What is it about?

Analysis is made of the long-term statistics of three different measures of ground level, storm time geomagnetic activity: instantaneous 1 min first differences in horizontal intensity ΔBh, the root-mean-square of 10 consecutive 1 min differences S, and the ramp change R over 10 min. Geomagnetic latitude maps of the cumulative exceedances of these three quantities are constructed, giving the threshold (nT/min) for which activity within a 24 h period can be expected to occur once per year, decade, and century. Specifically, at geomagnetic 55°, we estimate once-per-century ΔBh, S, and R exceedances and a site-to-site, proportional, 1 standard deviation range [1 σ, lower and upper] to be, respectively, 1000, [690, 1450]; 500, [350, 720]; and 200, [140, 280] nT/min. At 40°, we estimate once-per-century ΔBh, S, and R exceedances and 1 σ values to be 200, [140, 290]; 100, [70, 140]; and 40, [30, 60] nT/min.

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Why is it important?

This work provides a foundation for characterizing geomagnetic activity useful for estimating geoelectric hazards of concern to the electric-power grid industry.

Perspectives

This work is motivated by priorities set by the Space Weather Operations Response and Mitigation (SWORM) Subcommittee of the United States National Science and Technology Council.

Dr Jeffrey Love
Geomagnetism Program, U.S. Geological Survey

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This page is a summary of: Global statistical maps of extreme-event magnetic observatory 1 min first differences in horizontal intensity, Geophysical Research Letters, May 2016, American Geophysical Union (AGU),
DOI: 10.1002/2016gl068664.
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