Christopher W. Hamilton, Alfred S. McEwen, Laszlo Keszthelyi, Lynn M. Carter, Ashley G. Davies, Katherine de Kleer, Kandis Lea Jessup, Xianzhe Jia, James T. Keane, Kathleen Mandt, Francis Nimmo, Chris Paranicas, Ryan S. Park, Jason E. Perry, Anne Pommier, Jani Radebaugh, Sarah S. Sutton, Audrey Vorburger, Peter Wurz, Cauê Borlina, Amanda F. Haapala, Daniella N. DellaGiustina, Brett W. Denevi, Sarah M. Hörst, Sascha Kempf, Krishan K. Khurana, Justin J. Likar, Adam Masters, Olivier Mousis, Anjani T. Polit, Aditya Bhushan, Michael Bland, Isamu Matsuyama, John Spencer
Jupiter's moon Io is a highly compelling target for future exploration that offers critical insight into tidal dissipation processes and the geology of high heat flux worlds, including primitive planetary bodies, such as the early Earth, that are shaped by enhanced rates of volcanism. Io is also important for understanding the development of volcanogenic atmospheres and mass-exchange within the Jupiter System. However, fundamental questions remain about the state of Io's interior, surface, and atmosphere, as well as its role in the evolution of the Galilean satellites. The Io Volcano Observer (IVO) would address these questions by achieving the following three key goals: (A) Determine how and where tidal heat is generated inside Io; (B) Understand how tidal heat is transported to the surface of Io; and (C) Understand how Io is evolving. IVO was selected for Phase A study through the NASA Discovery program in 2020 and, in anticipation of a New Frontiers 5 opportunity, an enhanced IVO-NF mission concept was advanced that would increase the Baseline mission from 10 flybys to 20, with an improved radiation design; employ a Ka-band communications to double IVO's total data downlink; add a wide angle camera for color and stereo mapping; add a dust mass spectrometer; and lower the altitude of later flybys to enable new science. This study compares and contrasts the mission architecture, instrument suite, and science objectives for Discovery (IVO) and New Frontiers (IVO-NF) missions to Io, and advocates for continued prioritization of Io as an exploration target for New Frontiers.
木星的卫星木卫一是一个极具吸引力的未来探索目标，它提供了对潮汐消散过程和高热通量世界（包括原始行星体，如早期地球）地质学的重要洞察力，这些世界是由更高的火山爆发率形成的。木卫一对于了解木星系统内火山生成大气和质量变化的发展也很重要。然而，关于木卫二内部、表面和大气层的状况，以及它在伽利略卫星演变过程中的作用等基本问题仍然存在。木卫二火山观测器（IVO）将通过实现以下三个关键目标来解决这些问题：(A) 确定木卫二内部潮汐热是如何以及在何处产生的；(B) 了解潮汐热是如何传送到木卫二表面的；以及 (C) 了解木卫二是如何演变的。2020 年，IVO 被选为美国航天局发现计划的 A 阶段研究对象，由于预期会有 "新前沿 5 "的机会，因此提出了增强型 IVO-NF 任务概念，将基线任务从 10 次飞越增加到 20 次，并改进辐射设计；采用 Ka 波段通信，将 IVO 的总数据下行链路增加一倍；增加一个广角相机，用于色彩和立体绘图；增加一个尘埃质谱仪；降低以后飞越的高度，以实现新的科学研究。本研究比较和对比了飞往木卫一的 "发现 "号（IVO）和 "新疆域 "号（IVO-NF）任务的发射结构、仪器套件和科学目标，并主张继续优先将木卫一作为 "新疆域 "号的探测目标。
{"title":"Comparing NASA Discovery and New Frontiers Class Mission Concepts for the Io Volcano Observer (IVO)","authors":"Christopher W. Hamilton, Alfred S. McEwen, Laszlo Keszthelyi, Lynn M. Carter, Ashley G. Davies, Katherine de Kleer, Kandis Lea Jessup, Xianzhe Jia, James T. Keane, Kathleen Mandt, Francis Nimmo, Chris Paranicas, Ryan S. Park, Jason E. Perry, Anne Pommier, Jani Radebaugh, Sarah S. Sutton, Audrey Vorburger, Peter Wurz, Cauê Borlina, Amanda F. Haapala, Daniella N. DellaGiustina, Brett W. Denevi, Sarah M. Hörst, Sascha Kempf, Krishan K. Khurana, Justin J. Likar, Adam Masters, Olivier Mousis, Anjani T. Polit, Aditya Bhushan, Michael Bland, Isamu Matsuyama, John Spencer","doi":"arxiv-2408.08334","DOIUrl":"https://doi.org/arxiv-2408.08334","url":null,"abstract":"Jupiter's moon Io is a highly compelling target for future exploration that\u0000offers critical insight into tidal dissipation processes and the geology of\u0000high heat flux worlds, including primitive planetary bodies, such as the early\u0000Earth, that are shaped by enhanced rates of volcanism. Io is also important for\u0000understanding the development of volcanogenic atmospheres and mass-exchange\u0000within the Jupiter System. However, fundamental questions remain about the\u0000state of Io's interior, surface, and atmosphere, as well as its role in the\u0000evolution of the Galilean satellites. The Io Volcano Observer (IVO) would\u0000address these questions by achieving the following three key goals: (A)\u0000Determine how and where tidal heat is generated inside Io; (B) Understand how\u0000tidal heat is transported to the surface of Io; and (C) Understand how Io is\u0000evolving. IVO was selected for Phase A study through the NASA Discovery program\u0000in 2020 and, in anticipation of a New Frontiers 5 opportunity, an enhanced\u0000IVO-NF mission concept