To the first post-Newtonian order, the gravitational action of mass-energy currents is encoded by the off-diagonal gravitomagnetic components of the spacetime metric tensor. If they are time-dependent, a further acceleration enters the equations of motion of a moving test particle. Let the source of the gravitational field be an isolated, massive body rigidly rotating whose spin angular momentum experiences a slow precessional motion. The impact of the aforementioned acceleration on the orbital motion of a test particle is analytically worked out in full generality. The resulting averaged rates of change are valid for any orbital configuration of the satellite; furthermore, they hold for an arbitrary orientation of the precessional velocity vector of the spin of the central object. In general, all the orbital elements, with the exception of the mean anomaly at epoch, undergo nonvanishing long-term variations which, in the case of the Juno spacecraft currently orbiting Jupiter and the double pulsar PSR J0737-3039 A/B turn out to be quite small. Such effects might become much more relevant in a star-supermassive black hole scenario; as an example, the relative change of the semimajor axis of a putative test particle orbiting a Kerr black hole as massive as the one at the Galactic Centre at, say, 100 Schwarzschild radii may amount up to about $7%$ per year if the hole's spin precessional frequency is $10%$ of the particle's orbital one.
在牛顿后一阶，质能流的引力作用由时空度量张量的对角线外引力磁分量编码。如果这些分量与时间相关，则会在运动的测试粒子的运动方程中加入进一步的加速度。假设引力场源是一个孤立的、刚性旋转的大质量体，其自旋动量经历了缓慢的前向运动。对上述加速度对测试粒子轨道运动的影响进行了全面的分析。由此得出的平均变化率适用于卫星的任何轨道构型；此外，它们还适用于中心物体自旋前向速度矢量的任意方向。一般来说，所有的轨道元素，除了平均异常值之外，都会发生非消失性的长期变化，就目前围绕木星和双脉冲星 PSR J0737-3039 A/B 运行的朱诺号航天器而言，这种变化非常小。在恒星-超大质量黑洞的情况下，这种效应可能会变得更加重要；举例来说，如果黑洞的自旋前旋频率是粒子轨道频率的10%，那么围绕银河系中心的克尔黑洞（质量相当于100个施瓦兹柴尔德半径）运行的测试粒子的半长轴的相对变化可能达到每年7%。
{"title":"On the Euler-type gravitomagnetic orbital effects in the field of a precessing body","authors":"Lorenzo Iorio","doi":"arxiv-2409.11895","DOIUrl":"https://doi.org/arxiv-2409.11895","url":null,"abstract":"To the first post-Newtonian order, the gravitational action of mass-energy\u0000currents is encoded by the off-diagonal gravitomagnetic components of the\u0000spacetime metric tensor. If they are time-dependent, a further acceleration\u0000enters the equations of motion of a moving test particle. Let the source of the\u0000gravitational field be an isolated, massive body rigidly rotating whose spin\u0000angular momentum experiences a slow precessional motion. The impact of the\u0000aforementioned acceleration on the orbital motion of a test particle is\u0000analytically worked out in full generality. The resulting averaged rates of\u0000change are valid for any orbital configuration of the satellite; furthermore,\u0000they hold for an arbitrary orientation of the precessional velocity vector of\u0000the spin of the central object. In general, all the orbital elements, with the\u0000exception of the mean anomaly at epoch, undergo nonvanishing long-term\u0000variations which, in the case of the Juno spacecraft currently orbiting Jupiter\u0000and the double pulsar PSR J0737-3039 A/B turn out to be quite small. Such\u0000effects might become much more relevant in a star-supermassive black hole\u0000scenario; as an example, the relative change of the semimajor axis of a\u0000putative test particle orbiting a Kerr black hole as massive as the one at the\u0000Galactic Centre at, say, 100 Schwarzschild radii may amount up to about $7%$\u0000per year if the hole's spin precessional frequency is $10%$ of the particle's\u0000orbital one.","PeriodicalId":501423,"journal":{"name":"arXiv - PHYS - Space Physics","volume":"64 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142268248","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}
Luiz A. C. A. Schiavo, Gert J. J. Botha, James A. McLaughlin
Oscillatory reconnection is a specific type of time-dependent reconnection which involves periodic changes in the magnetic topology of a null point. The mechanism has been reported for a variety of magnetic field strengths and configurations, background temperatures and densities. All these studies report an oscillation in the current density at the null point, but also report a variety of periods, amplitudes and overall behaviors. We conduct a parametric study for equilibrium magnetic field strength and initial background temperature, solving 2D resistive MHD equations around a magnetic X-point. We introduce a parameter space for the ratio of internal-to-magnetic energy and find self-similar solutions for simulations where this ratio is below 0.1 (which represents a magnetically-dominated environment or, equivalently, a low-beta plasma). Self-similarity can be seen in oscillations in the current density at the null (including amplitude and period), Ohmic heating and the temperature generated via reconnection jets. The parameter space of energy ratios also allows us to contextualize previous studies of the oscillatory reconnection mechanism and bring those different studies together into a single unified understanding.
