Ionospheric VLF waves and optical phenomena over active thunderstorms. [VLF (very low frequency)]

Thesis/Dissertation · Fri Jan 01 04:00:00 EST 1993

OSTI ID:6924391

Li, Y Q

In 1987 and 1988, two campaigns, the Wave Induced Particle Precipitation campaign and the Thunderstorm II campaign, were conducted to investigate lightning-generated effects in the upper atmosphere and ionosphere. Two rockets and 6 balloons were launched near thunderstorms in these campaigns. Optical and electrical signals from hundreds of lightning strokes were recorded. The author has been able to study some problems about lightning-generated VLF waves in the ionosphere which have not been well investigated previously. This dissertation reports the following: (1) The downward-looking optical detector on the rocket recorded some anomalous characteristic optical phenomena. (2) The author studied the relation between the amplitude of lightning-generated VLF waves in the ionosphere and the lightning current recorded by the SUNYA lightning network. This study shows that the amplitude of waves at frequencies below 5 kHz has linear response to the lightning current. (3) The author has been able to determine the propagation path of the lightning-generated VLF waves from the source to the rocket. The path is consistent with the leaky waveguide hypothesis. (4) The amplitude of lightning-generated VLF waves has been found to have maxima and minima at different altitudes, instead of being attenuated monotonically with altitude as expected. A theoretical model has been proposed which shows that the wave amplitude profiles are the result of interference between waves from an aperture area below the rocket. (5) The author numerically calculated the absorption of VLF waves at the bottom of the ionosphere. The electron density gradient of the ionosphere was taken into account. The characteristics of the absorption, such as the frequency dependence, were investigated. The author deduced that significant heating of the ionosphere is caused by lightning-generated VLF waves.

• Research Organization: Washington Univ., Seattle, WA (United States)
• OSTI ID: 6924391
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
540110
661320* -- Auroral
Ionospheric
& Magnetospheric Phenomena-- (1992-)
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
DISASTERS
EARTH ATMOSPHERE
ELECTRIC DISCHARGES
ELECTRO-OPTICAL EFFECTS
ELECTROMAGNETIC RADIATION
HEATING
IONOSPHERE
LIGHTNING
LONG WAVE RADIATION
METEOROLOGY
PLANETARY IONOSPHERES
RADIATIONS
RADIOWAVE RADIATION
STORMS
WAVE PROPAGATION
WEATHER