Paolo Romano, Abouazza Elmhamdi, Alessandro Marassi, Lidia Contarino
Several recurrent X-class flares from Active Region (AR) 13664 have triggered a severe G5-class geomagnetic storm between May 10 and 11, 2024. The morphology and compactness of this AR closely resemble the active region responsible for the famous Carrington Event of 1859. Although the induced geomagnetic currents produced a value of the Dst index, probably, an order of magnitude weaker than that of the Carrington Event, the characteristics of AR 13664 warrant special attention. Understanding the mechanisms of magnetic field emergence and transformation in the solar atmosphere that lead to the formation of such an extensive, compact and complex AR is crucial. Our analysis of the emerging flux and horizontal motions of the magnetic structures observed in the photosphere reveals the fundamental role of a sequence of emerging bipoles at the same latitude and longitude, followed by converging and shear motions. This temporal order of processes frequently invoked in magnetohydrodynamic models - emergence, converging motions, and shear motions - is critical for the storage of magnetic energy preceding strong solar eruptions that, under the right timing, location and direction conditions, can trigger severe space weather events at Earth.
在2024年5月10日和11日之间，来自活动区（AR）13664的几个周期性X级耀斑引发了一场严重的G5级地磁暴。这个活动区的形态和紧凑程度与 1859 年著名的卡灵顿事件的活动区非常相似。虽然诱导地磁流产生的 Dst 指数值可能比卡林顿事件的指数值弱一个数量级，但 AR 13664 的特征值得特别关注。了解太阳大气中磁场出现和转变的机制，从而形成如此广泛、紧凑和复杂的AR，是至关重要的。我们对光层中观测到的新出现的磁通量和磁结构的水平运动的分析表明，在同一纬度和经度出现的一连串双极子，以及随后的会聚和剪切运动起着根本性的作用。磁流体力学模型中经常引用的这一时间顺序过程--出现、会聚运动和剪切运动--对于强太阳爆发前的磁能储存至关重要。
{"title":"Analyzing the Sequence of Phases Leading to the Formation of the Active Region 13664, with Potential Carrington-like Characteristics","authors":"Paolo Romano, Abouazza Elmhamdi, Alessandro Marassi, Lidia Contarino","doi":"arxiv-2409.04408","DOIUrl":"https://doi.org/arxiv-2409.04408","url":null,"abstract":"Several recurrent X-class flares from Active Region (AR) 13664 have triggered\u0000a severe G5-class geomagnetic storm between May 10 and 11, 2024. The morphology\u0000and compactness of this AR closely resemble the active region responsible for\u0000the famous Carrington Event of 1859. Although the induced geomagnetic currents\u0000produced a value of the Dst index, probably, an order of magnitude weaker than\u0000that of the Carrington Event, the characteristics of AR 13664 warrant special\u0000attention. Understanding the mechanisms of magnetic field emergence and\u0000transformation in the solar atmosphere that lead to the formation of such an\u0000extensive, compact and complex AR is crucial. Our analysis of the emerging flux\u0000and horizontal motions of the magnetic structures observed in the photosphere\u0000reveals the fundamental role of a sequence of emerging bipoles at the same\u0000latitude and longitude, followed by converging and shear motions. This temporal\u0000order of processes frequently invoked in magnetohydrodynamic models -\u0000emergence, converging motions, and shear motions - is critical for the storage\u0000of magnetic energy preceding strong solar eruptions that, under the right\u0000timing, location and direction conditions, can trigger severe space weather\u0000events at Earth.","PeriodicalId":501423,"journal":{"name":"arXiv - PHYS - Space Physics","volume":"48 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142178399","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}
Colin Wilkins, Vassilis Angelopoulos, Anton Artemyev, Andrei Runov, Xiao-Jia Zhang, Jiang Liu, Ethan Tsai
Using particle data from the ELFIN satellites, we present a statistical study of 284 proton isotropy boundary events on the nightside magnetosphere, characterizing their occurrence and distribution in local time, latitude (L-shell), energy, and precipitating energy flux, as a function of geomagnetic activity. For a given charged particle species and energy, its isotropy boundary (IB) is the magnetic latitude poleward of which persistently isotropic pitch-angle distributions ($J_{prec}/J_{perp}sim 1$) are first observed to occur. This isotropization is interpreted as resulting from magnetic field-line curvature (FLC) scattering in the equatorial magnetosphere. We find that proton IBs are observed under all observed activity levels, spanning 16 to 05 MLT with $sim$100% occurrence between 19 and 03 MLT, trending toward 60% at dawn/dusk. These results are also compared with electron IB properties observed using ELFIN, where we find similar trends across local time and activity, with the onset in $geq$50 keV proton IB occurring on average 2 L-shells lower, and providing between 3 