Suprathermal electrons of solar and local origins and typical pitch-angle distribution patterns associated with ICMEs 

Olga Khabarova - Institute of terrestrial magnetism (IZMIRAN); Valentina Zharkova - Northumbria University, Newcastle, United Kingdom; Qian Xia - Northumbria University, Newcastle, United Kingdom; Olga Malandraki - IAASARS, National Observatory of Athens, Penteli, Greece 

Session: Interplanetary CMEs and Solar Particle Events

Abstract

It has been thought for a long time that suprathermal electrons with energies of ∼70 eV and above consisting of dispersionless halo electrons and magnetic field-aligned beams of strahls originate only from the solar corona. Scattering was considered as the only active process impacting their properties in the solar wind. Consequently, the interpretation of patterns of pitch-angle distributions (PADs) of suprathermal electrons was impacted by the solar source paradigm. Recent observational studies supported by numerical simulations have shown that there is an unaccounted population of electrons accelerated to suprathermal energies at reconnecting current sheets and 3D dynamical plasmoids/blobs (or 2D magnetic islands) directly in the heliosphere. We discuss observations of counterstreaming strahls and heat flux dropouts in PADs, comparing observed PAD features with those predicted by PIC simulations and showing typical PAD patterns determined by local acceleration of thermal-core electrons. We show that in some energy channels, solar wind borne suprathermal electrons coexist with those of solar origin, therefore complex and puzzling heat flux dropout and bidirectional strahl events associated with ICMEs can be easily explained by a combination of local particle acceleration with the impact of corona borne suprathermal electrons.