1. The Thermosphere/Ionosphere Response to Solar Activity During the October/November 2003 Storms P. R. Straus 1, G. Crowley 2, R. R. Meier 3, L. J. Paxton 4, D. Morrison 4, P. C. Anderson 1, R. DeMajistre 4, H. Kil 4, Y. Zhang 4, A. B. Christensen 1 1 The Aerospace Corporation, Los Angeles, CA; 2 Southwest Research Institute, San Antonio, TX; 3 The Naval Research Laboratory, Washington DC; 4 Johns-Hopkins University Applied Physics Laboratory, Laurel, MD ©2004 The Aerospace Corporation ABSTRACT October/November of 2003 was a period of unusually high geomagnetic activity driven by various types of solar forcing (flares, proton events, and CME’s). Changes in the state of the thermosphere and ionosphere during this time period were observed by the GUVI instrument on TIMED and GPS occultation sensors on the PICOSat and CHAMP satellites. We present these observations, together with TIMEGCM model simulations for this period to evaluate our understanding of the terrestrial impacts of solar forcing. TIMED PICOSat CHAMP October 31 October 29 October 30 October 31 00/12 UT02/14 UT04/16 UT06/18 UT08/20 UT10/22 UT00/12 UT02/14 UT04/16 UT06/18 UT08/20 UT10/22 UT00/12 UT02/14 UT04/16 UT06/18 UT08/20 UT10/22 UT O/N2 Ratio foF2 November 19 00/12 UT02/14 UT04/16 UT06/18 UT08/20 UT10/22 UT00/12 UT02/14 UT04/16 UT06/18 UT08/20 UT10/22 UT00/12 UT02/14 UT04/16 UT06/18 UT08/20 UT10/22 UT O/N2 Ratio foF2 November 20November 21 October Storm November Storm November 4 X-Ray Flare October 29October 30 For the October storm, the TIMED, PICOSat, and CHAMP ascending nodes were at 04:00, 18:50, & 01:00 LT, respectively. For the November storm, they were 23:40, 13:30, & 23:00 LT Geophysical Indices Conclusions GPS occultation observations from the Ionospheric Occultation Experiment (IOX) on PICOSat and the CHAMP satellite are able to qualitatively validate some aspects of the TIMEGCM simulation of the October/November storms. In particular, the depletions in electron density predicted by the model are observed. However, the magnitudes of these depletions seems quite variable relative to the model, and in some cases the depleted regions do not seem to extend as far as predicted by the model. A significant enhancement of E- region was observed by IOX during the record solar flare of November 4. Oct 31 15:47 Oct 28 15:37 PRN03/31 Oct 31 16:14 Oct 28 16:00 PRN21/09 Oct 31 09:29 Oct 28 10:40 PRN06/30 Oct 31 15:37 Oct 28 15:25 PRN16/02 Oct 31 01:42 Oct 28 01:27 PRN20/20 Oct 31 01:51 Oct 28 01:40 PRN14/14 IOX Data CHAMP Data Terminator Orbit Track GUVI observations of the column integrated O/N 2 ratio provide an indication of thermospheric dynamics during the October and November storms. Neutral composition affects the ionosphere through ion loss, with increases in molecular nitrogen accelerating the loss process. Comparisons between model results sampled at the TIMED local time and the GUVI observations shows a match between some, but not all, features observed by GUVI. Samples of IOX & CHAMP GPS occultation electron density profiles during quiet (upper foF2 plots) and disturbed (lower foF2 plots) periods are used here to validate model understanding. Occultation Locations Nov 20 16:03 Nov 19 14:52 PRN31/11 Nov 20 15:24 Nov 19 14:10 PRN04/13 Nov 20 20:42 Nov 19 20:00 PRN30/06 Nov 21 05:09 Nov 20 04:35 PRN01/02 Nov 21 06:26 Nov 20 05:51 PRN10/29 Nov 20 20:25 Nov 19 14:39 PRN18/18 IOX Data CHAMP Data A factor of three enhancement in the southern hemisphere E-region was observed by IOX during the record solar flare that occurred on November 4 th. November 3 November 4 November 20November 21 5 15 10 20 foF2 (MHz) Storm Times