振荡再连接是一种特定类型的随时间变化的再连接，它涉及空点磁拓扑结构的周期性变化。据报道，该机制适用于各种磁场强度和配置、背景温度和密度。所有这些研究都报告了空穴处电流密度的振荡，但也报告了各种周期、振幅和总体行为。我们对平衡磁场强度和初始背景温度进行了参数研究，求解了围绕磁 X 点的二维电阻 MHD 方程。我们引入了内能与磁能之比的参数空间，并在该比值低于 0.1（代表磁主导环境或低贝塔等离子体）的模拟中找到了自相似解。自相似性体现在空点处的电流密度振荡（包括振幅和周期）、欧姆加热以及通过再连接喷流产生的温度。能量比的参数空间也使我们能够将以前对振荡再连接机制的研究与背景联系起来，并将这些不同的研究整合为一个统一的认识。
{"title":"Self-similar solutions of oscillatory reconnection: parameter study of magnetic field strength and background temperature","authors":"Luiz A. C. A. Schiavo, Gert J. J. Botha, James A. McLaughlin","doi":"arxiv-2409.12130","DOIUrl":"https://doi.org/arxiv-2409.12130","url":null,"abstract":"Oscillatory reconnection is a specific type of time-dependent reconnection\u0000which involves periodic changes in the magnetic topology of a null point. The\u0000mechanism has been reported for a variety of magnetic field strengths and\u0000configurations, background temperatures and densities. All these studies report\u0000an oscillation in the current density at the null point, but also report a\u0000variety of periods, amplitudes and overall behaviors. We conduct a parametric\u0000study for equilibrium magnetic field strength and initial background\u0000temperature, solving 2D resistive MHD equations around a magnetic X-point. We\u0000introduce a parameter space for the ratio of internal-to-magnetic energy and\u0000find self-similar solutions for simulations where this ratio is below 0.1\u0000(which represents a magnetically-dominated environment or, equivalently, a\u0000low-beta plasma). Self-similarity can be seen in oscillations in the current\u0000density at the null (including amplitude and period), Ohmic heating and the\u0000temperature generated via reconnection jets. The parameter space of energy\u0000ratios also allows us to contextualize previous studies of the oscillatory\u0000reconnection mechanism and bring those different studies together into a single\u0000unified understanding.","PeriodicalId":501423,"journal":{"name":"arXiv - PHYS - Space Physics","volume":"212 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142268195","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 perturbations of the hyperbolic motion of a test particle due to the general relativistic gravitoelectromagnetic Schwarzschild and Lense-Thirring components of the gravitational field of a massive, rotating body are analytically worked out to the first post-Newtonian level. To the Newtonian order, the impact of the quadrupole mass moment of the source is calculated as well. The resulting analytical expressions are valid for a generic orientation in space of both the orbital plane of the probe and the spin axis of the primary, and for arbitrary values of the eccentricity. They are applied first to 'Oumuamua, an interstellar asteroid which recently visited our solar system along an unbound heliocentric orbit. While its gravitoelectric shifts occurred close to the Sun's flyby are less than some tens of milliarcseconds, those due to the solar oblateness and angular momentum are of the order of microarcseconds throughout the whole trajectory. Comparable values occur for the post-Newtonian shifts of the Near Earth Asteroid Rendezvous (NEAR) spacecraft during its flyby of the Earth, while those due to the oblateness of the latter are nominally several orders of magnitude larger. The current (formal) uncertainty in the quadrupole mass moment of the geopotential would bring the mismodeling of such classical effects below the nominal value of the predicted relativistic disturbances. The hyperbolic excess velocity is not changed by any of the post--Keplerian accelerations considered. The calculational approach developed can be straightforwardly extended to any alternative models of gravity as well.
