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We investigate the seasonal variations of ion precipitation, utilizing observations from the Mars Atmosphere and Volatile Evolution mission spanning from 2014 January 4 to 2023 February 14. Our analysis reveals that a diminishing pattern characterizes the transition from Mars season L s 0°–180° to Mars season L s 180°–360°, manifesting as a reduction in precipitating ion fluxes. Additionally, we discern a significant influence of the crustal magnetic field on the seasonal variations in precipitating ion fluxes. Intriguingly, within regions where the crustal magnetic field exhibits a strong quasi-horizontal orientation, opposite seasonal trends become evident. The underlying physical mechanism driving these seasonal variations in ion precipitation is probably attributed to the mass loading effect that may decelerate the solar wind and influence the magnetic pileup. A detailed investigation is further demanded in the future. [ABSTRACT FROM AUTHOR]

Partially ionized plasma is a common occurrence in astrophysical and space environments. The emergence and development of plasma instabilities are significantly impacted by the inelastic collisions between the ions and neutrals in the partially ionized plasma, such as the charge exchange. In this study, the effect of the ion–neutral collisions on the sheared E × B flow was experimentally investigated. In the weak collision range, the shear-driven plasma instability, such as Kelvin–Helmholtz instability, was excited by the velocity-sheared flow. However, increasing ion–neutral collisions resulted in a decrease in the magnitude of the sheared E × B flow due to charge exchange–induced drag forces. Consequently, the Kelvin–Helmholtz instability is suppressed, and the Rayleigh–Taylor instability is triggered. The underlying mechanism was elucidated through experimental findings and numerical analysis. The result of this study proposes that a transition between the two modes occurred with increasing ion–neutral collision strength. It could be applied to the study of the solar chromosphere and prominence and planetary ionospheres, where plasma is partially ionized and the sheared E × B flow is often encountered. [ABSTRACT FROM AUTHOR]

In this paper, we present a new tool to investigate the interaction of the solar wind with Venus with the approach of a global multifluid magnetohydrodynamics (MHD) model. The continuity, momentum, and energy equations for H+, O+, O 2 + , and CO 2 + are solved self-consistently together with Faraday's law. The photochemistry of ionospheric ions are considered as the source term in the density, momentum, and energy equations for each ion. We found that the simulated ionospheric density, temperature, and the bow shock location are consistent with previous observations and simulations for both the solar maximum and minimum. The simulated magnetic fields also agree well with the Venus Express observations. Meanwhile, the high-resolving power and low numerical diffusion makes the model capable of capturing the fine structures of the Venusian-induced magnetosphere, such as the Kelvin–Helmholtz instability and the nightside wake. The escape rates have also been estimated and the results are similar to previous estimations. The high-resolution model could be an efficient tool for the exploration of the fine structures of the Venusian space environment system, and also for the application to other unmagnetized planets. [ABSTRACT FROM AUTHOR]

Abstract We present a new web service (http://transplanet.irap.omp.eu/) dedicated to the modeling of planetary ionospheres. Thanks to the development made for IRAP ionospheric model IPIM, it uses a unified description of the different ionized environments (presently Venus, Earth, Mars and Jupiter). The service provides a complete set of parameters characterizing these environments, including the concentration, velocities, temperatures, production rates of the different ions and electron heating rates. It is based on a modular approach allowing for selection of species, date of simulation and location. It is intended to be a support tool to data processing and analysis and we describe how simulation results can be used for such a purpose. The output format has been chosen to ease the interface with external data processing or vizualization tools, including online services. This web service is an open service which aims at providing users with the most relevant and consistent description of the couplings in planetary space environments and it will evolve in a way to increase user control on the simulation through a simplified Human-machine interface (HMI). [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • During post-sunset period ionospheric irregularities (EPBs) diffracts GNSS signals. • High rate of EPBs in low-latitudinal region can mask CIDs during post-sunset period. • CIDs can be captured even after post-sunset period in the high-latitudinal region. • EPBs production rate also depends upon seasonal/longitudinal parameters of the globe. Abstract Ionospheric disturbances induced by various natural (e.g., earthquakes, volcanic eruption, thunderstorms, meteorite showers, solar eclipses) or anthropogenic (e.g., nuclear explosions, launching of space shuttles) processes can be detected through change in Total Electron Content (TEC) in the F-layer. These ionospheric perturbations can be captured by worldwide expanding geodetic (GNSS) networks, mainly during the day time, when the solar radiation ionizes the air molecules. However, during post-sunset period, strong ionospheric irregularities (known as Equatorial Plasma Bubbles, EPBs) develop due to the classical configuration for the Rayleigh-Taylor (R-T) instability that diffracts navigation and communication signals. Here we use various instances of ionospheric disturbances triggered by natural processes (e.g., earthquakes and volcanic eruption), in the recent decade to investigate the spatiotemporal and seasonal effects of ionospheric irregularities on the GNSS signals. Our study suggests that in the low-latitudinal region (e.g., Sumatra, Mexico), such ionospheric irregularities can mask the ionospheric perturbations due to the higher production rate of EPBs. Hence detection of such co-seismic TEC anomaly becomes difficult. However, in the high-latitudinal region (e.g., Iceland, Alaska), due to the lower production rate of EPBs, ambient ionospheric irregularities are insignificant and hence coseismic TEC anomalies can be captured even during night time. We argue that the production rate of EPBs further depends upon seasonal and longitudinal parameters on the globe. [ABSTRACT FROM AUTHOR]

The extent to which a magnetosphere protects its planetary atmosphere from stellar wind ablation depends upon how well it prevents energy and momentum exchange with the atmosphere and how well it traps otherwise escaping plasma. We focus on the former, and provide a formalism for estimating approximate upper limits on mass, energy, and momentum capture, and use them to constrain loss rates. Our approach quantifies a competition between the local deflection of incoming plasma by a planetary magnetic field and the increase in area for solar wind mass capture provided by this magnetosphere when the wind and planetary fields incur magnetic reconnection. Solar wind capture can be larger for a magnetized planet versus an unmagnetized planet with small ionosphere, even if the rate of energy transfer is less. We find this to be the case throughout Earth's history since the lunar forming impact – the likely start of the geodynamo. Focussing of incoming charged particles near the magnetic poles can increase the local energy flux for a strong enough planetary field and weak enough wind, and we find that this may be the case for Earth's future. The future protective role of Earth's magnetic field would then depend on its ability to trap outgoing plasma. This competition between increased collection area and reduced inflow speed from a magnetosphere is likely essential in determining the net protective role of planetary fields and its importance in sustaining habitability, and can help explain the current ion loss rates from Mars, Venus, and Earth. [ABSTRACT FROM AUTHOR]

Many space plasmas (especially electrons generated in planetary ionospheres) exhibit fine-detailed structures that are challenging to fully resolve with the energy resolution of typical space plasma analyzers (10% → 20%). While analyzers with higher resolution have flown, generally this comes at the expense of sensitivity and temporal resolution. We present a new technique for measuring plasmas with extremely high energy resolution through the combination of a top-hat Electrostatic Analyzer (ESA) followed by an internally mounted Retarding Potential Analyzer (RPA). When high resolutions are not required, the RPA is grounded, and the instrument may operate as a typical general-purpose plasma analyzer using its ESA alone. We also describe how such an instrument may use its RPA to remotely vary the geometric factor (sensitivity) of a top hat analyzer, as was performed on the New Horizons Solar Wind at Pluto and MAVEN SupraThermal and Thermal Ion Composition instruments. Finally, we present results from laboratory testing of our prototype, showing that this technique may be used to construct an instrument with 1.6% energy resolution, constant over all energies and angles. [ABSTRACT FROM AUTHOR]

