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  • Solar Cycle Dependence of Very Large Nighttime Geomagnetic Disturbances (GMDs) Observed in Eastern Arctic Canada: Data

    work
    Creator:
    Engebretson, Mark J.
    Description:
    Large geomagnetic disturbances (GMDs, also denoted as MPEs - magnetic perturbation events) have sufficient amplitude to cause geomagnetically induced currents (GICs) that can damage technical infrastructure. In this study we present occurrence statistics for GMD / MPE events with derivatives ≥ 6 nT/s and ≥ 20 nT/s from five stations in the MACCS and AUTUMNX magnetometer arrays in Arctic Canada at magnetic latitudes ranging from 65° to 75°. Earlier studies using data from these arrays (Engebretson et al., 2019a,b, 2021a,b) covered only two years (2015 and 2017) and focused on latitude- and local time-dependent occurrence patterns and short-term dependencies on solar wind/IMF parameters and magnetospheric activity indices. This study presents all available data from these stations from 2011 through 2022 to analyze variations of GMD activity over a full solar cycle. Intense GMD activity did not closely follow the sunspot cycle, but instead was lowest during its rising phase and maximum (2011-2014), was highest during the early declining phase (2015-2017), and reached a subsequent minimum early in the following sunspot cycle (2020). GMDs with amplitude >20 nT/s followed the same yearly pattern but peaked even more strongly during 2015-2017. Most of these GMDs were associated with high-speed solar wind streams (Vsw > 600 km/s), but not with strongly negative values of the SYM/H index. The majority of these GMDs, irrespective of the Vsw value, were accompanied within 10 min (and most often less) by other events with amplitude ≥ 6 nT/s and showed a mostly poleward progression. These results show that large amplitude but spatially localized nighttime GMDs are primarily associated with high-speed stream geomagnetic drivers during the declining phase of the solar cycle. This indicates that large GIC hazard conditions can occur for a variety of solar wind drivers and geomagnetic conditions and not only for fast-coronal mass ejection driven storms.
    Keyword:
    geomagnetic disturbance events, geomagnetically induced currents
    Citation to related publication:
    Engebretson, M. J., Steinmetz, Yang, L., Pilipenko, V. A., Moldwin, M. B., McCuen, B. A., Connors, M. G., Weygand, J. M., Waters, C. L., Lyons, L. R., Nishimura, Y., Russell, C. T. (2023) Solar Cycle Dependence of Very Large Nighttime Geomagnetic Disturbances (GMDs) Observed in Eastern Arctic Canada. Journal of Geophysical Research – Space Physics
    Discipline:
    Science