A Caltech Library Service

Variability of spectra in large solar energetic particle events

Cohen, C. M. S. and Mewaldt, R. A. and Cummings, A. C. and Leske, R. A. and Stone, E. C. and von Rosenvinge, T. T. and Wiedenbeck, M. E. (2003) Variability of spectra in large solar energetic particle events. Advances in Space Research, 32 (12). pp. 2649-2654. ISSN 0273-1177. doi:10.1016/S0273-1177(03)00901-3.

Full text is not posted in this repository. Consult Related URLs below.

Use this Persistent URL to link to this item:


Using data from the Solar Isotope Spectrometer on the Advanced Composition Explorer obtained during 36large solar energetic particle events (SEPs) that occurred during 1997–2002 we have examined the spectral characteristics of oxygen and iron. Based on the shape of the oxygen spectrum during the decay phase following the peak in particle intensity, each SEP event was categorized as either exponential (7 events) or power law (29 events). We find that the exponential events were typically the larger events (in terms of peak oxygen intensity) and had Fe/O ratios that strongly decreased with increasing energy. Event-averaged Fe/O ratios (integrated over 12 to 60 MeV/nucleon) were at or below coronal abundances for nearly all these events, while the ratios obtained in the power law events were typically enhanced over coronal values. The majority of the power law events had the same spectral index for both O and Fe resulting in an Fe/O ratio independent of energy. However 6 of the 29 power law events had Fe/O ratios that increased with increasing energy due to an Fe spectral index less negative than that of O. We consider simple diffusion theory in an effort to understand the nature of these events and obtain preliminary but promising results.

Item Type:Article
Related URLs:
URLURL TypeDescription
Cohen, C. M. S.0000-0002-0978-8127
Mewaldt, R. A.0000-0003-2178-9111
Cummings, A. C.0000-0002-3840-7696
Leske, R. A.0000-0002-0156-2414
Stone, E. C.0000-0002-2010-5462
Wiedenbeck, M. E.0000-0002-2825-3128
Additional Information:© 2003 Elsevier Ltd on behalf of COSPAR. Manuscript received 02 December, 2002; revised 01 April, 2003; accepted 01 May, 2003. This research was supported by NASA at the California Institute of Technology (under grant NAG5-6912) the Jet Propulsion Laboratory, and the Goddard Space Flight Center.
Group:Space Radiation Laboratory
Funding AgencyGrant Number
Goddard Space Flight CenterUNSPECIFIED
Other Numbering System:
Other Numbering System NameOther Numbering System ID
Space Radiation Laboratory2003-53
Issue or Number:12
Record Number:CaltechAUTHORS:20140827-090049799
Persistent URL:
Official Citation:Cohen, C. M. S., Mewaldt, R. A., Cummings, A. C., Leske, R. A., Stone, E. C., von Rosenvinge, T. T., & Wiedenbeck, M. E. (2003). Variability of spectra in large solar energeticparticle events. Advances in Space Research, 32(12), 2649-2654. doi:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:48964
Deposited On:27 Aug 2014 17:31
Last Modified:10 Nov 2021 18:38

Repository Staff Only: item control page