and 10 times as much precipitating power. Proton IBs typically span $64^circ$-$66^circ$ in magnetic latitude (5-6 in L-shell), corresponding to the outer edge of the ring current, tending toward lower IGRF latitudes as geomagnetic activity increases. The IBs were found to commonly occur 0.3-2.1 Re beyond the plasmapause. Proton IBs typically span $<$50 keV to $sim$1 MeV in energy, maximizing near 22 MLT, and decreasing to a typical upper limit of 300-400 keV toward dawn and dusk, with peak observed isotropic energy increasing by $sim$500 keV during active intervals. These results suggest that FLC in the vicinity of IBs can provide a substantial depletion mechanism for energetic protons, with the total nightside precipitating power from FLC-scattering found to be on the order of 100 MW, at times $geq$10 GW.
{"title":"Statistical Characteristics of the Proton Isotropy Boundary","authors":"Colin Wilkins, Vassilis Angelopoulos, Anton Artemyev, Andrei Runov, Xiao-Jia Zhang, Jiang Liu, Ethan Tsai","doi":"arxiv-2409.04488","DOIUrl":"https://doi.org/arxiv-2409.04488","url":null,"abstract":"Using particle data from the ELFIN satellites, we present a statistical study\u0000of 284 proton isotropy boundary events on the nightside magnetosphere,\u0000characterizing their occurrence and distribution in local time, latitude\u0000(L-shell), energy, and precipitating energy flux, as a function of geomagnetic\u0000activity. For a given charged particle species and energy, its isotropy\u0000boundary (IB) is the magnetic latitude poleward of which persistently isotropic\u0000pitch-angle distributions ($J_{prec}/J_{perp}sim 1$) are first observed to\u0000occur. This isotropization is interpreted as resulting from magnetic field-line\u0000curvature (FLC) scattering in the equatorial magnetosphere. We find that proton\u0000IBs are observed under all observed activity levels, spanning 16 to 05 MLT with\u0000$sim$100% occurrence between 19 and 03 MLT, trending toward 60% at dawn/dusk.\u0000These results are also compared with electron IB properties observed using\u0000ELFIN, where we find similar trends across local time and activity, with the\u0000onset in $geq$50 keV proton IB occurring on average 2 L-shells lower, and\u0000providing between 3 and 10 times as much precipitating power. Proton IBs\u0000typically span $64^circ$-$66^circ$ in magnetic latitude (5-6 in L-shell),\u0000corresponding to the outer edge of the ring current, tending toward lower IGRF\u0000latitudes as geomagnetic activity increases. The IBs were found to commonly\u0000occur 0.3-2.1 Re beyond the plasmapause. Proton IBs typically span $<$50 keV to\u0000$sim$1 MeV in energy, maximizing near 22 MLT, and decreasing to a typical\u0000upper limit of 300-400 keV toward dawn and dusk, with peak observed isotropic\u0000energy increasing by $sim$500 keV during active intervals. These results\u0000suggest that FLC in the vicinity of IBs can provide a substantial depletion\u0000mechanism for energetic protons, with the total nightside precipitating power\u0000from FLC-scattering found to be on the order of 100 MW, at times $geq$10 GW.","PeriodicalId":501423,"journal":{"name":"arXiv - PHYS - Space Physics","volume":"9 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142223598","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}
M. Kozai, Y. Hayashi, K. Fujii, K. Munakata, C. Kato, N. Miyashita, A. Kadokura, R. Kataoka, S. Miyake, M. L. Duldig, J. E. Humble, K. Iwai
The north-south (NS) anisotropy of galactic cosmic rays (GCRs) is dominated by a diamagnetic drift flow of GCRs in the interplanetary magnetic field (IMF), allowing us to derive key parameters of cosmic-ray propagation, such as the density gradient and diffusion coefficient. We propose a new method to analyze the rigidity spectrum of GCR anisotropy and reveal a solar cycle variation of the NS anisotropy's spectrum using ground-based muon detectors in Nagoya, Japan, and Hobart, Australia. The physics-based correction method for the atmospheric temperature effect on muons is used to combine the different-site detectors free from local atmospheric effects. NS channel pairs in the multi-directional muon detectors are formed to enhance sensitivity to the NS anisotropy, and in this process, general graph matching in graph theory is introduced to survey optimized pairs. Moreover, Bayesian estimation with the Gaussian process allows us to unfold the rigidity spectrum without supposing any analytical function for the spectral shape. Thanks to these novel approaches, it has been discovered that the rigidity spectrum of the NS anisotropy is dynamically varying with solar activity every year. It is attributed to a rigidity-dependent variation of the radial density gradient of GCRs based on the nature of the diamagnetic drift in the IMF. The diffusion coefficient and mean-free-path length of GCRs as functions of the rigidity are also derived from the diffusion-convection flow balance. This analysis expands the estimation limit of the mean-free-path length into $le200$ GV rigidity region from $<10$ GV region achieved by solar energetic particle observations.
