Seasonal variations in the SAMPEX/PET proton flux data
It has been firmly established that the low-altitude trapped proton population exhibits strong time variations related to neutral atmosphere conditions. The flux measurements of the Proton Electron Telescope (PET) onboard the polar satellite SAMPEX constitute an adequate data set to characterize the different variations and to distinguish respective time scales. The four years (1992-1996) of PET data at our disposal allow us to analyze in more detail the relation between the proton flux variation and solar activity during the most recent descending solar cycle phase. After accounting for this effects, the PET data still exhibit a clear systematic variation on a shorter time scale. The residual flux variation, which can be as high as a factor 2, is strongly correlated with the seasonal variation of the MSISE-90 total mass density in the SAA at the altitude of mirroring protons.