A Double-Disturbed Lunar Plasma Wake

<p>Under nominal solar wind conditions, a low density wake region forms downstream of the nightside lunar surface. &#160;However, the lunar plasma environment undergoes a transformation as the Moon passes through the Earth&#8217;s magnetotail, with the warm plasma typically not having a strong flow, and thus the wake structure disappears. &#160;However, while in the tail, there can be a sudden intense change due to solar-driven events such as coronal mass ejections. &#160;With a new planned human presence on the Moon, it is important to understand the near-surface plasma environment&#8217;s response to these extreme conditions. &#160;We investigate the response of the lunar wake to a passing coronal mass ejection on 2012 March 8 while crossing the Earth&#8217;s magnetotail using both a large-scale MHD model of the Earth&#8217;s global magnetosphere and smaller-scale 3-D hybrid-PIC simulations.</p><p>The CME plasma shock was detected by the Wind spacecraft around 10:30 UT and in the Earth&#8217;s magnetotail around 11:20 UT by the ARTEMIS spacecraft in lunar orbit. &#160;Wind observations are used as time-dependent up-stream conditions for a 24-hour global magnetosphere MHD simulation run through NASA&#8217;s Community Coordinated Modeling Center using the OpenGGCM model. &#160;Extracted plasma parameters from the ARTEMIS spacecraft following the plasma shock are used as upstream static boundary conditions for hybrid-PIC simulations using the AMITIS code.</p><p>Results for the hybrid-PIC lunar wake simulations performed during a momentary jump in magnetotail plasma velocity and density show a short misaligned plasma void relative to nominal SW conditions. &#160;MHD results indicate that changes near the Moon appear as a result of a warped magnetopause boundary moving inward after 11:00 UT, causing the Moon to enter the magnetosheath. &#160;These results also show a number of plasmoids developing and propagating down the tail, including one seen at 11:20 UT that corresponds temporarily with plasmoid-like features in the ARTEMIS magnetic field profiles.</p>