Solar radiation-induced changes in ionospheric height and the Schumann resonance waveguide on different timescales
Article first published online: 22 MAR 2007
Copyright 2007 by the American Geophysical Union.
Volume 42, Issue 2, April 2007
How to Cite
2007), Solar radiation-induced changes in ionospheric height and the Schumann resonance waveguide on different timescales, Radio Sci., 42, RS2S11, doi:10.1029/2006RS003494., and (
- Issue published online: 22 MAR 2007
- Article first published online: 22 MAR 2007
- Manuscript Accepted: 19 DEC 2006
- Manuscript Revised: 5 DEC 2006
- Manuscript Received: 3 MAR 2006
- Schumann resonances;
- ionospheric height;
- ionizing radiation
 This study draws together the available observations in the Schumann resonance frequency range to examine the general issue of sensitivity of ionospheric height variations to changes in ionizing radiation from the Sun on different timescales. Ionospheric height can be formally defined, and two characteristic heights are recognized in the Schumann resonance frequency range. In general, order of magnitude changes in radiation are needed to cause relative changes in ionospheric height as large as 10%, as is the case on both the diurnal and 11-year timescales. Changes in EUV radiation are probably insufficiently strong to account for either the 27-day or the 11-year variation in ionospheric height. More ionization-effective X radiation is needed, but much smaller height changes are expected on the solar rotation timescale because the variations in X radiation on this timescale are only tens of percent and not orders of magnitude. The annual variation in radiation from the Sun is only 7%, with an expected height variation less than 100 m, and this remains to be verified by observations. The general insensitivity of the Schumann resonance cavity to changes in ionizing radiation lends stability to the medium that is valuable toward quantifying absolute changes in the global lightning activity on various timescales within the cavity.