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Published March 25, 2010 | Published
Book Section - Chapter Open

Observations and Interpretations of Energetic Neutral Hydrogen Atoms from the December 5, 2006 Solar Event


We discuss recently reported observations of energetic neutral hydrogen atoms (ENAs) from an X9 solar flare/coronal mass ejection event on 5 December 2006, located at E79. The observations were made by the Low Energy Telescopes (LETs) on STEREO A and B. Prior to the arrival of the main solar energetic particle (SEP) event at Earth, both LETs observed a sudden burst of 1.6 to 15 MeV energetic neutral hydrogen atoms produced by either flare or shock-accelerated protons. RHESSI measurements of the 2.2-MeV γ-ray line provide an estimate of the number of interacting flare-accelerated protons in this event, which leads to an improved estimate of ENA production by flare-accelerated protons. Taking into account ENA losses, we find that the observed ENAs must have been produced in the high corona at heliocentric distances ≥ 2 solar radii. Although there are no CME images from this event, it is shown that CME-shock-accelerated protons can, in principle, produce a time-history consistent with the observations.

Additional Information

© 2010 American Institute of Physics. Issue Date: 25 March 2010. This work was supported by NASA at Caltech and JPL under sub-contract SA2715-26309 from UC Berkeley under NASA contract NAS5-03131. The work at MSFC was supported by the TEI Program of NASA's Office of Chief Engineer. We thank NOAA for GOES X-ray data and appreciate discussions with Hugh Hudson, Sam Krucker, Gang Li, Bob Lin, Ron Murphy and Gerry Share.

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