English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Context. The solar chromosphere and the lower transition region is believedto play a crucial role in the heating of the solar corona. Models that describethe chromosphere (and the lower transition region), accounting for its highlydynamic and structured character are, so far, found to be lacking. This ispartly due to the breakdown of complete frequency redistribution in thechromospheric layers and also because of the difficulty in obtaining completesets of observations that adequately constrain the solar atmosphere at allrelevant heights. Aims. We aim to obtain semi-empirical model atmospheres thatreproduce the features of the Mg II h&k line profiles that sample the middlechromosphere with focus on a sunspot. Methods. We use spectropolarimetricobservations of the Ca II 8542 A spectra obtained with the Swedish 1-m SolarTelescope (SST) and use NICOLE inversions to obtain semi-empirical modelatmospheres for different features in and around a sunspot. These are used tosynthesize Mg II h&k spectra using RH1.5D code, which we compare withobservations taken with the Interface Region Imaging Spectrograph (IRIS).Results. Comparison of the synthetic profiles with IRIS observations revealsthat there are several areas, especially in the penumbra of the sunspot, wheremost of the observed Mg II h&k profiles are very well reproduced. In addition,we find that supersonic hot downflows, present in our collection of models inthe umbra, lead to synthetic profiles that agree well with the IRIS Mg II h&kprofiles, with the exception of the line core. Conclusions. We put forward andmake available four semi-empirical model atmospheres. Two for the penumbra,reflecting the range of temperatures obtained for the chromosphere, one forumbral flashes, and a model representative of the quiet surroundings of asunspot. These are available in electronic as well as in table formats.

Semi-empirical model atmospheres for the chromosphere of the sunspot penumbra and umbral flashes