Extreme value analysis of the time derivative of the horizontal magnetic field and computed electric field

Abstract

Abstract. High-frequency ( ≈ minutes) variability of ground magnetic fields is caused by ionospheric and magnetospheric processes driven by the changing solar wind. The varying magnetic fields induce electrical fields that cause currents to flow in man-made conductors like power grids and pipelines. Under extreme conditions the geomagnetically induced currents (GIC) may be harmful to the power grids. Increasing our understanding of the extreme events is thus important for solar-terrestrial science and space weather. In this work 1-min resolution of the time derivative of measured local magnetic fields (|dB h /dt|) and computed electrical fields (E h ), for locations in Europe, have been analysed with extreme value analysis (EVA). The EVA results in an estimate of the generalized extreme value probability distribution that is described by three parameters: location, width, and shape. The shape parameter controls the extreme behaviour. The stations cover geomagnetic latitudes from 40 to 70 • N. All stations included in the study have contiguous coverage of 18 years or more with 1-min resolution data. As expected, the EVA shows that the higher latitude stations have higher probability of large |dB h /dt| and |E h | compared to stations further south. However, the EVA also shows that the shape of the distribution changes with magnetic latitude. The high latitudes have distributions that fall off faster to zero than the low latitudes, and upward bounded distributions can not be ruled out. The transition occurs around 59-61 • N magnetic latitudes. Thus, the EVA shows that the observed series north of ≈ 60 • N have already measured values that are close to the expected maxima values, while stations south of ≈ • N will measure larger values in the future.

Defining scale thresholds for geomagnetic storms through statistics

“…Therefore, the best fit functions for Dst and SYM-H do not have upper limits, theoretically. This is in agreement with the results in Wintoft et al (2016). However, the physical parameters that trigger geomagnetic storms may be upper limited by the finiteness on impulsivity of solar features, such as CME speed, solar wind 10 speed, shocks, which cannot take every kind of values, but have an empirical upper limit (finite size effect, e.g.…”

“…shown in different works, e.g., Love (2012); Nikitina et al (2016); Love et al (2016); Wintoft et al (2016), among others.…”

Quantifying the daily economic impact of extreme space weather due to failure in electricity transmission infrastructure

“…] and that d B /d t could be larger at subauroral latitudes than auroral latitudes [ Wintoft et al . ]. Following the trend observed by Rostoker and Duc Phan [], this suggests that the electrojet should move to even lower latitudes.…”

Improving the modeling of geomagnetically induced currents in Spain

“…The combination of all the above mentioned factors in a worst case scenario can make the storm time geoelectric induction reach hazardous levels at a local scale. Regarding the hazard assessment, upper limits for the potentially biggest geomagnetic storm or estimates of return periods of a hypothetical extreme event are thus of great value, which causes studies on probability of extreme values to proliferate [e.g., Thomson et al ., ; Pulkkinen et al ., ; Love , ; Ngwira et al ., ; Nikitina et al ., ; Wintoft et al ., ; Riley and Love , ].…”