E. Joshua Rigler
Antti Pulkkinen
Pete Riley
Jeffrey J. Love
2015
<p><span>An examination is made of the hypothesis that the statistics of magnetic-storm-maximum intensities are the realization of a log-normal stochastic process. Weighted least-squares and maximum-likelihood methods are used to fit log-normal functions to −</span><i>D</i><i>s</i><i>t</i><span> storm-time maxima for years 1957-2012; bootstrap analysis is used to established confidence limits on forecasts. Both methods provide fits that are reasonably consistent with the data; both methods also provide fits that are superior to those that can be made with a power-law function. In general, the maximum-likelihood method provides forecasts having tighter confidence intervals than those provided by weighted least-squares. From extrapolation of maximum-likelihood fits: a magnetic storm with intensity exceeding that of the 1859 Carrington event, −</span><i>D</i><i>s</i><i>t</i><span>≥850 nT, occurs about 1.13 times per century and a wide 95% confidence interval of [0.42,2.41] times per century; a 100-yr magnetic storm is identified as having a −</span><i>D</i><i>s</i><i>t</i><span>≥880 nT (greater than Carrington) but a wide 95% confidence interval of [490,1187] nT.</span></p>
application/pdf
10.1002/2015GL064842
en
American Geophysical Union
On the log-normality of historical magnetic-storm intensity statistics: implications for extreme-event probabilities
article