Ionospheric Response to the Sustained High Geomagnetic Activity During the March '89 Great Storm

Authors

Jan Josef Sojka, Utah State UniversityFollow
Robert W. Schunk, Utah State UniversityFollow
W. F. Denig

Document Type

Article

Journal/Book Title/Conference

Journal of Geophysical Research: Space Physics

Volume

99

Issue

A11

Publisher

American Geophysical Union

Publication Date

1994

First Page

21,341

Last Page

21,352

Abstract

A simulation was conducted to model the high-latitude ionospheric response to the sustained level of high geomagnetic activity for the great magnetic storm period of March 13-14, 1989. The geomagnetic and solar activity indices and the DMSP F8 and F9 satellite data for particle precipitation and high-latitude convection were used as inputs to a time-dependent ionospheric model (TDIM). The results of the TDIM were compared to both DMSP plasma density data and ground-based total electron content (TEC) measurements for the great storm period as well as with earlier storm observations. The comparisons showed that the overall structure of the high-latitude ionosphere was dominated by an increased convection speed within the polar cap that led to increased ion temperatures. In turn, this enhanced the NO⁺ density, raised the atomic-to-molecular ion transition height to over 300 km, decreased N_mF₂ , increased h_mF₂ , and in places either increased n_e at 800 km or slightly decreased it. The morphology of the ionosphere under these extreme conditions was considerably different than that modeled for less disturbed intervals. These differences included the character of the dayside tongue of ionization that no longer extended deep into the polar cap. Instead, as a result of the ion heating and consequent reduction in N_mF₂ , a large polar hole occupied much of the polar region. This polar hole extended beyond the auroral oval and merged with the night sector midlatitude trough. The limitations associated with the applicability of the TDIM to the geomagnetic conditions present on March 13 and 14 are discussed. The primary limitations of the TDIM derive from the limited temporal resolution of the model input parameters and the lack of a suitably dynamic thermospheric specification for the great storm conditions. These limitations lead to midlatitude ionospheric storm phases that do not follow those observed.

Comments

Originally published by the American Geophysical Union. Abstract available online through the Journal of Geophysical Research: Space Physics.