{"title":"Cosmic ray north-south anisotropy: rigidity spectrum and solar cycle variations observed by ground-based muon detectors","authors":"M. Kozai, Y. Hayashi, K. Fujii, K. Munakata, C. Kato, N. Miyashita, A. Kadokura, R. Kataoka, S. Miyake, M. L. Duldig, J. E. Humble, K. Iwai","doi":"arxiv-2409.03182","DOIUrl":"https://doi.org/arxiv-2409.03182","url":null,"abstract":"The north-south (NS) anisotropy of galactic cosmic rays (GCRs) is dominated\u0000by a diamagnetic drift flow of GCRs in the interplanetary magnetic field (IMF),\u0000allowing us to derive key parameters of cosmic-ray propagation, such as the\u0000density gradient and diffusion coefficient. We propose a new method to analyze\u0000the rigidity spectrum of GCR anisotropy and reveal a solar cycle variation of\u0000the NS anisotropy's spectrum using ground-based muon detectors in Nagoya,\u0000Japan, and Hobart, Australia. The physics-based correction method for the\u0000atmospheric temperature effect on muons is used to combine the different-site\u0000detectors free from local atmospheric effects. NS channel pairs in the\u0000multi-directional muon detectors are formed to enhance sensitivity to the NS\u0000anisotropy, and in this process, general graph matching in graph theory is\u0000introduced to survey optimized pairs. Moreover, Bayesian estimation with the\u0000Gaussian process allows us to unfold the rigidity spectrum without supposing\u0000any analytical function for the spectral shape. Thanks to these novel\u0000approaches, it has been discovered that the rigidity spectrum of the NS\u0000anisotropy is dynamically varying with solar activity every year. It is\u0000attributed to a rigidity-dependent variation of the radial density gradient of\u0000GCRs based on the nature of the diamagnetic drift in the IMF. The diffusion\u0000coefficient and mean-free-path length of GCRs as functions of the rigidity are\u0000also derived from the diffusion-convection flow balance. This analysis expands\u0000the estimation limit of the mean-free-path length into $le200$ GV rigidity\u0000region from $<10$ GV region achieved by solar energetic particle observations.","PeriodicalId":501423,"journal":{"name":"arXiv - PHYS - Space Physics","volume":"108 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142178406","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}
Sushree S Nayak, Samrat Sen, Arpit Kumar Shrivastav, R. Bhattacharyya, P. S. Athiray
Coronal jets are the captivating eruptions which are often found in the solar atmosphere, and primarily formed due to magnetic reconnection. Despite their short-lived nature and lower energy compared to many other eruptive events, e.g. flares and coronal mass ejections, they play an important role in heating the corona and accelerating charged particles. However, their generation in the ambience of non-standard flare regime is not fully understood, and warrant a deeper investigation, in terms of their onset, growth, eruption processes, and thermodynamic evolution. Toward this goal, this paper reports the results of a data-constrained three-dimensional (3D) magnetohydrodynamics (MHD) simulation of an eruptive jet; initialized with a Non-Force-Free-Field (NFFF) extrapolation and carried out in the spirit of Implicit Large Eddy Simulation (ILES). The simulation focuses on the magnetic and dynamical properties of the jet during its onset, and eruption phases, that occurred on February 5, 2015 in an active region NOAA AR12280, associated with a seemingly three-ribbon structure. In order to correlate its thermal evolution with computed energetics, the simulation results are compared with differential emission measurement (DEM) analysis in the vicinity of the jet. Importantly, this combined approach provides an insight to the onset of reconnection in transients in terms of emission and the corresponding electric current profiles from MHD evolutions. The presented study captures the intricate topological dynamics, finds a close correspondence between the magnetic and thermal evolution in and around the jet location. Overall, it enriches the understanding of the thermal evolution due to MHD processes, which is one of the broader aspects to reveal the coronal heating problem.
