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Time-evolving magnetohydrodynamic (MHD) coronal modeling, driven by a series of time-dependent photospheric magnetograms, represents a new generation of coronal simulations. This approach offers greater realism compared to traditional coronal models constrained by a static magnetogram. However, its practical application is seriously limited by low computational efficiency and poor numerical stability. Therefore, we propose an extended magnetic field decomposition strategy and implement it in the implicit MHD model to develop a coronal model that is both efficient and numerically stable enough for simulating the long-term evolutions of the global corona. The traditional decomposition strategies split the magnetic field into a time-invariant potential field and a time-dependent component $\mathbf{B}_1$. It works well for quasi-steady-state coronal simulations where $\left|\mathbf{B}_1\right|$ is typically small. However, as the inner-boundary magnetic field evolves, $\left|\mathbf{B}_1\right|$ can grow significantly larger and its discretization errors often lead to nonphysical negative thermal pressure, ultimately causing the code to crash. In this paper, we mitigate such undesired situations by introducing a temporally piecewise-constant variable to accommodate part of the non-potential field and remain $\left|\mathbf{B}_1\right|$ consistently small throughout the simulations. We incorporate this novel magnetic field decomposition strategy into our implicit MHD coronal model and apply it to simulate the evolution of coronal structures within 0.1 AU over two solar-maximum Carrington rotations. The results show that this coronal model effectively captures observations and performs more than 80 times faster than real time using only 192 CPU cores, making it well-suited for practical applications in simulating the time-evolving corona., Comment: 26 pages,9 figures

The solar corona is highly structured by bunches of magnetic field lines forming either loops, or twisted flux ropes representing prominences/filaments, or very dynamic structures such as jets. The aim of this paper is to understand the interaction between filament channels and jets. We use high-resolution H$\alpha$ spectra obtained by the ground-based Telescope Heliographique pour lEtude du Magnetisme et des Instabilites Solaires (THEMIS) in Canary Islands, and data from Helioseismic Magnetic Imager (HMI) and Atmospheric Imaging Assembly (AIA) aboard the Solar Dynamics Observatory (SDO). In this paper we present a multi-wavelength study of the interaction of filaments and jets. They both consist of cool plasma embedded in magnetic structures. A jet is particularly well studied in all the AIA channels with a flow reaching 100-180 km s$^{-1}$. Its origin is linked to cancelling flux at the edge of the active region. Large Dopplershifts in H$\alpha$ are derived in a typical area for a short time (order of min). They correspond to flows around 140 km s$^{-1}$. In conclusion we conjecture that these flows correspond to some interchange of magnetic field lines between the filament channel and the jets leading to cool plasmoid ejections or reconnection jets perpendicularly to the jet trajectory., Comment: 13 Figures, 14 pages

This paper aims to present the time-dependent coupling between the coronal model COolfluid COroNal UnsTructured (COCONUT) and the heliospheric forecasting tool EUHFORIA. We perform six COCONUT simulations where a flux rope is implemented at the solar surface using either the Titov-D\'emoulin CME model or the Regularized Biot-Savart Laws (RBSL) CME model. At regular intervals, the magnetic field, velocity, temperature, and density of the 2D surface $R_{b}=21.5~\;R_{\odot}$ are saved in boundary files. This series of coupling files is read in a modified version of EUHFORIA to update progressively its inner boundary. After presenting the early stage of the propagation in COCONUT, we examine how the disturbance of the solar corona created by the propagation of flux ropes is transmitted into EUHFORIA. In particular, we consider the thermodynamic and magnetic profiles at L1 and compare them with those obtained at the interface between the two models. We demonstrate that the properties of the heliospheric solar wind in EUHFORIA are consistent with those in COCONUT, acting as a direct extension of the coronal domain. Moreover, the disturbances initially created from the propagation of flux ropes in COCONUT continue evolving from the corona in the heliosphere to Earth with a smooth transition at the interface between the two simulations. Looking at the profile of magnetic field components at Earth and different distances from the Sun, we also find that the transient magnetic structures have a self-similar expansion in COCONUT and EUHFORIA. However, the amplitude of the profiles depends on the flux rope model used and its properties, thus emphasizing the important role of the initial properties in solar source regions for accurately predicting the impact of CMEs.

Large amplitude oscillations commonly occur in solar prominences, triggered by energetic phenomena such as jets and flares. On March 14-15, 2015, a filament partially erupted in two stages, leading to oscillations in different parts. This study explores longitudinal oscillations from the eruption, focusing on the mechanisms behind their initiation, with special attention to the large oscillation on March 15. The oscillations and jets are analyzed using the time-distance technique. For flares and their interaction with the filament, we analyze AIA channels and use the DEM technique. Initially, a jet fragments the filament, splitting it into two segments. One remains in place, while the other detaches and moves. This causes oscillations in both segments: (a) the position change causes the detached segment to oscillate with a period of $69 \pm 3$ minutes; (b) the jet flows cause the remaining filament to oscillate with a period of $62 \pm 2$ minutes. In the second phase, on March 15, another jet seemingly activates the detached filament eruption, followed by a flare. A large longitudinal oscillation occurs in the remnant segment with a period of $72 \pm 2$ minutes and velocity amplitude $73 \pm 1 \, \mathrm{km s^{-1}}$. During the oscillation trigger, bright field lines connect the flare with the filament, appearing only in the AIA 131$\r{A}$ and 94$\r{A}$ channels, indicating the presence of hot plasma. DEM analysis confirms this, showing plasma around 10 MK pushing the prominence from its southeastern side, displacing it along the field lines and starting the oscillation. From this, the flare -- not the preceding jet-triggers the oscillation. The hot plasma flows into the filament channel. We explain how flares trigger large oscillations in filaments by proposing that post-flare loops reconnect with the filament channel's magnetic field., Comment: Accepted for publication in Astronomy and Astrophysics

