The polarization of the Mg II k line at 279.5 nm encodes valuable information on the magnetic field of the upper solar chromosphere, where this strong resonance line originates. We have developed a novel radiative transfer code which allows us to account for scattering polarization and the Hanle and Zeeman effects, as well as partial frequency redistribution (PRD) phenomena (i.e., correlation effects between the incoming and outgoing photons in the scattering events). This non-LTE code, which treats the atomic system and the polarized radiation field quantum-mechanically, has been applied to calculate the Stokes profiles that emerge from given models of the solar chromosphere considering various magnetic field configurations. The Hanle effect is the magnetic-field-induced modification of the linear polarization produced by scattering processes in a spectral line. Before this investigation, it was thought that the wings of the linear polarization profiles are insensitive to the presence of a magnetic field, and that the magnetic sensitivity of strong chromospheric lines, like the Mg II k line, is restricted to the circular polarization induced by the Zeeman effect and, via the Hanle effect, to the core of the linear polarization profiles. We have discovered that in strong resonance lines for which PRD effects are significant, like Mg II k, the magneto-optical terms of the Stokes-vector transfer equation introduce a very significant magnetic sensitivity in the wings of the linear polarization profiles. This hitherto unnoticed sensitivity to both weak (around 5 G) and stronger magnetic fields expands the scientific interest of the Mg II k line polarization as a diagnostic tool for probing the magnetism of the enigmatic solar chromosphere, both in quiet and active regions of the Sun. The second flight of the Chromospheric LAyer Spectro-Polarimeter (CLASP) will be dedicated to observe the wavelength variation of the Stokes profiles across the Mg II h & k lines. The first flight of the CLASP sounding rocket experiment, proposed by NASA, JAXA and the IAC, took place on September 3, 2015. This very successful international project provided the first measurement of the polarization in an ultraviolet line of the solar disk radiation (hydrogen Lyman-alpha at 121.6 nm), and the first empirical exploration of the geometrical complexity and magnetic field of the chromosphere-corona transition region of the Sun.
Advertised on
References
It may interest you
-
Dark matter is an invisible substance that makes up more than eighty percent of the matter content of the universe. We know of its existence due to its gravitational influence, being a key ingredient to understand everything from the large-scale evolution of the universe to the formation of galaxies like the Milky Way, of which we are part of . However, very little is known about its nature, which constitutes one of the greatest unsolved problems in contemporary physics. The fuzzy dark matter model has recently been studied as a promising candidate. In this model , it is postulated that darkAdvertised on
-
The amount and complexity of data delivered by modern galaxy surveys has been steadily increasing over the past years. New facilities will soon provide imaging and spectra of hundreds of millions of galaxies. Extracting coherent scientific information from these large and multi-modal data sets remains an open issue for the community and data-driven approaches such as deep learning have rapidly emerged as a potentially powerful solution to some long lasting challenges. This enthusiasm is reflected in an unprecedented exponential growth of publications using neural networks, which have goneAdvertised on
-
The cosmic evolution of the barred galaxy population provides key information about the secular evolution of galaxies and the settling of rotationally dominated discs. We study the bar fraction in the SMACSJ0723.37323 (SMACS0723) cluster of galaxies at z = 0.39 using the Early Release Observations obtained with the NIRCam instrument mounted on the JWST telescope. We visually inspected all cluster member galaxies using the images from the NIRCam F200W filter. We classified the galaxies into ellipticals and discs and determine the presence of a bar. The cluster member selection was based on aAdvertised on