Studying geoeffective interplanetary coronal mass ejections between the Sun and Earth: Space weather implications of Solar Mass Ejection Imager observations

Space Weather 7, S05002, 2009

Studying geoeffective interplanetary coronal mass ejections between the Sun and Earth: Space weather implications of Solar Mass Ejection Imager observations

D.F. Webb
Inst. for Scientific Research, Boston College, MA, USA
Space Vehicles Directorate, Air Force Research Laboratory, Hanscom Air Force Base, MA, USA

T.A. Howard
Air Force Research Laboratory, NSO, Sunspot, NM, USA

C.D. Fry
Exploration Physics International, Inc., Huntsville, AL, USA

T.A. Kuchar and D.R. Mizuno
Inst. for Scientific Research, Boston College, MA, USA
Space Vehicles Directorate, Air Force Research Laboratory, Hanscom Air Force Base, MA, USA

J.C. Johnston
Space Vehicles Directorate, Air Force Research Laboratory, Hanscom Air Force Base, MA, USA

B.V. Jackson
Center for Astrophysics and Space Science, Univ. of California, La Jolla, CA, USA

Abstract

Interplanetary coronal mass ejections (ICMEs) are the primary cause of severe space weather at Earth because they drive shocks and trigger geomagnetic storms that can damage spacecraft and ground-based systems. The Solar Mass Ejection Imager (SMEI) is a U. S. Air Force experiment with the ability to track ICMEs in white light from near the Sun to Earth and beyond, thus providing an extended observational range for forecasting storms. We summarize several studies of SMEI's detection and tracking capability, especially of the ICMEs associated with the intense (peak Dst ≤ −100 nT) geomagnetic storms that were the focus of the NASA Living With a Star Geostorm Coordinated Data Analysis Workshop. We describe the SMEI observations and analyses for the 18 intense storms observed from May 2003–2007 with adequate SMEI coverage and identified solar and interplanetary source regions. SMEI observed the associated ICMEs for 89% of these intense storms. For each event we extracted the time differences between these sets of times at 1 AU for shock arrival time, predicted ICME arrival time, onset of high-altitude aurora observed by SMEI, and storm onset. The mean intervals between successive pairs of these data were found to each be ∼4 hours. On average, SMEI first detected the geoeffective ICME about 1 day in advance, yielding a prediction lead time of ∼18 hours. Finally, the RMS values for the ICME-shock and storm-ICME time differences were determined, and provide at least a 1-hour improvement compared to similar observational and model-dependent studies.