Sfe: waiting for the big one

Abstract

Accurate measurements of the radiation delivered during the two largest solar flares ever observed are unavailable. In the case of the Carrington event (1858) the X-ray and UV radiation was not recorded, while in the case of the big flare which happened after the storm of 29-31 October 2003 we will call from now on as Halloween event (2003) the radiation saturated the X-ray radiometer. Despite many studies, a consensus regarding the real values of these events at the moment of maximum radiation has never been reached. In this paper, we used an alternative approach to try and determine these values. We estimated the values from the perturbations they produced in the Earth's magnetism -these are known as Solar Flare Effects (Sfe). Firstly, we established an empirical relationship between the variation in the radiation (cause) and its effect on the magnetism (consequence). Then, using the inverse function, we estimated the energy flux of both events. We found that both flares can actually be classified as being larger than X45. Finally, we also calculated the return period for a Carrington-like flare. Assuming that this event had an intensity of about X45 -according to our calculations -we estimated the return period to be 90 ± 60 years.

Comparison of predictive estimates of high‐latitude electrodynamics with observations of global‐scale Birkeland currents

“…It is now recognized that extreme events may present significant threats to modern utility power, communications, and navigation technology infrastructures [Tsurutani and Lakhina, 2014;Love et al, 2015;Curto et al, 2016;Pulkkinen et al, 2017]. Indeed, there is a societal imperative to quantitatively understand the likely geospace consequences of such events to provide reliable guidance for government policy, mitigation planning, and technology development [National Research Council, 2008; North American Electric Reliability Corporation GMD Task Force, 2012; National Science and Technology Council, 2015a; National Science and Technology Council, 2015b].…”

A great space weather event in February 1730

“…This historical evidence suggests that the Carrington event may not be so rare, with historical frequencies of about one event per century as suggested by theoretical and empirical discussions (e.g. Riley 2012;Curto et al 2016;Riley & Love 2017;Riley et al 2018).…”

“…The study of major events of past space weather provides crucial data on these events, which occur rarely in each century (Riley 2012;Curto et al 2016;Riley & Love 2017). Because of their rarity, these cases are of enormous interest to modellers of the magnetosphere, the heliosphere, and the disturbances that are propagated inside it.…”

Automatic detection of Sfe: a proposal

“…Observers estimate the diurnal variation trend by eye. However, a careless assessment of the S q level could mask the Sfe decay, which would translate directly into Sfe vector computation errors (Curto et al, 2016a). With the ideas proposed above we can improve the detection method but we will still not have achieved our goal, which is the complete automatization of the detection process.…”