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The propulsive motions of swimming harp seals (Phoca groenlandica Erxleben) and ringed seals (Phoca hispida Schreber) were studied by filming individuals in a flume. The seals swam at velocities ranging from 0.6 to 1.42 m s-1. Locomotion was accomplished with alternate lateral sweeps of the hind flippers generated by lateral flexions of the axial body in(More)
A new method to generate ultrahigh-power microwave pulses compatible with mildly relativistic electron sources is proposed. This method involves a novel microwave compressor in the form of a metal helically corrugated waveguide, which can enhance the power of frequency-modulated nanosecond pulses up to the multigigawatt level. The results of the(More)
Helically corrugated waveguide has been used in various applications such as gyro-backward wave oscillators, gyro-traveling wave amplifier and microwave pulse compressor. A fast prediction of the dispersion characteristic of the operating eigenwave is very important when designing a helically corrugated waveguide. In this paper, multi-mode coupling wave(More)
In this Letter, we present theory and particle-in-cell simulations describing cyclotron radio emission from Earth's auroral region and similar phenomena in other astrophysical environments. In particular, we find that the radiation, generated by a down-going electron horseshoe distribution is due to a backward-wave cyclotron-maser emission process. The(More)
This paper presents the experimental study of microwave pulse compression using a five-fold helically corrugated waveguide. In the experiment, the maximum power compression ratio of 25.2 was achieved by compressing an input microwave pulse of 80-ns duration and 9.65-9.05-GHz frequency swept range into a 1.6-ns Gaussian-envelope pulse. For an average input(More)
This paper is exploring Auroral Kilometric Radiation modelling it as a cyclotron maser emission from a horseshoe type instability. It corresponds to a horseshoe or crescent shaped momentum distribution of energetic electrons moving into the convergent magnetic field which exists around polar regions of dipole type stars and planets including the Earth. We(More)
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