Articles | Volume 41, issue 1
https://doi.org/10.5194/angeo-41-13-2023
© Author(s) 2023. 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-41-13-2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Regular paper
| 
11 Jan 2023
Regular paper |
| 11 Jan 2023
| 11 Jan 2023
Drivers of rapid geomagnetic variations at high latitudes
Finnish Meteorological Institute, Helsinki, Finland
Ari Viljanen
Finnish Meteorological Institute, Helsinki, Finland
Andrew P. Dimmock
Swedish Institute of Space Physics, Uppsala, Sweden
Mirjam Kellinsalmi
Finnish Meteorological Institute, Helsinki, Finland
Audrey Schillings
Department of Physics, Umeå University, Umeå, Sweden
James M. Weygand
Department of Earth, Planetary, and Space Sciences, University of California Los Angeles, Los Angeles, CA, USA
Related authors
Liisa Juusola, Heikki Vanhamäki, Elena Marshalko, Mikhail Kruglyakov, and Ari Viljanen
EGUsphere, https://doi.org/10.5194/egusphere-2024-2831, https://doi.org/10.5194/egusphere-2024-2831, 2024
Short summary
Short summary
Interaction between the magnetic field of the rapidly varying electric currents in space and the conducting ground produces an electric field at the Earth's surface. This geoelectric field drives geomagnetically induced currents in technological conductor networks, which can affect the performance of critical ground infrastructure such as electric power transmission grids. We have developed a new method suitable for monitoring the geoelectric field based on ground magnetic field observations.
Urs Ganse, Yann Pfau-Kempf, Hongyang Zhou, Liisa Juusola, Abiyot Workayehu, Fasil Kebede, Konstantinos Papadakis, Maxime Grandin, Markku Alho, Markus Battarbee, Maxime Dubart, Leo Kotipalo, Arnaud Lalagüe, Jonas Suni, Konstantinos Horaites, and Minna Palmroth
Geosci. Model Dev. Discuss., https://doi.org/10.5194/gmd-2024-101, https://doi.org/10.5194/gmd-2024-101, 2024
Revised manuscript accepted for GMD
Short summary
Short summary
Vlasiator is a kinetic space-plasma model that simulates the behaviour of plasma, solar wind and magnetic fields in near-Earth space. So far, these simulations had been run without any interaction wtih the ionosphere, the uppermost layer of Earth's atmosphere. In this manuscript, we present the new methods that add an ionospheric electrodynamics model to Vlasiator, coupling it with the existing methods and presenting new simulation results of how space Plasma and Earth's ionosphere interact.
Noora Partamies, Bas Dol, Vincent Teissier, Liisa Juusola, Mikko Syrjäsuo, and Hjalmar Mulders
Ann. Geophys., 42, 103–115, https://doi.org/10.5194/angeo-42-103-2024, https://doi.org/10.5194/angeo-42-103-2024, 2024
Short summary
Short summary
Auroral imaging produces large amounts of image data that can no longer be analyzed by visual inspection. Thus, every step towards automatic analysis tools is crucial. Previously supervised learning methods have been used in auroral physics, with a human expert providing ground truth. However, this ground truth is debatable. We present an unsupervised learning method, which shows promising results in detecting auroral breakups in the all-sky image data.
Liisa Juusola, Ari Viljanen, Noora Partamies, Heikki Vanhamäki, Mirjam Kellinsalmi, and Simon Walker
Ann. Geophys., 41, 483–510, https://doi.org/10.5194/angeo-41-483-2023, https://doi.org/10.5194/angeo-41-483-2023, 2023
Short summary
Short summary
At times when auroras erupt on the sky, the magnetic field surrounding the Earth undergoes rapid changes. On the ground, these changes can induce harmful electric currents in technological conductor networks, such as powerlines. We have used magnetic field observations from northern Europe during 28 such events and found consistent behavior that can help to understand, and thus predict, the processes that drive auroras and geomagnetically induced currents.
Mirjam Kellinsalmi, Ari Viljanen, Liisa Juusola, and Sebastian Käki
Ann. Geophys., 40, 545–562, https://doi.org/10.5194/angeo-40-545-2022, https://doi.org/10.5194/angeo-40-545-2022, 2022
Short summary
Short summary
Eruptions from the Sun can pose a hazard to Earth's power grids via, e.g., geomagnetically induced currents (GICs). 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 2 min. 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.
