Articles | Volume 43, issue 1
https://doi.org/10.5194/angeo-43-55-2025
© 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-43-55-2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Regular paper
| 
15 Jan 2025
Regular paper |
| 15 Jan 2025
| 15 Jan 2025
Investigation of the October effect in very low-frequency (VLF) signals
Marc Hansen
CORRESPONDING AUTHOR
Institute for Solar-Terrestrial Physics, German Aerospace Center (DLR), Germany
Daniela Banyś
Institute for Solar-Terrestrial Physics, German Aerospace Center (DLR), Germany
Mark Clilverd
British Antarctic Survey (UKRI-NERC), Cambridge, UK
David Wenzel
Institute for Solar-Terrestrial Physics, German Aerospace Center (DLR), Germany
Tero Raita
Sodankylä Geophysical Observatory, University of Oulu, Oulu, Finland
Mohammed Mainul Hoque
Institute for Solar-Terrestrial Physics, German Aerospace Center (DLR), Germany
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Roman Leonhardt, Benoit Heumez, Tero Raita, and Jan Reda
EGUsphere, https://doi.org/10.5194/egusphere-2025-2553, https://doi.org/10.5194/egusphere-2025-2553, 2025
This preprint is open for discussion and under review for Geoscientific Instrumentation, Methods and Data Systems (GI).
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IMBOT , the INTERMAGNET ROBOT, has been developed to perform automated routines to convert and evaluate data submission to INTERMAGNET, a global network of geomagnetic observatories. IMBOT makes data review faster and more reliable, providing high-quality data for the geomagnetic community.
Mizuki Fukizawa, Yoshimasa Tanaka, Yasunobu Ogawa, Keisuke Hosokawa, Tero Raita, and Kirsti Kauristie
Ann. Geophys., 41, 511–528, https://doi.org/10.5194/angeo-41-511-2023, https://doi.org/10.5194/angeo-41-511-2023, 2023
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We use computed tomography to reconstruct the three-dimensional distributions of the Hall and Pedersen conductivities of pulsating auroras, a key research target for understanding the magnetosphere–ionosphere coupling process. It is suggested that the high-energy electron precipitation associated with pulsating auroras may have a greater impact on the closure of field-aligned currents in the ionosphere than has been previously reported.
Mizuki Fukizawa, Takeshi Sakanoi, Yoshimasa Tanaka, Yasunobu Ogawa, Keisuke Hosokawa, Björn Gustavsson, Kirsti Kauristie, Alexander Kozlovsky, Tero Raita, Urban Brändström, and Tima Sergienko
Ann. Geophys., 40, 475–484, https://doi.org/10.5194/angeo-40-475-2022, https://doi.org/10.5194/angeo-40-475-2022, 2022
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The pulsating auroral generation mechanism has been investigated by observing precipitating electrons using rockets or satellites. However, it is difficult for such observations to distinguish temporal changes from spatial ones. In this study, we reconstructed the horizontal 2-D distribution of precipitating electrons using only auroral images. The 3-D aurora structure was also reconstructed. We found that there were both spatial and temporal changes in the precipitating electron energy.
Irina Mironova, Miriam Sinnhuber, Galina Bazilevskaya, Mark Clilverd, Bernd Funke, Vladimir Makhmutov, Eugene Rozanov, Michelle L. Santee, Timofei Sukhodolov, and Thomas Ulich
Atmos. Chem. Phys., 22, 6703–6716, https://doi.org/10.5194/acp-22-6703-2022, https://doi.org/10.5194/acp-22-6703-2022, 2022
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From balloon measurements, we detected unprecedented, extremely powerful, electron precipitation over the middle latitudes. The robustness of this event is confirmed by satellite observations of electron fluxes and chemical composition, as well as by ground-based observations of the radio signal propagation. The applied chemistry–climate model shows the almost complete destruction of ozone in the mesosphere over the region where high-energy electrons were observed.
