Yeimy J. Rivera, Samuel T. Badman, Michael L. Stevens, Jaye L. Verniero, Julia E. Stawarz, Chen Shi, Jim M. Raines, Kristoff W. Paulson, Christopher J. Owen, Tatiana Niembro, Philippe Louarn, Stefano A. Livi, Susan T. Lepri, Justin C. Kasper, Timothy S. Horbury, Jasper S. Halekas, Ryan M. Dewey, Rossana De Marco, Stuart D. Bale
After leaving the Sun's corona, the solar wind continues to accelerate and cools, but more slowly than expected for a freely expanding adiabatic gas. We use in situ measurements from the Parker Solar Probe and Solar Orbiter spacecrafts to investigate a stream of solar wind as it traverses the inner heliosphere. The observations show heating and acceleration of the the plasma between the outer edge of the corona and near the orbit of Venus, in connection to the presence of large amplitude Alfv'en waves. Alfv'en waves are perturbations in the interplanetary magnetic field that transport energy. Our calculations show the damping and mechanical work performed by the Alfv'en waves is sufficient to power the heating and acceleration of the fast solar wind in the inner heliosphere.
{"title":"In situ observations of large amplitude Alfvén waves heating and accelerating the solar wind","authors":"Yeimy J. Rivera, Samuel T. Badman, Michael L. Stevens, Jaye L. Verniero, Julia E. Stawarz, Chen Shi, Jim M. Raines, Kristoff W. Paulson, Christopher J. Owen, Tatiana Niembro, Philippe Louarn, Stefano A. Livi, Susan T. Lepri, Justin C. Kasper, Timothy S. Horbury, Jasper S. Halekas, Ryan M. Dewey, Rossana De Marco, Stuart D. Bale","doi":"arxiv-2409.00267","DOIUrl":"https://doi.org/arxiv-2409.00267","url":null,"abstract":"After leaving the Sun's corona, the solar wind continues to accelerate and\u0000cools, but more slowly than expected for a freely expanding adiabatic gas. We\u0000use in situ measurements from the Parker Solar Probe and Solar Orbiter\u0000spacecrafts to investigate a stream of solar wind as it traverses the inner\u0000heliosphere. The observations show heating and acceleration of the the plasma\u0000between the outer edge of the corona and near the orbit of Venus, in connection\u0000to the presence of large amplitude Alfv'en waves. Alfv'en waves are\u0000perturbations in the interplanetary magnetic field that transport energy. Our\u0000calculations show the damping and mechanical work performed by the Alfv'en\u0000waves is sufficient to power the heating and acceleration of the fast solar\u0000wind in the inner heliosphere.","PeriodicalId":501423,"journal":{"name":"arXiv - PHYS - Space Physics","volume":"20 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142223602","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}
Xiao-Jia Zhang, Anton V. Artemyev, Xinlin Li, Harry Arnold, Vassilis Angelopoulos, Drew L. Turner, Mykhaylo Shumko, Andrei Runov, Yang Mei, Zheng Xiang
Earth's magnetotail, a night-side region characterized by stretched magnetic field lines and strong plasma currents, is the primary site for the release of magnetic field energy and its transformation into plasma heating and kinetic energy plus charged particle acceleration during magnetic reconnection. In this study, we demonstrate that the efficiency of this acceleration can be sufficiently high to produce populations of relativistic and ultra-relativistic electrons, with energies up to several MeV, which exceeds all previous theoretical and simulation estimates. Using data from the low altitude ELFIN and CIRBE CubeSats, we show multiple events of relativistic electron bursts within the magnetotail, far poleward of the outer radiation belt. These bursts are characterized by power-law energy spectra and can be detected during even moderate substorms.
