Dependence of the decay phase of solar energetic electron events on the large-scale IMF structure:: ACE observations -: art. no. 2079

Using recent measurements of energetic electrons (greater than or equal to38 keV) by the ACE/EPAM experiment, we examine the dependence of the characteristic decay time of two impulsive solar electron events on the large-scale structure of the Interplanetary Magnetic Field ( IMF) within which the electrons are emitted. The technique of mapping the solar wind and extrapolating the frozen-in magnetic field is used to obtain the large-scale IMF structure within and beyond the location of the ACE spacecraft. We find that the electron event that occurred within a converging IMF structure exhibits a remarkably longer decay phase compared to the electron event observed inside a diverging IMF configuration. The observations provide strong evidence for the location of magnetic "barriers'' in space beyond 1 AU and their role in determining the decay phase of solar energetic electron events and the establishment and maintenance of particle reservoirs in the heliosphere.