Characteristics of solar flares associated with interplanetary shock or nonshock events at Earth

Abstract

Solar flares and metric type II radio bursts are one kind of preliminary manifestations of solar disturbances and they are fundamental for predicting the arrival of associated interplanetary (IP) shocks at Earth. We statistically studied 347 solar flare type II radio burst events during 1997.2–2002.8 and found (1) only 37.5% of them were followed by the IP shocks at L1 (in other words, at Earth), the others without such IP shocks account for 62.5%; (2) the IP shocks associated with intense flares have large probability to arrive at Earth; (3) the IP shocks associated with central flares are more likely to arrive at Earth than those associated with the limb flares, and the most probable location for flares associated with IP shocks at Earth is W20°; and (4) there exists a east‐west asymmetry in the distribution of geoeffectiveness of flare‐associated IP shocks along the flare longitude. Most severe geomagnetic storms (Dstmin ≤ −100 nT) are usually caused by flare‐associated shocks originating from western hemisphere or middle regions near central meridian, and the most probable location for strong flares associated with more intense geomagnetic storms is W20° as well. These results could provide some criteria to estimate whether the associated shock would arrive at Earth and corresponding geomagnetic storm intensity.