SEP Event Science at Mars

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SEP Event Science at Mars
D. Brain, J. Luhmann, G. Delory (SSL UCB)
R.A. Mewaldt, C.M.S. Cohen (Caltech)

• Physics of SEP events
• Propagation through heliosphere
• Structure/morphology at 1.5 AU
• Consequences for Mars
• Effects at surface
• Effects on atmosphere

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Solar Protons at Mars
http//physics.nist.gov/PhysRefData/Star/Text/cont
ents.html
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Solar Protons at Mars
g 3.71 m/s2 P(0) 6.36 mbar H 11.1
km
http//physics.nist.gov/PhysRefData/Star/Text/cont
ents.html
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Solar Protons at Mars
g 3.71 m/s2 P(0) 6.36 mbar H 11.1
km
these primaries reach surface
http//physics.nist.gov/PhysRefData/Star/Text/cont
ents.html
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October Eventat Surface
The time integrated GOES event spectrum resembles
the SIREST SEP/SPE input spectrum
?
Integrated Event Spectrum
SIREST Input SPE Spectrum
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October Eventat Surface-Results fromSIREST site
Surface radiation flux from SEP event comparable
to or exceeds that from GCRs
GCR
SEP
Input (Space) Spectra
neutrons (up and down)
protons
Output Surface Fluxes
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Do Crustal Fields Matter?
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Effects of Crustal Fields
exobase
Magnetic fields deflect low energy (few MeV)
particles
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Deflection of Primary Protons
small deflection at surface for high energy
protons
large deflection for lower energy protons (at
higher altitudes)
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Effects of Crustal Fields
For low energy particles Less energy is
deposited above crustal sources than in
surrounding areas
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Summary

• The surface radiation from a large SPE can be
  important compared to the surface radiation from
  GCRs.
• Crustal fields do not strongly effect SEPs
  reaching the Martian surface.
• Crustal fields can have a significant effect on
  atmospheric energy deposition during a SPE,
  driving chemistry and dynamics
• ( Proposal to continue this work submitted to
  Planetary Atmospheres )
• Also
• Relationship discovered between the presence
  of intense auroral-like electron distributions
  and SEP events at Mars