All Physics Faculty Publications

Document Type

Article

Journal/Book Title/Conference

Journal of Geophysical Research: Space Physics

Volume

110

Issue

A08306

Publisher

American Geophysical Union

Publication Date

2005

First Page

1

Last Page

17

DOI

10.1029/2004JA010782

Abstract

A 1-D global average ionosphere and thermosphere (GAIT) model is used to examine the climatological behavior of the upper atmosphere, subject to both extremely low and high solar flux. These extremes are justified, in part, by the Maunder Minimum and Grand Maximum epochs described by J. A. Eddy, as well as other studies involving cosmogenic isotopes and Sun-like stars. As the irradiance falls below normal solar minimum levels, the concentration of O+ decreases rapidly relative to the molecular ions, such that the ratio ƒoF2oF1 approaches unity. When subject to exceptionally high solar fluxes, the ionospheric peak electron density (NmF2) unexpectedly plateaus, remaining relatively constant even as the photon flux continues to increase. In both cases, the state of the underlying thermosphere, particularly the neutral gas temperature, is found to be largely responsible. Model trends are discussed in relation to ionospheric observations, specifically the preponderance of so-called ionospheric G conditions at solar minimum and ƒoF2 saturation at solar maximum, as well as the problem of Earth's global helium budget.

Comments

Originally published by the American Geophysical Union. Publisher's PDF available thorough the Journal of Geophysical Research: Space Physics.

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