Enhanced energization of plume ions around Mars from interplanetary shocks

¹ Institute for Frontiers in Astronomy and Astrophysics, Beijing Normal University, Beijing 102206, PR China
e-mail: jpguo@bnu.edu.cn; guojpguo@gmail.com
² Planetary and Space Physics Group, Department of Astronomy, Beijing Normal University, Beijing 100875, PR China
³ Gravitational Wave and Cosmology Laboratory, Department of Astronomy, Beijing Normal University, Beijing, 100875, PR China
⁴ Advanced Institute of Natural Sciences, Beijing Normal University, Zhuhai, 519087, PR China
⁵ Key Laboratory of Earth and Planetary Physics, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, PR China
⁶ Heilongjiang Mohe Observatory of Geophysics, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, PR China
⁷ College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing 100049, PR China

Received: 13 April 2023
Accepted: 1 October 2023

Abstract

Heavy ions escaping Mars along the solar wind electric field direction are often referred to as an “ion plume”. This phenomenon represents one of the major ion escape channels on Mars. Spacecraft observations have indicated that the global average of escaping ion fluxes, derived with the aid of models, can be increased by an order of magnitude or more in response to strong solar events. In particular, it has been reported that interplanetary (IP) shocks produce high-energy escaping ion plumes. However, the ion acceleration mechanisms associated with the shock arrival have not yet been fully elucidated. During the passage of an IP shock on Mars on March 3, 2015, the plume O⁺ ions continuously entered the narrow field of view (FoV) of STATIC on board the MAVEN spacecraft, thanks to favorable FoV configurations. This event provides a unique opportunity to identify plume ion energization processes associated with the shock arrival. Our analysis suggests that the enhanced energization of the plume O⁺ ions is mainly due to the enhanced convection electric field caused by the IP shock compression. This finding provides a crucial clue towards the understanding of how IP shocks facilitate ion escape through the plume.