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Charge State Measurements of Solar Energetic Particles Observed with SAMPEX

Mason, G. M. and Mazur, J. E. and Looper, M. D. and Mewaldt, R. A. (1995) Charge State Measurements of Solar Energetic Particles Observed with SAMPEX. Astrophysical Journal, 452 . pp. 901-911. ISSN 0004-637X. doi:10.1086/176358.

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We have measured the ionization states of major elements accelerated in two large solar energetic particle events by use of the geomagnetic cutoff technique. The observations were made in 1992 October/November using instrumentation on the SAMPEX satellite, which is in an 82° inclination low Earth orbit. We calibrate the geomagnetic cutoff rigidity by assuming that protons and He observed on SAMPEX are fully stripped. The mean charge states of the heavier elements are then determined from their measured cutoffs, along with this calibrated scale. Our results cover the energy range ~0.5-5 MeV nucleon^(-1) and are in good agreement with earlier studies by Luhn et al. (1985) near -1 MeV nucleon^(-1) in all cases except for Fe. We find a mean charge state of 11.04±0.22 for Fe, while the average from Luhn is 14.09±0.09. The lower ionization state of Fe reported here appears to be consistent with the general range of values recently measured in solar wind Fe on the Ulysses deep space probe. Although the observational picture is still incomplete, overall the present results confirm and extend previous evidence that the solar energetic particles in large events are accelerated from the coronal or solar wind material.

Item Type:Article
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Mason, G. M.0000-0003-2169-9618
Mewaldt, R. A.0000-0003-2178-9111
Additional Information:© 1995. The American Astronomical Society. Received 1995 January 23; accepted 1995 May 1. We thank the members of the Space Physics Group at the University of Maryland Department of Physics and the Caltech Space Radiation Laboratory who designed, constructed, and calibrated the LICA and PET instruments; and the Small Explorer Project Office at Goddard Space Flight Center for the construction and launch of the SAMPEX spacecraft. This work was supported by NASA under contract NAS5-30704.
Group:Space Radiation Laboratory
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Space Radiation Laboratory1995-39
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ID Code:46377
Deposited By: Deborah Miles
Deposited On:20 Jun 2014 18:41
Last Modified:10 Nov 2021 17:24

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