Articles | Volume 41, issue 2
https://doi.org/10.5194/angeo-41-483-2023
© 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-41-483-2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Regular paper
| 
16 Nov 2023
Regular paper |
| 16 Nov 2023
| 16 Nov 2023
Three principal components describe the spatiotemporal development of mesoscale ionospheric equivalent currents around substorm onsets
Finnish Meteorological Institute, Helsinki, Finland
Ari Viljanen
Finnish Meteorological Institute, Helsinki, Finland
Noora Partamies
Department of Arctic Geophysics, University Centre in Svalbard (UNIS), Longyearbyen, Norway
Heikki Vanhamäki
Space Physics and Astronomy Research Unit, University of Oulu, Oulu, Finland
Mirjam Kellinsalmi
Finnish Meteorological Institute, Helsinki, Finland
Simon Walker
Department of Physics and Technology, University of Bergen, Bergen, Norway
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Abiyot Bires Workayehu, Minna Palmroth, Maxime Grandin, Liisa Juusola, Markku Alho, Ivan Zaitsev, Venla Koikkalainen, Konstantinos Horaites, Yann Pfau-Kempf, Urs Ganse, Markus Battarbee, and Jonas Suni
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We investigate the ionospheric signatures of BBFs in the magnetotail utilising a global 6D hybrid-Vlasov simulation coupled with an ionospheric model. We analyse changes in the magnitudes of ionospheric observables and use them as the ionospheric manifestations of bursty bulk flows. Our results reveal that reconnection-driven BBF induce vortices that generate FACs, which map to the ionosphere with distinct east-west alignment and exhibit a characteristic westward drift.
Venla Koikkalainen, Maxime Grandin, Emilia Kilpua, Abiyot Workayehu, Ivan Zaitsev, Liisa Juusola, Shi Tao, Markku Alho, Lauri Pänkäläinen, Giulia Cozzani, Konstantinos Horaites, Jonas Suni, Yann Pfau-Kempf, Urs Ganse, and Minna Palmroth
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We use a numerical simulation to study phenomena that occur between the Earth’s dipolar magnetic field and the nightside of near-Earth space. We observe the formation of large-scale vortex flows with scales of several Earth radii. On the ionospheric grid of the simulation we find that the field-aligned currents formed in the simulation reflect the vortex flow in the transition region. The main finding is that the vortex flow is a result of a combination of flow dynamics and a plasma instability.
Liisa Juusola, Ilkka Virtanen, Spencer Mark Hatch, Heikki Vanhamäki, Maxime Grandin, Noora Partamies, Urs Ganse, Ilja Honkonen, Abiyot Workayehu, Antti Kero, and Minna Palmroth
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Key properties of the ionospheric electrodynamics are electric fields, currents, and conductances. They provide a window to the vast and distant near-Earth space, cause Joule heating that affect satellite orbits, and drive geomagnetically induced currents (GICs) in technological conductor networks. We have developed a new method for solving the key properties of ionospheric electrodynamics from ground-based magnetic field observations.
Liisa Juusola, Heikki Vanhamäki, Elena Marshalko, Mikhail Kruglyakov, and Ari Viljanen
Ann. Geophys., 43, 271–301, https://doi.org/10.5194/angeo-43-271-2025, https://doi.org/10.5194/angeo-43-271-2025, 2025
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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., 18, 511–527, https://doi.org/10.5194/gmd-18-511-2025, https://doi.org/10.5194/gmd-18-511-2025, 2025
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Vlasiator is a kinetic space plasma model that simulates the behavior of plasma, solar wind and magnetic fields in near-Earth space. So far, these simulations have been run without any interaction with the ionosphere, the uppermost layer of Earth's atmosphere. In this paper, 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
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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, Andrew P. Dimmock, Mirjam Kellinsalmi, Audrey Schillings, and James M. Weygand
Ann. Geophys., 41, 13–37, https://doi.org/10.5194/angeo-41-13-2023, https://doi.org/10.5194/angeo-41-13-2023, 2023
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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.
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
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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
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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
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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.