was advanced that would increase the Baseline mission\u0000from 10 flybys to 20, with an improved radiation design; employ a Ka-band\u0000communications to double IVO's total data downlink; add a wide angle camera for\u0000color and stereo mapping; add a dust mass spectrometer; and lower the altitude\u0000of later flybys to enable new science. This study compares and contrasts the\u0000mission architecture, instrument suite, and science objectives for Discovery\u0000(IVO) and New Frontiers (IVO-NF) missions to Io, and advocates for continued\u0000prioritization of Io as an exploration target for New Frontiers.","PeriodicalId":501423,"journal":{"name":"arXiv - PHYS - Space Physics","volume":"205 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142223607","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}
Super-Alfv'enic jets, with kinetic energy densities significantly exceeding that of the solar wind, are commonly generated downstream of Earth's bow shock under both high and low beta plasma conditions. In this study, we present theoretical evidence that these enhanced kinetic energy flows are driven by firehose-unstable fluctuations and compressive heating within collisionless plasma environments. Using a fluid formalism that incorporates pressure anisotropy, we estimate that the downstream flow of a collisionless plasma shock can be accelerated by a factor of 2 to 4 following the compression and saturation of firehose instability. By analyzing quasi-parallel magnetosheath jets observed in situ by the Magnetospheric Multiscale (MMS) mission, we find that approximately 11% of plasma measurements within these jets exhibit firehose-unstable fluctuations. Our findings offer an explanation for the distinctive generation of fast downstream flows in both low ($beta<1$) and high ($beta>1$) beta plasmas, and provide new evidence that kinetic processes are crucial for accurately describing the formation and evolution of magnetosheath jets.
{"title":"On the Formation of Super-Alfvénic Flows Downstream of Collisionless Shocks","authors":"Adnane Osmane, Savvas Raptis","doi":"arxiv-2408.08159","DOIUrl":"https://doi.org/arxiv-2408.08159","url":null,"abstract":"Super-Alfv'enic jets, with kinetic energy densities significantly exceeding\u0000that of the solar wind, are commonly generated downstream of Earth's bow shock\u0000under both high and low beta plasma conditions. In this study, we present\u0000theoretical evidence that these enhanced kinetic energy flows are driven by\u0000firehose-unstable fluctuations and compressive heating within collisionless\u0000plasma environments. Using a fluid formalism that incorporates pressure\u0000anisotropy, we estimate that the downstream flow of a collisionless plasma\u0000shock can be accelerated by a factor of 2 to 4 following the compression and\u0000saturation of firehose instability. By analyzing quasi-parallel magnetosheath\u0000jets observed in situ by the Magnetospheric Multiscale (MMS) mission, we find\u0000that approximately 11% of plasma measurements within these jets exhibit\u0000firehose-unstable fluctuations. Our findings offer an explanation for the\u0000distinctive generation of fast downstream flows in both low ($beta<1$) and\u0000high ($beta>1$) beta plasmas, and provide new evidence that kinetic processes\u0000are crucial for accurately describing the formation and evolution of\u0000magnetosheath jets.","PeriodicalId":501423,"journal":{"name":"arXiv - PHYS - Space Physics","volume":"2 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142178440","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}
Solar winds originate from the Sun and can be classified as fast or slow. Fast solar winds come from coronal holes at the solar poles, while slow solar winds may originate from the equatorial region or streamers. Spicules are jet-like structures observed in the Sun's chromosphere and transition region. Some spicules exhibit rotating motion, potentially indicating vorticity and Alfven waves. Machine learning and the Hough algorithm were used to analyze over 3000 frames of the Sun, identifying spicules and their characteristics. The study found that rotating spicules, accounting for 21 percent at the poles and 4 percent at the equator, play a role in energy transfer to the upper solar atmosphere. The observations suggest connections between spicules, mini-loops, magnetic reconnection, and the acceleration of fast solar winds. Understanding these small-scale structures is crucial for comprehending the origin and heating of the fast solar wind.
