Coronal Holes, Jets, and the Origin of (3)He-rich Particle Events
Using magnetograph measurements, coronal field extrapolations, and imaging observations, we investigate the solar origins of 25 (3)He-rich particle events from the period 1997-2003. In essentially every case we find that the source of the impulsive solar energetic particles (SEPs) lies next to a cor...
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Veröffentlicht in: | The Astrophysical journal 2006-03, Vol.639 (1), p.495-509 |
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Format: | Artikel |
Sprache: | eng |
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Zusammenfassung: | Using magnetograph measurements, coronal field extrapolations, and imaging observations, we investigate the solar origins of 25 (3)He-rich particle events from the period 1997-2003. In essentially every case we find that the source of the impulsive solar energetic particles (SEPs) lies next to a coronal hole containing Earth-directed open field lines. Averaged over all events, the source-hole separation is only 64' at the photosphere. The source itself is typically a small, flaring active region located between longitudes 6W25 and 6W72. Around the estimated particle injection time, EUV images often show a jetlike ejection aligned with the open field lines. In some cases, a corresponding white-light jet is seen at heliocentric distances 2 R( , similar to those studied earlier by Wang & Sheeley. The jets show a tendency to recur, a behavior that is reflected in the time variation of the measured (3)He and Fe particle intensities. We interpret the jets as signatures of magnetic reconnection ("footpoint exchange") between closed and open field lines. On the basis of these findings, we expect (3)He enrichments to be observed whenever Earth-connected open field lines undergo footpoint exchanges with nearby active or ephemeral region fields. Because small bipoles emerge continually inside coronal holes, moderate enhancements in the (3)He level can occur even when no significant flaring activity is recorded. |
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ISSN: | 0004-637X |
DOI: | 10.1086/499355 |