Studying the South Atlantic Anomaly temporal evolutionfrom 1998 to 2022 using the SEM-2 proton flux

The SEM-2 (Space Environment Monitor-2) instrument embedded on the NOAA-15 Low Earth Orbit satellite provides measurements of trapped protons in the Van Allen inner belt from 1998 to nowadays. This continuous amount of measurements enables us to study the temporal evolution of the dynamics of the South Atlantic Anomaly (SAA) over more than two solar cycles.
In particular, we study the temporal evolution of the area of the SAA. We observe that the area of the SAA is anti-correlated with the solar activity. Two physical process explain this anticorrelation.
First, the more the Sun is active the more it disables the cosmic rays to reach the Earth Magnetosphere and to fill the inner radiation belt with protons. Then, when the Sun in more active, the upper atmosphere is warmer and therefore absorbs more protons from the radiation belt.
Then, we investigate the protons flux centroid of the SAA. The temporal evolution of its position, latitude and, longitude is studied over the same time interval (1998-2022). We notice the latitude of the centroid is also anti-correlated with the solar activity whereas the longitude seems absolutely
independent. Some explanations are given for these observations.
The temporal evolution of the position of the centroid shows a drift of the SAA. Indeed from 1998 to 2022 the SAA drifted of about 7 degrees West.
The SEM-2 instrument measures flux for protons of different energies (16, 36, 70 and, 140 MeV). For each energy, the SAA dynamic has a similar trend but with different values. These differences are investigated and the results discussed.