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The rotation of the Sun modulates solar emission with 27-day variations. Large-scale structures in the solar atmosphere, like sunspots and plages, rotate with the Sun and emit at extreme ultraviolet (EUV) and microwaves that produce the varying part of the emission. As EUV emission is the main driver of ionization in the Earth ionosphere, its variations are reflected in the electron content. In this paper, we analyze wide range of data from radio emission in 245–17000 MHz range and the entire EUV spectrum to total and global electron contents (TEC and GEC, respectively) in the ionosphere to find out where the 27-day variations are most prominent. We show that the relative contribution of 27-day variations to radio emission is maximal at 1000 MHz and decreases at 245 and 17000 MHz. The variations are pronounced throughout the EUV spectrum, their intensity vary at different spectral lines and, on average, is higher than in radio emission. The distribution of the variations in global ionospheric maps (GIM) shows an intensification of 27-day variations in TEC in the North America region, which can be related to the winter anomaly as it is also more significant in this region. Temporal variations of the 27-day component of emission are similar in shape for radio and EUV emission, as well as for GEC, and have a high correlation, up to 0.8. Cycle-averaged temporal variations imply that the 27-day component weakens significantly during solar minimum but can intensify during the remaining phases of the solar cycle. We also find that the flux at 1000 MHz, which originate from free-free emission in contrast to F10.7, can be used as a proxy index of solar activity because it has the highest intensity of 27-day variations and has been observed since 1956. [ABSTRACT FROM AUTHOR]

Solar energetic particles (SEPs) affect space weather in both the heliosphere and on Earth. The present study investigates the occurrences of large SEP events focusing on their influence on the Earth, as well as their correlation with solar radio bursts (SRBs). The velocity dispersion analysis (VDA) is used to calculate the release times of large SEP events from their launch locations, as well as their apparent path length that connects them to interplanetary magnetic fields lines. According to the study, 122 large SEP events impacted the planet Earth from 1997 to 2024. The comparison of occurrence rates with previous solar cycles (SCs) suggests that SC 25 will peak with greater solar activity than the cycle 24 in terms of large SEP occurrences since large SEP events correlate well with the pattern of the sunspot cycle progression. In general, a few (35 out of 122) large SEP events are typically released from the Sun at times that coincide with the peak of associated solar flares and the onsets of corresponding SRBs indicating no delay while the rest have delayed in the release. The projected apparent lengths (L) range from 1.0 to 3.0 AU, with L exceeding 1.5 AU due to particle scattering and launch site pitch angles. The majority (115/122) of SEP occurrences are accelerated by shock waves from solar flares, CMEs, and fast plasma flow in the magnetic reconnection regions. Relevant SRBs for space weather study as they precede large SEP events diagnose the properties of particle populations propelled by solar flares and CMEs. This study finds that 90% of the large SEP events are preceded by solar radio emissions of type II, III and IV; and WAVES/STEREO revealed ∼ 76 % of SRBs have continuation in IP medium indicating the dynamics of associated shocks and electron beams traveling along open and quasi-open magnetic field lines. Thus, SRB monitoring continues to be a valuable tool for studying space weather and understanding physical phenomena in the solar corona and IP medium, such as particle populations that cause large SEP occurrences. [ABSTRACT FROM AUTHOR]

Herein, the energy performance of photovoltaic noise barriers (PVNBs) with cassette and shingles built‐on designs is evaluated using imec's energy yield framework. The simulation is validated through on‐site electrical and thermal measurements, and then the same design is employed for a case study near E19 road in Belgium using different scenarios. To optimize the energy yield, variations in the noise barrier height, orientation, and PV module tilt are introduced. The energy yield is then simulated to identify the optimal combination of parameters to maximize energy production. The results show that the cassette built‐on PVNB with fixed cassette distance provides higher energy yield throughout the year compared to other scenarios, and a low‐rise noise barrier is more energy‐efficient due to reduced shading effects. Sound pressure simulation conducted in COMSOL reveals that the cassette built‐on and shingles built‐on have comparable performance in sound reduction, and high‐rise noise barriers with small tilts (20°–40°) are optimal for sound pressure attenuation. [ABSTRACT FROM AUTHOR]

The document "Solar Radio Emissions" discusses the wide frequency range of radio emissions from the Sun, originating from different layers of the solar atmosphere and produced by various physical processes. It highlights the importance of solar radio observations in diagnosing magnetic fields, detecting energetic particle acceleration, and predicting space weather events. The document also introduces recent advancements in solar radio telescopes and presents research papers on topics such as solar radio bursts, quasi-periodic pulsations, and the classification of solar radio spectra. Additionally, it explores the potential of using radio detectors to search for ultralight dark matter conversions in the solar corona and solar wind plasmas. [Extracted from the article]

In the case of a weak signal from a photon counting lidar and strong noise from the solar background, the signal is completely submerged by noise, potentially resulting in the appearance of multiple peaks in the denoising algorithm of photon counting entropy. Consequently, a clear distinction between the signal and noise may become challenging, leading to significant fluctuation in the ranging error. To solve this problem, this paper proposes an improved offset parameter optimization algorithm under the framework of photon counting entropy, aiming to effectively eliminate peak interference caused by noise and enhancing ranging accuracy. The algorithm includes two aspects. First, we introduce the solar irradiance prediction of an MLP network and least squares linear conversion to accurately estimate the noise rate of the solar background noise. Then, we propose the offset parameter optimization method to effectively mitigate the interference caused by noise. In simulation and experimental analyses, the ranging error of our proposed method is within 5 and 30 cm , respectively. Compared with the denoising method of photon counting entropy, the average ranging error is increased by 81.99% and 73.76%. Furthermore, compared to other anti-noise methods, it exhibits superior ranging capability. [ABSTRACT FROM AUTHOR]

Solar energy utilization in the transportation sector is important for reducing fossil fuel consumption and achieving the grant goal of carbon neutrality. The photovoltaic noise barriers (PVNB) are recognized as a potential alternative for electric vehicle charging. This study aims to evaluate the power generation capabilities of both monofacial photovoltaic noise barriers (mono‐PVNB) and bifacial photovoltaic noise barriers (bi‐PVNB) when applied along roads with different directions and shading conditions. Results show that the daily yields of bi‐PVNB facing west, southwest, south, and southeast are 754, 819, 1101, and 894 Wh, respectively. In contrast, the daily yields of mono‐PVNB are 459, 711, 968, and 764 Wh. The bifacial gains are, respectively, 64, 15, 14, and 17%. The influence of partial shading on PV power generation is tested, and sharp decrease is observed when horizontal shading reaches 20% and vertical shading reaches 40%. In summary, the bi‐PVNB shows satisfactory power generation ability with different orientation and shading conditions. Under Shenzhen climate, the annual power generation of bi‐PVNB along east–west, north–south, southeast–northwest, and southwest–northeast direction roads are predicted to be 304, 325, 342, and 335 MWh per kilometer. [ABSTRACT FROM AUTHOR]

We investigate the temporal correlation between very-high-frequency (VHF, at frequencies of the order of 10–100 MHz), ultrahigh-frequency (UHF, at frequencies within 1–6 GHz), and x-ray (with photon energies more than 10 keV) emissions, which accompany the development of a high-voltage discharge initiated in a long gap at voltages up to 1 MV. The x-ray and UHF emissions are found to emerge starting approximately from the prepulse current onset observed before the discharge gap breakdown and both gradually decay coming to this instant. The UHF emission spectrum is represented with frequencies up to 6 GHz, with the highest spectral power being achieved within 1–2 GHz. The radio emission power drops sharply at frequencies below 1 GHz and increases closer to 150 MHz with the highest spectral power of VHF radiation being reached within 60–90 MHz. The VHF emission can appear before the discharge current and UHF emission onsets in the form of 100-ns-long prepulses, and its intensity significantly increases as the UHF emission starts. The analysis of the temporal correlation between x rays, VHF, and UHF radiations, discharge current, and voltage waveforms indicates that the generation mechanisms of the discharge electromagnetic radiations are difficult to be interpreted in terms of the developing or colliding streamer concepts. [ABSTRACT FROM AUTHOR]

