EISCAT’s ionospheric Heating facility including Dynasonde

The Heating facility is situated next to the UHF and VHF incoherent scatter radars. See the list of publications that have come out of this facility since its construction in 1979.
The Heater is used for ionospheric modification experiments applying high-power transmissions of high-frequency electro-magnetic waves to study plasma parameters in the ionosphere. The name Heating stems from the fact that these high power electromagnetic waves, which are transmitted into the ionosphre with high-gain atennas, heat the electrons and thus modify the plasma state. To create plasma turbulence, the transmitted frequencies have to be close to the plasma resonances, which are 4 to 8 MHz.

HEATING meetings
Heating Results
Here are some results from the UK campaign in May 1995.
We also did a test experiment whereby Heating induced scintillations were observed on signals received at Tromsø from a Russian satellite.

Other scientific results and events:
API technique (Artificial Periodic Irregularities)
Langmuir turbulence
ELF/VLF wave generation
The programme and abstracts for the 4th European Heating Seminar held in Tromsø in May 1995 is here
Technical Description:
Transmitters
12 linear class AB tetrode valve (or tube for you Americans) power amplifiers of 100 kW continuous rating each, driven by a 1.5 kW solid state wideband exciter. Minimum pulse length is about 20µS. Any frequency in the range 3.85-8 MHz can be tuned, but we have been allocated the following: 4.04, 4.544, 4.9128, 5.423, 6.2, 6.77, 6.96, 7.1, 7.953 MHz. The transmitters can be tuned up either uniformly or to different frequencies in 2 groups of 6, 3 groups of 4, 6 groups of 2, or 12 different frequencies.
Antennas
There is a choice of 3 arrays. Two of the arrays (numbers 2 and 3) have 6×6 crossed dipoles, resulting in 36 antennas. They cover the frequency range 3.85-5.65 MHz and 5.5-8 MHz. The gain of these is 24 dBi giving a half power beam width of 14.5 ° and a maximum effective radiated power of 300 MW. A pair of transmitters is fed to orthogonal antennas on a row of antennas. A third array (array 1), covering 5.5-8 MHz, has a gain of 30 dBi giving 1200 MW of effective radiated power. A pair of transmitters in this array feeds two rows of antennas. Each row has 12 crossed dipoles giving a total of 144 antennas. A particular transmitter can be connected to only one particular row (or pair of rows in array 1), but in any array independent of the other transmitters. The transmitters feed the antennas through about 50 km of aluminium co-axial transmission lines.
Control system
Tuning to a new frequency is done by a PC and can take a few minutes. Tilting of the beam in the north-south plane up to about ± 30 ° is possible. Power can be chosen in 2.5% steps of the maximum tuned power, which itself can be less than the maximum possible. Complicated amplitude modulation formats are possible under computer or other sources of control. For example a so-called “SOUSY-switch” is used for ON/OFF modulation by about 70dB. Modulati on frequencies in the range 15-200 Hz with duty cycles near 50% can not be used due to power supply resonance problems. The radiated wave can be linearly or circularly polarized with either sense of rotation. Polarization reversal can be achieved on a pulse to pulse basis. Accurate timing to within microseconds is possible. Frequency stability is as good as the EISCAT cesium beam reference.
Dynasonde
A digital HF sounder covering ca. 1-30 MHz is also available. This can be run like an ionosonde or in other modes such as fixed frequency soundings. Spaced receiving antennas are used. A sample ionogram shows a “clean” ionospheric trace.