Solar jets are collimated plasma ejections along magnetic field lines observed in hot (EUV jets) and cool (chromospheric surges) temperature diagnostics. Their trigger mechanisms and the relationship between hot and cool jets are still not completely understood. We aim to investigate the generation of a sequence of active region solar jets and their evolution from the photospheric to the coronal heights. Using the synergy of high spatial and temporal resolution observations by the SST, along with the SDO, we analyze a sequence of solar jets originating in a mixed polarity region between the leading and following sunspots of an active region. We use a NFFF extrapolation technique for deriving the magnetic field topology of the active region. A mixed polarity region is formed over a long period (24 hours) with persistent magnetic flux emergence. This region has been observed as an arch filament system (AFS) in chromospheric SST observations. In this region, negative polarities surrounded by positive polarities create a fan-surface with a null point at a height of 6 Mm detected in the NFFF extrapolation. SST observations in H-beta spectral line reveal a large flux rope over the AFS and moving from the North to South, causing successive EUV and cool jets to move in the East-West direction and later towards the South along the long open loops. The high resolution SST observations (0.038 arcsec per pixel) resolve the dark area observed at the jet base and reveal the existence of an AFS with an extended cool jet which may be the result of a peeling-like mechanism of the AFS. Based on the combined analysis of SST and AIA observations along with extrapolated magnetic topology, it is suggested that the magnetic reconnection site may move southward by approximately 20 Mm until it reaches a region where the open magnetic field lines are oriented North-South., Comment: 14 pages, 11 figures, accepted for publication in A&A

Filament eruptions and coronal mass ejections are physical phenomena related to magnetic flux ropes carrying electric current. A magnetic flux rope is a key structure for solar eruptions, and when it carries a southward magnetic field component when propagating to the Earth. It is the primary driver of strong geomagnetic storms. As a result, developing a numerical model capable of capturing the entire progression of a flux rope, from its inception to its eruptive phase, is crucial for forecasting adverse space weather. The existence of such flux ropes is revealed by the presence of sigmoids in active regions or hot channels by observations from space and ground instruments. After proposing cartoons in 2D, potential, linear, non-linear-force-free-field (NLFFF) and non-force-free-field (NFFF) magnetic extrapolations, 3D numerical magnetohydrodynamic (MHD) simulation models were developed, first in a static configuration and later dynamic data-driven MHD models using high resolution observed vector magnetograms. This paper reviews a few recent developments in data-driven mode, such as the time-dependent magneto-frictional (TMF) and thermodynamic magnetohydrodynamic (MHD) models. Hereafter, to demonstrate the capacity of these models to reveal the physics of observations, we present the results for three events explored in our group: 1. the eruptive X1.0 flare on 28 October 2021; 2. the filament eruption on 18 August 2022; and 3. the confined X2.2 flare on 6 September 2017. These case studies validate the ability of data-driven models to retrieve observations, including the formation and eruption of flux ropes, 3D magnetic reconnection, CME three-part structures and the failed eruption. Based on these results, we provide some arguments for the formation mechanisms of flux ropes, the physical nature of the CME leading front, and the constraints of failed eruptions., Comment: 41 pages, 12 figures, pulished on Reviews of Modern Plasma Physics

Ultra-Wideband (UWB) technology re-emerges as a groundbreaking ranging technology with its precise micro-location capabilities and robustness. This paper highlights the security dimensions of UWB technology, focusing in particular on the intricacies of device fingerprinting for authentication, examined through the lens of state-of-the-art deep learning techniques. Furthermore, we explore various potential enhancements to the UWB standard that could realize a sovereign UWB data network. We argue that UWB data communication holds significant potential in healthcare and ultra-secure environments, where the use of the common unlicensed 2.4~GHz band-centric wireless technology is limited or prohibited. A sovereign UWB network could serve as an alternative, providing secure localization and short-range data communication in such environments., Comment: NetAISys Workshop at ACM Mobisys 2024

Coronal mass ejections (CMEs) stand as intense eruptions of magnetized plasma from the Sun, playing a pivotal role in driving significant changes of the heliospheric environment. Deducing the properties of CMEs from their progenitors in solar source regions is crucial for space weather forecasting. Deducing the properties of CMEs from their progenitors in solar source regions is crucial for space weather forecasting. The primary objective of this paper is to establish a connection between CMEs and their progenitors in solar source regions, enabling us to infer the magnetic structures of CMEs before their full development. To this end, we create a dataset comprising a magnetic flux rope series with varying projection shapes, sizes and toroidal fluxes, using the Regularized Biot-Savart Laws (RBSL). Thereafter, we simulate the propagation of these flux ropes from the solar surface to a distance of 25$R_{\odot}$ with our global coronal MHD model which is named COCONUT. Our parametric survey reveals significant impacts of source flux ropes on the consequent CMEs. We find that the projection shape can influence the magnetic structures of CMEs at 20$R_{\odot}$, albeit with minimal impacts on the propagation speed. However, these impacts diminish as source flux ropes become fat. In terms of toroidal flux, our simulation results demonstrate a pronounced correlation with the propagation speed of CMEs, as well as the successfulness in erupting. This work builds the bridge between the CMEs in the outer corona and their progenitors in solar source regions. Our parametric survey suggests that the projection shape, cross-section radius and toroidal flux of source flux ropes are crucial parameters in predicting magnetic structures and propagation speed of CMEs, providing valuable insights for space weather prediction., Comment: 11 pages, 10 figrues, accepted for publication by A&A

