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| Titel |
Multi-spacecraft observations of solar energetic particle events in the rising phase of solar cycle 24: Longitudinal and radial intensity gradients |
| VerfasserIn |
D. Lario, E. C. Roelof, G. C. Ho |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250067967
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| Zusammenfassung |
| The current fleet of spacecraft spread throughout the inner heliosphere (i.e., STEREO-A,
STEREO-B, ACE, SOHO, and MESSENGER) allows us to estimate the longitudinal
and radial gradients in intensity of solar energetic particle (SEP) events during the
rise of solar cycle 24. Simultaneous measurements of individual SEP events by
two or more of the first four of the above spacecraft (all near 1 AU) allow us to
infer the longitudinal gradient of SEP peak intensities. Distributions of the peak
intensities for the events with identifiable solar origin are approximated by the form
exp[-k(Ï-Ï0)2], where Ï is the longitudinal separation between the parent active region
and the footpoint of the field line connecting each spacecraft with the Sun, Ï0 is the
distribution centroid and k determines the longitudinal gradient. Those events for
which MESSENGER is nominally connected along the interplanetary magnetic
field to one of the spacecraft near 1 AU allow us to infer a lower limit to the radial
intensity gradient along magnetic field lines. During the decay phase of the events,
periods of similar intensities are commonly observed by spacecraft well separated in
longitude and, when connection to MESSENGER permits, by spacecraft along the same
nominal interplanetary field line. Those periods of null intensity gradients are known
as energetic particle reservoirs. Observations of radial and longitudinal intensity
gradients as well as energetic particle reservoirs made by Helios during solar cycle 21
[Lario et al., ApJ, 653, 1531-1544, 2006] provide an important point of comparison. |
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