Analysis of Dose Rate Variations Observed By MSL/RAD

Monday, 15 December 2014
Jingnan Guo1, Cary J Zeitlin2, R F Wimmer-Schweingruber1, Scot CR Rafkin3, Bent Ehresmann3, Jan Kohler1, Jan Kristoffer Appel1, Don Hassler4, Eckhard Boehm1, Stephan I Böttcher1, Cesar Martin-Garcia1, David E Brinza5, Henning Lohf1, Soenke Burmeister1, Bernd Heber1, Arik Posner6, Guenther Reitz7, Javier Martín-Torres8, Maria-Paz Zorzano9 and Henrik Kahanpää10, (1)University of Kiel, Kiel, Germany, (2)Southwest Research Institute, Oakland, CA, United States, (3)Southwest Research Institute Boulder, Boulder, CO, United States, (4)Southwest Research Inst, Boulder, CO, United States, (5)Jet Propulsion Laboratory, Pasadena, CA, United States, (6)NASA Headquarters, Washington, DC, United States, (7)German Aerospace Center DLR Cologne, Cologne, Germany, (8)Instituto Andaluz de Ciencias de la Tierra, Granada, Spain, (9)INTA-CSIC, Madrid, Spain, (10)Finnish Meteorological Inst, Helsinki, Finland
The Radiation Assessment Detector (RAD), on board Mars Science Laboratory's (MSL) rover Curiosity, measures the spectra of both energetic charged and neutral particles along with the radiation dose rate at the surface of Mars. With these first-ever measurements on the Martian surface, RAD observed several effects influencing the galactic cosmic ray (GCR)-induced surface radiation dose concurrently: [a] short-term diurnal variations of the Martian atmospheric pressure caused by daily thermal tides; [b] long-term seasonal pressure changes in the Martian atmosphere; and [c] the modulation of the primary GCR flux by the solar magnetic field, which correlates with long-term solar activities and heliospheric rotation. RAD also recorded the dose rate during the 253-day cruise phase of MSL from Earth to Mars. There, the variations of the GCR-induced dose rates during quiet time period without the influences of Solar Energetic Particles (SEPs) were theoretically solely driven by the changes of heliospheric conditions (i.e., [c]). The RAD cruise and surface dose measurements, along with the surface pressure data and the solar modulation factor, are analyzed in order to understand how the long-term influences ([b] and [c]) individually correlate with the measured dose rates.