Articles | Volume 35, issue 4
https://doi.org/10.5194/angeo-35-907-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
the Creative Commons Attribution 3.0 License.
https://doi.org/10.5194/angeo-35-907-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
the Creative Commons Attribution 3.0 License.
Regular paper
| 
01 Aug 2017
Regular paper |
| 01 Aug 2017
The impact on global magnetohydrodynamic simulations from varying initialisation methods: results from GUMICS-4
Antti Lakka
CORRESPONDING AUTHOR
Department of Electronics and Nanoengineering, Aalto University, Espoo, Finland
Tuija I. Pulkkinen
Department of Electronics and Nanoengineering, Aalto University, Espoo, Finland
Andrew P. Dimmock
Department of Electronics and Nanoengineering, Aalto University, Espoo, Finland
Adnane Osmane
Department of Electronics and Nanoengineering, Aalto University, Espoo, Finland
Ilja Honkonen
Finnish Meteorological Institute, Helsinki, Finland
Minna Palmroth
Department of Physics, University of Helsinki, Helsinki, Finland
Pekka Janhunen
Finnish Meteorological Institute, Helsinki, Finland
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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.
Leo Kotipalo, Markus Battarbee, Yann Pfau-Kempf, and Minna Palmroth
Geosci. Model Dev., 17, 6401–6413, https://doi.org/10.5194/gmd-17-6401-2024, https://doi.org/10.5194/gmd-17-6401-2024, 2024
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This paper examines a method called adaptive mesh refinement in optimization of the space plasma simulation model Vlasiator. The method locally adjusts resolution in regions which are most relevant to modelling, based on the properties of the plasma. The runs testing this method show that adaptive refinement manages to highlight the desired regions with manageable performance overhead. Performance in larger-scale production runs and mitigation of overhead are avenues of further research.
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
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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.
Tuomas Häkkilä, Maxime Grandin, Markus Battarbee, Monika E. Szeląg, Markku Alho, Leo Kotipalo, Niilo Kalakoski, Pekka T. Verronen, and Minna Palmroth
Ann. Geophys. Discuss., https://doi.org/10.5194/angeo-2024-7, https://doi.org/10.5194/angeo-2024-7, 2024
Preprint under review for ANGEO
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We study the atmospheric impact of auroral electron precipitation, by the novel combination of both magnetospheric and atmospheric modelling. We first simulate fluxes of auroral electrons, and then use these fluxes to model their atmospheric impact. We find an increase of up to 200 % in thermospheric odd nitrogen, and a corresponding decrease in stratospheric ozone of around 0.7 %. The produced auroral electron precipitation is realistic, and shows the potential for future studies.
Markku Alho, Giulia Cozzani, Ivan Zaitsev, Fasil Tesema Kebede, Urs Ganse, Markus Battarbee, Maarja Bussov, Maxime Dubart, Sanni Hoilijoki, Leo Kotipalo, Konstantinos Papadakis, Yann Pfau-Kempf, Jonas Suni, Vertti Tarvus, Abiyot Workayehu, Hongyang Zhou, and Minna Palmroth
Ann. Geophys., 42, 145–161, https://doi.org/10.5194/angeo-42-145-2024, https://doi.org/10.5194/angeo-42-145-2024, 2024
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Magnetic reconnection is one of the main processes for energy conversion and plasma transport in space plasma physics, associated with plasma entry into the magnetosphere of Earth and Earth’s substorm cycle. Global modelling of these plasma processes enables us to understand the magnetospheric system in detail. However, finding sites of active reconnection from large simulation datasets can be challenging, and this paper develops tools to find magnetic topologies related to reconnection.
Sanjay Kumar and Tuija I. Pulkkinen
EGUsphere, https://doi.org/10.5194/egusphere-2024-1113, https://doi.org/10.5194/egusphere-2024-1113, 2024
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We analyze magnetopause location, influenced by solar wind and IMF. Shue's (1998) model predicts its position based on solar wind pressure & IMF Bz. We investigate its location under northward/southward IMF & substorms using Shue's model & THEMIS/RBSP/MMS data. We observe significant magnetopause compression during strong northward/southward IMF around substorm peak.