{"title":"Relativistic and Ultra-Relativistic Electron Bursts in Earth's Magnetotail Observed by Low-Altitude Satellites","authors":"Xiao-Jia Zhang, Anton V. Artemyev, Xinlin Li, Harry Arnold, Vassilis Angelopoulos, Drew L. Turner, Mykhaylo Shumko, Andrei Runov, Yang Mei, Zheng Xiang","doi":"arxiv-2408.17299","DOIUrl":"https://doi.org/arxiv-2408.17299","url":null,"abstract":"Earth's magnetotail, a night-side region characterized by stretched magnetic\u0000field lines and strong plasma currents, is the primary site for the release of\u0000magnetic field energy and its transformation into plasma heating and kinetic\u0000energy plus charged particle acceleration during magnetic reconnection. In this\u0000study, we demonstrate that the efficiency of this acceleration can be\u0000sufficiently high to produce populations of relativistic and ultra-relativistic\u0000electrons, with energies up to several MeV, which exceeds all previous\u0000theoretical and simulation estimates. Using data from the low altitude ELFIN\u0000and CIRBE CubeSats, we show multiple events of relativistic electron bursts\u0000within the magnetotail, far poleward of the outer radiation belt. These bursts\u0000are characterized by power-law energy spectra and can be detected during even\u0000moderate substorms.","PeriodicalId":501423,"journal":{"name":"arXiv - PHYS - Space Physics","volume":"25 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142178426","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}
Harsha Gurram, Jason R. Shuster, Li-Jen Chen, Hiroshi Hasegawa, Richard E. Denton, Brandon L. Burkholder, Jason Beedle, Daniel J. Gershman, James Burch
The magnetic cloud (MC) of the Coronal Mass Ejection on April 24, 2023, contains sub-Alfv'{e}nic solar wind, transforming Earth's magnetosphere from conventional bow-shock magnetotail configuration to Alfv'{e}n wings. Utilizing measurements from the Magnetosphere Multiscale (MMS) mission, we present for the first time electron distribution signatures as the spacecraft traverses through various magnetic topologies during this transformation. Specifically, we characterize electrons inside the sub-Alfv'{e}nic MC, on the dawn-dusk wing field lines and on the closed field lines. The signatures include strahl electrons in MC regions and energetic keV electrons streaming along the dawn and dusk wing field lines. We demonstrate the distribution signatures of dual wing reconnection, defined as reconnection between dawn-dusk Alfv'{e}n wing field lines and the IMF. These signatures include four electron populations comprised of partially-depleted MC electrons and bi-directional energetic electrons with variations in energy and pitch-angle. The distributions reveal evidence of bursty magnetic reconnection under northward IMF.
{"title":"Earth's Alfvén Wings: Unveiling Dynamic Variations of Field-line Topologies with Electron Distributions","authors":"Harsha Gurram, Jason R. Shuster, Li-Jen Chen, Hiroshi Hasegawa, Richard E. Denton, Brandon L. Burkholder, Jason Beedle, Daniel J. Gershman, James Burch","doi":"arxiv-2409.00247","DOIUrl":"https://doi.org/arxiv-2409.00247","url":null,"abstract":"The magnetic cloud (MC) of the Coronal Mass Ejection on April 24, 2023,\u0000contains sub-Alfv'{e}nic solar wind, transforming Earth's magnetosphere from\u0000conventional bow-shock magnetotail configuration to Alfv'{e}n wings. Utilizing\u0000measurements from the Magnetosphere Multiscale (MMS) mission, we present for\u0000the first time electron distribution signatures as the spacecraft traverses\u0000through various magnetic topologies during this transformation. Specifically,\u0000we characterize electrons inside the sub-Alfv'{e}nic MC, on the dawn-dusk wing\u0000field lines and on the closed field lines. The signatures include strahl\u0000electrons in MC regions and energetic keV electrons streaming along the dawn\u0000and dusk wing field lines. We demonstrate the distribution signatures of dual\u0000wing reconnection, defined as reconnection between dawn-dusk Alfv'{e}n wing\u0000field lines and the IMF. These signatures include four electron populations\u0000comprised of partially-depleted MC electrons and bi-directional energetic\u0000electrons with variations in energy and pitch-angle. The distributions reveal\u0000evidence of bursty magnetic reconnection under northward IMF.","PeriodicalId":501423,"journal":{"name":"arXiv - PHYS - Space Physics","volume":"129 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142178411","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}
Charles Constant, Santosh Bhattarai, Indigo Brownhall, Anasuya Aruliah, Marek Ziebart
