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Ionospheric Heating

The HF modification facility and the EISCAT UHF radar

Heater picture

The high power RF modification facility at Ramfjordmoen, near Tromso, in northern Norway (69.6 degrees North, 19.2 degrees East, L= 6.2, magnetic dip angle I= 78 degrees) (Rietveld et al, 1993) was constructed jointly by the Max-Planck-Institut fur Aeronomie, Lindau and the University of Tromso. It was completed in 1980 and became part of the EISCAT association in 1993. The facility consists of 12 transmitters that generate up to 100 kW each and transmit on a number of narrow bands between 3.85 and 8 MHz. There are three antenna arrays, array 1 gives up to 1200 MW of effective radiated power (ERP) in the frequency range 5.5-8 MHz. Arrays 2 and 3 have a maximum ERP of 300 MW and operate in the frequency ranges 3.85-5.65 and 5.5-8 MHz respectively. The antennas themselves consist of crossed pairs of dipoles, with each dipole fed by a different transmitter. The beam is formed by applying different phases to adjacent pairs of dipoles, while the polarisation can be altered by changing the phase between signals fed to the crossed dipoles. The high latitude location of the HF facility is well suited to modification experiments involving the auroral electrojet. In addition, the EISCAT UHF incoherent radar facility is located nearby and the ionospheric profile is continuously measured by the Dynasonde.

Rietveld, M.T., H. Kohl, H. Kopka, and P. Stubbe, Introduction to ionospheric heating at Tromso - 1. Experimental overview, J. Atmos. Terr. Phys., 55, 577-599,1993.

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