{"title":"Post-Keplerian perturbations of the hyperbolic motion in the field of a massive, rotating object","authors":"Lorenzo Iorio","doi":"arxiv-2409.12063","DOIUrl":"https://doi.org/arxiv-2409.12063","url":null,"abstract":"The perturbations of the hyperbolic motion of a test particle due to the\u0000general relativistic gravitoelectromagnetic Schwarzschild and Lense-Thirring\u0000components of the gravitational field of a massive, rotating body are\u0000analytically worked out to the first post-Newtonian level. To the Newtonian\u0000order, the impact of the quadrupole mass moment of the source is calculated as\u0000well. The resulting analytical expressions are valid for a generic orientation\u0000in space of both the orbital plane of the probe and the spin axis of the\u0000primary, and for arbitrary values of the eccentricity. They are applied first\u0000to 'Oumuamua, an interstellar asteroid which recently visited our solar system\u0000along an unbound heliocentric orbit. While its gravitoelectric shifts occurred\u0000close to the Sun's flyby are less than some tens of milliarcseconds, those due\u0000to the solar oblateness and angular momentum are of the order of\u0000microarcseconds throughout the whole trajectory. Comparable values occur for\u0000the post-Newtonian shifts of the Near Earth Asteroid Rendezvous (NEAR)\u0000spacecraft during its flyby of the Earth, while those due to the oblateness of\u0000the latter are nominally several orders of magnitude larger. The current\u0000(formal) uncertainty in the quadrupole mass moment of the geopotential would\u0000bring the mismodeling of such classical effects below the nominal value of the\u0000predicted relativistic disturbances. The hyperbolic excess velocity is not\u0000changed by any of the post--Keplerian accelerations considered. The\u0000calculational approach developed can be straightforwardly extended to any\u0000alternative models of gravity as well.","PeriodicalId":501423,"journal":{"name":"arXiv - PHYS - Space Physics","volume":"157 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142268247","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}
Ying D. Liu, Huidong Hu, Xiaowei Zhao, Chong Chen, Rui Wang
The largest geomagnetic storm in two decades occurred in 2024 May with a minimum $D_{rm st}$ of $-412$ nT. We examine its solar and interplanetary origins by combining multipoint imaging and in situ observations. The source active region, NOAA AR 13664, exhibited extraordinary activity and produced successive halo eruptions, which were responsible for two complex ejecta observed at the Earth. In situ measurements from STEREO A, which was $12.6^{circ}$ apart, allow us to compare the ``geo-effectiveness" at the Earth and STEREO A. We obtain key findings concerning the formation of solar superstorms and how mesoscale variations of coronal mass ejections affect geo-effectiveness: (1) the 2024 May storm supports the hypothesis that solar superstorms are ``perfect storms" in nature, i.e., a combination of circumstances resulting in an event of an unusual magnitude; (2) the first complex ejecta, which caused the geomagnetic superstorm, shows considerable differences in the magnetic field and associated ``geo-effectiveness" between the Earth and STEREO A, despite a mesoscale separation; and (3) two contrasting cases of complex ejecta are found in terms of the geo-effectiveness at the Earth, which is largely due to different magnetic field configurations within the same active region.
2024年5月发生了二十年来最大的地磁暴，其最大值$D_{rm st}$为$-412$ nT。我们结合多点成像和现场观测，研究了它的太阳和行星际起源。源活动区 NOAA AR 13664 表现出了非同寻常的活动，并产生了连续的晕喷发，这是在地球上观测到的两个复杂喷出物的原因。我们获得了有关太阳超级风暴的形成以及日冕物质抛射的中尺度变化如何影响地球效应的重要发现：（1）2024 年 5 月的风暴支持了太阳超级风暴在本质上是 "完美风暴 "的假设，即："完美风暴 "是由各种条件的组合造成的、(2)造成地磁超级风暴的第一个复合抛射物显示地球和 STEREO A 之间的磁场和相关 "地球效应 "存在相当大的差异，尽管存在中尺度的分隔；(3)在地球的地球效应方面发现了两种截然不同的复合抛射物情况，这在很大程度上是由于同一活动区域内不同的磁场配置造成的。
{"title":"A Pileup of Coronal Mass Ejections Produced the Largest Geomagnetic Storm in Two Decades","authors":"Ying D. Liu, Huidong Hu, Xiaowei Zhao, Chong Chen, Rui Wang","doi":"arxiv-2409.11492","DOIUrl":"https://doi.org/arxiv-2409.11492","url":null,"abstract":"The largest geomagnetic storm in two decades occurred in 2024 May with a\u0000minimum $D_{rm st}$ of $-412$ nT. We examine its solar and interplanetary\u0000origins by combining multipoint imaging and in situ observations. The source\u0000active region, NOAA AR 13664, exhibited extraordinary activity and produced\u0000successive halo eruptions, which were responsible for two complex ejecta\u0000observed at the Earth. In situ measurements from STEREO A, which