Gleissberg cycle dependence of inner zone proton flux

Variation of inner belt protons is correlated with decreasing F10.7 maxima over the 40-year period, serving as proxy for solar EUV input to Earth's atmosphere. Extending an earlier study (Qin et al., 2014; ) of >70 MeV protons from 1980 - 2021 using the South Atlantic Anomaly (SAA) peak flux, and at fixed L = 1.3, a comparison is made between the >35, >70 and >140 MeV energy channels on POES.

All three energies show an increase in proton flux over the period 1998 - 2021 using a single spacecraft. The observed flux increase is correlated with decreasing F10.7 over the longer 40-year time interval, as with the similar to 11-year solar cycle. A phase lag during Solar Cycle 24 (January 2010 - June 2021) between the F10.7 minimum and proton flux maximum was determined to be similar to 500 days, the same at all energies studied.