The Impact of Sudden Commencements on Ground Magnetic Field Variability: Immediate and Delayed Consequences

Abstract

Sudden Commencements (SCs) are linked to 25% of rates of change above 50 nT min −1 11 at low geomagnetic latitudes, e.g. < 10 • . 12• 90% of fluctuations above 50 nT min −1 occur within three days of an SC below 13 60 • latitude. 14• Only Storm Sudden Commencements have a link with elevated rates of change of 15 the field, either during the SSC or in the following days.

On the Considerations of Using Near Real Time Data for Space Weather Hazard Forecasting

“…Ultimately strong magnetic field variability is driven by a myriad of magnetospheric processes in near‐Earth space (e.g., Heyns et al., 2021; Rogers et al., 2020; Tsurutani & Hajra, 2021). Extreme field fluctuations are often linked to global scale transient phenomena such as geomagnetic storms (Dimmock et al., 2019; Kappenman & Albertson, 1990), substorms (Freeman et al., 2019; Turnbull et al., 2009; Viljanen et al., 2006) and sudden commencements (Rodger et al., 2017; Smith et al., 2019; Smith, Forsyth, Rae, Rodger, & Freeman, 2021).…”

Forecasting the Probability of Large Rates of Change of the Geomagnetic Field in the UK: Timescales, Horizons, and Thresholds

“…This would provide estimates at other latitudes and local times, noting the dependence of the rate of change of the field on local features such as geology (e.g., Dimmock et al, 2020;Ngwira et al, 2015). At different latitudes other magnetospheric phenomena will be more important (e.g., Rogers et al, 2020;Smith et al, 2021), which may impact the performance of the models with different combinations of input window and forecast horizons.…”

“…At different latitudes other magnetospheric phenomena will be more important (e.g. Rogers et al, 2020;Smith et al, 2021), which may impact the performance of the models with different combinations of input window and forecast horizons.…”

“…These sharp, predominantly northward deflections of the ground magnetic field are observed globally, and are related to rapid increases in solar wind dynamic pressure at the nose of the magnetosphere, the impact of a solar wind interplanetary shock for example, (Lühr et al., 2009; Takeuchi et al., 2002). The morphological signature of an SC is complex, with particularly strong latitudinal variations (Araki, 1994; Shinbori et al., 2012; Smith et al., 2021). At low latitudes, ground observations are dominated by a compressional signature that maximizes at noon and decreases toward midnight (Russell et al., 1992).…”

“…Meanwhile at higher latitudes the compressional component couples to shear Alfvén waves and field aligned resonances (Southwood & Kivelson, 1990). While the magnitude of the SC deflection has been found to increase with latitude (Fiori et al., 2014; Smith et al., 2021), significant associated GICs have been recorded at mid and low latitudes (Beland & Small, 2004; Carter et al., 2015; Kappenman, 2003; Marshall et al., 2012; Rodger et al., 2017; Zhang et al., 2015).…”