Existence of Nanoparticle Dust Grains in the Inner Solar Corona?

Abstract

Motivated by the recent paper by Habbal et al., we have made spectroscopic observations in the wavelength range of 1072.8-1079.0 nm of the solar corona above the coronal hole region on several days using a coronagraph. We made raster scans above the coronal hole region as well as other coronal regions for comparison. The exposure time of 200 s at a single location permitted us to detect signals of the order of 10/sup7 of the solar disk brightness. We did not find any indication of emission around 1074.7 nm due to fluorescence from silicon nanoparticle dust grains in the coronal hole region in the inner corona proposed by Habbal et al. This may be due to the absence of silicon nanoparticle dust grains in the coronal hole region or to our detection limit.