The magnetization of a planet significantly changes the nature of atmospheric escape, and the question of whether a planetary field shields atmosphere from erosion by the solar wind or not remains open. Ion escape processes from Mars are investigated under two hypothetical conditions, namely, no intrinsic magnetic field and weak intrinsic dipole field cases under present solar wind conditions based on multispecies magnetohydrodynamics simulations. The existence of a weak dipole field results in an enhancement of the tailward flux of planetary ions through the four escape channels. Two channels are associated with the open fields at the poles, and the others are caused by magnetic reconnection between the planetary and solar wind magnetic fields at the flank magnetopause. The ion escape rate with the weak dipole is greater than in the no‐dipole case. The enhancement is significant for O2+ and CO2+, suggesting ion escape from the low‐altitude ionosphere. Plain Language Summary: Present Mars has a thin atmosphere and little water on the surface. Space missions have provided some evidences for the existence of liquid water and a thick atmosphere on ancient Mars. These evidences suggest Mars has experienced significant atmospheric loss up to the present. Ion outflow is one of the important atmospheric loss mechanisms. In the present day, Mars does not have a global magnetic field such as that of Earth, and thus, ions escape by the direct interaction with the solar wind (influenced to some extent by Mars' crustal fields). In contrast, it is expected that ancient Mars had a global magnetic field. The global magnetic field forms the magnetosphere around the planet, perhaps changing the ion escape mechanisms. In this study, a numerical simulation of the Mars‐solar wind interaction is used to compare ion escape for the case of no planetary field with a case where a weak global magnetic field is assumed. The weak global magnetic field yields four escape routes associated with open magnetic fields and magnetic reconnection. The escape rate of heavy ions increases by ~25% compared to the nondipole case, particularly facilitating the escape of O2+ and CO2+ present in the low‐altitude ionosphere. Key Points: The ion escape rate increases when a weak intrinsic dipole magnetic field is introducedThe weak intrinsic field facilitates four escape routes, through cusps and magnetic reconnections between the IMF and planetary fieldsThe enhancement of the escape rate is more pronounced for O2+ and CO2+ than O+, suggesting the ion escape from the low‐altitude ionosphere [ABSTRACT FROM AUTHOR]

The IZMIRAN database of Forbush effects and interplanetary disturbances has been used to study long-term changes in the number and magnitude of Forbush effects in the last six solar cycles (1957-2016) for cosmic rays of rigidity of 10 GV. Solar activity cycles have been shown to be well expressed in data of Forbush effects, especially in large magnitude events that almost disappear in minima. The changes in the distribution of Forbush effects and the decrease in their average values from solar activity maximum to minimum are explained by the predominance of cosmic-ray variations due to the action of coronal holes at low activity. It should be noted that the current cycle involves fewer and generally weaker Forbush effects than in the previous five cycles. For each month, an FD index combining the magnitude and number of Forbush effects and convenient for studying long-term variations has been proposed and calculated. [ABSTRACT FROM AUTHOR]

The set of experiments in 2017 included the forecasting of geo- and heliophysical conditions in the ionosphere, the choice of heating regimes at a minimum critical frequency of the F2 ionospheric layer, analysis of the ionosphere radio sounding results and measurements of geomagnetic perturbations using ground-based facilities, study of the potential for higher efficiency and probability of artificial effects on the ionosphere, and the establishment of a correlation between geomagnetic field variations and the radio heating facility cyclogram. The experiments were carried out with a combination of new heating conditions (pulse ratio, period of action, two-frequency and continuous heating, variations in radiated power, polarization, shortwave radiation direction, etc.) in the intervals between recurrent magnetic storms. Geomagnetic field pulsations (in accordance with the cyclogram) and substorm effects were stimulated by the SURA facility against a background of quiet geophysical conditions. [ABSTRACT FROM AUTHOR]

The Electric Field Detector (EFD) for space ionosphere electric field measurement is described. The EFD is one of the payloads of the China Seismo-Electromagnetic Satellite (CSES) space mission. The EFD measures the variation of the ionosphere electric field due to perturbations from solar, seismic and anthropic phenomena in a wideband from dc up to 3.5 MHz. The EFD will fly on board of the CSES, scheduled to be launched in February 2018. In order to investigate plasma performance of the EFD, the plasma parameters are measured with a Langmuir Probe(LP) and Retarding Potential Analyzers(RPA) in a simulated ionospheric plasma environment. The relevant quantities are obtained as a function of the plasma parameters (i.e. plasma density, electron temperature and ion mass) and system parameters like the orbital velocity, the probe dimensions, the photoelectron current emission and the bias current injected into the probes by the internal constant current source. Here is presented plasma characteristics of the EFD probe. The plasma coupling currents of the EFD probe are calculated analytically. The potential of the EFD probe is measured and calculated analytically. [ABSTRACT FROM AUTHOR]

A methodology has been developed for the physical (laboratory) simulation of the prolonged exposure of a space debris object to high-energy ions of a plasma plume for removing the object into low-Earth orbit with its subsequent burning in the Earth’s atmosphere. The methodology is based on the equivalence criteria of two modes of exposure (in the Earth’s ionosphere and in the setup) and the procedure for accelerated resource tests in terms of the sputtering of the space debris material and its deceleration by a plasma jet in the Earth’s ionosphere. [ABSTRACT FROM AUTHOR]

The possibilities of using the Martian soil subsurface sounding radar for investigating the structure of the plasma shell surrounding the planet have been considered. Based on the numerical modeling results and actual soil sounding data, it has been shown that the soil sounding mode of the radio-locating MARSIS radar can be used to assess the structure of the Martian ionosphere. As the emitted signals pass to the planet’s surface, it is possible to use the reflected signals to estimate the total electron content of the Martian ionosphere along the flight track of the spacecraft. [ABSTRACT FROM AUTHOR]

The topside ionosphere of Mars is known to show variability and transient topside layers. In this study, we analyzed the electron density profiles measured by the radio occultation technique aboard the Mars Global Surveyor spacecraft to study the topside ionosphere of Mars. The electron density profiles that we used in the present study span between 1998 and 2005. All the measurements are done from the northern high latitudes, except 220 profiles which were measured in the southern hemisphere, where strong crustal magnetic fields are present. We binned the observations into six measurement periods: 1998, 1999-north, 1999-south, 2000–2001, 2002–2003, and 2004–2005. We found that the topside ionosphere in the southern high latitudes is more variable than that from the northern hemisphere. This feature is clearly seen with fluctuations of wavelengths less than 20 km. Some of the electron density profiles show a transient topside layer with a local maximum in electron density between 160 km and 210 km. The topside layer is more prone to occur in the southern hemispheric crustal magnetic field regions than in the other regions. In addition, the peak density of the topside layer is greater in regions of strong crustal magnetic fields than in other regions. The variability of the topside ionosphere and the peak density of the topside layer, however, do not show one-to-one correlation with the strength of the crustal magnetic fields and magnetic field inclination. The results of the present study are discussed in the light of current understanding on the topside ionosphere, transient topside layers, and the role of crustal magnetic fields on plasma motions. [ABSTRACT FROM AUTHOR]