{"title":"Exploring the magnetic and thermal evolution of a coronal jet","authors":"Sushree S Nayak, Samrat Sen, Arpit Kumar Shrivastav, R. Bhattacharyya, P. S. Athiray","doi":"arxiv-2409.03484","DOIUrl":"https://doi.org/arxiv-2409.03484","url":null,"abstract":"Coronal jets are the captivating eruptions which are often found in the solar\u0000atmosphere, and primarily formed due to magnetic reconnection. Despite their\u0000short-lived nature and lower energy compared to many other eruptive events,\u0000e.g. flares and coronal mass ejections, they play an important role in heating\u0000the corona and accelerating charged particles. However, their generation in the\u0000ambience of non-standard flare regime is not fully understood, and warrant a\u0000deeper investigation, in terms of their onset, growth, eruption processes, and\u0000thermodynamic evolution. Toward this goal, this paper reports the results of a\u0000data-constrained three-dimensional (3D) magnetohydrodynamics (MHD) simulation\u0000of an eruptive jet; initialized with a Non-Force-Free-Field (NFFF)\u0000extrapolation and carried out in the spirit of Implicit Large Eddy Simulation\u0000(ILES). The simulation focuses on the magnetic and dynamical properties of the\u0000jet during its onset, and eruption phases, that occurred on February 5, 2015 in\u0000an active region NOAA AR12280, associated with a seemingly three-ribbon\u0000structure. In order to correlate its thermal evolution with computed\u0000energetics, the simulation results are compared with differential emission\u0000measurement (DEM) analysis in the vicinity of the jet. Importantly, this\u0000combined approach provides an insight to the onset of reconnection in\u0000transients in terms of emission and the corresponding electric current profiles\u0000from MHD evolutions. The presented study captures the intricate topological\u0000dynamics, finds a close correspondence between the magnetic and thermal\u0000evolution in and around the jet location. Overall, it enriches the\u0000understanding of the thermal evolution due to MHD processes, which is one of\u0000the broader aspects to reveal the coronal heating problem.","PeriodicalId":501423,"journal":{"name":"arXiv - PHYS - Space Physics","volume":"11 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142223414","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}
Yeimy J. Rivera, Samuel T. Badman, Michael L. Stevens, Jim M. Raines, Christopher J. Owen, Kristoff Paulson, Tatiana Niembro, Stefano A. Livi, Susan T. Lepri, Enrico Landi, Jasper S. Halekas, Tamar Ervin, Ryan M. Dewey, Jesse T. Coburn, Stuart D. Bale, B. L. Alterman
Since Parker Solar Probe's (Parker's) first perihelion pass at the Sun, large amplitude Alfv'en waves grouped in patches have been observed near the Sun throughout the mission. Several formation processes for these magnetic switchback patches have been suggested with no definitive consensus. To provide insight to their formation, we examine the heavy ion properties of several adjacent magnetic switchback patches around Parker's 11th perihelion pass capitalizing on a spacecraft lineup with Solar Orbiter where each samples the same solar wind streams over a large range of longitudes. Heavy ion properties (Fe/O, C$^{6+}$/C$^{5+}$, O$^{7+}$/O$^{6+}$) related to the wind's coronal origin, measured with Solar Orbiter can be linked to switchback patch structures identified near the Sun with Parker. We find that switchback patches do not contain distinctive ion and elemental compositional signatures different than the surrounding non-switchback solar wind. Both the patches and ambient wind exhibit a range of fast and slow wind qualities, indicating coronal sources with open and closed field lines in close proximity. These observations and modeling indicate switchback patches form in coronal hole boundary wind and with a range of source region magnetic and thermal properties. Furthermore, the heavy ion signatures suggest interchange reconnection and/or shear driven processes may play a role in their creation.
