Magnetic Topology Response to the 2003 Halloween ICME Event at Mars

Abstract

AbstractUnderstanding how the Mars plasma environment responds to space weather events provides insights into the early Sun‐Mars interaction and helps constrain the extrapolation of atmospheric loss back in time. The 2003 Halloween interplanetary coronal mass ejection (ICME) event is one of the most extreme space weather events encountered by Mars during the last two decades. Mars Global Surveyor's circular orbit at ∼400 km allows us to observationally study the magnetic topology response to this extreme event globally for the first time. We analyze the suprathermal electron data and magnetic field measurements from Mars Global Surveyor to infer magnetic topology before, during, and after this ICME event and quantify the variation of the topology over both weak and strong crustal regions and correlate the variation with the upstream dynamic pressure. Over weak crustal regions, more draped field lines and fewer closed field lines are observed under high dynamic pressures, implying a deeper interplanetary magnetic field penetration during the ICME event. Over dayside strong crustal regions, the dominant magnetic topology switches from closed field lines during quiet periods to open field lines during disturbed periods, suggesting more reconnection occurring between the crustal magnetic fields and interplanetary magnetic field. This mixed magnetic topological response is consistent with predictions from magnetohydrodynamic simulations for ICME events in previous studies.