Robert S. Massey

Phenomenology of transionospheric pulse pairs

Recent observations of transient radio impulses by an Earth-orbiting satellite appear to be quite unlike any previously reported. They appear as pairs of brief (a few microseconds), noiselike bursts, separated by a few tens of microseconds, and are dispersed in a way that implies subionospheric origin. Over 300 of these events have now been observed. These “transionospheric pulse pairs” (TIPPs) have not yet been associated with any known source, although thunderstorms are suspected. The observations, made by the Blackbeard instrument on the ALEXIS satellite, are digitized records of the electric field in a passband from about 25 to 100 MHz. Ground-based observations of lightning in this band appear quite different, even accounting for ionospheric dispersion: bursts of short pulses last hundreds of microseconds and have much lower power (when propagated to the satellite) than TIPP events. Signals that resemble the ground-based data have been observed by Blackbeard but, being much weaker, are much less likely to trigger the instrument than are the strong pulse pair events. In this paper we analyze 97 of the early TIPP observations. We compute several parameters that describe the events: the location of the satellite at the time of reception, the energy in each pulse, the separation between pulses, the duration of each pulse, and the dispersion of each pulse. The statistical distributions of these parameters provide clues to and constraints on possible source mechanisms. The possibility that the pulses might be the direct and reflected signals from a high-altitude source is considered and cannot be rejected by the data.

F‐Θ pumping and field modulation experiments on a reversed field pinch discharge

Computational simulations indicate that proper programming of the toroidal and poloidal magnetic fields in a reversed field pinch (RFP) can drive a steady‐state current. This current drive technique, called F‐Θ pumping, assumes that the RFP plasma remains in a quasirelaxed state and that the field programming is not deleterious to pinch performace. Field modulation experiments on the Los Alamos ZT‐40M experiment have shown that these assumptions are reasonable, and hence F‐Θ pumping is a plausible candidate for RFP current drive.

The Los Alamos beacon receiver array

Describes radio receivers that monitor transmissions from beacons on geosynchronous satellites. The receivers can detect ionospheric perturbations of a 300-3000 s period in the electron density integrated from beacon to receiver, for amplitudes as low as (1-2)/spl times/10/sup 13/ m/sup -2/. Data are used in studies of atmospheric acoustic and acoustic-gravity waves. >

Impulse response function for a transionospheric signal through a Gaussian filter

This short communique presents calculations of the output of a Gaussian filter to an electromagnetic impulse that has propagated through a nonmagnetized ionosphere. The rather simple result is interpreted on a physical basis. Useful expressions for the peak power and for the optimum bandwidth are obtained.

Total-electron-content signatures of plasmaspheric motions

Measurements of fluctuations in total electron content made with a radio interferometer reveal weak but frequent outbursts of total-electron-content disturbances, with trace azimuths roughly westward, with trace speeds up to ∼2 km/s, and with temporal periods in the range 100–500 seconds. Statistical tests of the dataset suggest that these disturbances are due to drift of plasmaspheric irregularities past the radio lines-of-sight. The phenomenon is likely to provide a new passive tracer of zonal convection in the inner magnetosphere.