Masters Thesis

Chromospheric properties of the Sun as a star

The chromospheric activity of the Sun is governed by the surface magnetic field often measured at the photosphere. We study the dependence of chromospheric activity on magnetic field of the Sun as a star by using observations by Integrated Sunlight Spectrometer (ISS) and Vector Spectromagnetograph (VSM) of Synoptic Optical Long-term Investigations of the Sun (SOLIS) instrument. The chromospheric activity is measured as the equivalent width (EW) of spectral lines in H-$\alpha$, He I 10830 nm, Ca II 854.2 nm, Ca II H and K, and Na D I 589.6 nm obtained with the ISS. The full disk mean total magnetic flux (FDMTMF) observed with the VSM is used as the measure of magnetic activity of the Sun. The equivalent width of Ca II K and He I 10830 nm measured by Livingston along with the Magnetic Plage Strength Index (MPSI) value and a Mount Wilson Sunspot Index (MWSI) obtained with 150-Foot SOlar Tower in Mt. Wilson Observatory are used to further study the relationship between the magnetic field and chromospheric activity.

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