The study of planetary ionospheres within our solar system offers a variety of settings to probe mechanisms of photo-ionization, chemical loss, and plasma transport. Ionospheres are a minor component of upper atmospheres, and thus their mix of ions observed depends on the neutral gas composition of their parent atmospheres. The same solar irradiance (x-rays and extreme-ultra-violet vs. wavelength) impinges upon each of these atmospheres, with solar flux magnitudes changed only by the inverse square of distance from the Sun. If all planets had the same neutral atmosphere—with ionospheres governed by photochemical equilibrium (production = loss)—their peak electron densities would decrease as the inverse of distance from the Sun, and any changes in solar output would exhibit coherent effects throughout the solar system. Here we examine the outer planet with the most observations of its ionosphere (Saturn) and compare its patterns of electron density with those at Earth under the same-day solar conditions. We show that, while the average magnitudes of the major layers of molecular ions at Earth and Saturn are approximately in accord with distance effects, only minor correlations exist between solar effects and day-to-day electron densities. This is in marked contrast to the strong correlations found between the ionospheres of Earth and Mars. Moreover, the variability observed for Saturn's ionosphere (maximum electron density and total electron content) is much larger than found at Earth and Mars. With solar irradiance changes far too small to cause such effects, we use model results to explore the roles of other agents. We find that water sources from Enceladus at low latitudes, and ‘ring rain’ at middle latitudes, contribute substantially to variability via water ion chemistry. Thermospheric winds and electrodynamics generated at auroral latitudes are suggested causes of high latitude ionospheric variability, but remain inconclusive due to the lack of relevant observations. [ABSTRACT FROM AUTHOR]

We develop models of the interaction of Rossby wave disturbances in the northern and southern ionospheres of Saturn. We show that interhemispheric field-aligned currents allow the exchange of vorticity, modifying the background Rossby wave propagation speed. This leads to interaction of the northern and southern Rossby wave periods. In a very simple symmetric model without a plasma disk the periods merge when the overall conductivity is sufficiently high. A more complex model taking account of the inertia of the plasma disk and the asymmetry of the two hemispheres predicts a rich variety of possible wave modes. We find that merging of the northern and southern periods can only occur when (i) the conductivities of both hemispheres are sufficiently low (a criterion that is fulfilled for realistic parameters) and (ii) the background Rossby wave periods in the two hemispheres are identical. We reconcile the second criterion with the observations of a merged period that also drifts by noting that ranges of Rossby wave propagation speeds are possible in each hemisphere. We suggest that a merged disturbance in the plasma disk may act as an ‘anchor’ and drive Rossby waves in each hemisphere within the range of possible propagation speeds. This suggestion predicts behaviour that qualitatively matches the observed merging and splitting of the northern and southern rotation periods that occurred in 2013 and 2014. Low conductivity modes also show long damping timescales that are consistent with the persistence of the periodic signals. [ABSTRACT FROM AUTHOR]

A comparative study aimed to investigate the equatorial and low-latitude spread-F occurrences for moderate solar activity (MSA) and high solar activity (HSA), was carried out considering concurrent observations made in some ionospheric stations, which identify three separate longitudinal sectors: Chiang Mai (CGM; 18.8 ° N, 98.9 ° E, mag. Lat. 13.2 ° N) and Chumphon (CPN; 10.7 ° N, 99.4 ° E, mag. Lat. 3.2 ° N), Thailand; Palmas (PAL; 10.2 ° S, 311.8 ° E, mag. Lat. 0.9 ° S) and São José dos Campos (SJC; 23.2 ° S, 314.1 ° E, mag. Lat. 14.0 ° S), Brazil; Tucumán (TUC; 26.9 ° S, 294.6 ° E, mag. Lat. 16.8 ° S), Argentina. Spread-F phenomena recorded during the equinoctial months of September and October 2010, March and April 2011, for MSA, March and April 2014, September and October 2014, for HSA, were classified in two different modes: range spread-F (RSF) and frequency spread-F (FSF). The satellite trace (ST) occurrence was also investigated as possible precursor of spread-F events. When comparing the results of equatorial (CPN and PAL) and low-latitude (CGM, SJC, and TUC) stations, some common features independently of the solar activity emerge: (1) a prevalence of RSF signatures is observed in the time interval 20:00–03:00 LT, while FSF occurrences prevail in the time interval 03:00–06:00 LT; (2) STs are confirmed to be a possible precursor of RSF occurrences. For HSA, at equatorial latitudes, spread-F occurrences in the Thai sector (CPN) are higher than those observed in the Brazilian sector (PAL). When comparing the results of low-latitude stations of CGM, SJC, and TUC some unusual aspects characterizing the morphology of spread-F occurrences emerge: (1) contrary to the Thai and Argentine sectors, in the Brazilian sector (SJC), RSF and FSF appearances in September, for HSA, are observed with relatively long persistence times between about 03:00-06:00 LT and 01:00-03:00 LT respectively, while balanced RSF and FSF occurrences with short persistence times are observed for months for MSA; (2) a prevalence of FSF at CGM during the first half of September for MSA, never observed in the Brazilian and Argentine areas. During years of LSA and MSA common morphological aspects are found at CGM and SJC, that is a predominance of FSF, with the lowest persistence times characterizing SJC. This suggests that the low-latitude behaviour of spread-F occurrences, under different levels of solar activity, at least in the longitude sectors here analysed, can be to a some extent generalized. [ABSTRACT FROM AUTHOR]

There is extensive evidence for ionospheric effects associated with earthquake-related atmospheric disturbances. Although the existence of earthquake precursors is controversial, one suggested method of detecting possible earthquake precursors and tsunamis is by observing possible ionospheric effects of atmospheric waves generated by such events. To study magneto-acoustic-gravity waves in the atmosphere, we have derived a general dispersion relation including the effects of the Earth's magnetic field. This dispersion relation can be used in a general atmospheric ray tracing program to calculate the propagation of magneto-acoustic-gravity waves from the ground to the ionosphere. The presence of the Earth's magnetic field in the ionosphere can radically change the dispersion properties of the wave. The general dispersion relation obtained here reduces to the known dispersion relations for magnetoacoustic waves and acoustic-gravity waves in the corresponding particular cases. The work described here is the first step in achieving a generalized ray tracing program permitting propagation studies of magneto-acoustic-gravity waves. [ABSTRACT FROM AUTHOR]

A physicochemical model of excited polar ionosphere has been presented. The model makes it possible to calculate vertical profiles of concentrations of the following excited and ionized constituents: O , N , O(S), O(D), O(P), O(D), O(S), N(S), N(D), N(P), NO, NO, N, N(AΣ ), N(BП), N(WΔ), and N(B′Σ ) and the electron concentration during electron precipitations. The energy spectrum of the electrons at the upper boundary of the ionosphere and concentrations of neutral constituents are the input parameters of the model. A model has been compiled based on available publications and includes 56 physicochemical reactions that influence concentrations of the aforementioned constituents in the polar ionosphere. The method of calculating vertical profiles of the excitation rates of atmospheric gases and proper allowance for the electron-vibrational kinetics in the processes of exciting the triplet states of N are specific features of the presented model. The ionospheric model has been approbated using the results of the coordinated rocket-satellite experiment. The agreement between the modeling results and experimental data best for the time being is achieved. [ABSTRACT FROM AUTHOR]

