Characterization of SEP events at high heliographic latitudes
Characterization of SEP events at high heliographic latitudes
复制标题
高日照纬度 SEP 事件的特征
DOI:
10.1063/1.1618680
复制
发表时间:
2003
期刊:
影响因子:
2.8
通讯作者:
R. B. Mckibben
中科院分区:
文献类型:
--
作者:
S. Dalla;A. Balogh;S. Krucker;A. Posner;R. Müller;J. Anglin;M. Y. Hofer;R. Marsden;T. Sanderson;B. Heber;Ming Zhang;R. B. Mckibben
Between 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 10...