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Enhanced carbon dioxide causing the dust storm‐related increase in high‐altitude photoelectron fluxes at Mars
Author(s) -
Xu Shaosui,
Liemohn Michael,
Bougher Stephen,
Mitchell David
Publication year - 2015
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2015gl066043
Subject(s) - atmospheric sciences , martian , mars exploration program , altitude (triangle) , atmosphere of mars , effects of high altitude on humans , atmosphere (unit) , environmental science , dust storm , x ray photoelectron spectroscopy , storm , photoelectric effect , astrobiology , physics , meteorology , optics , geometry , mathematics , nuclear magnetic resonance
Several studies have shown that the Martian global dust storm occurred in 2001 had a long‐term influence on high‐altitude photoelectron fluxes by analyzing the observations of the magnetometer/electron reflectometer instrument on board Mars Global Surveyor, most likely because the dust altered the neutral atmosphere in a significant way in terms of photoelectron production and loss. This study investigates candidate atmospheres that can replicate observations, especially focusing on the role that thermospheric composition and density play in high‐altitude photoelectrons. Through the simulations of our SuperThermal Electron Transport model, it is found that high‐altitude photoelectron fluxes at more field‐aligned pitch angles are very sensitive to composition change and surprisingly independent of density. For more perpendicular pitch angles, both composition and density take part in determining photoelectron fluxes. Also, a CO 2 atmosphere is the only one of the tested atmospheres that can qualitatively match the observation, which suggests that the global dust storm might have altered the photoelectron fluxes via causing CO 2 to be the dominant species at a much larger altitude range than usual.