Filament eruption is a common phenomenon in solar activity, but the triggering mechanism is not well understood. We focus our study on a filament eruption located in a complex nest of three active regions close to a coronal hole. The filament eruption is observed at multiple wavelengths: by the GONG, the STEREO, the SUTRI, and the AIA and Helioseismic and Magnetic Imager (HMI) on board the SDO. Thanks to high temporal-resolution observations, we were able to analyze the evolution of the fine structure of the filament in detail. The filament changes direction during the eruption, which is followed by a halo coronal mass ejection detected by the LASCO on board the SOHO. A Type III radio burst was also registered at the time of the eruption. To investigate the process of the eruption, we analyzed the magnetic topology of the filament region adopting a nonlinear force-free-field (NLFFF) extrapolation method and the polytropic global magnetohydrodynamic (MHD) modeling. We modeled the filament by embeddingatwisted fluxropewiththe regularized Biot-Savart Laws (RBSL) method in the ambient magnetic f ield. The extrapolation results show that magnetic reconnection occurs in a fan-spine configuration resulting in a circular flare ribbon. The global modeling of the corona demonstrates that there was an interaction between the filament and open field lines, causing a deflection of the filament in the direction of the observed CME eruption and dimming area. The modeling supports the following scenario: magnetic reconnection not only occurs with the filament itself (the flux rope) but also with the background magnetic field lines and open field lines of the coronal hole located to the east of the flux rope. This multiwavelength analysis indicates that the filament undergoes multiple magnetic reconnections on small and large scales with a drifting of the flux rope.

Coronal Mass Ejections (CMEs) are the main drivers of the disturbances in interplanetary space. Understanding the CME interior magnetic structure is crucial for advancing space weather studies. Assessing the capabilities of a numerical heliospheric model is crucial, as understanding the nature and extent of its limitations can be used for improving the model and the space weather predictions based on it. The present paper aims to test the capabilities of the recently developed heliospheric model Icarus and the linear force-free spheromak model that has been implemented in it. To validate the Icarus space weather modeling tool, two CME events were selected that were observed by two spacecraft located near Mercury and Earth, respectively. This enables testing the heliospheric model computed with Icarus at two distant locations. The source regions for the CMEs were identified, and the CME parameters were determined and later optimized. Different adaptive mesh refinement levels were applied in the simulations to assess its performance by comparing the simulation results to in-situ measurements. The first CME event erupted on SOL2013-07-09T15:24. The modeled time series were in good agreement with the observations both at MESSENGER and ACE. The second CME event started on SOL2014-02-16T10:24 and was more complicated, as three CME interactions occurred in this event. It was impossible to recover the observed profiles without modeling the other two CMEs that were observed, one before the main CME and one afterward. For both CME studies, AMR level 3 was sufficient to reconstruct small-scale features near Mercury, while at Earth, AMR level 4 was necessary due to the radially stretched grid that was used., Comment: 16 pages, 17 figures

Aims. We present further development of the rolling root mean square (rRMS) algorithm. These improvements consist of an increase in computational speed and an estimation of the uncertainty on the recovered diagnostics. This improvement is named the cross root mean square (xRMS) algorithm. Methods. We used the quantile method to recover the statistics of the line profiles in order to study the evolution of the prominence observed by IRIS on 1 October 2019. We then introduced the improvements to rRMS. These improvements greatly increased the computational speed, and this increase in speed allowed us to use a large model grid. Thus, we utilised a grid of 23 940 models to recover the thermodynamic diagnostics. We used the 'good' (but not 'best') fitting models to recover an estimate of the uncertainty on the recovered diagnostics. Results. The maximum line-of-sight (LOS) velocities were found to be 70 km/s. The line widths were mostly 0.4 {\AA} with the asymmetries of most pixels around zero. The central temperature of the prominence was found to range from 10 kK to 20 kK, with uncertainties of approximately +/-5 to +/-15 kK. The central pressure was around 0.2 dyn/cm2, with uncertainties of +/-0.2 to +/-0.3 dyn/cm2. The ionisation degree ranged from 1 to 1000, with uncertainties mostly in the range +/-10 to +/-100. The electron density was mostly 10^10 /cm3, with uncertainties of mostly +/-10^9. Conclusions. The new xRMS algorithm finds an estimation of the errors of the recovered thermodynamic properties. To our knowledge, this is the first attempt at systematically determining the errors from forward modelling. The large range of errors found may hint at the degeneracies present when using a single ion and/or species from forward modelling. In the future, co-aligned observations of more than one ion and/or species should be used to attempt to constrain this problem., Comment: 9 pages, 12 figures

