Astronomy and Astrophysics – Astrophysics
Scientific paper
Aug 1999
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1999a%26a...348..271k&link_type=abstract
Astronomy and Astrophysics, v.348, p.271-285 (1999)
Astronomy and Astrophysics
Astrophysics
26
Sun: Activity, Sun: Corona, Sun: Flares, Sun: Particle Emission, Sun: Radio Radiation
Scientific paper
It is widely believed that the longest lasting and most energetic solar energetic particle events (SEPs) observed in interplanetary space result from acceleration by the bow shocks of coronal mass ejections (CMEs). Using gamma-ray, X-ray and radio diagnostics of interacting particles and spaceborne and ground-based detection of >=20 MeV protons at 1 AU during two large events (1989 September 29 and October 19), we demonstrate that time-extended acceleration processes in the low and middle corona, far behind the CME, leave their imprints in the proton intensity time profiles in interplanetary space for one to several hours after the onset of the flare: (1) New increases of >=20 MeV proton fluxes at 1 AU can be traced back to episodes of coronal acceleration. (2) Increasing richness of relativistic protons observed at 1 AU in the course of the SEPs is associated with new coronal particle injection after the impulsive phase. (3) Particle injection sites enabling a rapid access to the well-connected magnetic field line, as required by the SEP time profile, exist in the middle corona even if the nominal Hα flare location is far away. These findings suggest that contrary to the prevalent view acceleration processes in the low and middle corona supply both interacting and at least part of the interplanetary particles. The association of the most proton-rich component of the SEPs with delayed low-frequency radio emission is consistent with ionization state studies of SEPs, in that both require acceleration in a tenuous plasma. We conclude that the complexity of the corona provides the ingredients for the acceleration of particles and their injection into a large range of heliocentric angles. The CME may play the role of a trigger or even contribute to the buildup of magnetic stresses in the corona, but its bow shock is not the main accelerator of the high-energy protons.
Chupp Edward L.
Dunphy Philip P.
Klein Karl-Ludwig
Magun Andreas
Rieger Erich
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