Long‐Lasting Geomagnetically Induced Currents and Harmonic Distortion Observed in New Zealand During the 7–8 September 2017 Disturbed Period

Clilverd, Mark A.; Rodger, Craig J.; Brundell, James B.; Dalzell, Michael D; Martin, Ian; Manus, Daniel H. Mac; Thomson, Nicholas R.; Petersen, Tanja; Obana, Yuki

doi:10.1029/2018sw001822

Cited by 58 publications

(103 citation statements)

References 33 publications

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“…This result is also consistent with a similar case study performed by for the 6-7 April 2000 geomagnetic storm, although their GIC readings in the same pipeline were smaller than in this case. Further evidence of a substorm during this time was reported by Clilverd et al (2018) based on the Wp index (Nosé et al, 2012). Similar to this study and around the same UT time, Clilverd et al (2018) showed enhanced GICs of almost 35 A at the Halfway Bush substation in Dunedin, South Island, New Zealand.…”

Section: Observationssupporting

confidence: 87%

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The GIC and Geomagnetic Response Over Fennoscandia to the 7–8 September 2017 Geomagnetic Storm

et al. 2019

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Between 7 and 8 September 2017, Earth experienced extreme space weather events. We have combined measurements made by the IMAGE magnetometer array, ionospheric equivalent currents, geomagnetically induced current (GIC) recordings in the Finnish natural gas pipeline, and multiple ground conductivity models to study the Fennoscandia ground effects. This unique analysis has revealed multiple interesting physical and technical insights. We show that although the 7–8 September event was significant by global indices (Dst∼150 nT), it produced an unexpectedly large peak GIC. It is intriguing that our peak GIC did not occur during the intervals of largest geomagnetic depressions, nor was there any clear upstream trigger. Another important insight into this event is that unusually large and rare GIC amplitudes (>10 A) occurred in multiple Magnetic Local Time (MLT) sectors and could be associated with westward and eastward electrojets. We were also successfully able to model the geoelectric field and GIC using multiple models, thus providing a further important validation of these models for an extreme event. A key result from our multiple conductivity model comparison was the good agreement between the temporal features of 1‐D and 3‐D model results. This provides an important justification for past and future uses of 1‐D models at Mäntsälä which is highly relevant to additional uses of this data set. Although the temporal agreement (after scaling) was good, we found a large (factor of 4) difference in the amplitudes between local and global ground models due to the difference in model conductivities. Thus, going forward, obtaining accurate ground conductivity values are key for GIC modeling.

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Section: Observationssupporting

confidence: 87%

“…As previous studies have shown (Anderson & Fuselier, ), this reiterates that the EE is also important to driving large GICs. It is particularly worth noting that this interval also appeared to be part of a larger global response (Clilverd et al, ).…”

Section: Discussionmentioning

confidence: 95%

The GIC and Geomagnetic Response Over Fennoscandia to the 7–8 September 2017 Geomagnetic Storm

et al. 2019

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“…Instead, SCs are known to often be followed by prolonged magnetospheric activity that can result in damaging GICs Pulkkinen et al (), Clilverd et al (). We have shown that, for the United Kingdom, the percentiles of R are elevated above background levels for 3 days following an SC.…”

Section: Discussionmentioning

confidence: 99%

The Influence of Sudden Commencements on the Rate of Change of the Surface Horizontal Magnetic Field in the United Kingdom

Smith¹,

Freeman

Rae³

et al. 2019

Space Weather

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Sudden commencements (SCs) are rapid increases in the northward component of the surface geomagnetic field, related to sharp increases in the dynamic pressure of the solar wind. Large rates of change of the geomagnetic field can induce damaging currents in ground power networks. In this work, the effect of SCs on the (1 min) rate of change of the surface magnetic field (R) at three U.K. stations is investigated. The distributions of R during SCs are shifted to higher values than the data set as a whole. Rates of change greater than 10 nT/min are 30–100 times more likely during SCs, though less than 8% of the most extreme R (≥99.99th percentile) are observed during SCs. SCs may also precede geomagnetic storms, another potential source of large R. We find that the probability of observing large a R is greatly enhanced for 3 days following an SC. In the 24 hr following an SC it is 10 times more likely than at any given time to observe rates of change between 10 and several hundred nT/min. Additionally, between 90% and 94% of data (depending on station) above the 99.97th percentile is recorded within 3 days of an SC. All values of R ≥ 200 nT/min in the United Kingdom have been observed within 3 days of an SC. These results suggest that accurately predicting SCs is critically important to identify intervals during which power networks at similar geomagnetic latitudes to the United Kingdom are at risk from large geomagnetically induced currents.

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“…This explosion produced a Coronal mass ejections (CME) and triggered a geomagnetic storm on 7 September. Many studies have investigated the ionospheric responses to the geomagnetic storm (e.g., Aa et al, 2018;Clilverd et al, 2018;Jin et al, 2018;Lei et al, 2018;Li et al, 2018;Yamauchi et al, 2018). Figure 2a shows the X-ray flux variation at the interval of 10-15 UT on 6 September.…”

Section: Datamentioning

confidence: 99%

Equatorial Ionospheric Electrodynamics Over Jicamarca During the 6–11 September 2017 Space Weather Event

Zhang

Liu

et al. 2019

JGR Space Physics

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We use the observations from the incoherent scatter radar and the magnetometers over Jicamarca (11.95° S, 76.87° W) sector to investigate the equatorial ionospheric electrodynamics on 6–11 September 2017. In this period, there are three X‐class solar flares peaked at 12:02, 14:36, and 16:06 UT on 6, 7, and 10 September, respectively, in the local daytime of Jicamarca and a storm with the minimum SYM‐H of −146 nT at 01:08 UT on 8 September. The results reveal that the three X‐class flares drive the westward disturbance electric field in equatorial region. The flares intensify the westward and eastward equatorial electrojets on 6 and 10 September, while the eastward equatorial electrojet enhances first and then declines on the 7 September flare. The depletion in equatorial electrojet during flare is suggested to be the effects of the weakened electric field. In the storm recovery, the disturbance electric field is westward at ~10–16 LT and eastward at postmidnight and early morning sectors on 9–11 September, which is mainly driven by disturbance dynamo electric field (DDEF). Further, it is found that the westward DDEF first occurs at high altitudes and then at low altitudes around 10 LT, and the westward DDEF at 200–500 km has magnitudes increasing with altitudes. Meanwhile, the Jicamarca incoherent scatter radar observations show distinct altitudinal differences in the responses of the F region electron density to the disturbance electric field.

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Long‐Lasting Geomagnetically Induced Currents and Harmonic Distortion Observed in New Zealand During the 7–8 September 2017 Disturbed Period

Cited by 58 publications

References 33 publications

The GIC and Geomagnetic Response Over Fennoscandia to the 7–8 September 2017 Geomagnetic Storm

The GIC and Geomagnetic Response Over Fennoscandia to the 7–8 September 2017 Geomagnetic Storm

The Influence of Sudden Commencements on the Rate of Change of the Surface Horizontal Magnetic Field in the United Kingdom

Equatorial Ionospheric Electrodynamics Over Jicamarca During the 6–11 September 2017 Space Weather Event

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