was\u0000$12.6^{circ}$ apart, allow us to compare the ``geo-effectiveness\" at the Earth\u0000and STEREO A. We obtain key findings concerning the formation of solar\u0000superstorms and how mesoscale variations of coronal mass ejections affect\u0000geo-effectiveness: (1) the 2024 May storm supports the hypothesis that solar\u0000superstorms are ``perfect storms\" in nature, i.e., a combination of\u0000circumstances resulting in an event of an unusual magnitude; (2) the first\u0000complex ejecta, which caused the geomagnetic superstorm, shows considerable\u0000differences in the magnetic field and associated ``geo-effectiveness\" between\u0000the Earth and STEREO A, despite a mesoscale separation; and (3) two contrasting\u0000cases of complex ejecta are found in terms of the geo-effectiveness at the\u0000Earth, which is largely due to different magnetic field configurations within\u0000the same active region.","PeriodicalId":501423,"journal":{"name":"arXiv - PHYS - Space Physics","volume":"183 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142247667","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}
Xuechao Zhang, Hongqiang Song, Xiaoqian Wang, Leping Li, Hui Fu, Rui Wang, Yao Chen
Alpha-proton differential flow ($V_{alpha p}$) of coronal mass ejections (CMEs) and solar wind from the Sun to 1 au and beyond could influence the instantaneous correspondence of absolute abundances of alpha particles (He$^{2+}$/H$^{+}$) between solar corona and interplanetary space as the abundance of a coronal source can vary with time. Previous studies based on Ulysses and Helios showed that $V_{alpha p}$ is negligible within CMEs from 5 to 0.3 au, similar to slow solar wind ($<$ 400 km s$^{-1}$). However, recent new observations using Parker Solar Probe (PSP) revealed that the $V_{alpha p}$ of slow wind increases to $sim$60 km s$^{-1}$ inside 0.1 au. It is significant to answer whether the $V_{alpha p}$ of CMEs exhibits the similar behavior near the Sun. In this Letter, we report the $V_{alpha p}$ of a CME measured by PSP at $sim$15 $R_odot$ for the first time, which demonstrates that the $V_{alpha p}$ of CMEs is obvious and complex inside 0.1 au while keeps lower than the local Alfv'{e}n speed. A very interesting point is that the same one CME duration can be divided into A and B intervals clearly with Coulomb number below and beyond 0.5, respectively. The means of $V_{alpha p}$ and alpha-to-proton temperature ratios of interval A (B) is 96.52 (21.96) km s$^{-1}$ and 7.65 (2.23), respectively. This directly illustrates that Coulomb collisions play an important role in reducing the non-equilibrium features of CMEs. Our study indicates that the absolute elemental abundances of CMEs also might vary during their propagation.
日冕物质抛射（CMEs）和太阳风的α-质子差流（$V_{alpha p}$）从太阳到1 au甚至更远，可能会影响日冕和行星际空间之间α粒子（He$^{2+}$/H$^{+}$）绝对丰度的瞬时对应关系，因为日冕源的丰度会随时间变化。以前基于Ulysses和Helios的研究表明，$V_{alpha p}$在5到0.3 au的CME内可以忽略不计，类似于缓慢的太阳风（$<$ 400 km s$^{-1}$）。然而，最近利用帕克太阳探测器（Parker Solar Probe，PSP）进行的最新观测发现，慢风的$V_{alphap}$在0.1au内增加到了$sim$60 km s$^{-1}$。回答CMEs的$V_{alpha p}$在太阳附近是否表现出类似的行为具有重要意义。在这封信中，我们首次报告了用PSP在$sim$15 $R_odot$测量到的CME的$V_{alpha p}$，这表明CME的$V_{alpha p}$在0.1au内是明显而复杂的，同时保持低于当地的Alfv'{e}n速度。一个非常有趣的现象是，同一次CME的持续时间可以明显地分为A和B两个区间，库仑数分别为0.5以下和0.5以上。A（B）区间的$V_{α p}$和α-质子温度比的平均值分别为96.52（21.96）kms$^{-1}$和7.65（2.23）。这直接说明库仑碰撞在降低CMEs的非平衡态特征方面发挥了重要作用。我们的研究表明，CMEs 的绝对元素丰度也可能在其传播过程中发生变化。
{"title":"Alpha-Proton Differential Flow of A Coronal Mass Ejection at 15 Solar Radii","authors":"Xuechao Zhang, Hongqiang Song, Xiaoqian Wang, Leping Li, Hui Fu, Rui Wang, Yao Chen","doi":"arxiv-2409.10799","DOIUrl":"https://doi.org/arxiv-2409.10799","url":null,"abstract":"Alpha-proton differential flow ($V_{alpha p}$) of coronal mass ejections\u0000(CMEs) and solar wind from the Sun to 1 au and beyond could influence the\u0000instantaneous correspondence of absolute abundances of alpha particles\u0000(He$^{2+}$/H$^{+}$) between solar corona and interplanetary space as the\u0000abundance of a coronal source can vary with time. Previous studies based on\u0000Ulysses and Helios showed that $V_{alpha p}$ is negligible within CMEs from 5\u0000to 0.3 au, similar to slow solar wind ($<$ 400 km s$^{-1}$). However, recent\u0000new observations using Parker Solar Probe (PSP) revealed that the $V_{alpha\u0000p}$ of slow wind increases to $sim$60 km s$^{-1}$ inside 0.1 au. It is\u0000significant to answer whether the $V_{alpha p}$ of CMEs exhibits the similar\u0000behavior near the Sun. In this Letter, we report the $V_{alpha p}$ of a CME\u0000measured by PSP at $sim$15 $R_odot$ for the first