We present a methodology to generate low-latency, high spatio-temporal resolution thermospheric density estimates using publicly available Low Earth Orbit (LEO) spacecraft ephemerides. This provides a means of generating density estimates that can be used in a data-assimilative context by the satellite operations and thermosphere communities. It also contributes to the data base of high-resolution density estimates during geomagnetic storms -- which remains one of the major gaps for the development and benchmarking of density models. Using accelerometer-derived densities from the Gravity Recovery And Climate Experiment Follow-On (GRACE-FO) spacecraft as truth, our method surpasses Energy Dissipation Rate-Type density retrieval techniques and three widely used operational density models in terms of accuracy: EDR (103.37%), JB2008 (85.43%), DTM2000 (52.73%), and NRLMSISE-00 (12.31%). We demonstrate the robustness of our methodology during a critical time for spacecraft operators -- attempting to operate in the presence of geomagnetic storms, by reconstructing density profiles along the orbits of three LEO satellites during 80 geomagnetic storms. These profiles exhibit high spatial and temporal resolution compared to three operational thermospheric models, highlighting the operational applicability and potential for their use in model validation. Our findings suggest that the increasing availability of precise orbit determination data offers a valuable, yet underutilized, resource that could provide a significant improvement to data assimilative thermospheric models, ultimately enhancing both spacecraft operations and thermospheric modeling efforts.
{"title":"Near-Real Time Thermospheric Density Retrieval from Precise Low Earth Orbit Spacecraft Ephemerides During Geomagnetic Storms","authors":"Charles Constant, Santosh Bhattarai, Indigo Brownhall, Anasuya Aruliah, Marek Ziebart","doi":"arxiv-2408.16805","DOIUrl":"https://doi.org/arxiv-2408.16805","url":null,"abstract":"We present a methodology to generate low-latency, high spatio-temporal\u0000resolution thermospheric density estimates using publicly available Low Earth\u0000Orbit (LEO) spacecraft ephemerides. This provides a means of generating density\u0000estimates that can be used in a data-assimilative context by the satellite\u0000operations and thermosphere communities. It also contributes to the data base\u0000of high-resolution density estimates during geomagnetic storms -- which remains\u0000one of the major gaps for the development and benchmarking of density models.\u0000Using accelerometer-derived densities from the Gravity Recovery And Climate\u0000Experiment Follow-On (GRACE-FO) spacecraft as truth, our method surpasses\u0000Energy Dissipation Rate-Type density retrieval techniques and three widely used\u0000operational density models in terms of accuracy: EDR (103.37%), JB2008\u0000(85.43%), DTM2000 (52.73%), and NRLMSISE-00 (12.31%). We demonstrate the\u0000robustness of our methodology during a critical time for spacecraft operators\u0000-- attempting to operate in the presence of geomagnetic storms, by\u0000reconstructing density profiles along the orbits of three LEO satellites during\u000080 geomagnetic storms. These profiles exhibit high spatial and temporal\u0000resolution compared to three operational thermospheric models, highlighting the\u0000operational applicability and potential for their use in model validation. Our\u0000findings suggest that the increasing availability of precise orbit\u0000determination data offers a valuable, yet underutilized, resource that could\u0000provide a significant improvement to data assimilative thermospheric models,\u0000ultimately enhancing both spacecraft operations and thermospheric modeling\u0000efforts.","PeriodicalId":501423,"journal":{"name":"arXiv - PHYS - Space Physics","volume":"11 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142178427","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 corona is the prototypical example of a low density environment heated to high temperatures by external sources. The plasma cools radiatively, and because it is optically thin to this radiation, it becomes possible to model the density, velocity, and temperature structure of the system by modifying the MHD equations to include energy source terms that approximate the local heating and cooling rates. The solutions can be highly inhomogeneous and even multiphase because the well known linear instability associated with these source terms, thermal instability, leads to a catastrophic heating and cooling of the plasma in the nonlinear regime. Here we show that there is a separate, much simpler instance of catastrophic heating and cooling accompanying these source terms that can rival thermal instability in dynamical importance. The linear stability criterion is the isochoric one identified by Parker (1953), and we demonstrate that cooling functions derived from collisional ionization equilibrium are highly prone to violating this criterion. If catastrophic cooling instability can act locally in global simulations, then it is an alternative mechanism for forming condensations, and due to its nonequilibrium character, it may be relevant to explaining a host of phenomena associated with the production of cooler gas in hot, low density plasmas.
