Speaker
Description
On May 10th 2024, the first of at least five interplanetary coronal mass ejections (ICMEs) arrived at Earth and caused the strongest geomagnetic storm (Gannon storm) in over twenty years. The effect of this storm was global, however in this study the effect on the Swedish power grid is in focus. By using satellite data from Wind, ground magnetometer data from the IMAGE network and ground conductivity modeling over the region, we study this storm from the solar wind down to the induced geoelectric field in the ground. A large induced geoelectric field is the leading cause of space weather related disturbances in the power grid and during this geomagnetic storm a disturbance was reported in southern Sweden. The disturbance occurred at 22:29 UT May 10th in the connecting line to the SwePol power line, connecting Sweden and Poland. Our analysis show that there are two clearly separated signatures on the ground, before and after the disturbance, which reached the same level of dB/dt and geoelectric field but can be connected to different solar wind drivers. Further, this event is put into context by analyzing two previous disturbances in the same power line, confirmed to be caused by geomagnetically induced currents (GICs). Another aspect of this study is the effect of timing and magnetic local time (MLT) to determine if the impact could have been worse or fundamentally different had the ICME arrived at a different time. Due to the complex structure of the interplanetary magnetic field (IMF) caused by the multiple ICMEs, timing is even more important in order to understand the effects of the complicated, embedded structures traveling with the solar wind. Through this timing analysis, we can see that Sweden's MLT experienced the worst of the storm at the time of the disturbance, but if the ICME would have arrived ten hours before, the effect would have been much greater, with electric field values more severe than those with an expected occurrence once every 100 years (Lanabere et al, 2024). This emphasises the unique impact merged ICME structures can have on a given region. The results of this study also highlight the need for further development of other parameters that accurately correlate with GIC effects, since the time of the reported incident did not coincide with the peak geoelectric field throughout the storm.
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