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.
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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Sota Nanjo, Masatoshi Yamauchi, Magnar Gullikstad Johnsen, Yoshihiro Yokoyama, Urban Brändström, Yasunobu Ogawa, Anna Naemi Willer, and Keisuke Hosokawa
EGUsphere, https://doi.org/10.5194/egusphere-2024-3277, https://doi.org/10.5194/egusphere-2024-3277, 2024
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Our research explored the "shock aurora," caused by the impact of solar wind particles on Earth's magnetic field. On February 26, 2023, we observed this rare event on the nightside, where such observations are difficult. Ground-based cameras revealed new structural features, including undulating and jumping patterns. These results provide fresh insights into the complex interactions between the solar wind and Earth's magnetosphere, enhancing our understanding of space weather 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
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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.
Nadezda Yagova, Natalia Nosikova, Lisa Baddeley, Olga Kozyreva, Dag A. Lorentzen, Vyacheslav Pilipenko, and Magnar G. Johnsen
Ann. Geophys., 35, 365–376, https://doi.org/10.5194/angeo-35-365-2017, https://doi.org/10.5194/angeo-35-365-2017, 2017
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A substorm is a dramatic phenomenon in the near-Earth space that is visualized as an aurora. Mostly substorms are caused by changes in the solar wind, but some of them can develop without any evident trigger. Such substorms together with undisturbed days were investigated using magnetometer and photometer data from Svalbard. Substorm precursors, i.e., specific features in 1–4 mHz geomagnetic and auroral luminosity pulsations, have been found at high geomagnetic latitudes.
C. Xiong, H. Lühr, H. Wang, and M. G. Johnsen
Ann. Geophys., 32, 609–622, https://doi.org/10.5194/angeo-32-609-2014, https://doi.org/10.5194/angeo-32-609-2014, 2014
Related subject area
Subject: Earth's ionosphere & aeronomy | Keywords: Ionospheric variability
Acoustic–gravity waves and their role in the ionospheric D region–lower thermosphere interaction
Characteristic analysis of the differences between total electron content (TEC) values in global ionosphere map (GIM) grids
Contribution of meteor flux in the occurrence of sporadic-E (Es) layers over the Arabian Peninsula
Epoch-by-epoch estimation and analysis of BeiDou Navigation Satellite System (BDS) receiver differential code biases with the additional BDS-3 observations
Ionosonde total electron content evaluation using International Global Navigation Satellite System Service data
Spatial and seasonal effects on the delayed ionospheric response to solar EUV changes
Ionospheric total electron content responses to HILDCAA intervals
Variations of the 630.0 nm airglow emission with meridional neutral wind and neutral temperature around midnight
Gordana Jovanovic
Ann. Geophys., 42, 491–500, https://doi.org/10.5194/angeo-42-491-2024, https://doi.org/10.5194/angeo-42-491-2024, 2024
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The dispersion equation and the reflection coefficient are elegant tools for investigating acoustic–gravity waves (AGWs) in stratified atmospheres. AGWs are used to study the the ionospheric D region–lower thermosphere interaction. This is important because these waves, and especially gravity waves, can produce ionospheric disturbances and an increase in lower thermospheric temperature. The results of this article can be applied to the stratified atmospheres of the planets and the Sun.
Qisheng Wang, Jiaru Zhu, and Genxin Yang
Ann. Geophys., 42, 45–53, https://doi.org/10.5194/angeo-42-45-2024, https://doi.org/10.5194/angeo-42-45-2024, 2024
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The GIM data of 2 years from high solar activity (2014) and low solar activity (2021) provided by CODE (Center for Orbit Determination in Europe) are selected to calculate the total electron content (TEC) difference for each grid point in this paper. Based on the calculation of the spatial and temporal variations in the difference values, both spatial and temporal characteristics of the TEC difference values of the four grid points within the grid are analyzed in detail.