Solar jets are collimated plasma flows moving along magnetic field lines and accelerated at low altitude following magnetic reconnection. Several of them originate from anemone-shaped low-lying arcades and the most impulsive ones tend to be relatively wider and display untwisting motions. We aim to establish typical behaviours and observational signatures in the low atmosphere that can occur in response to the coronal development of such impulsive jets. We analysed an observed solar jet associated with a circular flare ribbon, using high-resolution observations from SST coordinated with IRIS and SDO. We related specifically identified features with those developing in a generic 3D line-tied numerical simulation of reconnection driven jets, performed with the ARMS code. We identified three features in the SST observations: the formation of a hook along the circular ribbon, the gradual widening of the jet through the apparent displacement of its kinked edge towards, and not away from the presumed reconnection site, and the falling back of some of the jet plasma towards a footpoint offset from that of the jet itself. The 3D numerical simulation naturally accounts for these features which were not imposed a priori. Our analyses allow to interpret them in the context of the 3D geometry of the asymmetric swirled anemone loops and their sequences of reconnection with ambient coronal loops. Given the relatively-simple conditions in which the observed jet occurred, together with the generic nature of the simulation that comprised minimum assumptions, we predict that the specific features that we identified and interpreted are probably typical of every impulsive jet, Comment: 13 pages, 8 figures, Accepted for publication in Astronomy and Astrophysics

Aims. The aim of this paper is to consider relationship between the decay of sunspots and convection via the motion of the family of granules and how the diffusion mechanism of magnetic field operates in a decaying sunspot. Methods. We report the decay of a sunspot observed by the 1.6m Goode Solar Telescope (GST) with the TiO Broadband Filter Imager (BFI) and the Near-InfraRed Imaging Spectropolarimeter (NIRIS). The analysis was aided by the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamic Observatory (SDO). In the first step, we followed the decay of the sunspot with HMI data over three days by constructing its evolving area and total magnetic flux. In the second step, the high spatial and temporal resolution of the GST instruments allowed us to analyze the causes of the decay of the sunspot. Afterward, we followed the emergence of granules in the moat region around the sunspot over six hours. The evolution of the trees of fragmenting granules (TFGs) was derived based on their relationship with the horizontal surface flows. Results. We find that the area and total magnetic flux display an exponential decrease over the course of the sunspot decay. We identified 22 moving magnetic features (MMFs) in the moats of pores, which is a signature of sunspot decay through diffusion. We note that the MMFs were constrained to follow the borders of TFGs during their journey away from the sunspot. Conclusions. The TFGs and their development contribute to the diffusion of the magnetic field outside the sunspot. The conclusion of our analysis shows the important role of the TFGs in sunspot decay. Finally, the the family of granules evacuates the magnetic field.

Aims. Recurring jets are observed in the solar atmosphere, which can erupt intermittently. By the observation of intermittent jets, we want to understand the causes of periodic eruption characteristics. Methods. We report intermittent jets observed by the GST. The analysis was aided by 1400 {\AA} and 2796 {\AA} data from IRIS.These observational instruments allowed us to analyze the temporal characteristics of jet events. Results. The jet continued for up to 4 hours. The time distance diagram shows that the peak of the jet has obviously periodic eruption characteristics (5 minutes) during 18:00 UT-18:50 UT. We also found periodic brightening phenomenon (5 minutes) during jets bursts in the observed bands in the Transition Region (1400 {\AA} and 2796 {\AA}), which may be a response to intermittent jets in the upper solar atmosphere.The time lag is 3 minutes. Evolutionary images in the TiO band revealed the horizontal movement of granulation at the location of jet. Compared to the quiet region of the Sun, we found that the footpoint of the jet is enhanced at the center of the H {\alpha} spectral line profile, with no significant changes in the line wings. This suggests the presence of prolonged heating at the footpoint of the jet. In the mixed-polarity magnetic field region of the jet, we observed magnetic flux emergence, cancellation, and shear indicating possible intermittent magnetic reconnection. That is confirmed by the NLFFF model reconstructed using the magneto-friction method. Conclusions. The multi-wavelength analysis indicates that the events we studied were triggered by magnetic reconnection caused by mixed-polarity magnetic fields. We suggest that the horizontal motion of the granulation in the photosphere drives the magnetic reconnection, which is modulated by p-mode oscillations.

Context: Coronal mass ejections (CMEs) are rapid eruptions of magnetized plasma that occur on the Sun, which are known as the main drivers of adverse space weather. Accurately tracking their evolution in the heliosphere in numerical models is of utmost importance for space weather forecasting. Aims: The main objective of this paper is to implement the Regularized Biot-Savart Laws (RBSL) method in a new global corona model COCONUT. This approach has the capability to construct the magnetic flux rope with an axis of arbitrary shape. Methods: We present the implementation process of the RBSL flux rope model in COCONUT, which is superposed onto a realistic solar wind reconstructed from the observed magnetogram around the minimum of solar activity. Based on this, we simulate the propagation of an S-shaped flux rope from the solar surface to a distance of 25 solar radii. Results: Our simulation successfully reproduces the birth process of a CME originating from a sigmoid in a self-consistent way. The model effectively captures various physical processes and retrieves the prominent features of the CMEs in observations. In addition, the simulation results indicate that the magnetic topology of the CME flux rope at around 20 solar radii deviates from a coherent structure, and manifests as a mix of open and closed field lines with diverse footpoints. Conclusions: This work demonstrates the potential of the RBSL flux rope model in reproducing CME events that are more consistent with observations. Moreover, our findings strongly suggest that magnetic reconnection during the CME propagation plays a critical role in destroying the coherent characteristic of a CME flux rope., Comment: 14 pages, 8 figures, accepted for publication in A&A

