Experimental results from the HERO Project: In situ measurements of ionospheric modifications using sounding rockets

Abstract

The HEating ROcket project HERO comprised the first in situ experiments to measure artificial ionospheric modifications at F layer heights set up by radio waves transmitted from the Heating facility at Ramfjord near Tromso in Northern Norway. Four instrumented payloads were launched on sounding rockets from Andoya Rocket Range during the autumn of 1982 into a sunlit ionosphere with the sun close to the horizon. The payloads recorded modifications, in particular, the presence of electron plasma waves near the reflection level of the heating wave. The amplitude and phase of the three components of the electric and magnetic fields of the heating wave were measured simultaneously as a function of altitude. Coherent spectra of the three electric field components of the locally generated electron plasma waves were obtained in a 50-kHz-wide band. At the same time quasi-continuous measurements were made on several fixed frequencies from 4 kHz to 16 kHz below the heating frequency and in the VLF-range using linear dipole antennas. Moreover, measurements were made of electron temperature, suprathermal electrons and local electron density along the rocket trajectory. The experimental results will be presented and discussed.

Temporal evolution of pump beam self‐focusing at the High‐Frequency Active Auroral Research Program

“…This assumes that natural variations in the ionosphere are small, which is always the case during the 1-min pump pulses (see Figure 1). From the analyzed ionograms, the depletion level is $0.5-1.5%, consistent with previous observations [e.g., Georges, 1970;Rose et al, 1985].…”

“…Rocket and satellite measurements at Arecibo of pump-induced striations revealed smallscale plasma depletions up to 12% (mean 6%) [Kelley et al, 1995] and 3% [Farley et al, 1983], respectively, for low latitudes. Rocket measurements at EISCAT show smallscale pump-induced plasma depletions up to 2% (typically <1%) [Rose et al, 1985] for high latitudes.…”

Creating space plasma from the ground

“…That ratio above ~330 km in Figure is unity within the standard deviation of the measurement confirms expectation. The sharp edge of HF‐accelerated suprathermal electron flux is expected from the sharp cutoff of instabilities where the HF electric field drops below the instability threshold, as confirmed by in situ measurements by satellites at Arecibo [ Farley et al ., ] and EISCAT Tromsø rockets [ Rose et al ., ].…”

Heater‐induced ionization inferred from spectrometric airglow measurements

“…Rose et al [1985] published in situ measurements from rocket experiments showing electron energies up to 10 eV. Carlson et al [1982] published incoherent scatter plasma line measurements establishing suprathermal electron spectra reaching at least 20 eV.…”