Articles | Volume 38, issue 5
https://doi.org/10.5194/angeo-38-983-2020
© Author(s) 2020. 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-38-983-2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Induced currents due to 3D ground conductivity play a major role in the interpretation of geomagnetic variations
Finnish Meteorological Institute, Helsinki, Finland
Heikki Vanhamäki
Space Physics and Astronomy Research Unit, University of Oulu, Oulu, Finland
Ari Viljanen
Finnish Meteorological Institute, Helsinki, Finland
Maxim Smirnov
Department of Civil, Environmental and Natural Resources Engineering, Luleå University of Technology, Luleå, Sweden
Related authors
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
Preprint under review 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.
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.
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.
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
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
Short summary
Short summary
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
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
Preprint under review 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.
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
Short summary
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.
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.
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.
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.
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
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
Short summary
Short summary
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.
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
Short summary
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: Electric fields and currents
Testing the electrodynamic method to derive height-integrated ionospheric conductances
High-latitude crochet: solar-flare-induced magnetic disturbance independent from low-latitude crochet
Horizontal electric fields from flow of auroral O+(2P) ions at sub-second temporal resolution
Daniel Weimer and Thom Edwards
Ann. Geophys., 39, 31–51, https://doi.org/10.5194/angeo-39-31-2021, https://doi.org/10.5194/angeo-39-31-2021, 2021
Short summary
Short summary
The electrical conductivity of the Earth's ionosphere is an important parameter in the study of the polar,
auroral currents that produce magnetic disturbances on the ground. Yet the values of the conductances, and
how they vary, are not known with great precision. In our study we tested a method for deriving the conductivity
values that requires use of three empirical models for the electric fields above the ionosphere and the
magnetic field perturbations both on the ground and in space.
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
Short summary
Short summary
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.
Sam Tuttle, Betty Lanchester, Björn Gustavsson, Daniel Whiter, Nickolay Ivchenko, Robert Fear, and Mark Lester
Ann. Geophys., 38, 845–859, https://doi.org/10.5194/angeo-38-845-2020, https://doi.org/10.5194/angeo-38-845-2020, 2020
Short summary
Short summary
Electric fields in the atmosphere near dynamic aurora are important in the physics of the electric circuit within the Earth's magnetic field. Oxygen ions emit light as they move under the influence of these electric fields; the flow of this emission is used to find the electric field at high temporal resolution. The solution needs two other simultaneous measurements of auroral emissions to give key parameters such as the auroral energy. The electric fields increase with brightness of the aurora.
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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.
Rapid variations of the magnetic field measured on the ground can be used to estimate space...