Sebastian Käki, Ari Viljanen, Liisa Juusola, and Kirsti Kauristie
Ann. Geophys., 40, 107–119, https://doi.org/10.5194/angeo-40-107-2022, https://doi.org/10.5194/angeo-40-107-2022, 2022
Short summary
Short summary
During auroral substorms, the ionospheric electric currents change rapidly, and a large amount of energy is dissipated. We combine ionospheric current data derived from the Swarm satellite mission with the substorm database from the SuperMAG ground magnetometer network. We obtain statistics of the strength and location of the currents relative to the substorm onset. Our results show that low-earth orbit satellites give a coherent picture of the main features in the substorm current system.
Liisa Juusola, Heikki Vanhamäki, Ari Viljanen, and Maxim Smirnov
Ann. Geophys., 38, 983–998, https://doi.org/10.5194/angeo-38-983-2020, https://doi.org/10.5194/angeo-38-983-2020, 2020
Short summary
Short summary
Rapid variations of the magnetic field measured on the ground can be used to estimate space weather risks to power grids, but forecasting the variations remains a challenge. We show that part of this problem stems from the fact that, in addition to electric currents in space, the magnetic field variations are strongly affected by underground electric currents. We suggest that separating the measured field into its space and underground parts could improve our understanding of space weather.
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
Short summary
Short summary
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.
Liisa Juusola, Sanni Hoilijoki, Yann Pfau-Kempf, Urs Ganse, Riku Jarvinen, Markus Battarbee, Emilia Kilpua, Lucile Turc, and Minna Palmroth
Ann. Geophys., 36, 1183–1199, https://doi.org/10.5194/angeo-36-1183-2018, https://doi.org/10.5194/angeo-36-1183-2018, 2018
Short summary
Short summary
The solar wind interacts with the Earth’s magnetic field, forming a magnetosphere. On the night side solar wind stretches the magnetosphere into a long tail. A process called magnetic reconnection opens the magnetic field lines and reconnects them, accelerating particles to high energies. We study this in the magnetotail using a numerical simulation model of the Earth’s magnetosphere. We study the motion of the points where field lines reconnect and the fast flows driven by this process.
Liisa Juusola, Yann Pfau-Kempf, Urs Ganse, Markus Battarbee, Thiago Brito, Maxime Grandin, Lucile Turc, and Minna Palmroth
Ann. Geophys., 36, 1027–1035, https://doi.org/10.5194/angeo-36-1027-2018, https://doi.org/10.5194/angeo-36-1027-2018, 2018
Short summary
Short summary
The Earth's magnetic field is shaped by the solar wind. On the dayside the field is compressed and on the nightside it is stretched as a long tail. The tail has been observed to occasionally undergo flapping motions, but the origin of these motions is not understood. We study the flapping using a numerical simulation of the near-Earth space. We present a possible explanation for how the flapping could be initiated by a passing disturbance and then maintained as a standing wave.
Minna Palmroth, Sanni Hoilijoki, Liisa Juusola, Tuija I. Pulkkinen, Heli Hietala, Yann Pfau-Kempf, Urs Ganse, Sebastian von Alfthan, Rami Vainio, and Michael Hesse
Ann. Geophys., 35, 1269–1274, https://doi.org/10.5194/angeo-35-1269-2017, https://doi.org/10.5194/angeo-35-1269-2017, 2017
Short summary
Short summary
Much like solar flares, substorms occurring within the Earth's magnetic domain are explosive events that cause vivid auroral displays. A decades-long debate exists to explain the substorm onset. We devise a simulation encompassing the entire near-Earth space and demonstrate that detailed modelling of magnetic reconnection explains the central substorm observations. Our results help to understand the unpredictable substorm process, which will significantly improve space weather forecasts.
Noora Partamies, James M. Weygand, and Liisa Juusola
Ann. Geophys., 35, 1069–1083, https://doi.org/10.5194/angeo-35-1069-2017, https://doi.org/10.5194/angeo-35-1069-2017, 2017
Short summary
Short summary
Large-scale undulations of the diffuse aurora boundary, auroral omega bands, have been studied based on 438 omega-like structures identified over Fennoscandian Lapland from 1996 to 2007. The omegas mainly occurred in the post-magnetic midnight sector, in the region between oppositely directed ionospheric field-aligned currents, and during substorm recovery phases. The omega bands were observed during substorms, which were more intense than the average substorm in the same region.
