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EP: Fachverband Extraterrestrische Physik

EP 9: Sun III and Heliophysics I

EP 9.6: Talk

Wednesday, April 1, 2009, 14:45–15:00, Zahnklinik

Compton-Getting Correction for STEREO/SEPT — •Jan Gieseler, Raúl Gómez-Herrero, Andreas Klassen, Reinhold Müller-Mellin, Bernd Heber, and Stephan Böttcher — Christian-Albrechts-Universität Kiel

The Solar Electron and Proton Telescope (SEPT) aboard each of the two STEREO spacecraft consists of two dual double-ended magnetic/foil particle telescopes which separate and measure electrons (from 30 to 400 keV) and ions, mainly protons and α-particles (from 70 keV to 6.5 MeV). One telescope is looking in the ecliptic plane (SEPT-E), the other perpendicular to this plane (SEPT-NS). Thus there are four looking directions for each spacecraft: one pointing to the Sun along the nominal Parker spiral (45^∘ west from the S/C-Sun line), one pointing to the opposite direction, away from the Sun along the Parker spiral, and two apertures looking North and South perpendicular to the ecliptic. Since the velocity of several tens of keV ions is only by a factor of about 10 higher than the solar wind speed, it is expected that an isotropic pitch angle distribution in the solar wind frame becomes anisotropic in the spacecraft frame. We developed a method to correct the SEPT ion data for this so-called Compton-Getting effect. Telescopes such as SEPT that measure the total energy of the ion, but not its nuclear charge, cannot distinguish between protons and α-particles. Therefore our method is also designed to account for He contribution. Finally, we will show that with our method the measurements of SEPT can be transformed successfully to the solar wind frame, and apply it to selected particle events.