{"title":"Catastrophic cooling in optically thin plasmas","authors":"Tim Waters, Amanda Stricklan","doi":"arxiv-2408.15869","DOIUrl":"https://doi.org/arxiv-2408.15869","url":null,"abstract":"The solar corona is the prototypical example of a low density environment\u0000heated to high temperatures by external sources. The plasma cools radiatively,\u0000and because it is optically thin to this radiation, it becomes possible to\u0000model the density, velocity, and temperature structure of the system by\u0000modifying the MHD equations to include energy source terms that approximate the\u0000local heating and cooling rates. The solutions can be highly inhomogeneous and\u0000even multiphase because the well known linear instability associated with these\u0000source terms, thermal instability, leads to a catastrophic heating and cooling\u0000of the plasma in the nonlinear regime. Here we show that there is a separate,\u0000much simpler instance of catastrophic heating and cooling accompanying these\u0000source terms that can rival thermal instability in dynamical importance. The\u0000linear stability criterion is the isochoric one identified by Parker (1953),\u0000and we demonstrate that cooling functions derived from collisional ionization\u0000equilibrium are highly prone to violating this criterion. If catastrophic\u0000cooling instability can act locally in global simulations, then it is an\u0000alternative mechanism for forming condensations, and due to its nonequilibrium\u0000character, it may be relevant to explaining a host of phenomena associated with\u0000the production of cooler gas in hot, low density plasmas.","PeriodicalId":501423,"journal":{"name":"arXiv - PHYS - Space Physics","volume":"2 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142178429","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 study the dynamics of the solar basin -- the accumulated population of weakly-interacting particles on bound orbits in the Solar System. We focus on particles starting off on Sun-crossing orbits, corresponding to initial conditions of production inside the Sun, and investigate their evolution over the age of the Solar System. A combination of analytic methods, secular perturbation theory, and direct numerical integration of orbits sheds light on the long- and short-term evolution of a population of test particles orbiting the Sun and perturbed by the planets. Our main results are that the effective lifetime of a solar basin at Earth's location is $tau_{rm eff} = 1.20pm 0.09 ,mathrm{Gyr}$, and that there is annual (semi-annual) modulation of the basin density with known phase and amplitude at the fractional level of 6.5% (2.2%). These results have important implications for direct detection searches of solar basin particles, and the strong temporal modulation signature yields a robust discovery channel. Our simulations can also be interpreted in the context of gravitational capture of dark matter in the Solar System, with consequences for any dark-matter phenomenon that may occur below the local escape velocity.
{"title":"Orbital Dynamics of the Solar Basin","authors":"Cara Giovanetti, Robert Lasenby, Ken Van Tilburg","doi":"arxiv-2408.16041","DOIUrl":"https://doi.org/arxiv-2408.16041","url":null,"abstract":"We study the dynamics of the solar basin -- the accumulated population of\u0000weakly-interacting particles on bound orbits in the Solar System. We focus on\u0000particles starting off on Sun-crossing orbits, corresponding to initial\u0000conditions of production inside the Sun, and investigate their evolution over\u0000the age of the Solar System. A combination of analytic methods, secular\u0000perturbation theory, and direct numerical integration of orbits sheds light on\u0000the long- and short-term evolution of a population of test particles orbiting\u0000the Sun and perturbed by the planets. Our main results are that the effective\u0000lifetime of a solar basin at Earth's location is $tau_{rm eff} = 1.20pm 0.09\u0000,mathrm{Gyr}$, and that there is annual (semi-annual) modulation of the basin\u0000density with known phase and amplitude at the fractional level of 6.5% (2.2%).\u0000These results have important implications for direct detection searches of\u0000solar basin particles, and the strong temporal modulation signature yields a\u0000robust discovery channel. Our simulations can also be interpreted in the\u0000context of gravitational capture of dark matter in the Solar System, with\u0000consequences for any dark-matter phenomenon that may occur below the local\u0000escape velocity.","PeriodicalId":501423,"journal":{"name":"arXiv - PHYS - Space Physics","volume":"54 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142178428","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}
Meredith L. Rawls, Constance E. Walker, Michelle Dadighat, Harrison Krantz, Siegfried Eggl, Mike Peel
This Birds-of-a-Feather (BOF) session on 6 November 2023 was organized by leaders and members of SatHub at the International Astronomical Union Centre for the Protection of the Dark and Quiet Sky from Satellite Constellation Interference (IAU CPS). SatHub is dedicated to observations, data analysis, software, and related activities. The session opened with a talk on the current state of affairs with regards to satellite constellation mitigation, with a focus on optical astronomy, and moved to focused discussion around the top-voted topics. These included tools and techniques for forecasting satellite positions and brightnesses as well as streak detection and masking.
