Samriddhi Sankar Maity, Piyali Chatterjee, Ranadeep Sarkar, Ijas S. Mytheen
Coronal mass ejections (CMEs) are powerful drivers of space weather, with magnetic flux ropes (MFRs) widely regarded as their primary precursors. However, the variation in reconnection flux during the evolution of MFR during CME eruptions remains poorly understood. In this paper, we develop a realistic 3D magneto-hydrodynamic model using which we explore the temporal evolution of reconnection flux during the MFR evolution using both numerical simulations and observational data. Our initial coronal configuration features an isothermal atmosphere and a potential arcade magnetic field beneath which an MFR emerges at the lower boundary. As the MFR rises, we observe significant stretching and compression of the overlying magnetic field beneath it. Magnetic reconnection begins with the gradual formation of a current sheet, eventually culminating with the impulsive expulsion of the flux rope. We analyze the temporal evolution of reconnection fluxes during two successive MFR eruptions while continuously emerging the twisted flux rope through the lower boundary. We also conduct a similar analysis using observational data from the Helioseismic and Magnetic Imager (HMI) and the Atmospheric Imaging Assembly (AIA) for an eruptive event. Comparing our MHD simulation with observational data, we find that reconnection flux play a crucial role in determination of CME speeds. From the onset to the eruption, the reconnection flux shows a strong linear correlation with the velocity. This nearly realistic simulation of a solar eruption provides important insights into the complex dynamics of CME initiation and progression.
{"title":"Evolution of reconnection flux during eruption of magnetic flux ropes","authors":"Samriddhi Sankar Maity, Piyali Chatterjee, Ranadeep Sarkar, Ijas S. Mytheen","doi":"arxiv-2407.18188","DOIUrl":"https://doi.org/arxiv-2407.18188","url":null,"abstract":"Coronal mass ejections (CMEs) are powerful drivers of space weather, with\u0000magnetic flux ropes (MFRs) widely regarded as their primary precursors.\u0000However, the variation in reconnection flux during the evolution of MFR during\u0000CME eruptions remains poorly understood. In this paper, we develop a realistic\u00003D magneto-hydrodynamic model using which we explore the temporal evolution of\u0000reconnection flux during the MFR evolution using both numerical simulations and\u0000observational data. Our initial coronal configuration features an isothermal\u0000atmosphere and a potential arcade magnetic field beneath which an MFR emerges\u0000at the lower boundary. As the MFR rises, we observe significant stretching and\u0000compression of the overlying magnetic field beneath it. Magnetic reconnection\u0000begins with the gradual formation of a current sheet, eventually culminating\u0000with the impulsive expulsion of the flux rope. We analyze the temporal\u0000evolution of reconnection fluxes during two successive MFR eruptions while\u0000continuously emerging the twisted flux rope through the lower boundary. We also\u0000conduct a similar analysis using observational data from the Helioseismic and\u0000Magnetic Imager (HMI) and the Atmospheric Imaging Assembly (AIA) for an\u0000eruptive event. Comparing our MHD simulation with observational data, we find\u0000that reconnection flux play a crucial role in determination of CME speeds. From\u0000the onset to the eruption, the reconnection flux shows a strong linear\u0000correlation with the velocity. This nearly realistic simulation of a solar\u0000eruption provides important insights into the complex dynamics of CME\u0000initiation and progression.","PeriodicalId":501423,"journal":{"name":"arXiv - PHYS - Space Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141782555","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Tinatin Baratashvili, Michaela Brchnelova, Luis Linan, Andrea Lani, Stefaan Poedts
Solar wind modelling has become a crucial area of study due to the increased dependence of modern society on technology, navigation, and power systems. Accurate space weather forecasts can predict upcoming threats to Earth's geospace. In this study, we examine a novel full magnetohydrodynamic (MHD) chain from the Sun to Earth. The goal of this study is to demonstrate the capabilities of the full MHD modelling chain from the Sun to Earth by finalising the implementation of the full MHD coronal model into the COolfluid COroNa UnsTructured (COCONUT) model and coupling it to the MHD heliospheric model Icarus. The resulting coronal model has significant advantages compared to the pre-existing polytropic alternative, as it models a more realistic bi-modal wind, which is crucial for heliospheric studies. In this study, only thermal conduction, radiative losses, and approximated coronal heating function were considered in the energy equation. A realistic specific heat ratio was applied. The output of the coronal model was used to onset the 3D MHD heliospheric model Icarus. A minimum solar activity case was chosen as the first test case for the full MHD model. The numerically simulated data in the corona and the heliosphere were compared to observational products. We present a first attempt to obtain the full MHD chain from the Sun to Earth with COCONUT and Icarus. The coronal model has been upgraded to a full MHD model for a realistic bi-modal solar wind configuration. The approximated heating functions have modelled the wind reasonably well, but simple approximations are not enough to obtain a realistic density-speed balance or realistic features in the low corona and farther, near the outer boundary. The full MHD model was computed in 1.06 h on 180 cores of the Genius cluster of the Vlaams Supercomputing Center, which is only 1.8 times longer than the polytropic simulation.
