Long‐term variations of the electron slot region and global radiation belt structure

We report the observations of changes of the nominal position of the quiet‐time radiation belt slot over the solar cycles. It has been found that the slot region, believed to be a result of enhanced precipitation losses of energetic electrons due to their interactions with VLF waves in the magnetosphere, tends to shift to higher L (∼3) during a solar maximum compared to its canonical L value of ∼2.5, which is more typical of a solar minimum. The solar‐cycle migration of the slot can be understood in terms of the solar‐cycle changes in ionospheric densities, which may cause the optimal wave‐particle interaction region during higher solar activity periods to move to higher altitudes and higher latitudes, thus higher L . Our analysis also suggests that the primary regions of wave‐particle interaction processes that result in the slot formation are located off of the magnetic equator.