{"title":"Mixed Source Region Signatures Inside Magnetic Switchback Patches Inferred by Heavy Ion Diagnostics","authors":"Yeimy J. Rivera, Samuel T. Badman, Michael L. Stevens, Jim M. Raines, Christopher J. Owen, Kristoff Paulson, Tatiana Niembro, Stefano A. Livi, Susan T. Lepri, Enrico Landi, Jasper S. Halekas, Tamar Ervin, Ryan M. Dewey, Jesse T. Coburn, Stuart D. Bale, B. L. Alterman","doi":"arxiv-2409.03645","DOIUrl":"https://doi.org/arxiv-2409.03645","url":null,"abstract":"Since Parker Solar Probe's (Parker's) first perihelion pass at the Sun, large\u0000amplitude Alfv'en waves grouped in patches have been observed near the Sun\u0000throughout the mission. Several formation processes for these magnetic\u0000switchback patches have been suggested with no definitive consensus. To provide\u0000insight to their formation, we examine the heavy ion properties of several\u0000adjacent magnetic switchback patches around Parker's 11th perihelion pass\u0000capitalizing on a spacecraft lineup with Solar Orbiter where each samples the\u0000same solar wind streams over a large range of longitudes. Heavy ion properties\u0000(Fe/O, C$^{6+}$/C$^{5+}$, O$^{7+}$/O$^{6+}$) related to the wind's coronal\u0000origin, measured with Solar Orbiter can be linked to switchback patch\u0000structures identified near the Sun with Parker. We find that switchback patches\u0000do not contain distinctive ion and elemental compositional signatures different\u0000than the surrounding non-switchback solar wind. Both the patches and ambient\u0000wind exhibit a range of fast and slow wind qualities, indicating coronal\u0000sources with open and closed field lines in close proximity. These observations\u0000and modeling indicate switchback patches form in coronal hole boundary wind and\u0000with a range of source region magnetic and thermal properties. Furthermore, the\u0000heavy ion signatures suggest interchange reconnection and/or shear driven\u0000processes may play a role in their creation.","PeriodicalId":501423,"journal":{"name":"arXiv - PHYS - Space Physics","volume":"26 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142223599","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}
Laura Jade Millson, Anne-Marie Broomhall, Tishtrya Mehta
At high frequencies beyond the acoustic cut-off, a peak-like structure is visible in the solar power spectrum. Known as the pseudo-modes, their frequencies have been shown to vary in anti-phase with solar magnetic activity. In this work, we determined temporal variations in these frequencies across the solar disc, with the aim of identifying any potential latitudinal dependence of pseudo-mode frequency shifts. We utilised nearly 22 years of spatially resolved GONG data for all azimuthal orders, $textit{m}$, for harmonic degrees 0 $leq$ $textit{l}$ $leq$ 200, and determined shifts using the resampled periodogram method. Periodogram realisations were created from overlapping, successive 216d-long segments in time, and cropped to 5600-6800$mu$Hz. Cross-correlation functions were then repeatedly generated between these realisations to identify any variation in frequency and the uncertainty. We categorised each mode by its latitudinal sensitivity and used this categorisation to produce average frequency shifts for different latitude bands (15$^circ$ and 5$^circ$ in size) which were compared to magnetic proxies, the $F_{mathrm{10.7}}$ index and GONG synoptic maps. Morphological differences in the pseudo-mode shifts between different latitudes were found, which were most pronounced during the rise to solar maximum where shifts reach their minimum values. At all latitudes, shift behaviour was strongly in anti-correlation with the activity proxy. Additionally, periodicities shorter than the 11-year cycle were observed. Wavelet analysis was used to identify a periodicity of four years at all latitudes.