{"title":"The operationally ready full three-dimensional magnetohydrodynamic (3D MHD) model from the Sun to Earth: COCONUT+Icarus","authors":"Tinatin Baratashvili, Michaela Brchnelova, Luis Linan, Andrea Lani, Stefaan Poedts","doi":"arxiv-2407.17903","DOIUrl":"https://doi.org/arxiv-2407.17903","url":null,"abstract":"Solar wind modelling has become a crucial area of study due to the increased\u0000dependence of modern society on technology, navigation, and power systems.\u0000Accurate space weather forecasts can predict upcoming threats to Earth's\u0000geospace. In this study, we examine a novel full magnetohydrodynamic (MHD)\u0000chain from the Sun to Earth. The goal of this study is to demonstrate the\u0000capabilities of the full MHD modelling chain from the Sun to Earth by\u0000finalising the implementation of the full MHD coronal model into the COolfluid\u0000COroNa UnsTructured (COCONUT) model and coupling it to the MHD heliospheric\u0000model Icarus. The resulting coronal model has significant advantages compared\u0000to the pre-existing polytropic alternative, as it models a more realistic\u0000bi-modal wind, which is crucial for heliospheric studies. In this study, only thermal conduction, radiative losses, and approximated\u0000coronal heating function were considered in the energy equation. A realistic\u0000specific heat ratio was applied. The output of the coronal model was used to\u0000onset the 3D MHD heliospheric model Icarus. A minimum solar activity case was\u0000chosen as the first test case for the full MHD model. The numerically simulated\u0000data in the corona and the heliosphere were compared to observational products.\u0000We present a first attempt to obtain the full MHD chain from the Sun to Earth\u0000with COCONUT and Icarus. The coronal model has been upgraded to a full MHD\u0000model for a realistic bi-modal solar wind configuration. The approximated\u0000heating functions have modelled the wind reasonably well, but simple\u0000approximations are not enough to obtain a realistic density-speed balance or\u0000realistic features in the low corona and farther, near the outer boundary. The\u0000full MHD model was computed in 1.06 h on 180 cores of the Genius cluster of the\u0000Vlaams Supercomputing Center, which is only 1.8 times longer than the\u0000polytropic simulation.","PeriodicalId":501423,"journal":{"name":"arXiv - PHYS - Space Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141782556","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Athanasios Papaioannou, Konstantin Herbst, Tobias Ramm, David Lario, Astrid M. Veronig
Aims. The space radiation environment conditions and the maximum expected coronal mass ejection (CME) speed are being assessed through the investigation of scaling laws between the peak proton flux and fluence of Solar Energetic Particle (SEP) events with the speed of the CMEs. Methods. We utilize a complete catalog of SEP events, covering the last ~25 years of CME observations (i.e. 1997 to 2017). We calculate the peak proton fluxes and integrated event fluences for those events reaching an integral energy of up to E> 100 MeV, covering the period of the last ~25 years of CME observations. For a sample of 38 strong SEP events, we first investigate the statistical relations between the recorded peak proton fluxes (IP) and fluences (FP) at a set of integral energies of E >10 MeV, E>30 MeV, E>60 MeV, and E>100 MeV versus the projected CME speed near the Sun (VCME) obtained by the Solar and Heliospheric Observatory/Large Angle and Spectrometric Coronagraph (SOHO/LASCO). Based on the inferred relations, we further calculate the integrated energy dependence of both IP and FP, assuming that they follow an inverse power-law with respect to energy. By making use of simple physical assumptions, we combine our derived scaling laws to estimate the upper limits for VCME, IP, and FP focusing on two cases of known extreme SEP events that occurred on February 23, 1956 (GLE05) and in AD774/775, respectively. Given physical constraints and assumptions, several options for the upper limit VCME, associated with these events, are investigated. Results. A scaling law relating IP and FP to the CME speed as V^{5}CME for CMEs ranging between ~3400-5400 km/s is consistent with values of FP inferred for the cosmogenic nuclide event of AD774/775. At the same time, the upper CME speed that the current Sun can provide possibly falls within an upper limit of VCME <= 5500 km/s.