Yann Pfau-Kempf, Heli Hietala, Steve E. Milan, Liisa Juusola, Sanni Hoilijoki, Urs Ganse, Sebastian von Alfthan, and Minna Palmroth
Ann. Geophys., 34, 943–959, https://doi.org/10.5194/angeo-34-943-2016, https://doi.org/10.5194/angeo-34-943-2016, 2016
Short summary
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We have simulated the interaction of the solar wind – the charged particles and magnetic fields emitted by the Sun into space – with the magnetic field of the Earth. The solar wind flows supersonically and creates a shock when it encounters the obstacle formed by the geomagnetic field. We have identified a new chain of events which causes phenomena in the downstream region to eventually cause perturbations at the shock and even upstream. This is confirmed by ground and satellite observations.
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
Short summary
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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.
M. Myllys, N. Partamies, and L. Juusola
Ann. Geophys., 33, 573–581, https://doi.org/10.5194/angeo-33-573-2015, https://doi.org/10.5194/angeo-33-573-2015, 2015
K. Andréeová, L. Juusola, E. K. J. Kilpua, and H. E. J. Koskinen
Ann. Geophys., 32, 1293–1302, https://doi.org/10.5194/angeo-32-1293-2014, https://doi.org/10.5194/angeo-32-1293-2014, 2014
N. Partamies, L. Juusola, E. Tanskanen, and K. Kauristie
Ann. Geophys., 31, 349–358, https://doi.org/10.5194/angeo-31-349-2013, https://doi.org/10.5194/angeo-31-349-2013, 2013
Liisa Juusola, Heikki Vanhamäki, Elena Marshalko, Mikhail Kruglyakov, and Ari Viljanen
EGUsphere, https://doi.org/10.5194/egusphere-2024-2831, https://doi.org/10.5194/egusphere-2024-2831, 2024
Short summary
Short summary
Interaction between the magnetic field of the rapidly varying electric currents in space and the conducting ground produces an electric field at the Earth's surface. This geoelectric field drives geomagnetically induced currents in technological conductor networks, which can affect the performance of critical ground infrastructure such as electric power transmission grids. We have developed a new method suitable for monitoring the geoelectric field based on ground magnetic field observations.
Urs Ganse, Yann Pfau-Kempf, Hongyang Zhou, Liisa Juusola, Abiyot Workayehu, Fasil Kebede, Konstantinos Papadakis, Maxime Grandin, Markku Alho, Markus Battarbee, Maxime Dubart, Leo Kotipalo, Arnaud Lalagüe, Jonas Suni, Konstantinos Horaites, and Minna Palmroth
Geosci. Model Dev. Discuss., https://doi.org/10.5194/gmd-2024-101, https://doi.org/10.5194/gmd-2024-101, 2024
Revised manuscript accepted for GMD
Short summary
Short summary
Vlasiator is a kinetic space-plasma model that simulates the behaviour of plasma, solar wind and magnetic fields in near-Earth space. So far, these simulations had been run without any interaction wtih the ionosphere, the uppermost layer of Earth's atmosphere. In this manuscript, we present the new methods that add an ionospheric electrodynamics model to Vlasiator, coupling it with the existing methods and presenting new simulation results of how space Plasma and Earth's ionosphere interact.
Paul Prikryl, David R. Themens, Jaroslav Chum, Shibaji Chakraborty, Robert G. Gillies, and James M. Weygand
Ann. Geophys. Discuss., https://doi.org/10.5194/angeo-2024-6, https://doi.org/10.5194/angeo-2024-6, 2024
Preprint under review for ANGEO
Short summary
Short summary
Travelling ionospheric disturbances are plasma density fluctuations usually driven by atmospheric gravity waves in the neutral atmosphere. The aim of this study is to attribute multi-instrument observations of travelling ionospheric disturbances to gravity waves generated in the upper atmosphere at high latitudes or gravity waves generated by tropospheric weather systems at mid latitudes.
