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Ann. Geophys., 20, 937-945, 2002
www.ann-geophys.net/20/937/2002/
© European Geosciences Union 2002
Real-time forecasting of ICME shock arrivals at L1 during the "April Fool’s Day" epoch: 28 March – 21 April 2001
W. Sun1, M. Dryer2,3, C. D. Fry2, C. S. Deehr1, Z. Smith3, S.-I. Akasofu4, M. D. Kartalev5, and K. G. Grigorov5
1Geophysical Institute, University of Alaska Fairbanks, Fairbanks, Alaska, USA
2Exploration Physics International, Inc., Milford, New Hampshire, USA
3NOAA Space Environment Center, Boulder, Colorado, USA
4International Arctic Research Center, University of Alaska Fairbanks, Fairbanks, Alaska, USA
5Institute of Mechanics, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria
Correspondence to: W. Sun (sun@jupiter.gi.alaska.edu)
Abstract. The Sun was extremely
active during the "April Fool’s Day" epoch of 2001. We chose this
period between a solar flare on 28 March 2001 to a final shock arrival at Earth
on 21 April 2001. The activity consisted of two presumed helmet-streamer
blowouts, seven M-class flares, and nine X-class flares, the last of which was
behind the west limb. We have been experimenting since February 1997 with
real-time, end-to-end forecasting of interplanetary coronal mass ejection (ICME)
shock arrival times. Since August 1998, these forecasts have been distributed
in real-time by e-mail to a list of interested scientists and operational USAF
and NOAA forecasters. They are made using three different solar wind models. We
describe here the solar events observed during the April Fool’s 2001 epoch,
along with the predicted and actual shock arrival times, and the ex post
facto correction to the real-time coronal shock speed observations. It
appears that the initial estimates of coronal shock speeds from Type II radio
burst observations and coronal mass ejections were too high by as much as 30%.
We conclude that a 3-dimensional coronal density model should be developed for
application to observations of solar flares and their Type II radio burst
observations.
Key words. Interplanetary physics
(flare and stream dynamics; interplanetary shocks) – Magnetosheric physics
(storms and substorms)
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