# Accession Number:

## ADA207975

# Title:

## Effects of Magnetic and Collisional Viscosity on the E x B Gradient Drift Instability

# Descriptive Note:

## Memorandum rept.

# Corporate Author:

## NAVAL RESEARCH LAB WASHINGTON DC

# Personal Author(s):

# Report Date:

## 1989-04-27

# Pagination or Media Count:

## 43.0

# Abstract:

The role of magnetic viscosity i.e., Larmor radius effects and collisional viscosity on the Ex B gradient drift instability is investigated in both the collisional and inertial regimes. The equations describing the time evolution of small perturbations to an equilibrium two dimensional x,y magnetized plasma are derived where the equilibrium electron density is an arbitrary function of y. The equations are then solved iteratively in time to obtain the growth rate of the fastest growing eigenmode for a given Fourier wavenumber k in the x direction. We compare our results for appropriate profiles with two asymptotic results the long wavelength limit, valid for kL 1, and the short wavelength or local limit, valid for kL 1, where L is the gradient scale length of the equilibrium profile. It is found that although the long and short wavelength limits do indeed provide accurate growth rates for kL 1 and kL 1, respectively, neither provides reliable growth rates for kL approx. 1. In comparing these results to the long wavelength limit, in addition to affecting gamma in an absolute sense, increasing L to a finite value decreases k sub max, the value of k for which gammak maximizes, and also affects the sharpness of the peak of gammak about k sub max. Both of these phenomena have large effects on freezing models.

# Descriptors:

- *IONOSPHERIC DISTURBANCES
- *NUCLEAR CLOUDS
- GROWTH(GENERAL)
- PLASMAS(PHYSICS)
- ELECTRON DENSITY
- ACCURACY
- EQUILIBRIUM(GENERAL)
- RELIABILITY
- PROFILES
- FREEZING
- LIMITATIONS
- SCALE
- LENGTH
- PERTURBATIONS
- INERTIAL SYSTEMS
- IONOSPHERIC MODELS
- LONG WAVELENGTHS
- MAGNETIZATION
- VISCOSITY
- BARIUM
- SHORT WAVELENGTHS
- RADIUS(MEASURE)
- COLLISIONS
- GRADIENTS
- STABILITY
- CLOUDS
- MAGNETIC FIELDS

# Subject Categories:

- Atmospheric Physics
- Plasma Physics and Magnetohydrodynamics