time, which demonstrates\u0000that the $V_{alpha p}$ of CMEs is obvious and complex inside 0.1 au while\u0000keeps lower than the local Alfv'{e}n speed. A very interesting point is that\u0000the same one CME duration can be divided into A and B intervals clearly with\u0000Coulomb number below and beyond 0.5, respectively. The means of $V_{alpha p}$\u0000and alpha-to-proton temperature ratios of interval A (B) is 96.52 (21.96) km\u0000s$^{-1}$ and 7.65 (2.23), respectively. This directly illustrates that Coulomb\u0000collisions play an important role in reducing the non-equilibrium features of\u0000CMEs. Our study indicates that the absolute elemental abundances of CMEs also\u0000might vary during their propagation.","PeriodicalId":501423,"journal":{"name":"arXiv - PHYS - Space Physics","volume":"115 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142247668","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}
Praniti Singh, Shi Yan, Itamar J. Allali, JiJi Fan, Lingfeng Li
Orbits of celestial objects, especially the geocentric and heliocentric ones, have been well explored to constrain new long-range forces beyond the Standard Model (SM), often referred to as fifth forces. In this paper, for the first time, we apply the motion of a spacecraft around Jupiter to probe fifth forces that don't violate the equivalence principle. The spacecraft is the Juno orbiter, and ten of its early orbits already allow a precise determination of the Jovian gravitational field. We use the shift in the precession angle as a proxy to test non-gravitational interactions between Juno and Jupiter. Requiring that the contribution from the fifth force does not exceed the uncertainty of the precession shift inferred from data, we find that a new parameter space with the mass of the fifth-force mediator around $10^{-14}$ eV is excluded at 95% C.L.
{"title":"The Juno Mission as a Probe of Long-Range New Physics","authors":"Praniti Singh, Shi Yan, Itamar J. Allali, JiJi Fan, Lingfeng Li","doi":"arxiv-2409.10616","DOIUrl":"https://doi.org/arxiv-2409.10616","url":null,"abstract":"Orbits of celestial objects, especially the geocentric and heliocentric ones,\u0000have been well explored to constrain new long-range forces beyond the Standard\u0000Model (SM), often referred to as fifth forces. In this paper, for the first\u0000time, we apply the motion of a spacecraft around Jupiter to probe fifth forces\u0000that don't violate the equivalence principle. The spacecraft is the Juno\u0000orbiter, and ten of its early orbits already allow a precise determination of\u0000the Jovian gravitational field. We use the shift in the precession angle as a\u0000proxy to test non-gravitational interactions between Juno and Jupiter.\u0000Requiring that the contribution from the fifth force does not exceed the\u0000uncertainty of the precession shift inferred from data, we find that a new\u0000parameter space with the mass of the fifth-force mediator around $10^{-14}$ eV\u0000is excluded at 95% C.L.","PeriodicalId":501423,"journal":{"name":"arXiv - PHYS - Space Physics","volume":"10 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142268250","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}
Sophie Kadan, Xiao-Jia Zhang, Anton Artemyev, Yoshizumi Miyoshi, Ayako Matsuoka, Yoshiya Kasahara, Shoya Matsuda, Tomoaki Hori, Mariko Teramoto, Kazuhiro Yamamoto, Iku Shinohara
The latitudinal distribution of whistler-mode wave intensity plays a crucial role in determining the efficiency and energy of electrons scattered by these waves in the outer radiation belt. Traditionally, this wave property has mostly been derived from statistical measurements of off-equatorial spacecraft, which collect intensity data at various latitudes under different geomagnetic conditions and at different times. In this study we examine a set of events captured by both the near-equatorial THEMIS spacecraft and the off-equatorial ERG spacecraft. Specifically, we compare the whistler-mode wave intensity from THEMIS and ERG measurements at the same MLT and time sectors. Similar wave spectrum characteristics confirm that THEMIS and ERG indeed observed the same wave activity. However, upon closer examination of the wave intensity variations, we identify two distinct categories of events: those that follow the statistically predicted variations in wave intensity along magnetic latitudes, and those that exhibit rapid wave intensity decay away from the equatorial plane. We analyze main characteristics of events from both categories and discuss possible implications of our analysis for radiation belt models.