{"title":"Revisiting Empirical Solar Energetic Particle Scaling Relations II. Coronal Mass Ejections","authors":"Athanasios Papaioannou, Konstantin Herbst, Tobias Ramm, David Lario, Astrid M. Veronig","doi":"arxiv-2407.16479","DOIUrl":"https://doi.org/arxiv-2407.16479","url":null,"abstract":"Aims. The space radiation environment conditions and the maximum expected\u0000coronal mass ejection (CME) speed are being assessed through the investigation\u0000of scaling laws between the peak proton flux and fluence of Solar Energetic\u0000Particle (SEP) events with the speed of the CMEs. Methods. We utilize a\u0000complete catalog of SEP events, covering the last ~25 years of CME observations\u0000(i.e. 1997 to 2017). We calculate the peak proton fluxes and integrated event\u0000fluences for those events reaching an integral energy of up to E> 100 MeV,\u0000covering the period of the last ~25 years of CME observations. For a sample of\u000038 strong SEP events, we first investigate the statistical relations between\u0000the recorded peak proton fluxes (IP) and fluences (FP) at a set of integral\u0000energies of E >10 MeV, E>30 MeV, E>60 MeV, and E>100 MeV versus the projected\u0000CME speed near the Sun (VCME) obtained by the Solar and Heliospheric\u0000Observatory/Large Angle and Spectrometric Coronagraph (SOHO/LASCO). Based on\u0000the inferred relations, we further calculate the integrated energy dependence\u0000of both IP and FP, assuming that they follow an inverse power-law with respect\u0000to energy. By making use of simple physical assumptions, we combine our derived\u0000scaling laws to estimate the upper limits for VCME, IP, and FP focusing on two\u0000cases of known extreme SEP events that occurred on February 23, 1956 (GLE05)\u0000and in AD774/775, respectively. Given physical constraints and assumptions,\u0000several options for the upper limit VCME, associated with these events, are\u0000investigated. Results. A scaling law relating IP and FP to the CME speed as\u0000V^{5}CME for CMEs ranging between ~3400-5400 km/s is consistent with values of\u0000FP inferred for the cosmogenic nuclide event of AD774/775. At the same time,\u0000the upper CME speed that the current Sun can provide possibly falls within an\u0000upper limit of VCME <= 5500 km/s.","PeriodicalId":501423,"journal":{"name":"arXiv - PHYS - Space Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-07-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141782557","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The clouds have a great impact on Venus's energy budget and climate evolution, but its three-dimensional structure is still not well understood. Here we incorporate a simple Venus cloud physics scheme into a flexible GCM to investigate the three-dimensional cloud spatial variability. Our simulations show good agreement with observations in terms of the vertical profiles of clouds and H2SO4 vapor. H2O vapor is overestimated above the clouds due to efficient transport in the cloud region. The cloud top decreases as latitude increases, qualitatively consistent with Venus Express observations. The underlying mechanism is the combination of H2SO4 chemical production and meridional circulation. The mixing ratios of H2SO4 at 50-60 km and H2O vapors in the main cloud deck basically exhibit maxima around the equator, due to the effect of temperature's control on the saturation vapor mixing ratios of the two species. The cloud mass distribution is subject to both H2SO4 chemical production and dynamical transport and shows a pattern that peaks around the equator in the upper cloud while peaks at mid-high latitudes in the middle cloud. At low latitudes, H2SO4 and H2O vapors, cloud mass loading and acidity show semidiurnal variations at different altitude ranges, which can be validated against future missions. Our model emphasizes the complexity of the Venus climate system and the great need for more observations and simulations to unravel its spatial variability and underlying atmospheric and/or geological processes.
