1 / 25

Dave Brain UC Berkeley Space Sciences Lab (Hi folks! Sorry I couldn’t make it!)

Space Weather Events at Mars: Spacecraft Observations and Consequences for the Atmosphere and Surface. Dave Brain UC Berkeley Space Sciences Lab (Hi folks! Sorry I couldn’t make it!). 10’s MeV ions. 10-20 keV electrons. . Count Rate. Count Rate. . ER. Energy. Energy.

tea
Download Presentation

Dave Brain UC Berkeley Space Sciences Lab (Hi folks! Sorry I couldn’t make it!)

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Space Weather Events at Mars:Spacecraft Observations and Consequences for the Atmosphere and Surface Dave Brain UC Berkeley Space Sciences Lab (Hi folks! Sorry I couldn’t make it!)

  2. 10’s MeV ions 10-20 keV electrons  Count Rate Count Rate  ER Energy Energy MGS ER “Background” ‘High’ energy channels of electron instrument record 10-20 keV electrons and energetic ions Comparing count rates in these 3 channels allows determination of which particle populations contribute to observations

  3. A Space Weather Event at Mars shock arrival ‘real’ electrons present ‘real’ electrons present quiet time data dropouts MGS observations best for obtaining timing information at 1.5 AU, and qualitative info about fluxes of 10’s MeV ions and 10-20 keV electrons

  4. SEP Events at 1.5 AU1999-2005 More than 50 events (over 5 years) of enhanced background Count rate exceeds 50 counts/second ~4% of the time

  5. March 2003 SEP Event The radiation detector on Mars Odyssey saw modulations in the count rate at the S/C orbital period during a SEP event The MGS electron instrument also saw modulations at the S/C orbital period. But the event started much later at MGS! ER background count rate MARIE and ER likely sensitive to different particle energy ranges

  6. March 2003 SEP Event ‘real’ electrons last page • The event(s) observed by MARIE lasted beyond March 19 • Largest increase in solar wind pressure occurred late on March 21, • after decline in particles and during subsequent event • IMF changes direction on the 19th from dawnward to duskward • 10-20 keV electrons observed through the 25th

  7. Dropouts Dropouts in ‘background’ count rate observed during SEP events 10-20 keV electrons removed Are 10’s MeV ions removed? Why do the dropouts occur?

  8. Dropouts Some dropouts associated with shadow entry/exit S/C shielding effect? Electric fields? Ionospheric clouds?

  9. Dropouts ? Some dropouts associated with Martian crustal sources Crustal fields exclude 10-20 keV electrons?

  10. More Dropouts Dropouts during more intense July 2002 event are associated primarily with leaving shadow in southern hemisphere, and crustal magnetic fields

  11. And Still More Dropouts No dropouts before shock arrival  dropouts in 10-20 keV electrons only

  12. Solving the Mystery • Observed by MGS Electron instrument: • Oscillation in quiet time background • Many SEP events • Elevated ‘background’ count rates during SEP events (10’s MeV ions) • 10-20 keV electrons after shock arrival • Dropouts in background count rate during SEP events • correspond to shadow entry/exit • correspond to crustal magnetic fields • Plenty more to do… • What is going on? • Detailed physical interpretation tantalyzingly difficult (argh!) • Dedicated instruments likely required • SEP detector (10’s MeV to 1 GeV) • Clean electron measurements • Solar wind monitor (IMF, dynamic pressure)

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

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

  15. 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/contents.html

  16. 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/contents.html

  17. Shielding by Martian Atmosphere protons alphas electrons

  18. Martian Atmosphere

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

  20. Surface radiation flux from SEP event comparable to or exceeds that from GCRs October Eventat Surface SEP GCR Input Spectra neutrons (up and down) protons Output Surface Flux

  21. Do Crustal Fields Matter?

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

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

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

  25. 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

More Related