Proceeding toward the maximum of solar cycle 25 with a radiation environment similar to the previous cycle

Abstract

The Sun exhibited lower-than-average activity levels, including a weak maximum and a prolonged minimum in the solar cycle (SC) 24. Thiswas following a 60-year trend of weakening solar activity, leading to speculations that we could be moving into another secular minimum scenario like the Dalton or the Gleissberg periods. During such periods, the fluxes of galactic cosmic rays (GCRs) increase significantly, introducing radiation hazards for long-term crewed space explorations. In our previous work, we predicted the level of solar activity, and thus, the radiation environment for SC25 will be similar to SC24. In this paper, we show that, to date, the radiation environment observed by CRaTER has been similar to SC24, as we predicted. Furthermore, we predict that if the radiation environment remains similar to SC24, the maximum value for permissible mission duration (PMD) for SC25 will be 917-230+234 days based on NASA’s latest permissible exposure limit (PEL).