1. Effects of Solar Energetic Particle Events on the Martian Surface and Atmosphere F Leblanc, DA Brain, JG Luhmann, GT Delory, RA Mewaldt, CM Cohen 2004 Fall AGU Meeting - Friday 17 December

2. Motivation Record-setting Halloween 2003 Solar Energetic Particle event occurred when Earth and Mars “on same field line” Protons 1 MeV to 1 GeV

3. Mars Global Surveyor - Electron Reflectometer Data Electron instrument at Mars “contaminated” by energetic particles Motivation What effect do SEP events have on the Martian surface and atmosphere?

4. Solar Protons at Mars http://physics.nist.gov/PhysRefData/Star/Text/contents.html

5. Solar Protons at Mars http://physics.nist.gov/PhysRefData/Star/Text/contents.html g = 3.71 m/s 2 P(0) = 6.36 mbar H = 11.1 km

6. Solar Protons at Mars http://physics.nist.gov/PhysRefData/Star/Text/contents.html these primaries reach surface g = 3.71 m/s 2 P(0) = 6.36 mbar H = 11.1 km

7. Shielding by Martian Atmosphere protons alphas electrons

8. Martian Atmosphere

9. October Event at Surface  The time integrated GOES event spectrum resembles the SIREST SEP/SPE input spectrum http://sirest.larc.nasa.gov/ Integrated Event SpectrumSIREST Input SPE Spectrum

10. GCRSEP Input Spectra Output Surface Flux Surface radiation flux from SEP event exceeds that from GCRs October Event at Surface neutrons (up and down) protons

11. Do Crustal Fields Matter?

12. Effects of Crustal Fields exobase Magnetic fields deflect low energy (few MeV) particles

13. Deflection of Primary Protons small deflection at surface for high energy protons large deflection for lower energy protons (at higher altitudes)

14. Effects of Crustal Fields For low energy particles: Less energy is deposited above crustal sources than in surrounding areas

15. Summary The surface radiation from a large SPE can be important compared to the surface radiation from GCRs. Crustal fields can have a significant effect on atmospheric energy deposition during a SPE. They do not have a strong effect on SEPs reaching the Martian surface.