Extreme geomagnetically induced currents

Abstract

We propose an emergency alert framework for geomagnetically induced currents (GICs), based on the empirically extreme values and theoretical upper limits of the solar wind parameters and of dB/dt, the time derivative of magnetic field variations at ground. We expect this framework to be useful for preparing against extreme events. Our analysis is based on a review of various papers, including those presented during Extreme Space Weather Workshops held in Japan in 2011, 2012, 2013, and 2014. Large-amplitude dB/dt values are the major cause of hazards associated with three different types of GICs: (1) slow dB/dt with ring current evolution (RC-type), (2) fast dB/dt associated with auroral electrojet activity (AE-type), and (3) transient dB/dt of sudden commencements (SC-type). We set "caution," "warning," and "emergency" alert levels during the main phase of superstorms with the peak Dst index of less than −300 nT (once per 10 years), −600 nT (once per 60 years), or −900 nT (once per 100 years), respectively. The extreme dB/dt values of the AE-type GICs are 2000, 4000, and 6000 nT/min at caution, warning, and emergency levels, respectively. For the SCtype GICs, a "transient alert" is also proposed for dB/dt values of 40 nT/s at low latitudes and 110 nT/s at high latitudes, especially when the solar energetic particle flux is unusually high.

Defining scale thresholds for geomagnetic storms through statistics

“…The usual reasoning, which is the utilization of ad-hoc thresholds for calculations, appear, e.g., for mean residual life computation to estimate return periods, e.g., in Thomson et al (2011), or as percentile comparison in Nikitina et al (2016) in addition to the use of Q-Q plots (diagnostics tool based on the quartile comparison of a chosen distribution and 15 the data intended to be fitted), helping in the task of checking the goodness-of-fit of statistical distribution. Kataoka and Ngwira (2016) set some alert thresholds for geomagnetic disturbance and its rate of change, corresponding to different geomagnetic transients, without statistical distribution fit; or the percentile choice for proving the threshold independence of power laws in Wanliss and Weygand (2007).…”

Geomagnetically induced currents: Science, engineering, and applications readiness

“…Since CMEs are believed to cause the most significant GIC, they are of special interest especially in the extreme events context. Consequently, we recognize that to facilitate progress in capturing the key CME processes pertaining to GIC, it may be worthwhile to attack the transient transport modeling challenge in separate components (see Kataoka and Ngwira [], for a similar idea in terms of magnetospheric‐ionospheric response and GIC). CMEs have a series of elements driving magnetospheric‐ionospheric and geomagnetic activity.…”

Exploration of a Composite Index to Describe Magnetospheric Activity: Reduction of the Magnetospheric State Vector to a Single Scalar

“…The exploratory choice E (1) ≥ 2 for a storm definition found that E (1) ≥ 2 storms are associated with high levels of all geomagnetic indices and other magnetospheric measures in the magnetospheric state vector E . In future the choice of storms using a critical value of E (1) should be assessed by the association of those storms with the occurrences of important storm time phenomena such as spacecraft upsets (Choi et al, ), geomagnetically induced currents (Kataoka & Ngwira, ), radiation belt intensifications (Wrenn, ), great aurora (Jones, ), spacecraft‐charging events (Mullen et al, ), and solar energetic particles (Cane et al, ).…”