Predictable aspects of the variable likelihood of extreme space weather events
Space weather, the manifestation on Earth of energetic solar events, has a broad range of impacts, from the appearance of the northern and southern lights, to the disruption of GPS navigation, communication networks and, in extreme cases, power grids. The likelihood of an extreme, damaging space weather event occurring changes as solar activity varies, over a roughly 11-year cycle. However, each of these solar cycles is unique in its peak activity and exact duration, leading to long-term trends in the occurrence of space weather events, known as space climate.
In this work we have studied the interval around the maxima of each of the last 5 solar cycles, looking at the statistics of the largest measurements of four space weather-relevant quantities: the F10.7 index, the solar wind dynamic pressure, and the AE and Dst geomagnetic indices. We find that for each parameter, the functional form of the statistical distribution of its extreme values was the same for all five solar cycles - that is, the equation that describes the likelihood of measuring a certain extreme value was the same for all solar maxima. The unique peak activity level of each cycle was reflected in the mean and variance of the extreme values during that cycle. This will help tailor the prediction of the likelihood of the largest, potentially most damaging, space weather events to the unique activity of each solar cycle.
Caption to figure: The aurora, or northern and southern lights, are the most beautiful manifestation of space weather on Earth.
- Publication: Chapman, S.C., N.W. Watkins, and E. Tindale (2018), Space Weather, in press.