Main properties of multiply charged molecular ions (energetics, structure, stability, lifetime and fragmentation dynamics) are relevant to know and to model the behavior of gaseous plasmas, planetary ionospheres, and astrophysical environments. Experimental measurements of the kinetic energy released of fragment ions produced by the Coulomb explosion of molecular dications (doubly charged molecular species) originating by double photoionization of CO2 molecules, are reported and discussed. The kinetic energy released, as a function of the UV photon energy in the range of 34-50 eV, is extracted from the electron-ion-ion coincidence spectra recorded by using tunable synchrotron radiation coupled with ion imaging techniques at the GasPhase beam line of ELETTRA Synchrotron Light Laboratory Trieste, Italy. This kind of experiment allows assessing the probability of escape for simple ionic species in the ionosphere of Mars and Titan. The kinetic energy released, measured in the case of O+ and CO+ fragment ions, are ranging between 1.0-5.0 and 0.4-3.0 eV, respectively. These values are large enough to allow such ionic species in participating in the atmospheric escape from Mars (only O+ ions) and Titan (both O+ and CO+ ions) into space. In the case of Mars, we suggest a possible rationalization for the observed behavior of the O+ and CO22+ ion density profiles by Viking 1 lander and Mariner 6 spacecraft. [ABSTRACT FROM AUTHOR]

Previous studies of Jupiter's upper atmosphere often assume that the mid-to-low latitude ionosphere is corotating, but a model describing an observed asymmetry in hydrogen Lyman-α emission (∼1000 km above the 1 bar level) disagrees with this assumption. From measurements of the Doppler shifted H 3 + ν 2 Q ( 1 , 0 − ) line at 3.953 μ m using the IRTF, the line-of-sight velocities of the H 3 + ions were derived in the planetary reference frame and found to be 0.091 ± 0.25 0.33 e m 0 e x km 0.33 e m 0 e x s − 1 , 0.0082 ± 0.30 0.33 e m 0 e x km 0.33 e m 0 e x s − 1 and 0.31 ± 0.51 0.33 e m 0 e x km 0.33 e m 0 e x s − 1 0.33 e m 0 e x in 1998, 2007 and 2013 respectively. These zero velocities represent corotation at the mid-to-low latitude region of Jupiter's ionosphere. There is no evidence of flows associated with the hydrogen Lyman-α emission asymmetries detected in the peak H 3 + emission layer (∼550 km above the 1 bar level), and we assert that the H 3 + ions in Jupiter's mid-to-low latitude are rigidly corotating. [ABSTRACT FROM AUTHOR]

A multifluid model is used to investigate how Saturn's magnetosphere affects ionosphere. The model includes a magnetospheric plasma temperature of 2 eV as a boundary condition. The main results are: (1) H + ions are accelerated along magnetic field lines by ambipolar electric fields and centrifugal force, and have an upward velocity of about 10 km/s at 8000 km; (2) the ionospheric plasma temperature is 10,000 K at 5000 km, and is significantly affected by magnetospheric heat flow at high altitudes; (3) modeled electron densities agree with densities from occultation observations if the maximum neutral temperature at a latitude of 54˚ is about 900 K or if electrons are heated near an altitude of 2500 km; (4) electron heating rates from photoelectrons (≈100 K/s) can also give agreement with observed electron densities when the maximum neutral temperature is lower than 700 K (note that Cassini observations give 520 K); and (5) the ion temperature is high at altitudes above 4000 km and is almost the same as the electron temperature. The ionospheric height-integrated Pedersen conductivity, which affects the magnetospheric plasma velocity, varies with local time with values between 0.4 and 10 S. We suggest that the sub-corotating ion velocity in the inner magnetosphere depends on the local time, because the conductivity generated by dust–plasma interactions in the inner magnetosphere is almost comparable to the ionospheric conductivity. This indicates that magnetosphere–ionosphere coupling is highly important in the Saturn system. [ABSTRACT FROM AUTHOR]

Ground-based phase wind-up effect (GPWU) is caused by the rotation of receiving antenna. It had been studied and applied in rapidly rotation platforms, such as sounding rocket, guided missile and deep space exploration. In Global Navigation Satellite System high accuracy positioning applications, however, most studies treated it as an error source and focused on eliminating this effect in Precision Point Positioning and Real Time Kinematic (RTK) positioning. The GPWU effect is also sensitive to the rotational status of the antenna, in particular the yaw angle variations. In this paper we explore the feasibility of yaw angle determination of relatively slow rotation platforms based on the GPWU effect. We use the geometry-free carrier phase observations from a RTK base and a moving station receivers to estimate the cumulative yaw angle of the moving platform. Several experiments, including rotating platform tests, vehicle and shipborne tests were carried out. The cumulative errors of rotating platform tests are under 0.38 $$^{\circ }$$ , indicating good long-term accuracy of the GPWU determined yaw angle. But the RMS are in a range of 11.98 $$^{\circ }$$ and 17.39 $$^{\circ }$$ , indicating the errors, such as multipath effect, are not negligible and should be further investigated. The RMS of vehicle and shipborne tests using a base station of 9-11 km are 24.77 $$^{\circ }$$ and 23.66 $$^{\circ }$$ . In order to evaluate the influence of the differential ionospheric delay, another vehicle test was carried out using a base station located less than 1 km to the vehicle. The RMS reduces to 15.11 $$^{\circ }$$ , which gains 39.00 % improvement than before, and demonstrates that the differential ionospheric delay even from a few kilometers long baseline still cannot be neglected. These tests validate the feasibility of GPWU for real-time yaw angle determination. Since this method is able to determine the yaw angle with a minimum one satellite, such a unique feature provides potential applications for attitude determination in the environment with poor sky visibility. [ABSTRACT FROM AUTHOR]

When sensing Earth's ionosphere using multiple Global Navigation Satellite Systems (GNSSs), special care needs to be taken with the receiver differential code bias (DCB) contributions to the error budget. We propose a method that is able to time-wisely retrieve the Between-Receiver DCBs (BR-DCBs) from code measurements collected by a zero-baseline setup, thereby eliminating most common error sources. We base our investigations on dual-frequency GPS (L1 + L2), BeiDou (B1 + B2), and Galileo (E1 + E5a) measurements collected in 2013 with a 30 second sampling rate by four multi-GNSS receivers of three types connected to one common antenna. For each receiver-pair, we determine the time-wise estimates of GPS/GEO/IGSO/MEO/Galileo BR-DCBs from the corresponding code measurements. We confirm that (1) the time-wise estimates of BR-DCBs for all tested receiver-pairs exhibit good intra-day stability and (2) the daily weighted average (DWA) estimates of GEO/IGSO/MEO BR-DCBs are inconsistent for receiver-pairs of mixed type, due to the presence of BeiDou code inter-satellite-type biases (ISTBs). We also identify likely factors accounting for variability in DWA estimates of BR-DCBs over a one-year interval. Copyright © 2016 Institute of Navigation Copyright © 2016 Institute of Navigation [ABSTRACT FROM AUTHOR]

