title: Two-step forecast of geomagnetic storm using coronal mass ejection and solar wind condition.
abstract: To forecast geomagnetic storms, we had examined initially observed parameters of coronal mass ejections (CMEs) and introduced an empirical storm forecast model in a previous study. Now we suggest a two-step forecast considering not only CME parameters observed in the solar vicinity but also solar wind conditions near Earth to improve the forecast capability. We consider the empirical solar wind criteria derived in this study (Bz≤ -5 nT orEy≥ 3 mV/m fort≥ 2 h for moderate storms with minimumDstless than -50 nT) and aDstmodel developed by Temerin and Li (2002, 2006) (TL model). Using 55 CME-Dstpairs during 1997 to 2003, our solar wind criteria produce slightly better forecasts for 31 storm events (90%) than the forecasts based on the TL model (87%). However, the latter produces better forecasts for 24 nonstorm events (88%), while the former correctly forecasts only 71% of them. We then performed the two-step forecast. The results are as follows: (i) for 15 events that are incorrectly forecasted using CME parameters, 12 cases (80%) can be properly predicted based on solar wind conditions; (ii) if we forecast a storm when both CME and solar wind conditions are satisfied (∩), the critical success index becomes higher than that from the forecast using CME parameters alone, however, only 25 storm events (81%) are correctly forecasted; and (iii) if we forecast a storm when either set of these conditions is satisfied (∪), all geomagnetic storms are correctly forecasted.
authors.affiliation: Astronomy and Space Program Division, Korea Astronomy and Space Science Institute Daejeon, South Korea.
authors.forename: R-S
authors.initials: RS
authors.lastname: Kim
authors.affiliation: School of Space Research, Kyung Hee University Yongin, South Korea.
authors.forename: Y-J
authors.initials: YJ
authors.lastname: Moon
authors.affiliation: Heliophysics Division, Goddard Space Flight Center Greenbelt, Maryland, USA.
authors.forename: N
authors.initials: N
authors.lastname: Gopalswamy
authors.affiliation: Astronomy and Space Program Division, Korea Astronomy and Space Science Institute Daejeon, South Korea.
authors.forename: Y-D
authors.initials: YD
authors.lastname: Park
authors.affiliation: Astronomy and Space Program Division, Korea Astronomy and Space Science Institute Daejeon, South Korea.
authors.forename: Y-H
authors.initials: YH
authors.lastname: Kim
keywords: coronal mass ejection; geomagnetic storm forecast; solar wind