Other
Scientific paper
Dec 2006
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006agufmsh54a..02r&link_type=abstract
American Geophysical Union, Fall Meeting 2006, abstract #SH54A-02
Other
2149 Mhd Waves And Turbulence (2752, 6050, 7836), 7513 Coronal Mass Ejections (2101), 7514 Energetic Particles (2114), 7519 Flares
Scientific paper
A focused transport equation for solar energetic particles is sufficiently complex that simple analytic approximations are generally inadequate, but the physics is sufficiently well established to permit precise numerical modeling of high energy particle observations at various distances from the Sun. We demonstrate how observed profiles of intensity and anisotropy vs. time can be quantitatively fit to determine an optimal injection profile at the Sun, scattering mean free path λ, and magnetic configuration. For several ground level enhancements (GLE) of solar energetic particles at energies ~ 1 GeV, the start time of injection has been determined to 1 or 2 minutes. In each case this start time coincides, within that precision, to the soft X-ray peak time, when the flare's primary energy release has ended. This is not inconsistent with acceleration at a coronal mass ejection (CME)-driven shock, though the rapid timescale is challenging to understand. For the GLE of 2005 January 20, λ decreases substantially over ~ 10 minutes, which is consistent with concepts of proton-amplified waves. The GLE of 2000 July 14 is properly fit only when a magnetic bottleneck beyond Earth is taken into account, a feature later confirmed by NEAR observations. The long-standing puzzle of the 1989 October 22 event can now be explained by simultaneous injection of relativistic solar particles along both legs of a closed interplanetary magnetic loop, while other reasonable explanations fail the test of quantitative fitting. The unusually long λ (confirming many previous reports) and a low turbulent spectral index hint at unusual properties of turbulence in the loop. While the early GLE peak on 2003 October 28 remains a mystery, the main peak's strong anisotropy is inconsistent with a suggestion of injection along the far leg of a magnetic loop; quantitative fitting fails because of reverse focusing during Sunward motion. With these modeling capabilities, one is poised to take full advantage of future particle observations at various distances, as well as STEREO observations of magnetic clouds, which should provide important guidance for modeling to refine our understanding of the magnetic topology underlying the particle transport. Partially supported by the Thailand Research Fund, a post-doctoral grant from Mahidol University, NSF Grant ATM-0527878, and the Rachadapisek Sompoj Fund of Chulalongkorn University.
Bieber John W.
Evenson Paul
Khumlumlert Thiranee
Pyle Roger
Ruffolo David
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