On the log-normality 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 log-normal stochastic process. Weighted least-squares and maximum-likelihood methods are used to fit log-normal 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-yr 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 log-normality 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 American Geophysical Union
Publisher location Washington, D.C.
Contributing office(s) Geologic Hazards Science Center
Description 10 p.
First page 6544
Last page 6553
Online Only (Y/N) N
Additional Online Files (Y/N) N