{"title":"Characterizing Solar Spicules and their Role in Solar Wind Production using Machine Learning and the Hough Transform","authors":"R. Sadeghi, E. Tavabi","doi":"arxiv-2408.07168","DOIUrl":"https://doi.org/arxiv-2408.07168","url":null,"abstract":"Solar winds originate from the Sun and can be classified as fast or slow.\u0000Fast solar winds come from coronal holes at the solar poles, while slow solar\u0000winds may originate from the equatorial region or streamers. Spicules are\u0000jet-like structures observed in the Sun's chromosphere and transition region.\u0000Some spicules exhibit rotating motion, potentially indicating vorticity and\u0000Alfven waves. Machine learning and the Hough algorithm were used to analyze\u0000over 3000 frames of the Sun, identifying spicules and their characteristics.\u0000The study found that rotating spicules, accounting for 21 percent at the poles\u0000and 4 percent at the equator, play a role in energy transfer to the upper solar\u0000atmosphere. The observations suggest connections between spicules, mini-loops,\u0000magnetic reconnection, and the acceleration of fast solar winds. Understanding\u0000these small-scale structures is crucial for comprehending the origin and\u0000heating of the fast solar wind.","PeriodicalId":501423,"journal":{"name":"arXiv - PHYS - Space Physics","volume":"80 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142178441","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}
Distribution functions of collisionless systems are known to show non-thermal power law tails. Interestingly, collisionless plasmas in various physical scenarios, (e.g., the ion population of the solar wind) feature a $v^{-5}$ tail in the velocity ($v$) distribution, whose origin has been a long-standing mystery. We show this power law tail to be a natural outcome of the self-consistent collisionless relaxation of driven electrostatic plasmas. We perform a quasilinear analysis of the perturbed Vlasov-Poisson equations to show that the coarse-grained mean distribution function (DF), $f_0$, follows a quasilinear diffusion equation with a diffusion coefficient $D(v)$ that depends on $v$ through the plasma dielectric constant. If the plasma is isotropically forced on scales much larger than the Debye length with a white noise-like electric field, then $D(v)sim v^4$ for $sigma
{"title":"Universal non-thermal power-law distribution functions from the self-consistent evolution of collisionless electrostatic plasmas","authors":"Uddipan Banik, Amitava Bhattacharjee, Wrick Sengupta","doi":"arxiv-2408.07127","DOIUrl":"https://doi.org/arxiv-2408.07127","url":null,"abstract":"Distribution functions of collisionless systems are known to show non-thermal\u0000power law tails. Interestingly, collisionless plasmas in various physical\u0000scenarios, (e.g., the ion population of the solar wind) feature a $v^{-5}$ tail\u0000in the velocity ($v$) distribution, whose origin has been a long-standing\u0000mystery. We show this power law tail to be a natural outcome of the\u0000self-consistent collisionless relaxation of driven electrostatic plasmas. We\u0000perform a quasilinear analysis of the perturbed Vlasov-Poisson equations to\u0000show that the coarse-grained mean distribution function (DF), $f_0$, follows a\u0000quasilinear diffusion equation with a diffusion coefficient $D(v)$ that depends\u0000on $v$ through the plasma dielectric constant. If the plasma is isotropically\u0000forced on scales much larger than the Debye length with a white noise-like\u0000electric field, then $D(v)sim v^4$ for $sigma<v<omega_{mathrm{P}}/k$, with\u0000$sigma$ the thermal velocity, $omega_{mathrm{P}}$ the plasma frequency and\u0000$k$ the maximum wavenumber of the perturbation; the corresponding $f_0$, in the\u0000quasi-steady state, develops a $v^{-left(d+2right)}$ tail in $d$ dimensions\u0000($v^{-5}$ tail in 3D), while the energy ($E$) distribution develops an $E^{-2}$\u0000tail irrespective of the dimensionality of space. Any redness of the noise only\u0000alters the scaling in the high $v$ end. Non-resonant particles moving slower\u0000than the phase-velocity of the plasma waves ($omega_{mathrm{P}}/k$)\u0000experience a Debye-screened electric field, and significantly less (power law\u0000suppressed) acceleration than the near-resonant particles. Thus, a Maxwellian\u0000DF develops a power law tail. The Maxwellian core ($v<sigma$) eventually also\u0000heats up, but over a much longer timescale than that over which the tail forms.\u0000We definitively show that self-consistency (ignored in test-particle\u0000treatments) is crucial for the development of the universal $v^{-5}$ tail.","PeriodicalId":501423,"journal":{"name":"arXiv - PHYS - Space Physics","volume":"12 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142178258","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}
