REMIX (Redeveloped Magnetosphere-Ionosphere Coupler/Solver) code is a full rewrite of the MIX code (Merkin and Lyon, 2010) that was originally developed to mediate coupling between the different models within the Coupled Magnetosphere-Ionosphere-Thermosphere model (CMIT; Wiltberger et al., 2017; Lin et al., 2019) – a predecessor of MAGE. REMIX was developed for full integration with GAMERA and, like GAMERA, relies on no external libraries and uses only modern Fortran, i.e., the code is highly efficient and portable.
The basic functionality of REMIX is two-fold. First, it performs the various interpolations and coordinate transformations required for data transfers between the different participating model components. Second, it solves the ionospheric Ohm's law (current continuity) given a source of field-aligned currents, a tensor of ionospheric conductance (height-integrated conductivities) and, if available, thermospheric neutral winds. The conductances can be computed internally or provided by a model of the ionosphere-thermosphere system, such as WACCM-X or TIEGCM (e.g., Qian et al., 2014). In either case, the contribution to the conductances from magnetospheric particle precipitation is evaluated from the plasma properties in the global MHD code (e.g., Zhang et al., 2015). Recently, we have also started including the diffuse precipitation component directly from RCM electron population and mono-energetic component from GAMERA.
Once the electrostatic potential is computed, the resulting high-latitude ionospheric electric field and convection are provided to the models that require all or some of these variables (GAMERA, RCM, SAMI3, IPWM, WACCM-X).
A representative snapshot from the REMIX solution during the August 2005 geospace storm from a fully coupled GAMERA-RCM-TIEGCM simulation. The plots show significant stormtime Region 2 field-aligned currents in the ionosphere along with the plasma convection paths (left) as well as the ionospheric conductances from the TIEGCM model with the diffuse precipitation derived from RCM and mono-energetic precipitation derived from GAMERA.
Lin, D., Wang, W., Scales, W. A., Pham, K., Liu, J., Zhang, B., ... & Maimaiti, M. (2019). SAPS in the 17 March 2013 storm event: Initial results from the coupled magnetosphere‐ionosphere‐thermosphere model. Journal of Geophysical Research: Space Physics, 124(7), 6212-6225.
Merkin, V. G., & Lyon, J. G. (2010). Effects of the low‐latitude ionospheric boundary condition on the global magnetosphere. Journal of Geophysical Research: Space Physics, 115(A10).
Qian, L., Burns, A. G., Emery, B. A., Foster, B., Lu, G., Maute, A., ... & Wang, W. (2014). The NCAR TIE-GCM: A community model of the coupled thermosphere/ionosphere system. Modeling the ionosphere-thermosphere system, 201, 73-83.
Wiltberger, M., Merkin, V., Zhang, B., Toffoletto, F., Oppenheim, M., Wang, W., ... & Stephens, G. K. (2017). Effects of electrojet turbulence on a magnetosphere‐ionosphere simulation of a geomagnetic storm. Journal of Geophysical Research: Space Physics, 122(5), 5008-5027.
Zhang, B., Lotko, W., Brambles, O., Wiltberger, M., & Lyon, J. (2015). Electron precipitation models in global magnetosphere simulations. Journal of Geophysical Research: Space Physics, 120(2), 1035-1056.