Astronomy and Astrophysics – Astrophysics
Scientific paper
May 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008agusmsh41b..05k&link_type=abstract
American Geophysical Union, Spring Meeting 2008, abstract #SH41B-05
Astronomy and Astrophysics
Astrophysics
7514 Energetic Particles (2114), 7549 Ultraviolet Emissions
Scientific paper
The Ultraviolet Coronagraph Spectrometer (UVCS) on the Solar and Heliospheric Observatory is being used to measure precise coronal H I Ly-alpha spectral line profiles out to several Doppler half widths. Such observations can be used to reveal the proton velocity distribution along the line-of-sight. Departures from a Maxwellian distribution are believed to be needed for the acceleration of solar energetic particles (SEPs) by coronal mass ejection (CME) shocks. We have now completed all required instrument characterizations and refined the observations to the point where it is possible to distinguish a Gaussian coronal velocity distribution from a power law tail of sufficient strength to accelerate SEPs. It is generally believed that the required seed particle population needed to produce SEPs of interest with a CME shock would have a velocity distribution with 0.001 to 0.01 of the particles with speeds that exceed 1000 km/s. Assuming a kappa distribution that is symmetric in the tangential plane and Maxwellian in the radial direction, this would correspond to a distribution with kappa = 3.5 or smaller. We show that UVCS observations can distinguish a Gaussian from a kappa of 4 or less. This paper will report the results of examining observations during 2006-2008 and report on any departures from a Maxwellian distribution. It will also report the CME/flare predecessor history of each observation. This work is supported by the National Aeronautics and Space Administration (NASA) under Grant NNX07AL72G to the Smithsonian Astrophysical Observatory.
Cranmer Steven R.
Gardner Larry D.
Kohl John L.
Panasyuk Alexander V.
Raymond John C.
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