The polarization profiles of Ca II 854.2 nm in a Quiet Sun simulation
Rebeca Centeno, High Altitude Observatory (NCAR), USA
Ca II 854.2 nm has been deemed one of the most promising spectral line diagnostics for the chromospheric magnetic field, due to its accessibility from ground-based observations and the relative ease of its interpretation. The standard tools used for the interpretation of this spectral line do not account for the physics of scattering polarization nor its modification due to the Hanle effect. However, scattering polarization signatures typically dominate the linear polarization profiles of Ca.
II 854.2 nm in weak field areas (Manso Sainz & Trujillo Bueno 2010, 2003), particularly close to the limb. When combined with the enhancing effect of shocks, these linear polarization signals can reach amplitudes of up to 1% of the continuum intensity (Carlin et al 2012), which would drown Zeeman-polarization signatures induced by magnetic fields in the low hecto-gauss range.
In this work Rebecca Centeno evaluates the temporal evolution of the polarization profiles of Ca II 854.2 nm that emerge from a Quiet Sun simulation from MuRAM. The effects of the magnetic field and the line-of-sight velocity are analyzed separately in order to quantify their individual contributions to the linear polarization.
Waves captured by spectropolarimetric IBIS obversations
Dr Marco Stangalini, ASI, Italian Space Agency, Italy
Spectropolarimetry has become a mature tool for the analysis of the dynamics of the lower solar atmosphere. Next generation solar instrumentation, characterized by unmatched polarimetric accuracy and sensitivity, will dramatically improve our observational capabilities, extending the use of spectropolarimetric diagnostics down to very small spatial scales (< 100 km) and higher atmospheric heights.
In this contribution Dr Stangalini will show how simultaneous spectropolarimetric observations at multiple heights is a powerful tool to reveal the details about the plasma and magnetic field wave dynamics in the solar atmosphere, and for the identification of Alfvénic disturbances.
More in detail, he will show the capabilities of tomographic spectropolarimetric imaging in the investigation of MHD waves, by presenting recent results from high resolution state-of-the-art observations of the solar atmosphere and, in particular, from IBIS.
Two-fluid shocks in an isothermal stratified atmosphere
Dr Ben Snow, University of Exeter, Uk
A compressional wave propagating upwards in the solar atmosphere naturally steepens due to the stratification of the atmosphere and can readily develop nonlinearities and shock. If the magnetic field is inclined, a shock can separate into fast- and slow- mode components as it passes through the point where the sound and Alfven speed are equal. This point can occur in the lower solar atmosphere, where the plasma is partially-ionised and two-fluid effects become important. In this talk, Dr Snow will present results from two-fluid numerical simulations demonstrating the mode conversion and interplay between the ionised and neutral species for a shock wave propagating through an isothermal stratified atmosphere.
Waves in the lower solar atmosphere: setting the scene for the next generation of solar telescopes
Dr David Jess, Queen's University Belfast, UK
The development of cutting-edge three-dimensional simulations has highlighted a vast assortment of predicted solar phenomena that reside below the spatial, temporal, and spectral resolutions of current telescope facilities. Thankfully, next-generation solar telescopes (including DKIST, SUNRISE, NLST, EST, and Solar-C) will improve the spatial resolutions achievable. However, it is the role of the instruments commissioned on these revolutionary facilities that will pave the way for robust comparisons to be made to the cutting-edge numerical simulations pioneered by the likes of Mancha, Bifrost, MuRAM, and LareXd. Here, Dr Jess will present overarching requirements of such new-age instrumentation, including a description of a hyper-spectropolarimetric imager currently under construction for the Indian National Large Solar Telescope. Lastly, Dr Jess will highlight the scientific challenges discussed during the Royal Society’s High Resolution Wave Dynamics in the Lower Solar Atmosphere Theo Murphy meeting, and suggest ways how combined novel instrumentation, alongside collaborative efforts within the solar physics community, will provide rapid developments in the understanding of wave phenomena in the lower solar atmosphere.
Meeting overview and future directions (discussion)