The Great Space Weather Event during February 1872 Recorded in East Asia

TL;DR

This study revisits the 1872 geomagnetic storm using East Asian auroral and sunspot records, demonstrating it was as extreme as the 1859 Carrington Event and highlighting its potential risks to modern infrastructure.

Contribution

It provides a detailed historical analysis of the 1872 geomagnetic storm, estimating the auroral oval boundary and comparing it to the Carrington Event using East Asian records.

Findings

The 1872 storm was as intense as the Carrington Event in auroral extent.

Auroral brightness indicated high-energy electron precipitation.

Auroral phases aligned with magnetic storm stages.

Abstract

The study of historical great geomagnetic storms is crucial for assessing the possible risks to the technological infrastructure of a modern society, caused by extreme space-weather events. The normal benchmark has been the great geomagnetic storm of September 1859, the so-called "Carrington Event". However, there are numerous records of another great geomagnetic storm in February 1872. This storm, about 12 years after the Carrington Event, resulted in comparable magnetic disturbances and auroral displays over large areas of the Earth. We have revisited this great geomagnetic storm in terms of the auroral and sunspot records in the historical documents from East Asia. In particular, we have surveyed the auroral records from East Asia and estimated the equatorward boundary of the auroral oval to be near 24.3 deg invariant latitude (ILAT), on the basis that the aurora was seen near the zenith at Shanghai (20 deg magnetic latitude, MLAT). These results confirm that this geomagnetic storm of February 1872 was as extreme as the Carrington Event, at least in terms of the equatorward motion of the auroral oval. Indeed, our results support the interpretation of the simultaneous auroral observations made at Bombay (10 deg MLAT). The East Asian auroral records have indicated extreme brightness, suggesting unusual precipitation of high-intensity, low-energy electrons during this geomagnetic storm. We have compared the duration of the East Asian auroral displays with magnetic observations in Bombay and found that the auroral displays occurred in the initial phase, main phase, and early recovery phase of the magnetic storm.