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Rice Convection Model


CCMC Services available for RCM
Request a Run

Model Developer(s)
Stanislav Sazykin, Richard A. Wolf
Department of Physics and Astronomy, Rice University

Model Description
The Rice Convection model (RCM) is a bounce averaged-drift kinetic model of the ring current and inner plasma sheet and their coupling to the ionosphere. It assumes an isotropic distribution function for all magnetospheric particles and calculates the temporal and spatial variation of the phase space density in the inner-plasma-sheet and ring current. The model considers particle drift in an inputted, time varying magnetic field, and a self consistent potential electric field that is computed taking into account current closure in the ionosphere.

The particle population in the inner magnetosphere is represented by three species (H+, O+, and electrons); in addition, a model plasmasphere is included. RCM solves a special form of the collisionless Vlasov equation for the distribution function of the three species that includes transport due to ExB and gradient/curvature drifts. The source terms include inflow through the outer boundary, the losses are due to boundary outflows and charge-exchange (for H+ and O+) with neutral hydrogen of geocorona. For the plasmasphere, parameterized refilling is included as a source term. The potential electric field used in the transport equations is obtained self-consistently by solving the current-conservation equation. Divergent drift currents are allowed to close through the ionosphere via field-aligned (Birkeland) currents and horizontal Pedersen and Hall ionospheric currents. Both potential and induction electric fields are included in the transport equations.

The transport equations and the current-conservation equation are solved on a high-resolution ionospheric polar orthogonal grid. The standard grid offered through runs on request has grid spacing that is uniform in local time (0.25 hrs MLT resolution). Latitudinal grid spacing varies from about 0.1 degrees in the auroral zone to about 2 degrees close to the equator. The modeling region is set to be an ellipse in the equatorial plane that extends near the magnetopause on the dayside and about twice the standoff distance in the tail. The location of the boundary is mapped to the ionosphere (where it is not aligned with the grid) and varies throughout simulations as the magnetic field is time-dependent. The equatorward/earthward boundary is at L=1.05 (~10 degrees latitude).

In solving the potential equation, the conductance tensor has two contributions. The solar EUV-produced "background" ionosphere is represented by the empirical IRI-90 model. Auroral enhancements due to energetic particle precipitation are evaluated from the computed magnetospheric distribution function assuming loss rates that are a fraction of the strong pitch-angle scattering limit rate, and conductance values are estimated using the expressions of Robinson et al. (1987).

The basic theory of the equations that RCM solves is described in detail in [Wolf, 1983; Toffoletto et al., 2003]. Some of the physics studied with the RCM can be found in [Sazykin et al., 2002; Wolf et al., 2007].

Model Input
Many input models feed boundary conditions and other necessary information into the RCM, which provides opportunity for a great deal of computer experimentation, but at the cost of complexity. For runs on request, sensible default models and options are used to provide most of the input parameters, so that the model can be run with only a few input parameters. In the future, developers and CCMC plan to implement additional user options that will become available for runs on request.

Specifying time history of the solar wind speed and density, interplanetary magnetic field, and Dst, Kp, and ABI indices will be sufficient to obtain plasma boundary conditions and polar cap potential and drive the magnetic field model. These will all be automatically supplied by CCMC when the desired event interval is specified.

In the CCMC implementation, the magnetospheric particle distribution is represented by 85 invariant-energy channels for H+, 85 channels for O+, and 29 for electrons. (Invariant energy is particle energy times (flux tube volume)^2/3.) One channel is set aside for cold plasmaspheric particles. The invariant energy channels cover energies from about 0.05*kT to 10*kT in the inner plasma sheet.

Model Output
RCM raw output consists of time history of the full distribution function of all three species, as well as electric and magnetic fields, currents, and auroral particle precipitation. For runs on request, typical output available to the user will be:

These quantities may be displayed in one of the two forms: two-dimensional ionospheric projections (polar plots in colatitude-MLT coordinates of the two hemispheres viewed from above the pole), or magnetospheric plots displayed in the equatorial plane by mapping the solutions along magnetic field lines.

Limitations and Caveats

For options and output results not available through the runs on request interface, the user is strongly encouraged to contact the developers.

References and relevant publications

CCMC Contact(s)

301-286-1085

National Aeronautics and Space Administration Air Force Materiel Command Air Force Office of Scientific Research Air Force Research Laboratory Air Force Weather Agency NOAA Space Environment Center National Science Foundation Office of Naval Research

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