We analysed a GOES C6.2 class solar flare that occurred on 27 October 2003 at the heliographic position S20E29. Utilising a database developed from a simplified 3D magnetic loop model, we inferred a set of geometric and physical parameters to characterise the flare. This model, based on general properties of known solar flares and adjusted for instrument resolution, was used to replicate observations from the Nobeyama Radio Polarimeter (NoRP) spectra and the Nobeyama Radioheliograph (NoRH) brightness maps. We identified a possible range of parameters by comparing observed spectra and brightness distribution maps with modelled counterparts. The analysis involved computing a weighted mean of the one hundred best-fit model parameters, ranked by increasing χ 2 values.Across six discrete time intervals representing the gradual, impulsive, and decay phases of the flare, we observed slight variations in values for ten analysed parameters, with notable exceptions at the burst maxima, including an energy spectral index of approximately ∼ 2.34 , a photospheric magnetic field strength of around ∼ 2 308 G , and a non-thermal electron density of about ∼ 10 7.11 cm - 3 . In general, our results replicated the soft-hard-soft behaviour in the gradual-peak-decay phases of a solar flare. Therefore, we infer that the physical parameters (magnetic field strength, energy spectral index, and non-thermal electron density) were accurately recovered. However, fitting geometric parameters such as inclination, asymmetry, azimuth, loop radius, loop height, and footpoint separation proved challenging due to the limited resolution of the instruments, which affects the precise determination of loop-like flare geometries. [ABSTRACT FROM AUTHOR]

The research involves examining the influence of partial solar eclipse on the strength of neutral hydrogen from the Sun. Baghdad University Radio Telescope (BURT) was used to monitor the partial solar eclipse on the 25th of October, 2022. Radio observations from the Sun were recorded from 11:30 AM to 03:36 PM. This means that the HI emission from the Sun was recorded before, during and after the event. It was noticed, that at the moment of maximum eclipse, ~ 46% of the Sun’s disk was covered by the Moon. For the purpose of this research, the solar radio wave intensity was monitored and the solar flux density was determined at different times, i.e. before, during and after the partial solar eclipse. The obtained results showed that both of the solar flux and power spectrum decrease with the progress of the eclipse until the moment of maximum eclipse, i.e. the moment at which the minimum values of solar flux density and antenna temperature were recorded (7 × 104 Jy and ~ 80 K). Then, at the last moments of the partial eclipse, it was noticed that both parameters started to increase again due to the decrease in the area of the Sun’s disk until both reached their normal values. In Conclusion, the partial solar eclipse affects the strength of neutral hydrogen from the Sun because the Moon blocks the neutral hydrogen from the Sun during the solar eclipse. [ABSTRACT FROM AUTHOR]

Solar images are critically important for studying solar activities and features. Today, many observatories rely on CMOS sensors to acquire these images. However, these sensors often introduce column fixed-pattern noise (CFPN), seriously affecting image quality. Therefore, we proposed a two-way filtering algorithm to remove CFPN. Firstly, in the horizontal direction, we used the one-dimensional global weighted least squares filter and the efficient bilateral filter to obtain a coarse denoised image. Then, we utilized the weighted guided filter in the vertical direction to estimate the CFPN components, thereby obtaining a clean solar image. We selected three different solar observation images to compare and evaluate our results to those obtained by three comparative methods. The images are observed by the Solar Upper Transition Region Imager aboard the SATech-01 satellite. Additionally, we further used two quantitative metrics, photo response non-uniformity and mean relative deviation, to quantify the denoised results. The results demonstrate that our proposed method removes the CFPN better and preserves the image features in a more balanced way. [ABSTRACT FROM AUTHOR]

Underwater optical wireless communication (UOWC) is a field of research that has gained popularity with the development of unmanned underwater vehicle (UUV) technologies. Its utilization is crucial in offshore industries engaging in sustainable alternatives for food production and energy security. Although UOWC can meet the high data rate and low latency requirements of underwater video transmission for UUV operations, the links that enable such communication are affected by the inhomogeneous light attenuation and the presence of sunlight. Here, we present how the underwater spectral distribution of the light field can be modeled along the depths of eight stratified oceanic water types. We considered other established models, such as SPCTRL2, Haltrin's single parameter model for inherent optical properties, and a model for the estimation of the depth distribution of chlorophyll-a, and present insights based on transmission wavelength for the maximum signal-to-noise ratio (SNR) under different optical link parameter combinations such as beam divergence and transmit power under "daytime" and "nighttime" conditions. The results seem to challenge the common notion that the blue-green spectrum is the most suitable for underwater optical communication. We highlight a unique relationship between the transmission wavelength for the optimal SNR and the link parameters and distance, which varies with depth depending on the type of oceanic water stratification. Our analyses further highlighted potential implications for solar discriminatory approaches and strategies for routing in cooperative optical wireless networks in the photic region. [ABSTRACT FROM AUTHOR]

Context. The slowly positively drifting bursts (SPDBs) are rarely observed in radio emission of solar flares. Aims. To understand how the SPDBs are generated, we studied the radio observations at 600–5000 MHz together with the imaging observations made in ultraviolet (UV) and extreme ultraviolet (EUV) during the SPDB-rich C8.7 flare of 2014 May 10 (SOL2014-05-10T0702). Methods. Because the SPDBs propagate towards locations of higher plasma density, we studied their associations with individual flare kernels, located either within the flare core itself, or distributed at longer distances, but connected to the flaring region by large-scale hot loops. For each kernel we constructed light curves using 1600 Å and 304 Å observations and compared these light curves with the temporal evolution of radio flux at 1190 MHz, representing all observed groups of SPDBs. We also analysed the UV/EUV observations to understand the evolution of magnetic connectivity during the flare. Results. The flare starts with a growing hot sigmoid observed in 131 Å. As the sigmoid evolves, it extends to and interacts with a half dome present within the active region. The evolving sigmoid reconnects at the respective hyperbolic flux tube, producing large-scale magnetic connections and an EUV swirl. Three groups of SPDBs are observed during this large-scale magnetic reconnection, along with a group of narrow-band type III bursts. The light curves of a kernel corresponding to the footpoint of spine line analogue show good agreement with the radio flux at 1190 MHz, indicating that the SPDBs are produced by the large-scale magnetic reconnection at the half dome. In addition, one of the kernels appeared in the neighbouring active region and also showed a similar evolution to the radio flux, implying that beams of accelerated particles can synchronize radio and UV/EUV light curves across relatively large distances. [ABSTRACT FROM AUTHOR]

Context. Shock waves in the solar corona are associated with solar flares and coronal mass ejections (CMEs). Type II solar bursts are radio signatures of shock waves in the solar corona. They are driven by solar flares or CMEs. Despite extensive studies, the intricate spectral patterns observed in type II solar bursts occasionally pose new challenges for the theory of electron acceleration in shocks. Aims. We study a newly identified feature in type II solar bursts called spectral cleaving. This feature is characterized by the actual branching of a type II radio emission lane in radio spectral data. Methods. We analyzed the type II burst exhibiting spectral cleaving in high-fidelity dynamic spectra obtained using the URAN-2 radio telescope (8.25–33 MHz; Poltava region, Ukraine) on 2011 February 14. The high-resolution spectrograms were examined to ascertain its spectral morphology. Results. Our research represents the first recognition of spectral cleaving as a peculiarity of type II bursts that is yet to be classified. This effect occurs due to the shift (or migration) of radio source(s) along a shock front, which in turn is caused by changes in the magnetic field orientation ahead of the propagating shock front. Conclusions. The spectral cleaving observed in solar type II bursts reveals a distinct phenomenon that indicates complex interactions between shock waves and magnetic fields in the solar corona. This discovery enhances our understanding of the mechanisms behind solar radio emissions and emphasizes the need for further observational studies to verify these findings. [ABSTRACT FROM AUTHOR]

