A5046677391- Ionosphere and magnetosphere dynamics
- Solar and Space Plasma Dynamics
- Geomagnetism and Paleomagnetism Studies
- Astro and Planetary Science
- Earthquake Detection and Analysis
- Magnetic confinement fusion research
- Gas Dynamics and Kinetic Theory
- Geophysics and Gravity Measurements
- Atmospheric Ozone and Climate
- Planetary Science and Exploration
- Stellar, planetary, and galactic studies
- Atomic and Subatomic Physics Research
- Astrophysics and Cosmic Phenomena
- Meteorological Phenomena and Simulations
- High-pressure geophysics and materials
- Statistical and numerical algorithms
- Fluid Dynamics and Turbulent Flows
- Laser-Plasma Interactions and Diagnostics
- Seismic Waves and Analysis
- Plant Ecology and Soil Science
- Water management and technologies
- Iron and Steelmaking Processes
- Cardiovascular Health and Disease Prevention
- Data Visualization and Analytics
- Optics and Image Analysis
University of Helsinki
2017-2025
Helsinki Institute of Physics
2020-2024
Laboratoire de Physique des Plasmas
2013-2017
European Space Research and Technology Centre
2015-2017
École Polytechnique
2013-2015
Centre National de la Recherche Scientifique
2013-2015
Sorbonne Université
2014-2015
Laboratoire de Mécanique des Sols, Structures et Matériaux
1965
This paper reviews Vlasov-based numerical methods used to model plasma in space physics and astrophysics. Plasma consists of collectively behaving charged particles that form the major part baryonic matter Universe. Many concepts ranging from our own planetary environment Solar system beyond can be understood terms kinetic physics, represented by Vlasov equation. We introduce physical basis for system, then outline associated are typically used. A particular application is Vlasiator, world's...
Abstract We discuss observations of the journey throughout Solar System a large interplanetary coronal mass ejection (ICME) that was ejected at Sun on 14 October 2014. The ICME hit Mars 17 October, as observed by Express, Atmosphere and Volatile EvolutioN Mission (MAVEN), Odyssey, Science Laboratory (MSL) missions, 44 h before encounter planet with Siding‐Spring comet, for which space weather context is provided. It reached comet 67P/Churyumov‐Gerasimenko, perfectly aligned 3.1 AU, Rosetta...
We present methods and algorithms that allow the Vlasiator code to run global, three-dimensional hybrid-Vlasov simulations of Earth's entire magnetosphere. The key ingredients make Vlasov at magnetospheric scales possible are sparse velocity space implementation spatial adaptive mesh refinement. outline algorithmic improvement semi-Lagrangian solver for six-dimensional phase quantities, discuss coupling Maxwell equations' solvers in a refined mesh, provide performance figures from simulation...
Abstract Magnetic reconnection and current sheet kink instability often develop concurrently in sheets, yet their dynamic interplay remains unclear. We investigate interaction the magnetotail of a 3D global magnetospheric hybrid‐Vlasov simulation. identify growth saturation phase estimate evolution rate during same interval. Our findings indicate that decreases phase, especially at locations where undergoes significant perturbations. These results highlight intricate three‐dimensional...
Abstract We explore the three‐dimensional structure of ion‐kinetic instabilities in a thin current layer using hybrid‐Vlasov simulation Earth's magnetosphere. The shows simultaneous growth tearing and kinking instabilities, which develop Sun‐Earth dawn‐dusk directions, respectively, within magnetotail sheet. formation flux ropes indicates development instability, while flapping‐type cross‐tail oscillations arise from kink instability. consider both as independent polarizations, albeit...
The Earth's magnetosphere and its bow shock, which is formed by the interaction of supersonic solar wind with terrestrial magnetic field, constitute a rich natural laboratory enabling in situ investigations universal plasma processes. Under suitable interplanetary field conditions, foreshock intense wave activity forms upstream shock. So-called 30 s waves, named after their typical period at Earth, are dominant mode play an important role modulating shape shock front affect particle...
Abstract This paper describes properties and behavior of magnetic reconnection flux transfer events (FTEs) on the dayside magnetopause using global hybrid‐Vlasov code Vlasiator. We investigate two simulation runs with without a sunward (positive) B x component interplanetary field (IMF) when IMF is southward. The are two‐dimensional in real space noon‐midnight meridional (polar) plane three‐dimensional velocity space. Solar wind input parameters identical simulations exception that purely...
Abstract In this paper, we present a detailed study of the effects interplanetary magnetic field (IMF) strength on foreshock properties at small and large scales. Two simulation runs performed with hybrid‐Vlasov code Vlasiator identical setup but different IMF strengths, namely, 5 10 nT, are compared. We find that bow shock position shape roughly in both runs, due to quasi‐radial orientation, agreement previous magnetohydrodynamic simulations theory. Foreshock waves develop broader region...
Abstract Rapid plasma eruptions explosively release energy within Earth’s magnetosphere, at the Sun and other planets. At Earth, these eruptions, termed plasmoids, occur in magnetospheric nightside are associated with sudden brightening of aurora. The chain events leading to plasmoid is one longest-standing unresolved questions space physics. Two competing paradigms have been proposed explain course events. first asserts that magnetic reconnection changes topology tail, severing a part...
Abstract. Compressed sheath regions form ahead of interplanetary coronal mass ejections (ICMEs) that are sufficiently faster than the preceding solar wind. The turbulent important drivers magnetospheric activity, but due to their complex internal structure, relatively little is known on distribution magnetic field and plasma variations in them. In this paper we investigate ultra low frequency (ULF) fluctuations (IMF) dynamic pressure (Pdyn) using a superposed epoch analysis 41 observed...
