Abstract
AbstractAn intriguing aspect of the famous September 2, 1859 geomagnetic disturbance (or “Carrington” event) is the horizontal magnetic (BH) data set measured in Colaba, India (magnetic latitude approximately 20°N). The field exhibits a sharp decrease of over 1,600 nT and a quick recovery of about 1,300 nT, all within a few hours during the daytime. The mechanism behind this has previously been attributed to magnetospheric processes, ionospheric processes or a combination of both. In this study, we outline our efforts to replicate this low‐latitude magnetic field using the Space Weather Modeling Framework. By simulating an extremely high pressure solar wind scenario, we can emulate the low‐latitude surface magnetic signal at Colaba. In our simulation, magnetospheric currents adjacent to the near‐Earth magnetopause and strong Region 1 field‐aligned currents are the main contributors to the large Colaba BH. The rapid recovery of BH in our simulated scenario is due to the retreat of these magnetospheric currents as the magnetosphere expands, as opposed to ring current dynamics. In addition, we find that the scenario that best emulated the surface magnetic field observations during the Carrington event had a minimum calculated Dst value between −431 and −1,191 nT, indicating that Dst may not be a suitable estimate of storm intensity for this kind of event.
Highlights
The Carrington event of 1-2 September 1859 is one of the largest geomagnetic storms on record and has been extensively studied as an example of a geomagnetic superstorm
The main contributions to the extremely negative BH at Colaba were due to the proximity of Westward electric currents adjacent to the magnetopause, as well as from strong Region 1 field-aligned currents (FACs)
As the solar wind pressure abated and the magnetopause moved away from the Earth, the quick recovery of BH at low-latitudes was primarily due to the motion of the Westward electric currents in the near-Earth dayside magnetosphere
Summary
The Carrington event of 1-2 September 1859 is one of the largest geomagnetic storms on record and has been extensively studied as an example of a geomagnetic superstorm. It is likely to have been more intense than any geomagnetic storm that has occurred in the satellite era, and there have been many efforts to classify its intensity in terms of Dst, a proxy measurement for the strength of the ring current, and a commonly used measure of storm intensity since 1957 [Tsurutani et al, 2003; Siscoe et al, 2006; Cliver & Dietrich, 2013]. The effects of the 1989 geomagnetic storm were intense enough to disrupt the Hydro-Quebec power system [Allen et al, 1989; Bolduc, 2002; Boteler , 2019], and were a Carrington-scale geomagnetic storm to occur today, it would probably result in widespread negative effects in grounded infrastructure such as long-distance power transmission grids [Oughton et al, 2017; Pulkkinen et al, 2017]
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