Abiyot Bires Workayehu, Minna Palmroth, Maxime Grandin, Liisa Juusola, Markku Alho, Ivan Zaitsev, Venla Koikkalainen, Konstantinos Horaites, Yann Pfau-Kempf, Urs Ganse, Markus Battarbee, and Jonas Suni
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We investigate the ionospheric signatures of BBFs in the magnetotail utilising a global 6D hybrid-Vlasov simulation coupled with an ionospheric model. We analyse changes in the magnitudes of ionospheric observables and use them as the ionospheric manifestations of bursty bulk flows. Our results reveal that reconnection-driven BBF induce vortices that generate FACs, which map to the ionosphere with distinct east-west alignment and exhibit a characteristic westward drift.
Karl M. Laundal, Andreas S. Skeidsvoll, Beatrice Popescu Braileanu, Spencer M. Hatch, Nils Olsen, and Heikki Vanhamäki
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The ionosphere is where Earth’s atmosphere overlaps with a gas of charged particles in space. There, collisions with neutral air and electromagnetic forces driven by the solar wind control plasma motion. We created a global model that includes magnetic induction, explaining how electric currents and fields are altered, offering a more accurate view of atmosphere–space coupling than conventional models based on electric circuits.
Venla Koikkalainen, Maxime Grandin, Emilia Kilpua, Abiyot Workayehu, Ivan Zaitsev, Liisa Juusola, Shi Tao, Markku Alho, Lauri Pänkäläinen, Giulia Cozzani, Konstantinos Horaites, Jonas Suni, Yann Pfau-Kempf, Urs Ganse, and Minna Palmroth
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Short summary
We use a numerical simulation to study phenomena that occur between the Earth’s dipolar magnetic field and the nightside of near-Earth space. We observe the formation of large-scale vortex flows with scales of several Earth radii. On the ionospheric grid of the simulation we find that the field-aligned currents formed in the simulation reflect the vortex flow in the transition region. The main finding is that the vortex flow is a result of a combination of flow dynamics and a plasma instability.
Liisa Juusola, Ilkka Virtanen, Spencer Mark Hatch, Heikki Vanhamäki, Maxime Grandin, Noora Partamies, Urs Ganse, Ilja Honkonen, Abiyot Workayehu, Antti Kero, and Minna Palmroth
EGUsphere, https://doi.org/10.5194/egusphere-2025-2394, https://doi.org/10.5194/egusphere-2025-2394, 2025
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Short summary
Key properties of the ionospheric electrodynamics are electric fields, currents, and conductances. They provide a window to the vast and distant near-Earth space, cause Joule heating that affect satellite orbits, and drive geomagnetically induced currents (GICs) in technological conductor networks. We have developed a new method for solving the key properties of ionospheric electrodynamics from ground-based magnetic field observations.
Liisa Juusola, Heikki Vanhamäki, Elena Marshalko, Mikhail Kruglyakov, and Ari Viljanen
Ann. Geophys., 43, 271–301, https://doi.org/10.5194/angeo-43-271-2025, https://doi.org/10.5194/angeo-43-271-2025, 2025
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., 18, 511–527, https://doi.org/10.5194/gmd-18-511-2025, https://doi.org/10.5194/gmd-18-511-2025, 2025
Short summary
Short summary
Vlasiator is a kinetic space plasma model that simulates the behavior of plasma, solar wind and magnetic fields in near-Earth space. So far, these simulations have been run without any interaction with the ionosphere, the uppermost layer of Earth's atmosphere. In this paper, 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.
Spencer Mark Hatch, Heikki Vanhamäki, Karl Magnus Laundal, Jone Peter Reistad, Johnathan K. Burchill, Levan Lomidze, David J. Knudsen, Michael Madelaire, and Habtamu Tesfaw
Ann. Geophys., 42, 229–253, https://doi.org/10.5194/angeo-42-229-2024, https://doi.org/10.5194/angeo-42-229-2024, 2024
Short summary
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In studies of the Earth's ionosphere, a hot topic is how to estimate ionospheric conductivity. This is hard to do for a variety of reasons that mostly amount to a lack of measurements. In this study we use satellite measurements to estimate electromagnetic work and ionospheric conductances in both hemispheres. We identify where our model estimates are inconsistent with laws of physics, which partially solves a previous problem with unrealistic predictions of ionospheric conductances.
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.