{"title":"Latitudinal dependence of variations in the frequencies of solar oscillations above the acoustic cut-off","authors":"Laura Jade Millson, Anne-Marie Broomhall, Tishtrya Mehta","doi":"arxiv-2409.03574","DOIUrl":"https://doi.org/arxiv-2409.03574","url":null,"abstract":"At high frequencies beyond the acoustic cut-off, a peak-like structure is\u0000visible in the solar power spectrum. Known as the pseudo-modes, their\u0000frequencies have been shown to vary in anti-phase with solar magnetic activity.\u0000In this work, we determined temporal variations in these frequencies across the\u0000solar disc, with the aim of identifying any potential latitudinal dependence of\u0000pseudo-mode frequency shifts. We utilised nearly 22 years of spatially resolved\u0000GONG data for all azimuthal orders, $textit{m}$, for harmonic degrees 0 $leq$\u0000$textit{l}$ $leq$ 200, and determined shifts using the resampled periodogram\u0000method. Periodogram realisations were created from overlapping, successive\u0000216d-long segments in time, and cropped to 5600-6800$mu$Hz. Cross-correlation\u0000functions were then repeatedly generated between these realisations to identify\u0000any variation in frequency and the uncertainty. We categorised each mode by its\u0000latitudinal sensitivity and used this categorisation to produce average\u0000frequency shifts for different latitude bands (15$^circ$ and 5$^circ$ in\u0000size) which were compared to magnetic proxies, the $F_{mathrm{10.7}}$ index\u0000and GONG synoptic maps. Morphological differences in the pseudo-mode shifts\u0000between different latitudes were found, which were most pronounced during the\u0000rise to solar maximum where shifts reach their minimum values. At all\u0000latitudes, shift behaviour was strongly in anti-correlation with the activity\u0000proxy. Additionally, periodicities shorter than the 11-year cycle were\u0000observed. Wavelet analysis was used to identify a periodicity of four years at\u0000all latitudes.","PeriodicalId":501423,"journal":{"name":"arXiv - PHYS - Space Physics","volume":"59 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142178403","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}
Ao Guo, Quanming Lu, San Lu, Zhongwei Yang, Xinliang Gao
Shock drift acceleration plays an important role in generating high-energy electrons at quasi-perpendicular shocks, but its efficiency in low beta plasmas is questionable. In this article, we perform a two-dimensional particle-in-cell simulation of a low-Mach-number low-plasma-beta quasi-perpendicular shock, and find that the electron cyclotron drift instability is unstable at the leading edge of the shock foot, which is excited by the relative drift between the shock-reflected ions and the incident electrons. The electrostatic waves triggered by the electron cyclotron drift instability can scatter and heat the incident electrons, which facilitates them to escape from the shock's loss cone. These electrons are then reflected by the shock and energized by shock drift acceleration. In this way, the acceleration efficiency of shock drift acceleration at low-plasma-beta quasi-perpendicular shocks is highly enhanced.
