A Statistical Study Of The Reservoir Phenomenon Of Solar Energetic Electrons

In the gradual solar energetic particle(SEP)events,a so called reservoir phenomenon is usually observed by multi-spacecraft located at different latitudes,longitudes,and distances in the interplanetary space.In the SEP event with reservoir,large differences in particle fluxes are observed by different spacecraft during the ascending phase,while the fluxes are almost equal and evolve similarly over time during the decay phase.In this dissertation,the data in the 23 rd solar cycle from Ulysses and ACE spacecraft is used to investigate the solar energetic electrons,magnetic field,plasma temperature,and plasma bulk velocity and density during the reservoir phenomen a.The SEP fluxes are fitted with the adiabatic cooling and diffusion models to find out which mechanism plays a dominant role in a reservoir phenomenon.Furthermore,using the data from STEREO A-B during the solar cycle 24,the fluxes and anisotropies are analyzed in the reservoir events.The ratios of SEP fluxes in different pitch angles are used to study the anisotropy in SEP events.The anisotropy can be used to deduce the magnetic connection between the source and spacecraft,it is able to infer the transport process of SEPs during the reservoir phenom enon.Based on the observations,we suggest that perpendicular diffusion is a general mechanism to explain the reservoir phenomenon,and the injection process of energetic electron source also plays an important role in the formation of the reservoir.In addition,during the decay phase of particle flux,the perpendicular diffusion could reduce the spatial gradient of fluxes at different locations,so it can further help to form the reservoir phenomenon.In some intensive gradual energetic electron events,the duration of fluxes are very long,therefore,the effects of perpendicular diffusion become more apparent.Although the effects of interplanetary magnetic mirror are conducive to the formation of reservoir phenomenon in some events,it is not a general mechanism.If energetic electrons could diffuse perpendicularly near the source,STEREO A and STEREO B could simultaneously observe intensive anisotropy in pitch angle,so reservoir phenomenon could happen only with parallel diffusion.If energetic electrons could diffuse perpendicularly in the interplanetary space but not near the source at most,one spacecraft could observe intensive anisotropy in pitch angle,so the effective perpendicular diffusion of energetic electrons is necessary for explaining the reservoir phenomenon.