We analyzed 58 high-energy proton events that occurred during the years 1996 – 2022. In 32 out of the 58 (55%) events, the proton energies extended up to ∼ 68 MeV but did not reach 100 MeV. In the remaining 26 events, the proton energies exceeded 100 MeV. We studied the differences in the characteristics of these proton events and their associations with solar and interplanetary phenomena to improve understanding proton sources and acceleration processes. The coronal mass ejections (CMEs) associated with > 100 MeV proton events appeared to be, on average, more energetic than those associated with < 100 MeV proton events. The peak and integrated fluxes (fluence) of the soft X-ray (SXR) flares were higher in > 100 MeV proton events, but there was almost no difference in the rise times of the flares. In a major part of the > 100 MeV proton events, protons were released over the rise phase of the SXR flares, whereas in most of the < 100 MeV events the proton releases occurred after the peak of the SXR flares. We established limits for the CME speed VCME and SXR peak flux Fpk or total fluence Fi, which helped us to distinguish the events in the two groups. Solar eruptions with VCME > 1000 km s−1 and F > pk 5 ⋅ 10 − 5 W m−2 had a high probability to produce proton events of > 100 MeV. On the other hand, eruptions with V > CME 900 km s−1 and F < i 5 ⋅ 10 − 4 J m−2 and eruptions with V < CME 900 km s−1 irrespective of the SXR total fluence were very likely to produce proton events of < 100 MeV. All proton events were associated with decametric Type III radio bursts, and most of them had Type II bursts associations either in metric or decametric–hectometric (DH) wavelengths or both. Both metric- and DH-Type II emissions were observed in 50% of < 100 MeV proton events while they were observed in 88% of > 100 MeV events. Our analysis showed that protons in most of the > 100 MeV events were released low in the corona (≤ 3.0 R⊙) before the onsets of the DH-Type II radio bursts. Conversely, protons in most of the < 100 MeV events were released higher in the corona (> 3 R⊙) and after the DH-Type II onsets. We conclude that protons in most of the > 100 MeV events are accelerated either by the flare reconnection processes or by shocks low in the corona and could undergo reacceleration higher in the corona in CME shocks manifested in DH-Type II radio emission. In the < 100 MeV events, protons are mainly accelerated in CME shocks at coronal heights > 3 R⊙. [ABSTRACT FROM AUTHOR]

The intelligent transportation systems (ITS) using radio frequency (RF) face challenges like interference and limited bandwidth compared to visible light communication (VLC). Integrating vehicular VLC (V-VLC) utilizing the existing light-emitting diodes (LEDs) in automobiles could provide a complementary approach to mitigate RF constraints. Performance degradation by background noise from sunlight can undermine signal quality. So, improving performance and managing interference are the keys to better V-VLC operation. This work proposes a solar noise suppression method for a V-VLC system, leveraging Allan variance and an extended Kalman filter (EKF). Based on the obtained Allan variance, updates are made to the observation model, state vector, and observation noise covariance matrix to achieve superior performance. Minimum mean square error (MMSE) equalization is used. The proposed filter efficiently minimizes the notable autocorrelation triggered by the solar noise, resulting in a bit error rate (BER) reduction of approximately 88% compared to the system without the adaptive filter. This increased convergence highlights the possibility of higher communication performance and reliability. Hence, this work provides a novel adaptive EKF design and offers valuable perspectives on the importance of Allan variance in enhancing the V-VLC system. [ABSTRACT FROM AUTHOR]

Solar type III radio bursts are crucial indicators of energetic electron activity in the solar corona and interplanetary space. Our assessment of 43 interplanetary type III bursts, recorded by the FIELDS instrument on board the Parker Solar Probe during Encounters 05 to 11, has led to significant and complex findings. We have analyzed time profile features across a frequency range of 19–0.5 MHz, revealing dependencies on frequency and providing insights into duration, burst speeds, bandwidths, and drift rates. This novel analysis has unveiled a spectral index of −0.63 ± 0.04 for rise, −0.69 ± 0.03 for decay time, and −0.68 ± 0.03 for the total duration. We have determined the average electron beam velocities for front, middle, and back as 0.15 c, 0.13 c, and 0.08 c, respectively. Our findings show that faster electron beams generate emissions with shorter duration. The average ratio of the front-to-back velocity is 1.87, and the ratio of front-to-middle velocity is 1.23. We have also discovered a strong relationship between burst duration with rise, peak, and decay times, particularly pronounced with decay time (correlation coefficient = 0.95). This indicates that the entire temporal profile, including rise, peak, and decay phases, collectively contributes to event duration and is not solely influenced by external factors like plasma conditions or electron beam dynamics but also by internal burst processes. These complex findings shed light on the physical mechanisms governing burst dynamics, revealing intricate interactions between electron beam characteristics and observed temporal and spectral traits of type III solar radio bursts. [ABSTRACT FROM AUTHOR]

The underwater environment used for communication is harsh and complex, necessitating heightened standards for spectral efficiency and reliability in underwater wireless optical communication (UWOC) systems. The focus of this work is on the performance of multi-user UWOC systems operating in oblique channels of ocean turbulence downlink, where users are randomly distributed at a certain depth. A joint optimization scheme is proposed, which joints rate-splitting multiple access (RSMA) and power allocation so that the system's ergodic sum capacity is optimized to improve the transmission bandwidth. Furthermore, the probability density function (PDF) and cumulative distribution function (CDF) models for the received signal-to-noise ratio (SNR) of a multi-user multiple-input multiple-output (MIMO) system operating in the turbulent underwater oblique channels are established, accounting for the avalanche photodiode (APD) shot noise and solar radiation noise. Theoretical derivations are presented to quantify the ergodic capacity and outage probability of the multi-user system utilizing the RSMA technology. Subsequently, a numerical analysis is conducted to investigate the influence of the power allocation coefficient, RSMA, and the joint optimization algorithm on the performance of a two-user MIMO system leveraging RSMA. The simulation results show that our optimization scheme effectively reduces the outage probability, thereby achieving the maximum system sum rate and validating the practical feasibility and efficacy of the proposed scheme. [ABSTRACT FROM AUTHOR]

We introduce a new multivariate data set that utilizes multiple spacecraft collecting in‐situ and remote sensing heliospheric measurements shown to be linked to physical processes responsible for generating solar energetic particles (SEPs). Using the Geostationary Operational Environmental Satellites (GOES) flare event list from Solar Cycle (SC) 23 and part of SC 24 (1998–2013), we identify 252 solar events (>C‐class flares) that produce SEPs and 17,542 events that do not. For each identified event, we acquire the local plasma properties at 1 au, such as energetic proton and electron data, upstream solar wind conditions, and the interplanetary magnetic field vector quantities using various instruments onboard GOES and the Advanced Composition Explorer spacecraft. We also collect remote sensing data from instruments onboard the Solar Dynamic Observatory, Solar and Heliospheric Observatory, and the Wind solar radio instrument WAVES. The data set is designed to allow for variations of the inputs and feature sets for machine learning (ML) in heliophysics and has a specific purpose for forecasting the occurrence of SEP events and their subsequent properties. This paper describes a data set created from multiple publicly available observation sources that is validated, cleaned, and carefully curated for our ML pipeline. The data set has been used to drive the newly‐developed Multivariate Ensemble of Models for Probabilistic Forecast of SEPs (MEMPSEP; see MEMPSEP‐I (Chatterjee et al., 2024, https://doi.org/10.1029/2023SW003568) and MEMPSEP‐II (Dayeh et al., 2024, https://doi.org/10.1029/2023SW003697) for accompanying papers). Plain Language Summary: We present a new data set that uses observations from multiple spacecraft observing the Sun and the interplanetary space around it. This data is connected to the processes that create solar energetic particles (SEPs). SEP events pose threats to both astronauts and assets in space. The data set contains 252 solar flare events that caused SEPs and 17,542 that do not. For each event, we gather information about the local space environment around the sun, such as energetic protons and electrons, the conditions of the solar wind, the magnetic field, and remote solar imaging data. We use instruments from NOAA's Geostationary Operational Environmental Satellites (GOES) and the Advanced Composition Explorer spacecraft, as well as data from the Solar Dynamic Observatory, the Solar and Heliospheric Observatory, and the Wind solar radio instrument WAVES. This data set is designed to be used in machine learning (ML), with a focus on predicting the occurrence and properties of SEP events. We detail each observation obtained from publicly available sources, and the data treatment processes used to validate the reliability and usefulness for ML applications. Key Points: Machine learning oriented data set for predicting the occurance and properties of solar energetic particle eventsMultivariate remote sensing and in‐situ observationsContinuous data set spanning several decades [ABSTRACT FROM AUTHOR]