{"title":"Electron shock drift acceleration at a low-Mach-number, low-plasma-beta quasi-perpendicular shock","authors":"Ao Guo, Quanming Lu, San Lu, Zhongwei Yang, Xinliang Gao","doi":"arxiv-2409.03174","DOIUrl":"https://doi.org/arxiv-2409.03174","url":null,"abstract":"Shock drift acceleration plays an important role in generating high-energy\u0000electrons at quasi-perpendicular shocks, but its efficiency in low beta plasmas\u0000is questionable. In this article, we perform a two-dimensional particle-in-cell\u0000simulation of a low-Mach-number low-plasma-beta quasi-perpendicular shock, and\u0000find that the electron cyclotron drift instability is unstable at the leading\u0000edge of the shock foot, which is excited by the relative drift between the\u0000shock-reflected ions and the incident electrons. The electrostatic waves\u0000triggered by the electron cyclotron drift instability can scatter and heat the\u0000incident electrons, which facilitates them to escape from the shock's loss\u0000cone. These electrons are then reflected by the shock and energized by shock\u0000drift acceleration. In this way, the acceleration efficiency of shock drift\u0000acceleration at low-plasma-beta quasi-perpendicular shocks is highly enhanced.","PeriodicalId":501423,"journal":{"name":"arXiv - PHYS - Space Physics","volume":"18 780 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142178401","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 solar wind is highly turbulent, and intermittency effects are observed for fluctuations within the inertial range. By analyzing magnetic field spectra and fourth-order moments, we perform a comparative study of intermittency in different types of solar wind measured during periods of solar minima and a maximum. Using eight fast solar wind intervals measured during solar minima between 0.3 au and 3.16 au, we found a clear signature of two inertial sub-ranges with $f^{-3/2}$ and $f^{-5/3}$ power laws in the magnetic power spectra. The intermittency, measured through the scaling law of the kurtosis of magnetic field fluctuations, further confirms the existence of two different power laws separated by a clear break. A systematic study on the evolution of the said sub-ranges as a function of heliospheric distance shows correlation of the break scale with both the turbulence outer scale and the typical ion scales. During solar maximum, we analyzed five intervals for each of Alfv'enic fast, Alfv'enic slow and non-Alfv'enic slow solar wind. Unlike the case during the solar minima, the two sub-ranges are no longer prominent and the Alfv'enic slow wind is found to be in an intermediate state of turbulence compared to that of the fast wind and the usual non-Alfv'enic slow wind.
{"title":"Emergence of two inertial sub-ranges in solar wind turbulence: dependence on heliospheric distance and solar activity","authors":"Shiladittya Mondal, Supratik Banerjee, Luca Sorriso-Valvo","doi":"arxiv-2409.03090","DOIUrl":"https://doi.org/arxiv-2409.03090","url":null,"abstract":"The solar wind is highly turbulent, and intermittency effects are observed\u0000for fluctuations within the inertial range. By analyzing magnetic field spectra\u0000and fourth-order moments, we perform a comparative study of intermittency in\u0000different types of solar wind measured during periods of solar minima and a\u0000maximum. Using eight fast solar wind intervals measured during solar minima\u0000between 0.3 au and 3.16 au, we found a clear signature of two inertial\u0000sub-ranges with $f^{-3/2}$ and $f^{-5/3}$ power laws in the magnetic power\u0000spectra. The intermittency, measured through the scaling law of the kurtosis of\u0000magnetic field fluctuations, further confirms the existence of two different\u0000power laws separated by a clear break. A systematic study on the evolution of\u0000the said sub-ranges as a function of heliospheric distance shows correlation of\u0000the break scale with both the turbulence outer scale and the typical ion\u0000scales. During solar maximum, we analyzed five intervals for each of Alfv'enic\u0000fast, Alfv'enic slow and non-Alfv'enic slow solar wind. Unlike the case\u0000during the solar minima, the two sub-ranges are no longer prominent and the\u0000Alfv'enic slow wind is found to be in an intermediate state of turbulence\u0000compared to that of the fast wind and the usual non-Alfv'enic slow wind.","PeriodicalId":501423,"journal":{"name":"arXiv - PHYS - Space Physics","volume":"16 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142178400","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}
Context. Simulating solar flares, which involve large-scale dynamics and small-scale magnetic reconnection, poses significant computational challenges. Aims. This study aims to develop an explicit Particle-In-Cell (PIC) solver within the DISPATCH framework to model the small-scale kinetic processes in solar corona setting. This study in the first in a series with the ultimate goal to develop a hybrid PIC-MHD solver, to simulate solar flares. Methods. The PIC solver, inspired by the PhotonPlasma code, solves the Vlasov-Maxwell equations in a collisionless regime using explicit time-staggering and spatial-staggering techniques. Validation included unit tests, plasma frequency recovery, two-stream instability, and current sheet dynamics. Results. Validation tests confirmed the solver's accuracy and robustness in modeling plasma dynamics and electromagnetic fields. Conclusions. The integration of the explicit PIC solver into the DISPATCH framework is the first step towards bridging the gap between large and small scale dynamics, providing a robust platform for future solar physics research.
