Low-altitude Nuclear Explosions Research Articles

Numerical simulation of the ionization effects of low-and high-altitude nuclear explosions

Low-altitude and high-altitude nuclear explosions are sources of intensive additional ionization in ionosphere. In this paper, in terms of the ionization equilibrium equation system and the equation of energy deposition of radiation in atmosphere, and considering the influence of atmosphere, the temporal and spacial distribution of ionization effects caused by atmospheric nuclear detonation are investigated. The calculated results show that the maximum of additional free electron density produced by low-altitude nuclear explosion is greater than that by the high-altitude nuclear burst. As to the influence of instant nuclear radiation, there is obvious difference between the low-altitude and the high-altitude explosions. The influence range and the continuance time caused by delayed nuclear radiation is less for the low-altitude nuclear detonation than that for the high-altitude one.

Disturbances in the lower ionosphere caused by a low altitude nuclear explosion

Observations of the lower ionospheric disturbance caused by a low altitude nuclear explosion are presented. A forward scatter radar, frequency 41 MHz, power 2.5 kW, was used to study these disturbances. The first radar scattering signal consisting of three peaks appeared 40 s after the explosion. It was due to early ionization by delayed y-rays. The second kind of disturbance generated after 190 s was clearly different from the first. The scattering signal had a constant component which indicated a strong specular reflection. The field strength increased by more than 20 db. This disturbance was produced by the direct shock wave. The third kind of disturbance began after 8 min, lasted 5.0 min, and was probably dominated by the fireball/smoke cloud oscillation when it reached its stabilization altitude and approached hydrodynamical equilibrium with the ambient atmosphere. Using numerical computation techniques, we have explained the above results well.

Wilson Cloud formation by low-altitude nuclear explosions

A model of Wilson Cloud formation following a low-altitude nuclear detonation is developed. It is shown that, for detonation yields between 10−3 kt and 100 kt, simple scaling laws characterize the evolution and physical properties of the Wilson Cloud.

The production of nitrogen oxides by low-altitude nuclear explosions

Hydrodynamic and chemical kinetic calculations are used to show that megaton (Mt) nuclear explosions near the ground produce, in the air that is shocked above 2200°K and quickly cooled by expansion, 0.8×1032 NO molecules/Mt. Inside this region the air is still so hot that further production or destruction of NO may take place. An upper limit to the production is obtained by assuming that the hot inner air mixes with undisturbed air, producing an additional 0.7×1032 NO molecules/Mt, giving a total of 1.5×1032 NO molecules/Mt. A lower limit is obtained by assuming that during the fireball rise all of the shocked air containing NO is entrained and mixed into the hotter air, and slow cooling of the mixture reduces the total NO to 0.4×1032 molecules/Mt.

Group Velocities of Atmospheric Gravity Waves

Atmospheric gravity waves generated by low-altitude nuclear explosions have been detected by ground-level microbarographs and by ionospheric instruments. Group velocity dispersion curves have been computed for propagation over the short and long great-circle paths. Apparent lower velocities over the short paths are interpreted as due to the “rise time” of the nuclear disturbances to ionospheric levels with subsequent generation of gravity waves at those levels. Corrections to the travel times to account for the “rise time” delays are estimated to be ∼13 min or more. Corrected group velocity dispersion curves are found to agree with theoretical group velocity dispersion for atmospheric surface waves.

The Design Of Complex Systems To Resist The EffectsOf A Nuclear Explosion

The design of complex systems subject to the effects of a nuclear explosion is a critical issue, particularly due to the variety of phenomena generated by the explosion. The major effects which are to be considered in a low altitude nuclear explosion include: mechanical effects, thermal effects, nuclear radiations, and electromagnetic pulse. The discipline concerned with analysis, design and production of systems to resist the effects of a nuclear explosion is termed Nuclear Hardening. The paper provides an overview on the effects of a nuclear explosion and on the consequences that they can have on complex systems. The methodology applicable to weapon systems such as tanks, armoured vehicles and war ships, is described.

A comparative study of ground-pressure waves in various atmospheric models

Dispersion curves and stationary phase contributions to theoretical ground-pressure waves from low-altitude nuclear explosions are presented for model atmospheres containing winds. Comparison is made with previously published results. It is shown that the reflection of waves above an altitude of 120 km can result in certain effects in waves with periods greater than 5 minutes. These effects are readily observable in microbarographic records associated with nuclear explosions. It is shown that winds can have a pronounced effect on wave characteristics at periods between 1 and 10 minutes. It is concluded that the effects of low-atmospheric winds are best observed in the behavior of waves of periods less than 4 minutes. Details are given of the numerical procedures followed in obtaining results.