{"title":"Three-Dimensional Venus Cloud Structure Simulated by a General Circulation Model","authors":"Wencheng D. Shao, João M. Mendonça, Longkang Dai","doi":"arxiv-2407.15966","DOIUrl":"https://doi.org/arxiv-2407.15966","url":null,"abstract":"The clouds have a great impact on Venus's energy budget and climate\u0000evolution, but its three-dimensional structure is still not well understood.\u0000Here we incorporate a simple Venus cloud physics scheme into a flexible GCM to\u0000investigate the three-dimensional cloud spatial variability. Our simulations\u0000show good agreement with observations in terms of the vertical profiles of\u0000clouds and H2SO4 vapor. H2O vapor is overestimated above the clouds due to\u0000efficient transport in the cloud region. The cloud top decreases as latitude\u0000increases, qualitatively consistent with Venus Express observations. The\u0000underlying mechanism is the combination of H2SO4 chemical production and\u0000meridional circulation. The mixing ratios of H2SO4 at 50-60 km and H2O vapors\u0000in the main cloud deck basically exhibit maxima around the equator, due to the\u0000effect of temperature's control on the saturation vapor mixing ratios of the\u0000two species. The cloud mass distribution is subject to both H2SO4 chemical\u0000production and dynamical transport and shows a pattern that peaks around the\u0000equator in the upper cloud while peaks at mid-high latitudes in the middle\u0000cloud. At low latitudes, H2SO4 and H2O vapors, cloud mass loading and acidity\u0000show semidiurnal variations at different altitude ranges, which can be\u0000validated against future missions. Our model emphasizes the complexity of the\u0000Venus climate system and the great need for more observations and simulations\u0000to unravel its spatial variability and underlying atmospheric and/or geological\u0000processes.","PeriodicalId":501423,"journal":{"name":"arXiv - PHYS - Space Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-07-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141785981","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The applicability of first-order Fermi acceleration in explaining the cosmic ray spectrum has been reexamined using recent results on shock acceleration mechanisms from the Multiscale Magnetospheric mission in Earth's bow shock. It is demonstrated that the Fermi mechanism is a crude approximation of the ballistic surfing acceleration (BSA) mechanism. While both mechanisms yield similar expressions for the energy gain of a particle after encountering a shock once, leading to similar power-law distributions of the cosmic ray energy spectrum, the Fermi mechanism is found to be inconsistent with fundamental equations of electrodynamics. It is shown that the spectral index of cosmic rays is determined by the average magnetic field compression rather than the density compression, as in the Fermi model. It is shown that the knee observed in the spectrum at an energy of 5x10^{15} eV could correspond to ions with a gyroradius comparable to the size of shocks in supernova remnants. The BSA mechanism can accurately reproduce the observed spectral index s = -2.5 below the knee energy, as well as a steeper spectrum, s = -3, above the knee. The acceleration time up to the knee, as implied by BSA, is on the order of 300 years. First-order Fermi acceleration does not represent a physically valid mechanism and should be replaced by ballistic surfing acceleration in applications or models related to quasi-perpendicular shocks in space. It is noted that BSA, which operates outside of shocks, was previously misattributed to shock drift acceleration (SDA), which operates within shocks.
