The ambient solar wind controls the propagation properties of Coronal Mass Ejections (CMEs) in the interplanetary space. It is therefore crucial to resemble realistic ambient conditions in the solar ...corona and inner heliosphere when modeling a space weather event from the Sun to the Earth. Traditionally, the solar wind acceleration is treated in global MHD models through (1) empirical source terms, (2) the WKB approximation of Alfven turbulence, or (3) by using a non-uniform polytropic index distribution. Here, we adopt the latter approach to drive the solar corona and the inner heliosphere modules of the Space Weather Modeling Framework (SWMF). Assuming the Bernoulli integral conservation along a magnetic field line, the value of the polytropic index at the base of the corona can be related to the asymptotic value of the solar wind speed at large distances form the Sun. This allows us to prescribe the distribution of the polytropic index as a function of the ultimate solar wind speed and the radial distance from the Sun. In our model, we calculate the self-consistent MHD steady-state solution using the polytropic index distribution in the energy equation. The input for the final solar wind speed is obtained by employing either the empirical Wang-Sheeley-Arge (WSA) model, or the physics-based Fisk model (i.e., by calculating the Pointing flux at the base of the corona). We present results of the obtained steady-state solutions, and we compare the two solar wind inputs.
The interaction of multiple CMEs has been detected by LASCO C2 and C3 and by the Wind/ACE spacecrafts. It is also thought to be associated with large Solar Energetic Particles events and enhanced ...radio II bursts. New and future missions such as STEREO, Sentinels, and Solar Orbiter should provide additional observations of the interaction of multiple CMEs between the Sun and the Earth. We will present the results of simulations of two and more CMEs interacting in the heliosphere done with the Space Weather Modeling Framework. We will discuss the observational evidence of their interaction (both in situ and from coronographs). The importance of having multiple spacecrafts at different distances and angular positions from the Sun will be emphasized.
We summarize the theory and modeling efforts for the STEREO mission, which will be used to interpret the data of both the remote-sensing (SECCHI, SWAVES) and in-situ instruments (IMPACT, PLASTIC). ...The modeling includes the coronal plasma, in both open and closed magnetic structures, and the solar wind and its expansion outwards from the Sun, which defines the heliosphere. Particular emphasis is given to modeling of dynamic phenomena associated with the initiation and propagation of coronal mass ejections (CMEs). The modeling of the CME initiation includes magnetic shearing, kink instability, filament eruption, and magnetic reconnection in the flaring lower corona. The modeling of CME propagation entails interplanetary shocks, interplanetary particle beams, solar energetic particles (SEPs), geoeffective connections, and space weather. This review describes mostly existing models of groups that have committed their work to the STEREO mission, but is by no means exhaustive or comprehensive regarding alternative theoretical approaches.
Physics-based models of the space environment provide valuable information on the processes that occur. Gross understanding of the basic properties of environment can be made with simplified models, ...such as 1- and 2-dimensional spatial codes, or codes that make assumptions about the system that reduces the computational burden. This talk will discuss some of the various compromises that are typically made in modeling different regions of the space environment, such as the ionosphere, inner magnetosphere, outer magnetosphere, and the solar corona, for the sake of run-time. The parallelization of codes and the increased physics that this enables will further be discussed. Finally, new computational technologies that reduce the run-time of simulations will be touched upon.
We use a global MHD model of the Earth magnetosphere to study convection in the Earth ionosphere. This convection is ultimately driven by the magnetic reconnection processes. We find that the ...magnetic field topology in our model is consistent with the classical null-separator model of Dungey and Cowley, and with anti-parallel reconnection scenario. We identify observable ionospheric convection patterns, predicted by our model, which include so- called lobe convection cells, circulating entirely inside the polar cap in the summer hemisphere, and reciprocal cells, circulating entirely in the closed field line region in the winter hemisphere. We show examples of events (July 11, 2000 and December 4, 2000) when such patterns were, in fact, observed with SuperDARN radars and DMSP satellites. We also present initial results of a similar modeling study for pure IMF By case, which are also consistent with the null-separator model.
This study is an extension of our previous high-performance storm simulation with the coupled BATS-R-US (Block Adaptive Tree Solar-wind Roe-type Upwind Scheme) global magnetohydrodynamics (MHD) ...model, Rice Convection Model (RCM), and Ridley Ionosphere Model (RIM). In this work, the superposed epoch recovery phase of 34 moderate storms at solar maximum (July, 1999 - June, 2002) is simulated for averaged upstream solar wind conditions with the standalone RCM and also with the coupled codes. Superposed epoch averages of it Dst, it Sym-H, and the Los Alamos Magnetospheric Plasma Analyzer (MPA) observations at geosynchronous orbit are used to validate the modeling results. In addition, parameters in the standalone RCM and the coupled codes are adjusted to systematically study the effects of interchange instability, charge exchange rate, particle drift intensity, and particle energy levels on the ring current decay. Computer experiments will also explore how magnetic field changes and time-dependent plasma-sheet density affect the recovery phase.
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