The White-Light Limb Flare of 16 August 1989 and its Chromospheric Counterpart

Abstract

After carefully comparing the white-light (5600+/-800 Angstrom) and the slit-jaw Halpha images (0.5 Angstrom passband) of the 2N/X20 white-light flare of 16 August 1989, we found that the Halpha counterpart identification of the bright kernels in continuum by Hiei, Nakagomi, and Takuma (1992) was incorrect. Now we come to the conclusion that none of the two white-light kernels has a corresponding bright Halpha area. Moreover, the loop shapes in white-light are also different from those in Halpha. Halpha loops rose more rapidly than white-light loops. However, their height-time variations on the whole are similar. This indicates that the continuum and chromospheric emissions of the flare presumably come from different plasmas, but may be modulated by some mutual factors, such as large-scale magnetic fields. Analysis of the He I 10 830 Angstrom spectra taken simultaneously with the slit-jaw Halpha images shows that the line-center intensity of He I 10 830 Angstrom doesn't have a good correlation with the intensity of nearby continuum, which supports the above conclusions. In addition, the electron density at the white-light loop top estimated from the continuum around 5600 Angstrom and 10 830 Angstrom is as high as 10(12)-10(13) cm(-3).