Filament eruptions and coronal mass ejections are physical phenomena related to magnetic flux ropes carrying electric current. A magnetic flux rope is a key structure for solar eruptions, and when it carries a southward magnetic field component when propagating to the Earth. It is the primary driver of strong geomagnetic storms. As a result, developing a numerical model capable of capturing the entire progression of a flux rope, from its inception to its eruptive phase, is crucial for forecasting adverse space weather. The existence of such flux ropes is revealed by the presence of sigmoids in active regions or hot channels by observations from space and ground instruments. After proposing cartoons in 2D, potential, linear, non-linear-force-free-field (NLFFF) and non-force-free-field (NFFF) magnetic extrapolations, 3D numerical magnetohydrodynamic (MHD) simulation models were developed, first in a static configuration and later dynamic data-driven MHD models using high resolution observed vector magnetograms. This paper reviews a few recent developments in data-driven mode, such as the time-dependent magneto-frictional (TMF) and thermodynamic magnetohydrodynamic (MHD) models. Hereafter, to demonstrate the capacity of these models to reveal the physics of observations, we present the results for three events explored in our group: 1. the eruptive X1.0 flare on 28 October 2021; 2. the filament eruption on 18 August 2022; and 3. the confined X2.2 flare on 6 September 2017. These case studies validate the ability of data-driven models to retrieve observations, including the formation and eruption of flux ropes, 3D magnetic reconnection, CME three-part structures and the failed eruption. Based on these results, we provide some arguments for the formation mechanisms of flux ropes, the physical nature of the CME leading front, and the constraints of failed eruptions.
{"title":"Recent advances in solar data-driven MHD simulations of the formation and evolution of CME flux ropes","authors":"Brigitte Schmieder, Jinhan Guo, Stefaan Poedts","doi":"arxiv-2408.06595","DOIUrl":"https://doi.org/arxiv-2408.06595","url":null,"abstract":"Filament eruptions and coronal mass ejections are physical phenomena related\u0000to magnetic flux ropes carrying electric current. A magnetic flux rope is a key\u0000structure for solar eruptions, and when it carries a southward magnetic field\u0000component when propagating to the Earth. It is the primary driver of strong\u0000geomagnetic storms. As a result, developing a numerical model capable of\u0000capturing the entire progression of a flux rope, from its inception to its\u0000eruptive phase, is crucial for forecasting adverse space weather. The existence\u0000of such flux ropes is revealed by the presence of sigmoids in active regions or\u0000hot channels by observations from space and ground instruments. After proposing\u0000cartoons in 2D, potential, linear, non-linear-force-free-field (NLFFF) and\u0000non-force-free-field (NFFF) magnetic extrapolations, 3D numerical\u0000magnetohydrodynamic (MHD) simulation models were developed, first in a static\u0000configuration and later dynamic data-driven MHD models using high resolution\u0000observed vector magnetograms. This paper reviews a few recent developments in\u0000data-driven mode, such as the time-dependent magneto-frictional (TMF) and\u0000thermodynamic magnetohydrodynamic (MHD) models. Hereafter, to demonstrate the\u0000capacity of these models to reveal the physics of observations, we present the\u0000results for three events explored in our group: 1. the eruptive X1.0 flare on\u000028 October 2021; 2. the filament eruption on 18 August 2022; and 3. the\u0000confined X2.2 flare on 6 September 2017. These case studies validate the\u0000ability of data-driven models to retrieve observations, including the formation\u0000and eruption of flux ropes, 3D magnetic reconnection, CME three-part structures\u0000and the failed eruption. Based on these results, we provide some arguments for\u0000the formation mechanisms of flux ropes, the physical nature of the CME leading\u0000front, and the constraints of failed eruptions.","PeriodicalId":501423,"journal":{"name":"arXiv - PHYS - Space Physics","volume":"16 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142178442","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 has been suggested that under solar coronal conditions, drift waves may contribute to coronal heating. Specific properties of the drift waves to be expected in the solar corona have, however, not yet been determined using more advanced numerical models. We investigate the linear properties of density-gradient-driven drift waves in the solar coronal plasma using gyrokinetic