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Observations of exosphere variations during geomagnetic storms

2013; American Geophysical Union; Volume: 40; Issue: 10 Linguagem: Inglês

10.1002/grl.50443

1944-8007

Justin J. Bailey, M. Gruntman,

Astro and Planetary Science

Abstract The dominant neutral constituent in Earth's upper exosphere, atomic hydrogen (H), resonantly scatters solar Lyman‐alpha (121.567 nm) radiation, observed as the geocorona. We report here observations of an exospheric response to geomagnetic storms obtained using measurements of the geocorona by Lyman‐alpha detectors on the Two Wide‐angle Imaging Neutral‐atom Spectrometers mission. We introduce a new parameter, N H , the number of H atoms in the spherical shell from a geocentric distance of 3 to 8 Earth radii, to quantitatively characterize in a simplified way global exospheric conditions. Five geomagnetic storms observed during three months in the second half of 2011 are accompanied by abrupt temporary increases, spikes, of N H from 6% to 17%, lasting not longer than a day. These increases seem to show some correlation with the minimum Dst index reached during the peak of each storm.