Solar source regions of coronal mass ejections and their geomagnetic effects

Citation
Sp. Plunkett et al., Solar source regions of coronal mass ejections and their geomagnetic effects, J ATMOS S-P, 63(5), 2001, pp. 389-402
Citations number
63
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Earth Sciences
Journal title
JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS
ISSN journal
1364-6826 → ACNP
Volume
63
Issue
5
Year of publication
2001
Pages
389 - 402
Database
ISI
SICI code
1364-6826(200103)63:5<389:SSROCM>2.0.ZU;2-4
Abstract
It is generally accepted that the fast interplanetary manifestations of cor onal mass ejections (ICMEs) are the major solar drivers of many space weath er phenomena, including large, non-recurrent geomagnetic storms and solar e nergetic particle events. High-quality synoptic observations of the solar c orona, as carried out by the EIT and LASCO experiments on SOHO, provide nea r real-time imaging of CMEs from the base of the corona out to a projected distance of 30R(circle dot) (R-circle dot is the solar radius). The average characteristics of CMEs observed by LASCO are similar to those from earlie r coronagraphs. Most CMEs travel with approximately constant speed through the LASCO field of view. However, a significant number accelerate as they m ove outward, and some fast events have been observed to decelerate. LASCO h as observed a great deal of internal structure in many CMEs. Concave-outwar d structures that are interpreted as magnetic flux ropes are observed in ap proximately one third of all events. Complex structures are often observed in the trailing portions of CMEs. Halo CMEs, many of which are very faint, can be routinely observed with LASCO. Extreme-ultraviolet (EW) images of th e low corona and solar disk, as recorded by EIT, reveal a complex web of CM E signatures. These include large-scale waves in the inner corona associate d with CMEs, extended regions of depleted EW intensity, and bright arcades that form following the occurrence of a CME. The combination of LASCO and E IT imagery allows the source regions of halo CMEs to be identified, and can be used to help predict the occurrence of geomagnetic disturbances several days in advance. The most important parameters in determining the geoeffec tiveness of an ICME are the magnetic field strength and direction, and the speed of the disturbance. The most intense geomagnetic storms are associate d with strong and persistent southward fields, either within the ICME itsel f or in the compressed sheath of solar wind plasma ahead of it. (C) 2001 El sevier Science Ltd. All rights reserved.