Noora Partamies, Bas Dol, Vincent Teissier, Liisa Juusola, Mikko Syrjäsuo, and Hjalmar Mulders
Ann. Geophys., 42, 103–115, https://doi.org/10.5194/angeo-42-103-2024, https://doi.org/10.5194/angeo-42-103-2024, 2024
Short summary
Short summary
Auroral imaging produces large amounts of image data that can no longer be analyzed by visual inspection. Thus, every step towards automatic analysis tools is crucial. Previously supervised learning methods have been used in auroral physics, with a human expert providing ground truth. However, this ground truth is debatable. We present an unsupervised learning method, which shows promising results in detecting auroral breakups in the all-sky image data.
Liisa Juusola, Ari Viljanen, Noora Partamies, Heikki Vanhamäki, Mirjam Kellinsalmi, and Simon Walker
Ann. Geophys., 41, 483–510, https://doi.org/10.5194/angeo-41-483-2023, https://doi.org/10.5194/angeo-41-483-2023, 2023
Short summary
Short summary
At times when auroras erupt on the sky, the magnetic field surrounding the Earth undergoes rapid changes. On the ground, these changes can induce harmful electric currents in technological conductor networks, such as powerlines. We have used magnetic field observations from northern Europe during 28 such events and found consistent behavior that can help to understand, and thus predict, the processes that drive auroras and geomagnetically induced currents.
Paul Prikryl, Robert G. Gillies, David R. Themens, James M. Weygand, Evan G. Thomas, and Shibaji Chakraborty
Ann. Geophys., 40, 619–639, https://doi.org/10.5194/angeo-40-619-2022, https://doi.org/10.5194/angeo-40-619-2022, 2022
Short summary
Short summary
The solar wind interaction with Earth’s magnetic field deposits energy into the upper portion of the atmosphere at high latitudes. The coupling process that modulates the ionospheric convection and intensity of ionospheric currents leads to formation of densely ionized patches convecting across the polar cap. The ionospheric currents launch traveling ionospheric disturbances (TIDs) propagating equatorward. The polar cap patches and TIDs are then observed by networks of radars and GPS receivers.
Mirjam Kellinsalmi, Ari Viljanen, Liisa Juusola, and Sebastian Käki
Ann. Geophys., 40, 545–562, https://doi.org/10.5194/angeo-40-545-2022, https://doi.org/10.5194/angeo-40-545-2022, 2022
Short summary
Short summary
Eruptions from the Sun can pose a hazard to Earth's power grids via, e.g., geomagnetically induced currents (GICs). 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 2 min. 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.
Homayon Aryan, Jacob Bortnik, Jinxing Li, James Michael Weygand, Xiangning Chu, and Vassilis Angelopoulos
Ann. Geophys., 40, 531–544, https://doi.org/10.5194/angeo-40-531-2022, https://doi.org/10.5194/angeo-40-531-2022, 2022
Short summary
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In this study, we use a multipoint analysis of conjugate magnetospheric and ionospheric observations to investigate the magnetospheric and ionospheric responses to fast flow bursts that are associated with different space weather conditions. The results show that ionospheric currents are connected to the magnetospheric flows for different space weather conditions. The connection is more apparent and global for flows that are associated with a geomagnetically active condition.
Sebastian Käki, Ari Viljanen, Liisa Juusola, and Kirsti Kauristie
Ann. Geophys., 40, 107–119, https://doi.org/10.5194/angeo-40-107-2022, https://doi.org/10.5194/angeo-40-107-2022, 2022
Short summary
Short summary
During auroral substorms, the ionospheric electric currents change rapidly, and a large amount of energy is dissipated. We combine ionospheric current data derived from the Swarm satellite mission with the substorm database from the SuperMAG ground magnetometer network. We obtain statistics of the strength and location of the currents relative to the substorm onset. Our results show that low-earth orbit satellites give a coherent picture of the main features in the substorm current system.
Lucile Turc, Vertti Tarvus, Andrew P. Dimmock, Markus Battarbee, Urs Ganse, Andreas Johlander, Maxime Grandin, Yann Pfau-Kempf, Maxime Dubart, and Minna Palmroth
Ann. Geophys., 38, 1045–1062, https://doi.org/10.5194/angeo-38-1045-2020, https://doi.org/10.5194/angeo-38-1045-2020, 2020
Short summary
Short summary
Using global computer simulations, we study properties of the magnetosheath, the region of near-Earth space where the stream of particles originating from the Sun, the solar wind, is slowed down and deflected around the Earth's magnetic field. One of our main findings is that even for idealised solar wind conditions as used in our model, the magnetosheath density shows large-scale spatial and temporal variation in the so-called quasi-parallel magnetosheath, causing varying levels of asymmetry.
