Accession Number : ADP006523

Title :   Observations De Perturbations Produites Par Des Explosions Chimiques Puissantes Dans L'Ionosphere (Observations of Disturbances Produced by Powerful Chemical Explosions in the Ionosphere),

Corporate Author : COMMISSARIAT A L'ENERGIE ATOMIQUE PARIS (FRANCE)

Personal Author(s) : Blanc, Elisabeth

Report Date : OCT 1990

Pagination or Media Count : 12

Abstract : This paper describes observations by HF ionospheric sounding of disturbances produced by powerful chemical explosions (several KT). These experiments were performed at distances of about 30-40 km from the explosion point. Because of the amplification due to the atmospheric density decrease with increasing altitude , the acoustic waves from such explosions are characterized by shock wave features when they reach the ionosphere. The development of the disturbance has been studied from the lower E region up to the F2 region by using 8 sounding frequencies. We show that a blanketing sporadic E layer undergoes small scale fluctuations and becomes semi-transparent after the passage of the disturbance. Several wave fronts with different properties are followed up to the Fl region. In the lower E region, the wave induced stratifications on which the radio waves are partially reflected. The echoes totally reflected in the E region undergo an amplitude modulation with a period of about 2 seconds, persisting about 30 minutes. The variations of the total reflection height and of the Doppler frequency shift are most noticeable in the Fl region. The wave loses its shock wave feature in the F2 region and the dis signature is then that of a pseudo-sinusoidal wave with a wave length of several tens of kilo meters.

Descriptors :   *EXPLOSIONS, *IONOSPHERIC DISTURBANCES, ACOUSTIC WAVES, AMPLIFICATION, AMPLITUDE, AMPLITUDE MODULATION, ATMOSPHERIC DENSITY, ATMOSPHERICS, E REGION, ECHOES, FREQUENCY SHIFT, IONIZATION, IONOSPHERE, LENGTH, MODULATION, PAPER, RADIO WAVES, REFLECTION, SHOCK, SHOCK WAVES, SIGNATURES, SOUNDING, VARIATIONS, HIGH ALTITUDE, FRANCE, ELECTROMAGNETIC WAVE REFLECTIONS.

Subject Categories : Atmospheric Physics

Distribution Statement : APPROVED FOR PUBLIC RELEASE