Muhammad Mubasshir Shaikh, Govardan Gopakumar, Aisha Abdulla Al-owais, Maryam Essa Sharif, and Ilias Fernini
Ann. Geophys., 39, 471–478, https://doi.org/10.5194/angeo-39-471-2021, https://doi.org/10.5194/angeo-39-471-2021, 2021
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We report observations of sporadic-E (Es) layers and visual meteor count data simultaneously observed during night-time over the Arabian Peninsula. A constant and well-established presence of Es has been reported with a consistent count of meteors also present throughout the 1-year observation period. Data show that the Es observations are not dependent on the presence of meteor flux; i.e., the presence of meteors is not the main cause of the presence of Es over the Arabian Peninsula.
Qisheng Wang, Shuanggen Jin, and Youjian Hu
Ann. Geophys., 38, 1115–1122, https://doi.org/10.5194/angeo-38-1115-2020, https://doi.org/10.5194/angeo-38-1115-2020, 2020
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In this paper, the receiver differential code bias (DCB) of BDS (BeiDou Navigation Satellite System) is estimated as the changing parameter within 1 d with epoch-by-epoch estimates. The intraday variability of receiver DCB is analyzed from 30 d of Multi-GNSS Experiment observations. In particular, the intraday stability of receiver DCB for the BDS-3 and BDS-2 observations is compared. The result shows that the intraday stability of BDS-3 receiver DCB is better than that of BDS-2 receiver DCB.
Telmo dos Santos Klipp, Adriano Petry, Jonas Rodrigues de Souza, Eurico Rodrigues de Paula, Gabriel Sandim Falcão, and Haroldo Fraga de Campos Velho
Ann. Geophys., 38, 347–357, https://doi.org/10.5194/angeo-38-347-2020, https://doi.org/10.5194/angeo-38-347-2020, 2020
Erik Schmölter, Jens Berdermann, Norbert Jakowski, and Christoph Jacobi
Ann. Geophys., 38, 149–162, https://doi.org/10.5194/angeo-38-149-2020, https://doi.org/10.5194/angeo-38-149-2020, 2020
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This study correlates ionospheric parameters with the integrated solar radiation for an analysis of the delayed ionospheric response in order to confirm previous studies on the delay and to further specify variations of the delay (seasonal and spatial). Results also indicate the dependence on the geomagnetic activity as well as on the 11-year solar cycle. The results are important for the understanding of ionospheric processes and could be used for the validation of ionospheric models.
Regia Pereira da Silva, Clezio Marcos Denardini, Manilo Soares Marques, Laysa Cristina Araujo Resende, Juliano Moro, Giorgio Arlan da Silva Picanço, Gilvan Luiz Borba, and Marcos Aurelio Ferreira dos Santos
Ann. Geophys., 38, 27–34, https://doi.org/10.5194/angeo-38-27-2020, https://doi.org/10.5194/angeo-38-27-2020, 2020
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In this work, we studied the HILDCAA disturbance time effects in the TEC by analyzing local time and seasonal dependences, and the influences of the solar wind velocity on a sample of 10 intervals occurring in 2015 and 2016. The main results show great variability in the hourly distribution of the dTEC between one interval and another, seasonal behavior different from that presented by geomagnetic storms, and interestingly no relation between the dTEC disturbances and the magnitude of the HSS.
Chih-Yu Chiang, Sunny Wing-Yee Tam, and Tzu-Fang Chang
Ann. Geophys., 36, 1471–1481, https://doi.org/10.5194/angeo-36-1471-2018, https://doi.org/10.5194/angeo-36-1471-2018, 2018
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Based on our simulation results, both temperature change and meridional neutral wind could cause the 630.0 nm nightglow intensity to vary, while the latter is more effective. An unexpected aspect of the results is the non-monotonic dependence of the emission rate on temperature, featuring a turning point as the temperature changes. Our findings of these turning temperature tendencies can guide future modeling attempts to match the observed nightglow brightness intensities.
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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...