Liisa Juusola, Heikki Vanhamäki, Ari Viljanen, and Maxim Smirnov
Ann. Geophys., 38, 983–998, https://doi.org/10.5194/angeo-38-983-2020, https://doi.org/10.5194/angeo-38-983-2020, 2020
Short summary
Short summary
Rapid variations of the magnetic field measured on the ground can be used to estimate space weather risks to power grids, but forecasting the variations remains a challenge. We show that part of this problem stems from the fact that, in addition to electric currents in space, the magnetic field variations are strongly affected by underground electric currents. We suggest that separating the measured field into its space and underground parts could improve our understanding of space weather.
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
Short summary
Short summary
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.
Antti Lakka, Tuija I. Pulkkinen, Andrew P. Dimmock, Emilia Kilpua, Matti Ala-Lahti, Ilja Honkonen, Minna Palmroth, and Osku Raukunen
Ann. Geophys., 37, 561–579, https://doi.org/10.5194/angeo-37-561-2019, https://doi.org/10.5194/angeo-37-561-2019, 2019
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We study how the Earth's space environment responds to two different amplitude interplanetary coronal mass ejection (ICME) events that occurred in 2012 and 2014 by using the GUMICS-4 global MHD model. We examine local and large-scale dynamics of the Earth's space environment and compare simulation results to in situ data. It is shown that during moderate driving simulation agrees well with the measurements; however, GMHD results should be interpreted cautiously during strong driving.
Liisa Juusola, Sanni Hoilijoki, Yann Pfau-Kempf, Urs Ganse, Riku Jarvinen, Markus Battarbee, Emilia Kilpua, Lucile Turc, and Minna Palmroth
Ann. Geophys., 36, 1183–1199, https://doi.org/10.5194/angeo-36-1183-2018, https://doi.org/10.5194/angeo-36-1183-2018, 2018
Short summary
Short summary
The solar wind interacts with the Earth’s magnetic field, forming a magnetosphere. On the night side solar wind stretches the magnetosphere into a long tail. A process called magnetic reconnection opens the magnetic field lines and reconnects them, accelerating particles to high energies. We study this in the magnetotail using a numerical simulation model of the Earth’s magnetosphere. We study the motion of the points where field lines reconnect and the fast flows driven by this process.
Xochitl Blanco-Cano, Markus Battarbee, Lucile Turc, Andrew P. Dimmock, Emilia K. J. Kilpua, Sanni Hoilijoki, Urs Ganse, David G. Sibeck, Paul A. Cassak, Robert C. Fear, Riku Jarvinen, Liisa Juusola, Yann Pfau-Kempf, Rami Vainio, and Minna Palmroth
Ann. Geophys., 36, 1081–1097, https://doi.org/10.5194/angeo-36-1081-2018, https://doi.org/10.5194/angeo-36-1081-2018, 2018
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We use the Vlasiator code to study the characteristics of transient structures that exist in the Earth's foreshock, i.e. upstream of the bow shock. The structures are cavitons and spontaneous hot flow anomalies (SHFAs). These transients can interact with the bow shock. We study the changes the shock suffers via this interaction. We also investigate ion distributions associated with the cavitons and SHFAs. A very important result is that the arrival of multiple SHFAs results in shock erosion.
Liisa Juusola, Yann Pfau-Kempf, Urs Ganse, Markus Battarbee, Thiago Brito, Maxime Grandin, Lucile Turc, and Minna Palmroth
Ann. Geophys., 36, 1027–1035, https://doi.org/10.5194/angeo-36-1027-2018, https://doi.org/10.5194/angeo-36-1027-2018, 2018
Short summary
Short summary
The Earth's magnetic field is shaped by the solar wind. On the dayside the field is compressed and on the nightside it is stretched as a long tail. The tail has been observed to occasionally undergo flapping motions, but the origin of these motions is not understood. We study the flapping using a numerical simulation of the near-Earth space. We present a possible explanation for how the flapping could be initiated by a passing disturbance and then maintained as a standing wave.
