Energetic Particles in the Heliosphere: from the Sun to Planetary Atmospheres
Pitch Angle Scattering of Solar Flare Electrons in the Interplanetary Medium: Observations and Modelling
Benjamin Alcock
Dr. Eduard Kontar (University of Glasgow), Dr Neus Agueda (Universitat de Barcelona)
University of Glasgow
Recent studies have found that the arrival of solar flare electrons at Earth is often delayed with respect to Hard X-ray and radio emission. Whilst several theories have attempted to explain these observations, the origin of this delay is still under debate. We analyse several near-relativistic (~27 keV - 300 keV) electron events observed via both RHESSI Hard X-ray observations at the Sun and in-situ measurements from the Wind/3DP detector at 1 AU. Numerical simulations of electron transport outwards from the Sun are made which take an injection time and initial energy spectrum from RHESSI data, and the flux subsequently passing 1 AU is calculated. We consider the effects of adiabatic focusing and pitch angle diffusion on the particle transport, and an energy and distance dependent form of the parallel mean free path for electrons is employed. The simulated lightcurves, peak flux spectrum, pitch angle distribution and delay times are then compared with Wind observations. We find that, for higher energy electrons (>40 keV), the simulated events match well with observations, showing that pitch angle scattering is able to explain apparent delayed particle injection at the Sun. The lower energy observations, however, remain unmatched by models, which predict much more impulsive events at Earth than are observed.
13:30 - 15:00