Abstract
Abstract. Among the many challenges facing the space weather modelling community today, is the need for validation and verification methods of the numerical models available describing the complex nonlinear Sun-Earth system. Magnetohydrodynamic (MHD) models represent the latest numerical models of this environment and have the unique ability to span the enormous distances present in the magnetosphere, from several hundred kilometres to several thousand kilometres above the Earth's surface. This makes it especially difficult to develop verification and validation methods which posses the same range spans as the models. In this paper we present a first general large-scale comparison between four years (2001â2004) worth of in situ Cluster plasma observations and the corresponding simulated predictions from the coupled Block-Adaptive-Tree-Solarwind-Roe-Upwind-Scheme (BATS-R-US) MHD code. The comparison between the in situ measurements and the model predictions reveals that by systematically constraining the MHD model inflow boundary conditions a good correlation between the in situ observations and the modeled data can be found. These results have an implication for modelling studies addressing also smaller scale features of the magnetosphere. The global MHD simulation can therefore be used to place localised satellite and/or ground-based observations into a global context and fill the gaps left by measurements.
Highlights
The Earthâs magnetosphere is a highly complex nonlinear system mainly influenced by the interaction of the solar wind with the terrestrial magnetic field
In respect to the results presented by Daum and Wild (2006); Hayosh et al (2003, 2006); Koval et al (2006) we have computed different simulation runs with varying densities and have compared the location of the magnetopause in these simulation runs with actual Cluster magnetopause crossings
Overall it can be said that the global magnetosphere (GM)/inner magnetosphere (IM)/ionospheric electrodynamic (IE) coupled MHD model plasma predictions, without a two-way coupling to the Comprehensive Ring Current Model (CRCM), represent the plasma pressure observations reasonable well in all major regions for L>4 RE, considering the above mentioned instrument and model limitations
Summary
The Earthâs magnetosphere is a highly complex nonlinear system mainly influenced by the interaction of the solar wind with the terrestrial magnetic field. For the times where the Cluster orbit swept over the dayside magnetosphere region, highlighted in Fig. 3 by the underlying grey areas, additional fixed input boundary model runs with an averaged dipole tilt of â11.68⊠(calculated from the daily dipole tilts in the time from January to April of each year) were performed These runs were used for an initial comparison of the magnetopause shape and location in the model and the data in order to give a first implication if the presented constraining factor (50% density decrease) is applicable. The first step develops and evaluates the constraining factor used for the model runs and the second builds upon this factor to present a first general large-scale comparison of the Cluster observations and the coupled MHD model run predictions
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