Matti M. Ala-Lahti, Emilia K. J. Kilpua, Andrew P. Dimmock, Adnane Osmane, Tuija Pulkkinen, and Jan Souček
Ann. Geophys., 36, 793–808, https://doi.org/10.5194/angeo-36-793-2018, https://doi.org/10.5194/angeo-36-793-2018, 2018
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We present a comprehensive statistical analysis of mirror mode waves and the properties of their plasma surroundings in sheath regions driven by interplanetary coronal mass ejection (ICME) to deepen our understanding of these geo-effective plasma environments. The results imply that mirror modes are common structures in ICME sheaths and occur almost exclusively as dip-like structures and in mirror stable stable plasma.
Minna Palmroth, Sanni Hoilijoki, Liisa Juusola, Tuija I. Pulkkinen, Heli Hietala, Yann Pfau-Kempf, Urs Ganse, Sebastian von Alfthan, Rami Vainio, and Michael Hesse
Ann. Geophys., 35, 1269–1274, https://doi.org/10.5194/angeo-35-1269-2017, https://doi.org/10.5194/angeo-35-1269-2017, 2017
Short summary
Short summary
Much like solar flares, substorms occurring within the Earth's magnetic domain are explosive events that cause vivid auroral displays. A decades-long debate exists to explain the substorm onset. We devise a simulation encompassing the entire near-Earth space and demonstrate that detailed modelling of magnetic reconnection explains the central substorm observations. Our results help to understand the unpredictable substorm process, which will significantly improve space weather forecasts.
Noora Partamies, James M. Weygand, and Liisa Juusola
Ann. Geophys., 35, 1069–1083, https://doi.org/10.5194/angeo-35-1069-2017, https://doi.org/10.5194/angeo-35-1069-2017, 2017
Short summary
Short summary
Large-scale undulations of the diffuse aurora boundary, auroral omega bands, have been studied based on 438 omega-like structures identified over Fennoscandian Lapland from 1996 to 2007. The omegas mainly occurred in the post-magnetic midnight sector, in the region between oppositely directed ionospheric field-aligned currents, and during substorm recovery phases. The omega bands were observed during substorms, which were more intense than the average substorm in the same region.
Antti Lakka, Tuija I. Pulkkinen, Andrew P. Dimmock, Adnane Osmane, Ilja Honkonen, Minna Palmroth, and Pekka Janhunen
Ann. Geophys., 35, 907–922, https://doi.org/10.5194/angeo-35-907-2017, https://doi.org/10.5194/angeo-35-907-2017, 2017
Short summary
Short summary
We studied the impact on global MHD simulations from different simulation initialisation methods. While the global MHD code used is GUMICS-4 we conclude that the results might be generalisable to other codes as well. It is found that different initialisation methods affect the dynamics of the Earth's space environment by creating differences in momentum transport several hours afterwards. These differences may even grow as a response to rapid solar wind condition changes.
Yann Pfau-Kempf, Heli Hietala, Steve E. Milan, Liisa Juusola, Sanni Hoilijoki, Urs Ganse, Sebastian von Alfthan, and Minna Palmroth
Ann. Geophys., 34, 943–959, https://doi.org/10.5194/angeo-34-943-2016, https://doi.org/10.5194/angeo-34-943-2016, 2016
Short summary
Short summary
We have simulated the interaction of the solar wind – the charged particles and magnetic fields emitted by the Sun into space – with the magnetic field of the Earth. The solar wind flows supersonically and creates a shock when it encounters the obstacle formed by the geomagnetic field. We have identified a new chain of events which causes phenomena in the downstream region to eventually cause perturbations at the shock and even upstream. This is confirmed by ground and satellite observations.
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
Short summary
Short summary
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.
Andrew P. Dimmock, Tuija I. Pulkkinen, Adnane Osmane, and Katariina Nykyri
Ann. Geophys., 34, 511–528, https://doi.org/10.5194/angeo-34-511-2016, https://doi.org/10.5194/angeo-34-511-2016, 2016
Short summary
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Ion densities measured on the dawn-side magnetosheath flank were higher than the dusk-flank. The asymmetry was measured close to the magnetopause, but it became more ambiguous in the central magnetosheath. We show that the asymmetry was at its maximum at the 2009 solar minimum (~ 20 %), but then decreased in the rising stage of the next solar cycle (< 5 %). These results could impact plasma transport processes which are dependent on local magnetopause conditions such as Kelvin Helmholtz Instability.
