Measuring Magnetic Fields in the Solar Atmosphere

TL;DR

This paper reviews the history, current methods, and challenges of measuring magnetic fields in the solar atmosphere, emphasizing the importance of these measurements for understanding solar and heliospheric processes.

Contribution

It provides a comprehensive overview of solar magnetic field measurement techniques, discusses existing challenges, and offers insights into future directions in solar magnetometry.

Findings

Photospheric magnetometry is well-established.

Diagnosing magnetic fields in the chromosphere and corona remains challenging.

Limited measurements have been made in the outer solar atmosphere.

Abstract

Since the discovery by Hale in the early 1900s that sunspots harbor strong magnetic field, magnetism has become increasingly important in our understanding of processes on the Sun and in the Heliosphere. Many current and planned instruments are capable of diagnosing magnetic field in the solar atmosphere. Photospheric magnetometry is now well-established. However, many challenges remain. For instance, the diagnosis of magnetic field in the chromosphere and corona is difficult, and interpretation of measurements is harder still. As a result only very few measurements have been made so far, yet it is clear that if we are to understand the outer solar atmosphere we must study the magnetic field. I will review the history of solar magnetic field measurements, describe and discuss the three types of magnetometry, and close with an outlook on the future.