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Temporal Variations in Solar Energetic Particle Events

von Rosenvinge, T. T. and Christian, E. R. and Cohen, C. M. S. and Cummings, A. C. and Leske, R. A. and Mewaldt, R. A. and Stone, E. C. and Slocum, P. L. and Wiedenbeck, M. E. (2001) Temporal Variations in Solar Energetic Particle Events. In: Proceedings of the 27th International Cosmic Ray Conference. Vol.8. Copernicus Systems and Technology GmbH , Berlin, Germany, pp. 3136-3138.

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The Solar Isotope Spectrometer (SIS) on-board the Advanced Composition Explorer (ACE) spacecraft has measured elemental abundances in large solar energetic particle (SEP) events as a function of time for more than 25 such events. There are large temporal variations in the observed abundances within events, from event to event, and as a function of particle energy. Such variations have been previously attributed to the combination of an initial impulsive phase having enhanced heavy element abundances with a longer gradual phase with coronal abundances. More recently they have been attributed to rigidity dependent escape from CME-driven shocks through plasma waves generated by wave-particle interactions. Both these models can be expected to depend upon solar longitude since impulsive events are associated with longitudes well-connected magnetically to the observer, and shock properties and connection of the observer to the shock are also longitude dependent. We present evidence of longitude related variations. In addition, we show that there are events with little time variation and heavy element enhancements similar to those of impulsive events. These events appear to be difficult to explain in current models in which particles are accelerated with coronal abundances. Rather, these events seem to require abundance enhancements either in the source material or in the acceleration process.

Item Type:Book Section
Related URLs:
URLURL TypeDescription
Christian, E. R.0000-0003-2134-3937
Cohen, C. M. S.0000-0002-0978-8127
Cummings, A. C.0000-0002-3840-7696
Leske, R. A.0000-0002-0156-2414
Mewaldt, R. A.0000-0003-2178-9111
Stone, E. C.0000-0002-2010-5462
Wiedenbeck, M. E.0000-0002-2825-3128
Additional Information:© Copernicus Gesellschaft 2001. This research was supported by the National Aeronautics and Space Administration at the Goddard Space Flight Center, the California Institute of Technology (under grant NAG5-6912), and the Jet Propulsion Laboratory. TvR acknowledges assistance from Hilary Cane with determining associated solar event locations.
Group:Space Radiation Laboratory
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Space Radiation Laboratory2001-42
Record Number:CaltechAUTHORS:20150303-100220896
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:55458
Deposited By: Deborah Miles
Deposited On:04 Mar 2015 17:09
Last Modified:09 Mar 2020 13:19

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