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- Title
Superposed Epoch Analyses of Geoelectric Field Disturbances in Japan in Response to Different Geomagnetic Activities.
- Authors
Zhang, T.; Ebihara, Y.
- Abstract
An increase in geomagnetically induced currents (GICs) is an inevitable result of geomagnetic field disturbances, and is harmful to the power grid, in particular, at high latitudes. At mid and low latitudes, the amplitude of the GICs is, in general, small, but large‐amplitude GICs are often observed during magnetic storms. It is of importance to understand major characteristics and extreme values of GICs at mid and low latitudes. For the geoelectric field disturbances ΔE observed at Kakioka (27.8° geomagnetic latitude) in Japan in 1996–2004, we performed superposed epoch analyses with respect to three types of geomagnetic disturbances: (a) storm sudden commencements (SSCs)/sudden impulses (SIs), (b) main phase of magnetic storms, and (c) bay disturbances. It is shown that the SSCs/SIs and the main phase of the magnetic storms are equally important for causing large‐amplitude disturbances of ΔE at Kakioka. GICs are thought to be amplified when the SIs and/or the bay disturbances occur during the magnetic storms. The maximum value of ΔE tends to be correlated with the maximum value of ΔH during the three types of events, where ΔH is the horizontal component of the geomagnetic field. Assuming that a quasi‐linear relationship between the maximum ΔE and the maximum ΔH is valid, we estimated GICs at three substations in Japan for an extreme SSCs/SIs, and the extreme magnetic storms. This scheme could be applicable to estimate roughly the GICs against extreme events, and to forecast the maximum GICs in a real‐time manner. Plain Language Summary: Geomagnetic fields are known to change in characteristic manners during the magnetic storms and substorms. However, characteristic changes in the geomagnetically induced electric fields on the ground are not well known. We performed superposed epoch analyses of the electric fields observed at Kakioka Magnetic Observatory in Japan to obtain an overview of the effects of associated electric current systems in near‐Earth space on the electric field and geomagnetically induced currents (GICs). Histograms of the maximum amplitude of the electric field are also provided. The correlation between changes in the horizontal component of the geomagnetic field and the electric field is found to be good for each type of disturbance. Using empirical equations to indicate the relationship between them, we can roughly estimate the maximum electric field at Kakioka and GICs flowing at three electrical substations in Japan for extreme disturbances. Key Points: We performed superposed epoch analyses of low‐latitude geoelectric field for storm sudden commencements (SSCs)/sudden impulses (SIs), magnetic storms and bay disturbancesSSCs/SIs and magnetic storms are almost equally important for large‐amplitude disturbances of geoelectric field at low‐latitudeWith empirical equations, we estimated geomagnetically induced currents flowing at three substations in Japan for extreme SSCs and extreme magnetic storms
- Subjects
JAPAN; GEOMAGNETISM; MAGNETIC storms; ELECTRIC currents; GEOMAGNETIC variations; ELECTRIC fields; AMPLITUDE estimation; EXTREME value theory
- Publication
Space Weather: The International Journal of Research & Applications, 2022, Vol 20, Issue 5, p1
- ISSN
1539-4956
- Publication type
Article
- DOI
10.1029/2021SW002893