Magnetic flux ropes are a bundle of twisted magnetic field lines produced by internal electric currents, which are responsible for solar eruptions and are the major drivers of geomagnetic storms. As such, it is crucial to develop a numerical model that can capture the entire evolution of a flux rope, from its birth to death, in order to predict whether adverse space weather events might occur or not. In this paper, we develop a data-driven modeling that combines a time-dependent magneto-frictional approach with a thermodynamic magnetohydrodynamic model. Our numerical modeling successfully reproduces the formation and confined eruption of an observed flux rope, and unveils the physical details behind the observations. Regarding the long-term evolution of the active region, our simulation results indicate that the flux cancellation due to collisional shearing plays a critical role in the formation of the flux rope, corresponding to a substantial increase in magnetic free energy and helicity. Regarding the eruption stage, the deformation of the flux rope during its eruption can cause an increase in the downward tension force, which suppresses it from further rising. This finding may shed light on why some torus-unstable flux ropes lead to failed eruptions after large-angle rotations. Moreover, we find that twisted fluxes can accumulate during the confined eruptions, which would breed the subsequent eruptive flares., Comment: 30 pages, 10 figures, Accepted for ApJ

The aim of this paper is to present the implementation of two new CME models in the space weather forecasting tool, EUHFORIA. We introduce the two toroidal CME models analytically, along with their numerical implementation in EUHFORIA. One model is based on the modified Miller-Turner (mMT) solution, while the other is derived from the Soloviev equilibrium, a specific solution of the Grad-Shafranov equation. The magnetic field distribution in both models is provided in analytic formulae, enabling a swift numerical computation. After detailing the differences between the two models, we present a collection of thermodynamic and magnetic profiles obtained at Earth using these CME solutions in EUHFORIA with a realistic solar wind background. Subsequently, we explore the influence of their initial parameters on the time profiles at L1. In particular, we examine the impact of the initial density, magnetic field strength, velocity, and minor radius. In EUHFORIA, we obtained different thermodynamic and magnetic profiles depending on the CME model used. We found that changing the initial parameters affects both the amplitude and the trend of the time profiles. For example, using a high initial speed results in a fast evolving and compressed magnetic structure. The speed of the CME is also linked to the strength of the initial magnetic field due to the contribution of the Lorentz force on the CME expansion. However, increasing the initial magnetic field also increases the computation time. Finally, the expansion and integrity of the magnetic structure can be controlled via the initial density of the CME. Both toroidal CME models are successfully implemented in EUHFORIA and can be utilized to predict the geo-effectiveness of the impact of real CME events. Moreover, the current implementation could be easily modified to model other toroidal magnetic configurations.

The properties of pre-eruptive structures and coronal mass ejections (CMEs) are characterized by those of their footpoints, the latter of which thus attract great interest. However, how to identify the footpoints of pre-eruptive structures and how to identify the footpoints with ground-based instruments, still remain elusive. In this work, we study an arc-shaped structure intruding in the sunspot umbra. It is located close to the (pre-)eruptive flux rope footpoint and is thus expected to help identify the footpoint. We analyse this arc-shaped structure, which we name as "sunspot scar", in a CME event on 2012 July 12 and in two CME events in observationally-inspired MHD simulations performed by OHM and MPI-AMRVAC. The sunspot scar has a more inclined magnetic field with a weaker vertical component and a stronger horizontal component relative to that in the surrounding umbra and manifests as a light bridge in the white light passband. The hot field lines anchored in the sunspot scar are spatially at the transition between the flux rope and the background coronal loops, and temporally in the process of the slipping reconnection which builds up the flux rope. The sunspot scar and its related light bridge mark the edge of the CME flux rope footpoint, and especially, the edge of the pre-eruptive flux rope footpoint in the framework of "pre-eruptive structures being flux ropes". Therefore, they provide a new perspective for the identification of pre-eruptive and CME flux rope footpoints, and also new methods for studying the properties and evolution of pre-eruptive structures and CMEs with photospheric observations only., Comment: 25 pages, 14 figures, accepted for publication in Astronomy & Astrophysics

Extreme-ultraviolet (EUV) waves are one of the large-scale phenomena on the Sun. They are defined as large propagating fronts in the low corona with speeds ranging from a few tens km/s to a multiple of 1000 km/s. They are often associated with solar filament eruptions, flares, or coronal mass ejections (CMEs). EUV waves show different features, such as, wave and nonwave components, stationary fronts, reflection, refraction, and mode conversion. Apart from these, they can hit the nearby coronal loops and filaments/prominences during their propagation and trigger them to oscillate. These oscillating loops and filaments/prominences enable us to diagnose coronal parameters such as the coronal magnetic field strength. In this article, we present the different observed features of the EUV waves along with existing models., Comment: 10 pages, 3 figures, 3rd BINA workshop proceeding