David A. Newnham, Mark A. Clilverd, William D. J. Clark, Michael Kosch, Pekka T. Verronen, and Alan E. E. Rogers
Atmos. Meas. Tech., 15, 2361–2376, https://doi.org/10.5194/amt-15-2361-2022, https://doi.org/10.5194/amt-15-2361-2022, 2022
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Ozone (O3) is an important trace gas in the mesosphere and lower thermosphere (MLT), affecting heating rates and chemistry. O3 profiles measured by the Ny-Ålesund Ozone in the Mesosphere Instrument agree with Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) for winter night-time, but autumn twilight SABER abundances are up to 50 % higher. O3 abundances in the MLT from two different SABER channels also show significant differences for both autumn twilight and summer daytime.
Minna Palmroth, Maxime Grandin, Theodoros Sarris, Eelco Doornbos, Stelios Tourgaidis, Anita Aikio, Stephan Buchert, Mark A. Clilverd, Iannis Dandouras, Roderick Heelis, Alex Hoffmann, Nickolay Ivchenko, Guram Kervalishvili, David J. Knudsen, Anna Kotova, Han-Li Liu, David M. Malaspina, Günther March, Aurélie Marchaudon, Octav Marghitu, Tomoko Matsuo, Wojciech J. Miloch, Therese Moretto-Jørgensen, Dimitris Mpaloukidis, Nils Olsen, Konstantinos Papadakis, Robert Pfaff, Panagiotis Pirnaris, Christian Siemes, Claudia Stolle, Jonas Suni, Jose van den IJssel, Pekka T. Verronen, Pieter Visser, and Masatoshi Yamauchi
Ann. Geophys., 39, 189–237, https://doi.org/10.5194/angeo-39-189-2021, https://doi.org/10.5194/angeo-39-189-2021, 2021
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This is a review paper that summarises the current understanding of the lower thermosphere–ionosphere (LTI) in terms of measurements and modelling. The LTI is the transition region between space and the atmosphere and as such of tremendous importance to both the domains of space and atmosphere. The paper also serves as the background for European Space Agency Earth Explorer 10 candidate mission Daedalus.
Xiaochen Gou, Lei Li, Yiteng Zhang, Bin Zhou, Yongyong Feng, Bingjun Cheng, Tero Raita, Ji Liu, Zeren Zhima, and Xuhui Shen
Ann. Geophys., 38, 775–787, https://doi.org/10.5194/angeo-38-775-2020, https://doi.org/10.5194/angeo-38-775-2020, 2020
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The CSES observed ionospheric Pc1 waves near the wave injection regions in conjugate hemispheres during the recovery phase of the geomagnetic storm on 27 August 2018. The Pc1s were found to be Alfvén waves with mixed polarisation propagating along background magnetic lines in the ionosphere. We suggest that the possible sources of Pc1 are EMIC waves generated near the plasmapause by the outward expansion of the plasmasphere into the ring current during the recovery phase of geomagnetic storms.
Theodoros E. Sarris, Elsayed R. Talaat, Minna Palmroth, Iannis Dandouras, Errico Armandillo, Guram Kervalishvili, Stephan Buchert, Stylianos Tourgaidis, David M. Malaspina, Allison N. Jaynes, Nikolaos Paschalidis, John Sample, Jasper Halekas, Eelco Doornbos, Vaios Lappas, Therese Moretto Jørgensen, Claudia Stolle, Mark Clilverd, Qian Wu, Ingmar Sandberg, Panagiotis Pirnaris, and Anita Aikio
Geosci. Instrum. Method. Data Syst., 9, 153–191, https://doi.org/10.5194/gi-9-153-2020, https://doi.org/10.5194/gi-9-153-2020, 2020
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Daedalus aims to measure the largely unexplored area between Eart's atmosphere and space, the Earth's
ignorosphere. Here, intriguing and complex processes govern the deposition and transport of energy. The aim is to quantify this energy by measuring effects caused by electrodynamic processes in this region. The concept is based on a mother satellite that carries a suite of instruments, along with smaller satellites carrying a subset of instruments that are released into the atmosphere.
