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Ann. Geophys., 20, 997-1005, 2002
www.ann-geophys.net/20/997/2002/
© European Geosciences Union 2002
Comparisons of high latitude E > 20 MeV proton geomagnetic cutoff observations with predictions of the SEPTR model
S. Kahler1 and A. Ling2
1Air Force Research Laboratory, Space Vehicles Directorate, Hanscom Air Force Base, Massachusetts 01731, USA
2Radex Corporation, 3 Preston Court, Bedford, Massachusetts 01730, USA
Correspondence to: S. Kahler
(stephen.kahler@hanscom.af.mil)
Abstract. Radiation effects from
solar energetic proton (SEP) events are a concern when the International Space
Station reaches high latitudes accessible to SEPs. We use data from the 20–29
and 29–64 MeV proton channels of the Proton/Electron Telescope on the SAMPEX
satellite during nine large SEP events to determine the experimental geographic
cutoff latitudes for the two energy ranges. These are compared with calculated
cutoff latitudes based on a computer model, SEPTR (solar energetic particle
tracer). The observed cutoff latitudes are systematically equatorward of the
latitudes calculated by the SEPTR program using a Tsyganenko field model, but
that model produces mean values of ~ 2° for latitudinal differences with
observations, DLat, which are ~ 3 times smaller than
those using the 1995 International Geomagnetic Reference Field model alone. The
number distributions of DLat are peaked near 0° and
decline toward higher values. With the Tsyganenko model, we find no significant
trend in either the DLat or their variances with
increasing Kp .
Key words. Interplanetary physics
(energetic particles) – Magnetospheric physics (polar cap phenomena) –
Space plasma physics (charged particle motion and acceleration)
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