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Published 2012 | Published
Book Section - Chapter Open

Investigating the longitude dependence of solar energetic particle spectra


We examine the traits of six solar energetic particle events observed simultaneously by instruments on ACE and at least one of the twin STEREO spacecraft. We compare the time profiles and spectra of energetic oxygen as a function of the longitudinal separation of the observer from the solar source region. We find systematic trends in the rise and peak times with source longitude that are consistent with those determined from single spacecraft studies. However, we also find two events where the rise times were surprisingly rapid when the source region was over the western limb relative to the observer. This has potential consequences for space weather predictions of radiation hazards. No clear trend is apparent for hardness of the event-integrated spectra with source longitude contrary to trends seen in the single spacecraft studies.

Additional Information

© 2012 American Institute of Physics. This work was supported by NASA under grants NNX08AI11G and NNX10AQ68G at Caltech, NNX10AT75G at JHUAPL, subcontracts SA2715-26309 from UC Berkeley (NASA contract NAS5-03131) and by NSF grant AGS-1156004. We thank Nariaki Nitta for useful discussions regarding solar source identifications.

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