{"title":"Reinterpretation of the Fermi acceleration of cosmic rays in terms of the ballistic surfing acceleration in supernova shocks","authors":"Krzysztof Stasiewicz","doi":"arxiv-2407.15767","DOIUrl":"https://doi.org/arxiv-2407.15767","url":null,"abstract":"The applicability of first-order Fermi acceleration in explaining the cosmic\u0000ray spectrum has been reexamined using recent results on shock acceleration\u0000mechanisms from the Multiscale Magnetospheric mission in Earth's bow shock. It\u0000is demonstrated that the Fermi mechanism is a crude approximation of the\u0000ballistic surfing acceleration (BSA) mechanism. While both mechanisms yield\u0000similar expressions for the energy gain of a particle after encountering a\u0000shock once, leading to similar power-law distributions of the cosmic ray energy\u0000spectrum, the Fermi mechanism is found to be inconsistent with fundamental\u0000equations of electrodynamics. It is shown that the spectral index of cosmic rays is determined by the\u0000average magnetic field compression rather than the density compression, as in\u0000the Fermi model. It is shown that the knee observed in the spectrum at an\u0000energy of 5x10^{15} eV could correspond to ions with a gyroradius comparable to\u0000the size of shocks in supernova remnants. The BSA mechanism can accurately\u0000reproduce the observed spectral index s = -2.5 below the knee energy, as well\u0000as a steeper spectrum, s = -3, above the knee. The acceleration time up to the\u0000knee, as implied by BSA, is on the order of 300 years. First-order Fermi acceleration does not represent a physically valid\u0000mechanism and should be replaced by ballistic surfing acceleration in\u0000applications or models related to quasi-perpendicular shocks in space. It is\u0000noted that BSA, which operates outside of shocks, was previously misattributed\u0000to shock drift acceleration (SDA), which operates within shocks.","PeriodicalId":501423,"journal":{"name":"arXiv - PHYS - Space Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-07-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141782558","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
It is under debate whether the magnetic field in the solar atmosphere carries neutralized electric currents; particularly, whether a magnetic flux rope (MFR), which is considered the core structure of coronal mass ejections, carries neutralized electric currents. Recently Wang et al. (2023, ApJ, 943, 80) studied magnetic flux and electric current measured at the footpoints of 28 eruptive MFRs from 2010 to 2015. Because of the small sample size, no rigorous statistics has been done. Here, we include 9 more events from 2016 to 2023 and perform a series of nonparametric statistical tests at a significance level of 5%. The tests confirm that there exist no significant differences in magnetic properties between conjugated footpoints of the same MFR, which justifies the method of identifying the MFR footpoints through coronal dimming. The tests demonstrate that there exist no significant differences between MFRs with pre-eruption dimming and those with only post-eruption dimming. However, there is a medium level of association between MFRs carrying substantial net current and those produce pre-eruption dimming, which can be understood by the Lorentz-self force of the current channel. The tests also suggest that in estimating the magnetic twist of MFRs, it is necessary to take into account the spatially inhomogeneous distribution of electric current density and magnetic field.