Visibility scintillation resulting from wave propagation through the turbulent ionosphere can be an important source of noise at low radio frequencies (ν ≲ 200 MHz). Many low-frequency experiments are underway to detect the power spectrum of brightness temperature fluctuations of the neutral-hydrogen 21-cm signal from the Epoch of Reionization (EoR: 12 ≳ z ≳ 7, 100 ≲ ν ≲ 175 MHz). In this paper, we derive scintillation noise power spectra in such experiments while taking into account the effects of typical data processing operations such as self-calibration and Fourier synthesis. We find that for minimally redundant arrays such as LOFAR and MWA, scintillation noise is of the same order of magnitude as thermal noise, has a spectral coherence dictated by stretching of the snapshot uv-coverage with frequency, and thus is confined to the well-known wedge-like structure in the cylindrical (two-dimensional) power spectrum space. Compact, fully redundant (dcore ≲ rF ≈ 300 m at 150 MHz) arrays such as HERA and SKA-LOW (core) will be scintillation noise dominated at all baselines, but the spatial and frequency coherence of this noise will allow it to be removed along with spectrally smooth foregrounds. [ABSTRACT FROM AUTHOR]

On April 23, 2015, the VEI4 (volcanic explosive index) Calbuco volcano abruptly erupted in Chile and the Mw7.9 Nepal earthquake occurred on April 25. In order to investigate the similarities and differences between total electron content (TEC) anomalies preceding these two types of geophysical activities, the TEC time series over preparation zones before the volcanic eruption and earthquake extracted from global ionosphere map were analyzed. We used sunspot numbers (SSN), B z , Dst, and Kp indices to represent the solar-terrestrial environment and eliminate the effects of solar and geomagnetic activities on ionosphere by the sliding interquartile range method with the 27-day window. The results indicate that TEC-negative and -positive anomalies appeared in the 14th and 6th day before the eruption, respectively. The anomalies lasted about 4–6 h with a magnitude of 15–20 TECU. The TEC anomalies were also observed on the 14th and 6th day before the Nepal earthquake with a duration of 6–8 h, and the absolute magnitude of TEC anomalies was within 12–20 TECU. These findings indicate that the magnitude of TEC anomalies preceding volcanic eruption was larger, and the duration of TEC anomalies before the earthquake was longer, which may be associated with their particular physical mechanisms. The TEC anomalies before the Nepal earthquake in the Eastern hemisphere occurred in the afternoon local time, but those before the eruption were observed in the night local time. Peak regions of TEC anomalies did not coincide with the epicenters of geophysical activities, and the TEC anomalies also appeared in the magnetic conjugated region. Both the TEC anomalies in the preparation zone and conjugated region were distributed near the boundaries of equatorial anomaly zone and moved along the boundaries. In the moving process, sometimes the extent or magnitude of TEC anomalies in the conjugated region was larger than that in the preparation zone. Many more GPS stations and receivers should be distributed along the boundaries of equatorial anomaly zone, which will be significant in predicting volcanic eruptions and earthquakes in the low-mid-latitudes. [ABSTRACT FROM AUTHOR]

In the mainland of China, the number of ionospheric research groups is more than 10. Around 110 articles related to ionospheric physics have been published during 2014-2015. In this annual national report of the Committee on Space Research (COSPAR), we will outline some recent progresses in ionospheric studies conducted by the Chinese mainland scientists in the past 2 years. These investigations cover (1) the ionosphere responses to geomagnetic activities; (2) ionospheric climatology and structures; (3) couplings between the ionosphere, plasmasphere and lower atmosphere, and possible seismic signatures in the ionosphere; (4) ionospheric irregularities and scintillation; (5) ionospheric models, data assimilation and simulations; (6) ionospheric dynamics and electrodynamics; (7) progresses in the observation methodology and technique; and (8) planetary ionospheres. Such investigations will strengthen our ability to monitor the ionosphere, provide a better understanding of the ionospheric states and the underlying fundamental processes, and improve the ionospheric modeling, forecasting, and related applications. [ABSTRACT FROM AUTHOR]

Low energy secondary ions ejected by the solar wind are an important component of tenuous exospheres surrounding airless bodies, since these ions carry information on the planetary surface composition. In this work we examine the dependence of secondary-ion abundance, as a function of energy and mass, on surface composition. The surface compositions of two Apollo soils (10084 and 62231) and a synthetic Corning glass lunar simulant were measured with X-ray photoelectron spectroscopy and correlated with the spectra of secondary-ions ejected from the same soils by 4 keV He ions. XPS spectra for lunar soils show that the surface compositions are similar to the bulk, but enriched in Fe and O, while depleted in Mg and Ca. 4 keV He irradiation on the lunar soils and a glass simulant preferentially removes O and Si, enriching the surface in Al, Ti, Mg, and Ca. Secondary-ion species ejected from the Apollo soils by 4 keV He include: Na + , Mg + , Al + , Si + , Ca + , Ca ++ , Ti + , Fe + , and molecular species: NaO + , MgO + and SiO + . Secondary ion energy distributions for lunar soil 10084 and 62231 rise rapidly, reach a maxima at ∼5 eV for molecular ions and Na + , ∼7.5 eV for Fe + , and ∼10 eV for Mg + , Al + , Si + , Ca + and Ti + , then decrease slowly with energy. We present species-dependent relative conversion factors for the derivation of atomic surface composition from secondary-ion count rates for 4 keV He irradiation of lunar soils 10084 and 62231, as well as the Corning glass lunar simulant. [ABSTRACT FROM AUTHOR]

GPS data obtained from two equatorial stations of Ilorin (geographic Lat. 8.53°N, Long. 4.57°E and geomagnetic Lat. 10.57°N, Long. 78.56°E) and Toro (geographic Lat. 10.12°N, Long. 9.12°W and geomagnetic Lat. 11.36°N, Long. 83.35°E) have been used to study the response of vertical TEC to four geomagnetic storms which occurred during 22–23 Jan, 23–26 Jan, 6–8 March and 8–11 March in the year 2012. Three of these events were in the category of moderate storms (−50 > Dst > −100 nT) while the 8–11 March event was in the category of intense storm (−100 > Dst > −200 nT). Results obtained show that TEC response can either be enhancement or depletion irrespective of the category of the storm. While the main and recovery phases of the 23–26 Jan. and 6–8 March, 2012 moderate events produced TEC enhancement at Toro, TEC depletions were observed at Ilorin during the main phases of these two events. The result of the analysis of the 22–23 Jan, 2012 moderate storms with sudden commencement shows that response of TEC to the main phase was depletion at both stations. Percentage deviations in TEC with respect to quiet time averages ranged between −19% and +21% at Toro and −42% to +34% at Ilorin. The moderate storms with gradual commencement (i.e. 23–26 Jan and 6–8 March events) have different effects on TEC at the two stations. While the initial and recovery phases of the 23–24 Jan event produced significant TEC enhancement at both stations (+119% at Toro and +82% at Ilorin), the recovery phase of the 6–8 March event produced enhancement at Toro and depletion at Ilorin. The intense storm of 8–11 March, 2012 produced almost opposite effects on TEC at the two stations. While the effect at Toro was TEC enhancement of 0% to +116% during all the three phases, TEC fluctuations at Ilorin ranged between −36% and +28% during the initial and main phases. [ABSTRACT FROM AUTHOR]

The classical multidimensional scaling (MDS) method is introduced and applied in the study of the hour-to-hour ionospheric variability based on the ionospheric foF2 observed at three ionosonde stations in East-Asia in 2002 and 2007. Results from the matrix eigen decompositions indicate that the annual part of the ionospheric variation is large in middle latitude and solar maximum period (2002) while low in the low latitude and solar minimum period (2007). The connectivity maps of the hour-to-hour ionospheric variability based on MDS method show some common diurnal features. The ionospheric connectivity between adjacent hours near noon hours and near midnight hours is high. The ionospheric connectivity between adjacent hours near sunrise hours and near sunset hours is poor, especially for the sunrise hours. Also there are latitudinal and solar activity dependences in this kind of connectivity. These results revealed from the ionospheric connectivity maps are useful physically and in practice for the ionospheric forecasting on the hour-to-hour scale. [ABSTRACT FROM AUTHOR]

