Circulation, water masses, and fluxes on the southeastern Bering Sea shelf

We review here the recent works on low-latitude whistler propagation based on ground measurements with a reference to space observations and point out the role of low-latitude ground whistlers in the general study of whistler propagation. Then we identify the main unsolved problems of low-latitude whistlers: (1) whether or not ground whistlers propagate along field lines. (2) the characteristics of transmission through the ionosphere, and (3) the properties of low-latitude whistler ducts (formation and decay times) and their structure. These fundamental problems also concern high-latitude whistlers, but they have less influence, since the rate of duct occurrence is higher and the duct trapping is much easier at high latitudes. On the other hand, considering that the smaller dip angle of the geomagnetic field at low latitudes makes the duct trapping and the ionospheric transmission very hard and that the rate of duct occurrence itself is not so high, we can say that low-latitude ground whistlers have suffered severe conditions during the course of their propagation. In other words, the fuller study of low-latitude whistlers will contribute to solving the most poorly understood problem: how the whistler propagates upward from its source, excites ducts, and leaks from ducts, penetrating to themore » ground. Furthermore, the characteristics of whistler ducts may be studied effectively by using low-latitude whistlers. Hence these questions should be investigated during this International Magnetospheric Study period.« less

On the propagation of low-latitude whistlers

Recent observations of both naturally occurring and triggered VLF emissions (a few KHz) made on the ground, aboard rockets, and aboard satellites are discussed. Although reference is made to auroral-zone emissions, attention is concentrated on midlatitude discrete emissions such as chorus. Following Brice [1964] and Kennel and Petschek [1966], the signals are interpreted as arising from the transverse resonance (or cyclotron) instability of magnetospheric plasma in the equatorial plane in the vicinity of the plasmapause. The energy of the gyroresonant electrons is estimated; the precipitation of these energetic electrons from the radiation belts is a consequence of the interaction.

VLF Emissions in the Magnetosphere

This paper questions the conventional wisdom that spongiform encephalopathies, particularly bovine spongiform encephalopathy (BSE), are solely due to ‘infection’ with an ultrafiltrable particulate protein called a prion. The literature is reviewed and data and circumstantial evidence are presented to support the hypothesis that the BSE epidemic was initiated as a result of a combination of factors—genetic, nutritional and chronic exposure to mutagenic organophosphate pesticides which disrupt the genetic pathway of prion protein synthesis. Possible mechanisms are discussed and the broader implications for modern farming practices inspected.

Are Organophosphate Pesticides Involved in the Causation of Bovine Spongiform Encephalopathy (BSE)? Hypothesis Based upon a Literature Review and Limited Trials on BSE Cattle

Propagation characteristics of low‐latitude whistlers

Ground observations of whistlers have been analyzed to yield a low-latitude cutoff around 16° geomagnetic latitude. It is suggested that this cutoff signifies a latitude below which, irrespective of the magnetic activity, no whistlers can be heard or when a few are heard, they can readily be identified as originating at higher latitudes.

Low‐latitude cutoff for whistlers observed on the ground

THIS communication reports riser whistlers observed for the first time in a ground station. They were noticed during the routine recording of whistlers at our low latitude station, the High Altitude Research Laboratory, Gulmarg (geomagnetic latitude 24° 10′ N, geomagnetic longitude 147° 24′ E). Because these whistlers appear as rising tones in the sonagrams, they resemble the “riser whistlers” reported by Pfeiffer et al.1, from the Injun III satellite observations.

Riser Whistlers at a Ground Station at Low Latitude

This paper presents the results of a detailed study of the influence of geomagnetic storms on low latitude whistlers recorded on ground. Studied in detail is the effect of the geomagnetic storm of March 6-10, 1970 on whistlers recorded at Gulmarg (Geomagnetic coordinates: 24°10′N; 147°24′E); results of analysis for the earlier storm of January 13-15, 1967 are included for comparison. Some of the important results of the present study are: (i) Both the whistler occurrence rate and dispersion increase simultaneously with Kp, (ii) During the decaying phase of the storm, changes in occurrence rate and in dispersion lag behind those in Kp, (iii) There is an indication of the existence of a cross-over latitude where tube contents may not change appreciably during storm periods, (iv) Multipath whistlers are observed only during disturbed conditions, (v) Duct life ranges between several hours to few days and (vi) Maximum number of ducts is observed during the main and recovery phases of the storm.

V. V. Somayajulu

Papers

Low‐latitude cutoff for whistlers observed on the ground

Riser Whistlers at a Ground Station at Low Latitude

A Study of the Effect of Geomagnetic Storms on Low Latitude Whistlers