[1] One of the primary goals of the Center for Integrated Space Weather Modeling (CISM) effort is to assess and improve prediction of the solar wind conditions in nearEarth space, arising from both quasi-steady and transient structures. We compare 8 years of L1 in situ observations to predictions of the solar wind speed made by the WangSheeley-Arge (WSA) empirical model. The mean-square error (MSE) between the observed and model predictions is used to reach a number of useful conclusions: there is no systematic lag in the WSA predictions, the MSE is found to be highest at solar minimum and lowest during the rise to solar maximum, and the optimal lead time for 1 AU solar wind speed predictions is found to be 3 days. However, MSE is shown to frequently be an inadequate ''figure of merit'' for assessing solar wind speed predictions. A complementary, event-based analysis technique is developed in which high-speed enhancements (HSEs) are systematically selected and associated from observed and model time series. WSA model is validated using comparisons of the number of hit, missed, and false HSEs, along with the timing and speed magnitude errors between the forecasted and observed events. Morphological differences between the different HSE populations are investigated to aid interpretation of the results and improvements to the model. Finally, by defining discrete events in the time series, model predictions from above and below the ecliptic plane can be used to estimate an uncertainty in the predicted HSE arrival times.
[1] In this paper we describe a coupled model of Earth's magnetosphere that consists of the Lyon-Fedder-Mobarry (LFM) global magnetohydrodynamics (MHD) simulation, the MIX ionosphere solver and the Rice Convection Model (RCM) and report some results using idealized inputs and model parameters. The algorithmic and physical components of the model are described, including the transfer of magnetic field information and plasma boundary conditions to the RCM and the return of ring current plasma properties to the LFM. Crucial aspects of the coupling include the restriction of RCM to regions where field-line averaged plasma-b ≤ 1, the use of a plasmasphere model, and the MIX ionosphere model. Compared to stand-alone MHD, the coupled model produces a substantial increase in ring current pressure and reduction of the magnetic field near the Earth. In the ionosphere, stronger region-1 and region-2 Birkeland currents are seen in the coupled model but with no significant change in the cross polar cap potential drop, while the region-2 currents shielded the low-latitude convection potential. In addition, oscillations in the magnetic field are produced at geosynchronous orbit with the coupled code. The diagnostics of entropy and mass content indicate that these oscillations are associated with low-entropy flow channels moving in from the tail and may be related to bursty bulk flows and bubbles seen in observations. As with most complex numerical models, there is the ongoing challenge of untangling numerical artifacts and physics, and we find that while there is still much room for improvement, the results presented here are encouraging.Citation: Pembroke, A., F. Toffoletto, S. Sazykin, M. Wiltberger, J. Lyon, V. Merkin, and P. Schmitt (2012), Initial results from a dynamic coupled magnetosphere-ionosphere-ring current model,
Using a global multifluid MHD model, we demonstrate the effects of magnetospheric O+ on bursty magnetotail flows. We carry out two simulations without ionospheric outflow to use as baseline, one driven by real solar wind data and one driven by idealized solar wind. Solar wind data from 1 October 2001 are used as a storm time solar wind driver. During this event, the plasma sheet was observed to be rich in O+, making the event of interest for a model analysis of the effects of ionospheric origin O+ on magnetospheric dynamics. We carry out outflow comparison simulations for both the realistic and idealized solar wind drivers using a simple empirical model that places auroral outflow in regions where downward propagating Poynting flux and electron precipitation are present, combined with a low‐flux thermal energy O+ outflow over the entire polar region. We demonstrate the effects of O+ on magnetotail structure and the occurrence rate and strength of bursty, fast earthward flows. The addition of O+ to the magnetotail stretches the tail and increases the velocity of bursty earthward flows. This increase is shown to be produced by reconnection events in an extended current sheet created by tail stretching.
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