First Kinetic Simulations of Equatorial Spread-F - Analysis of Kilometer-to-Meter Scale Irregularities

This AFOSR project investigated the small-scale ($$ 100 m) plasma dynamics of Convective Ionospheric Storms (CEIS), i.e. Equatorial Spread-F. CEIS cause sever degradation of earth-to-satellite communication signals (e.g. GPS) and other disruptions of communication. Our plan was to investigate the dynamics of small-scale CEIS using Particle-in-Cell (PIC) simulations and theory. All previous simulations had used large-scale fluid codes which generally ignored the important physics that occurs at scale sizes below 100 m. In order to do this, we developed our existing massively-parallel PIC simulator, adding new boundary conditions and field solvers. We then performed 2 and 3 dimensional simulations initialized with strong density gradients. We found that these gradients result in small scale drift wave instabilities perpendicular to the background density gradient. The gradient length scales required to produce these instabilities, however, are slightly smaller than those previously measured in situ by satellites and rockets. We conclude that a simple drift wave instability is sufficient to explain the development of small scale irregularities as they quickly dissipate the steepened structures that drive their growth. We are currently preparing a manuscript discussing these results.
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