# Record-breaking coronal magnetic field in solar active region 12673

## TL;DR

This paper reports the first imaging microwave observations of an exceptionally strong coronal magnetic field of about 4000 G in solar active region NOAA 12673, challenging previous assumptions about coronal magnetic field strengths.

## Contribution

It introduces a novel observational and modeling approach to measure and validate the record-breaking coronal magnetic field in a solar active region.

## Key findings

- Coronal magnetic field of about 4000 G was observed at the base of the corona.
- The study combined microwave imaging and magnetic field measurements to model the coronal magnetic field.
- The record-breaking magnetic field was quantified at various coronal heights.

## Abstract

At the Sun, the strongest magnetic fields are routinely detected at dark sunspots. The magnitude of the field is typically about 3000 G, with only a few exceptions that reported the magnetic field in excess of 5000 G. Given that the magnetic field decreases with height in the solar atmosphere, no coronal magnetic field above ~2000 G was ever reported. Here, we present imaging microwave observations of an anomalously strong magnetic field of about 4000 G at the base of the corona in solar active region NOAA 12673 on 06 September 2017. Combining the photospheric vector measurements of the magnetic field and the coronal probing, we created and validated a nonlinear force-free field coronal model, with which we quantify the record-breaking coronal magnetic field at various coronal heights.