Why Are Some Solar Wind Pressure Pulses Followed by Geomagnetic Storms?

Fogg, A. R.; Jackman, C. M.; Coco, I.; Douglas Rooney, L.; Weigt, D. M.; Lester, M.

doi:10.1029/2022ja031259

Cited by 3 publications

(1 citation statement)

References 61 publications

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“…For the period between 2001 and 2020 this list comprises a total of 232 SCs, a subset of which will have the requisite GIC data at each of the 75 transformers. Further, we define an SSC to be an SC that is followed within 24 hr by a SymH of −50 nT or less, a similar criteria to that typically employed (e.g., Fiori et al., 2014; Fogg, Jackman, Coco, et al., 2023; Smith, Forsyth, Rae, Rodger, & Freeman, 2021). Meanwhile, if SymH exceeds −50 nT for the 24 hr after the SC then it is categorized as an SI.…”

Section: Datamentioning

confidence: 99%

Sudden Commencements and Geomagnetically Induced Currents in New Zealand: Correlations and Dependance

Smith,

Rodger,

Mac Manus

et al. 2024

Space Weather

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Changes in the Earth's geomagnetic field induce geoelectric fields in the solid Earth. These electric fields drive Geomagnetically Induced Currents (GICs) in grounded, conducting infrastructure. These GICs can damage or degrade equipment if they are sufficiently intense—understanding and forecasting them is of critical importance. One of the key magnetospheric phenomena are Sudden Commencements (SCs). To examine the potential impact of SCs we evaluate the correlation between the measured maximum GICs and rate of change of the magnetic field (H′) in 75 power grid transformers across New Zealand between 2001 and 2020. The maximum observed H′ and GIC correlate well, with correlation coefficients (r2) around 0.7. We investigate the gradient of the relationship between H′ and GIC, finding a hot spot close to Dunedin: where a given H′ will drive the largest relative current (0.5 A nT−1 min). We observe strong intralocation variability, with the gradients varying by a factor of two or more at adjacent transformers. We find that GICs are (on average) greater if they are related to: (a) Storm Sudden Commencements (SSCs; 27% larger than Sudden Impulses, SIs); (b) SCs while New Zealand is on the dayside of the Earth (27% larger than the nightside); and (c) SCs with a predominantly East‐West magnetic field change (14% larger than North‐South equivalents). These results are attributed to the geology of New Zealand and the geometry of the power network. We extrapolate to find that transformers near Dunedin would see 2000 A or more during a theoretical extreme SC (H′ = 4000 nT min−1).

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Section: Datamentioning

confidence: 99%

Sudden Commencements and Geomagnetically Induced Currents in New Zealand: Correlations and Dependance

Smith,

Rodger,

Mac Manus

et al. 2024

Space Weather

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Predicting Interplanetary Shock Occurrence for Solar Cycle 25: Opportunities and Challenges in Space Weather Research

Oliveira,

Allen,

Alves

et al. 2024

Space Weather

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Interplanetary (IP) shocks are perturbations observed in the solar wind. IP shocks correlate well with solar activity, being more numerous during times of high sunspot numbers. Earth‐bound IP shocks cause many space weather effects that are promptly observed in geospace and on the ground. Such effects can pose considerable threats to human assets in space and on the ground, including satellites in the upper atmosphere and power infrastructure. Thus, it is of great interest to the space weather community to (a) keep an accurate catalog of shocks observed near Earth, and (b) be able to forecast shock occurrence as a function of the solar cycle (SC). In this work, we use a supervised machine learning regression model to predict the number of shocks expected in SC25 using three previously published sunspot predictions for the same cycle. We predict shock counts to be around 275 ± 10, which is ∼47% higher than the shock occurrence in SC24 (187 ± 8), but still smaller than the shock occurrence in SC23 (343 ± 12). With the perspective of having more IP shocks on the horizon for SC25, we briefly discuss many opportunities in space weather research for the remainder years of SC25. The next decade or so will bring unprecedented opportunities for research and forecasting effects in the solar wind, magnetosphere, ionosphere, and on the ground. As a result, we predict SC25 will offer excellent opportunities for shock occurrences and data availability for conducting space weather research and forecasting.

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Quantification of magnetosphere–ionosphere coupling timescales using mutual information: response of terrestrial radio emissions and ionospheric–magnetospheric currents

Fogg,

Jackman,

Chapman

et al. 2024

Nonlin. Processes Geophys.

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Abstract. Auroral kilometric radiation (AKR) is a terrestrial radio emission excited by the same accelerated electrons which excite auroral emissions. Although it is well correlated with auroral and geomagnetic activity, the coupling timescales between AKR and different magnetospheric or ionospheric regions have yet to be determined. Estimation of these coupling timescales is non-trivial as a result of complex, non-linear processes which rarely occur in isolation. In this study, the mutual information between AKR intensity and different geomagnetic indices is used to assess the correlation between variables. Indices are shifted to different temporal lags relative to AKR intensity, and the lag at which the variables have the most shared information is found. This lag is interpreted as the coupling timescale. The AKR source region receives the effects of a shared driver before the auroral ionosphere. Conversely, the polar ionosphere reacts to a shared driver before the AKR source region. Bow shock interplanetary magnetic field BZ is excited about 1 h before AKR enhancements. This work provides quantitatively determined temporal context to the coupling timelines at Earth. The results suggest that there is a sequence of excitation following the onset of a shared driver: first, the polar ionosphere feels the effects, followed by the AKR source region and then the auroral ionosphere.

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Why Are Some Solar Wind Pressure Pulses Followed by Geomagnetic Storms?

Cited by 3 publications

References 61 publications

Sudden Commencements and Geomagnetically Induced Currents in New Zealand: Correlations and Dependance

Sudden Commencements and Geomagnetically Induced Currents in New Zealand: Correlations and Dependance

Predicting Interplanetary Shock Occurrence for Solar Cycle 25: Opportunities and Challenges in Space Weather Research

Quantification of magnetosphere–ionosphere coupling timescales using mutual information: response of terrestrial radio emissions and ionospheric–magnetospheric currents

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