Jonas Suni, Minna Palmroth, Lucile Turc, Markus Battarbee, Giulia Cozzani, Maxime Dubart, Urs Ganse, Harriet George, Evgeny Gordeev, Konstantinos Papadakis, Yann Pfau-Kempf, Vertti Tarvus, Fasil Tesema, and Hongyang Zhou
Ann. Geophys., 41, 551–568, https://doi.org/10.5194/angeo-41-551-2023, https://doi.org/10.5194/angeo-41-551-2023, 2023
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Magnetosheath jets are structures of enhanced plasma density and/or velocity in a region of near-Earth space known as the magnetosheath. When they propagate towards the Earth, these jets can disturb the Earth's magnetic field and cause hazards for satellites. In this study, we use a simulation called Vlasiator to model near-Earth space and investigate jets using case studies and statistical analysis. We find that jets that propagate towards the Earth are different from jets that do not.
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.
Konstantinos Papadakis, Yann Pfau-Kempf, Urs Ganse, Markus Battarbee, Markku Alho, Maxime Grandin, Maxime Dubart, Lucile Turc, Hongyang Zhou, Konstantinos Horaites, Ivan Zaitsev, Giulia Cozzani, Maarja Bussov, Evgeny Gordeev, Fasil Tesema, Harriet George, Jonas Suni, Vertti Tarvus, and Minna Palmroth
Geosci. Model Dev., 15, 7903–7912, https://doi.org/10.5194/gmd-15-7903-2022, https://doi.org/10.5194/gmd-15-7903-2022, 2022
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Vlasiator is a plasma simulation code that simulates the entire near-Earth space at a global scale. As 6D simulations require enormous amounts of computational resources, Vlasiator uses adaptive mesh refinement (AMR) to lighten the computational burden. However, due to Vlasiator’s grid topology, AMR simulations suffer from grid aliasing artifacts that affect the global results. In this work, we present and evaluate the performance of a mechanism for alleviating those artifacts.
Vertti Tarvus, Lucile Turc, Markus Battarbee, Jonas Suni, Xóchitl Blanco-Cano, Urs Ganse, Yann Pfau-Kempf, Markku Alho, Maxime Dubart, Maxime Grandin, Andreas Johlander, Konstantinos Papadakis, and Minna Palmroth
Ann. Geophys., 39, 911–928, https://doi.org/10.5194/angeo-39-911-2021, https://doi.org/10.5194/angeo-39-911-2021, 2021
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We use simulations of Earth's magnetosphere and study the formation of transient wave structures in the region where the solar wind first interacts with the magnetosphere. These transients move earthward and play a part in the solar wind–magnetosphere interaction. We show that the transients are a common feature and their properties are altered as they move earthward, including an increase in temperature, decrease in solar wind speed and an alteration in their propagation properties.
Andrei Runov, Maxime Grandin, Minna Palmroth, Markus Battarbee, Urs Ganse, Heli Hietala, Sanni Hoilijoki, Emilia Kilpua, Yann Pfau-Kempf, Sergio Toledo-Redondo, Lucile Turc, and Drew Turner
Ann. Geophys., 39, 599–612, https://doi.org/10.5194/angeo-39-599-2021, https://doi.org/10.5194/angeo-39-599-2021, 2021
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In collisionless systems like space plasma, particle velocity distributions contain fingerprints of ongoing physical processes. However, it is challenging to decode this information from observations. We used hybrid-Vlasov simulations to obtain ion velocity distribution functions at different locations and at different stages of the Earth's magnetosphere dynamics. The obtained distributions provide valuable examples that may be directly compared with observations by satellites in space.
Minna Palmroth, Savvas Raptis, Jonas Suni, Tomas Karlsson, Lucile Turc, Andreas Johlander, Urs Ganse, Yann Pfau-Kempf, Xochitl Blanco-Cano, Mojtaba Akhavan-Tafti, Markus Battarbee, Maxime Dubart, Maxime Grandin, Vertti Tarvus, and Adnane Osmane
Ann. Geophys., 39, 289–308, https://doi.org/10.5194/angeo-39-289-2021, https://doi.org/10.5194/angeo-39-289-2021, 2021
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Magnetosheath jets are high-velocity features within the Earth's turbulent magnetosheath, separating the Earth's magnetic domain from the solar wind. The characteristics of the jets are difficult to assess statistically as a function of their lifetime because normally spacecraft observe them only at one position within the magnetosheath. This study first confirms the accuracy of the model used, Vlasiator, by comparing it to MMS spacecraft, and then carries out the first jet lifetime statistics.
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.
Markus Battarbee, Thiago Brito, Markku Alho, Yann Pfau-Kempf, Maxime Grandin, Urs Ganse, Konstantinos Papadakis, Andreas Johlander, Lucile Turc, Maxime Dubart, and Minna Palmroth
Ann. Geophys., 39, 85–103, https://doi.org/10.5194/angeo-39-85-2021, https://doi.org/10.5194/angeo-39-85-2021, 2021
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We investigate local acceleration dynamics of electrons with a new numerical simulation method, which is an extension of a world-leading kinetic plasma simulation. We describe how large supercomputer simulations can be used to initialize the electron simulations and show numerical stability for the electron method. We show that features of our simulated electrons match observations from Earth's magnetic tail region.
