# Diagnostic potential of the Ca II 8542A line for solar filaments

## TL;DR

This study demonstrates that the Ca II 8542A line can effectively diagnose the magnetic and dynamic properties of solar filaments, providing insights into temperature, velocity, and magnetic fields through high-resolution spectropolarimetric observations.

## Contribution

It introduces the use of the Ca II 8542A line for detailed magnetic and dynamic diagnostics of solar filaments, validated with high-resolution observations and inversion techniques.

## Key findings

- Ca II 8542A line encodes temperature, velocity, and magnetic field information.
- Magnetic field strength upper limit estimated at 260G.
- Degeneracy in parameters like height, temperature, and density outside hydrostatic equilibrium.

## Abstract

In this study we explore the diagnostic potential of the chromospheric Ca II line at 8542A for studying the magnetic and dynamic properties of solar filaments. We have acquired high spatial resolution spectropolarimetric observations in the Ca II 8542A line using the CRISP instrument at the Swedish 1-m Solar Telescope. We use the NICOLE inversion code to infer physical properties from observations of a solar filament. We discuss the validity of the results due to the assumption of hydrostatic equilibrium. We have used observations from other telescopes such as CHROTEL and SDO, in order to study large scale dynamics and the long term evolution of the filament. We show that the Ca II 8542A line encodes information of the temperature, line-of-sight velocity and magnetic field vector from the region where the filament is located. The current noise level only allow us to estimate an upper limit of 260G for the total magnetic field of the filament. Our study also reveals that if we only consider information from the aforementioned spectral line, the geometric height, the temperature and the density can be degenerated parameters outside the hydrostatic equilibrium approach.