Open AccessExospheric dynamics of hydrogen and deuterium at solar minimum
Author(s) -
Hodges R. Richard
Publication year - 1998
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 - 10.1029/97ja02875
Subject(s) - exosphere , thermosphere , deuterium , hydrogen , astrobiology , flux (metallurgy) , physics , atmospheric escape , atmospheric sciences , eddy diffusion , troposphere , atomic physics , chemistry , geophysics , meteorology , ionosphere , mars exploration program , ion , turbulence , organic chemistry , quantum mechanics
The escape of hydrogen and deuterium from the Earth is regulated by eddy transport of hydrogenic gases (e.g., water vapor, methane, and molecular hydrogen) from the troposphere, through the stratosphere, and into the mesosphere and lower thermosphere where photochemistry produces atomic forms of hydrogen and deuterium. Farther up, escape creates a deficit of these atoms relative to diffusive equilibrium, and this in turn leads to upward fluxes of both species to balance escape. A Monte Carlo exosphere simulator program, which has evolved through numerous applications to the moon and terrestrial planets, has been adapted to a coordinated study of the dynamics of D and H in the terrestrial exosphere, plasmasphere, and polar wind. Results show that while the escape of hydrogen is compatible with Hunten's limiting flux at the homopause (about 2.5 × 10 8 cm −2 s −1 ), the upward flow of deuterium is suppressed by slow escape, which in turn causes an exospheric buildup. The global average escape flux of deuterium is 55% (±10%) of its limiting flux, or 1.5 × 10 4 cm −2 s −1 . From an isotopic perspective, the escape rate of D relative to H corresponds to about 39% of the D/H ratio in SMOW.