{"title":"Toward Realistic Solar Flare Models: An explicit Particle-In-Cell solver in the DISPATCH framework","authors":"Michael Haahr, Boris V. Gudiksen, Åke Nordlund","doi":"arxiv-2409.02493","DOIUrl":"https://doi.org/arxiv-2409.02493","url":null,"abstract":"Context. Simulating solar flares, which involve large-scale dynamics and\u0000small-scale magnetic reconnection, poses significant computational challenges.\u0000Aims. This study aims to develop an explicit Particle-In-Cell (PIC) solver\u0000within the DISPATCH framework to model the small-scale kinetic processes in\u0000solar corona setting. This study in the first in a series with the ultimate\u0000goal to develop a hybrid PIC-MHD solver, to simulate solar flares. Methods. The\u0000PIC solver, inspired by the PhotonPlasma code, solves the Vlasov-Maxwell\u0000equations in a collisionless regime using explicit time-staggering and\u0000spatial-staggering techniques. Validation included unit tests, plasma frequency\u0000recovery, two-stream instability, and current sheet dynamics. Results.\u0000Validation tests confirmed the solver's accuracy and robustness in modeling\u0000plasma dynamics and electromagnetic fields. Conclusions. The integration of the\u0000explicit PIC solver into the DISPATCH framework is the first step towards\u0000bridging the gap between large and small scale dynamics, providing a robust\u0000platform for future solar physics research.","PeriodicalId":501423,"journal":{"name":"arXiv - PHYS - Space Physics","volume":"17 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142178413","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}
David Ruffolo, Panisara Thepthong, Peera Pongkitiwanichakul, Sohom Roy, Francesco Pecora, Riddhi Bandyopadhyay, Rohit Chhiber, Arcadi V. Usmanov, Michael Stevens, Samuel Badman, Orlando Romeo, Jiaming Wang, Joshua Goodwill, Melvyn L. Goldstein, William H. Matthaeus
Using Parker Solar Probe data from orbits 8 through 17, we examine fluctuation amplitudes throughout the critical region where the solar wind flow speed approaches and then exceeds the Alfv'en wave speed, taking account of various exigencies of the plasma data. In contrast to WKB theory for non-interacting Alfv'en waves streaming away from the Sun, the magnetic and kinetic fluctuation energies per unit volume are not monotonically decreasing. Instead, there is clear violation of conservation of standard WKB wave action, which is consistent with previous indications of strong in-situ fluctuation energy input in the solar wind near the Alfv'en critical region. This points to strong violations of WKB theory due to nonlinearity (turbulence) and major energy input near the critical region, which we interpret as likely due to driving by large-scale coronal shear flows.
{"title":"Observed Fluctuation Enhancement and Departure from WKB Theory in Sub-Alfvénic Solar Wind","authors":"David Ruffolo, Panisara Thepthong, Peera Pongkitiwanichakul, Sohom Roy, Francesco Pecora, Riddhi Bandyopadhyay, Rohit Chhiber, Arcadi V. Usmanov, Michael Stevens, Samuel Badman, Orlando Romeo, Jiaming Wang, Joshua Goodwill, Melvyn L. Goldstein, William H. Matthaeus","doi":"arxiv-2409.02612","DOIUrl":"https://doi.org/arxiv-2409.02612","url":null,"abstract":"Using Parker Solar Probe data from orbits 8 through 17, we examine\u0000fluctuation amplitudes throughout the critical region where the solar wind flow\u0000speed approaches and then exceeds the Alfv'en wave speed, taking account of\u0000various exigencies of the plasma data. In contrast to WKB theory for\u0000non-interacting Alfv'en waves streaming away from the Sun, the magnetic and\u0000kinetic fluctuation energies per unit volume are not monotonically decreasing.\u0000Instead, there is clear violation of conservation of standard WKB wave action,\u0000which is consistent with previous indications of strong in-situ fluctuation\u0000energy input in the solar wind near the Alfv'en critical region. This points\u0000to strong violations of WKB theory due to nonlinearity (turbulence) and major\u0000energy input near the critical region, which we interpret as likely due to\u0000driving by large-scale coronal shear flows.","PeriodicalId":501423,"journal":{"name":"arXiv - PHYS - Space Physics","volume":"25 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142178404","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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