Prominences are large magnetic structures in the corona filled by cool plasma with fast evolving fine structure. We aim to better understand the plasma conditions in the fine structure of a quiescent prominence including two transient horns observed at the bottom of the cavity using the high-resolution spectrograph IRIS and the MulTi-Raies (MTR) spectrograph of the THEMIS in the Canary Islands. We analysed the spectra obtained in H-alpha by THEMIS and MgII by IRIS and compare them with a grid of 23940 1D radiative transfer models which include a prominence-to-corona transition region (PCTR). The full observed profiles of MgII in each pixel are fitted completely by synthesised profiles with xRMS (Cross RMS; an improved version of the rolling root mean square (rRMS) method). When the RMS is below a certain threshold value, we recover the plasma conditions from the parameters of the model best fitting the observed line profile. This criterion is met in two regions (the horns and edge of the prominence) where the line profiles can generally be described as single peaked. The 1D models suggest that two different kinds of model atmospheres correspond to these two regions. The region at the edge is found to be fitted mainly with isothermal and isobaric models, while the other area (the horns) is seen to be fitted with models with a PCTR that have optical thicknesses <5. In the prominence edge, the theoretical relationship between the integrated intensities in H-alpha and MgII is verified and corresponds to low emission measure values. In these regions the electron density is ~10^10 cm^{-3}, while it is one order of magnitude less in the horn regions. In the horns, we find some profiles are best fitted with models with high mean temperatures. This suggests that the hot PCTR found in the horns could be interpreted as prominence plasma in condensation phase at the bottom of the coronal cavity., Comment: 24 pages, 19 figures, manuscript accepted to publication in A&A

Solar filaments often exhibit rotation and deflection during eruptions, which would significantly affect the geoeffectiveness of the corresponding coronal mass ejections (CMEs). Therefore, understanding the mechanisms that lead to such rotation and lateral displacement of filaments is a great concern to space weather forecasting. In this paper, we examine an intriguing filament eruption event observed by the Chinese H{\alpha} Solar Explorer (CHASE) and the Solar Dynamics Observatory (SDO). The filament, which eventually evolves into a CME, exhibits significant lateral drifting during its rising. Moreover, the orientation of the CME flux rope axis deviates from that of the pre-eruptive filament observed in the source region. To investigate the physical processes behind these observations, we perform a data-constrained magnetohydrodynamic (MHD) simulation. Many prominent observational features in the eruption are reproduced by our numerical model, including the morphology of the eruptive filament, eruption path, and flare ribbons. The simulation results reveal that the magnetic reconnection between the flux-rope leg and neighboring low-lying sheared arcades may be the primary mechanism responsible for the lateral drifting of the filament material. Such a reconnection geometry leads to flux-rope footpoint migration and a reconfiguration of its morphology. As a consequence, the filament material hosted in the flux rope drifts laterally, and the CME flux rope deviates from the pre-eruptive filament. This finding underscores the importance of external magnetic reconnection in influencing the orientation of a flux rope axis during eruption., Comment: 25 pages, 14 figures, Accepted for publication in ApJ

The propagation of Interplanetary Coronal Mass Ejections (ICMEs) in the heliosphere is influenced by many physical phenomena, related to the internal structure of the ICME and its interaction with the ambient solar wind and magnetic field. As the solar magnetic field is modulated by the 11-year dynamo cycle, our goal is to perform a theoretical exploratory study to assess the difference of propagation of an ICME in typical minimum and maximum activity backgrounds. We define a median representative CME at 0.1~au, using both observations and numerical simulations, and describe it using a spheromak model. We use the heliospheric propagator European Heliospheric FORecasting Information Asset (EUHFORIA) to inject the same ICME in two different background wind environments. We then study how the environment and the internal CME structure impact the propagation of the ICME towards Earth, by comparison with an unmagnetized CME. At minimum of activity, the structure of the heliosphere around the ecliptic causes the ICME to slow down, creating a delay with the polar parts of the ejecta. This delay is more important if the ICME is faster. At maximum of activity, a southern coronal hole causes a northward deflection. For these cases, we always find that the ICME at maximum of activity arrives first, while the ICME at minimum of activity is actually more geo-effective. The helicity sign of the ICME is also a crucial parameter but at minimum of activity only, since it affects the magnetic profile and the arrival time of up to 8 hours., Comment: 25 pages, 16 figures, accepted in ApJ

Solar coronal mass ejections (CMEs) can catch up and interact with preceding CMEs and solar wind structures to undergo rotation and deflection during their propagation. We aim to show how interactions undergone by a CME in the corona and heliosphere can play a significant role in altering its geoeffectiveness predicted at the time of its eruption. We consider a case study of two successive CMEs launched from the active region NOAA 12158 in early September 2014. The second CME was predicted to be extensively geoeffective based on the remote-sensing observations of the source region. However, in situ measurements at 1~au recorded only a short-lasting weak negative Bz component followed by a prolonged positive Bz component. The EUropean Heliosphere FORecasting Information Asset (EUHFORIA) is used to perform a self-consistent 3D MHD simulation of the two CMEs in the heliosphere. The initial conditions of the CMEs are determined by combining observational insights near the Sun, fine-tuned to match the in situ observations near 1~au, and additional numerical experiments of each individual CME. By introducing CME1 before CME2 in the EUHFORIA simulation, we modelled the negative Bz component in the sheath region ahead of CME2 whose formation can be attributed to the interaction between CME1 and CME2. To reproduce the positive Bz component in the magnetic ejecta of CME2, we had to initialise CME2 with an orientation determined at 0.1~au and consistent with the orientation interpreted at 1~au, instead of the orientation observed during its eruption. EUHFORIA simulations suggest the possibility of a significant rotation of CME2 in the low corona in order to explain the in situ observations at 1~au. Coherent magnetic field rotations, potentially geoeffective, can be formed in the sheath region as a result of CME-CME interactions in the heliosphere even if the individual CMEs are not geoeffective., Comment: The paper is accepted in A&A journal for publication on May 5, 2023

