On the lognormality of historical magnetic storm intensity statistics: Implications for extreme‐event probabilities

Geophysical Research Letters
By: , and 

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Abstract

An examination is made of the hypothesis that the statistics of magnetic storm maximum intensities are the realization of a lognormal stochastic process. Weighted least squares and maximum likelihood methods are used to fit lognormal functions to −Dst 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, −Dst ≥ 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 year magnetic storm is identified as having a −Dst ≥ 880 nT (greater than Carrington) but a wide 95% confidence interval of [490, 1187] nT.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title On the lognormality of historical magnetic storm intensity statistics: Implications for extreme‐event probabilities
Series title Geophysical Research Letters
DOI 10.1002/2015GL064842
Volume 42
Issue 16
Year Published 2015
Language English
Publisher AGU
Contributing office(s) Geologic Hazards Science Center
Description 10 p.
First page 6544
Last page 6553