Further studies, including analyses of the directional fluxes and transport simulations that take the individual instrument responses into account, would allow a better interpretation of the radial evolution of SEE events.
The absence of a clear radial dependence on the first-order anisotropy and the rise time as well as the ambiguous onset timing of the SEE events found in this study could be the result of general limitations in the methods we used. The rudimentary methods presented in this study lead to event parameters with large uncertainties. The derived onset delays observed between two spacecraft were found to be too long to be explained by ideal Parker spirals in multiple events.Ĭonclusions.
For the first-order anisotropy and the rise time no clear radial dependence was found.
For the majority of events, the peak flux decreases with increasing radial distance. In our sample of SEE events, we find strong event-to-event variations in the radial dependence of all derived parameters. We compared the event parameters observed at different spacecraft and derived exponential indices α p for each parameter p, assuming an R α-dependence on the heliocentric distance R. For all the SEE events that satisfied our selection criteria, we determined the onset times, rise times, peak fluxes, and peak values of the first-order anisotropy for electrons in the energy range from ∼50 − 85 keV. For the approximation of the footpoint separation, we followed a ballistic back-mapping approach using in situ solar wind speed measurements. We identified SEE events for which Solar Orbiter and either Wind or STEREO-A had a small longitudinal separation (< 15°) between their nominal magnetic footpoints. We study the radial evolution of near-relativistic solar energetic electron (SEE) events observed by at least two spacecraft at different heliocentric distances and with small separation angles between their magnetic footpoints at the Sun. Universidad de Alcalá, Space Research Group (SRG-UAH), Plaza de San Diego s/n, 28801 Alcalá de Henares, Madrid, SpainĪims. Institute of Experimental and Applied Physics, Kiel University, Christian-Albrechts-Platz 4, 24118 Kiel, GermanyĮ-mail: of Physics and Astronomy, 20014 University of Turku, Finland
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