Nonlocal theory of long-wavelength plasma waves associated with sporadic E layers

Journal Article · Wed Feb 01 04:00:00 EST 1989 · J. Geophys. Res.; (United States)

DOI:https://doi.org/10.1029/JA094iA02p01495· OSTI ID:6451270

Riggin, D; Kadish, A

In this paper we calculate the nonlocal growth rate of gradient drift plasma waves under conditions where the electron density gradient scale length changes with altitude. The results are compared with the local growth rate and discussed in the context of the kilometer-scale waves which have been observed in the vicinity of mid-latitude sporadic E layers. These large-scale waves drastically violate the local approximation, kL/sub m/>>1, where k is the irregularity wave number and L/sub m/ is the minimum gradient scale length on the edge of a layer. The first step in the analysis is to derive a general eigenmode equation, starting with the same assumptions usually used in the derivation of the local dispersion relation for long wavelength waves. Modeling a sporadic E layer as a slab, the nonlocal growth rate spectrum is found by solving the eigenmode equation for this profile. The solution is an algebraic dispersion relation with a growth rate spectrum which is roughly proportional to k, rather than the k/sup 2/ dependence predicted by conventional local theory at long wavelengths. At short wavelengths the nonlocal growth rate determined with the slab is unbounded, in disagreement with local theory. The slab is an inadequate model for short wavelength waves and a bound on the growth rate is instead derived from a theory which can be applied to any realistic profile with nonzero L/sub m/. At short wavelengths this bound is identical to the local growth rate expression, while at long wavelengths the bound remains proportional to k and thus is consistent with the dispersion relation for a slab. Nonlocal effects alone do not explain the dominance of kilometer scales, but they do tend to favor the excitation of long wavelengths.

• Research Organization: Atmospheric Sciences Group, Earth and Space Sciences Division, Los Alamos National Laboratory, New Mexico
• OSTI ID: 6451270
• Journal Information: J. Geophys. Res.; (United States), Journal Name: J. Geophys. Res.; (United States) Vol. 94:A2; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

640201* -- Atmospheric Physics-- Auroral
Ionospheric
& Magetospheric Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
DISPERSION RELATIONS
DRIFT INSTABILITY
E REGION
EARTH ATMOSPHERE
ELECTRON DENSITY
INSTABILITY
INSTABILITY GROWTH RATES
IONOSPHERE
PLANETARY IONOSPHERES
PLASMA INSTABILITY
PLASMA MICROINSTABILITIES
PLASMA WAVES
SPORADIC E