Experimental investigation of ULF/VLF radio waves generation and propagation in the upper atmosphere and ionosphere during EISCAT heating experiment in 2012

Thursday, 4 September 2014
Regency Ballroom (Hyatt Regency)
Boris G Gavrilov1, Julius I Zetzer2, Natalia F Blagoveshchenskaya3, Michael T Rietveld4, Vladimir M Ermak1, Yuriy V Poklad1 and Ilya A Ryakhovskiy1, (1)Inst Geospheres Dynamics, Moscow, Russia, (2)Institute of Geosphere Dynamics RAS, Moscow, Russia, (3)Arctic and Antarctic Institute, St. Petersburg, Russia, (4)EISCAT Scientific Association, Ramfjordbotn, Norway
Abstract:
Powerful high frequency radio waves transmitted from high-power ground-based HF heating facilities could strongly modify the ionospheric plasma. The X-mode HF pump wave can generate strong small-scale artificial field aligned irregularities in the F region of the high-latitude ionosphere. One of the tasks of the Russian EISCAT heating campaign on February 2012 was an investigation of the generation and propagation of ULF/VLF signals generated at the result of HF radiation modulation. Despite the numerous attempts of long-range detection of such signals there are only several evidences of successful results. The most reliable and important results were obtained by [Barr et al., 1991] more than 20 years ago. They measured of VLF radio waves in Lindau, Germany at the distance of about 2000 km from EISCAT Heater. We present the results of the ULF/VLF registrations at the same distance during heating campaign on February 2012.

The measurements were conducted at Mikhnevo Geohysical Observatory of IDG RAS located in 80 km to the south from Moscow and at the distance of about 1900 km from Tromso. For measurements were used a sensitive magnetic field receivers with crossed air-coil loop antennas working in the frequency range from 80 Hz to 50 kHz in the femtotesla amplitude range. We recorded the radial and azimuthal magnetic component of the signals and from their ratio obtained the waveguide mode polarization. The amplitude of the signals was in the range of 1-20 femtotesla.

The signals were radiated by EISCAT Heater at 517, 1017, 2017, 3017, 4017 and 6017 Hz. It was shown that at the frequency less than 2 kHz the signals propagates in the QTEM mode, and signals at the frequency range from 2 to 4 kHz were in the QTE mode.

Observed absolute magnetic field strengths and waveguide polarizations are found to be in line with the predictions of simple waveguide models. Qualitative coincidence of the signals polarization character and its dependence on the signals frequency specifies adequacy of numerical models and reliability of the experimental data received in campaign 2012.

Barr et al, Long-range detection of VLF radiation produced by heating the auroral electrojet. Radio Science, Volume 26, Number 4, Pages 871-879, July-August 1991.

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