Spectral Studies of Farley-Buneman Waves in the Auroral E-Region from a New Generation of High-Resolution Simulations

Details Spectral Studies of Farley-Buneman Waves in the Auroral E-Region from a New Generation of High-Resolution Simulations Spectral Studies of Farley-Buneman Waves in the Auroral E-Region from a New Generation of High-Resolution Simulations

May 2005

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2005agusmsa21a..08o&link_type=abstract

American Geophysical Union, Spring Meeting 2005, abstract #SA21A-08

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Computation

2407 Auroral Ionosphere (2704), 2439 Ionospheric Irregularities, 2471 Plasma Waves And Instabilities, 2483 Wave/Particle Interactions

Scientific paper

In the auroral electrojet, strong ambient DC electric fields drive the Farley-Buneman instability that creates plasma density irregularities responsible for type 1 radar echoes. These irregularities have been studied experimentally and theoretically for five decades. In the last decade, numerical simulations became an important tool in exploring the nonlinear behavior of E-region instabilities. However, these simulations were limited to 2-D and meshes resolving only 4096 (64 by 64) modes. Today, taking advantage of modern, massively parallel, supercomputers, we can resolve over 262,144 (512 by 512) modes in 2-D or over a million modes in 3-D. In this paper, we describe the spectra of type 1 waves from these high-resolution simulations and how they relate to measurements of electrojet spectra made by radar and rockets. In 2-D, our simulator modeled electron dynamics with an adiabatic, inertial, fluid solver while resolving ions kinetically with a particle-in-cell method (PIC). We ran a set of simulations appropriate for the auroral E-region. In all cases, the phase velocity of the most energetic modes lies well below the linearly predicted phase velocity. We see that for short wavelengths (< 1m), the dominant mode maintains a roughly constant phase velocity as the angle with respect to the drift direction increases from 0° to nearly ± 90° while for longer wavelengths in the system (> 6m), the phase velocity shows more complex behavior. In 3-D, our latest generation simulations model both electrons and ions with kinetic algorithms. This allows us to explore thermal effects with great accuracy but requires us to resolve the system Debye length and electron gyrofrequency, limiting our total resolution. Nevertheless, we see similar spectral features similar to those described in the 2-D system and we observe coupling to modes with a small component parallel to the geomagnetic field. Finally, we measure wave driven electron heating, a phenomena clearly observed by radars. Work was supported by NSF Grants ATM- 0332354 and ATM-0442075. Essential computational support was provided by the SCV and CCS at Boston University.

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