Emilia Kilpua, Liisa Juusola, Maxime Grandin, Antti Kero, Stepan Dubyagin, Noora Partamies, Adnane Osmane, Harriet George, Milla Kalliokoski, Tero Raita, Timo Asikainen, and Minna Palmroth
Ann. Geophys., 38, 557–574, https://doi.org/10.5194/angeo-38-557-2020, https://doi.org/10.5194/angeo-38-557-2020, 2020
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Coronal mass ejection sheaths and ejecta are key drivers of significant space weather storms, and they cause dramatic changes in radiation belt electron fluxes. Differences in precipitation of high-energy electrons from the belts to the upper atmosphere are thus expected. We investigate here differences in sheath- and ejecta-induced precipitation using the Finnish riometer (relative ionospheric opacity meter) chain.
David A. Newnham, Mark A. Clilverd, Michael Kosch, Annika Seppälä, and Pekka T. Verronen
Atmos. Meas. Tech., 12, 1375–1392, https://doi.org/10.5194/amt-12-1375-2019, https://doi.org/10.5194/amt-12-1375-2019, 2019
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A simulation study has been carried out to investigate the potential for observing ozone and hydroxyl radical abundances in the mesosphere and lower thermosphere using ground-based passive microwave radiometry. In the polar middle atmosphere these chemical species respond strongly to geomagnetic activity associated with space weather. The results show that measuring diurnal variations in ozone and hydroxyl from high-latitude Northern Hemisphere and Antarctic locations would be possible.
Katja Matthes, Bernd Funke, Monika E. Andersson, Luke Barnard, Jürg Beer, Paul Charbonneau, Mark A. Clilverd, Thierry Dudok de Wit, Margit Haberreiter, Aaron Hendry, Charles H. Jackman, Matthieu Kretzschmar, Tim Kruschke, Markus Kunze, Ulrike Langematz, Daniel R. Marsh, Amanda C. Maycock, Stergios Misios, Craig J. Rodger, Adam A. Scaife, Annika Seppälä, Ming Shangguan, Miriam Sinnhuber, Kleareti Tourpali, Ilya Usoskin, Max van de Kamp, Pekka T. Verronen, and Stefan Versick
Geosci. Model Dev., 10, 2247–2302, https://doi.org/10.5194/gmd-10-2247-2017, https://doi.org/10.5194/gmd-10-2247-2017, 2017
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The solar forcing dataset for climate model experiments performed for the upcoming IPCC report is described. This dataset provides the radiative and particle input of solar variability on a daily basis from 1850 through to 2300. With this dataset a better representation of natural climate variability with respect to the output of the Sun is provided which provides the most sophisticated and comprehensive respresentation of solar variability that has been used in climate model simulations so far.
Tatjana Gerzen, Volker Wilken, David Minkwitz, Mainul M. Hoque, and Stefan Schlüter
Ann. Geophys., 35, 203–215, https://doi.org/10.5194/angeo-35-203-2017, https://doi.org/10.5194/angeo-35-203-2017, 2017
David Minkwitz, Karl Gerald van den Boogaart, Tatjana Gerzen, Mainul Hoque, and Manuel Hernández-Pajares
Ann. Geophys., 34, 999–1010, https://doi.org/10.5194/angeo-34-999-2016, https://doi.org/10.5194/angeo-34-999-2016, 2016
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We extend the kriging of the ionospheric electron density with slant total electron content (STEC) measurements based on a spatial covariance to kriging with a spatial–temporal covariance and develop a novel tomography approach by gradient-enhanced kriging assimilating STEC and F2 layer characteristics. The methods are cross-validated with independent measurements and point out the potential compensation for the often observed bias in the estimation of the F2 layer peak height.
Tamás Kovács, John M. C. Plane, Wuhu Feng, Tibor Nagy, Martyn P. Chipperfield, Pekka T. Verronen, Monika E. Andersson, David A. Newnham, Mark A. Clilverd, and Daniel R. Marsh
Geosci. Model Dev., 9, 3123–3136, https://doi.org/10.5194/gmd-9-3123-2016, https://doi.org/10.5194/gmd-9-3123-2016, 2016
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This study was completed on D-region atmospheric model development. The sophisticated 3-D Whole Atmosphere Community Climate Model (WACCM) and the 1-D Sodynkalä Ion and Neutral Chemistry Model (SIC) were combined in order to provide a detailed, accurate model (WACCM-SIC) that considers the processes taking place in solar proton events. The original SIC model was reduced by mechanism reduction, which provided an accurate sub-mechanism (rSIC, WACCM-rSIC) of the original model.