ion-electron simulations with the gyrokinetic code GENE, solving the Vlasov-Maxwell equations in five dimensions assuming a simple slab geometry. We determine the frequencies and growth rates of the coronal density gradient-driven drift waves with changing plasma parameters, such as the electron b{eta} , the density gradient, the magnetic shear and additional temperature gradients. To investigate the influence of the finite Larmor radius effect on the growth and structure of the modes, we also compare the gyrokinetic simulation results to those obtained from drift-kinetics. In most of the investigated conditions, the drift wave has positive growth rates that increase with increasing density gradient and decreasing b{eta} . In the case of increasing magnetic shear, we find that from a certain point, the growth rate reaches a plateau. Depending on the considered reference environment, the frequencies and growth rates of these waves lie on the order of 0.1 mHz to 1 Hz. These values correspond to the observed solar wind density fluctuations near the Sun detected by WISPR, currently of unexplained origin. As a next step, nonlinear simulations are required to determine the expected fluctuation amplitudes and the plasma heating resulting from this mechanism.
{"title":"Density-gradient-driven drift waves in the solar corona","authors":"Michaela Brchnelova, MJ Pueschel, Stefaan Poedts","doi":"arxiv-2408.06696","DOIUrl":"https://doi.org/arxiv-2408.06696","url":null,"abstract":"It has been suggested that under solar coronal conditions, drift waves may\u0000contribute to coronal heating. Specific properties of the drift waves to be\u0000expected in the solar corona have, however, not yet been determined using more\u0000advanced numerical models. We investigate the linear properties of\u0000density-gradient-driven drift waves in the solar coronal plasma using\u0000gyrokinetic ion-electron simulations with the gyrokinetic code GENE, solving\u0000the Vlasov-Maxwell equations in five dimensions assuming a simple slab\u0000geometry. We determine the frequencies and growth rates of the coronal density\u0000gradient-driven drift waves with changing plasma parameters, such as the\u0000electron b{eta} , the density gradient, the magnetic shear and additional\u0000temperature gradients. To investigate the influence of the finite Larmor radius\u0000effect on the growth and structure of the modes, we also compare the\u0000gyrokinetic simulation results to those obtained from drift-kinetics. In most\u0000of the investigated conditions, the drift wave has positive growth rates that\u0000increase with increasing density gradient and decreasing b{eta} . In the case\u0000of increasing magnetic shear, we find that from a certain point, the growth\u0000rate reaches a plateau. Depending on the considered reference environment, the\u0000frequencies and growth rates of these waves lie on the order of 0.1 mHz to 1\u0000Hz. These values correspond to the observed solar wind density fluctuations\u0000near the Sun detected by WISPR, currently of unexplained origin. As a next\u0000step, nonlinear simulations are required to determine the expected fluctuation\u0000amplitudes and the plasma heating resulting from this mechanism.","PeriodicalId":501423,"journal":{"name":"arXiv - PHYS - Space Physics","volume":"386 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142178443","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}
Rattanakorn Koontaweepunya, Yakov S. Dimant, Meers M. Oppenheim
Strong electric fields in the auroral and equatorial electrojets can distort the background ion distribution function away from Maxwellian. We developed a collisional plasma kinetic model using the Boltzmann equation and a simple BGK collision operator which predicts a relatively simple relationship between the intensity of the background electric field and the resulting ion distribution function. To test the model, we perform 3-D plasma particle-in-cell simulations and compare the results to the model. The simulation applies an elastic collision operator assuming a constant ion-neutral collision rate. These simulations show less ion heating in the Pedersen direction than the analytic model but show similar overall heating. The model overestimates the heating in the Pedersen direction because the simple BGK operator includes no angular collisional scattering in the ion velocity space. On the other hand, the fully-kinetic particle-in-cell code is able to capture the physics of ion scattering in 3-D and therefore heats ions more isotropically. Although the simple BGK analytic theory does not precisely model the non-Maxwellian ion distribution function, it does capture the overall momentum and energy flows and therefore can provide the basis of further analysis of E-region wave evolution.
