# Occurrence of Great Magnetic Storms on 6-8 March 1582

## TL;DR

This study reconstructs a severe magnetic storm on 8 March 1582 using auroral records, revealing its duration, intensity, and possible cause, thus extending knowledge of historical space weather events before the 19th century.

## Contribution

It provides the first detailed analysis of a 1582 magnetic storm based on auroral evidence, estimating its severity and duration, and proposing a series of ICMEs as the cause.

## Key findings

- The storm was comparable in intensity to major 20th-century storms.
- Auroral oval extended to low latitudes, indicating a severe storm.
- The storm lasted at least three days, with auroras observed at mid- and low-latitudes.

## Abstract

Although knowing the occurrence frequency of severe space weather events is important for a modern society, it is insufficiently known due to the lack of magnetic or sunspot observations, before the Carrington event in 1859 known as one of the largest events during the last two centuries. Here, we show that a severe magnetic storm occurred on 8 March 1582 based on auroral records in East Asia. The equatorward boundary of auroral visibility reached 28.8{\deg} magnetic latitude. The equatorward boundary of the auroral oval is estimated to be 33.0{\deg} invariant latitude (ILAT), which is comparable to the storms on 25/26 September 1909 (~31.6{\deg} ILAT, minimum Dst of -595 nT), 28/29 August 1859 (~36.5{\deg} ILAT), and 13/14 March 1989 (~40{\deg} ILAT, minimum Dst of -589 nT). Assuming that the equatorward boundary is a proxy for the scale of magnetic storms, we presume that the storm on March 1582 was severe. We also found that the storm on March 1582 lasted, at least, for three days by combining European records. The auroral oval stayed at mid-latitude for the first two days and moved to low-latitude (in East Asia) for the last day. It is plausible that the storm was caused by a series of ICMEs (interplanetary coronal mass ejections). We can reasonably speculate that a first ICME could have cleaned up interplanetary space to make the following ICMEs more geo-effective, as probably occurred in the Carrington and Halloween storms.

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Source: https://tomesphere.com/paper/1905.08017