Johannes Norberg, Lassi Roininen, Antti Kero, Tero Raita, Thomas Ulich, Markku Markkanen, Liisa Juusola, and Kirsti Kauristie
Geosci. Instrum. Method. Data Syst., 5, 263–270, https://doi.org/10.5194/gi-5-263-2016, https://doi.org/10.5194/gi-5-263-2016, 2016
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The Sodankylä Geophysical Observatory has been producing ionospheric tomography data since 2003. Based on these data, one solar cycle of ionospheric vertical total electron content (VTEC) estimates is constructed. The measurements are compared against the IRI-2012 model, F10.7 solar flux index and sunspot number data. Qualitatively the tomographic VTEC estimate corresponds to reference data very well, but the IRI-2012 model are on average 40 % higher of that of the tomographic results.
Kirsti Kauristie, Minna Myllys, Noora Partamies, Ari Viljanen, Pyry Peitso, Liisa Juusola, Shabana Ahmadzai, Vikramjit Singh, Ralf Keil, Unai Martinez, Alexej Luginin, Alexi Glover, Vicente Navarro, and Tero Raita
Geosci. Instrum. Method. Data Syst., 5, 253–262, https://doi.org/10.5194/gi-5-253-2016, https://doi.org/10.5194/gi-5-253-2016, 2016
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We use the connection between auroras and geomagnetic field variations in a concept for a Regional Auroral Forecast (RAF) service. RAF is based on statistical relationships between alerts by the NOAA Space Weather Prediction Center and magnetic time derivatives measured by five MIRACLE magnetometer stations located in the surroundings of the Sodankylä research station. As an improvement to previous similar services RAF yields knowledge on typical auroral storm durations at different latitudes.
D. Minkwitz, K. G. van den Boogaart, T. Gerzen, and M. Hoque
Ann. Geophys., 33, 1071–1079, https://doi.org/10.5194/angeo-33-1071-2015, https://doi.org/10.5194/angeo-33-1071-2015, 2015
M. E. Andersson, P. T. Verronen, C. J. Rodger, M. A. Clilverd, and S. Wang
Atmos. Chem. Phys., 14, 1095–1105, https://doi.org/10.5194/acp-14-1095-2014, https://doi.org/10.5194/acp-14-1095-2014, 2014
Related subject area
Subject: Earth's ionosphere & aeronomy | Keywords: Ionospheric disturbances
Observations of ionospheric disturbances associated with the 2020 Beirut explosion by Defense Meteorological Satellite Program and ground-based ionosondes
Effects of the super-powerful tropospheric western Pacific phenomenon of September–October 2018 on the ionosphere over China: results from oblique sounding
Ionospheric effects of the 5–6 January 2019 eclipse over the People's Republic of China: results from oblique sounding
Study of the equatorial and low-latitude total electron content response to plasma bubbles during solar cycle 24–25 over the Brazilian region using a Disturbance Ionosphere indeX
Diagnostic study of geomagnetic storm-induced ionospheric changes over very low-frequency signal propagation paths in the mid-latitude D region
Complex analysis of the ionosphere variations during the geomagnetic storm at 20 January 2010 performed by Detection of Ionosphere Anomalies (DIA) software and DEMETER satellite data
Dynamic processes in the magnetic field and in the ionosphere during the 30 August–2 September 2019 geospace storm: influence on high frequency radio wave characteristics
Tomographic imaging of a large-scale travelling ionospheric disturbance during the Halloween storm of 2003
Ionospheric anomalies associated with the Mw 7.3 Iran–Iraq border earthquake and a moderate magnetic storm
Model of the propagation of very low-frequency beams in the Earth–ionosphere waveguide: principles of the tensor impedance method in multi-layered gyrotropic waveguides
Strong influence of solar X-ray flares on low-frequency electromagnetic signals in middle latitudes
A case study of the large-scale traveling ionospheric disturbances in the eastern Asian sector during the 2015 St. Patrick's Day geomagnetic storm
Geomagnetic conjugate observations of ionospheric disturbances in response to a North Korean underground nuclear explosion on 3 September 2017
Emergence of a localized total electron content enhancement during the severe geomagnetic storm of 8 September 2017
Mitigation of ionospheric signatures in Swarm GPS gravity field estimation using weighting strategies
PPP-based Swarm kinematic orbit determination
Impact of magnetic storms on the global TEC distribution
Rezy Pradipta and Pei-Chen Lai
Ann. Geophys., 42, 301–312, https://doi.org/10.5194/angeo-42-301-2024, https://doi.org/10.5194/angeo-42-301-2024, 2024
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A large explosion released a significant amount of energy into the Earth's upper atmosphere in Beirut on 4 Aug 2020, generating traveling ionospheric disturbances (TIDs). These TIDs were observed in previous work using GPS total electron content measurements around Beirut. Here, we used measurements from the Defense Meteorological Satellite Program and ionosondes in the Mediterranean to show that the TIDs from the Beirut explosion were able to reach greater distances than previously reported.
