APPLICATION OF 3D HYDROGEN CORONA DISTRIBUTION MODEL TO
RETRIVE ATOMIC HYDROGEN FROM EMUS/EMM OBSERVATIONS.
Susarla Raghuram, Laboratory for Atmospheric and Space Physics, University of Colorado Boulder, Boulder, CO,
USA, Space and Planetary Science Center, Khalifa University, Abu Dhabi, UAE (susarla.raghuram@lasp.colorado.eduk),
Mike Chaffin, Laboratory for Atmospheric and Space Physics, University of Colorado Boulder, Boulder, CO, USA,
Justin Deighan, Laboratory for Atmospheric and Space Physics, University of Colorado Boulder, Boulder, CO, USA,
Sonal Jain, Laboratory for Atmospheric and Space Physics, University of Colorado Boulder, Boulder, CO, USA,
Robert Lillis, Space Sciences Laboratory, University of California, Berkeley, CA, USA, Rodney Elliott, Laboratory
for Atmospheric and Space Physics, University of Colorado Boulder, Boulder, CO, USA, Matt Fillingim, Space
Sciences Laboratory, University of California, Berkeley, CA, USA, Greg Holsclaw, Laboratory for Atmospheric and
Space Physics, University of Colorado Boulder, Boulder, CO, USA, Hessa AlMatroushi, Mohammed Bin Rashid
Space Center, Dubai, UAE, David Brain, Laboratory for Atmospheric and Space Physics, University of Colorado
Boulder, Boulder, CO, USA, Scott England, Virginia Polytechnic Institute and State University, Aerospace and Ocean
Engineering, Blacksburg, VA, USA, Krishnaprasad Chirakkil, Laboratory for Atmospheric and Space Physics, University of Colorado Boulder, Boulder, CO, USA, Space and Planetary Science Center, Khalifa University, Abu Dhabi,
UAE, Fatma Lootah, Mohammed Bin Rashid Space Center, Dubai, UAE, Hoor AlMazmi, UAE Space Agency, Abu
Dhabi, UAE.

Introduction
Hydrogen is essentially produced from the dissociation
of H2 O and via odd-hydrogen reactions in the Martian
atmosphere. A fraction of H2 transported to the upper atmosphere is dissociated by solar ultraviolet photons that
leads to fast moving hydrogen atoms. The scale height
of atomic hydrogen is larger than any other species due
to its smaller mass, which makes hydrogen a dominant
species in the Martian exosphere. The study of atomic
hydrogen distribution and its loss rate from the Martian
atmosphere can help us to understand the history of water presence on Mars. Previous observations have shown
that atomic hydrogen density is highly variable in the
Martian exosphere but its spatial and temporal variability over a large period is not yet well-understood [Chaffin
et al., 2014; Clarke et al., 2014; Halekas, 2017; Stone et al.,
2020, and several other works]. Characterizing the hydrogen variability in the Martian exosphere is one of the
primary goals of the Emirates Ultraviolet Spectrometer (EMUS) onboard Emirates Mars Mission (EMM). A
global hydrogen distribution model for atomic hydrogen
is essential while retrieving the density and temperature
of hydrogen from the EMUS/EMM observations.

at the critical level.

Application of the model for MCD exobase condition
The developed model has been applied under different
exobase conditions of Mars obtained from Mars Climate
Data (MCD) base model [Forget et al., 1999] and the calculated hydrogen distribution profiles are compared with
Chamberlain [1963] model (See Figure 1). A significant
difference between the modelled hydrogen distribution
profiles has been noticed. Along with the EMUS/EMM
observations, this model will be used to constrain the
density and temperature of hydrogen in the Martian exosphere. This approach allows us to study the global
distribution of atomic hydrogen and its variability at different Martian seasons and also under different space
weather conditions.

Model
Following the theoretical approach of Vidal-Madjar and
Bertaux [1972], we developed a 3-D hydrogen corona
distribution model which is characterized by the conditions of exobase such as number density and temperature. Unlike the classical Chamberlain [1963] model,
which assumes a uniform temperature and number density at the exobase, this model can account for inhomogeneous distribution of temperature and number density

Figure 1: A comparison of modelled atomic hydrogen density
profile calculated using MCD exobase condition with Chamberlin (1963) calculation.

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