{"title":"Quantifying & Mitigating Satellite Constellation Interference with SatHub","authors":"Meredith L. Rawls, Constance E. Walker, Michelle Dadighat, Harrison Krantz, Siegfried Eggl, Mike Peel","doi":"arxiv-2408.15223","DOIUrl":"https://doi.org/arxiv-2408.15223","url":null,"abstract":"This Birds-of-a-Feather (BOF) session on 6 November 2023 was organized by\u0000leaders and members of SatHub at the International Astronomical Union Centre\u0000for the Protection of the Dark and Quiet Sky from Satellite Constellation\u0000Interference (IAU CPS). SatHub is dedicated to observations, data analysis,\u0000software, and related activities. The session opened with a talk on the current\u0000state of affairs with regards to satellite constellation mitigation, with a\u0000focus on optical astronomy, and moved to focused discussion around the\u0000top-voted topics. These included tools and techniques for forecasting satellite\u0000positions and brightnesses as well as streak detection and masking.","PeriodicalId":501423,"journal":{"name":"arXiv - PHYS - Space Physics","volume":"47 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142178431","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}
Rajkumar Hajra, Bruce Tsatnam Tsurutani, Gurbax Singh Lakhina, Quanming Lu, Aimin Du
The recent superstorm of 2024 May 10-11 is the second largest geomagnetic storm in the space age and the only one that has simultaneous interplanetary data (there were no interplanetary data for the 1989 March storm). The May superstorm was characterized by a sudden impulse (SI+) amplitude of +88 nT, followed by a three-step storm main phase development which had a total duration of ~9 hr. The cause of the first storm main phase with a peak SYM-H intensity of -183 nT was a fast forward interplanetary shock (magnetosonic Mach number Mms ~7.2) and an interplanetary sheath with southward interplanetary magnetic field component Bs of ~40 nT. The cause of the second storm main phase with a SYM-H intensity of -354 nT was a deepening of the sheath Bs to ~43 nT. A magnetosonic wave (Mms ~0.6) compressed the sheath to a high magnetic field strength of ~71 nT. Intensified Bs of ~48 nT was the cause of the third and most intense storm main phase with a SYM-H intensity of -518 nT. Three magnetic cloud events with Bs fields of ~25-40 nT occurred in the storm recovery phase, lengthening the recovery to ~2.8 days. At geosynchronous orbit, ~76 keV to ~1.5 MeV electrons exhibited ~1-3 orders of magnitude flux decreases following the shock/sheath impingement onto the magnetosphere. The cosmic ray decreases at Dome C, Antarctica (effective vertical cutoff rigidity <0.01 GV) and Oulu, Finland (rigidity ~0.8 GV) were ~17% and ~11%, respectively relative to quite time values. Strong ionospheric current flows resulted in extreme geomagnetically induced currents of ~30-40 A in the sub-auroral region. The storm period is characterized by strong polar region field-aligned currents, with ~10 times intensification during the main phase, and equatorward expansion down to ~50 deg geomagnetic (altitude-adjusted) latitude.
