P088-01
A transient enhancement of Mercury’s exosphere observed at extremely high altitudes in the solar wind

Thursday, 17 December 2020: 04:00
Virtual
Jamie Matthew Jasinski1, Leonardo Regoli2, Tim Cassidy3, Ryan M. Dewey4, Jim M Raines4, James A Slavin5, Andrew J Coates6, Daniel J Gershman7, Tom Nordheim1 and Neil Murphy8, (1)NASA Jet Propulsion Laboratory, Pasadena, CA, United States, (2)Mullard Space Science Laboratory, Dorking, United Kingdom, (3)University of Colorado Boulder, Boulder, CO, United States, (4)University of Michigan, Ann Arbor, MI, United States, (5)University of Michigan Ann Arbor, Department of Climate and Space Sciences and Engineering, Ann Arbor, MI, United States, (6)University College London, Mullard Space Science Laboratory, London, United Kingdom, (7)NASA Goddard Space Flight Center, Greenbelt, MD, United States, (8)JPL, Pasadena, CA, United States
Recorded Presentation
Abstract:
Mercury has a tenuous exosphere, which is supplied by particles released from its surface. This exosphere is closely bound to Mercury, with measured densities of 10-2 cm-3 at ~1500 km. We report on the first inferred enhancement of neutral sodium and silicon densities (<103 cm-3) at high altitudes of ~5300 km by the MESSENGER spacecraft. The Fast-Imaging Plasma Spectrometer (FIPS) detected sodium-group ions that were recently ionized, and “picked up” by the solar wind (SW). We estimate that the neutral density required to produce the observed pickup ion fluxes is similar to typical exospheric densities found at ~700 km altitudes and therefore the global exosphere cannot account for these high-altitude observations. Only an impact by a micrometeroid could eject these particles at high enough velocities to be observed at extreme high altitudes. Understanding micrometeoroid impacts is critical to understanding the source processes of the exosphere at Mercury, and the use of plasma spectrometers will be crucial for future observations with the Bepi-Colombo mission at Mercury.
Previous Abstract | Next Abstract >>