A spatial model of theF-region ionospheric traveling disturbance following a low-altitude nuclear explosion

The ƒoF2 fluctuations observed by means of vertical-incidence ionosondes at various Pacific Island stations following the low-altitude, megaton-range nuclear explosion on October 30, 1962, were analyzed. By accounting for the influence of the earth's magnetic field on the response of the ionosphere to the passage of the neutral atmospheric gravity wave (AGW) disturbance, the properties of the neutral AGW disturbance were determined as a function of time after the explosion and distance from the explosion. It was found that the average period of the neutral AGW increases linearly with range, with an additive constant; this constant is related to the initial period of a virtual source located within the ionosphere above the point of the explosion (G0). The amplitude of the neutral AGW varies as exp(−kr), where r is the range from the explosion. Isoionic contours of the ΔN/N fluctuations were computed. Four cases of the expanding ionospheric disturbance are given, for 22, 44, 65, and 109 minutes after the explosion; these times correspond to the expansion of the leading edge of the neutral AGW to 1000, 2000, 3000, and 50000 km from the explosion. The Housatonic data agree well with the published theoretical papers on AGW's generated by impulsive, low-altitude sources.

Response of the ionosphere to the passage of acoustic-gravity waves generated by low-altitude nuclear explosions

The response of the bottomside ionosphere to the passage of acoustic-gravity waves generated from a large low-altitude explosion (Housatonic) has been observed by means of vertical-incidence ionosondes. Acoustic-gravity wave disturbances propagated essentially horizontally away from the detonation point (G0) with velocities of 610 and 362 m/sec corresponding to the first and second positive peaks of the disturbance. The disturbance was first sensed at each station at times corresponding to 765 m/sec. They were detected up to 4000 km from G0. The geomagnetic field played an important role in the ionosphere response of these gravity waves. For those stations located north of G0 and those south of the geomagnetic equator (group I stations) ionization first slid down the magnetic field lines; whereas, for stations south of G0 but north of the geomagnetic equator (group II stations) ionization was first forced to move up the magnetic field lines. In both cases fluctuations in ionization density at a given height were observed. Considering the height and shape of the ionosphere, the ionization migration caused (1) the ƒ0F2 peak height hm to be lowered as much as 105 km as the disturbance reached its first positive peak overhead and the bottomside ionosphere to be flattened out for group I stations and (2) the opposite behavior for group II stations as the ƒ0F2 disturbance reached its first negative peak. Ionosondes located at distances from 450 to 4000 km from G0 observed fluctuations in electron concentration which at their first peak excursions reached from −20% (for group II stations) to +68% (for group I stations). The observed ƒ0F2 fluctuations appear to fit an approximate theoretical formula especially with regard to their magnetic field direction and amplitude-period dependence. Ionosonde data following the near-surface 58 Mt explosion on October 30, 1961, at Novaya Zemlya also fit this theory.

On the nature of traveling ionospheric disturbances launched by low-altitude nuclear explosions

The nuclear explosion of October 30, 1961, over Novaya Zemlya, resulted in major perturbations of the F-layer critical frequency, even at very great ranges from the explosion site. These perturbations have been interpreted in terms of long-period gravity waves, and more recently in terms of shorter-period acoustic-gravity waves. It is shown here that the new interpretation is unsatisfactory, while the old is perfectly consistent with the observations if allowance is made for the obliquity of energy propagation. The results have some bearing on natural traveling ionospheric disturbances as well.

The atmospheric pressure wave generated by a nuclear explosion: 1.

The problem of describing the pressure wave detected by an observer on the ground a few thousand kilometers from a low-altitude nuclear explosion is formulated. To avoid numerical complications, the atmosphere is assumed to have an isothermal temperature distribution. With this simplification a Green's function for the problem is developed as an expansion in Legendre polynomials. This representation yields a time-dependent pressure function which satisfies the condition of causality but which converges far too slowly to be useful. An alternative scheme, which is entirely equivalent, makes use of a Watson transformation and requires the determination of the set of Regge poles. The behavior of the complete Green's function is then shown to be dominated by the so-called gravity wave mode, and the form of this approximate solution is developed.

Effects of propagation on the high-frequency electromagnetic radiation from low-altitude nuclear explosions

The high-frequency electromagnetic pulse radiation from nuclear explosions presents a possible detection mechanism. This paper first considers the selective attenuation of the higher-frequency components of the pulse when it travels via ground wave, and shows how the waveform is modified with distance. Effects of the height of the source are included. Propagation via sky wave is investigated, and it is demonstrated that ionospheric dispersion considerably stretches the pulse for reasonable propagation distances. The receiver bandwidth should be selected to match the ionospheric dispersion at the receiver frequency.

Low-altitude nuclear test and radio noise level

Low-altitude nuclear explosion around Reganne (26°N, 0°E) in the Sahara Desert during February, 1960 had effect on radio communication at Ibadan (7°N, 4°E) about 2,000 km from the region of detonation. The nuclear weapon was believed to have been in the kiloton range and exploded from a 300-ft tower. Increased ionization in the ionosphere and enhancement of atmospheric radio noise levels were evidenced at Ibadan. The atmospheric noise levels at all frequencies investigated were affected but the effects were rather more pronounced at the lower frequencies.The results of the observations suggest that the explosion itself generates electromagnetic energy at least in the radio-frequency band, 51 kc/s-20 Mc/s.