Field-aligned currents couple energy between the Earth's magnetosphere and ionosphere and are responsible for driving both micro and macro motions of plasma and neutral atoms in both regimes. These currents are believed to be a contributing energy source for ion acceleration in the polar ionosphere and may be detected via measurements of magnetic gradients along the track of a polar orbiting spacecraft, usually the north-south gradients of the east-west field component. The detection of such gradients does not require observatory class measurements of the geomagnetic field. The Magnetic Field instrument (MGF) measures the local magnetic field onboard the Enhanced Polar Outflow Probe (e-POP) satellite by using two ring-core fluxgate sensors to characterize and remove the stray spacecraft field. The fluxgate sensors have their heritage in the MAGSAT design, are double wound for reduced mass and cross-field dependence, and are mounted on a modest 0.9 m carbon-fiber boom. The MGF samples the magnetic field 160 times per sec (∼50 meters) to a resolution of 0.0625 nT and outputs data at 1952 bytes per second including temperature measurements. Its power consumption is 2.2 watts, and its noise level is 7 pT per root Hz at 1 Hz. [ABSTRACT FROM AUTHOR]

Substorm current wedge (SCW) formation is associated with global magnetic field reconfiguration during substorm expansion. We combine a two-loop model SCW (SCW2L) with a background magnetic field model to investigate distortion of the ionospheric footpoint pattern in response to changes of different SCW2L parameters. The SCW-related plasma sheet footprint shift results in formation of a pattern resembling an auroral bulge, the pole-ward expansion of which is controlled primarily by the total current in the region 1 sense current loop (I1). The magnitude of the footprint latitudinal shift may reach - 10° corrected geomagnetic latitude (CGLat) during strong sub-storms (I1 = 2 MA). A strong helical magnetic field around the field-aligned current generates a surge-like region with embedded spiral structures, associated with a westward traveling surge (WTS) at the western end of the SCW. The helical field may also contribute to rotation of the ionospheric projection of narrow plasma streams (auroral streamers). Other parameters, including the total current in the second (region 2 sense) loop, were found to be of secondary importance. Analyzing two consecutive dipolarizations on 17 March 2010, we used magnetic variation data obtained from a dense midlatitude ground network and several magnetospheric spacecraft, as well as the adaptive AM03 model, to specify SCW2L parameters, which allowed us to predict the magnitude of pole-ward auroral expansion. Auroral observations made during the two substorm activations demonstrate that the SCW2L combined with the AM03 model nicely describes the azimuthal progression and the observed magnitude of the auroral expansion. This finding indicates that the SCW-related distortions are responsible for much of the observed global development of bright auroras. [ABSTRACT FROM AUTHOR]

Long-term variability has previously been ob-served in the relative magnitude of annual and semi-annual variations in the critical frequency (related to the peak electron concentration) of the ionospheric F2 layer (foF2). In this paper we investigate the global patterns in such variability by calculating the time varying power ratio of semi-annual to annual components seen in ionospheric foF2 data sequences from 77 ionospheric monitoring stations around the world. The temporal variation in power ratios observed at each station was then correlated with the same parameter calculated from similar epochs for the Slough/Chilton data set (for which there exists the longest continuous sequence of ionospheric data). This technique reveals strong regional variation in the data, which bears a striking similarity to the regional variation observed in long-term changes to the height of the ionospheric F2 layer. We argue that since both the height and peak density of the ionospheric F2 region are influenced by changes to thermospheric circulation and composition, the observed long-term and regional variability can be explained by such changes. In the absence of long-term measurements of thermospheric composition, detailed modelling work is required to investigate these processes. [ABSTRACT FROM AUTHOR]

Until recently, short-term prediction of earthquakes with answers to the main triad of questions (When? Where? What magnitude?) was considered to be an unsolvable problem. And if for the forecast of place and energy (or magnitude) a number of empirical regularities confirmed with theoretical models were set, but the principal possibility of short-term forecast of the time (a period from several days to months) of the beginning of earthquakes was denied by most professionals. To answer the first question of the main triad of forecast there were not reliable empirical regularities and model approaches. This was due to a flashing character in time and mosaic manifestation in the space of many types of earthquake precursors of different geophysical nature and ambiguity of their interpretations. However, the development of Internet technologies and means of ground and space monitoring of different environmental parameters have allowed in real-time to obtain, compare and analyze various anomalies in the Geosphere shells of the Earth: the magnetosphere, the ionosphere, atmosphere, lithosphere and deep layers of the Earth. This has led to a breakthrough in solving the main problems of Geophysics: short-term prediction of strong earthquakes. [ABSTRACT FROM AUTHOR]

The ionospheric response to auroral precipitation at the giant planets is reviewed, using models and observations. The emission processes for aurorae at radio, infrared, visible, ultraviolet, and X-ray wavelengths are described, and exemplified using ground- and space-based observations. Comparisons between the emissions at different wavelengths are made, where possible, and interpreted in terms of precipitating particle characteristics or atmospheric conditions. Finally, the spatial distributions and dynamics of the various components of the aurorae (moon footprints, low-latitude, main oval, polar) are related to magnetospheric processes and boundaries, using theory, in situ, and remote observations, with the aim of distinguishing between those related to internally-driven dynamics, and those related to the solar wind interaction. [ABSTRACT FROM AUTHOR]

The widely used International Reference Ionosphere (IRI) model in simulation/modeling of ionospheric studies specially at low latitudes require performance evaluation. To achieve this objective, we have compared total electron content (TEC) derived from the recent version of IRI model (IRI-2012) over low latitude Indian station Varanasi (Geographic: 25°16′N, 82°59′E; Geomagnetic: 14°55′N, 154°E) with TEC measured from the GPS receiver installed at Varanasi. The results are in good agreement with correlation coefficient ~0.9, and root-mean square deviations generally around 25–70% for diurnal comparisons. The seasonal variability of TEC derived by using the different topside options of the IRI-2012 model (IRI-2001, NeQuick and IRI01-corr) are studied and validated for the three seasons. The IRI-2012 model with all the three topside options significantly overestimates TEC for the station during the winter season of 2012–2013, which has been attributed to discrepancy in foF2 parameter as predicted by the model during the winter season of 2012–2013. This has been confirmed by comparing the foF2 data from COSMIC with IRI model. [ABSTRACT FROM AUTHOR]

This paper presents a contemporary review of vertical coupling in the atmosphere and ionosphere system induced by internal waves of lower atmospheric origin. Atmospheric waves are primarily generated by meteorological processes, possess a broad range of spatial and temporal scales, and can propagate to the upper atmosphere. A brief summary of internal wave theory is given, focusing on gravity waves, solar tides, planetary Rossby and Kelvin waves. Observations of wave signatures in the upper atmosphere, their relationship with the direct propagation of waves into the upper atmosphere, dynamical and thermal impacts as well as concepts, approaches, and numerical modeling techniques are outlined. Recent progress in studies of sudden stratospheric warming and upper atmospheric variability are discussed in the context of wave-induced vertical coupling between the lower and upper atmosphere. [ABSTRACT FROM AUTHOR]