Leonid F. Chernogor, Kostiantyn P. Garmash, Qiang Guo, Victor T. Rozumenko, and Yu Zheng
Ann. Geophys., 41, 173–195, https://doi.org/10.5194/angeo-41-173-2023, https://doi.org/10.5194/angeo-41-173-2023, 2023
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The receiver at the Harbin Engineering University and eight surrounding HF broadcast stations ~1000 km observed the response in the ionospheric electron density to the activity of Typhoon Kong-rey (30 September–6 October 2018). On 1–2 and 5–6 October 2018, the 20 min to 60 min period quasi-sinusoidal variations in the electron density with an amplitude of 0.4 % to 6 % resulted in 0.1 Hz to 0.5 Hz amplitude Doppler shift variations, a factor of 2–3 increase as compared to a quiet time reference.
Leonid F. Chernogor, Kostyantyn P. Garmash, Qiang Guo, Victor T. Rozumenko, and Yu Zheng
Ann. Geophys., 40, 585–603, https://doi.org/10.5194/angeo-40-585-2022, https://doi.org/10.5194/angeo-40-585-2022, 2022
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The solar eclipse of 5–6 January 2019 perturbed the ionospheric electron density, N, observed with the receiver at the Harbin Engineering University and 14 HF broadcasting stations ~1 000 km around. It was accompanied by ±1.5 Hz Doppler-spectrum broadening, ±0.5 Hz Doppler shift, fD, variations, 15 min period variations in fD caused by 1.6–2.4 % perturbations in N, and period changes of 4–5 min in fD caused by 0.2–0.3 % disturbances in N. The decrease in N attained ~15 % (vs. modeled 16 %).
Giorgio Arlan Silva Picanço, Clezio Marcos Denardini, Paulo Alexandre Bronzato Nogueira, Laysa Cristina Araujo Resende, Carolina Sousa Carmo, Sony Su Chen, Paulo França Barbosa-Neto, and Esmeralda Romero-Hernandez
Ann. Geophys., 40, 503–517, https://doi.org/10.5194/angeo-40-503-2022, https://doi.org/10.5194/angeo-40-503-2022, 2022
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In this work, we use the Disturbance Ionosphere indeX (DIX) to study equatorial plasma bubble (EPB) events over the Brazilian equatorial and low latitudes. Our results showed that the DIX detected EPB disturbances in terms of their intensity and occurrence times. Therefore, these responses agreed with the ionosphere behavior before, during, and after the studied EPBs. Finally, these disturbances tended to be higher (lower) in high (low) solar activity.
