Enhanced ion escape rate during IMF rotation under weak intrinsic magnetic field conditions on a Mars-like planet
Enhanced ion escape rate during IMF rotation under weak intrinsic magnetic field conditions on a Mars-like planet
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在类火星行星上弱固有磁场条件下 IMF 旋转过程中离子逃逸率增强
DOI：
10.1029/2022ja030510
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发表时间：
2023
期刊：
影响因子：
--
通讯作者：
Y.
中科院分区：
文献类型：
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作者：
Sakai;S.;Seki;K.;Terada;N.;Shinagawa;H.;Sakata;R.;Tanaka;T.;& Ebihara;Y.
行星际磁场 (IMF) 的旋转提供了逃逸机制的细节，该机制随着固有磁场和 IMF 之间的相互作用而变化。在类火星行星上，在弱固有磁场和 IMF 在 12 小时内旋转 180° 的条件下进行了多物种磁流体动力学模拟，这与日冕物质抛射 (CME) 时间尺度相当。在IMF从正北（平行于假设的固有磁场）旋转到正南（与假设的固有磁场反平行）的过程中，总离子逃逸率从∼5 × 1023s−1增加到∼3 × 1025s−1。当IMF从正北旋转到时钟角45°~75°时，逃逸率显着增加，然后缓慢增加，直到IMF旋转到正南。大幅增加的触发因素是磁层侧翼区域的多次重连，而后续的增加是由于重连区域扩展到赤道区域。除了侧面重新连接之外，电离层中的 IMF 质量负载也导致了 IMF 时钟角超过 90° 时的缓慢增加。 IMF 轮换是 CME 的一般特征。在 M 矮星附近运行的系外行星可能会经常受到 IMF 自转的影响，因为它们可能会暴露在日冕物质抛射环境中的严重恒星风中，目前的研究可能有助于未来计划的系外行星环境观测。
The rotation of the interplanetary magnetic field (IMF) provides details of the escape mechanism that varies with the interaction between the intrinsic magnetic field and the IMF. A multispecies magnetohydrodynamic simulation is conducted on a Mars‐like planet under the conditions of a weak intrinsic magnetic field and the IMF rotating by 180° over 12 hr, which is comparable to the coronal mass ejection (CME) time scale. The total ion escape rate increases from ∼5 × 1023s−1to ∼3 × 1025s−1during the IMF rotation from due north (parallel to the assumed intrinsic magnetic field) to due south (antiparallel to the assumed intrinsic magnetic field). The escape rate increases significantly with the IMF rotating from due north to clock angles of 45°–75°, followed by a gentle increase until the IMF rotates to due south. The trigger for the large increase is multiple reconnections in the magnetospheric flank region, and the subsequent increase is due to the expansion of the reconnection area into the equatorial region. The IMF mass loading in the ionosphere is also responsible for the gentle increase with IMF clock angles above 90° in addition to the flank reconnection. The IMF rotation is a general feature for a CME. Exoplanets orbiting in the vicinity of M‐dwarfs might be frequently affected by IMF rotation, as they could be exposed to severe stellar winds such as in CME environments, and the current study could be helpful for future planned observations of the exoplanetary environment.