LAUSR

Forbush decreases (FDs) in galactic cosmic rays (GCRs) have been recorded by neutron monitors (NMs) at Earth for more than 60 years. For the past five years, with the establishment of the Radiation Assessment Detector (RAD) onboard the Mars Science Laboratory (MSL) rover Curiosity at Mars, it is possible to continuously detect, for the first time, FDs at another planet: Mars. In this work, we have compiled a catalog of 424 FDs at Mars using RAD dose rate data, from 2012 to 2016. Furthermore, we applied, for the first time, a comparative statistical analysis of the FDs measured at Mars, by RAD, and at Earth, by NMs, for the same time span. A carefully chosen sample of FDs at Earth and at Mars, driven by the same ICME, led to a significant correlation (cc=0.71$cc=0.71$) and a linear regression between the sizes of the FDs at the different observing points at the respective energies at Mars and Earth. We show that the amplitude of the FD at Mars (AM$A_{\mathrm{M}}$), for an energy of E>150MeV$E>150~\mbox{MeV}$, is higher by a factor of 1.5 – 2 compared to the size of the FD at Earth (AE$A_{\mathrm{E}}$), for a definite rigidity of 10 GV. Finally, almost identical regressions were obtained for both Earth and Mars as concerns the dependence of the maximum hourly decrease of the CR density (DMin$\mathit{DM}_{\mathrm{in}}$) to the size of the FD.