On extreme geomagnetic storms

Abstract

Extreme geomagnetic storms are considered as one of the major natural hazards for technology-dependent society. Geomagnetic field disturbances can disrupt the operation of critical infrastructures relying on space-based assets, and can also result in terrestrial effects, such as the Quebec electrical disruption in 1989. Forecasting potential hazards is a matter of high priority, but considering large flares as the only criterion for early-warning systems has demonstrated to release a large amount of false alarms and misses. Moreover, the quantification of the severity of the geomagnetic disturbance at the terrestrial surface using indices as Dst cannot be considered as the best approach to give account of the damage in utilities. High temporal resolution local indices come out as a possible solution to this issue, as disturbances recorded at the terrestrial surface differ largely both in latitude and longitude. The recovery phase of extreme storms presents also some peculiar features which make it different from other less intense storms. This paper goes through all these issues related to extreme storms by analysing a few events, highlighting the March 1989 storm, related to the Quebec blackout, and the October 2003 event, when several transformers burnt out in South Africa.

Identification of the different magnetic field contributions during a geomagnetic storm in magnetospheric and ground observations

“…It has been recently suggested that local geomagnetic indices could represent very useful tools, complementary to global indices, in defining deviations from the usual geomagnetic activity. In fact, local geomagnetic disturbances seem to play T. Alberti et al: Geomagnetic storm: EMD Approach a key role in assessing the potential risk factor of extreme events in specific regions (Cid et al, 2014). So, it can be useful to investigate the time evolution of a baseline of the geomagnetic field defined as the local geomagnetic activity observed on large scales.…”

Dynamics of large‐scale solar wind streams obtained by the double superposed epoch analysis

“…Only disturbed types of SW streams can contain the IMF component perpendicular to the ecliptic plane and in particular the southward IMF component. Such disturbed types are the following SW streams: interplanetary manifestation of coronal mass ejection (ICME) including magnetic cloud (MC) and Ejecta, Sheath-compression region before ICME and corotating interaction region (CIR)-compression region before high-speed stream (HSS) of solar wind (see reviews and recent papers by Gonzalez et al [1999], Huttunen and Koskinen [2004], Yermolaev [2006, 2010], Zhang et al [2007], Yermolaev et al [2012], Hietala et al [2014], Cid et al [2014], Katus et al [2015], and references therein). In the mentioned above works the SW types are considered as sources of magnetospheric disturbance, i.e., the selection of SW events is carried out in connection with magnetospheric activity.…”

Extreme geomagnetically induced currents

“…For example, Nagatsuma et al (2015) estimated that the solar wind speed of 960 km/s and southward interplanetary magnetic field Bz of −50 nT continuing for 5 h drove the main phase of the March 1989 storm, whereas Lakhina and Tsurutani (2016) indicated that the interplanetary driver of the March 1989 storm included multiple shocks, multiple sheaths, and multiple magnetic clouds. It is therefore reasonable to assume that a perfect "slot machine"-type combination of solar wind parameters sometimes results from the complex interactions of chains of coronal mass ejections during their propagation in the solar wind (Cid et al 2014;Kataoka et al 2015).…”