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SAMPEX Observations of Energetic Hydrogen Isotopes in the Inner Zone

Looper, M. D. and Blake, J. B. and Cummings, J. R. and Mewaldt, R. A. (1996) SAMPEX Observations of Energetic Hydrogen Isotopes in the Inner Zone. Radiation Measurements, 26 (6). pp. 967-978. ISSN 1350-4487. doi:10.1016/S1350-4487(96)00098-4.

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We report observations of geomagnetically-trapped hydrogen isotopes at low altitudes, near the feet of field lines in the inner zone, made with the PET instrument aboard the SAMPEX satellite. We have mapped protons from 19 to 500 MeV, and have discovered a collocated belt of deuterons, which we have mapped from 18 to 58 MeV/nucleon. We found deuterium at about 1% of the level of the proton flux at the same energy per nucleon, and no tritium at energies of tens of MeV/nucleon with an upper limit of about 0.1% of the proton flux. Protons and deuterons showed similar time dependence, with fluxes approximately tripling from July 1992 to March 1996, and similar pitch-angle dependence. The high-L limits of the proton and deuteron belts as functions of energy were organized by rigidity, as was to be expected if these limits were set for both species by inability of particles to sustain adiabatic motion and stable trapping.

Item Type:Article
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URLURL TypeDescription DOIArticle
Mewaldt, R. A.0000-0003-2178-9111
Additional Information:© 1996 Elsevier Science Ltd. This work was supported by NASA at The Aerospace Corporation under NASA Cooperative Agreement 26979B and at the California Institute of Technology under contract NAS5-30704 and grant NAGW- 1919. One of us (MDL) was supported during the early part of this study by an NRC Research Associateship. The authors would like to acknowledge discussions with Richard Selesnick on many aspects of the analysis and modeling of SAMPEX radiation-belt measurements, and with Daniel Williams on the ion response of PET. Note added in proof-Since completing the work reported in this paper, we have reexamined the three-detector events shown in Figs 1 and 2. By including a consistency check on the three pulse heights, we have reduced the background level in Fig. 2 to the point that we can now detect tritium in this low-L region. The abundance at these energies (14-35 MeV/nuc) is about equal to the upper limit we set in the paper, or an eighth of the deuteron flux. This observation was presented at the 1996 COSPAR meeting in Birmingham, England.
Group:Space Radiation Laboratory
Funding AgencyGrant Number
NASA Cooperative Agreement26979B
NRC Research AssociateshipUNSPECIFIED
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Other Numbering System NameOther Numbering System ID
Space Radiation Laboratory1996-11
Issue or Number:6
Record Number:CaltechAUTHORS:20140703-213301160
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Official Citation:M.D. Looper, J.B. Blake, J.R. Cummings, R.A. Mewaldt, Sampex observations of energetic hydrogen isotopes in the inner zone, Radiation Measurements, Volume 26, Issue 6, November 1996, Pages 967-978, ISSN 1350-4487, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:46827
Deposited By: Deborah Miles
Deposited On:10 Jul 2014 23:03
Last Modified:10 Nov 2021 17:29

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