Gamma-Ray Line Observations of the 2000 July 14 Flare and SEP Impact on the Earth |
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| Authors: | Share GH Murphy RJ Tylka AJ Schwartz RA Yoshimori M Suga K Nakayama S Takeda H |
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| Institution: | (1) Naval Research Laboratory, E.O. Hulburt Center for Space Research, Washington;(2) Raytheon ITSS, LASP, NASA Goddard Space Flight Center, Greenbelt, MD, 20771, U.S.A;(3) Department of Physics, Rikkyo University, Toshima-ku, Tokyo 171-8501, Japan |
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| Abstract: | The HXS and GRS detectors on Yohkoh observed the 14 July 2000, X5.7 flare, beginning at ∼ 10:20 UT, ∼ 4 min before the peak in soft X-rays. The hard X-rays and
γ-rays peaked ∼ 3 min later at ∼ 10:27 UT. Solar γ-ray emission lasted until ∼ 10:40 UT. Impact of high-energy ions at the
Sun is revealed by the γ-ray lines from neutron capture, annihilation radiation and de-excitation that are visible above the
bremsstrahlung continuum. From measurement of these lines we find that the flare-averaged spectrum of accelerated protons
is consistent with a power law ge10 MeV with index 3.14±0.15 and flux 1.1×1032 protons MeV−1 at 10 MeV. We estimate that there were ∼1.5×1030 erg in accelerated ions if the power law extended without a break down to 1 MeV; this is about 1% of the energy in electrons
> 20 keV from measurements of the hard X-rays. We find no evidence for spectral hardening in the hard X-rays that has been
suggested as a predictor for the occurrence of solar energetic particle (SEP) events. This was the third largest proton event
above 10 MeV since 1976. The GRS and HXS also observed γ-ray lines and continuum produced by the impact of SEP on the Earth's
atmosphere beginning about 13 UT on 14 July. These measurements show that the SEP spectrum softened considerably over the
next 24 hours. We compare these measurements with proton measurements in space. |
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