Bonn 2020 – scientific programme

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EP: Fachverband Extraterrestrische Physik

EP 4: Sun and Heliosphere II

EP 4.3: Talk

Wednesday, April 1, 2020, 11:15–11:30, H-HS VIII

Estimating uncertainties for Solar Energetic Particle anisotropies — •Maximilian Brüdern, Nina Dresing, Bernd Heber, Lars Berger, Alexander Kollhoff, and Patrick Kühl — IEAP Christian Albrechts Universität zu Kiel

Solar Energetic Particles (SEPs) can routinely be observed at 1 AU depending on their origin at the Sun and their transport through the interplanetary medium. Their energy is mostly determined close to the Sun. As SEPs propagate outward along the Interplanetary Magnetic Field (IMF) the pitch-angle with respect to the local field is systematically focused due to the radial decreasing IMF. While stochastic changes are induced by scattering at fluctuations of the IMF. Often the first order anisotropy of SEPs is calculated to disentangle imprints of source and transport. Strong anisotropies indicate periods of weak pitch-angle scattering. Although many modeling and observational studies are based on the anisotropy, its uncertainty is often neglected which could result in inaccurate conclusions. Therefore, we propose a new method based on a bootstrap approach where we consider (1) directional instrument responses, (2) the variation of the magnetic field, and (3) the stochastic nature of detection. Here, we present our procedure and final results for different SEP events using measured data of the IMF and particle fluxes by the Solar Electron and Proton Telescope (SEPT) on board of each STEREO spacecraft. The SEPT provides four viewing directions with a view cone of 0.66 sr each on a three axis stabilized spacecraft. In future we plan to apply our method to the Electron and Proton Telescope (EPT) on board Solar Orbiter.