The Vlasiator 5.2 ionosphere - coupling a magnetospheric hybrid-Vlasov simulation with a height-integrated ionosphere model

Aug 22, 2026

Simulations of the coupled ionosphere–magnetosphere system support understanding of geospace and space-weather responses, yet most global models rely on fluid plasma descriptions with an electrostatic ionosphere. Kinetic global magnetosphere modeling coupled to an ionosphere remains uncommon. The work introduces an ionospheric boundary model for the Vlasiator near-Earth system, deriving the ionospheric potential from field-aligned currents and plasma quantities on an unstructured grid, then mapping the resulting electric field to the magnetospheric inner boundary to enable two-region current formation.

LanguageEnglish

CategoryResearch & Report

FormatPDF

Pages17

Reading Time43 min

AccessFree to download

Introduction

Ionospheric physics and space-weather relevance

Current system regions (Region 1 and Region 2)

Modeling approaches and coupling challenges

Coupling mechanisms between magnetosphere and ionosphere

Geosci. Model Dev., 18, 511–527, 2025 [https://doi.org/10.5194/gmd-18-511-2025](https://doi.org/10.5194/gmd-18-511-2025)[ ](https://doi.org/10.5194/gmd-18-511-2025)© Author(s) 2025 . This work is distributed under the Creative Commons Attribution 4 .0 License. The Vlasiator 5.2 ionosphere – coupling a magnetospheric hybrid-Vlasov simulation with a height-integrated ionosphere model Urs Ganse 1 , Yann Pfau-Kempf1 , Hongyang Zhou 1 , Liisa Juusola 1,2 , Abiyot Workayehu 1 , Fasil Kebede 1 , Konstantinos Papadakis 1 , Maxime Grandin 1 , Markku Alho 1 , Markus Battarbee 1 , Maxime Dubart 1 , Leo Kotipalo 1 , Arnaud Lalagüe 1 , Jonas Suni 1 , Konstantinos Horaites 1 , and Minna Palmroth 1,2 1Department of Physics, University of Helsinki, Helsinki, Finland 2Finnish Meteorological Institute, Helsinki, Finland Correspondence: Urs Ganse (urs.ganse@helsinki.ﬁ) Received: 30 May 2024 – Discussion started: 4 July 2024 Revised: 31 October 2024 – Accepted: 19 November 2024 – Published: 29 January 2025 Abstract. Simulations of the coupled ionosphere– magnetosphere system are a key tool to understand geospace and its response to space weather. For the most part, they are based on ﬂuid descriptions of plasma (magnetohydrodynamics, MHD) formalism, coupled to an electrostatic ionosphere. Kinetic approaches to modeling the global magnetosphere with a coupled ionosphere system are still a rarity. We present an ionospheric boundary model for the global near-Earth plasma simulation system Vlasiator. It complements the magnetospheric hybrid-Vlasov simulations with an inner boundary condition that solves the ionospheric potential based on ﬁeld-aligned current and plasma quantities from the magnetospheric domain. This new ionospheric module solves the ionospheric potential in a height-integrated approach on an unstructured grid and couples back to the hybrid-kinetic simulation by mapping the resulting electric ﬁeld to the magnetosphere's inner boundary. The solver is benchmarked against a set of wellestablished analytic reference cases, and we discuss the beneﬁts of a spherical Fibonacci mesh for use inionospheric modeling. Preliminary results from coupled global magnetospheric–ionospheric simulations are presented, showing formation of both Region 1 and Region 2 current systems. 1 Introduction The ionosphere is the upper part of Earth's atmosphere (in an altitude range of about 80 to 1000 km), in which a signiﬁcant fraction of gas exists in an ionized state and hence electrodynamic effects are part of the atmospheric dynamics (Palmroth et al., 2021) . At the interface between magnetospheric space plasma phenomena and atmospheric physics, the ionosphere plays a key role in space weather effects (Pulkkinen, 2007), such as geomagnetically induced currents (Marshalko et al., 2023), Joule heating (Ahn et al., 1983 ; Billett et al., 2018 ; Palmroth et al., 2004) and auroral phenomena. Modeling ionospheric physics and its interaction with the magnetosphere in a global context (including the solar wind, magnetosphere and ionosphere) is therefore a research focus of computer simulations. Multiple well-established simulation systems based on ﬂuid modeling of plasma ﬂows (magnetohydrodynamics, MHD) exist, such as SWMF (Gombosi et al., 2021), GAMERA (Lin et al., 2021) or GUMICS-4 (Janhunen et al., 2012) . The large-scale morphology of ionospheric current systems is characterized by the presence of two regions of ﬁeldaligned currents (Iijima and Potemra, 1976a, b): Region 1 forms a more poleward circumpolar oval structure, whereas Region 2 is located on the equatorward side of the auroral oval. MHD-based approaches have difﬁculties representing the Region 2 currents with high ﬁdelity (Ridley et al., 2002), as they are unable to model ring current drift kinetics (Wolf et al., 2007) and overlapping multi-temperature plasmas and are hence underrepresenting the required pressure Published by Copernicus Publications on behalf of the Europea

FAQs

What does the paper contribute to Vlasiator ionosphere modeling?

It presents an ionospheric boundary model for the Vlasiator 5.2 global near-Earth simulation system. The model computes the ionospheric potential using field-aligned currents and plasma quantities from the magnetospheric domain.

How is the coupling between the magnetosphere and ionosphere implemented?

The ionosphere module solves the ionospheric potential in a height-integrated manner on an unstructured grid. It then maps the resulting electric field back to the magnetosphere’s inner boundary to affect the hybrid-kinetic simulation.

How is the solver validated and what preliminary results are shown?

The solver is benchmarked against established analytic reference cases. Preliminary coupled simulations report formation of both Region 1 and Region 2 current systems.

Aug 22, 2026

Upload by Emma Wilson