Borysenko S. Fast variations in spectrum of comet Halley

The goal of this work is to research fast variations of the spectral lines intensities in spectra of comet Halley and to analyse these phenomena. The present investigation has been made on the basis of more then 500 high-resolution spectrogram obtained by H.K.Nazarchuk (with participation of L.M.Shulman and SAO astronomers) in November-December of 1985 at the 6-m telescope (SAO, Russia). The TV-scanner, which is mounted at the Nasmyth's focus of the 6-meter telescope, was used as the spectral device. Originally the spectrograph has a long (> 40 arcsec) slit. The slit was covered by a special mask, which cut from the slit two rectangular diaphragms. The height of each was equal to 4 arcsec. So, there were two space channels separated by 40 arcsec. There were 1024 spectral channels in each of the space one. The total extension of a spectrum on the inlet window was about 900 - 980 A, so the width of a spectral channel was about 0.9 A and, therefore, four expositions were necessary to cover the whole spectral region restricted by the spectral sensitivity of the input photocathode: 3320 - 6600 A. Some fast variations with different quasiperiods were detected in all the spectrograms. Quasiperiods of these variations were from 15 - 40 min to 1.5 - 2 hours. Only the most important lines so as C2, C3, CN, CH and NH2 were analyzed. False periods were checked by comparison of the power spectra of the variations with the computed spectral window of the data. Only false periods about 400 sec (the average exposition) were detected. An algorithm for analysis of locally Poisson's time series with gaps was proposed and used. Average cross-correlation coefficients are calculated. Two types of fast variations are detected: 1) high amplitude variations with more long quasiperiods (1.5 - 2 hours) and the coefficient of crosscorrelations between line intensities about 0.9 - 0.95; 2) low amplitude variations with short periods (15 - 40 min), which look like white noise and have the coefficient of crosscorrelations about 0.1 - 0.3. This difference may be caused by the nature of the variations. The first type variations may be an effect of both active processes in cometary nucleus and the solar proton streams. Analysis of solar proton flux variation with energies >1 MeV in November - December 1985 (by spacecraft IMP 8 results) confirms the above-mentioned version. For determination of general parameters of cometary atmosphere, such as the production rates of radicals C2, C3, CN, CH, and NH2 it was necessary to estimate the contribution of dust luminescence into the continuum of the comet. We supposed, that this part of a cometary continuum is luminocity of cometary CHON particles exited by solar ultraviolet radiation. Space and wavelength distribution of the luminescent continuum was calculated. A simple model of a comet atmosphere (the Haser's model) was taken to make synthetic photometrical data and to calibrate the spectra by comparison the synthetic photometry with the data of the absolute photometry from the IHW archive. This waythe gas production rates and numbers of basic molecules in the cometary atmosphere were obtained.