Signatures of interplanetary transients behind shocks and their associated near-surface solar activity

摘要

Interplanetary transients with particularsignatures different from the normal solar wind have been observed behindinterplanetary shocks and also without shocks. In this paper we have selectedfour well-known transient interplanetary signatures, namely: magnetic clouds,helium enhancements and bidirectional electron and ion fluxes, found in thesolar wind behind shocks, and undertaken a correlative study between them andthe corresponding solar observations. We found that although commonly differentsignatures appear in a single interplanetary transient event, they are notnecessarily simultaneous, that is, they may belong to different plasma regionswithin the ejecta, which suggests that they may be generated by complexprocesses involving the ejection of plasma from different solar regions. We alsofound that more than 90% of these signatures correspond to cases when anHα flare and/or the eruption of a filament occurred near solarcentral meridian between 1 and 4 days before the observation of the disturbanceat 1 AU, the highest association being with flares taking place between 2 and 3days before. The majority of the Hα flares were also accompanied bysoft X-ray events. We also studied the longitudinal distribution of theassociated solar events and found that between 80% and 90% of the interplanetaryejecta were associated with solar events within a longitudinal band of ±30°from the solar central meridian. An east-west asymmetry in the associated solarevents seems to exist for some of the signatures. We also look for coronal holesadjacent to the site of the explosive event and find that they were presentalmost in every case. Interplanetary physics · Interplanetaryshocks · Solar wind plasma · Solar physics · Flares and mass ejections