Review of Mercury's Dynamic Magnetosphere: Post-MESSENGER Era and Comparative Magnetospheres

TL;DR

This review synthesizes current knowledge of Mercury's magnetosphere post-MESSENGER, compares it with other planets, and discusses future research opportunities with the upcoming BepiColombo mission.

Contribution

It provides a comprehensive overview of Mercury's magnetospheric dynamics, including recent findings and open questions, especially in light of new data from the MESSENGER mission and upcoming BepiColombo.

Findings

Frequent magnetic reconnection events depend on plasma beta and magnetic shear.

Mercury's magnetosphere responds dynamically to extreme solar events.

Particle energization mechanisms include Kelvin-Helmholtz waves and magnetic reconnection structures.

Abstract

This review summarizes the research of Mercury's magnetosphere in the Post-MESSENGER era and compares its dynamics to those in other planetary magnetospheres, especially to those in Earth's magnetosphere. This review starts by introducing the planet Mercury, including its interplanetary environment, magnetosphere, exosphere, and conducting core. The frequent and intense magnetic reconnection on the dayside magnetopause, which is represented by the flux transfer event "shower", is reviewed on how they depend on magnetosheath plasma beta and magnetic shear angle across the magnetopause, following by how they contribute to the flux circulation and magnetosphere-surface-exosphere coupling. In the next, the progress of Mercury's magnetosphere under extreme solar events, including the core induction and the reconnection erosion on the dayside magnetosphere, the responses of the nightside magnetosphere, are reviewed. Then, the dawn-dusk properties of the plasma sheet, including the features of the ions, the structure of the current sheet, and the dynamics of magnetic reconnection, are summarized. The last topic reviews the particle energization in Mercury's magnetosphere, which includes the energization of the Kelvin-Helmholtz waves on the magnetopause boundaries, reconnection-generated magnetic structures, and the cross-tail electric field. In each chapter, the last section discusses the open questions related with each topic, which can be considered by the simulations and the future spacecraft mission. We close by summarizing the future BepiColombo opportunities, which is a joint mission between ESA and JAXA, and is en route to Mercury.