Articles | Volume 43, issue 1
https://doi.org/10.5194/angeo-43-241-2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/angeo-43-241-2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Regular paper
| 
20 May 2025
Regular paper |
| 20 May 2025
| 20 May 2025
A critical review and presentation of the complete, historic series of K indices as determined at Norwegian magnetic observatories since 1939
Ingeborg Frøystein
Department of Physics and Technology, UiT the Arctic University of Norway, Tromsø, Norway
Tromsø Geophysical Observatory, Faculty of Science and Technology, UiT The Arctic University of Norway, Tromsø, Norway
Magnar Gullikstad Johnsen
CORRESPONDING AUTHOR
Tromsø Geophysical Observatory, Faculty of Science and Technology, UiT The Arctic University of Norway, Tromsø, Norway
Related authors
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Kian Sartipzadeh, Andreas Kvammen, Björn Gustavsson, Njål Gulbrandsen, Magnar Gullikstad Johnsen, Devin Huyghebaert, and Juha Vierinen
EGUsphere, https://doi.org/10.5194/egusphere-2025-3070, https://doi.org/10.5194/egusphere-2025-3070, 2025
Short summary
Short summary
Knowing charged particle densities high above Earth is key for forecasting space weather effects on satellites and communications, but they are difficult to estimate at high latitudes because of auroras. We built an artificial intelligence model for northern Norway using radar observations, magnetic field measurements, geophysical indices and solar activity. It produces more accurate estimates than existing methods, even during auroral events, and can be adapted to other regions.
Sota Nanjo, Masatoshi Yamauchi, Magnar Gullikstad Johnsen, Yoshihiro Yokoyama, Urban Brändström, Yasunobu Ogawa, Anna Naemi Willer, and Keisuke Hosokawa
Ann. Geophys., 43, 303–317, https://doi.org/10.5194/angeo-43-303-2025, https://doi.org/10.5194/angeo-43-303-2025, 2025
Short summary
Short summary
Our research explores the shock aurora, which is typically observed on the dayside due to the rapid compression of the Earth's magnetic field. We observed this rare aurora on the nightside, a region where such events are difficult to detect. Using ground-based cameras, we identified new features, including leaping and vortex-like patterns. These findings offer a fresh insight into the interactions between the solar wind and the magnetosphere, enhancing our understanding of space weather and its effects.
Masatoshi Yamauchi, Magnar G. Johnsen, Carl-Fredrik Enell, Anders Tjulin, Anna Willer, and Dmitry A. Sormakov
Ann. Geophys., 38, 1159–1170, https://doi.org/10.5194/angeo-38-1159-2020, https://doi.org/10.5194/angeo-38-1159-2020, 2020
Short summary
Short summary
The paper reports a new finding on space weather effects at around 70–75 ° geographic latitudes. We found that X flares cause an unexpectedly strong ionospheric current driven by solar flares. The effect is as large as a substorm that is known to cause strong auroras and may enhance ongoing substorms. However, it has been overlooked in the past due to the narrow latitudinal range at high latitudes. Since severe magnetic storms often occur with X flares, this may cause geomagnetic hazards.
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Short summary
The complete time series of the geomagnetic disturbance index (K) from Norwegian magnetic observatories have been digitized. We compare and discuss the tree methods used to derive the index, finding that each method has strengths and weaknesses. In total, we present all K indices derived from Norwegian observatories since the 1930s until today, the used derivation methods and the long historic time series as a whole, enabling critical use for future scientific work.
The complete time series of the geomagnetic disturbance index (K) from Norwegian magnetic...
