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Ion distribution functions in magnetotail reconnection: Global hybrid-Vlasov simulation results
Annales Geophysicae ( IF 1.9 ) Pub Date : 2021-02-01 , DOI: 10.5194/angeo-2020-89 Andrei Runov , Maxime Grandin , Minna Palmroth , Markus Battarbee , Urs Ganse , Heli Hietala , Sanni Hoilijoki , Emilia Kilpua , Yann Pfau-Kempf , Sergio Toledo-Redondo , Lucile Turc , Drew Turner
Annales Geophysicae ( IF 1.9 ) Pub Date : 2021-02-01 , DOI: 10.5194/angeo-2020-89 Andrei Runov , Maxime Grandin , Minna Palmroth , Markus Battarbee , Urs Ganse , Heli Hietala , Sanni Hoilijoki , Emilia Kilpua , Yann Pfau-Kempf , Sergio Toledo-Redondo , Lucile Turc , Drew Turner
Abstract. We present results of noon–midnight meridional plane global hybrid-Vlasov simulations of the magnetotail ion dynamics under steady southward interplanetary magnetic field using the Vlasiator model. The simulation results show magnetotail reconnection and formation of earthward and tailward fast plasma outflows. The hybrid-Vlasov approach allows us to study ion velocity distribution functions (VDFs) that are self-consistently formed during the magnetotail evolution. We examine the VDFs collected by virtual detectors placed along the equatorial magnetotail within earthward and tailward outflows and around the quasi-steady X-line formed in the magnetotail at X ≈ −14 RE. This allows us to follow the evolution of VDFs during earthward and tailward motion of reconnected flux tubes as well as study signatures of unmagnetized ion motion in the weak magnetic field near the X-line. The VDFs indicate actions of Fermi-type and betatron acceleration mechanisms, ion acceleration by the reconnection electric field, and Speiser-type motion of ions near the X-line. The simulated VDFs are compared and show good agreement with VDFs observed in the magnetotail by the Time History of Events and Macroscale Interactions during Substorms (THEMIS) and Acceleration, Reconnection, Turbulence and Electrodynamics of Moon's Interaction with the Sun (ARTEMIS) spacecraft. We find that the VDFs become more gyrotropic but retain transverse anisotropy and counter-streaming ion beams when being convected earthward. The presented global hybrid-Vlasov simulation results are valuable for understanding physical processes of ion acceleration during magnetotail reconnection, interpretation of in-situ observations, and for future mission development by setting requirements on pitch-angle and energy resolution of upcoming instruments.
中文翻译:
磁尾重连中的离子分布函数:全局混合-Vlasov模拟结果
摘要。我们介绍了使用Vlasiator模型在稳定的南向行星际磁场下磁尾离子动力学的午午至午夜子午面全局混合Vlasov模拟的结果。仿真结果表明磁尾重连以及形成向地和向后快速等离子体流出。混合-Vlasov方法使我们能够研究在磁尾演化过程中自洽形成的离子速度分布函数(VDF)。我们检查了由虚拟探测器收集的VDF,这些探测器沿着赤道磁尾在地球的向后流出和向尾流出内以及在X≈-14 R E处在磁尾中形成的准稳定X线周围 。这使我们能够跟踪重新连接的通量管向地和向后运动期间VDF的演化,并研究X线附近弱磁场中未磁化离子运动的信号。VDF表示费米型和电子加速器加速机制的作用,通过重新连接电场进行的离子加速以及X线附近离子的Speiser型运动。对模拟的VDF进行了比较,并与亚暴期间事件和宏观相互作用的时间历史(THEMIS)以及月球与太阳相互作用的加速,重新连接,湍流和电动力学(ARTEMIS)观测到的磁尾中的VDF很好地吻合。我们发现,VDF旋转性更高,但在对流向地面时仍保持横向各向异性和逆流离子束。
更新日期:2021-02-01
中文翻译:
磁尾重连中的离子分布函数:全局混合-Vlasov模拟结果
摘要。我们介绍了使用Vlasiator模型在稳定的南向行星际磁场下磁尾离子动力学的午午至午夜子午面全局混合Vlasov模拟的结果。仿真结果表明磁尾重连以及形成向地和向后快速等离子体流出。混合-Vlasov方法使我们能够研究在磁尾演化过程中自洽形成的离子速度分布函数(VDF)。我们检查了由虚拟探测器收集的VDF,这些探测器沿着赤道磁尾在地球的向后流出和向尾流出内以及在X≈-14 R E处在磁尾中形成的准稳定X线周围 。这使我们能够跟踪重新连接的通量管向地和向后运动期间VDF的演化,并研究X线附近弱磁场中未磁化离子运动的信号。VDF表示费米型和电子加速器加速机制的作用,通过重新连接电场进行的离子加速以及X线附近离子的Speiser型运动。对模拟的VDF进行了比较,并与亚暴期间事件和宏观相互作用的时间历史(THEMIS)以及月球与太阳相互作用的加速,重新连接,湍流和电动力学(ARTEMIS)观测到的磁尾中的VDF很好地吻合。我们发现,VDF旋转性更高,但在对流向地面时仍保持横向各向异性和逆流离子束。