AAS 204th Meeting, June 2004
Session 2 When the Sun Went Wild
SPD Topical Related Poster, Monday, May 31, 2004, 9:20am-6:30pm, Ballroom

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[2.20] Ground Level Detection of SEPs and Forbush Decreases in October and November 2003

J.M. Ryan (UNH), Milagro Collaboration

Milagro, the ground level TeV gamma-ray telescope, is sensitive to solar energetic particles and Forbush decreases. Milagro sits in the Jemez mountains at an altitude of 2630 m in northern New Mexico and has detected and measured TeV gamma-ray emission from various objects and SEPs in earlier GLEs. By measuring count rates due to secondary muons and electromagnetic showers, Milagro can be used to investigate SEPs and galactic CR modulations. On 2003 October 29 Milagro registered a major Forbush decrease at various thresholds beyond 5 GV. Visual inspection of the data reveals the Forbush decrease in at least three independent channels coinciding with the decrease registered at several neutron monitor stations. Since the count rates are primarily those for secondary muons, significant barometric and diurnal corrections are necessary. A preliminary correction for these effects has been performed revealing a Forbush decrease greater than 10% at 5 GV. Different detection modes possess different energy thresholds. The analysis of some of these channels addresses the rigidity dependence of the decrease and subsequent recovery. We will present data and preliminary analyses of the Forbush decrease and recovery. We will also present evidence for any ground-level solar energetic particles in and around 2003 October 29.

The author(s) of this abstract have provided an email address for comments about the abstract: james.ryan@unh.edu

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