01 Feb 2022
01 Feb 2022
Status: a revised version of this preprint is currently under review for the journal ANGEO.

The time derivative of the geomagnetic field has a short memory

Mirjam Kellinsalmi1,2, Ari Viljanen1, Liisa Juusola1, and Sebastian Käki1,2 Mirjam Kellinsalmi et al.
  • 1Finnish Meteorological Institute
  • 2University of Helsinki

Abstract. Solar eruptions and other types of space weather effects can pose a hazard to the Earth's power grids via geomagnetically induced currents (GIC). In worst cases, they can even cause large scale power outages. GIC are a complex phenomenon, closely related to the time derivative of the geomagnetic field. However, the behavior of the time derivative is chaotic and has proven to be tricky to predict. In our study, we look at the dynamics of the geomagnetic field during active space weather. We try to characterize the magnetic field behavior, to better understand the drivers behind strong GIC events. We use geomagnetic data from the IMAGE (International Monitor for Auroral Geomagnetic Effect) magnetometer network between 1996 and 2018. The measured geomagnetic field is primarily produced by currents in the ionosphere and magnetosphere and secondarily by currents in the conducting ground. We use the so called separated magnetic field in our analysis. The separation of the field means, that the measured magnetic field is computationally divided into external and internal parts based on the field's ionospheric or telluric origin. We study the yearly directional distributions of the separated horizontal geomagnetic field and its time derivative. The yearly distributions do not have a clear solar cycle dependency. The internal field distributions are more scattered than the external field. There are also clear, station specific differences in the distributions. One of our main findings is that the direction of the geomagnetic field time derivative has a very short "reset time", around two minutes, but the total horizontal field does not have this kind of behavior. These results hold true even with less active space weather conditions. We conclude that this result gives insight into the time scale of ionospheric current systems, which are the primary driver behind the time derivative's behavior.

Mirjam Kellinsalmi et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • CC1: 'Comment on angeo-2022-4: Methodology and circular mean', Spencer Hatch, 04 Feb 2022
    • AC1: 'Reply on CC1', Mirjam Kellinsalmi, 04 Feb 2022
      • CC2: 'Reply to AC1', Spencer Hatch, 07 Feb 2022
  • RC1: 'Comment on angeo-2022-4', Anonymous Referee #1, 15 Feb 2022
    • AC2: 'Reply on RC1', Mirjam Kellinsalmi, 25 Feb 2022
  • RC2: 'Comment on angeo-2022-4', Anonymous Referee #2, 03 Mar 2022
    • AC3: 'Reply on RC2', Mirjam Kellinsalmi, 15 Mar 2022

Mirjam Kellinsalmi et al.

Mirjam Kellinsalmi et al.


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Short summary
Eruptions from the Sun can pose a hazard to Earth's power grids via geomagnetically induced currents (GIC). We study magnetic measurements from Fennoscandia to find ways to understand and forecast GIC. We find that the direction of the time derivative of the magnetic field has a short “reset time”, about two minutes. We conclude that this result gives insight on the current systems high in Earth’s atmosphere, which are the main driver behind the time derivative’s behavior and GIC formation.