{"title":"Variation of Whistler-Mode Wave Characteristics Along Magnetic Field Lines: Comparison of Near-Equatorial THEMIS and Middle-Latitude ERG Observations","authors":"Sophie Kadan, Xiao-Jia Zhang, Anton Artemyev, Yoshizumi Miyoshi, Ayako Matsuoka, Yoshiya Kasahara, Shoya Matsuda, Tomoaki Hori, Mariko Teramoto, Kazuhiro Yamamoto, Iku Shinohara","doi":"arxiv-2409.09900","DOIUrl":"https://doi.org/arxiv-2409.09900","url":null,"abstract":"The latitudinal distribution of whistler-mode wave intensity plays a crucial\u0000role in determining the efficiency and energy of electrons scattered by these\u0000waves in the outer radiation belt. Traditionally, this wave property has mostly\u0000been derived from statistical measurements of off-equatorial spacecraft, which\u0000collect intensity data at various latitudes under different geomagnetic\u0000conditions and at different times. In this study we examine a set of events\u0000captured by both the near-equatorial THEMIS spacecraft and the off-equatorial\u0000ERG spacecraft. Specifically, we compare the whistler-mode wave intensity from\u0000THEMIS and ERG measurements at the same MLT and time sectors. Similar wave\u0000spectrum characteristics confirm that THEMIS and ERG indeed observed the same\u0000wave activity. However, upon closer examination of the wave intensity\u0000variations, we identify two distinct categories of events: those that follow\u0000the statistically predicted variations in wave intensity along magnetic\u0000latitudes, and those that exhibit rapid wave intensity decay away from the\u0000equatorial plane. We analyze main characteristics of events from both\u0000categories and discuss possible implications of our analysis for radiation belt\u0000models.","PeriodicalId":501423,"journal":{"name":"arXiv - PHYS - Space Physics","volume":"10 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142247634","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}
Low Mach number collisionless shocks are routinely observed in the solar wind and upstream of planetary bodies. However, most in situ observations have lacked the necessary temporal resolution to directly study the kinetic behavior of ions across these shocks. We investigate a series of five low Mach number bow shock crossings observed by the Magnetospheric Multiscale (MMS) mission. The five shocks had comparable Mach numbers, but varying shock-normal angles ($66^{circ} lesssim theta_{Bn} lesssim 89^{circ}$) and ramp widths ($5~mathrm{km} lesssim l lesssim 100~mathrm{km}$). The shock width is shown to be crucial in determining the fraction of protons reflected and energized by the shock, with proton reflection increasing with decreasing shock width. As the shock width increases proton reflection is arrested entirely. For nearly perpendicular shocks, reflected protons exhibit quasi-periodic structures, which persist far downstream of the shock. As the shock-normal angle becomes more oblique these periodic proton structures broaden to form an energetic halo population. Periodic fluctuations in the magnetic field downstream of the shocks are generated by fluctuations in dynamic pressure of alpha particles, which are decelerated by the cross-shock potential and subsequently undergo gyrophase bunching. These results demonstrate that complex kinetic-scale ion dynamics occur in low Mach number shocks, which depend significantly on the shock profile.
