Abstract
Abstract. Observations of modifications of the electron temperature in the F-region produced by powerful high frequency radiowaves at 4.04 MHz transmitted in X-mode are presented. The experiments were performed during quiet nighttime conditions with low ionospheric densities so no reflections occurred. Electron temperature enhancements of the order of 300–400 K were obtained. Numerical simulation of ohmic heating by the pump wave reproduces both altitude profiles and temporal dependence of the temperature modifications in the experiments.
Highlights
A powerful High Frequency (HF) radio wave can perturb the ionospheric plasma significantly and induce a great number of interesting plasma-physical phenomena near the reflection altitude (e.g. Gurevich, 2007, and references therein)
Our observations show no detectable change in Ti during the HF transmission we can simplify the model by only considering the electron energy equation
We have found temperature enhancements of the order of 300– 400 K and characteristic times of about 10 s for the modulations
Summary
A powerful High Frequency (HF) radio wave can perturb the ionospheric plasma significantly and induce a great number of interesting plasma-physical phenomena near the reflection altitude (e.g. Gurevich, 2007, and references therein). Gurevich, 2007, and references therein) This includes instabilities and mode conversions driving Langmuir and upper hybrid turbulence leading to large electron temperature enhancements (Honary et al, 1993; Robinson et al, 1996; Leyser et al, 2000; Rietveld et al, 2003), creation of field aligned density depletions (Kelley et al, 1995; Ponomarenko et al, 1999), acceleration of electrons (Carlson et al, 1982) and radio induced emissions at HF and optical frequencies (Bernhardt et al, 1989; Leyser, 2001; Brandstrom et al, 1999; Gustavsson et al, 2001; Kosch et al, 2007). Due to a large number of possible wave-plasma processes acting in the region close to the reflection altitude it is difficult to accurately separate the effects of Ohmic heating from the effects of nonlinear and resonant processes, unless one keeps the ERP (Effective radiated power) low enough to make sure the peak E-field amplitude is below the threshold for the nonlinear processes. Underdense heating makes it possible to study the effect of Ohmic heating with large amplitude E-fields in a large altitude range
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