To fully exploit the multi-epoch data processing in GNSS parameter estimation, a thorough understanding of the parameters’ temporal behavior is required. This behavior is expressed by a dynamic model whose uncertainty is captured by the parameters’ process noises. The more randomly the temporal behavior deviates from the dynamic model, the larger the process noise variance should be considered. In GNSS positioning, the ionospheric parameters are known to be time-varying, requiring a reliable choice of process noise. In this contribution, we present a data-driven method with which one can estimate ionospheric process noise variances, minimizing the risk of having a suboptimal estimation process. We study the dependency of such process noise variance on solar and geomagnetic activities across various geographic positions. By analyzing several globally distributed datasets, a considerable difference in the ionospheric process noise estimates is observed between daytime and nighttime, emphasizing the importance of modeling ionospheric temporal characteristic in GNSS positioning. [ABSTRACT FROM AUTHOR]

We report for the first time the detection of thermal free–free emission from post-flare loops at 34 GHz in images from the Nobeyama Radioheliograph. We studied eight loops, seven of which were from regions with an extremely strong coronal magnetic field reported by Fedenev et al. Loop emission was observed in a wide range of wavelength bands, up to soft X-rays, confirming their multitemperature structure and was associated with noise storm emission in metric λ. The comparison of the 17 GHz emission with that at 34 GHz, after a calibration correction of the latter, showed that the emission was optically thin at both frequencies. We describe the structure and evolution of the loops and we computed their density, obtaining values for the top of the loops between 1 and 6 × 1010 cm−3, noticeably varying from one loop to another and in the course of the evolution of the same loop system; these values have only a weak dependence on the assumed temperature, 2 × 106 K in our case, as we are in the optically thin regime. Our density values are above those reported from EUV observations, which go up to about 1010 cm−3. This difference could be due to the fact that different emitting regions are sampled in the two domains and/or due to the more accurate diagnostics in the radio range, which do not suffer from inherent uncertainties arising from abundances and non-LTE excitation/ionization equilibria. We also estimated the magnetic field in the loop tops to be in the range of 10–30 G. [ABSTRACT FROM AUTHOR]

Massive stars that travel at supersonic speeds can create bow shocks as their stellar winds interact with the surrounding interstellar medium (ISM). These bow shocks – prominent sites for mechanical feedback of individual massive stars – are predominantly observed in the infrared (IR) band. Confirmed high-energy emission from stellar bow shocks has remained elusive and confirmed radio counterparts, while rising in recent years, remain rare. Here, we present an in-depth multiwavelength exploration of the bow shock driven by LS 2355, focusing on its non-thermal properties. Using the most recent Fermi source catalogue, we rule out its previously proposed association with an unidentified γ-ray source. Furthermore, we use deep Australian Square Kilometre Array Pathfinder (ASKAP) observations from the Rapid ASKAP Continuum Survey and the Evolutionary Map of the Universe survey to identify a non-thermal radio counterpart: the third spectrally confirmed non-thermal bow shock counterpart after BD+43°3654 and BD+60°2522. We finally use Wide-field Infrared Survey Explorer (WISE) IR data and Gaia to study the surrounding ISM and update the motion of LS 2355. Specifically, we derive a substantially reduced stellar velocity, |$v_* = 7.0\pm 2.5$| km s−1, compared to previous estimates. The observed non-thermal properties of the bow shock can be explained by an interaction between the wind of LS 2355 and a dense H  ii region, at a magnetic field close to the maximum magnetic field strength allowed by the compressibility of the ISM. Similar to earlier works, we find that the thermal radio emission of the shocked ISM is likely to be substantially suppressed for it to be consistent with the observed radio spectrum. [ABSTRACT FROM AUTHOR]

Ultra-high-energy cosmic rays (UHECRs) are extremely rare energetic particles of ordinary matter in the Universe, traveling astronomical distances before reaching the Earth's atmosphere. When primary cosmic rays interact with atmospheric nuclei, cascading extensive air showers (EASs) of secondary elementary particles are developed. Radio detectors have proven to be a reliable method for reconstructing the properties of EASs, such as the shower's axis, its energy, and its maximum ( X max ). This aids in understanding fundamental astrophysical phenomena, like active galactic nuclei and gamma-ray bursts. Concurrently, data science has become indispensable in UHECR research. By applying statistical, computational, and deep learning methods to both real-world and simulated radio data, researchers can extract insights and make predictions. We introduce a convolutional neural network (CNN) architecture designed to classify simulated air shower events as either being generated by protons or by iron nuclei. The classification achieved a stable test error of 10%, with Accuracy and F 1 scores of 0.9 and an MCC of 0.8. These metrics indicate strong prediction capability for UHECR's nuclear composition, based on data that can be gathered by detectors at the world's largest cosmic rays experiment on Earth, the Pierre Auger Observatory, which includes radio antennas, water Cherenkov detectors, and fluorescence telescopes. [ABSTRACT FROM AUTHOR]

Transport of energetic electrons in the flare loop is important to understanding nonthermal emissions in solar flares. In this work, we model the propagation of electrons by numerically solving the particle transport equation which includes the physics of magnetic mirroring and turbulent pitch-angle diffusion. We find that both the fractions of electrons trapped in the looptop and precipitating into the solar surface display a non-monotonic behavior with increasing scattering rate. In the moderate diffusion regime, the precipitation fraction is highest and we expect intense nonthermal HXR and microwave emissions at the footpoints. With no or weak pitch-angle scattering, the velocity space distribution can be highly anisotropic both in the looptop and loopleg regions. Different patterns of stripes with positive gradients in the perpendicular direction can drive the electron cyclotron maser instability with higher efficiency than the classical loss-cone distribution, facilitating the excitation of coherent solar radio bursts. Our simulation results highlight the effects of turbulent pitch-angle scattering on electron trap/precipitation and anisotropic distribution in solar flares, which may help us understand the precipitation of magnetospheric electrons accounting for the aurora as well.

There are several methods for indirectly detecting exoplanets, such as transit, radial velocity, astrometry, and the conventional gravitational microlensing approach. These methods rely on observing the effects of exoplanets on the emission or motion of observed stars. All these techniques have focused on the optical or infrared domains. However, an alternative method for exoplanet detection via microlensing events involves planets orbiting the source star, creating a binary source system. In this study, we explore a novel approach to detecting and studying exoplanets exclusively through their radio emissions resulting from magnetospheric processes. We propose utilizing the Roman telescope as a survey observer to detect microlensing events. Subsequently, we investigate the potential for detecting planetary radio signals through followup observations of these microlensing events in the radio band using the SKA telescope. This method is viable due to the comparable radio emission levels of exoplanets and their parent stars, unlike optical and infrared emissions. We conduct a Monte Carlo simulation to replicate the observations by the Nancy Roman Telescope, followed by a follow-up observation in radio frequencies using the SKA telescope. We determine that approximately 1,317 exoplanets exhibit detectable signals by the SKA telescope during the 7-season observations by the Nancy Roman Telescope. This result indicates that such a method cannot only facilitate the direct detection of exoplanets but also enable the measurement of their magnetic field strength through analysis of their radio emissions. [ABSTRACT FROM AUTHOR]

