Effects of the Crustal Magnetic Fields and Changes in the IMF Orientation on the Magnetosphere of Mars: MAVEN Observations and LatHyS Results

Abstract

The Mars Atmosphere and Volatile EvolutioN Mission (MAVEN) is currently probing the complex Martian environment. Although main structures arising from the interaction between the solar wind (SW) and the induced magnetosphere of Mars can be described using a steady state picture, time‐dependent physical processes modify the response of this obstacle. These processes result from temporal variabilities in the internal and/or external electromagnetic fields and plasma properties. Indeed, the crustal magnetic fields (CF) rotation constantly modifies the intrinsic magnetic field topology relative to the SW. Moreover, the magnetosphere's state is also modified by changes in the interplanetary magnetic field (IMF). In this work we analyze MAVEN magnetic field and plasma measurements obtained on 23 December 2014, between 06:00 UT and 14:15 UT. These measurements suggest that the external conditions remained approximately constant when MAVEN was inside the magnetosphere during the first orbit. In contrast, MAVEN observed changes in the IMF orientation before visiting the magnetosphere during the second orbit. To investigate the response of the Martian plasma environment to the CF rotation and IMF variability, we also perform hybrid simulations, using MAVEN observations to set SW external conditions. Simulation results are compared with the MAVEN measurements and show good agreement. Associated recovery timescales of different magnetospheric regions are found to range between ∼ 10 s and ∼ 10 min. Finally, we do not observe large variability in the total planetary H+ and O+ escape rates at different times during this event, although a correlation between the latter and the CF location is identified.

Recovery Timescales of the Dayside Martian Magnetosphere to IMF Variability

“…We study the O + plume recovery process up to X MSO =−2.30 R M so that, together with the results by Romanelli, Modolo, Leblanc, Chaufray, Hess, et al. (), we provide a description of the magnetosphere and O + plume recovery between X MSO =1 R M and X MSO =−2.30 R M .…”

“…Geophysical Research Letters similar to that of the upstream IMF, given that a new magnetic field configuration consistent with such external condition must be achieved. Comparison between Figure 2 and Figure 9 of Romanelli, Modolo, Leblanc, Chaufray, Hess, et al (2018) shows that differences in the adaptation of a given (fixed) annular region are drastically more important between the X MSO =1R M and X MSO =−1R M planes than outside from this region.…”

“…Specifically, in this work we further analyze the simulation results presented by Romanelli, Modolo, Leblanc, Chaufray, Hess, et al. () when MAVEN observed an IMF rotation in the upstream SW on 23 December 2014, between 10:43 and 10:49 UT. Romanelli, Modolo, Leblanc, Chaufray, Hess, et al.…”

“…Crustal magnetic fields at Mars (Acuña et al, 1999) are described using the model derived in Cain et al (2003). A detailed description of the LatHyS model and the time-dependent simulation presented here can be found in Modolo (2016) and Romanelli, Modolo, Leblanc, Chaufray, Hess, et al (2018), respectively.…”

“…This procedure allows us to estimate the O + plume recovery timescales by studying the evolution of r CM , the mean convective electric field upstream from the bow shock in the same spatial region, and the angle between them, as a function of time and X MSO . We study the O + plume recovery process up to X MSO =−2.30 R M so that, together with the results by Romanelli, Modolo, Leblanc, Chaufray, Hess, et al (2018), we provide a description of the magnetosphere and O + plume recovery between X MSO =1R M and X MSO =−2.30R M . Figure 3a shows the clock angle associated with r CM (blue curve) and the convective electric field (red curve) as a function of time, for two different X MSO planes at X MSO =1R M and X MSO =−2.30R M .…”