{"title":"Interplanetary Causes and Impacts of the 2024 May Superstorm on the Geosphere: An Overview","authors":"Rajkumar Hajra, Bruce Tsatnam Tsurutani, Gurbax Singh Lakhina, Quanming Lu, Aimin Du","doi":"arxiv-2408.14799","DOIUrl":"https://doi.org/arxiv-2408.14799","url":null,"abstract":"The recent superstorm of 2024 May 10-11 is the second largest geomagnetic\u0000storm in the space age and the only one that has simultaneous interplanetary\u0000data (there were no interplanetary data for the 1989 March storm). The May\u0000superstorm was characterized by a sudden impulse (SI+) amplitude of +88 nT,\u0000followed by a three-step storm main phase development which had a total\u0000duration of ~9 hr. The cause of the first storm main phase with a peak SYM-H\u0000intensity of -183 nT was a fast forward interplanetary shock (magnetosonic Mach\u0000number Mms ~7.2) and an interplanetary sheath with southward interplanetary\u0000magnetic field component Bs of ~40 nT. The cause of the second storm main phase\u0000with a SYM-H intensity of -354 nT was a deepening of the sheath Bs to ~43 nT. A\u0000magnetosonic wave (Mms ~0.6) compressed the sheath to a high magnetic field\u0000strength of ~71 nT. Intensified Bs of ~48 nT was the cause of the third and\u0000most intense storm main phase with a SYM-H intensity of -518 nT. Three magnetic\u0000cloud events with Bs fields of ~25-40 nT occurred in the storm recovery phase,\u0000lengthening the recovery to ~2.8 days. At geosynchronous orbit, ~76 keV to ~1.5\u0000MeV electrons exhibited ~1-3 orders of magnitude flux decreases following the\u0000shock/sheath impingement onto the magnetosphere. The cosmic ray decreases at\u0000Dome C, Antarctica (effective vertical cutoff rigidity <0.01 GV) and Oulu,\u0000Finland (rigidity ~0.8 GV) were ~17% and ~11%, respectively relative to quite\u0000time values. Strong ionospheric current flows resulted in extreme\u0000geomagnetically induced currents of ~30-40 A in the sub-auroral region. The\u0000storm period is characterized by strong polar region field-aligned currents,\u0000with ~10 times intensification during the main phase, and equatorward expansion\u0000down to ~50 deg geomagnetic (altitude-adjusted) latitude.","PeriodicalId":501423,"journal":{"name":"arXiv - PHYS - Space Physics","volume":"40 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142223604","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}
Coronal mass ejections (CMEs) are complex magnetized plasma structures in which the magnetic field spirals around a central axis, forming what is known as a flux rope (FR). The central FR axis can be oriented at any angle to the ecliptic. Throughout its journey, a CME will encounter interplanetary magnetic field and solar wind which are neither homogeneous nor isotropic. Consequently, CMEs with different orientations will encounter different ambient medium conditions and, thus, the interaction of a CME with its surrounding environment will vary depending on the orientation of its FR axis, among other factors. This study aims to understand the effect of inclination on CME propagation. We performed simulations with the EUHFORIA 3D magnetohydrodynamic model. This study focuses on two CMEs modelled as spheromaks with nearly identical properties, differing only by their inclination. We show the effects of CME orientation on sheath evolution, MHD drag, and non-radial flows by analyzing the model data from a swarm of 81 virtual spacecraft scattered across the inner heliospheric. We have found that the sheath duration increases with radial distance from the Sun and that the rate of increase is greater on the flanks of the CME. Non-radial flows within the studied sheath region appear larger outside the ecliptic plane, indicating a "sliding" of the IMF in the out-of ecliptic plane. We found that the calculated drag parameter does not remain constant with radial distance and that the inclination dependence of the drag parameter can not be resolved with our numerical setup.
