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The Influence of Short-Term Solar Activity on the Proton Flux Measured by AMS during Solar Cycle 24.

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Title:The Influence of Short-Term Solar Activity on the Proton Flux Measured by AMS during Solar Cycle 24.
Authors:Whitman, Kathryn
Contributors:Physics (department)
Keywords:AMS-02
solar energetic particles
Forbush decreases
solar activity
Date Issued:Aug 2017
Publisher:University of Hawaiʻi at Mānoa
Abstract: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.
Description:Ph.D. Thesis. University of Hawaiʻi at Mānoa 2017.
URI:http://hdl.handle.net/10125/62679
Rights:All UHM dissertations and theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission from the copyright owner.
Appears in Collections: Ph.D. - Physics


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