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An Improved Model for Relativistic Solar Proton Acceleration Applied to the 2005 January 20 and Earlier Events


Bombardieri, DJ and Duldig, ML and Humble, JE and Michael, KJ, An Improved Model for Relativistic Solar Proton Acceleration Applied to the 2005 January 20 and Earlier Events, The Astrophysical Journal, 682, (2) pp. 1315-1327. ISSN 0004-637X (2008) [Refereed Article]

DOI: doi:10.1086/589494


This paper presents results on modeling the ground-level response of the higher energy protons for the 2005 January 20 ground-level enhancement (GLE). This event, known as GLE 69, produced the highest intensity of relativistic solar particles since the famous event on 1956 February 23. The location of recent X-ray and -ray emission (N14 W61 ) was near Sun-Earth connecting magnetic field lines, thus providing the opportunity to directly observe the acceleration source from Earth. We restrict our analysis to protons of energy 450 MeV to avoid complications arising from transport processes that can affect the propagation of low-energy protons. In light of this revised approach we have reinvestigated two previous GLEs: those of 2000 July 14 (GLE 59) and 2001 April 15 (GLE 60). Within the limitations of the spectral forms employed, we find that from the peak (06:55 UT) to the decline (07:30 UT) phases of GLE 69, neutronmonitor observations from450MeVto 10 GeVare best fitted by the Gallegos-Cruz&Perez- Peraza stochastic acceleration model. In contrast, the Ellison & Ramaty spectra did not fit the neutron monitor observations as well. This result suggests that for GLE 69, a stochastic process cannot be discounted as a mechanism for relativistic particle acceleration, particularly during the initial stages of this solar event. For GLE 59 we find evidence that more than one acceleration mechanism was present, consistent with both shock and stochastic acceleration processes dominating at different times of the event. For GLE 60 we find that Ellison & Ramaty spectra better represent the neutron monitor observations compared to stochastic acceleration spectra. The results for GLEs 59 and 60 are in agreement with our previous work.

Item Details

Item Type:Refereed Article
Keywords:acceleration of particles — cosmic rays — Sun: particle emission
Research Division:Physical Sciences
Research Group:Astronomical sciences
Research Field:Solar physics
Objective Division:Expanding Knowledge
Objective Group:Expanding knowledge
Objective Field:Expanding knowledge in the physical sciences
UTAS Author:Bombardieri, DJ (Dr Daniel Bombardieri)
UTAS Author:Duldig, ML (Dr Marc Duldig)
UTAS Author:Humble, JE (Dr John Humble)
UTAS Author:Michael, KJ (Dr Kelvin Michael)
ID Code:54336
Year Published:2008
Web of Science® Times Cited:37
Deposited By:IASOS
Deposited On:2009-02-17
Last Modified:2015-02-10

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