Preliminary testing of global hybrid-Vlasov simulation: Magnetosheath and cusps under northward interplanetary magnetic field M. Palmroth a,n , I. Honkonen a,b , A. Sandroos a , Y. Kempf a,b , S. von Alfthan a , D. Pokhotelov a a Finnish Meteorological Institute, Helsinki, Finland b University of Helsinki, Department of Physics, Helsinki, Finland article info Article history: Received 17 March 2012 Received in revised form 12 September 2012 Accepted 25 September 2012 Available online 18 October 2012 Keywords: Magnetosphere Global modelling Magnetosheath Cusp abstract Global magnetohydrodynamic (MHD) simulations have been successful in describing systems where the important spatial scales are larger than ion inertial length and the plasma has a well-defined temperature. The weakness of global one-fluid MHD simulations is their inability to model the multi- temperature, multi-component plasmas in the inner magnetosphere, where most of space-borne technology, including communication and navigation systems reside. We are developing a global hybrid-Vlasov simulation, where electrons are MHD fluid, but protons are modeled as distribution functions evolved in time using the Vlasov equation. This approach does not include the noise present in kinetic-hybrid simulations, but is computationally extremely challenging requiring petascale computations with thousands of cores. Here, we briefly review the status of our new parallel six- dimensional Vlasov solver. We carry out a test particle simulation and propagate the distribution functions using the electromagnetic fields of the GUMICS-4 global MHD simulation. Our main goal is to test the Vlasov solver in a global setup against the standalone GUMICS-4 global MHD simulation. The results shown here are obtained during due northward interplanetary magnetic field (IMF). We find that the magnetosheath and magnetopause plasma properties from the test particle simulation are in rough agreement with the results from the GUMICS-4 simulation. Furthermore, we show that the cusp injection patterns reproduce the expected behavior of northward IMF. The results indicate that our solver behaves sufficiently well, indicating that global hybrid-Vlasov simulations of this kind are feasible, promising improved global simulation capabilities in the future. & 2012 Elsevier Ltd. All rights reserved. 1. Introduction As space missions provide measurements from a limited volume, theoretical and numerical models are important in understanding the observed variations. Depending on the problem, the equations to be solved range from kinetic (full particle orbit calculation) to hybrid (full ion dynamics, fluid electrons) and magnetohydrodynamic (fluid equations). At present MHD simula- tions are the only feasible tool to make large-scale simulations of the near-earth space in real time or near real time, allowing also space weather forecasts with L1 input data. Several global simula- tion groups have started to improve the accuracy of their codes by coupling the MHD part with inner magnetosphere models (e.g., Huang et al., 2006). Global (including solar wind, magnetosphere, and ionosphere) hybrid simulations in three dimensions exist for non-magnetized bodies (Kallio and Janhunen, 2002), while the first somewhat limited attempts for earth-based hybrid simulations have recently emerged (Omidi et al., 2005). Ion energy dispersion with latitude across the polar cusp is an essential characteristic of cusp precipitations known to correlate with the interplanetary magnetic field (IMF) orientation. Under southward IMF conditions, near-equatorial dayside reconnection and subsequent poleward convection of the merged flux tubes causes a decreasing average energy of injected ions with increas- ing latitude as been proposed by Reiff et al. (1977). Under northward IMF conditions, lobe reconnection in the region pole- ward to the northern cusp results in a rising energy of injected particles at high latitudes causing the V-shaped dispersion, i.e. a decrease in energy followed by an increase as latitude increases (Woch and Lundin, 1992). Recent studies of cusp injections with a constellation of four Cluster satellites confirmed that the decreas- ing and the V-shaped energy-latitude dispersions are typical, respectively, for the southward and northward IMF conditions (Escoubet et al., 2008). Contents lists available at SciVerse ScienceDirect journal homepage: www.elsevier.com/locate/jastp Journal of Atmospheric and Solar-Terrestrial Physics 1364-6826/$ - see front matter & 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jastp.2012.09.013 n Corresponding author. Tel.: þ358 405311745. E-mail address: minna.palmroth@fmi.fi (M. Palmroth). Journal of Atmospheric and Solar-Terrestrial Physics 99 (2013) 41–46