MESSENGER observations of planetary ion enhancements at Mercury's northern magnetospheric cusp during Flux Transfer Event Showers
Weijie Sun, James A. Slavin, Anna Milillo, Ryan M. Dewey, Stefano Orsini, Xianzhe Jia, Jim M. Raines, Stefano Livi, Jamie M. Jasinski, Suiyan Fu, Jiutong Zhao, … 展开作者
Weijie Sun, James A. Slavin, Anna Milillo, Ryan M. Dewey, Stefano Orsini, Xianzhe Jia, Jim M. Raines, Stefano Livi, Jamie M. Jasinski, Suiyan Fu, Jiutong Zhao, Qiu-Gang Zong, Yoshifumi Saito, Changkun Li
备注：
34 pages, 10 figures, 1 table
发表信息：
Journal of Geophysical Research: Space Physics, 127, e2022JA030280 (2022)
At Mercury, several processes can release ions and neutrals out of the planet's surface. Here we present enhancements of dayside planetary ions in the solar wind entry layer during flux transfer event (FTE) "showers" near Mercury's northern magnetospheric cusp. The FTE showers correspond to the intervals of intense magnetopause reconnection of Mercury's magnetosphere, which form a solar wind entry layer equatorward of the magnetospheric cusps. In this entry layer, solar wind ions are accelerated and move downward (i.e. planetward) toward the cusps, which sputter upward-moving planetary ions within 1 minute. The precipitation rate is enhanced by an order of magnitude during FTE showers and the neutral density of the exosphere can vary by >10% due to this FTE-driven sputtering. These in situ observations of enhanced planetary ions in the entry layer likely correspond to an escape channel of Mercury's planetary ions, and the large-scale variations of the exosphere observed on minute-timescales by Earth observatories. Comprehensive, future multi-point measurements made by BepiColombo will greatly enhance our understanding of the processes contributing to Mercury's dynamic exosphere and magnetosphere.
This review summarizes the research of Mercury's magnetosphere in the Post-MESSENGER era and compares its dynamics to those in other planetary magnetospheres, especially to those in Earth's magnetosphere. This review starts by introducing the planet Mercury, including its interplanetary environment, magnetosphere, exosphere, and conducting core. The frequent and intense magnetic reconnection on the dayside magnetopause, which is represented by the flux transfer event "shower", is reviewed on how they depend on magnetosheath plasma beta and magnetic shear angle across the magnetopause, followin…
The large-scale magnetic structure of interplanetary coronal mass ejections (ICMEs) has been shown to cause decreases in the galactic cosmic ray (GCR) flux measured in situ by spacecraft, known as Forbush decreases (Fds). We use measurements of the GCR count rate obtained by MESSENGER during its orbital phase around Mercury to identify such Fds related to the passage of ICMEs and characterize their structure. Of the 42 ICMEs with corresponding high-quality GCR data, 79% are associated with a Fd. Thus a total of 33 ICME-related Fds were identified, 24 of which (73%) have a two-step structure. W…
Mercury and frame-dragging in light of the MESSENGER flybys: conflict with general relativity, poor knowledge of the physical properties of the Sun, data reduction artifact, or still insufficient observations?
广义相对论利用日震学中太阳的角动量S = 190 x 10^39 kg m^2 s^-1，预测水星近日点经度的兰斯-瑟林岁差为-2.0毫角秒/世纪（在天体赤道参考系中计算）。在4-σ水平上，它与标准牛顿/爱因斯坦岁差的0.4 +/- 0.6毫角秒/世纪修正值不一致，只要后者完全归因于标架拖曳。补充岁差是最近用INPOP 10a星历表与一个长行星数据记录（1914-2010年）进行全球拟合确定的，其中包括2008-2009年从信使号航天器收集的3个数据点。INPOP 10a模型根本不包括太阳重力磁场，因此它的特征可能在数据简化过程中被部分删除。另一方面，Lense-Thirring进动可能在一定程度上被竞争进动所抵消，这些竞争进动是由太阳四极质量矩和PPN参数β进入Schwarzschild类1 PN进动的小错误建模引起的，两者都是在INPOP 10a中建模的。相反，水星本身的扁率对其近日点的影响可以忽略不计。最大的单个小行星和小行星环的错误模型行为也是如此。未来对目前正在进行的信使号任务的更多观测结果的分析将进一步阐明这一问题，如果得到证实，可能会挑战我们目前对目前公认的引力定律和/或太阳物理特性的看法。
Mercury's magnetosphere is known to be affected by enhanced ram pressures and magnetic fields inside interplanetary coronal mass ejections (ICMEs). Here we report detailed observations of an ICME compressing Mercury's dayside magnetosphere to the surface. A fast CME launched from the Sun on November 29 2013 impacted first MESSENGER, which was orbiting Mercury, on November 30 and later STEREO-A near 1 AU on December 1. Following the ICME impact, MESSENGER remained in the solar wind as the spacecraft traveled inwards and northwards towards Mercury's surface until it reached and passed its closes…
MESSENGER has observed a lot of dawn-dusk asymmetries in Mercury's magnetotail, such as the asymmetries of the cross-tail current sheet thickness and the occurrence of flux ropes, dipolarization events and energetic electron injections. In order to obtain a global pictures of Mercury's magnetotail dynamics and the relationship between these asymmetries, we perform global simulations with the magnetohydrodynamics with embedded particle-in-cell (MHD-EPIC) model, where Mercury's magnetotail region is covered by a PIC code. Our simulations show that the dawnside current sheet is thicker, the plasm…
Our knowledge of the properties of Coronal Mass Ejections (CMEs) in the inner heliosphere is constrained by the relative lack of plasma observations between Sun and 1 AU. In this work, we present a comprehensive catalog of 47 CMEs measured in situ measurements by two or more radially aligned spacecraft (MESSENGER, Venus Express, STEREO or Wind/ACE). We estimate the CME impact speeds at Mercury and Venus using a drag-based model and present an average propagation profile of CMEs (speed and deceleration/acceleration) in the inner heliosphere. We find that CME deceleration continues past Mercury'…