The accelerated electrons during solar flares produce radio bursts and nonthermal X-ray signatures. The quasi-periodic pulsations (QPPs) and fine structures in spatial–spectral–temporal space in radio bursts depend on the emission mechanism and the local conditions, such as magnetic fields, electron density, and pitch-angle distribution. Radio burst observations with high-frequency time resolution imaging provide excellent diagnostics. In converging magnetic field geometries, the radio bursts can be produced via the electron cyclotron maser (ECM). Recently, using observations made by the Karl G. Jansky Very Large Array (VLA) at 1–2 GHz, Yu et al. reported a discovery of long-lasting auroral-like radio bursts persistent over a sunspot and interpreted them as ECM-generated emission. Here we investigate the detailed second and subsecond temporal variability of this continuous ECM source. We study the association of 5 s period QPPs with a concurrent GOES C1.5-class flare, utilizing VLA's imaging spectroscopy capability with an extremely high temporal resolution (50 ms). We use the density and magnetic field extrapolation model to constrain the ECM emission to the second harmonic O -mode. Using the delay of QPPs from X-ray emission times, combined with X-ray spectroscopy and magnetic extrapolation, we constrain the energies and pitch angles of the ECM-emitting electrons to ≈4–8 keV and >26°. Our analysis shows that the loss-cone diffusion continuously fuels the ECM via Coulomb collisions and magnetic turbulence between a length scale of 5 and 100 Mm. We conclude that the QPP occurs via the Lotka–Volterra system, where the electrons from solar flares saturate the continuously operating ECM and cause temporary oscillations. [ABSTRACT FROM AUTHOR]

In order to deal with the difficulty of spectrum sensing in cognitive satellite wireless networks, a large-scale cognitive network spectrum sensing algorithm based on big data analysis theory is studied, and a new algorithm using mean exponential eigenvalue is proposed. This new approach fully uses all the eigenvalues in sample covariance matrix of the sensing results to make the decision, which can effectively improve the detection performance without obtaining the prior information from licensed users. Through simulation, the performance of various large scale cognitive radio spectrum sensing algorithms based on big data analysis theory is compared, and the influence of satellite to ground channel conditions and the number of sensing nodes on the performance of the algorithm is discussed. [ABSTRACT FROM AUTHOR]

The Laser Interferometer Space Antenna (LISA) of the European Space Agency will be the first interferometer for low-frequency ( 10 - 4 – 10 - 1 Hz) gravitational wave detection in space. LISA will detect spurious accelerations of the test masses, the end mirrors of the interferometer, of the order of femto-g. Amongst spurious signals, Coulomb forces due to stray electric fields coupling with charge deposited on the test masses by galactic and solar particles and the noise associated to the charging process must be monitored during the mission lifetime. Precious clues on spurious forces acting on the test masses have been studied with the LISA Pathfinder mission, meant for the testing of the instrumentation that will be placed on board LISA, in 2016–2017. In this work we present the design and implementation of a workflow leading to equation discovery for the relationship between solar wind speed, galactic cosmic-ray variations and interplanetary magnetic field intensity observations for the diagnostics of LISA. The workflow exploits explainable artificial intelligence tools to build a bridge between the opaque predictions obtained with machine learning (ML) models and data analysis performed by humans with space mission observations. The core step of the workflow is the implementation, tuning and optimisation of an opaque ML regressor explicitly designed for the future LISA mission, based on input observations of the galactic cosmic-ray flux and of the interplanetary magnetic field intensity. The regressor is aimed at reconstructing the solar wind speed, a parameter of fundamental importance, but not available, for the mission environment monitoring. The workflow ends with the application of explainable clustering techniques to the opaque model in order to (i) obtain human-interpretable outputs instead of opaque ones without any noticeable loss in the predictive performance and (ii) discover an equation describing the quantitative relationship between the involved variables, currently missing in the literature. The correlation amongst the transit of interplanetary structures, galactic cosmic-ray variations and LISA test-mass charging is illustrated here. [ABSTRACT FROM AUTHOR]

This paper investigates the incidence of coherent emission in solar radio bursts, using a revised catalog of 3800 solar radio bursts observed by the Nobeyama Radio Polarimeters from 1988 to 2023. We focus on the 1.0 and 2.0 GHz data, where radio fluxes of order 1010 Jy have been observed. Previous work has suggested that these bursts are due to electron cyclotron maser (ECM) emission. In at least one well-studied case, the bright emission at 1 GHz consists of narrowband spikes of millisecond duration. Coherent emission at 1 GHz can be distinguished from traditional incoherent gyrosynchrotron flare emission based on the radio spectrum: Gyrosynchrotron emission at 1 GHz usually has a spectrum rising with frequency, so bursts in which 1 GHz is stronger than higher-frequency measurements are unlikely to be incoherent gyrosynchrotron. Based on this criterion, it is found that for bursts exceeding 100 sfu, three-quarters of all bursts at 1 GHz and half of all 2 GHz bursts have a dominant coherent emission component, assumed to be ECM. The majority of the very bright bursts at 1 GHz are highly circularly polarized, consistent with a coherent emission mechanism, but not always 100% polarized. The frequency range from 1 to 2 GHz is heavily utilized for terrestrial applications, and these results are relevant for understanding the extreme flux levels that may impact such applications. Further, they provide a reference for comparison with the study of ECM emission from other stars and potentially exoplanets. [ABSTRACT FROM AUTHOR]

The geo-effectiveness of coronal mass ejections (CMEs) is determined primarily by their magnetic fields. Modeling of gyrosynchrotron (GS) emission is a promising remote sensing technique to measure the CME magnetic field at coronal heights. However, faint GS emission from CME flux ropes is hard to detect in the presence of bright solar emission from the solar corona. With high dynamic-range spectropolarimetric meter wavelength solar images provided by the Murchison Widefield Array, we have detected faint GS emission from a CME out to ∼8.3 R ⊙, the largest heliocentric distance reported to date. High-fidelity polarimetric calibration also allowed us to robustly detect circularly polarized emission from GS emission. For the first time in the literature, Stokes V detection has jointly been used with Stokes I spectra to constrain GS models. One expects that the inclusion of polarimetric measurement will provide tighter constraints on the GS model parameters. Instead, we found that homogeneous GS models, which have been used in all prior works, are unable to model both the total intensity and circular polarized emission simultaneously. This strongly suggests the need for using inhomogeneous GS models to robustly estimate the CME magnetic field and plasma parameters. [ABSTRACT FROM AUTHOR]

Radio observations from normal pulsars indicate that the coherent radio emission is excited by curvature radiation from charge bunches. In this review, we provide a systematic description of the various observational constraints on the radio emission mechanism. We have discussed the presence of highly polarized time samples where the polarization position angle follow two orthogonal well-defined tracks across the profile that closely match the rotating vector model in an identical manner. The observations also show the presence of circular polarization, with both the right and left handed circular polarization seen across the profile. Other constraints on the emission mechanism are provided by the detailed measurements of the spectral index variation across the profile window, where the central part of the profile, corresponding to the core component, has a steeper spectrum than the surrounding cones. Finally, the detailed measurements of the subpulse drifting behaviour can be explained by considering the presence of non-dipolar field on the stellar surface and the formation of the partially screened gap (PSG) above the polar cap region. The PSG gives rise to a non-stationary plasma flow that has a multi-component nature, consisting of highly energetic primary particles, secondary pair plasma, and iron ions discharged from the surface, with large fragmentation resulting in dense plasma clouds and lower-density inter-cloud regions. The physical properties of the outflowing plasma and the observational constraints lead us to consider coherent curvature radiation as the most viable explanation for the emission mechanism in normal pulsars, where propagation effects due to adiabatic walking and refraction are largely inconsequential. [ABSTRACT FROM AUTHOR]

