K emission-line widths and the solar chromosphere

Abstract

Closely spaced microphotometer tracings parallel to the dispersion of one excellent frame of a K-line time sequence have been utilized for a study of the nature of the K2v, K2R intensities in the case of the solar chromosphere. The frequency of occurrence of the categories of intensity ratio 1K~v/I~R are as follows: 1~2v > IJ~R = 45.3 per cent; l~v = I~R = 4.7 per cent; Ix~v < 1K~R --25 per cent; IK~R=0=22.3 per cent; I~v=0--0.7 per cent. Two types of absorbing components are postulated to explain the pattern of observed K2v, K2R intensity ratios. One component with minor Doppler displacements acting on the normal Kz32 profile, where Ksv > KsR, produces the cases Ksv>> KsR, Ksv = K2R, K2v < KsR. The other component arises from 'dark condensations' which are of size 3500 kms as seen in Ksn. They have principally large down flowing velocities in the range 5-8 km/sec and are seen on Kz spectroheliograms with sizes of about 5000 kms, within the coarse network of emission. These 'dark condensations' give rise to the situation Ksn = 0.Ks-line widths are measured for all tracings where K2v, K2R are measurable simultaneously. The distribution curve of these widths is extremely sharp. The K2 emission source is identified with the bright fine mottles visible on the surface. Evidence for this interpretation comes from the study of auto-correlation functions of K2 intensity variations and the spacing between the bright fine mottles from both spectrograms and speetroheliograms. The life time of the fine mottling is 200 sec.The supergranular boundaries which constitute the coarse network come in two intensity classes. A low intensity network has the fine mottles as its principal contributor to the K emission. When the network is bright, the enhancement is caused by increased K emission due to the accumulation of magnetic fields at the supergranule boundary. The Ks widths of the low intensity supergranular boundary agree with the value found for the bright mottles. Those for the brighter network are lower than this value, similar to the Kz widths as seen in the active regions.It is concluded that bright fine mottling is responsible for the relation, found by Wilson and Bappu, between K emission line widths and absolute magnitudes of the stars.The paper discusses the solar cycle equivalents that stellar chromospheres can demonstrate and indicates a possible line of approach for successful detection of cyclic activity in stellar chromospheres.The last decade has witnessed much interest in the chromospheres of stars, especially on problems regarding the physical parameters that characterize them. There is also the added charm of speculating on the detection of cyclic effects in stellar chromospheres, similar to that which we are aware of in the solar case. The discovery that the widths of the K emission reversals are related to the absolute magnitudes of the stars (Wilson and Bappu, 1957;Bappu, 1954;Wilson, 1954) and that the intensities have an age dependence (Wilson, 1963), together with the high resolution spectroscopic efforts...

Ca II K line profile of the truly quiet Sun

“…The latter agrees perfectly with the value of the width derived by Bappu and Sivaraman (1977) 9 The e -1 width is the width which one would measure if a micrometer were used for the measurement as was done for the stars by Wilson and Bappu (1957). The width for the plage is different, and the plages themselves exhibit a variety of widths (Smith, 1960;Bappu and Sivaraman, 1971; Shine and Linsky, 1972). As a consequence of this, the widths also exhibit variability over the cycle (White and Livingston, 1981;Sivaraman et al, 1987).…”

Absolute spectrophotometry of Comet kohoutek 1973f during post-perihelion passage

“…This agrees very well with the earlier studies on the D-line emission in comets (c.f. Bappu and Sivaraman, 1969).…”

Temporal Variation of Ca–K Line Profile of the Sun during the Solar Cycle 22 and 23

“…The spatially resolved spectra indicate that regions of plages and networks show larger K 1 widths and smaller K 2 widths as compared to quiescent regions (White & Livingston 1981;Bappu & Sivaraman 1971), depending upon the intensity of the features. Also, the emission at the K 2V and K 2R wavelength regions increases with the intensity of the features.…”