Nighttime Magnetic Perturbation Events Observed in Arctic Canada: 3. Occurrence and Amplitude as Functions of Magnetic Latitude, Local Time, and Magnetic Disturbance Indices

Abstract

We present 2 years of observations of ≥6 nT/s magnetic perturbation events (MPEs) from 5 high latitude Arctic stations. Most MPEs occurred within 30 min of a substorm onset, but substorms were neither necessary nor sufficient to cause MPEs. Premidnight and postmidnight MPEs had different temporal relations to substorms and occurred at slightly different latitudes.

Climatological Statistics of Extreme Geomagnetic Fluctuations with Periods from 1 s to 60 min

“…A secondary peak of occurrence is observed in the dawn-noon sector. Some of these peaks below 70°N may be associated with MPEs since they are consistent with the 02-06 MLT distribution observed by Engebretson et al (2021) for the station at 65°N geomagnetic, as noted above. However, this is also a region in which Pc5 pulsations are the dominant wave activity (e.g.…”

“…MPEs are a broad class of large (hundreds of nT), localised, 5-10 min unipolar or bipolar pulses of 𝐵 ℎ which occur in the auroral zone during substorms, but are not necessarily associated with substorm onsets (Engebretson et al, 2019a(Engebretson et al, ,b, 2020(Engebretson et al, , 2021Belakhovsky et al, 2019;Dimmock et al, 2019;Apatenkov et al, 2020;Viljanen, 1997). They arise from transient phenomena in the magnetotail such as bursty bulk flows (BBFs) (Angelopoulos et al, 1992;Wei et al, 2021), dipolarising flux bundles (Liu et al, 2014), poleward-expanding discrete aurorae passing over the magnetometer site (Ngwira et al, 2018), and small-scale rapidly moving ionospheric current vortices (Apatenkov et al, 2020).…”

“…expansion and recovery phases themselves, or with transient and localised MPEs, most of which occur within 30 min of a substorm onset Engebretson et al (2021). recently presented a statistical survey of MPEs at five Canadian sites (65-75°N geomagnetic) and their Fig.4showed that the distributions of MPE above a threshold of 6 nT/s (360 nT/min) (with a maximum of 37 nT/s (2220 nT/min)) contained a distribution in the range 02-06 MLT at only the lowest latitude station (65°N) whilst for the other four stations (71°N-75°N) a broad distribution of MPE occurrence was observed in the pre-midnight hours over 19-01 MLT.…”

Superposed Epoch Analysis of Nighttime Magnetic Perturbation Events Observed in Arctic Canada

“…Two papers reporting results from this work were published in 2019 (Engebretson, Pilipenko, et al, 2019;Engebretson, Steinmetz, et al, 2019): the first paper presented statistical results using data from these magnetometers, and the second presented 3 case studies using auroral imagers and spacecraft data as well. A third paper (Engebretson et al, 2021, henceforth referred to as paper 3), as well as another study that compared MPEs observed in the Arctic and Antarctic using some of these stations as well as stations in Greenland (Engebretson et al, 2020), showed several differences in characteristics between premidnight and postmidnight MPEs. At least some of the postmidnight events were associated with auroral omega bands, as also noted by Viljanen et al (2001) and Apatenkov et al (2020).…”

Characterization of Transient‐Large‐Amplitude Geomagnetic Perturbation Events

“…Therefore, significant efforts of the geophysical community are aimed at developing global MHD models of geomagnetic storm and substorm activity and incorporating the magnetotelluric response of the Earth to compute GICs (Pulkkinen et al., 2015; Zhang et al., 2012). However, beyond the largest space weather events, several studies suggest that there are more rapid, small‐scale and localized processes involved in generating some extreme GICs (Dimmock et al., 2020; Engebretson, Pilipenko, et al., 2019, Engebretson et al., 2021; Ngwira et al., 2015, 2018; Opgenoorth et al., 2020).…”