M-I Coupling: Physics Based Algorithm for the High Latitude Conductance and Its Implications

University Of Maryland, College Park, College Park MD

Investigators

Abstract

The objective of this research is to develop a physics-based module of the ionospheric conductivity that incorporates anomalous heating due to the electrojet instability driven by strong convection electric fields in the ionosphere. Reliable dynamic ionospheric conductance and energy dissipation modules covering the entire range of the solar wind input are critical elements in the construction of global electrodynamic ionosphere-magnetosphere models, such as the Geospace General Circulation Model (GGCM), the Global Ionospheric Model (GIM) and the TIME-GCM Model. Furthermore, they are critical in the representation of the ionospheric boundary in global magneto-hydrodynamic codes. A semi-empirical model based on a simple prescription is used in the LFM model, while an assimilation model, the Assimilating Mapping of Ionospheric Electrodynamics (AMIE) is the frontrunner for incorporation to the GGCM. The modeling and comparison with data shows that the above models perform well under conditions of moderate (< 20 mV/m) local ionospheric electric fields. Under strong (> 20 mV/m) local ionospheric electric fields, an important energy dissipation mechanism due to the electron Hall current becomes important. This process is not included in the traditional ionospheric electrodynamic energy budget, since the current and the electric field are orthogonal to each other. The dissipation is thus anomalous and is attributed to well known and experimentally documented Farley-Buneman two-stream electrojet instability. Electron temperatures in excess of 2000 K have been observed by the EISCAT radar and earlier by the Chatanika radar at E-region altitudes. The process, in addition to acting as a non-Ohmic dissipation, results in changes in the Pederson and Hall conductances by modifying the electron recombination coefficient and thus increasing the resultant plasma density. In this study, appropriate algorithms will be developed for incorporation in the AMIE, GIM, TIME-GCM and to global MHD codes. The new conduction module will be disseminated to the broader space science community to assess its ability to represent the observed saturation of the polar cap potential. The most challenging aspects of this research are the treatment of cross scale coupling and the incorporation of collisionless microphysics effects into fluid and electrodynamic models in the form of anomalous transport. The study will expose students to interdisciplinary research because it involves computer simulations and modeling with applications to fusion and plasma physics, meteorology, and overall to studies of complex physical and biological systems.