Charged Particle Measurements with the Mars Science Laboratory's Radiation Assessment Detector (MSL/RAD)

Monday, 15 December 2014
Bent Ehresmann1, Don Hassler1, Cary J Zeitlin2, Jan Kohler3, R F Wimmer-Schweingruber3, Jan Kristoffer Appel3, Eckhard Boehm3, Stephan I Böttcher3, David E Brinza4, Soenke Burmeister3, Jingnan Guo3, Henning Lohf3, Cesar Martin-Garcia3, Daniel Matthiae5, Arik Posner6, Scot CR Rafkin1 and Guenther Reitz5, (1)Southwest Research Institute Boulder, Boulder, CO, United States, (2)Southwest Research Institute, Durham, NH, United States, (3)University of Kiel, Kiel, Germany, (4)Jet Propulsion Laboratory, Pasadena, CA, United States, (5)German Aerospace Center DLR Cologne, Cologne, Germany, (6)NASA Headquarters, Washington, DC, United States
Since the Curiosity rover's landing in Gale crater on the surface of Mars, the Radiation Assessment Detector (RAD) on board the rover has been conducting the first-ever measurements of the Martian surface radiation field. This field is induced by Galactic Cosmic Rays (GCRs) and their interactions with the atoms of the Martian atmosphere and soil. Furthermore, sporadic Solar Energetic Particle (SEP) events can lead to large, but short-term enhancements in the intensity of the radiation field. A large part of the radiation environment is made up of charged particles, e.g., ions and their isotopes, electrons, and positrons amongst others. There are mainly two factors influencing the surface radiation field: the modulation of the incoming GCR flux due to the solar magnetic field correlating with the solar cycle; the amount of atmospheric column mass above Gale crater resulting in changes of GCR penetration depth into the atmosphere, as well as influencing the secondary particle production rate. Here, we focus on the temporal evolution of the radiation environment since the landing, analyzing changes in the measured particle spectra for different phases in the Martian seasonal cycle and solar activity. Furthermore, we present enhancements in the proton flux during directly observed SEP events.