Peter Wintoft, Ari Viljanen, and Magnus Wik
Ann. Geophys., 34, 485–491, https://doi.org/10.5194/angeo-34-485-2016, https://doi.org/10.5194/angeo-34-485-2016, 2016
Short summary
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Extreme value analysis has been applied to 1-minute-resolution magnetic fields and computed electric fields over Europe. We find that on average the largest disturbances of the fields are observed close to the auroral oval, as expected. However, the analysis indicates that as we move south from Scandinavia to northern continental Europe the distribution becomes more extreme. This could be due to that strong storms regularly occur at high latitudes, while the extreme storms push the oval south.
M. Myllys, N. Partamies, and L. Juusola
Ann. Geophys., 33, 573–581, https://doi.org/10.5194/angeo-33-573-2015, https://doi.org/10.5194/angeo-33-573-2015, 2015
K. Andréeová, L. Juusola, E. K. J. Kilpua, and H. E. J. Koskinen
Ann. Geophys., 32, 1293–1302, https://doi.org/10.5194/angeo-32-1293-2014, https://doi.org/10.5194/angeo-32-1293-2014, 2014
N. Partamies, L. Juusola, E. Tanskanen, and K. Kauristie
Ann. Geophys., 31, 349–358, https://doi.org/10.5194/angeo-31-349-2013, https://doi.org/10.5194/angeo-31-349-2013, 2013
Related subject area
Subject: Earth's ionosphere & aeronomy | Keywords: Space weather effects
The time derivative of the geomagnetic field has a short memory
Atmospheric drag effects on modelled low Earth orbit (LEO) satellites during the July 2000 Bastille Day event in contrast to an interval of geomagnetically quiet conditions
Effects of solar flares on the ionosphere as shown by the dynamics of ionograms recorded in Europe and South Africa
Mirjam Kellinsalmi, Ari Viljanen, Liisa Juusola, and Sebastian Käki
Ann. Geophys., 40, 545–562, https://doi.org/10.5194/angeo-40-545-2022, https://doi.org/10.5194/angeo-40-545-2022, 2022
Short summary
Short summary
Eruptions from the Sun can pose a hazard to Earth's power grids via, e.g., geomagnetically induced currents (GICs). 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 2 min. 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.
Victor U. J. Nwankwo, William Denig, Sandip K. Chakrabarti, Muyiwa P. Ajakaiye, Johnson Fatokun, Adeniyi W. Akanni, Jean-Pierre Raulin, Emilia Correia, John E. Enoh, and Paul I. Anekwe
Ann. Geophys., 39, 397–412, https://doi.org/10.5194/angeo-39-397-2021, https://doi.org/10.5194/angeo-39-397-2021, 2021
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In this work, we simulated the effect of atmospheric drag on satellites in low Earth orbit (LEO) during 1-month intervals of disturbed and quiet solar geomagnetic activity. Our results show that geomagnetic storms (e.g. the Bastille Day event) can cause a significant drop in LEO satellite altitudes and increase their background orbit decay rate by 50–70 %. This work can contribute to improved situational awareness and mitigation of potential threats solar energetic events pose to satellites.
Veronika Barta, Gabriella Sátori, Kitti Alexandra Berényi, Árpád Kis, and Earle Williams
Ann. Geophys., 37, 747–761, https://doi.org/10.5194/angeo-37-747-2019, https://doi.org/10.5194/angeo-37-747-2019, 2019
Short summary
Short summary
The solar flare effects on ionosphere at midlatitudes and low latitudes were investigated with the systematic analysis of ionospheric parameters derived from ionograms (total radio fade-out, fmin, dfmin: deviation from the reference days). The duration of the total fade-out varied with the solar zenith angle. Furthermore, a solar-zenith-angle-dependent enhancement of the fmin and dfmin parameters was detected but the observed values also depended on the flare intensity.
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Short summary
We have examined events during which the measured magnetic field on the ground changes very rapidly, causing a risk to technological conductor networks. According to our results, such events occur when strong electric currents in the ionosphere at 100 km altitude are abruptly modified by sudden compression or expansion of the magnetospheric magnetic field farther in space.
We have examined events during which the measured magnetic field on the ground changes very...
