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H. Kimura (MPAE), I. Mann (MPAE, CalTech), B. Goldstein (JPL), C. Korendyke, R. Howard (NRL)
The solar F-corona emission is comprised of solar radiation scattered by dust particles and thermal radiation emitted from near-solar dust particles. The visible brightness is mainly produced by scattering at medium scattering angles from particles near the Sun and by enhanced forward scattering from particles near the observer. The infrared brightness originates from the thermal emission from hot particles near the Sun. Studies of the F-corona are usually limited by the influence of atmospheric stray light and by difficulties of the separation of the K-corona, produced by sunlight scattered at electrons. The K-corona decreases steeply with increasing elongation and has a smaller contribution to the outer coronal brightness. This outer corona is observed from the SOHO satellite where the lack of atmospheric stray light and an optimized suppression of instrumental stray light in the LASCO coronagraph allow for the detection of the coronal brightness as far out as about 30 solar radii from the center of the Sun. These observations yield the opportunity to study the properties of interplanetary dust in the inner solar system. We will present preliminary results from the analysis of the data from the LASCO C3 coronagraph at distances from 10 to 30 solar radii from the center of the Sun in 3 wavelength intervals between 0.4 and 1.1 micron. We compare the data to brightness calculations in order to discuss the distribution of dust grains in the inner solar system.
The Solar Heliospheric Observatory, SOHO, is a joint scientific space mission developed by ESA and NASA. The Large Angle Spectrometric Coronagraph (LASCO) was developed and is operated jointly by the Naval Research Laboratory (USA), the Max-Planck-Institut für Aeronomie (Germany), the Laboratoire d'Astronomie Spatiale (France) and the University of Birmingham (UK).