Holistic study of space weather and space climate at Earth orbit
2019 July 22
We present an update of changes in space weather/space climate at Earth orbit using sunspot number (SSN) timeline (1700-2018), geomagnetic indices aa/Ap (1870–2018), solar polar magnetic field (1976-2017), interplanetary magnetic field (IMF) and galactic cosmic ray (GCR) flux (1963-2018) in the stratosphere at high latitudes. The Cycle 24 is close to minimum, expected in 2020. The baseline of aa index increases monotonically from 1900 to 1986 declining steeply afterwards, solar polar magnetic field decreases systematically for last three cycles (22–24) as do SSNs at cycle peaks. Livingston and Penn (2009) note a long term weakening of maximum magnetic field in sunspots since 1992. They expect SSNs for the Cycle 25 to peak at 7 (a steep decline in solar activity) leading to Maunder-like minimum, in contrast to prediction of a Dalton minimum by several colleagues. The North-South asymmetry in the solar polar field is pronounced for the decay phase of cycles 23, 24, it
seems to change sign after the Cycle 21. GCR flux in the stratosphere is higher than in 1965 and increasing, pointing to an enhanced radiation exposure in future for passengers on transpolar flights, the astronauts on the space station as well as those travelling to and staying on the Moon and the Mars on prolonged missions; the assets in space would have to be hardened for safety from enhanced radiation.