{"title":"Nonparametric Statistics on Magnetic Properties at the Footpoints of Erupting Magnetic Flux Ropes","authors":"Rui Liu, Wensi Wang","doi":"arxiv-2407.15148","DOIUrl":"https://doi.org/arxiv-2407.15148","url":null,"abstract":"It is under debate whether the magnetic field in the solar atmosphere carries\u0000neutralized electric currents; particularly, whether a magnetic flux rope\u0000(MFR), which is considered the core structure of coronal mass ejections,\u0000carries neutralized electric currents. Recently Wang et al. (2023, ApJ, 943,\u000080) studied magnetic flux and electric current measured at the footpoints of 28\u0000eruptive MFRs from 2010 to 2015. Because of the small sample size, no rigorous\u0000statistics has been done. Here, we include 9 more events from 2016 to 2023 and\u0000perform a series of nonparametric statistical tests at a significance level of\u00005%. The tests confirm that there exist no significant differences in magnetic\u0000properties between conjugated footpoints of the same MFR, which justifies the\u0000method of identifying the MFR footpoints through coronal dimming. The tests\u0000demonstrate that there exist no significant differences between MFRs with\u0000pre-eruption dimming and those with only post-eruption dimming. However, there\u0000is a medium level of association between MFRs carrying substantial net current\u0000and those produce pre-eruption dimming, which can be understood by the\u0000Lorentz-self force of the current channel. The tests also suggest that in\u0000estimating the magnetic twist of MFRs, it is necessary to take into account the\u0000spatially inhomogeneous distribution of electric current density and magnetic\u0000field.","PeriodicalId":501423,"journal":{"name":"arXiv - PHYS - Space Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141782559","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We present a new boundary condition for simulations of magnetic reconnection based on the topology of a Klein bottle. When applicable, the new condition is computationally cheaper than fully periodic boundary conditions, reconnects more flux than systems with conducting boundaries, and does not require assumptions about regions external to the simulation as is necessary for open boundaries. The new condition reproduces the expected features of reconnection, but cannot be straightforwardly applied in systems with asymmetric upstream plasmas.
{"title":"Magnetic Reconnection on a Klein Bottle","authors":"Luke Xia, M. Swisdak","doi":"arxiv-2407.14665","DOIUrl":"https://doi.org/arxiv-2407.14665","url":null,"abstract":"We present a new boundary condition for simulations of magnetic reconnection\u0000based on the topology of a Klein bottle. When applicable, the new condition is\u0000computationally cheaper than fully periodic boundary conditions, reconnects\u0000more flux than systems with conducting boundaries, and does not require\u0000assumptions about regions external to the simulation as is necessary for open\u0000boundaries. The new condition reproduces the expected features of reconnection,\u0000but cannot be straightforwardly applied in systems with asymmetric upstream\u0000plasmas.","PeriodicalId":501423,"journal":{"name":"arXiv - PHYS - Space Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-07-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141785982","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Majedaldein Almahasneh, Adeline Paiement, Xianghua Xie, Jean Aboudarham
Precisely localising solar Active Regions (AR) from multi-spectral images is a challenging but important task in understanding solar activity and its influence on space weather. A main challenge comes from each modality capturing a different location of the 3D objects, as opposed to typical multi-spectral imaging scenarios where all image bands observe the same scene. Thus, we refer to this special multi-spectral scenario as multi-layer. We present a multi-task deep learning framework that exploits the dependencies between image bands to produce 3D AR localisation (segmentation and detection) where different image bands (and physical locations) have their own set of results. Furthermore, to address the difficulty of producing dense AR annotations for training supervised machine learning (ML) algorithms, we adapt a training strategy based on weak labels (i.e. bounding boxes) in a recursive manner. We compare our detection and segmentation stages against baseline approaches for solar image analysis (multi-channel coronal hole detection, SPOCA for ARs) and state-of-the-art deep learning methods (Faster RCNN, U-Net). Additionally, both detection a nd segmentation stages are quantitatively validated on artificially created data of similar spatial configurations made from annotated multi-modal magnetic resonance images. Our framework achieves an average of 0.72 IoU (segmentation) and 0.90 F1 score (detection) across all modalities, comparing to the best performing baseline methods with scores of 0.53 and 0.58, respectively, on the artificial dataset, and 0.84 F1 score in the AR detection task comparing to baseline of 0.82 F1 score. Our segmentation results are qualitatively validated by an expert on real ARs.