The atmospheres of exoplanets are commonly studied by observing the transit of the planet passing in front of its parent star. The obscuration of part of the stellar disk during a transit will reveal aspects of its surface structure resulting from general centre-to-limb variations (CLVs). These become apparent when forming the ratio between the stellar light in and out of transit. These phenomena can be seen particularly clearly during the progress of a penumbral lunar eclipse, where the Earth transits the solar disk and masks different regions of the solar disk as the eclipse progresses. When inferring the properties of the planetary atmosphere, it is essential that this effect originating at the star is properly accounted for. Using the data observed from the 2014-April-15 lunar eclipse with the ESPaDOnS spectrograph mounted on the Canada France Hawaii Telescope (CFHT), we have obtained for the first time a time sequence of the penumbral spectra. These penumbral spectra enable us to study the centre-to-limb variations of solar Fraunhofer lines when the Earth is transiting Sun. The Na i and Ca ii absorption features reported from previous lunar eclipse observations are demonstrated to be CLV features, which dominate the corresponding line profiles and mask possible planetary signal. Detecting atmospheric species in exoplanets via transit spectroscopy must account for the CLV effect. [ABSTRACT FROM AUTHOR]

Conditions similar to those observed in the solar wind interaction with Venus and Mars where there is a planetary atmosphere in the absence of a global intrinsic magnetic field may also be applicable to Pluto. With up to 24 μbars inferred for the Pluto atmosphere it is possible that the feeble solar photon radiation flux that reaches by its orbit, equivalent to ∼10 −3 that at Earth, is sufficient to produce an ionization component that can be eroded by the solar wind. In view of the reduced solar wind density (∼10 −3 with respect to that at 1 AU) that should be available by Pluto its total kinetic energy will be significantly smaller than that at Earth. However, the parameter values that are implied for the interaction process between the solar wind and the local upper ionosphere are sufficient to produce a plasma wake that should extend downstream from Pluto. In view of its low gravity force the plasma wake should have a wider cross-section than that in the Venus and Mars plasma environment. Since Pluto rotates with the axis tilted ∼30° away from the ecliptic plane the plasma wake will be influenced by a Magnus force that has a large component is the north–south solar polar direction. That force will be responsible for propelling the plasma wake with a component that can be directed away from that plane. It is estimated that transport of solar wind momentum to the upper Pluto’s ionosphere implies rotation periods smaller than that of the solid body, and thus large values of the Magnus force that can increase the orientation of the plasma wake away from the ecliptic plane. [ABSTRACT FROM AUTHOR]

Exospheric neutral atoms and molecules (primarily N 2 , with trace amounts of CH 4 and CO according to our current understanding of Pluto’s atmosphere) escape from Pluto and travel into interplanetary space for millions of kilometers. Eventually, the neutrals are ionized by solar EUV photons and/or by collisions with solar wind electrons. The mass-loading associated with this ion pick-up is thought to produce a comet-like interaction of the solar wind with Pluto. Within a few thousand kilometers of Pluto the solar wind interaction should lead to a magnetic field pile-up and draping, as it does around other “non-magnetic” bodies such as Venus and comets. The structure of plasma regions and boundaries will be greatly affected by large gyroradii effects and the extensive exosphere. Energetic plasma should disappear from the flow within radial distances of a few thousand kilometers due to charge exchange collisions. An ionosphere should be present close to Pluto with a composition that is determined both by the primary ion production and ion-neutral chemistry. One question discussed in the paper is whether or not the ionosphere has a Venus-like sharply defined ionopause boundary or a diamagnetic cavity such as that found around comet Halley. Simple physical estimates of plasma processes and structures in the collision-dominated region are made in this paper and predictions are made for the New Horizons mission. [ABSTRACT FROM AUTHOR]

Far Ultraviolet Nighttime Ionopsheric Photometer (FNIP) is a newly-designed instrument for low earth orbit missions, observing the earth night airglow nadir at OI 135.6 nm emission produced by ionospheric O+e recombination and receiving the horizontal information on nighttime ionosphere with a spatial resolution of about 1.6×3.8. This simple, highly robust instrument excludes OI 130.4 nm emission and Herzberg oxygen bands with lower power and approximately achieves a sensitivity of about 400 counts/s/Rayleigh at 135.6 nm with stray light less than 2 %. Some tests of the instrument have been conducted and the results will be discussed in the end. [ABSTRACT FROM AUTHOR]

The variations of plasma density in topside ionosphere during 23rd/24th solar cycle minimum attract more attentions in recently years. In this analysis, we use the data of electron density (Ne) from DEMETER (Detection of Electromagnetic Emissions Transmitted from Earthquake Regions) satellite at the altitude of 660–710 km to investigate the solstitial and equinoctial asymmetry under geomagnetic coordinate system at LT (local time) 1030 and 2230 during 2005–2010, especially in solar minimum years of 2008–2009. The results reveal that ΔNe (December–June) is always positive over Southern Hemisphere and negative over northern part whatever at LT 1030 or 2230, only at 0–10°N the winter anomaly occurs with ΔNe (December–June) > 0, and its amplitude becomes smaller with the declining of solar flux from 2005 to 2009. The ΔNe between September and March is completely negative during 2005–2008, but in 2009, it turns to be positive at latitudes of 20°S–40°N at LT 1030 and 10°S–20°N at LT 2230. Furthermore, the solstitial and equinoctial asymmetry index (AI) are calculated and studied respectively, which all depends on local time, latitude and longitude. The notable differences occur at higher latitudes in solar minimum year of 2009 with those in 2005–2008. The equinoctial AI at LT 2230 is quite consistent with the variational trend of solar flux with the lowest absolute AI occurring in 2009, the extreme solar minimum, but the solstitial AI exhibits abnormal enhancement during 2008 and 2009 with bigger AI than those in 2005–2007. Compared with the neutral compositions at 500 km altitude, it illustrates that [O/N 2 ] and [O] play some roles in daytime and nighttime asymmetry of Ne at topside ionosphere. [ABSTRACT FROM AUTHOR]

The question about the survival possibility and the life duration of the topside ionosphere equatorial spread F (ESF) plasma bubbles observed in the separate ion component (He + ) is investigated. For this aim the main aeronomy processes, in which plasma bubbles and their He + ions are involved, were under consideration. It was obtained that the main competition takes place between the He + loss reactions (He + –N 2 reaction) and the uplift during linear growth phase (~10 min) of the Rayleigh–Taylor (R–T) instability, when the plasma bubbles are forming. It was revealed that the ambipolar diffusion of the He + ions inside the plasma bubble is the fastest (~1–2 min) in the altitude region up to 500 km and becomes slower (~1 h) above 500 km. On the other hand, the plasma bubbles seen in He + density are pretty stable structures against the cross-field (Bohm) diffusive collapse. It was concluded that the ESF plasma bubbles, reaching the “ceiling” heights, can exist for a night and several morning hours (~10–13 h) and that there is a principal opportunity to observe them in the separate ion component (He + ). [ABSTRACT FROM AUTHOR]

