Observations of solar cyclical variations in geocoronal Hα column emission intensities
Article first published online: 20 MAR 2004
Copyright 2004 by the American Geophysical Union.
Geophysical Research Letters
Volume 31, Issue 6, March 2004
How to Cite
2004), Observations of solar cyclical variations in geocoronal Hα column emission intensities, Geophys. Res. Lett., 31, L06110, doi:10.1029/2003GL018729., , , and (
- Issue published online: 20 MAR 2004
- Article first published online: 20 MAR 2004
- Manuscript Accepted: 9 FEB 2004
- Manuscript Revised: 30 JAN 2004
- Manuscript Received: 26 SEP 2003
 Observations of thermospheric + exospheric Hα column emissions by the Wisconsin Hα Mapper (WHAM) Fabry-Perot (Kitt Peak, Arizona) over the 1997–2001 rise in solar cycle 23 show a statistically significant solar cyclical variation. The higher signal-to-noise WHAM observations corroborate suggestions of a solar cycle trend in the Hα emissions seen in Wisconsin observations over solar cycle 22. Here we compare WHAM 1997 and 2000–2001 winter solstice geocoronal Hα observations toward regions of the sky with low galactic emission. The observed variation in geocoronal hydrogen column emission intensities over the solar cycle is small compared with variations in hydrogen exobase densities. Higher Hα emissions are seen during solar maximum periods of the solar cycle. At a mid range shadow altitude (3000 km), WHAM geocoronal Hα intensities are about 45% higher during solar maximum than during solar minimum.