Victor U. J. Nwankwo, William Denig, Sandip K. Chakrabarti, Olugbenga Ogunmodimu, Muyiwa P. Ajakaiye, Johnson O. Fatokun, Paul I. Anekwe, Omodara E. Obisesan, Olufemi E. Oyanameh, and Oluwaseun V. Fatoye
Ann. Geophys., 40, 433–461, https://doi.org/10.5194/angeo-40-433-2022, https://doi.org/10.5194/angeo-40-433-2022, 2022
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We combined the observed diurnal VLF amplitude variation in the D region with standard measurements of the E and F regions to perform a diagnostic investigation of coupled geomagnetic storm effects in order to understand the observed storm-induced variations in VLF narrowband based on state and responses of the ionosphere. The dayside VLF amplitude showed a tendency for attenuation following geomagnetic storms, and the h’E and h’F variations confirmed strong storm response over the signal paths.
Anatoliy Lozbin, Viktor Fedun, and Olga Kryakunova
Ann. Geophys., 40, 55–65, https://doi.org/10.5194/angeo-40-55-2022, https://doi.org/10.5194/angeo-40-55-2022, 2022
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Detection of Ionosphere Anomalies (DIA) for detection, identification, and analysis of ionosphere anomalies from satellite spectrograms and time series row data from instruments onboard the DEMETER satellite was designed. Using this software, the analyses of ionosphere parameter variations caused by various factors are provided. The scientific data processing and visualization technologies used in the development of DIA can be used in the creation of software for other scientific space missions.
Yiyang Luo, Leonid Chernogor, Kostiantyn Garmash, Qiang Guo, Victor Rozumenko, and Yu Zheng
Ann. Geophys., 39, 657–685, https://doi.org/10.5194/angeo-39-657-2021, https://doi.org/10.5194/angeo-39-657-2021, 2021
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The 30 August–2 September 2019 geospace storm and its influence on the characteristics of high frequency radio waves over the People's Republic of China have been analyzed. The geospace storm was weak, the magnetic storm was moderate, and the ionospheric storm was moderate to strongly negative, which manifested itself by the reduction in the ionospheric F-region electron density. Appreciable disturbances were also observed to occur in the ionospheric E-region and possibly in the Es layer.
Karl Bolmgren, Cathryn Mitchell, Talini Pinto Jayawardena, Gary Bust, Jon Bruno, and Elizabeth Mitchell
Ann. Geophys., 38, 1149–1157, https://doi.org/10.5194/angeo-38-1149-2020, https://doi.org/10.5194/angeo-38-1149-2020, 2020
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Travelling ionospheric disturbances behave like waves in the ionosphere, the ionised upper part of the atmosphere. In this study, we use an ionospheric tomography technique to map the electron content as affected by the passage of a large-scale travelling ionospheric disturbance launched during the largest geomagnetic storm observed by modern instruments. This is the first such imaging using this software and to the authors' knowledge the first study of this travelling ionospheric disturbance.
Erman Şentürk, Samed Inyurt, and İbrahim Sertçelik
Ann. Geophys., 38, 1031–1043, https://doi.org/10.5194/angeo-38-1031-2020, https://doi.org/10.5194/angeo-38-1031-2020, 2020
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The analysis of unexpected ionospheric phases before large earthquakes is one of the cutting-edge issues in earthquake prediction studies. Ionospheric TEC data were analyzed by short-time Fourier transform and a classic running median to detect abnormalities before the Mw 7.3 Iran–Iraq earthquake on November 12, 2017. The results showed clear positive anomalies 8–9 d before the earthquake as an earthquake precursor due to quiet space weather, local dispersion, and proximity to the epicenter.
Yuriy Rapoport, Vladimir Grimalsky, Viktor Fedun, Oleksiy Agapitov, John Bonnell, Asen Grytsai, Gennadi Milinevsky, Alex Liashchuk, Alexander Rozhnoi, Maria Solovieva, and Andrey Gulin
Ann. Geophys., 38, 207–230, https://doi.org/10.5194/angeo-38-207-2020, https://doi.org/10.5194/angeo-38-207-2020, 2020
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The paper analytically and numerically treats the new theoretical basis for ground-based and satellite monitoring of the most powerful processes in the lower atmosphere and Earth (hurricanes, earthquakes, etc.), solar-wind magnetosphere (magnetic storms) and ionosphere (lightning discharges, thunderstorms, etc.). This can be provided by the determination of phases and amplitudes of radio waves in the Earth and ionosphere. In perspective, damage from the natural disasters can be decreased.