The predicted Lense-Thirring perihelion precession of Mercury induced by the Sun's angular momentum through its general relativistic gravitomagnetic field amounts to 2 milliarcseconds per century. It turned out to be compatible with the latest experimental determinations of the supplementary perihelion precession of Mercury with the INPOP15a ephemerides, whose accuracy level has nowadays reached the magnitude of the predicted relativistic effect itself thanks to the analysis of some years of tracking data of the MESSENGER spacecraft, which orbited Mercury from 2011 to 2015. A dedicated analysi…
Hot flow anomalies (HFAs) represent a subset of solar wind discontinuities interacting with collisionless bow shocks. They are typically formed when the normal component of motional (convective) electric field points toward the embedded current sheet on at least one of its sides. The core region of an HFA contains hot and highly deflected ion flows and rather low and turbulent magnetic field. In this paper, we report first observations of HFA-like events at Mercury identified over a course of two planetary years. Using data from the orbital phase of the MErcury Surface, Space ENvironment, GEoc…
For the first time, we explore the tightly coupled interior-magnetosphere system of Mercury by employing a three-dimensional ten-moment multifluid model. This novel fluid model incorporates the non-ideal effects including the Hall effect, inertia, and tensorial pressures that are critical for collisionless magnetic reconnection; therefore, it is particularly well suited for investigating $collisionless$ magnetic reconnection in Mercury's magnetotail and at the planet's magnetopause. The model is able to reproduce the observed magnetic field vectors, field-aligned currents, and cross-tail curre…
The planet Mercury possesses a small but highly dynamic magnetosphere in which the role and dynamics of electrons are still largely unknown. We aim at modeling the global dynamics of solar wind electrons impinging on Mercury's magnetosphere. Particular relevance is given to local acceleration processes and the global circulation patterns. The goals of this work are pursued by means of three-dimensional, fully kinetic particle-in-cell simulations modeling the interaction of the solar wind with the Hermean magnetosphere. This method allows a self-consistent representation of the plasma dynamics …
In this review we discuss all the relevant solar/stellar radiation and plasma parameters and processes that act together in the formation and modification of atmospheres and exospheres that consist of surface-related minerals. Magma ocean degassed silicate atmospheres or thin gaseous envelopes from planetary building blocks, airless bodies in the inner Solar System, and close-in magmatic rocky exoplanets such as CoRot-7b, HD219134b and 55 Cnc e are addressed. The depletion and fractionation of elements from planetary embryos, which act as the building blocks for protoplanets are also discussed…
The aim of this study is to simulate the interaction of the solar wind with the Hermean magnetosphere when the interplanetary magnetic field is weak, performing a parametric study for all the range of hydrodynamic values of the solar wind predicted on Mercury for the ENLIL + GONG WSA + Cone SWRC model: density from $12$ to $180$ cm$^{-3}$, velocity from $200$ to $500$ km/s and temperatures from $2 \cdot 10^4$ to $18 \cdot 10^4$ K, and compare the results with a real MESSENGER orbit as reference case. We use the code PLUTO in spherical coordinates and an asymmetric multipolar expansion for the …
Properties and Radial Evolution of Solar Wind Turbulence Near Mercury's Orbit
Boston University（波士顿大学）；Institute for Advanced Study, Princeton（普林斯顿高等研究院）；Laboratoire de Physique des Plasmas (LPP), CNRS, Observatoire de Paris, Sorbonne Université, Université Paris Saclay, Ecole polytechnique, Institut Polytechnique de Paris（等离子体物理实验室（LPP），法国国家科学研究中心，巴黎天文台，索邦大学，巴黎萨克雷大学，巴黎综合理工学院，巴黎理工学院）；University of Michigan（密歇根大学）
We study interplanetary coronal mass ejections (ICMEs) measured by probes at different heliocentric distances (0.3-1AU) to investigate the propagation of ICMEs in the inner heliosphere and determine how the generic features of ICMEs change with heliospheric distance. Using data from the MESSENGER, Venus Express and ACE spacecraft, we analyze with the superposed epoch technique the profiles of ICME substructures, namely the sheath and the magnetic ejecta. We determine that the median magnetic field magnitude in the sheath correlates well with ICME speeds at 1 AU and we use this proxy to order t…
The aim of this research is to simulate the interaction of the solar wind with the magnetic field of Mercury and to study the particle fluxes between the magnetosheath and the planet surface. We simulate the magnetosphere structure using the open source MHD code PLUTO in spherical geometry with a multipolar expansion of the Hermean magnetic field (Anderson, B. J. et al, 2012). We perform two simulations with realistic solar wind parameters to study the properties of a plasma stream originated in the reconnection region between the interplanetary and the Hermean magnetic field. The plasma preci…
We present the first statistical analysis of complexity changes affecting the magnetic structure of interplanetary coronal mass ejections (ICMEs), with the aim of answering the questions: How frequently do ICMEs undergo magnetic complexity changes during propagation? What are the causes of such changes? Do the in situ properties of ICMEs differ depending on whether they exhibit complexity changes? We consider multi-spacecraft observations of 31 ICMEs by MESSENGER, Venus Express, ACE, and STEREO between 2008 and 2014 while radially aligned. By analyzing their magnetic properties at the inner an…