The remnant of the historical supernova 1181 is claimed to be associated with a white dwarf merger remnant J005311. The supernova remnant (SNR) shock, and a termination shock expected to be formed by the intense wind of J005311, are potential sites for radio emission via synchrotron emission from shock-accelerated electrons. In this paper, we estimate the radio emission from these two shocks, and find the peak radio flux to be 0.1–10 mJy (at 0.01–1 GHz) in the outer SNR shock and 0.01–0.1 mJy (at 1–10 GHz) in the inner termination shock. We also search for radio emission from this source in the archival data of the Karl G. Jansky Very Large Array (VLA) Sky Survey at 3 GHz, the NRAO VLA Sky Survey at 1.4 GHz and the Canadian Galactic Plane Survey at 408 MHz, finding no significant detection. While targeted observations with higher sensitivity are desired, we particularly encourage those at higher frequency and angular resolution to probe the inner termination shock and its evolution. [ABSTRACT FROM AUTHOR]

The present paper implements new approaches introduced in regard to pre-earthquake geo-chemical activity that results in lithosphere-atmosphere–ionosphere coupling (LAIC). Specifically, stratospheric temperature anomaly as a result of precursory atmospheric gravity wave (AGW) activity in the stratosphere is studied. A new technique is developed based on the parameters a) daily average temperature ( T mean ), b) daily maximum temperature ( T max ), c) T mean averaged over altitude, d) T max averaged over altitude. The new approach is applied to six earthquakes of Iran as well as Tohoku earthquake. Detected Anomalies are analyzed and discussed. Possible new variations such as stratospheric cooling as a result of active geomagnetic conditions are determined. Geographical maps and spatial distribution of temperature anomalies are presented to comprehend the possible source of variation. Moreover, space-based ULF emission observed by an in situ electric field detector (EFD) on board of China Seismic-Electromagnetic Satellite (CSES) is presented as associated with 3 earthquakes that occurred in 2019. Detailed analysis of satellite overpass proximity to the earthquake epicenter, earthquake magnitude, and dates are examined and ULF anomalies associated with 3 magnetic field components are discussed. Finally, a systematic approach to be implemented using the new techniques in real time is proposed. [ABSTRACT FROM AUTHOR]

At redshifts beyond z≳30 , the 21 cm line from neutral hydrogen is expected to be essentially the only viable probe of the three-dimensional matter distribution. The lunar far-side is an extremely appealing site for future radio arrays that target this signal, as it is protected from terrestrial radio frequency interference, and has no ionosphere to attenuate and absorb radio emission at low frequencies (tens of MHz and below). We forecast the sensitivity of low-frequency lunar radio arrays to the bispectrum of the 21 cm brightness temperature field, which can in turn be used to probe primordial non-Gaussianity generated by particular early universe models. We account for the loss of particular regions of Fourier space due to instrumental limitations and systematic effects, and predict the sensitivity of different representative array designs to local-type non-Gaussianity in the bispectrum, parametrized by fNL. Under the most optimistic assumption of sample variance-limited observations, we find that σ(fNL)≲0.01 could be achieved for several broad redshift bins at z≳30 if foregrounds can be removed effectively. These values degrade to between σ(fNL)∼0.03 and 0.7 for z=30 to z=170 , respectively, when a large foreground wedge region is excluded. This article is part of a discussion meeting issue 'Astronomy from the Moon: the next decades (part 2)'. [ABSTRACT FROM AUTHOR]

Aims. The X-ray luminous and radio-loud active galactic nucleus (AGN) SRGE J170245.3+130104 discovered at z ∼ 5.5 provides unique chances to probe the growth and evolution of a supermassice black hole (SMBH) with powerful jets in the early Universe. Methods. We present 1.35 − 5.1 GHz Very Long Baseline Array (VLBA) results regarding the radio continuum emission and a spectral analysis of this quasar in a low-flux-density state. Results. This source is unresolved at three frequencies, with total flux densities of 8.35 ± 0.09 Jy beam−1, 7.47 ± 0.08 Jy beam−1, and 6.57 ± 0.02 Jy beam−1 at 1.73 GHz, 2.26 GHz, and 4.87 GHz, respectively. Meanwhile, the brightness temperature is higher than 109 K. Conclusions. Compared with previous radio observations with arcsecond-scale resolution, nearly all the radio emission from this source is concentrated in the very central milliarcsecond (mas) scale area. We confirm this source is a bright blazar at z > 5. This young AGN provides a great opportunity to understand the mechanisms behind the generation of strong jets in the early Universe. [ABSTRACT FROM AUTHOR]

Large‐scale ionospheric gradients associated with the solar terminator can deflect high frequency (HF) radio waves to off‐great circle paths during the morning and evening, negatively impacting technologies reliant on HF radio wave propagation. For example, geolocation algorithms used by scientific and military over‐the‐horizon radars (OTHRs) generally assume on‐great circle propagation, and thus lateral deviations from the great‐circle path can lead to positioning errors. In this study, radio wave propagation is simulated via 3D numerical ray traces though an empirical, high‐latitude model ionosphere initialized for a variety of times of the day and year to explore and quantify high‐latitude off‐great circle propagation associated with the solar terminator. Analysis of these simulations show large scale east‐west ionospheric gradients due to the solar terminator can cause lateral deviations in north‐directed propagation paths exceeding 20° at sunrise and sunset depending on radio wave frequency, though the largest portion of received signal power tends to experience maximum deflections of 5°. An exploration of the dependence of propagation direction on deflection shows that propagation paths parallel to the solar terminator tend to experience the largest deflections. Since the solar terminator at high latitudes is at an angle with respect to north in the winter and summer, propagation paths oriented west or east of north can experience larger deflections than north oriented paths at sunrise and sunset during these times of year. Impacts of these diurnal deflections on the operation of OTHR and scientific radar are discussed, as well as possible strategies for mitigating them. Plain Language Summary: High frequency (HF) radio waves are able to travel long distances by bouncing between the ionosphere (an upper layer of the Earth's atmosphere) and the ground. HF radio waves transmitted north can have their paths deflected east or west by changes in the ionosphere that happen at sunrise and sunset. In this paper, simulations of radio waves are used to explore how large these deflections can be and how they change over the course of the day and year. It is found that north pointing radio signals at certain frequencies can be deflected by more than 20° at sunrise and sunset. These simulations are also used to explore how radio waves transmitted in different directions are deflected at sunrise and sunset. It is found that radio waves transmitted along the dividing line between day and night tend to experience the largest deflections. The Earth is tilted with respect to its rotation, meaning this dividing line is not always aligned with North. The deviation from north is largest in the winter and summer. This means that radio waves transmitted west or east of north at these times of year can experience larger deflections than northward transmissions. Key Points: The lateral deflection of high frequency radio waves caused by the solar terminator is investigated with ray tracing simulationsNorth‐south propagation paths can experience significant (>20°) deflections in the morning and eveningEast‐west paths can also see significant deflections at high latitudes, at times when the solar terminator is also oriented east‐west [ABSTRACT FROM AUTHOR]

The F10.7 index is crucial for assessing solar activity, significantly impacting communication, navigation, and satellite operations. The intrinsic complexity and variability of solar activity often result in sudden perturbations in the F10.7 index, compromising the accuracy and stability of forecasts. To address this challenge, we propose a novel prediction strategy that separately forecasts fundamental trends driven by the medium-to-long-term evolution of the solar cycle and the 27 day rotational modulation, along with transient disturbances caused by solar flares and the rapid evolution of active regions. These forecasts are then integrated to enhance overall prediction accuracy. We incorporate additional features such as the soft X-ray flare index (FI _SXR ), magnetic type of the active region (new_Mag), and X-ray background flux (XBF) to enhance the understanding of the underlying physical processes of solar activity. Our experiments, conducted using advanced forecasting models on the SG-F10.7-All data set, validate the efficacy of our proposed strategy. Notably, the iTransformer model demonstrates superior performance in both short-term and medium-term forecasting scenarios. The inclusion of FI _SXR , new_Mag, and XBF significantly improves forecasting accuracy, highlighting their importance in improving the F10.7 index predictions. Our method outperforms international models from the Space Weather Prediction Center, British Geological Survey, and Collecte Localisation Satellites, exhibiting greater accuracy and adaptability across various solar activity phases. This finding provides a novel approach for precise forecasting of the F10.7 index.

