Dissertation/Thesis Abstract

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The Influence of Short-Term Solar Activity on the Proton Flux Measured by Ams During Solar Cycle 24
by Whitman, Kathryn, Ph.D., University of Hawai'i at Manoa, 2017, 322; 10757803
Abstract (Summary)

The Alpha Magnetic Spectromer (AMS), a particle detector onboard the International Space Station (ISS), measures cosmic rays (CR) in the rigidity range of 0.8 GV to the TV (≈ 300 MeV/nuc into the TeV) with unprecedented precision and high statistics. The particle flux in the lower part of this rigidity range is influenced by short-term solar activity resulting from the most explosive events on the sun, M and X-class flares and fast coronal mass ejections (CME) with velocities > 800 km/s. The primary responses are temporary decreases in the galactic cosmic ray (GCR) flux which last on the order of days, called Forbush decreases (FD), and temporary increases in flux which last on the order of hours to days due to the arrival of solar energetic particles (SEP).

It is still an open question as to how FDs behave with rigidity and how this behavior is related to disturbances measured in the solar wind. In this thesis, we present high-precision AMS proton fluxes for selected FDs with detailed information about FD behavior with rigidity and search for new correlations between FD characteristics and solar wind parameters. In addition, the background fluctuations in the AMS daily proton flux due to variability in the solar wind are quantified and the modified Force-Field Approximation from Corti et al. (2015) is compared with data.

The second major portion of this thesis work is the measurement and analysis of SEP protons in an energy range and at a precision that have never before been available. We present AMS SEP proton fluxes for nine SEP events in solar cycle 24 that accelerated particles to rigidities above 0.8 GV. These AMS measurements are combined with SOHO and GOES-13 data to create SEP spectra between 0.1 - ∼ 2 GV which are compared with physics-based models and functions that represent different SEP acceleration mechanisms. This research program has taken advantage of AMS’s innovative technology and location above the atmosphere to provide brand new information to the heliophysics community about SEPs, which is currenty unavailable in the public domain from any other satellite. vii

Indexing (document details)
Advisor: Bindi, Veronica
School: University of Hawai'i at Manoa
School Location: United States -- Hawaii
Source: DAI-B 79/07(E), Dissertation Abstracts International
Subjects: Astrophysics, Physics
Keywords: AMS-02, Forbush decreases, SEP, Solar activity, Solar energetic particles
Publication Number: 10757803
ISBN: 9780355601138
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