Anton Goertz, Noora Partamies, Daniel Whiter, and Lisa Baddeley
Ann. Geophys., 41, 115–128, https://doi.org/10.5194/angeo-41-115-2023, https://doi.org/10.5194/angeo-41-115-2023, 2023
Short summary
Short summary
Poleward moving auroral forms (PMAFs) are specific types of aurora believed to be the signature of the connection of Earth's magnetic field to that of the sun. In this paper, we discuss the evolution of PMAFs with regard to their auroral morphology as observed in all-sky camera images. We interpret different aspects of this evolution in terms of the connection dynamics between the magnetic fields of Earth and the sun. This sheds more light on the magnetic interaction between the sun and Earth.
Liisa Juusola, Ari Viljanen, Andrew P. Dimmock, Mirjam Kellinsalmi, Audrey Schillings, and James M. Weygand
Ann. Geophys., 41, 13–37, https://doi.org/10.5194/angeo-41-13-2023, https://doi.org/10.5194/angeo-41-13-2023, 2023
Short summary
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.
Daniel K. Whiter, Noora Partamies, Björn Gustavsson, and Kirsti Kauristie
Ann. Geophys., 41, 1–12, https://doi.org/10.5194/angeo-41-1-2023, https://doi.org/10.5194/angeo-41-1-2023, 2023
Short summary
Short summary
We measured the height of green and blue aurorae using thousands of camera images recorded over a 7-year period. Both colours are typically brightest at about 114 km altitude. When they peak at higher altitudes the blue aurora is usually higher than the green aurora. This information will help other studies which need an estimate of the auroral height. We used a computer model to explain our observations and to investigate how the green aurora is produced.
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.
Derek McKay, Juha Vierinen, Antti Kero, and Noora Partamies
Geosci. Instrum. Method. Data Syst., 11, 25–35, https://doi.org/10.5194/gi-11-25-2022, https://doi.org/10.5194/gi-11-25-2022, 2022
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When radio waves from our galaxy enter the Earth's atmosphere, they are absorbed by electrons in the upper atmosphere. It was thought that by measuring the amount of absorption, it would allow the height of these electrons in the atmosphere to be determined. If so, this would have significance for future instrument design. However, this paper demonstrates that it is not possible to do this, but it does explain how multiple-frequency measurements can nevertheless be useful.
Fasil Tesema, Noora Partamies, Daniel K. Whiter, and Yasunobu Ogawa
Ann. Geophys., 40, 1–10, https://doi.org/10.5194/angeo-40-1-2022, https://doi.org/10.5194/angeo-40-1-2022, 2022
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In this study, we present the comparison between an auroral model and EISCAT radar electron densities during pulsating aurorae. We test whether an overpassing satellite measurement of the average energy spectrum is a reasonable estimate for pulsating aurora electron precipitation. When patchy pulsating aurora is dominant in the morning sector, the overpass-averaged spectrum is found to be a reasonable estimate – but not when there is a mix of pulsating aurora types in the post-midnight sector.
Daniel K. Whiter, Hanna Sundberg, Betty S. Lanchester, Joshua Dreyer, Noora Partamies, Nickolay Ivchenko, Marco Zaccaria Di Fraia, Rosie Oliver, Amanda Serpell-Stevens, Tiffany Shaw-Diaz, and Thomas Braunersreuther
Ann. Geophys., 39, 975–989, https://doi.org/10.5194/angeo-39-975-2021, https://doi.org/10.5194/angeo-39-975-2021, 2021
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This paper presents an analysis of high-resolution optical and radar observations of a phenomenon called fragmented aurora-like emissions (FAEs) observed close to aurora in the high Arctic. The observations suggest that FAEs are not caused by high-energy electrons or protons entering the atmosphere along Earth's magnetic field and are, therefore, not aurora. The speeds of the FAEs and their internal dynamics were measured and used to evaluate theories for how the FAEs are produced.
Florine Enengl, Noora Partamies, Nickolay Ivchenko, and Lisa Baddeley
Ann. Geophys., 39, 795–809, https://doi.org/10.5194/angeo-39-795-2021, https://doi.org/10.5194/angeo-39-795-2021, 2021
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Energetic particle precipitation has the potential to change the neutral atmospheric temperature at the bottom of the ionosphere. We have searched for events and investigated a possible correlation between lower-ionosphere electron density enhancements and simultaneous neutral temperature changes. Six of the 10 analysed events are associated with a temperature decrease of 10–20K. The events change the chemical composition in the mesosphere, and the temperatures are probed at lower altitudes.
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.
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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.
At times when auroras erupt on the sky, the magnetic field surrounding the Earth undergoes rapid...
