An empirical approach to interpret the time evolution of the high spatial resolution Ca Ii K line is presented. We specify the physical parameters, such as electron temperature, hydrogen density, and velocity (microturbulent and systematic) as functions of height. The electron density is obtained from scaled non-LTE solutions for hydrogen ionization. The population indices, and thus the Ca n source functions, for a 5-level Ca II atom are computed by using the generalized NewtonRaphson method. K line profiles are then synthesized for different evolutionary stages and are compared with the observed ones. The explanation of the 'peculiar' type profile is also attempted.
Feature-to-feature identification is made on simultaneous Ca It K-line spectrograms (SG) and K2v spectroheliograms (SHG). The line profiles in plages and in the network boundary nearly always have double-peaked reversal in the core, while those inside the cells present all possibilities: double-peaked, single-peaked on violet side, single-peaked on red side, and unreversed absorption. Statistics of the profiles in the quiet chromosphere show that 50 % are Kz32 double-peaked, 20 % are K2v single-peaked, 10 % are K2r single-peaked, and 20 % show oniy incipient reversal or even totally lack any reversal. We call attention to the nontrivial contribution of these absorption profiles which are formed in 'dark regions' shown on SHG's.The physical conditions inferred from different kinds of profiles are briefly discussed.
Radiospectroheliograms obtained at millimeter wavelengths were used to determine the rotation of the solar atmosphere. Regions observed in both emission as well as absorption (associated with Ha dark filaments) were followed across the disk. The average sidereal rotation rate deduced from emissive regions is given by w (deg day -1) = 14.152(• sin E B, where B is the heliographic latitude and the quoted errors are the standard deviations of a least squares fit to the data. The rate deduced from absorption regions is given by to = 14.729(•177 sin E B. This rate is larger than that of emissive regions at all latitudes and shows smaller differential rotation. This apparent difference in the rotation rates is probably due to the difference in the height of formation of the emissive and absorption regions. This difference could be used to estimate the difference in height between an emissive region and an absorption feature in millimeter radiation.
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