The magnetosphere is the lens through which solar space weather phenomena are focused and directed towards Earth. In particular, non-linear interaction of wind with Earth's magnetic field leads to formation highly inhomogenous electrical currents in ionosphere can ultimately result damage problems operation power distribution networks. Since electric fundamental cornerstone modern life, interruption primary pathway by has impact on human activity technology. Consequently, context weather, it...
Abstract We present a statistical study of interplanetary conditions and geospace response to 89 coronal mass ejection‐driven sheaths observed during Solar Cycles 23 24. investigate in particular the dependencies on driver properties variations across sheath. find that ejecta speed principally controls sheath geoeffectiveness shows highest correlations with parameters, region closest shock. Sheaths fast have average high solar wind speeds, magnetic ( B ) field magnitudes, fluctuations, they...
In hybrid-Vlasov plasma modeling, the ion velocity distribution function is propagated using Vlasov equation while electrons are considered a charge-neutralizing fluid. It an alternative to particle-in-cell methods, one advantage being absence of sampling noise in moments distribution. However, discretization requirements up six dimensions (3D position, 3V velocity) make computational cost models higher. This why modeling has only recently become more popular and available model large-scale...
Discontinuities in the solar wind, bow shock ripples or ionized dust clouds carried by high speed jets (HSJs) are observed magnetosheath. These HSJs have typically a Vx component larger than 200 km s-1 and their dynamic pressure can be few times wind pressure. We use conjunction of Cluster MMS, crossing simultaneously magnetopause, to study characteristics these impact on magnetopause. Over one hour-fifteen minutes interval magnetosheath, 21 HSJs. During same period, MMS 12 entered...
Abstract Earth’s magnetosheath consists of shocked solar wind plasma that has been compressed and slowed down at the bow shock. Magnetosheath jets are pulses enhanced dynamic pressure in magnetosheath. Jets have observed by numerous spacecraft missions, but their origin remained unconfirmed, though several formation mechanisms suggested. In this study, we use a method for automatically identifying tracking as well foreshock compressive structures (FCSs) four 2D runs global hybrid‐Vlasov...
Shock waves in collisionless plasmas are among the most efficient particle accelerators space. reformation is a process important to plasma heating and acceleration, but direct observations of at quasi-parallel shocks have been lacking. Here, we investigate Earth's bow shock with by four Magnetospheric Multiscale spacecraft. The multi-spacecraft provide evidence short large-amplitude magnetic structures (SLAMS) causing shock. We perform an ion-kinetic Vlasiator simulation show that SLAMS...
Abstract. We use a global hybrid-Vlasov simulation for the magnetosphere, Vlasiator, to investigate magnetosheath high-speed jets. Unlike many other hybrid-kinetic simulations, Vlasiator includes an unscaled geomagnetic dipole, indicating that spatial and temporal dimensions can be given in SI units without scaling. Thus, first time, this allows investigating jet properties comparing them directly with observed jets within Earth's magnetosheath. In run shown paper, interplanetary magnetic...
Coronal mass ejections (CMEs) and solar energetic particles (SEPs) are two phenomena that can cause severe space weather effects throughout the heliosphere. The evolution of CMEs, especially in terms their magnetic structure, configuration interplanetary field (IMF) influences transport SEPs currently areas active research. These aspects not necessarily independent each other, during maximum when multiple eruptive events occur close time. Accordingly, we present analysis a CME erupted on...
Abstract Vlasiator is a high‐performance ion‐kinetic code that now conducting 3D hybrid‐Vlasov simulations of the global magnetosphere. We use to investigate impact pressure pulse with southward‐oriented magnetic field on Earth's The simulation driving parameters are comparable conditions have led geomagnetic storms. Our reproduces many physical effects, namely expansion auroral oval, development field‐aligned currents, enhanced particle precipitation near open/closed line boundary, and...
Abstract Ultra‐Low Frequency (ULF) waves are critical drivers of particle acceleration and loss in the Earth's magnetosphere. While statistical models ULF‐induced radial transport have traditionally assumed that uniformly distributed across magnetic local time (MLT), decades observational evidence show significant MLT localization ULF This study presents, for first time, a quasi‐linear diffusion coefficient accounting localized waves. Our results reveal when cover more than 30% MLT,...
 On the macroscale, large-scale magnetic field structure governs magnetotail current layer. At same time, it must be supported by self-consistent dynamics of charged particles. While layer reaches a critical state, microscale processes start to play leading role triggering kinetic instabilities. These instabilities drive changes in topology and particle energization. This study examines Earth's using global hybrid-Vlasov simulations (Vlasiator). In our simulation, southward...
In this study we investigate the formation of magnetosheath jets before, during, and after interaction between Earth's bow shock a solar wind rotational discontinuity in 2D ecliptic simulation run global magnetospheric hybrid-Vlasov model Vlasiator. Magnetosheath are transient enhancements dynamic pressure downstream collisionless shocks, they have been observed magnetosheath, magnetosheaths other planets, as well sheaths interplanetary shocks. Rotational discontinuities (RD) boundaries...
At the electron scales power spectrum of solar-wind magnetic fluctuations can be highly variable and dissipation mechanisms energy into various particle species is under debate. In this paper we investigate data from Cluster mission's STAFF Search Coil magnetometer when level turbulence sufficiently high that morphology at investigated. The spacecraft sample a disturbed interval plasma where two streams solar wind interact. Meanwhile, several discontinuities (coherent structures) are seen in...