Dynamic geomagnetic rigidity cutoff variations during a solar proton event

Rodger, Craig J.; Clilverd, Mark A. ORCID:; Verronen, Pekka T.; Ulich, Thomas; Jarvis, Martin J.; Turunen, Esa. 2006 Dynamic geomagnetic rigidity cutoff variations during a solar proton event. Journal of Geophysical Research, 111 (A4), A04222. 12, pp.

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Solar proton events (SPE) are major, though infrequent, space weather phenomena that can produce hazardous effects in the near-Earth space environment. A detailed understanding of their effects depends upon knowledge of the dynamic rigidity cutoffs imposed by the changing total magnetic field. For the first time we investigate detailed comparisons between theoretical cutoff rigidities and ground-based measurements during the large geomagnetic disturbance of 4–10 November 2001. We make use of the imaging riometer (IRIS) at Halley, Antarctica, fortunately situated such that the rigidity cutoff sweeps back and forth across the instrument's field of view during the SPE period. The Kp-dependent geomagnetic rigidity cutoff energies are determined from satellite observations combined with previously reported particle-tracing results. We find that the predicted absorption levels show good agreement with those experimentally observed for low and middle levels of geomagnetic disturbance (Kp < 5). However, during more disturbed geomagnetic conditions the cutoff modeling overestimates the stretching of the geomagnetic field, underestimating the rigidity cutoff energies, and hence leading to riometer absorption predictions that are too high. In very disturbed conditions (Kp ≈ 7–9) the rigidity energy cutoffs indicated by the IRIS observations appear to be equivalent to those predicted for Kp ≈ 6 by the particle-tracing approach. Examples of changing rigidity cutoff contours for increasing levels of geomagnetic disturbance are presented.

Item Type: Publication - Article
Digital Object Identifier (DOI):
Programmes: BAS Programmes > Global Science in the Antarctic Context (2005-2009) > Sun Earth Connections
ISSN: 0148-0227
Format Availability: Electronic, Print
Additional Information. Not used in RCUK Gateway to Research.: Full text not available from this repository
NORA Subject Terms: Space Sciences
Date made live: 17 Aug 2007 12:29 +0 (UTC)

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