{"title":"Non-Maxwellian Ion Distribution in the Equatorial and Auroral Electrojets","authors":"Rattanakorn Koontaweepunya, Yakov S. Dimant, Meers M. Oppenheim","doi":"arxiv-2408.06339","DOIUrl":"https://doi.org/arxiv-2408.06339","url":null,"abstract":"Strong electric fields in the auroral and equatorial electrojets can distort\u0000the background ion distribution function away from Maxwellian. We developed a\u0000collisional plasma kinetic model using the Boltzmann equation and a simple BGK\u0000collision operator which predicts a relatively simple relationship between the\u0000intensity of the background electric field and the resulting ion distribution\u0000function. To test the model, we perform 3-D plasma particle-in-cell simulations\u0000and compare the results to the model. The simulation applies an elastic\u0000collision operator assuming a constant ion-neutral collision rate. These\u0000simulations show less ion heating in the Pedersen direction than the analytic\u0000model but show similar overall heating. The model overestimates the heating in\u0000the Pedersen direction because the simple BGK operator includes no angular\u0000collisional scattering in the ion velocity space. On the other hand, the\u0000fully-kinetic particle-in-cell code is able to capture the physics of ion\u0000scattering in 3-D and therefore heats ions more isotropically. Although the\u0000simple BGK analytic theory does not precisely model the non-Maxwellian ion\u0000distribution function, it does capture the overall momentum and energy flows\u0000and therefore can provide the basis of further analysis of E-region wave\u0000evolution.","PeriodicalId":501423,"journal":{"name":"arXiv - PHYS - Space Physics","volume":"48 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142178257","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}
Parker Solar Probe (PSP) counts dust impacts in the near-solar region, but modelling effort is needed to understand the dust population's properties. We aim to constrain the dust cloud's properties based on the flux observed by PSP. We develop a forward-model for the bound dust detection rates using the formalism of 6D phase space distribution of the dust. We apply the model to the location table of different PSP's solar encounter groups. We explain some of the near-perihelion features observed in the data as well as the broader characteristic of the dust flux between 0.15 AU and 0.5 AU. We compare the measurements of PSP to the measurements of Solar Orbiter (SolO) near 1 AU to expose the differences between the two spacecraft. We found that the dust flux observed by PSP between 0.15 AU and 0.5 AU in post-perihelia can be explained by dust on bound orbits and is consistent with a broad range of orbital parameters, including dust on circular orbits. However, the dust number density as a function of the heliocentric distance and the scaling of detection efficiency with the relative speed are important to explain the observed flux variation. The data suggest that the slope of differential mass distribution ${delta}$ is between 0.14 and 0.49. The near-perihelion observations, however, show the flux maxima, which are inconsistent with the circular dust model, and additional effects may play a role. We found indication that the sunward side of PSP is less sensitive to the dust impacts, compared to the other PSP's surfaces. Conclusions. We show that the dust flux on PSP can be explained by non-circular bound dust and the detection capabilities of PSP. The scaling of flux with the impact speed is especially important, and shallower than previously assumed.