Maxime Dubart, Urs Ganse, Adnane Osmane, Andreas Johlander, Markus Battarbee, Maxime Grandin, Yann Pfau-Kempf, Lucile Turc, and Minna Palmroth
Ann. Geophys., 38, 1283–1298, https://doi.org/10.5194/angeo-38-1283-2020, https://doi.org/10.5194/angeo-38-1283-2020, 2020
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Plasma waves are ubiquitous in the Earth's magnetosphere. They are responsible for many energetic processes happening in Earth's atmosphere, such as auroras. In order to understand these processes, thorough investigations of these waves are needed. We use a state-of-the-art numerical model to do so. Here we investigate the impact of different spatial resolutions in the model on these waves in order to improve in the future the model without wasting computational resources.
Markus Battarbee, Xóchitl Blanco-Cano, Lucile Turc, Primož Kajdič, Andreas Johlander, Vertti Tarvus, Stephen Fuselier, Karlheinz Trattner, Markku Alho, Thiago Brito, Urs Ganse, Yann Pfau-Kempf, Mojtaba Akhavan-Tafti, Tomas Karlsson, Savvas Raptis, Maxime Dubart, Maxime Grandin, Jonas Suni, and Minna Palmroth
Ann. Geophys., 38, 1081–1099, https://doi.org/10.5194/angeo-38-1081-2020, https://doi.org/10.5194/angeo-38-1081-2020, 2020
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We investigate the dynamics of helium in the foreshock, a part of near-Earth space found upstream of the Earth's bow shock. We show how the second most common ion in interplanetary space reacts strongly to plasma waves found in the foreshock. Spacecraft observations and supercomputer simulations both give us a new understanding of the foreshock edge and how to interpret future observations.
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
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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.
Harriet George, Emilia Kilpua, Adnane Osmane, Timo Asikainen, Milla M. H. Kalliokoski, Craig J. Rodger, Stepan Dubyagin, and Minna Palmroth
Ann. Geophys., 38, 931–951, https://doi.org/10.5194/angeo-38-931-2020, https://doi.org/10.5194/angeo-38-931-2020, 2020
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We compared trapped outer radiation belt electron fluxes to high-latitude precipitating electron fluxes during two interplanetary coronal mass ejections (ICMEs) with opposite magnetic cloud rotation. The electron response had many similarities and differences between the two events, indicating that different acceleration mechanisms acted. Van Allen Probe data were used for trapped electron flux measurements, and Polar Operational Environmental Satellites were used for precipitating flux data.
Milla M. H. Kalliokoski, Emilia K. J. Kilpua, Adnane Osmane, Drew L. Turner, Allison N. Jaynes, Lucile Turc, Harriet George, and Minna Palmroth
Ann. Geophys., 38, 683–701, https://doi.org/10.5194/angeo-38-683-2020, https://doi.org/10.5194/angeo-38-683-2020, 2020
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We present a comprehensive statistical study of the response of the Earth's space environment in sheath regions prior to interplanetary coronal mass ejections. The inner magnetospheric wave activity is enhanced in sheath regions, and the sheaths cause significant changes to the outer radiation belt electron fluxes over short timescales. We also show that non-geoeffective sheaths can result in a significant response.
Markus Battarbee, Urs Ganse, Yann Pfau-Kempf, Lucile Turc, Thiago Brito, Maxime Grandin, Tuomas Koskela, and Minna Palmroth
Ann. Geophys., 38, 625–643, https://doi.org/10.5194/angeo-38-625-2020, https://doi.org/10.5194/angeo-38-625-2020, 2020
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The structure and medium-scale dynamics of Earth's bow shock and how charged solar wind particles are reflected by it are studied in order to better understand space weather effects. We use advanced supercomputer simulations to model the shock and reflected ions. We find that the thickness of the shock depends on solar wind conditions but also has small-scale variations. Charged particle reflection is shown to be non-localized. Magnetic fields are important for ion reflection.
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.