In this work the electric field of narrow bipolar events (NBEs) measured at a remote location is used to extract the current waveform of the source discharge. All calculations correspond to a vertical linear current source above a perfectly conducting ground plane. The current study uses the well established formulation of electromagnetic fields in the frequency domain, and develops a deconvolution based technique to obtain exact reconstruction of the source current, improving upon previous modeling of NBEs, which often require tuning several inter‐dependent parameters to determine the current that best reproduces the observed electric field. Our proposed solution, although readily available in standard electromagnetic textbooks, has never been employed in the context of lightning related discharges, and offers a simple and efficient alternative to previous conventional time domain calculations. Plain Language Summary: Narrow bipolar events (NBEs) are associated with highly impulsive sources of electromagnetic radiation in the Earth's natural environment that occur in association with initiation of lightning discharges or in isolation. The research community has accumulated significant amount of data on radio emissions associated with these sources. However, the interpretation of these events is currently conducted using source current fitting models that employ large numbers of fitting parameters that do not have physical grounding or clear relevance to these isolated sources. In this work we use standard frequency domain analysis of radiation from these sources that does not require any fitting parameters and allows direct reconstruction of source currents. The proposed approach assumes that the observed radiation is emitted due to polarization of a conducting region in externally applied electric field. The approach is grounded on previous first principles modeling of the polarization process, indicating that the polarization current should be maximum in the middle of conducting region and take zero values at the ends. This first order physics based interpretation of NBE sources does not require specification of the ionization mechanism creating the conducting region, but allows exact reconstruction of the current that radiates the observed wideband NBE waveforms. Key Points: The frequency domain analysis is applied for the first time to analysis of radiation from NBE source currentsThe proposed new approach is validated by detailed comparisons with previously published NBE studiesThe methodology is developed that allows exact reconstruction of source currents that radiate the observed wideband NBE waveforms [ABSTRACT FROM AUTHOR]

The solar type J radio burst is a variant of type III bursts, which are a probe for understanding solar energetic electrons and local electron density. This study investigates a type J burst event on 2017 September 9. We have combined the data from the extreme-ultraviolet (EUV) imaging and the EUV Imaging Spectrometer (EIS) to analyze the event. Within 4 minutes several type J bursts with similar morphology occur. Two of them, with clear fundamental and second harmonic bands, are studied in detail. We find a delay of 2 ± 0.5 s between their different harmonic bands. During type J bursts, only one coronal loop brightens significantly at its northern footpoint, in correlation with the continuous injection of erupting jets into the loop. The EUV intensity of the brightening footpoint is correlated with the radio flux at 245 and 410 MHz, with correlation coefficients of 0.2 and 0.4, respectively. These observations suggest that the type J bursts should originate from this coronal loop. By analyzing the electron number density distribution along the coronal loop diagnosed from the EIS data and the time evolution of the plasma frequency calculated from the type J burst, we determine that the velocities of the energetic electrons exciting the two type Js are 0.10 ± 0.02 c and 0.12 ± 0.02 c. Our results confirm previous studies on type J bursts. [ABSTRACT FROM AUTHOR]

The large‐scale deployment of photovoltaics (PVs) along highways has the potential for the generation of clean electricity without competing for land use or burdening the power grid since energy for electric vehicles (EVs) can be generated locally on wastelands along highways near service stations. An analysis was carried out to evaluate the feasibility of integrating vertical bifacial solar modules into noise barriers. The approach involved integrating geospatial data with PV potential data using geographic information systems (GIS) technology. The results show a potential of around 200 GWh/year if all current noise barriers along highways in the Netherlands are considered suitable for PV module integration. Three case studies have been analysed regarding specific service stations for specific road orientations. It is shown that solar energy can charge more than 300 vehicles per day by combining bifacial PV noise barriers and standard mono‐facial PV modules on publicly available land along the highway in all three case studies, which is sufficient to meet 80% of the expected EV charging demand along highways in 2030. Highlights: The PV potential of noise barriers in Dutch highways is 200 GWh/year.Three case studies including bifacial vertical PV noise barriers and standard tilted PV systems.PV‐powered service stations can charge about 300 EVs per day.Solar fraction of EV charging is higher than 80% for all case studies. [ABSTRACT FROM AUTHOR]

The results of the analysis of 205 brightest sources ( mJy), which were found in the sky survey at the declination of the pulsar in the Crab Nebula, are presented. The survey was conducted at a frequency of 4.7 GHz using a three-beam radiometer complex installed in the focus of the Western Sector of the RATAN-600 radio telescope in 2018–2019. Based on the measurements taken and the data collected in the CATS astrophysical catalogs database, the radio spectra of the objects were constructed. For a quarter of all detected sources, data at frequencies above 4 GHz were obtained for the first time, and for the rest they were supplemented. The variability of radiation sources on the scales of the year, from days to months, has been studied. The greatest change in the radio flux was found in the blazar B2 1324 22. The search for daily variability was carried out for 26 of the brightest sources with an average value of mJy. All sources are identified with objects from optical and infrared catalogs. The radio luminosity was calculated for 112 objects with known redshifts. [ABSTRACT FROM AUTHOR]

Based on the global empirical model of the median of the critical frequency of the F2 layer (SDMF2), the properties of diurnal variations in the annual asymmetry in the maximal concentration NmF2 of the F2 layer for different values of the solar activity index F are analyzed. The AI index characterizing the relative difference in NmF2 averaged over all latitudes and longitudes between January and July at a given local time is used as a parameter of this asymmetry. It is found that a semidiurnal mode prevails in the diurnal variations in the AI index with maxima at the daytime and nighttime hours. The daytime maximum of the AI index hardly depends at all on the solar activity level. The nighttime AI maximum decreases with an increase in solar activity. The daytime and nighttime maxima in AI almost coincide by the amplitude when AI = 16–17% for low solar activity. The difference in the solar radio emission flux between January and July due to the ellipticity of Earth's orbit relative to the Sun contributes substantially into the AI index at all hours of the day. On average, it is 3–4% and could reach 5% for low solar activity during the nighttime hours. The difference in the AI index for low and high solar activity according to the International Reference Ionosphere model IRI (with the URSI and even more with the CCIR coefficients) is overestimated with respect to the SDMF2 model at almost all hours of the day, apparently due to limited amount of the experimental data used to obtain the CCIR and URSI coefficients, especially over oceans. [ABSTRACT FROM AUTHOR]

The transition region is a very thin but most peculiar layer in the solar atmosphere located between the solar chromosphere and the corona. It is a key region for understanding coronal heating, solar eruption triggers, and the origin of solar winds. Here, almost all physical parameters (density, temperature, and magnetic fields) have the maximum gradient. Therefore, this region should be highly dynamic, including fast energy releasing and transporting, plasma heating, and particle accelerating. The physical processes can be categorized into two classes: thermal and non-thermal processes. Thermal processes can be observed at ultraviolet (UV) and extreme ultraviolet (EUV) wavelengths via multi-wavelength images. Non-thermal processes accelerate non-thermal electrons and produce radio emissions via the gyrosynchrotron mechanism resulting from the interaction between the non-thermal electrons and magnetic fields. The frequency range spans from several GHz to beyond 100 GHz, in great number of bursts with narrowband, millisecond lifetime, rapid frequency drifting rates, and being referred to as transition region small-scale microwave bursts (TR-SMBs). This work proposes a new type of Solar Ultra-wide Broadband Millimeter-wave Spectrometer (SUBMS) that can be used to observe TR-SMBs. From SUBMS observations, we can derive rich dynamic information about the transition region, such as information about non-thermal energy release and propagation, the flows of plasma and energetic particles, the magnetic fields and their variations, the generation and transportation of various waves, and the formation and evolution of the source regions of solar eruptions. Such an instrument can actually detect the non-thermal signals in the transition region during no flare as well as the eruptive high-energy processes during solar flares. [ABSTRACT FROM AUTHOR]

