Observations of prolonged ionospheric anomalies following passage of an infrasound pulse through the lower thermosphere

We have studied the Doppler spectra of E-layer vertical-incidence HF soundings around the time of passage of a brief (duration approx.10 s) acoustic shock. Following the exit of the shock from the reflection volume, there occurred a several-minute episode of spectral derangement. We have analyzed this derangement in some detail and have related it to other studies of possibly the same phenomenon. 18 refs., 10 figs

FORTE satellite constraints on ultra-high energy cosmic particle fluxes

The FORTE (Fast On-orbit Recording of Transient Events) satellite records bursts of electromagnetic waves arising from near the Earth's surface in the radio frequency (RF) range of 30 to 300 MHz with a dual polarization antenna. We investigate the possible RF signature of ultra-high energy cosmic-ray particles in the form of coherent Cherenkov radiation from cascades in ice. We calculate the sensitivity of the FORTE satellite to ultra-high energy (UHE) neutrino fluxes at different energies beyond the Greisen-Zatsepin-Kuzmin (GZK) cutoff. Some constraints on supersymmetry model parameters are also estimated due to the limits that FORTE sets on the UHE neutralino flux. The FORTE database consists of over 4 million recorded events to date, including in principle some events associated with UHE neutrinos. We search for candidate FORTE events in the period from September 1997 to December 1999. The candidate production mechanism is via coherent VHF radiation from a UHE neutrino shower in the Greenland ice sheet. We demonstrate a high efficiency for selection against lightning and anthropogenic backgrounds. A single candidate out of several thousand raw triggers survives all cuts, and we set limits on the corresponding particle fluxes assuming this event represents our background level.Comment: added a table, updated references and Figure 8, this version is submitted to Phys. Rev.

Simple model for an upper bound on density fluctuations in a turbulent pinch

A rough scaling relationship for plasma density fluctuations driven by magnetic field disturbances is derived. The result is found to agree with an earlier theory based on acoustic waves inflating magnetic flux surfaces

Interferometric studies of plasma-density fluctuations in ZT-40M, using time-delayed correlation techniques

Density fluctuations in a reversed-field pinch have been studied using multichord CO/sub 2/-laser interferometry. Both non-periodic and quasi-periodic oscillations have been observed. The latter are m = 0 and m = 1 and remain torodially localized until the final stage of the discharge, when the m = 0 oscillation becomes toroidally coherent (with n = 1)

Coordinated Satellite Observations of the Very Low Frequency Transmission Through the Ionospheric D Layer at Low Latitudes, Using Broadband Radio Emissions from Lightning

Both ray theory and full-wave models of very low frequency transmission through the ionospheric D layer predict that the transmission is greatly suppressed near the geomagnetic equator. We use data from the low-inclination Communication/Navigation Outage Forecast System satellite to test this semiquantitatively, for broadband very low frequency emissions from lightning. Approximate ground-truthing of the incident wavefields in the Earth-ionosphere waveguide is provided by the World Wide Lightning Location Network. Observations of the wavefields at the satellite are provided by the Vector Electric Field Instrument aboard the satellite. The data set comprises whistler observations with the satellite at magnetic latitudes<26deg. Thus, our conclusions, too, must be limited to the near-equatorial region and are not necessarily predictive of midlatitude whistler properties. We find that in most broadband recordings of radio waves at the satellite, very few of the lightning strokes result in a detectable radio pulse at the satellite. However, in a minority of the recordings, there is enhanced transmission of very low frequency lightning emissions through the D layer, at a level exceeding model predictions by at least an order of magnitude. We show that kilometric-scale D-layer irregularities may be implicated in the enhanced transmission. This observation of sporadic enhancements at low magnetic latitude, made with broadband lightning emissions, is consistent with an earlier review of D-layer transmission for transmission from powerful man-made radio beacons