Open AccessEscape rates and variability constraints for high‐energy sodium sources at Mercury
Author(s) -
Schmidt Carl A.,
Baumgardner Jeffrey,
Mendillo Michael,
Wilson Jody K.
Publication year - 2012
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2011ja017217
Subject(s) - exosphere , mercury (programming language) , physics , astrobiology , micrometeoroid , astronomy , ion , quantum mechanics , space debris , computer science , spacecraft , programming language
We present a 3‐D time‐dependent modeling of Mercury's extended sodium exosphere in the region of the distant tail. Recent simulations in support of the MESSENGER and BepiColombo missions have shown spatial distributions in Mercury's exosphere can be linked to specific source processes. Our model builds upon these efforts by concentrating on the escaping component of Mercury's surface‐bound exosphere to assess the wide‐field (7°) data described in the studies by Baumgardner et al. (2008) and Schmidt et al. (2010). Escape rates of several source processes in Mercury's exosphere are determined, and the effects of orbital motion, surface‐gas interactions, variable source rates, and spatially heterogeneous sources are explored. Our simulations demonstrate that both photon‐stimulated desorption and micrometeoroid impacts can result in a ∼20% loss of Mercury's sodium atmosphere, depending on orbital phase, and are jointly responsible for the observed comet‐like tail as driven by solar radiation pressure. For a constant supply of both these sources into the exosphere, the modeled average column density over Mercury's disc decreases by ∼1/3 at 70° true anomaly (the orbital position for peak escape), consistent with observations over many orbits.