Well-motivated models of dark matter often result in a population of electrons and positrons within galaxies produced through dark matter annihilation — usually in association with gamma rays. As they diffuse through galactic magnetic fields, these e± produce synchrotron radio emission. The intensity and morphology of this signal depends on the properties of the interstellar medium through which the e± propagate. Using observations of the Andromeda Galaxy (M31) to construct a model of the gas, magnetic fields, and starlight, we set constraints on dark matter annihilation to b b ¯ using the morphology of 3.6 cm radio emission. As the emission signal at the center of M31 is very sensitive to the diffusion coefficient and dark matter profile, we base our limits on the differential flux in the region between 0.9 – 6.9 kpc from the center. We exclude annihilation cross sections ≳ 3 × 10−25 cm3/s in the mass range 10 – 500 GeV, with a maximum sensitivity of 7 × 10−26 cm3/s at 20 – 40 GeV. Though these limits are weaker than those found in previous studies of M31, they are robust to variations of the diffusion coefficient. [ABSTRACT FROM AUTHOR]

Interstellar radio wave scattering leads to flux density fluctuations and pulse broadening of pulsar signals. However, Galactic distribution and the structure of the scattering medium are still poorly understood. Pulsar pulse broadening data available for a relatively large number of pulsars is well suited for such investigations. We collected an up-to-date sample of publicly available pulsar scattering data and introduced a new quantity – the reduced scattering strength |$\tilde{\tau }$| to study the Galactic distribution of pulsar scattering in the Milky Way. We show that the current observations are dominated by two distinct pulsar populations: a local and an inner-Galactic one separated by |$\tilde{\tau }=10^{-5.1}$|  s cm6 pc−1. The stronger electron density fluctuations associated with the inner-Galactic population naturally explain the observed steepening of pulsar scattering time τ–dispersion measure relation. We measure an inner disc region with |$3\, {\rm kpc}\ \lt\ \rm r\ \lt\ 5.5\, {\rm kpc}$| from the Galactic centre to have a scattering scale height of about 0.28 kpc, supporting a correlation between interstellar radio scattering and structures associating with the ionized gas and stellar activities. [ABSTRACT FROM AUTHOR]

We report the discovery of a faint radio filament near PSR J0538+2817 in the NVSS, CGPS, and the Rapid ASKAP Continuum Survey data. This pulsar is plausibly associated with the supernova that gave rise to the Spaghetti nebula (Simeis 147). The structure is one-sided and appears to be almost aligned (within 17 degrees) with the direction of the pulsar's proper motion, but in contrast to the known cases of pulsar radio tails, it is located ahead of the pulsar. At the same time, this direction is also approximately (within 5 degrees) perpendicular to the axis of the extended non-thermal X-ray emission around the pulsar. No X-ray or optical emission is detected from the filament region, although the end point of the radio filament appears to be adjacent to a filament of Hα emission. We speculate that this structure might represent a filament connecting pulsar wind nebula (PWN) with the ambient interstellar medium filled with relativistic electrons escaping the pulsar nebula, i.e. a radio analogue of X-ray filaments of Guitar and Lighthouse PWNs and filaments of non-thermal radio emission in the Galactic Centre. [ABSTRACT FROM AUTHOR]

In the magnetically dominated corona, loop-like structures are expected to undergo pulsating events which are highly structured in time and classified into different types from strictly periodic to irregular. In the case of periodic pulsations, they differ in their characteristic period: from tens of minutes (associated with global large-scale structure oscillations) to milliseconds (fast oscillations associated with a small local scale). These pulsations are strongly related to the basic physical properties of the solar corona and the evolution of magnetic loop-like structures that make up the entire solar atmosphere. This contribution describes a real-world scenario where a route to chaos and reverse processes take place. We examine the dynamic characteristics of a group of a train of pulsations at metric waveband solar radio emission as it evolves in time. The associated time series was recorded with the radio polarimeter of the INAF Trieste Astronomical Observatory, Basovizza Station on April 17, 2002, with a resolution time of 10 ms. Possible scenarios and mechanisms for the observed deterministic-chaos alternating regimes are discussed. [ABSTRACT FROM AUTHOR]

• Investigated CR-solar activity parameters relationship using KAAU, Rc = 14.8 GV, muon detector data. • Regression, ANN, and power spectral analyses were used. • Found significant correlations between CRs and IMF, F10.7, and V. • ANN provided slightly more accurate predictions than regression analysis. • The obtained results are in agreements with those obtained by several investigators. The objective of this study was to examine the relationship between cosmic rays (CR) and various solar activity parameters, including the interplanetary magnetic field (B), solar radio emission flux at 10.7 cm (F10.7), solar wind speed (V), solar wind density (N), solar wind pressure (P), and the variance of the interplanetary magnetic field vector (σF). The CR data collected from 2007 to 2013 were obtained using a muon detector situated at King Abdulaziz University (KAAU) in Jeddah, Saudi Arabia, with a rigidity cutoff of 14.8 GV. To explore the correlation between the CR data and the selected parameters, three distinct methods were employed: regression analysis, artificial neural network (ANN), and power spectral analysis. Regression analysis revealed significant positive correlations between CR muons and plasma pressure (R = 0.1, p < 0.05), as well as solar wind speed (R = 0.1, p < 0.05). On the other hand, negative correlations were observed between CRs and radio flux (R = 0.75, p < 0.05), as well as interplanetary magnetic field (R = 0.1, p < 0.05). However, no significant correlations were found between CRs and plasma density or the variance of the interplanetary magnetic field vector (p > 0.05). Furthermore, multivariable correlation analyses were conducted to explore the relationship between CR muons and the considered parameters, resulting in only marginal improvement. For comparison purposes, data from the King Abdulaziz City for Science and Technology (KACST) muon detector in Riyadh, Saudi Arabia (with a rigidity cutoff of 14.4 GV), as well as CR data from Oulu NM (with a rigidity cutoff of 0.3 GV), were utilized for the same period as the KAAU data. The correlation results indicated that the relationships between the CR data from the three detectors and some of the considered parameters were consistent. However, the strength of the correlations and the magnitudes of the slopes exhibited variations. ANN procedures were also employed to compare the efficiency of neural network analysis in forecasting CR muons based on solar activity parameters. The Multilayer Perceptron (MLP) Module trained using the backpropagation learning algorithm was utilized to build a neural network model and assess its accuracy. The results indicated that the ANN method provided slightly more accurate predictions compared to regression analysis. Finally, Fast Fourier Transform (FFT) analyses were conducted to examine the presence of periodicities between the CRs and the variables under consideration. The analysis revealed several shared periodicities, including cycles spanning 270–277 days, 146–158 days, 89–95 days, 66–73 days, and 21–31 days. [ABSTRACT FROM AUTHOR]

With the exponential development of MEMS (Micro-Electromechanical Systems) in the last decade, emphasis has been placed on the construction of IoT devices in conjunction with an appropriate information system to assist citizens in various fields (transportation, trade, etc.). More specifically, in the health sector,, there are specific IoT devices which can monitor a patient's health condition or provide environmental data for the area, information which affects health quality conditions. In densely populated areas and especially in large cities, in terms of environmental pollution, as well as the known issue of air pollution, citizens are also exposed to solar radiation (ultraviolet UVA UVB radiation), as well as to noise pollution in areas where people live and work. Ultraviolet radiation, especially during the summer months, is responsible for skin cancer and various eye diseases, while noise pollution can create mental disorders in humans, especially in children. In this article, a low-cost solar radiation and noise pollution monitoring station is presented. The parts that compose the station and its implementation are a microcontroller (TTGO-OLED32) with an integrated LoRa device, an ultraviolet radiation sensor and sound sensors. In addition, a mini ups device is used in case of power failure and a GPS device is utilized for the location point. The measurements are obtained by the sensors every ten minutes and are transmitted via the LoRa network to an application server in which the user has direct access to the environmental data of a specific area. In conclusion, the data obtained from such IoT devices help in the study of cities to optimize factors in people's lives. [ABSTRACT FROM AUTHOR]