在太阳风和行星体上游经常观测到低马赫数的无碰撞冲击。然而，大多数现场观测都缺乏必要的时间分辨率来直接研究离子穿过这些冲击的动力学行为。我们研究了磁层多尺度（MMS）飞行任务观测到的一系列五个低马赫数弓形冲击穿越。这五个冲击的马赫数相当，但冲击法向角（66^{circ} lesssim theta_{Bn} lesssim 89^{circ}$）和斜坡宽度（5~mathrm{km} lesssim l lesssim 100~mathrm{km}$）各不相同。结果表明，冲击宽度对决定质子反射和被冲击激发的比例至关重要，质子反射随着冲击宽度的减小而增加。随着冲击宽度的增加，质子反射会完全停止。对于近乎垂直的冲击，反射质子呈现出准周期结构，这种结构在冲击下游很远的地方持续存在。当冲击-法向角变得越来越斜时，这些周期性质子结构就会扩大，从而形成一个高能卤群。冲击下游磁场的周期性波动是由α粒子的动态压力波动产生的，这些α粒子在跨冲击电势的作用下减速，随后在日格相束流作用下减速。这些结果表明，在低马赫数冲击中发生了复杂的动力学尺度离子动力学，这在很大程度上取决于冲击剖面。
{"title":"The Structure and Kinetic Ion Behavior of Low Mach Number Shocks","authors":"D. B. Graham, Yu. V. Khotyaintsev","doi":"arxiv-2409.09552","DOIUrl":"https://doi.org/arxiv-2409.09552","url":null,"abstract":"Low Mach number collisionless shocks are routinely observed in the solar wind\u0000and upstream of planetary bodies. However, most in situ observations have\u0000lacked the necessary temporal resolution to directly study the kinetic behavior\u0000of ions across these shocks. We investigate a series of five low Mach number\u0000bow shock crossings observed by the Magnetospheric Multiscale (MMS) mission.\u0000The five shocks had comparable Mach numbers, but varying shock-normal angles\u0000($66^{circ} lesssim theta_{Bn} lesssim 89^{circ}$) and ramp widths\u0000($5~mathrm{km} lesssim l lesssim 100~mathrm{km}$). The shock width is shown\u0000to be crucial in determining the fraction of protons reflected and energized by\u0000the shock, with proton reflection increasing with decreasing shock width. As\u0000the shock width increases proton reflection is arrested entirely. For nearly\u0000perpendicular shocks, reflected protons exhibit quasi-periodic structures,\u0000which persist far downstream of the shock. As the shock-normal angle becomes\u0000more oblique these periodic proton structures broaden to form an energetic halo\u0000population. Periodic fluctuations in the magnetic field downstream of the\u0000shocks are generated by fluctuations in dynamic pressure of alpha particles,\u0000which are decelerated by the cross-shock potential and subsequently undergo\u0000gyrophase bunching. These results demonstrate that complex kinetic-scale ion\u0000dynamics occur in low Mach number shocks, which depend significantly on the\u0000shock profile.","PeriodicalId":501423,"journal":{"name":"arXiv - PHYS - Space Physics","volume":"23 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142247669","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 new in situ measurements of the Solar Orbiter mission contribute to the knowledge of the suprathermal populations in the solar wind, especially of ions and protons whose characterization, although still in the early phase, seems to suggest a major involvement in the interaction with plasma wave fluctuations. Recent studies point to the stimulating effect of suprathermal populations on temperature anisotropy instabilities in the case of electrons already being demonstrated in theory and numerical simulations. Here, we investigate anisotropic protons, addressing the electromagnetic ion-cyclotron (EMIC) and the proton firehose (PFH) instabilities. Suprathermal populations enhance the high-energy tails of the Kappa velocity (or energy) distributions measured in situ, enabling characterization by contrasting to the quasi-thermal population in the low-energy (bi-)Maxwellian core. We use hybrid simulations to investigate the two instabilities (with ions or protons as particles and electrons as fluid) for various configurations relevant to the solar wind and terrestrial magnetosphere. The new simulation results confirm the linear theory and its predictions. In the presence of suprathermal protons, the wave fluctuations reach increased energy density levels for both instabilities and cause faster and/or deeper relaxation of temperature anisotropy. The magnitude of suprathermal effects also depends on each instability's specific (initial) parametric regimes. These results further strengthen the belief that wave-particle interactions govern space plasmas. These provide valuable clues for understanding their dynamics, particularly the involvement of suprathermal particles behind the quasi-stationary non-equilibrium states reported by in situ observations.
