Cool Stars 14 - Submitted Abstract # 307
This version created on 05 October 2006

Energy Deposition by Solar Energetic Particles in the Upper
Atmospheres of


David Brain, UC Berkeley Space Sciences Lab  
R. Mewaldt, California Institute of Technology  
C. Cohen, California Institute of Technology  
H. Lammer, Space Research Institute  
S. Bougher, University of Michigan  
J. Luhmann, UC Berkeley Space Sciences Lab  
G. Delory, UC Berkeley Space Sciences Lab  
F. Leblanc, Service d'Aéronomie du CNRS

The structure, dynamics, chemistry, and evolution of planetary
atmospheres are in large part determined by the available sources of
energy.  One potentially important energy source is solar energetic
particle (SEP) events consisting of large fluxes of charged particles
accelerated near the Sun during and following fast coronal mass
ejections.  While other mechanisms provide more constant sources of
energy, SEP events can significantly affect an atmosphere for short
periods, possibly enhancing atmospheric loss and driving chemical
reactions.  At unmagnetized planets, in particular, SEPs of all
energies have direct access to the atmosphere and so provide a more
substantial energy source than at planets having protective global
magnetic fields.  SEP-related atmospheric energy input should be more
significant for planets orbiting more active stars.  Therefore
quantification of the atmospheric energy input from SEP events is an
important component of our understanding of the processes that control
their state and evolution.  Here we present the results of an initial
calculation of the energy input by a single large SEP event in a
Venus-like CO2 atmosphere.  We calculate the penetration depth and
energy deposition profile of energetic protons having different
incident energies, and weight the profiles by the event-integrated
energy spectrum of a SEP event to calculate the total energy
deposition.  We compare to the energy deposited by photons and discuss
the potential role of SEP events on extrasolar planetary atmospheres.


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