帕克太阳探测器（Parker Solar Probe，PSP）对近太阳区的尘埃撞击进行计数，但要了解尘埃群的特性还需要建模工作。我们利用尘埃 6D 相空间分布的形式主义，建立了一个约束尘埃探测率的前向模型。我们将该模型应用于不同PSP太阳遭遇组的定位表。我们解释了数据中观测到的一些近近日点特征，以及 0.15 AU 和 0.5 AU 之间尘埃通量的更广泛特征。我们将 PSP 的测量结果与太阳轨道器（Solar Orbiter，SolO）在 1 AU 附近的测量结果进行了比较，以显示两个航天器之间的差异。我们发现，PSP观测到的后近日期0.15 AU和0.5 AU之间的尘埃通量可以用约束轨道上的尘埃来解释，并且与广泛的轨道参数一致，包括圆形轨道上的尘埃。然而，尘埃数量密度与日心距离的函数关系以及探测效率与相对速度的比例关系对于解释观测到的通量变化非常重要。数据表明，差分质量分布${delta}$的斜率介于0.14和0.49之间。然而，近近日点观测到的通量最大值与圆形尘埃模型不一致，可能还有其他影响。我们发现，与其他 PSP 表面相比，PSP 向阳面对尘埃撞击的敏感度较低。结论。我们的研究表明，PSP上的尘埃通量可以用非圆形束缚尘埃和PSP的探测能力来解释。尘埃通量与撞击速度的比例关系尤为重要，而且比以前假设的要浅。
{"title":"On the distribution of the the near-solar bound dust grains detected with Parker Solar Probe","authors":"Samuel Kočiščák, Audun Theodorsen, Ingrid Mann","doi":"arxiv-2408.05031","DOIUrl":"https://doi.org/arxiv-2408.05031","url":null,"abstract":"Parker Solar Probe (PSP) counts dust impacts in the near-solar region, but\u0000modelling effort is needed to understand the dust population's properties. We\u0000aim to constrain the dust cloud's properties based on the flux observed by PSP.\u0000We develop a forward-model for the bound dust detection rates using the\u0000formalism of 6D phase space distribution of the dust. We apply the model to the\u0000location table of different PSP's solar encounter groups. We explain some of\u0000the near-perihelion features observed in the data as well as the broader\u0000characteristic of the dust flux between 0.15 AU and 0.5 AU. We compare the\u0000measurements of PSP to the measurements of Solar Orbiter (SolO) near 1 AU to\u0000expose the differences between the two spacecraft. We found that the dust flux\u0000observed by PSP between 0.15 AU and 0.5 AU in post-perihelia can be explained\u0000by dust on bound orbits and is consistent with a broad range of orbital\u0000parameters, including dust on circular orbits. However, the dust number density\u0000as a function of the heliocentric distance and the scaling of detection\u0000efficiency with the relative speed are important to explain the observed flux\u0000variation. The data suggest that the slope of differential mass distribution\u0000${delta}$ is between 0.14 and 0.49. The near-perihelion observations, however,\u0000show the flux maxima, which are inconsistent with the circular dust model, and\u0000additional effects may play a role. We found indication that the sunward side\u0000of PSP is less sensitive to the dust impacts, compared to the other PSP's\u0000surfaces. Conclusions. We show that the dust flux on PSP can be explained by\u0000non-circular bound dust and the detection capabilities of PSP. The scaling of\u0000flux with the impact speed is especially important, and shallower than\u0000previously assumed.","PeriodicalId":501423,"journal":{"name":"arXiv - PHYS - Space Physics","volume":"48 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141946758","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}
In the field of spaceflight mechanics and astrodynamics, determining eclipse regions is a frequent and critical challenge. This determination impacts various factors, including the acceleration induced by solar radiation pressure, the spacecraft power input, and its thermal state all of which must be accounted for in various phases of the mission design. This study leverages recent advances in neural image processing to develop fully differentiable models of eclipse regions for highly irregular celestial bodies. By utilizing test cases involving Solar System bodies previously visited by spacecraft, such as 433 Eros, 25143 Itokawa, 67P/Churyumov--Gerasimenko, and 101955 Bennu, we propose and study an implicit neural architecture defining the shape of the eclipse cone based on the Sun's direction. Employing periodic activation functions, we achieve high precision in modeling eclipse conditions. Furthermore, we discuss the potential applications of these differentiable models in spaceflight mechanics computations.