The aim of this paper is to demonstrate the possible use of the new coronal model COCONUT to compute a detailed representation of a numerical CME at 0.1~AU, after its injection at the solar surface and propagation in a realistic solar wind, as derived from observed magnetograms. We present the implementation and propagation of modified Titov-D\'emoulin (TDm) flux ropes in the COCONUT 3D MHD coronal model. The background solar wind is reconstructed in order to model two opposite configurations representing a solar activity maximum and minimum respectively. Both were derived from magnetograms which were obtained by the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamic Observatory (SDO) satellite. We track the propagation of 24 flux ropes, which differ only by their initial magnetic flux. We especially investigate the geometry of the flux rope during the early stages of the propagation as well as the influence of its initial parameters and solar wind configuration on 1D profiles derived at 0.1~AU. At the beginning of the propagation, the shape of the flux ropes varies between simulations during low and high solar activity. We find dynamics that are consistent with the standard CME model, such as the pinching of the legs and the appearance of post-flare loops. Despite the differences in geometry, the synthetic density and magnetic field time profiles at 0.1~AU are very similar in both solar wind configurations. These profiles are similar to those observed further in the heliosphere and suggest the presence of a magnetic ejecta composed of the initially implemented flux rope and a sheath ahead of it. Finally, we uncover relationships between the properties of the magnetic ejecta, such as density or speed and the initial magnetic flux of our flux ropes., Comment: 20 pages, 13 figures

Coronal jets are eruptions identified by a collimated, sometimes twisted spire. They are small-scale energetic events compared with flares. Using multi-wavelength observations from the Solar Dynamics Observatory/Atmospheric Imaging Assembly (SDO/AIA) and a magnetogram from Hinode/Spectro-Polarimeter (Hinode/SP), we study the formation and evolution of a jet occurring on 2019 March 22 in the active region NOAA 12736. A zero-$\beta$ magnetohydrodynamic (MHD) simulation is conducted to probe the initiation mechanisms and appearance of helical motion during this jet event. As the simulation reveals, there are two pairs of field lines at the jet base, indicating two distinct magnetic structures. One structure outlines a flux rope lying low above the photosphere in the north of a bald patch region and the other structure shows a null point high in the corona in the south. The untwisting motions of the observed flux rope was recovered by adding an anomalous (artificial) resistivity in the simulation. A reconnection occurs at the bald patch in the flux rope structure, which is moving upwards and simultaneously encounters the field lines of the null point structure. The interaction of the two structures results in the jet while the twist of the flux rope is transferred to the jet by the reconnected field lines. The rotational motion of the flux rope is proposed to be an underlying trigger of this process and responsible for helical motions in the jet spire., Comment: 17pages, 9 figures. Accepted for publication in The Astrophysical Journal

Solar filament eruptions, flares and coronal mass ejections (CMEs) are manifestations of drastic release of energy in the magnetic field, which are related to many eruptive phenomena from the Earth magnetosphere to black hole accretion disks. With the availability of high-resolution magnetograms on the solar surface, observational data-based modelling is a promising way to quantitatively study the underlying physical mechanisms behind observations. By incorporating thermal conduction and radiation losses in the energy equation, we develop a new data-driven radiative magnetohydrodynamic (MHD) model, which has the capability to capture the thermodynamic evolution compared to our previous zero-\b{eta} model. Our numerical results reproduce major observational characteristics of the X1.0 flare on 2021 October 28 in NOAA active region (AR) 12887, including the morphology of the eruption, kinematic of flare ribbons, extreme-ultraviolet (EUV) radiations, and two components of the EUV waves predicted by the magnetic stretching model, i.e., a fast-mode shock wave and a slower apparent wave due to successive stretching of magnetic field lines. Moreover, some intriguing phenomena are revealed in the simulation. We find that flare ribbons separate initially and ultimately stop at the outer stationary quasi-separatrix layers (QSLs). Such outer QSLs correspond to the border of the filament channel and determine the final positions of flare ribbons, which can be used to predict the size and the lifetime of a flare before it occurs. In addition, the side view of the synthesized EUV and white-light images exhibit typical three-part structures of CMEs, where the bright leading front is roughly cospatial with the non-wave component of the EUV wave, reinforcing the magnetic stretching model for the slow component of EUV waves., Comment: 46 pages, 15 figures, accepted for publication in The Astrophysical Journal Supplement

Large-amplitude oscillations (LAOs) are often detected in filaments. Using multiwavelength observations, their origin can be traced back to the interaction with eruptions and jets. We present two different case studies as observational evidence in support of 2.5D MHD numerical experiments that show that the LAOs in the filament channels can be initiated by solar jets. In the two studied events, we can identify a quadrupolar configuration with an X-point at the top of the parasitic region suggestive of a classical null-point. A reconnection flow emanates from this structure leading to a jet that propagates along the filament channel. In both cases we can identify the quiescent and eruptive phases of the jet. The triggered LAOs have periods of around 70-80 minutes and are damped after a few oscillations. The minimum magnetic field intensity inferred with seismology for the filament turns out to be around 30 Gauss. We conclude that the two case studies are consistent with the recent numerical model of Luna and Moreno-Insertis (2021), in which the LAOs are initiated by jets. The relationship between the onset of the jet and filament oscillations is straight-forward for the first case and less for the second case. In the second event, although there is some evidence, we cannot rule out other possibilities such as activity unrelated to the null-point or changes in the magnetic structure of the filament. Both jets are associated with very weak flares which did not launch any EUV wave. Therefore the role of EUV waves for triggering the filament oscillations can be eliminated for these two case., Comment: 12 pages, 13 figures, Accepted for publication in Astronomy & Astrophysics

