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We study the radiative emission of various types of solar features, such asquiet Sun, enhanced network, plage, and bright plage regions, identified onfiltergrams taken in the Ca II K line. We analysed fulldisk images obtainedwith the PSPT, by using three interference filters that sample the Ca II K linewith different bandpasses. We studied the dependence of the radiative emissionof disk features on the filter bandpass. We also performed a NLTE spectralsynthesis of the Ca II K line integrated over the bandpass of PSPT filters. Thesynthesis was carried out by utilizing both the PRD and CRD with the mostrecent set of semi empirical atmosphere models in the literature and someearlier atmosphere models. We measured the CLV of intensity values for varioussolar features identified on PSPT images and compared the results obtained withthose derived from the synthesis. We find that CRD calculations derived usingthe most recent quiet Sun model, on average, reproduce the measured values ofthe quiet Sun regions slightly more accurately than PRD computations with thesame model. This may reflect that the utilized atmospheric model was computedassuming CRD. Calculations with PRD on earlier quiet Sun model atmospheresreproduce measured quantities with a similar accuracy as to that achieved hereby applying CRD to the recent model. We also find that the median contrastvalues measured for most of the identified bright features, disk positions, andfilter widths are, on average, a factor 1.9 lower than those derived from PRDsimulations performed using the recent bright feature models. The discrepancybetween measured and modeled values decreases by 12% after taking into accountstraylight effects on PSPT images. PRD computations on either the most recentor the earlier atmosphere models of bright features reproduce measurements fromplage and bright plage regions with a similar accuracy.

Radiative emission of solar features in the Ca II K line: comparison of measurements and models