Timing of Injections of Relativistic Protons and Electrons in the 20 January 2005 Flare

Details Timing of Injections of Relativistic Protons and Electrons in the 20 January 2005 Flare Timing of Injections of Relativistic Protons and Electrons in the 20 January 2005 Flare

Dec 2005

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2005agufmsh23a0319s&link_type=abstract

American Geophysical Union, Fall Meeting 2005, abstract #SH23A-0319

Astronomy and Astrophysics

Astrophysics

7513 Coronal Mass Ejections (2101), 7514 Energetic Particles (2114), 7519 Flares, 7534 Radio Emissions

Scientific paper

The injection of relativistic protons and electrons in the extraordinarily prompt and intense solar energetic particle (SEP) event of 20 January 2005 may be examined from 1AU with ~1-minute time resolution because the Earth was magnetically well-connected to the injection region, so that the pitch-angle distributions of the SEPs were strongly collimated along the interplanetary magnetic field whose solar foot point was close to the location of the importance 2B (X7.1) flare at N12W58. By a fortunate circumstance, the magnetic field at Earth was almost south-to-north during the onset of the neutron monitor ground level event (GLE). The much larger response of the south polar stations (Bartol Research Institute) indicated unambiguously that the relativistic (~2 GeV) protons had strong beam-like pitch-angle distributions. The multiple-head ACE/EPAM detectors indicated that the (~235 keV) electrons were also beam-like. The first-arriving particles would have transit times along a nominal Parker field of 9.6 min (protons) and 12.2 min (electrons). By comparing the injection times of these particles with the start times of the electro-magnetic emissions and the launch of the west-limb CME, we can place constraints on the particle acceleration/release process. The CME launch was estimated from a SOHO/LASCO C2 image (0654 UT) with the assumption that the CME velocity was 2500 km/s, consistent with the last undisturbed SOHO/EIT image at 0636 UT. All the start times (at the Sun) for these emissions are given by Simnett ( Astron. Astrophys., 2005): 15.4 GHz--0627; SXR(1-8A)--0628; HXR(40keV)--0630; CME-->0632; Flare(2B)--0633; gammas(4-7MeV)--0636; typeIII(14MHz)--0637; protons(2GeV)--0639; electrons(235keV)--0645. The electron injection is delayed 6 min after the proton injection, 8 min after the type III burst, and 15 min after the start of the hard xrays, while the proton injection is 3 min after the prompt gamma rays (excitation of C and O). Therefore if the first arriving particles are all accelerated in the flare process, we must explain all the delays of the near-relativistic electrons. Alternatively, if the particles are accelerated by a CME-driven shock (~2500 km/s), their injection altitudes would have to be different: <1.4 Rs (protons) and<2.6 Rs above the solar surface. In order to sort out these alternatives, further diagnostics (such as the subsequent time histories of the particles and their energy spectra) are being examined in detail.

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