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A Direct Measurement of the Geomagnetic Cutoff for Cosmic Rays at Space Station Latitudes

Ogliore, R. C. and Mewaldt, R. A. and Leske, R. A. and Stone, E. C. and von Rosenvinge, T. T. (2001) A Direct Measurement of the Geomagnetic Cutoff for Cosmic Rays at Space Station Latitudes. In: Proceedings of the 27th International Cosmic Ray Conference. Vol.10. Copernicus Systems and Technology GmbH , Berlin, Germany, pp. 4112-4114.

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We report new measurements of the vertical geomagnetic cutoff for cosmic rays with rigidities from ~500 to 1700 MV, made using data from the MAST instrument on SAMPEX. A total of ~10,000 nuclei were used to measure the latitude cutoff in nineteen separate rigidity intervals. These results show that cosmic rays and solar particles can penetrate several degrees lower in latitude than would be estimated from commonly used relations for the geomagnetic cutoff, which has implications for the radiation exposure expected on the Space Station. An excellent fit to our measured cutoffs is given by the relation Rc = 15.062cos4 (Λ) - 0.363 GV, where Rc is the geomagnetic cutoff in rigidity, and λ is the invariant latitude. We suggest that this relation is useful over invariant latitudes from Λ = 0° to 64°, corresponding to rigidity cutoffs from ~0.2 to 15 GV.

Item Type:Book Section
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URLURL TypeDescription
Mewaldt, R. A.0000-0003-2178-9111
Leske, R. A.0000-0002-0156-2414
Stone, E. C.0000-0002-2010-5462
Additional Information:© Copernicus GmbH. This research was supported by NASA under grant NAS5-30704. During the summer of 1999, when most of this work was conducted, Ryan Ogliore was a student at Clarcmont-McKcnna College, working at Caltech as the recipient of a Caltech Summer Undergraduate Research Fellowship (SURF). We thank Georgia de Nolfo for helpful discussions and Jay Cummings for contributions to the data analysis routines.
Group:Space Radiation Laboratory
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Space Radiation Laboratory2001-18
Record Number:CaltechAUTHORS:20150302-113209743
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:55412
Deposited By: Deborah Miles
Deposited On:04 Mar 2015 17:19
Last Modified:20 Feb 2020 14:33

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