Response of the Martian Ionosphere to Solar Activity including SEPs and ICMEs in a two week period starting on 25 February 2015

TL;DR

This study analyzes how solar activity, including SEPs and ICMEs, affects Mars's ionosphere over two weeks in 2015, revealing increased ionization, plasma transport, and ion escape rates during solar disturbances.

Contribution

It provides detailed observations of Mars's ionospheric response to ICMEs and SEPs, highlighting ionization and plasma escape mechanisms during solar events.

Findings

Increased electron densities during ICMEs.

Enhanced ion escape rates of 10^25 - 10^26 s^-1.

Correlation between solar activity and ionospheric disturbances.

Abstract

In a two-week period between February and March of 2015, a series of interplanetary coronal mass ejections (ICMEs) and (solar energetic particles) SEPs made contact with Mars. The interactions were observed by several spacecraft, including Mars Express (MEX), Mars Atmosphere and Volatile Evolution Mission (MAVEN), and Mars Odyssey (MO). The ICME disturbances were characterized by an increase in ion speed, plasma temperature, magnetic field magnitude, and energetic electron flux. Furthermore, increased solar wind density and speeds, unusually high local electron densities and high flow velocities were detected on the nightside at high altitudes during the March 8th event. These effects are thought to be due to the transport of ionospheric plasma away from Mars. The peak electron density at periapsis shows a substantial increase, reaching number densities about 2.7 x 104 cm-3 during the second ICME in the deep nightside, which corresponds to an increase in the MOHigh-Energy Neutron Detector flux, suggesting an increase in the ionization of the neutral atmosphere due to the high intensity of charged particles. SEPs show a substantial enhancement before the shock of fourth ICME causing impact ionization and absorption of the surface echo intensity which drops to the noise levels. Moreover, the peak ionospheric density exhibits a discrete enhancement over a period of about 30 hrs around the same location, which maybe due to impact ionization. Ion escape rates at this time are calculated to be in the order of 1025 - 1026 s-1, consistent with MAVEN results, but somewhat higher.