Physics Department Seminar University of Alaska Fairbanks

J O U R N A L    C L U B

Statistical modeling of geomagnetic storm occurrences
Karen Remick
HIPAS Observatory

Using the accumulated 73 years worth of Kp data, we create a statistical model of geomagnetic storm occurrence. We define a geomagnetic storm as the occurrence of a Kp value above a given threshold, which is preceded by at least 2 days (16 readings) below the threshold. This eliminates the temporal clumping of Kp, which distorts the distributions. We find the wait times between storm occurrences can be described by an exponential distribution. This implies the arrival of geomagnetic storms is a Poisson process. We then determine the solar cycle variation of the occurrence rate through maximum likelihood fitting. The range of variation in occurrence rate is found to depend on the threshold chosen, with Kp ≥ 5 storms varying only a few percent, while Kp > 8 storms vary by more than a factor of 4. Comparing the occurrence rate of sunspots to that of storms of various thresholds shows a dependence on threshold level. Large storms are seen to occur earlier on the solar cycle than small storms.

Friday, 17 November 2006
Globe Room, Elvey Building
3:45 PM