Maxime Grandin, Markus Battarbee, Adnane Osmane, Urs Ganse, Yann Pfau-Kempf, Lucile Turc, Thiago Brito, Tuomas Koskela, Maxime Dubart, and Minna Palmroth
Ann. Geophys., 37, 791–806, https://doi.org/10.5194/angeo-37-791-2019, https://doi.org/10.5194/angeo-37-791-2019, 2019
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When the terrestrial magnetic field is disturbed, particles from the near-Earth space can precipitate into the upper atmosphere. This work presents, for the first time, numerical simulations of proton precipitation in the energy range associated with the production of aurora (∼1–30 keV) using a global kinetic model of the near-Earth space: Vlasiator. We find that nightside proton precipitation can be regulated by the transition region between stretched and dipolar geomagnetic field lines.
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
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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.
Minna Palmroth, Heli Hietala, Ferdinand Plaschke, Martin Archer, Tomas Karlsson, Xóchitl Blanco-Cano, David Sibeck, Primož Kajdič, Urs Ganse, Yann Pfau-Kempf, Markus Battarbee, and Lucile Turc
Ann. Geophys., 36, 1171–1182, https://doi.org/10.5194/angeo-36-1171-2018, https://doi.org/10.5194/angeo-36-1171-2018, 2018
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Magnetosheath jets are high-velocity plasma structures that are commonly observed within the Earth's magnetosheath. Previously, they have mainly been investigated with spacecraft observations, which do not allow us to infer their spatial sizes, temporal evolution, or origin. This paper shows for the first time their dimensions, evolution, and origins within a simulation whose dimensions are directly comparable to the Earth's magnetosphere. The results are compared to previous observations.
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
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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
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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.
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
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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.
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
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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.
P. Janhunen
Ann. Geophys., 33, 1507–1512, https://doi.org/10.5194/angeo-33-1507-2015, https://doi.org/10.5194/angeo-33-1507-2015, 2015
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The solar wind electric sail (E-sail) is a new way to move in the solar system efficiently without consuming propellant. The E-sail taps momentum from the solar wind by long, charged and centrifugally stretched tethers. Here we develop a new type of simulation for predicting E-sail thrust. The new simulation involves some approximations, but is robust and executes fast on a computer. The results are in good agreement with an earlier theoretical prediction. The E-sail thrust seems strong.
M. Myllys, E. Kilpua, and T. Pulkkinen
Ann. Geophys., 33, 845–855, https://doi.org/10.5194/angeo-33-845-2015, https://doi.org/10.5194/angeo-33-845-2015, 2015
P. T. Verronen, M. E. Andersson, A. Kero, C.-F. Enell, J. M. Wissing, E. R. Talaat, K. Kauristie, M. Palmroth, T. E. Sarris, and E. Armandillo
Ann. Geophys., 33, 381–394, https://doi.org/10.5194/angeo-33-381-2015, https://doi.org/10.5194/angeo-33-381-2015, 2015
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Electron concentrations observed by EISCAT radars can be reasonable well represented using AIMOS v1.2 satellite-data-based ionization model and SIC D-region ion chemistry model. SIC-EISCAT difference varies from event to event, probably because the statistical nature of AIMOS ionization is not capturing all the spatio-temporal fine structure of electron precipitation. Below 90km, AIMOS overestimates electron ionization because of proton contamination of the satellite electron detectors.
P. Janhunen
Ann. Geophys., 32, 1207–1216, https://doi.org/10.5194/angeo-32-1207-2014, https://doi.org/10.5194/angeo-32-1207-2014, 2014
D. Pokhotelov, S. von Alfthan, Y. Kempf, R. Vainio, H. E. J. Koskinen, and M. Palmroth
Ann. Geophys., 31, 2207–2212, https://doi.org/10.5194/angeo-31-2207-2013, https://doi.org/10.5194/angeo-31-2207-2013, 2013
A. T. Aikio, T. Pitkänen, I. Honkonen, M. Palmroth, and O. Amm
Ann. Geophys., 31, 1021–1034, https://doi.org/10.5194/angeo-31-1021-2013, https://doi.org/10.5194/angeo-31-1021-2013, 2013
A. Kestilä, T. Tikka, P. Peitso, J. Rantanen, A. Näsilä, K. Nordling, H. Saari, R. Vainio, P. Janhunen, J. Praks, and M. Hallikainen
Geosci. Instrum. Method. Data Syst., 2, 121–130, https://doi.org/10.5194/gi-2-121-2013, https://doi.org/10.5194/gi-2-121-2013, 2013
P. Janhunen, A. A. Quarta, and G. Mengali
Geosci. Instrum. Method. Data Syst., 2, 85–95, https://doi.org/10.5194/gi-2-85-2013, https://doi.org/10.5194/gi-2-85-2013, 2013
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.
We studied the impact on global MHD simulations from different simulation initialisation...
