First 100 ms of HF modification at Tromsø, Norway

Abstract

[1] Experiments were performed with the high-power, high-frequency (HF) facility at Tromsø, Norway to test theoretical predictions for the excitation of ion and Langmuir oscillations in the ionosphere. The principal diagnostic of wave-plasma interactions was the VHF radar at the European Incoherent Scatter (EISCAT) facility. This radar is collocated with the HF facility. High-resolution radar techniques were used to monitor the temporal development of the ion and Langmuir oscillations. HF pulses 100 ms in duration were periodically transmitted into a smooth background F region plasma. Measurements of the radar backscatter spectra show that all key spectral features predicted by strong Langmuir turbulence theory are simultaneously present in the plasma and that their evolution is in agreement with theoretical expectations. However, several new features have been observed that are not anticipated by current theory. The experimental results reinforce the notion that new theoretical developments are needed to accommodate the large HF electric fields produced at Tromsø and treat the electron acceleration process in a self-consistent fashion.

Amplitude domain analysis of strong range and Doppler spread radar echos

“…The results are similar to the ones obtained by Djuth et al (2004), except that we have slightly worse frequency resolution due to the shorter transmission pulse. But we are able to obtain much better temporal resolution.…”

Angular dependence of pump-induced bottomside and topside ionospheric plasma turbulence at EISCAT

“…However, a shortcoming of this method is that only one frequency is monitored and we had no means of monitoring for the presence of plasma irregularities at other scale sizes. Some preconditioning of the ionosphere seems likely given our pump duty cycle and average ERP compared to previous similar experiments [Djuth et al, 2004;Isham et al, 1999aIsham et al, , 1999bSulzer and Fejer, 1994].…”

“…Isham et al, 1999aIsham et al, , 1999bMishin et al, 2001] and to avoid anomalous absorption of the pump wave. Unfortunately for this type of experiment, striations are easily stimulated [e.g., Djuth et al, 2004;Isham et al, 1999aIsham et al, , 1999bSulzer and Fejer, 1994]. In addition, the possible presence of pump-induced striations was actively monitored using the Hankasalmi SuperDARN HF radar at 11.6 MHz.…”

Conditional integration of Incoherent Scattering in relation to flickering aurora

“…similar conditions) than over pulses that are contiguous in time. This was demonstrated by Djuth et al [2004], in an HF modification experiment. There, the European Incoherent Scatter (EISCAT) VHF radar was synchronized with the high-power Heating facility [Rietveld et al, 1993], and radar pulses taken at identical times relative to the switch-on time of the heater were integrated together.…”