Ion Jets Within Current Sheets in the Martian Magnetosphere
Ion Jets Within Current Sheets in the Martian Magnetosphere
复制标题
DOI：
10.1029/2020ja028576
复制
发表时间：
2020-11
期刊：
影响因子：
--
通讯作者：
Y. Harada;J. Halekas;Shaosui Xu;G. DiBraccio;S. Ruhunusiri;T. Hara;J. Mcfadden;J. Espley;D. Mitchell;C. Mazelle
中科院分区：
文献类型：
--
作者：
Y. Harada;J. Halekas;Shaosui Xu;G. DiBraccio;S. Ruhunusiri;T. Hara;J. Mcfadden;J. Espley;D. Mitchell;C. Mazelle
磁重联经常被认为与在火星复杂的磁层中观察到的各种动力学现象有关。我们提出了第一个全球调查的离子射流电流片内，这被认为是磁重联的主要产品，火星大气和挥发性演变（MAVEN）的数据在火星磁层的昼侧和夜侧。我们开发了一种全自动的算法，以有效和可靠地识别离子流速度偏差，在当前片交叉记录的MAVEN。所获得的统计结果表明，（i）在火星的昼侧和夜侧磁层中，通常广泛地观察到嵌入电流片内的向阳和反向阳离子喷流，（ii）在喷流交叉期间测量的磁场剖面和推断的磁拓扑结构通常与重新连接电流片的预期一致，（iii）喷流发生显然与上游驱动条件无关，和（iv）大多数已识别的电流片都很薄，大约为离子尺度的半厚度，并嵌入低β等离子体中，这表明它们似乎能够根据已知的起始条件重新连接。离子喷流的广泛分布和常见探测，以及薄的、低β电流片的普遍存在，意味着磁重联可能在火星周围的许多地方频繁发生，从而在火星磁层的动力学中发挥重要作用，即使不是全部，也是大多数的太阳风条件。
Magnetic reconnection is often suggested to be implicated in a variety of dynamic phenomena observed in the complex magnetosphere of Mars. We present a first global survey of ion jets within current sheets, which are thought of as a primary product of magnetic reconnection, with Mars Atmosphere and Volatile EvolutioN (MAVEN) data obtained on the dayside and nightside in the Martian magnetosphere. We develop a fully automated algorithm to efficiently and reliably identify ion flow velocity deviations during current sheet crossings recorded by MAVEN. The obtained statistical results show that (i) sunward and anti‐sunward ion jets embedded within current sheets are commonly and widely observed in the dayside and nightside magnetosphere of Mars, (ii) measured magnetic field profiles and inferred magnetic topology during the jet crossings are generally consistent with those expected for reconnecting current sheets, (iii) the jet occurrence is apparently independent of upstream driver conditions, and (iv) most of the identified current sheets are thin with a roughly ion scale half‐thickness and are embedded in low beta plasma, suggesting that they are seemingly capable of reconnection based on the known onset conditions. The widespread distributions and common detection of ion jets, as well as the ubiquitous presence of thin, low‐beta current sheets, imply that magnetic reconnection could operate frequently in many locations around Mars, thereby playing an important role in the dynamics of the Martian magnetosphere for most, if not all, of the solar wind conditions in the present epoch.