Alexander Rozhnoi, Maria Solovieva, Viktor Fedun, Peter Gallagher, Joseph McCauley, Mohammed Y. Boudjada, Sergiy Shelyag, and Hans U. Eichelberger
Ann. Geophys., 37, 843–850, https://doi.org/10.5194/angeo-37-843-2019, https://doi.org/10.5194/angeo-37-843-2019, 2019
Jing Liu, Dong-He Zhang, Anthea J. Coster, Shun-Rong Zhang, Guan-Yi Ma, Yong-Qiang Hao, and Zuo Xiao
Ann. Geophys., 37, 673–687, https://doi.org/10.5194/angeo-37-673-2019, https://doi.org/10.5194/angeo-37-673-2019, 2019
Yi Liu, Chen Zhou, Qiong Tang, Guanyi Chen, and Zhengyu Zhao
Ann. Geophys., 37, 337–345, https://doi.org/10.5194/angeo-37-337-2019, https://doi.org/10.5194/angeo-37-337-2019, 2019
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Underground nuclear explosion (UNE) can produce ionospheric disturbances through a lithosphere–atmosphere–ionosphere coupling mechanism, which is very similar with earthquakes. By using the total electron content observations and Swarm ionospheric current data, we have investigated the geomagnetic conjugate ionospheric disturbances. We proposed that the electric field generated during the UNE test can be an important mechanism for ionospheric disturbance.
Carlos Sotomayor-Beltran and Laberiano Andrade-Arenas
Ann. Geophys., 37, 153–161, https://doi.org/10.5194/angeo-37-153-2019, https://doi.org/10.5194/angeo-37-153-2019, 2019
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A localized total electron content enhancement (LTE) was observed as a product of the geomagnetic storm that happened on 8 September 2017. This result was unexpected because it was located south of the equatorial ionization anomaly (EIA). The origin of the enhancement of the TEC in the EIA is very likely due to the super-fountain effect. On the other hand, the LTE is suggested to be produced by the contribution of the super-fountain effect along with traveling ionospheric disturbances.
Lucas Schreiter, Daniel Arnold, Veerle Sterken, and Adrian Jäggi
Ann. Geophys., 37, 111–127, https://doi.org/10.5194/angeo-37-111-2019, https://doi.org/10.5194/angeo-37-111-2019, 2019
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Comparing Swarm GPS-only gravity fields to the ultra-precise GRACE K-Band gravity field schematic errors occurs around the geomagnetic equator. Due to the end of the GRACE mission, and the gap to the GRACE-FO mission, only Swarm can provide a continuous time series of gravity fields. We present different and assess different approaches to remove the schematic errors and thus improve the quality of the Swarm gravity fields.
Le Ren and Steffen Schön
Ann. Geophys., 36, 1227–1241, https://doi.org/10.5194/angeo-36-1227-2018, https://doi.org/10.5194/angeo-36-1227-2018, 2018
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In this contribution, we analyse the performance of the Swarm onboard GPS receiver and present the approach for determination of the IfE Swarm kinematic orbit with PPP. The differences between our kinematic orbits and ESA reduced-dynamic orbits are at 1.5 cm, 1.5 cm and 2.5 cm level in along-track, cross-track and radial directions, respectively. A comparison with SLR underlines an accuracy of the kinematic orbits of 3–4 cm.
Donat V. Blagoveshchensky, Olga A. Maltseva, and Maria A. Sergeeva
Ann. Geophys., 36, 1057–1071, https://doi.org/10.5194/angeo-36-1057-2018, https://doi.org/10.5194/angeo-36-1057-2018, 2018
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Short summary
The amplitude of subionospheric very low-frequency (VLF) radio signals does not show a symmetrical behavior over the year, which would be expected from its dependency on the solar position. The VLF amplitude rather shows a distinctive sharp decrease around October, which is hence called the "October effect". This study is the first to systematically investigate this October effect, which shows a clear latitudinal dependency.
The amplitude of subionospheric very low-frequency (VLF) radio signals does not show a...