A new hybrid climatological model for long-term prediction of the global TEC was developed. It is based on the global empirical background TEC model constructed by Mukhtarov et al. (2013a,b) and the availability of regularly/new observations from CODE TEC data. The cornerstone of the hybrid model consists of applying the method of autocorrelation prediction of the error and the respective correction of the background model with the predicted error. An important question is how the efficiency of the correction procedure depends on the given offset, i.e. the time distance between the dates for which the prediction is made to that with real data. It was found that the correction is really effective if the error prediction is made for a date with a distance up to 60 days from the date with real data. Then the RMSE decreases from 3.2 TECU (for the global background TEC model) to 2.76 TECU (for the hybrid model) which demonstrates the advantage of the presented in this paper hybrid model for long-term prediction with respect to the originally built background TEC model. [ABSTRACT FROM AUTHOR]

We analyze continuous magnetic observations of ionospheric Alfvén resonator (IAR) emissions at mid-latitude observatory Mondy. The measurements were by a LEMI-30 search-coil magnetometer covering the period from March 2010 to May 2011. The results are compared with data from simultaneous ionospheric sounding data and International Reference Ionosphere (IRI-2012) model parameters. The large amount of observational data allowed us to inspect the daily and seasonal variations in some morphological characteristics of the emissions as well as their relationship to ionospheric conditions. The main factor affecting the duration of the emission is how long the lower ionosphere stays in Earth's shadow. We demonstrate a close inverse correlation between the diurnal and seasonal IAR frequency variations, on the one hand, and changes in the ionospheric critical frequency, f 0 F 2 , on the other. Additionally, the expected emission frequency scale calculated with the IRI-2012 model is in good agreement with the values measured from the emission spectrograms. [ABSTRACT FROM AUTHOR]

Both solar and lunar atmospheric tides are believed to drive ionospheric electrodynamic effects during stratospheric sudden warmings (SSWs), but their relative importance is not well understood. In this study, long-term records (1958–2007) of the geomagnetic field are analyzed to determine the average solar (S) and lunar (L) ionospheric current systems for SSW and non-SSW periods. It is found that the L current intensity is enhanced during SSWs approximately by 75%, while the relative change in the S current intensity is much smaller (~10%). Nonetheless, absolute changes are comparable in the S and L current intensities. At the magnetic equator, semidiurnal perturbations produced by S and L currents reinforce or cancel each other depending on the phase of the moon, creating lunar-dependent recurrent onset in the total effect. These results indicate that both S and L contributions need to be considered to understand ionospheric variability during SSWs. [ABSTRACT FROM AUTHOR]

We report results from the experiment aimed at the artificial excitation of extremely low-frequency (ELF) electromagnetic waves with frequencies corresponding to the frequency of Schumann resonance. Electromagnetic waves with these frequencies can form a standing pattern inside the spherical cavity formed by the surface of the Earth and the ionosphere. In the experiment the ELF waves were excited by heating the ionosphere with X-mode HF electromagnetic waves generated at the High Frequency Active Auroral Research Program (HAARP) facility in Alaska. The experiment demonstrates that heating of the ionosphere can excite relatively large-amplitude electromagnetic waves with frequencies in the range 7.8–8.0 Hz when the ionosphere has a strong F layer, the frequency of the HF radiation is in the range 3.20–4.57 MHz, and the electric field greater than 5 mV/m is present in the ionosphere. [ABSTRACT FROM AUTHOR]

Scientific attention has recently been focused on the coupling of the earth's upper atmosphere and ionosphere. In the present work, we review the advances in this field, emphasizing the studies and contributions of Chinese scholars. This work first introduces new developments in the observation instruments of the upper atmosphere. Two kinds of instruments are involved: optical instruments (lidars, FP interferometers and all-sky airglow imagers) and radio instruments (MST radars and all-sky meteor radars). Based on the data from these instruments and satellites, the researches on climatology and wave disturbances in the upper atmosphere are then introduced. The studies on both the sporadic sodium layer and sporadic E-layer are presented as the main works concerning the coupling of the upper atmosphere and the low ionosphere. We then review the investigations on the ionospheric longitudinal structure and the causative atmospheric non-migrating tide as the main progress of the coupling between the atmosphere and the ionospheric F2-region. Regarding the ionosphere-thermosphere coupling, we introduce studies on the equatorial thermospheric anomaly, as well as the influence of the thermospheric winds and gravity waves to the ionospheric F2-region. Chinese scholars have made much advancement on the coupling of the ionosphere and upper atmosphere, including the observation instruments, data precession, and modeling, as well as the mechanism analysis. [ABSTRACT FROM AUTHOR]

With the rapid increase of GPS/GNSS receivers being deployed and operated in China, real-time GPS data from nearly a thousand sites are available at the National Center for Space Weather, China Meteorology Administration. However, it is challenging to generate a high-quality regional total electron content (TEC) map with the traditional two-dimensional (2-D) retrieval scheme because a large horizontal gradient has been reported over east-south Asia due to the northern equatorial ionization anomaly. We developed an Ionosphere Data Assimilation Analysis System (IDAAS), which is described in this study, using an International Reference Ionosphere (IRI) model as the background and applying a Kalman filter for updated observations. The IDAAS can reconstruct a three-dimensional ionosphere with the GPS slant TEC. The inverse slant TEC correlates well with observations both for GPS sites involved in the reconstruction and sites that are not involved. Based on the IDAAS, simulations were performed to investigate the deviation relative to the slant-to-vertical conversion (STV). The results indicate that the relative deviation induced by slant-to-vertical conversion may be significant in certain instances, and the deviation varies from 0% to 40% when the elevation decreases from 90° to 15°, while the relative IDAAS deviation is much smaller and varies from -5% to 15% without an elevation dependence. Compared with 'true TEC' map derived from the model, there is large difference in STV TEC map but no obvious discrepancy in IDAAS map. Generally, the IDAAS TEC map is much closer to the "true TEC" than is STV TEC map is. It is suggested that three-dimensional inversion technique is necessary for GPS observations of low elevation at an equatorial anomaly region, wherein the high horizontal electron density gradient may produce significant slant-to-vertical deviations using the two-dimensional STV inversion method. [ABSTRACT FROM AUTHOR]

Abstract: Following a long period of observation and investigation beginning in the early 1970s, it has been firmly established that Earth׳s magnetosphere is defined as much by the geogenic plasma within it as by the geomagnetic field. This plasma is not confined to the ionosphere proper, defined as the region within a few density scale heights of the F-region plasma density peak. Rather, it fills the flux tubes on which it is created, and circulates throughout the magnetosphere in a pattern driven by solar wind plasma that becomes magnetically connected to the ionosphere by reconnection through the dayside magnetopause. Under certain solar wind conditions, plasma and field energy is stored in the magnetotail rather than being smoothly recirculated back to the dayside. Its release into the downstream solar wind is produced by magnetotail disconnection of stored plasma and fields both continuously and in the form of discrete plasmoids, with associated generation of energetic Earthward-moving bursty bulk flows and injection fronts. A new generation of global circulation models is showing us that outflowing ionospheric plasmas, especially O+, load the system in a different way than the resistive F-region load of currents dissipating energy in the plasma and atmospheric neutral gas. The extended ionospheric load is reactive to the primary dissipation, forming a time-delayed feedback loop within the system. That sets up or intensifies bursty transient behaviors that would be weaker or absent if the ionosphere did not “strike back” when stimulated. Understanding this response appears to be a necessary, if not sufficient, condition for us to gain accurate predictive capability for space weather. However, full predictive understanding of outflow and incorporation into global simulations requires a clear observational and theoretical identification of the causal mechanisms of the outflows. This remains elusive and requires a dedicated mission effort. [Copyright &y& Elsevier]