Abstract <p>The radiation from galactic and solar cosmic rays as they pass through the modern and rarefied (as a result of multiple reversals) atmosphere during solar proton events and at the time of geomagnetic reversal is studied. We suppose that, during the reversal process, the geomagnetic field weakens and takes on an axisymmetric quadrupole configuration. It is shown that, in the case of a single reversal, when the atmosphere does not have time to change, radiation dose powers increase only at low latitudes and are identical to the modern radiation at the poles. However, during the period of multiple inversions, when the atmosphere is rarefied, the level of radiation at the moment of reversal on the Earth’s surface increases, on average, twice as much as today’s radiation at all latitudes, which can affect the biosphere.</p>