Research Goals

  1. To diagnose the magnetism of the solar chromosphere below the chromosphere-corona transition region, as well as to determine the strength and geometry of the magnetic fields that confine and/or channel the plasma of a variety of chromospheric and coronal structures (e.g., spicules, prominences, eruptive filaments), we exploit the polarization produced by the joint action of the Hanle and Zeeman effects in several permitted spectral lines, like H-alpha, the Ca II H & K resonance lines, the IR triplet of Ca II, and the He I 10830 Å and 5876 Å multiplets.
  2. To decipher the physics of the upper chromosphere and transition region, where the average ratio of gas to magnetic pressure is smaller than unity, we develop novel techniques to diagnose the polarization of the solar-disk radiation in permitted FUV and EUV resonance lines, such as the Lyman-alpha lines of H I and He II, the C IV line at 1548 Å, the Si III line at 1206 Å and the Mg II h & k doublet.
  3. To explore the magnetism of the corona (i.e., the region of the Sun where the near-Earth space weather is generated through the quick release of magnetic free energy) we investigate the polarization of forbidden and permitted coronal lines, developing for the first time novel techniques to complement them.

Methodology and working plan

The POLMAG research group is formed by the PI, together with the scientists and students mentioned above. The team is being created so as to facilitate synergies between theory, supercomputations, development of plasma diagnostic techniques and spectropolarimetric observations. The main work packages (WP) of research are the following:

  • WP-1: Identify the most suitable ultraviolet (UV) spectral lines applying the quantum theory of spectral line polarization, assuming complete frequency redistribution (CRD) in the scattering events.
  • WP-2: For each of the UV lines selected in WP-1, refine the predictions by taking into account the effects of partial frequency redistribution (PRD) with J-state interference and considering the general Hanle-Zeeman regime.
  • WP-3: Develop and apply new coronal magnetometry methods by combining the information encoded in the polarization of forbidden (visible/IR) and permitted (FUV/EUV) spectral lines.
  • WP-4: Extend the radiative transfer code PORTA of Stepan & Trujillo Bueno (2013) to PRD in the general Hanle-Zeeman regime. Moreover, perform 3D radiative transfer modeling of the Stokes profiles of chromospheric and transition region lines using increasingly realistic numerical models of the solar atmosphere, both in CRD and PRD. Confrontation with the spectropolarimetric observations resulting from the CLASP 1 & 2 sounding rocket experiments (Lyman-alpha, Si III 120.6 nm, Mg II h & k) and from observations with ground-based telescopes (e.g., GREGOR, SST, DKIST).
  • WP-5: Obtain novel spectropolarimetric observations with GREGOR (e.g., the He I 10830 and D3 multiplets) and with the SST (e.g., the IR triplet of Ca II), and pursue the development and application of the new generation of Stokes inversion techniques.
  • WP-6: Development of the “Polarized Radiation Diagnostics Website”. This will provide the astrophysical community with a user-friendly environment where any scientist interested in doing top-level science with the spectropolarimetric data provided by facilities like CLASP, GREGOR, DKIST, SUNRISE-III and EST will find suitable tools for her/his research.