SOLARNET Conference: The Many Scales of the Magnetic Sun

The Solar Mean Magnetic Field (SMMF) is the average value of the line-of-sight (LOS) magnetic field considered over the visible hemisphere of the Sun. Various synoptic observations of the solar magnetic field have shown that the SMMF has a periodicity of ~ 27 days, and an amplitude that varies according to the solar cycle, from ±0.2 G during solar minima to ±2 G during solar maxima. It has also been shown that the SMMF has a good correlation with the Interplanetary Magnetic Field (IMF). Nevertheless, the origin of the SMMF is still a controversial subject. Till date, SMMF measurements have always been carried out using photospheric spectral lines only. In this regard, we utilised full-disk LOS magnetograms from the Vector Spectromagnetograph (VSM) (one of the instruments in SOLIS - Synoptic Optical Long-term Investigations of the Sun), calculated the SMMF as the disk-averaged magnetic field in each magnetogram, and compared the SMMF at photospheric and chromospheric heights. Our comparison showed that the SMMF at the chromosphere is a factor of 0.6 times the SMMF at the photosphere, with a correlation coefficient of 0.80; indicating that a considerable fraction of the SMMF might be propagating outwards from the photosphere to the chromosphere. This brings us one step closer to understanding the connection between the SMMF and the IMF. Further, to understand the origin of the SMMF, which is a magnetic flux imbalance, we are studying the full-disk Stokes I and Stokes V data from VSM, which are disk-averaged to create Stokes profiles. Any localised source of the SMMF should reflect in the Stokes V profile as a rotationally modulated doppler shift. Our initial analyses show that there is a periodicity in the Stokes V doppler shift. This periodicity is being analysed along with associated magnetograms, to understand the source of the SMMF.