Observations of solar cyclical variations in geocoronal HA column emission intensities - art. no. L06110

摘要

1] Observations of thermospheric + exospheric Halpha column emissions by the Wisconsin Halpha 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 Halpha emissions seen in Wisconsin observations over solar cycle 22. Here we compare WHAM 1997 and 2000-2001 winter solstice geocoronal Halpha 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 Halpha emissions are seen during solar maximum periods of the solar cycle. At a mid range shadow altitude (3000 km), WHAM geocoronal Halpha intensities are about 45% higher during solar maximum than during solar minimum. [References: 23