Kwajalein Research Articles

On the spatial relationship of 1‐m equatorial spread F irregularities and plasma bubbles

A radar experiment was conducted on August 18, 1978, at Kwajalein Atoll, Marshall Islands, to investigate the spatial relationship of 1‐m equatorial spread F irregularities to plasma bubbles (localized depletions in F layer plasma density). East‐west scans were made with Altair, an incoherent scatter radar, to spatially map (1) the backscatter produced by field‐aligned irregularities and (2) the electron density distribution of the background F layer. Plasma bubbles were spatially mapped for the first time with an incoherent scatter radar. By assuming invariance along the magnetic field lines (over distances of less than 100 km) we show that 1‐m field‐aligned irregularities are directly related to plasma bubbles.

Altair: an incoherent scatter radar for equatorial spread F studies

We report preliminary results on 1‐m equatorial spread F irregularities obtained with a high‐power VHF backscatter radar located at equatorial latitudes. The field experiment was conducted at Kwajalein Atoll, Marshall Islands, during August 1977. The examples, which include both incoherent scatter measurements and backscatter from equatorial spread F irregularities, illustrate the usefulness of a fully steerable radar for equatorial spread F studies. The backscatter observations at 155.5 MHz are not consistent with the scattering model proposed by Woodman and Basu (1978), which includes a cutoff near the ion gyroradius. The results obtained thus far also indicate that the collisional Rayleigh‐Taylor instability is probably the principal mechanism producing equatorial spread F.

Plutonium concentrations in fish and seawater from Kwajalein Atoll.

A follow-up study has been made to assess the concentrations of 239+240Pu and 137Cs in the marine environment of Kwajalein Atoll. Fish collected from the atoll in 1972 had body burdens of plutonium that were substantially higher than concentrations in similar species from locations contaminated only with global fallout. Our recent results, however, indicated that Kwajalein lagoon seawater contained levels of plutonium more similar to global fallout levels found in north equatorial Pacific surface waters. No satisfactory explanation for the reported plutonium levels in fish from Kwajalein collected in 1972 could be deduced from the available data. The highest plutonium concentrations reported for the 1972 reef species of fish could expose man, through ingestion of marine foods, to a dose rate as high as 25% of the proposed EPA guideline for annual total transuranic dose rate to bone (3 mrad/yr over 70 yr). Our present results show the dose rate from the marine food pathway is nearer to 0.005% of the recommended EPA value and is consistent with the view that Kwajalein Atoll contains plutonium concentrations that are expected from global fallout. The magnitude of the plutonium levels reported in fish collected from Kwajalein lagoon during 1972 was excessively high, and these results appear to be inconsistent with other environmental data from the lagoon. Our results also show that concentration factors for plutonium in fish muscle and bone tissues appear to be independent of species, trophic level and location, which leads us to believe that there is a great deal of validity in the concept of a concentration factor for estimating concentrations of plutonium in fish.

Plutonium levels in Kwajalein Lagoon

Reported plutonium levels in fish from both Kwajalein and Enewetak lagoons, suggest that Kwajalein Lagoon contains significantly more plutonium in its environment than would be expected from worldwide fallout levels alone, although quantities of plutonium greater than fallout concentrations have not been detected in the lagoon water. If there is no reason to reject the published fish data, then individuals on Kwajalein Atoll who supplement their diet with foods from the local marine environment may have plutonium body burdens similar to the low levels predicted for individuals on similar diets at Enewetak Atoll.

Control of radar site environment by use of fences

Electrically-opaque fences have been found to be a versatile means of controlling radar site problems such as clutter return and ground reflections; they have also been used to reduce the power density in the radar vicinity in order to prevent a personnel hazard. Such fences have been designed for several existing radar installations at the White Sands Missile Range and at Kwajalein Island in the Pacific. In these applications, the function of the fence is to block undesired signal paths. However, the improvement achieved by the use of a fence is limited by the fields diffracted over the fence edge. The effects of this diffraction are calculated on the basis of straight-edge diffraction theory. Generally, the fence design is a compromise between performance and cost, large-radius fences providing better performance than smaller ones. Techniques are presently being investigated for obtaining improved performance by the treatment of the top edge of the fence to further control the diffraction.

Anomalous high-frequency propagation after the Soviet nuclear test of October 30, 1961

The three-frequency IGY auroral radar located at Thule, Greenland, was monitored during part of 1961 at several sites. Anomalous propagation conditions were detected after the large Soviet nuclear test at Novaya Zemlya on October 30, 1961, in which a propagation path was created between Thule and Kwaj alein Atoll for 12-Mc/s signals and apparent off-great circle paths were produced for 12; 18, and 30-Mc/s transmissions. The Thule radar signal is radiated by a set of Yagi antennas mounted in common on a mast which rotates approximately 1 rpm. The unit thus successively scans 360° in azimuth around Thule and produces, under normal conditions, a signal variation approximating a rectified sinusoid at a distant fixed receiving site. The half cycles are of alternating amplitude dependent on the front to back ratio of the radiation pattern of the transmitting antenna. The receiving instrumentation was composed of communications receivers which fed square law detectors and strip chart recorders with suitable averaging circuits to eliminate sharp transients as much as possible.

Dewatering Carbonate Soils of the Pacific

Study of formation of atolls and various types of carbonate soils found on 3 typical coral islets of Kwajalein Atoll; results of novel dewatering design and procedure. in connection with building of Nike-Zeus installation.