{"title":"Numerical simulations of temperature anisotropy instabilities stimulated by suprathermal protons","authors":"S. M. Shaaban, R. A. Lopez, M. Lazar, S. Poedts","doi":"arxiv-2409.09180","DOIUrl":"https://doi.org/arxiv-2409.09180","url":null,"abstract":"The new in situ measurements of the Solar Orbiter mission contribute to the\u0000knowledge of the suprathermal populations in the solar wind, especially of ions\u0000and protons whose characterization, although still in the early phase, seems to\u0000suggest a major involvement in the interaction with plasma wave fluctuations.\u0000Recent studies point to the stimulating effect of suprathermal populations on\u0000temperature anisotropy instabilities in the case of electrons already being\u0000demonstrated in theory and numerical simulations. Here, we investigate\u0000anisotropic protons, addressing the electromagnetic ion-cyclotron (EMIC) and\u0000the proton firehose (PFH) instabilities. Suprathermal populations enhance the\u0000high-energy tails of the Kappa velocity (or energy) distributions measured in\u0000situ, enabling characterization by contrasting to the quasi-thermal population\u0000in the low-energy (bi-)Maxwellian core. We use hybrid simulations to\u0000investigate the two instabilities (with ions or protons as particles and\u0000electrons as fluid) for various configurations relevant to the solar wind and\u0000terrestrial magnetosphere. The new simulation results confirm the linear theory\u0000and its predictions. In the presence of suprathermal protons, the wave\u0000fluctuations reach increased energy density levels for both instabilities and\u0000cause faster and/or deeper relaxation of temperature anisotropy. The magnitude\u0000of suprathermal effects also depends on each instability's specific (initial)\u0000parametric regimes. These results further strengthen the belief that\u0000wave-particle interactions govern space plasmas. These provide valuable clues\u0000for understanding their dynamics, particularly the involvement of suprathermal\u0000particles behind the quasi-stationary non-equilibrium states reported by in\u0000situ observations.","PeriodicalId":501423,"journal":{"name":"arXiv - PHYS - Space Physics","volume":"14 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142247672","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}
Tom Narock, Sanchita Pal, Aryana Arsham, Ayris Narock, Teresa Nieves-Chinchilla
Decades of in-situ solar wind measurements have clearly established the variation of solar wind physical parameters. These variable parameters have been used to classify the solar wind magnetized plasma into different types leading to several classification schemes being developed. These classification schemes, while useful for understanding the solar wind originating processes at the Sun and early detection of space weather events, have left open questions regarding which physical parameters are most useful for classification and how recent advances in our understanding of solar wind transients impact classification. In this work, we use neural networks trained with different solar wind magnetic and plasma characteristics to automatically classify the solar wind in coronal hole, streamer belt, sector reversal and solar transients such as coronal mass ejections comprised of both magnetic obstacles and sheaths. Furthermore, our work demonstrates how probabilistic neural networks can enhance the classification by including a measure of prediction uncertainty. Our work also provides a ranking of the parameters that lead to an improved classification scheme with ~96% accuracy. Our new scheme paves the way for incorporating uncertainty estimates into space weather forecasting with the potential to be implemented on real-time solar wind data.
{"title":"Classifying different types of solar wind plasma with uncertainty estimations using machine learning","authors":"Tom Narock, Sanchita Pal, Aryana Arsham, Ayris Narock, Teresa Nieves-Chinchilla","doi":"arxiv-2409.09230","DOIUrl":"https://doi.org/arxiv-2409.09230","url":null,"abstract":"Decades of in-situ solar wind measurements have clearly established the\u0000variation of solar wind physical parameters. These variable parameters have\u0000been used to classify the solar wind magnetized plasma into different types\u0000leading to several classification schemes being developed. These classification\u0000schemes, while useful for understanding the solar wind originating processes at\u0000the Sun and early detection of space weather events, have left open questions\u0000regarding which physical parameters are most useful for classification and how\u0000recent advances in our understanding of solar wind transients impact\u0000classification. In this work, we use neural networks trained with different\u0000solar wind magnetic and plasma characteristics to automatically classify the\u0000solar wind in coronal hole, streamer belt, sector reversal and solar transients\u0000such as coronal mass ejections comprised of both magnetic obstacles and\u0000sheaths. Furthermore, our work demonstrates how probabilistic neural networks\u0000can enhance the classification by including a measure of prediction\u0000uncertainty. Our work also provides a ranking of the parameters that lead to an\u0000improved classification scheme with ~96% accuracy. Our new scheme paves the way\u0000for incorporating uncertainty estimates into space weather forecasting with the\u0000potential to be implemented on real-time solar wind data.","PeriodicalId":501423,"journal":{"name":"arXiv - PHYS - Space Physics","volume":"75 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142247773","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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