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
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The dayside auroral region is a highly dynamic region of the ionosphere that is influenced by the coupling between the solar wind, magnetosphere, and ionosphere. In this paper, we illustrate this dynamic nature and present a quantitative analysis of both altitudinal and latitudinal variation within the region. In addition, ionospheric parameters on closed field lines, along the open-closed field line boundary and in the polar cap are statistically compared.
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The dayside auroral region is a highly dynamic region of the ionosphere that is influenced by the coupling between the solar wind, magnetosphere, and ionosphere. In this paper, we illustrate this dynamic nature and present a quantitative analysis of both altitudinal and latitudinal variation within the region. In addition, ionospheric parameters on closed field lines, along the open-closed field line boundary and in the polar cap are statistically compared.
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Ultra-low frequency (ULF) signals are observed using ground based magnetometers. We apply four years of data from West Greenland in a statistical analysis of ULF signal distribution as a function of season, latitude, local time, and solar wind conditions. We identify a ULF signal population associated with the magnetospheric cusp that is separate from the auroral oval during summer. Earlier studies, which were mainly performed in winter, failed to unambiguously identify these signals.
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During the New Year's Day storm of 2025, we filmed the northern lights as razor-thin, picket-like stripes that sometimes appeared in far-apart places at the same moment. Using ground cameras together with Earth-orbiting satellites, we found signs of local heating and swift winds in the upper atmosphere that would help form these stripes. Our study clarifies where and how such patterns arise and improves understanding of how the upper atmosphere responds to solar storms.
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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.
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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.
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Van Sabben, D., Siebert, M., and IAGA: IAGA Bulletin no. 12w1 – Geomagnetic Data 1969, Indices K and Ci, IUGG Publications Office, https://doi.org/10.25577/kvcs-ey31, 1971. a, b
Veldkamp, J., Siebert, M., and IAGA: IAGA Bulletin no. 12t1 – Geomagnetic Data 1965, Indices K and C, IUGG Publications Office, https://doi.org/10.25577/5qkt-zt70, 1968. a, b
Veldkamp, J., Siebert, M., and IAGA: IAGA Bulletin no. 12u1 – Geomagnetic Data 1966, Indices K and C, IUGG Publications Office, https://doi.org/10.25577/4rcx-pq55, 1969. a, b
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Wasserfall, K. F.: Results from the magnetic station at Dombås 1946, 1947, 1948, Publikasjoner fra Det norske institutt for kosmisk fysikk, no. 35, 1953. a
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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...