从多光谱图像中精确定位太阳活动区（AR）是了解太阳活动及其对空间天气影响的一项具有挑战性但又十分重要的任务。与所有图像波段都观测同一场景的典型多光谱成像场景不同，每种模式捕捉到的三维物体的位置都不同，这是一个主要挑战。因此，我们将这种特殊的多光谱场景称为多层。我们提出了一个多任务深度学习框架，利用图像波段之间的依赖关系来生成三维 AR 定位（分割和检测），其中不同的图像波段（和物理位置）有各自的结果集。此外，为了解决为训练监督机器学习（ML）算法而生成密集 AR 注释的困难，我们以递归方式调整了基于弱标签（即边界框）的训练策略。我们将我们的检测和分割阶段与太阳图像分析的基准方法（多通道冠状孔检测、AR 的 SPOCA）和最先进的深度学习方法（Faster RCNN、U-Net）进行了比较。此外，检测和分割阶段都在人工创建的类似空间配置数据上进行了定量验证，这些数据来自有注释的多模态磁共振图像。我们的框架在所有模式下的平均 IoU（分割）和 F1 分数（检测）分别为 0.72 和 0.90，而在人工数据集上表现最好的基线方法的平均 IoU 和 F1 分数分别为 0.53 和 0.58，在 AR 检测任务中的平均 F1 分数为 0.84，而基线方法的平均 F1 分数为 0.82。我们的分割结果得到了真实 AR 专家的定性验证。
{"title":"MLMT-CNN for Object Detection and Segmentation in Multi-layer and Multi-spectral Images","authors":"Majedaldein Almahasneh, Adeline Paiement, Xianghua Xie, Jean Aboudarham","doi":"arxiv-2407.14473","DOIUrl":"https://doi.org/arxiv-2407.14473","url":null,"abstract":"Precisely localising solar Active Regions (AR) from multi-spectral images is\u0000a challenging but important task in understanding solar activity and its\u0000influence on space weather. A main challenge comes from each modality capturing\u0000a different location of the 3D objects, as opposed to typical multi-spectral\u0000imaging scenarios where all image bands observe the same scene. Thus, we refer\u0000to this special multi-spectral scenario as multi-layer. We present a multi-task\u0000deep learning framework that exploits the dependencies between image bands to\u0000produce 3D AR localisation (segmentation and detection) where different image\u0000bands (and physical locations) have their own set of results. Furthermore, to\u0000address the difficulty of producing dense AR annotations for training\u0000supervised machine learning (ML) algorithms, we adapt a training strategy based\u0000on weak labels (i.e. bounding boxes) in a recursive manner. We compare our\u0000detection and segmentation stages against baseline approaches for solar image\u0000analysis (multi-channel coronal hole detection, SPOCA for ARs) and\u0000state-of-the-art deep learning methods (Faster RCNN, U-Net). Additionally, both\u0000detection a nd segmentation stages are quantitatively validated on artificially\u0000created data of similar spatial configurations made from annotated multi-modal\u0000magnetic resonance images. Our framework achieves an average of 0.72 IoU\u0000(segmentation) and 0.90 F1 score (detection) across all modalities, comparing\u0000to the best performing baseline methods with scores of 0.53 and 0.58,\u0000respectively, on the artificial dataset, and 0.84 F1 score in the AR detection\u0000task comparing to baseline of 0.82 F1 score. Our segmentation results are\u0000qualitatively validated by an expert on real ARs.","PeriodicalId":501423,"journal":{"name":"arXiv - PHYS - Space Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-07-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141738203","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Munkhjargal Lkhagvadorj, Gabor Facsko, Andrea Opitz, Peter Kovacs, David G. Sibeck
Interplanetary shocks are one of the crucial dynamic phenomena in the Heliosphere. They accelerate particles to high energies, generate plasma waves, and can trigger geomagnetic storms in the terrestrial magnetosphere disturbing significantly our technological infrastructures. In this study, two IP shock events are selected to study the temporal variations of the shock parameters using magnetometer and ion plasma measurements of the STEREO$-$A and B, the Wind, Cluster fleet, and the ACE spacecraft. The shock normal vectors are determined using the minimum variance analysis (MVA) and the magnetic coplanarity methods. During the May 7, 2007 event, the shock parameters and the shock normal direction are consistent. The shock surface appears to be tilted almost the same degree as the Parker spiral, and the driver could be a Co--Rotating Interacting Region (CIR). During the April 23, 2007 event, the shock parameters do not change significantly except for the shock $theta_{Bn}$ angle, however, the shape of the IP shock appears to be twisted along the perpendicular direction to the Sun-Earth line as well. The driver of this rippled shock is Stream Interaction Regions (SIRs)/CISs as well.
