Characterization of SEP events at high heliographic latitudes

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Proceedings titleSOLAR WIND TEN: Proceedings of the Tenth International Solar Wind Conference
Series titleAIP Conference Proceedings; no. 679
ConferenceTenth International Solar Wind Conference, June 17-31, 2002, Pisa, Italy
Pages656659; # of pages: 4
AbstractBetween February 2000 and May 2002, the Ulysses spacecraft made the first ever measurements of solar energetic particles (SEPs) at high heliographic latitudes. Nine large gradual SEP events were detected at latitudes greater than 45°, their signatures being clearest at high particle energies, i.e. protons >30 MeV and electrons >0.1 MeV. In this paper we measure the onset times of Ulysses high latitude events in several energy channels, and plot them versus inverse particle speed. We repeat the procedure for near Earth observations by Wind and SOHO. Velocity dispersion is observed in all the events near Earth and in most of them at Ulysses. The plots of onset times versus inverse speed allow to derive an experimental path length and time of release from the solar atmosphere. We find that the derived path lengths at Ulysses are longer than the length of a Parker spiral magnetic field line connecting it to the Sun, by a factor between 1.2–2.7. The time of particle release from the Sun is typically between 100 and 200 mins later than the relase time derived from in-ecliptic measurements. Unlike near Earth observations, Ulysses measurements are therefore not compatible with scatter-free propagation from the Sun to the spacecraft.
Publication date
AffiliationNational Research Council Canada; NRC Herzberg Institute of Astrophysics
Peer reviewedNo
NPARC number9720775
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Record identifier39565279-c710-498f-94f5-b4db21c089e0
Record created2009-07-17
Record modified2016-05-09
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