{"title":"Probing coronal mass ejections inclination effects with EUHFORIA","authors":"Karmen Martinić, Eleanna Asvestari, Mateja Dumbović, Tobias Rindlisbacher, Manuela Temmer, Bojan Vršnak","doi":"arxiv-2408.14971","DOIUrl":"https://doi.org/arxiv-2408.14971","url":null,"abstract":"Coronal mass ejections (CMEs) are complex magnetized plasma structures in\u0000which the magnetic field spirals around a central axis, forming what is known\u0000as a flux rope (FR). The central FR axis can be oriented at any angle to the\u0000ecliptic. Throughout its journey, a CME will encounter interplanetary magnetic\u0000field and solar wind which are neither homogeneous nor isotropic. Consequently,\u0000CMEs with different orientations will encounter different ambient medium\u0000conditions and, thus, the interaction of a CME with its surrounding environment\u0000will vary depending on the orientation of its FR axis, among other factors.\u0000This study aims to understand the effect of inclination on CME propagation. We\u0000performed simulations with the EUHFORIA 3D magnetohydrodynamic model. This\u0000study focuses on two CMEs modelled as spheromaks with nearly identical\u0000properties, differing only by their inclination. We show the effects of CME\u0000orientation on sheath evolution, MHD drag, and non-radial flows by analyzing\u0000the model data from a swarm of 81 virtual spacecraft scattered across the inner\u0000heliospheric. We have found that the sheath duration increases with radial\u0000distance from the Sun and that the rate of increase is greater on the flanks of\u0000the CME. Non-radial flows within the studied sheath region appear larger\u0000outside the ecliptic plane, indicating a \"sliding\" of the IMF in the out-of\u0000ecliptic plane. We found that the calculated drag parameter does not remain\u0000constant with radial distance and that the inclination dependence of the drag\u0000parameter can not be resolved with our numerical setup.","PeriodicalId":501423,"journal":{"name":"arXiv - PHYS - Space Physics","volume":"390 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142178433","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}
Shuhong Yang, Jie Jiang, Zifan Wang, Yijun Hou, Chunlan Jin, Qiao Song, Yukun Luo, Ting Li, Jun Zhang, Yuzong Zhang, Guiping Zhou, Yuanyong Deng, Jingxiu Wang
The polar magnetic fields of the Sun play an important role in governing solar activity and powering fast solar wind. However, because our view of the Sun is limited in the ecliptic plane, the polar regions remain largely uncharted. Using the high spatial resolution and polarimetric precision vector magnetograms observed by Hinode from 2012 to 2021, we investigate the long-term variation of the magnetic fields in polar caps at different latitudes. The Hinode magnetic measurements show that the polarity reversal processes in the north and south polar caps are non-simultaneous. The variation of the averaged radial magnetic flux density reveals that, in each polar cap, the polarity reversal is completed successively from the 70 degree latitude to the pole, reflecting a poleward magnetic flux migration therein. These results clarify the polar magnetic polarity reversal process at different latitudes.
{"title":"Long-term variation of the solar polar magnetic fields at different latitudes","authors":"Shuhong Yang, Jie Jiang, Zifan Wang, Yijun Hou, Chunlan Jin, Qiao Song, Yukun Luo, Ting Li, Jun Zhang, Yuzong Zhang, Guiping Zhou, Yuanyong Deng, Jingxiu Wang","doi":"arxiv-2408.15168","DOIUrl":"https://doi.org/arxiv-2408.15168","url":null,"abstract":"The polar magnetic fields of the Sun play an important role in governing\u0000solar activity and powering fast solar wind. However, because our view of the\u0000Sun is limited in the ecliptic plane, the polar regions remain largely\u0000uncharted. Using the high spatial resolution and polarimetric precision vector\u0000magnetograms observed by Hinode from 2012 to 2021, we investigate the long-term\u0000variation of the magnetic fields in polar caps at different latitudes. The\u0000Hinode magnetic measurements show that the polarity reversal processes in the\u0000north and south polar caps are non-simultaneous. The variation of the averaged\u0000radial magnetic flux density reveals that, in each polar cap, the polarity\u0000reversal is completed successively from the 70 degree latitude to the pole,\u0000reflecting a poleward magnetic flux migration therein. These results clarify\u0000the polar magnetic polarity reversal process at different latitudes.","PeriodicalId":501423,"journal":{"name":"arXiv - PHYS - Space Physics","volume":"6 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142223605","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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