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Ecliptic North‐South Symmetry of Hydrogen Geocorona
Author(s) -
Kameda S.,
Ikezawa S.,
Sato M.,
Kuwabara M.,
Osada N.,
Murakami G.,
Yoshioka K.,
Yoshikawa I.,
Taguchi M.,
Funase R.,
Sugita S.,
Miyoshi Y.,
Fujimoto M.
Publication year - 2017
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 - 10.1002/2017gl075915
Subject(s) - exosphere , physics , hydrogen , flux (metallurgy) , plasmasphere , radiation pressure , astrobiology , atmosphere (unit) , astronomy , astrophysics , geophysics , magnetic field , magnetosphere , materials science , meteorology , ion , quantum mechanics , metallurgy
Abstract The hydrogen exosphere constitutes the uppermost atmospheric layer of the Earth, and its shape may reflect the last stage of the atmospheric escape process. The distribution of hydrogen in the outer exosphere remains unobserved because outer geocoronal emissions are difficult to observe from within the exosphere. In this study, we used the Lyman Alpha Imaging Camera on board the Proximate Object Close Flyby with Optical Navigation spacecraft, located outside the exosphere, to obtain the first image of the entire geocorona that extends to more than 38 Earth radii. The observed emission intensity distribution can be reproduced using our analytical model that has three parameters: exobase temperature, exobase density, and solar radiation pressure, which implies that hot hydrogen production in the magnetized plasmasphere is not the dominant process shaping the outer hydrogen exosphere. However, the role of the magnetic effect in determining the total escape flux cannot be ruled out.