{"title":"EclipseNETs: a differentiable description of irregular eclipse conditions","authors":"Giacomo Acciarini, Francesco Biscani, Dario Izzo","doi":"arxiv-2408.05387","DOIUrl":"https://doi.org/arxiv-2408.05387","url":null,"abstract":"In the field of spaceflight mechanics and astrodynamics, determining eclipse\u0000regions is a frequent and critical challenge. This determination impacts\u0000various factors, including the acceleration induced by solar radiation\u0000pressure, the spacecraft power input, and its thermal state all of which must\u0000be accounted for in various phases of the mission design. This study leverages\u0000recent advances in neural image processing to develop fully differentiable\u0000models of eclipse regions for highly irregular celestial bodies. By utilizing\u0000test cases involving Solar System bodies previously visited by spacecraft, such\u0000as 433 Eros, 25143 Itokawa, 67P/Churyumov--Gerasimenko, and 101955 Bennu, we\u0000propose and study an implicit neural architecture defining the shape of the\u0000eclipse cone based on the Sun's direction. Employing periodic activation\u0000functions, we achieve high precision in modeling eclipse conditions.\u0000Furthermore, we discuss the potential applications of these differentiable\u0000models in spaceflight mechanics computations.","PeriodicalId":501423,"journal":{"name":"arXiv - PHYS - Space Physics","volume":"10 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142223610","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}
Michael F. Zhang, Matthew W. Kunz, Jonathan Squire, Kristopher G. Klein
Minor ions in the solar corona are heated to extreme temperatures, far in excess of those of the electrons and protons that comprise the bulk of the plasma. These highly non-thermal distributions make minor ions sensitive probes of the underlying collisionless heating processes, which are crucial to coronal heating and the creation of the solar wind. The recent discovery of the "helicity barrier" offers a mechanism where imbalanced Alfv'enic turbulence in low-beta plasmas preferentially heats protons over electrons, generating high-frequency, proton-cyclotron-resonant fluctuations. We use the hybrid-kinetic particle-in-cell code, Pegasus++, to drive imbalanced Alfv'enic turbulence in a 3D low-beta plasma with additional passive ion species, He$^{2+}$ and O$^{5+}$. A helicity barrier naturally develops, followed by clear phase-space signatures of oblique ion-cyclotron-wave heating and Landau-resonant heating from the imbalanced Alfv'enic fluctuations. The former results in characteristically arced ion velocity distribution functions, whose non-bi-Maxwellian features are shown by linear ALPS calculations to be critical to the heating process. Additional features include a steep transition-range electromagnetic spectrum, the presence of ion-cyclotron waves propagating in the direction of imbalance, significantly enhanced proton-to-electron heating ratios, anisotropic ion temperatures that are significantly more perpendicular with respect to magnetic field, and extreme heating of heavier species in a manner consistent with empirically derived mass scalings informed by measurements. None of these features are realized in an otherwise equivalent simulation of balanced turbulence. If seen simultaneously in the fast solar wind, these signatures of the helicity barrier would testify to the necessity of incorporating turbulence imbalance in a complete theory for the evolution of the solar wind.
{"title":"Extreme heating of minor ions in imbalanced solar-wind turbulence","authors":"Michael F. Zhang, Matthew W. Kunz, Jonathan Squire, Kristopher G. Klein","doi":"arxiv-2408.04703","DOIUrl":"https://doi.org/arxiv-2408.04703","url":null,"abstract":"Minor ions in the solar corona are heated to extreme temperatures, far in\u0000excess of those of the electrons and protons that comprise the bulk of the\u0000plasma. These highly non-thermal distributions make minor ions sensitive probes\u0000of the underlying collisionless heating processes, which are crucial to coronal\u0000heating and the creation of the solar wind. The recent discovery of the\u0000\"helicity barrier\" offers a mechanism where imbalanced Alfv'enic turbulence in\u0000low-beta plasmas preferentially heats protons over electrons, generating\u0000high-frequency, proton-cyclotron-resonant fluctuations. We use the\u0000hybrid-kinetic particle-in-cell code, Pegasus++, to drive imbalanced Alfv'enic\u0000turbulence in a 3D low-beta plasma with additional passive ion species,\u0000He$^{2+}$ and O$^{5+}$. A helicity barrier naturally develops, followed by\u0000clear phase-space signatures of oblique ion-cyclotron-wave heating and\u0000Landau-resonant heating from the imbalanced Alfv'enic fluctuations. The former\u0000results in characteristically arced ion velocity distribution functions, whose\u0000non-bi-Maxwellian features are shown by linear ALPS calculations to be critical\u0000to the heating process. Additional features include a steep transition-range\u0000electromagnetic spectrum, the presence of ion-cyclotron waves propagating in\u0000the direction of imbalance, significantly enhanced proton-to-electron heating\u0000ratios, anisotropic ion temperatures that are significantly more perpendicular\u0000with respect to magnetic field, and extreme heating of heavier species in a\u0000manner consistent with empirically derived mass scalings informed by\u0000measurements. None of these features are realized in an otherwise equivalent\u0000simulation of balanced turbulence. If seen simultaneously in the fast solar\u0000wind, these signatures of the helicity barrier would testify to the necessity\u0000of incorporating turbulence imbalance in a complete theory for the evolution of\u0000the solar wind.","PeriodicalId":501423,"journal":{"name":"arXiv - PHYS - Space Physics","volume":"28 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141946756","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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