We present the observations of an extreme-ultraviolet (EUV) wave, which originated from the active region (AR) NOAA 12887 on 28 October 2021 and its impact on neighbouring loops. The event was observed by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO) satellite at various wavebands and by the Solar TErrestrial RElations Observatory-Ahead (STEREO-A) with its Extreme-Ultraviolet Imager (EUVI) and COR1 instruments with a different view angle than SDO. We show that the EUV wave event consists of several waves as well as non-wave phenomena. The wave components include: the fast-mode part of the EUV wave event, creation of oscillations in nearby loops, and the appearance of wave trains. The non-wave component consists of stationary fronts. We analyze selected oscillating loops and find that the periods of these oscillations range from 230 - 549 s. Further, we compute the density ratio inside and outside the loops and the magnetic field strength. The computed density ratio and magnetic field are found in the range of 1.08 - 2.92 and 5.75 - 8.79 G, respectively. Finally, by combining SDO and STEREO-A observations, we find that the observed EUV wave component propagates ahead of the CME leading edge., Comment: 27 pages, 11 figures

Many prominences are supported by magnetic flux ropes. One important question is how we can determine whether the flux rope is weakly-twisted or strongly-twisted. In this paper, we attempted to check whether prominences supported by weakly-twisted and strongly-twisted flux ropes can manifest different features so that we might distinguish the two types of magnetic structures by their appearance. We performed pseudo three-dimensional simulations of two magnetic flux ropes with different twists. We found that the resulting two prominences differ in many aspects. The prominence supported by a weakly-twisted flux rope is composed mainly of transient threads, forming high-speed flows inside the prominence. Its horns are evident. Conversely, the one supported by a highly-twisted flux rope consists mainly of stable quasi-stationary threads, including longer independently trapped threads and shorter magnetically connected threads. It is also revealed that the prominence spine deviates from the flux rope axis in the vertical direction and from the photospheric polarity inversion line projected on the solar surface, especially for the weakly-twisted magnetic flux rope. The two types of prominences differ significantly in appearance. It is also suggested that a piling-up of short threads in highly-twisted flux ropes might account for the vertical-like threads in some prominences., Comment: 10 pages, 7 figures, accepted for publication in A&A

On the Sun,jets in light bridges are frequently observed with high-resolution instruments.The respective roles played by convection and the magnetic field in triggering such jets are not yet clear.We report a small fan-shaped jet along a LB observed by the 1.6m Goode Solar Telescope(GST) with the TiO Broadband Filter Imager(BFI),the Visible Imaging Spectrometer(VIS) in H{\alpha},and the Near-InfraRed Imaging Spectropolarimeter(NIRIS),along with the Stokes parameters.The high spatial and temporal resolution of those instruments allowed us to analyze the features identified during the jet event.By constructing the H{\alpha} Dopplergrams,we found that the plasma is first moving upward,whereas during the second phase of the jet,the plasma is flowing back.Working with time slice diagrams,we investigated the propagation-projected speed of the fan and its bright base.The fan-shaped jet developed within a few minutes,with diverging beams. At its base,a bright point was slipping along the LB and ultimately invaded the umbra of the sunspot.The H{\alpha} profiles of the bright points enhanced the intensity in the wings, similarly to the case of Ellerman bombs.Co-temporally,the extreme ultraviolet brightenings developed at the front of the dark material jet and moved at the same speed as the fan, leading us to propose that the fan-shaped jet material compressed and heated the ambient plasma at its extremities in the corona.Our multi-wavelength analysis indicates that the fan-shaped jet could result from magnetic reconnection across the highly diverging field low in the chromosphere,leading to an apparent slipping motion of the jet material along the LB.However,we did not find any opposite magnetic polarity at the jet base,as would typically be expected in such a configuration.We therefore discuss other plausible physical mechanisms,based on waves and convection, that may have triggered the event., Comment: 10 pages, 7 figures

Coronal mass ejections (CMEs) are large scale eruptions observed close to the Sun. They are travelling through the heliosphere and possibly interacting with the Earth environment creating interruptions or even damaging new technology instruments. Most of the time their physical conditions (velocity, density, pressure) are only measured in situ at one point in space, with no possibility to have information on the variation of these parameters during their journey from Sun to Earth. Our aim is to understand the evolution of internal physical parameters of a set of three particular fast halo CMEs. These CMEs were launched between 15 and 18 July 2002. Surprisingly, the related interplanetary CMEs (ICMEs), observed near Earth, have a low, and in one case even very low, plasma density. We use the EUropean Heliosphere FORecasting Information Asset (EUHFORIA) model to simulate the propagation of the CMEs in the background solar wind by placing virtual spacecraft along the Sun--Earth line. We set up the initial conditions at 0.1 au, first with a cone model and then with a linear force free spheromak model. A relatively good agreement between simulation results and observations concerning the speed, density and arrival times of the ICMEs is obtained by adapting the initial CME parameters. In particular, this is achieved by increasing the initial magnetic pressure so that a fast expansion is induced in the inner heliosphere. This implied the develop First, we show that a magnetic configuration with an out of force balance close to the Sun mitigates the EUHFORIA assumptions related to an initial uniform velocity. Second, the over-expansion of the ejected magnetic configuration in the inner heliosphere is one plausible origin for the low density observed in some ICMEs at 1 au. The in situ observed very low density has a possible coronal origin of fast expansion for two of the three ICMEs., Comment: 20 pages