| Autor: |
Schillings, A., Palin, L., Opgenoorth, H. J., Hamrin, M., Rosenqvist, L., Gjerloev, J. W., Juusola, L., Barnes, R. |
| Předmět: |
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| Zdroj: |
Space Weather: The International Journal of Research & Applications; May2022, Vol. 20 Issue 5, p1-18, 18p |
| Abstrakt: |
The physical magnetospheric cause for geomagnetically induced currents (GICs) are rapid time‐varying magnetic fields (dB/dt), which occur mainly during magnetic substorms and storms. When, where and why exactly such rapid dB/dt may occur is insufficiently understood. We investigated all storms since 1980 and analyzed the negative and positive dB/dt spikes (>|500| nT/min) in the north and east component using a worldwide coverage (SuperMAG). Our analysis confirmed the existence of two dB/dt spikes "hotspots" located in the pre‐midnight and in the morning magnetic local time sector, independently of the geographic location of the stations. The associated physical phenomena are probably substorm current wedge onsets and westward traveling surges (WTS) in the evening sector, and wave‐ or vortex‐like current flows in the morning sector known as Omega bands. We observed a spatiotemporal evolution of the negative northern dB/dt spikes. The spikes initially occur in the pre‐midnight sector, and then develop in time toward the morning sector. This spatiotemporal sequence is correlated with bursts in the AE index, and can be repeated several times throughout a storm. Finally, we investigated the peak value of Dst and AE during the storm period in comparison with the dB/dt spike occurrence frequency, we did not find any correlation. This result implies that a moderate storm with many spikes can be as (or more) dangerous for ground‐based infrastructures than a major storm with fewer dB/dt spikes. Our findings regarding the physical causes and characteristics of dB/dt spikes may help to improve the GIC forecast for the affected regions. Plain Language Summary: Space weather prognosis is similar to meteorological weather but for predicting space events that can potentially damage humans technologies. One phenomenon are the geomagnetically induced currents or commonly called GICs. They are created by rapid fluctuations in the Earth's magnetic field, which can lead to power black outs and damages in communication systems. These rapid fluctuations are measured by worldwide magnetometers and defined as the time derivative of the magnetic field. In this study, we investigate the spikes in the time derivative for the two horizontal components, namely the northern and eastern component with a threshold of ±500 nT/min. Our first result shows that these rapid fluctuations mainly occur in the magnetic local time (MLT) pre‐midnight and morning sectors. We identified the possible physical phenomena that could caused the fluctuations. We also found that the spikes develop in space and time from the evening toward the morning MLT sectors. Finally, we found that a major geomagnetic storm does not necessary cause more spikes then a less intense one. Our findings concerning the physical nature of fast intense magnetic variations may help to improve the forecast of GICs. Key Points: During storms, dB/dt spikes follow a general spatiotemporal development starting in the pre‐midnight toward the morning sectorConfirmation of 2 dB/dt hotspots (pre‐midnight and morning sector) with different component characteristics independent of station locationThe peak value of Dst and AL indices during the entire storm is not correlated with the dB/dt spikes occurrence frequency of the storm [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
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