The J- and K-Band Brightness of the Solar F Corona Observed during the Solar Eclipse on 1998 February 26

We analyze J- and K-band observations of the 1998 solar eclipse and derive the F-corona brightness in the K band between 3 and 7 R_☉ from the center of the Sun and in the J band out to 5 R_☉. The falloff in the K-band brightness from 3 to 7 R_☉ is fitted with a radial power law with exponent -2.4 ± 0.1 at the solar equator and with exponent -2.9 at the solar pole. This slope is gentler than that derived from observations in 1983 but is steeper than that derived from observations for the 1991 eclipse. The radial profiles agree well with models that explain the F corona with weakly absorbing dust particles. Comparison of the J- and K-band brightness at 3 R_☉ from the center of the Sun indicates a reddening of the F corona with respect to the solar spectrum. The reddening is, however, less pronounced compared to the F corona observed during the 1983 total solar eclipse. This fact may be attributed to a change in the composition of dust near the Sun. As with the radial profiles, the reddening in 1998 is better explained with models that assume weakly absorbing rather than strongly absorbing dust particles in the solar corona. Similar to recent eclipse observations, we do not detect an excess emission feature of near-solar dust in the F corona. We hence can reject the hypothesis that suggests a correlation between the detection of an emission feature and the solar activity cycle.