{"title":"Propagation of Interplanetary Shocks in the Heliosphere","authors":"Munkhjargal Lkhagvadorj, Gabor Facsko, Andrea Opitz, Peter Kovacs, David G. Sibeck","doi":"arxiv-2407.12689","DOIUrl":"https://doi.org/arxiv-2407.12689","url":null,"abstract":"Interplanetary shocks are one of the crucial dynamic phenomena in the\u0000Heliosphere. They accelerate particles to high energies, generate plasma waves,\u0000and can trigger geomagnetic storms in the terrestrial magnetosphere disturbing\u0000significantly our technological infrastructures. In this study, two IP shock\u0000events are selected to study the temporal variations of the shock parameters\u0000using magnetometer and ion plasma measurements of the STEREO$-$A and B, the\u0000Wind, Cluster fleet, and the ACE spacecraft. The shock normal vectors are\u0000determined using the minimum variance analysis (MVA) and the magnetic\u0000coplanarity methods. During the May 7, 2007 event, the shock parameters and the\u0000shock normal direction are consistent. The shock surface appears to be tilted\u0000almost the same degree as the Parker spiral, and the driver could be a\u0000Co--Rotating Interacting Region (CIR). During the April 23, 2007 event, the\u0000shock parameters do not change significantly except for the shock $theta_{Bn}$\u0000angle, however, the shape of the IP shock appears to be twisted along the\u0000perpendicular direction to the Sun-Earth line as well. The driver of this\u0000rippled shock is Stream Interaction Regions (SIRs)/CISs as well.","PeriodicalId":501423,"journal":{"name":"arXiv - PHYS - Space Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141738200","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The results of simulations of magnetic reconnection accompanied by electron and proton heating and energization in a macroscale system are presented. Both species form extended powerlaw distributions that extend nearly three decades in energy. The primary drive mechanism for the production of these nonthermal particles is Fermi reflection within evolving and coalescing magnetic flux ropes. While the powerlaw indices of the two species are comparable, the protons overall gain more energy than electrons and their power law extends to higher energy. The power laws roll into a hot thermal distribution at low energy with the transition energy occurring at lower energy for electrons compared with protons. A strong guide field diminishes the production of non-thermal particles by reducing the Fermi drive mechanism. In solar flares, proton power laws should extend down to 10's of keV, far below the energies that can be directly probed via gamma-ray emission. Thus, protons should carry much more of the released magnetic energy than expected from direct observations.
{"title":"Simultaneous Proton and Electron Energization during Macroscale Magnetic Reconnection","authors":"Zhiyu Yin, James F. Drake, Marc Swisdak","doi":"arxiv-2407.10933","DOIUrl":"https://doi.org/arxiv-2407.10933","url":null,"abstract":"The results of simulations of magnetic reconnection accompanied by electron\u0000and proton heating and energization in a macroscale system are presented. Both\u0000species form extended powerlaw distributions that extend nearly three decades\u0000in energy. The primary drive mechanism for the production of these nonthermal\u0000particles is Fermi reflection within evolving and coalescing magnetic flux\u0000ropes. While the powerlaw indices of the two species are comparable, the\u0000protons overall gain more energy than electrons and their power law extends to\u0000higher energy. The power laws roll into a hot thermal distribution at low\u0000energy with the transition energy occurring at lower energy for electrons\u0000compared with protons. A strong guide field diminishes the production of\u0000non-thermal particles by reducing the Fermi drive mechanism. In solar flares,\u0000proton power laws should extend down to 10's of keV, far below the energies\u0000that can be directly probed via gamma-ray emission. Thus, protons should carry\u0000much more of the released magnetic energy than expected from direct\u0000observations.","PeriodicalId":501423,"journal":{"name":"arXiv - PHYS - Space Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141719568","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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