This report presents the results of an investigation of a proposed method for the controlled artificial generation of ultra-low-frequency (ULF) hydromagnetic waves, primarily of class Pc 1 (0.2 to 5 Hz), in the ionosphere and magnetosphere. The basis of this method, which is called the 'peninsula method' (a second possible method, the 'VLF method', is discussed in a companion report), is the passage of a ULF-modulated electric current around a relatively nonconducting peninsula in the sea or in a large saline lake to form a ULF current loop that produces a ULF magnetic field in the lower ionosphere. Provided the amplitude of the ULF magnetic field fluctuations is sufficiently large, i. e., provided the maximum magnetic moment of the peninsula current loop is greater than about 10 to the 13th power Am2, it is predicted theoretically that ULF hydromagnetic waves can be generated in a disturbed region of the lower ionosphere above the peninsula. These waves can then propagate away to large distances in the ionosphere and magnetosphere. The peninsula method is a version of a particular class of ULF wave generation methods based on the use of large ground-based ULF current systems. Compared with other possible methods of generation, these methods appear to have the advantage of reliability and versatility. However, both the construction costs and the power requirements for these systems are large.

This report summarizes theoretical and experimental work sponsored by the Defense Advanced Projects Agency at Stanford University through the Office of Naval Research Contract No. N00014-75-C-1095. The primary purpose of this work, which was conducted during the interval 1 January 1975 through 28 February 1977, was to investigate the possibility of obtaining a relatively inexpensive method for the controlled artificial generation of ultra-low-frequency (ULF; frequencies less than 5 Hz) geomagnetic pulsations. Because of the great penetration of these signals in sea water, the controlled artificial source could conceivably be used as a transmitter to communicate with deeply submerged receivers at a low data rate. A second purpose of the work was to investigate the feasibility of using airborne loop antennas for air/undersea communication at ULF. The following are the major conclusions of this work; (1) The controlled artificial generation of ULF geomagnetic pulsations by the 'peninsula method, ' i.e., by the passage of a ULF-modulated electric current around a relatively nonconducting peninsula in the sea or in a large saline lake, is feasible and that further experiments, in particular, a fullscale ULF wave generation experiment, appear desirable. (2) The controlled artificial generation of ULF geomagnetic pulsations by the 'VLF method, ' i.e., by the injection of ULF-modulated VLF signals into the magnetosphere from a large ground-based VLF transmitter, appears possible, but further theoretical and experimental studies are required to clarify the generation mechanism.

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This report presents the results of an investigation of a proposed method for the controlled artificial generation of ultra-low-frequency (ULF) hydromagnetic waves of class Pc 1 (0.2 to 5 Hz) in the ionosphere and magnetosphere. In this method, which is called the VLF method, a large ground-based very-low-frequency (VLF) transmitter is used to stimulate the ULF waves by injecting pulses of VLF waves into the magnetosphere. A second possible method of ULF wave generation, the peninsula method, is discussed in a companion report. Combining the theoretical and experimental results obtained during this research, it is suggested that naturally-occurring repetitive VLF activity can stimulate Pc 1 pulsation events, and it is further suggested that such VLF activity may be a major source of stimulation for Pc 1 pulsations. Thus, future experiments on ULF wave generation with ground-based VLF transmitters would probably benefit greatly if they were combined with a program of simultaneous observations of naturally-occurring VLF and ULF activity.