Influence of localized precipitation-induced D-region ionization enhancements on subionospheric VLF propagation

Thesis/Dissertation · Sat Jan 01 04:00:00 EST 1983

OSTI ID:5819433

Tolstoy, A

Short-term nighttime perturbations of the phase and amplitude of very-low-frequency (VLF: 10-30 kHz) radio wave transmissions propagating in the earth-ionosphere waveguide have been observed to correlate with the coincident occurrence of magnetospheric whistler/noise emissions. These signal perturbations are believed to be caused by the whistler/noise induced precipitation of energetic electrons into the ionospheric D-region. The location and extent of these precipitation regions as may be deduced by model predictions of subionospheric radio wave propagation are examined. A two-dimensional propagation model has been used extensively to investigate the effects of various configurations of localized ionospheric perturbations on the VLF radio waves. It is based upon Maxwell's equations for electromagnetic wave propagation within a waveguide where the earth's surface comprises the lower boundary (with varying conductivity and permittivity) and where the ionosphere comprises the upper boundary (diffuse, dissipative, inhomogeneous and anisotropic). The mathematical foundation of the model is shown to be related to the ideas of invariant embedding. Model computations have been performed for a number of transmitter-receiver paths in an effort to deduce the geometry of actual perturbation regions. The particular regions of disturbance being modeled have been hypothesized to exist and to thereby account for a range of observed signal amplitude changes. Calculations have shown that in order to obtain the very large amplitude increases observed in the data, two regions of localized D-region ionization enhancement, one near the transmitter and one near the receiver, must exist simultaneously. It is hypothesized that the former is due to transmitter induced electron precipitation while the latter is due to precipitation associated with the whistler.

• OSTI ID: 5819433
• Country of Publication: United States
• Language: English

Related Subjects

640201* -- Atmospheric Physics-- Auroral
Ionospheric
& Magetospheric Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
D REGION
EARTH ATMOSPHERE
ELECTROMAGNETIC RADIATION
FREQUENCY RANGE
IONOSPHERE
KHZ RANGE
NOISE
PLANETARY IONOSPHERES
RADIATIONS
RADIO NOISE
RADIOWAVE RADIATION
VARIATIONS
WAVE PROPAGATION
WHISTLERS