EISCAT's ionospheric Heating facility including Dynasonde
Heating facility is situated in Ramfjordmoen, near
Tromso in northern Norway, next to the
EISCAT UHF and VHF incoherent scatter
radars. The facility was built by the Max-Planck-Institut fuer Sonnensystemforschung in
collaboration with the University of Tromso in 1979. In January 1993 the
facility was transferred to EISCAT, but the institute still is one of its
The facility is used to conduct plasma physics and active geophysical research of the lower
and upper ionosphere by the controlled injection of powerful HF (4-8 MHz) waves. A technical description is given below.
Scientists from MPS who are closely involved in Heating experiments are:
T. Hagfors, H. Kohl, M. T. Rietveld, P. Stubbe, as well as guest scientists and collaborators. (M. Rietveld works half his time for MPS and the other half for EISCAT).
The main research areas covered are:
- Langmuir wave turbulence
- ELF and VLF wave research
- Effects of Gyroharmonic heating
There is a list of
publications that have come out of this facility since its construction in 1979.
Latest Heating Results
Here are some
results from the UK campaign in May 1995.
We also recently did a test experiment whereby Heating induced
scintillations were observed on signals received at Tromso from a Russian satellite.
Other recent scientific results:
API technique (Artificial Periodic Irregularities)
ELF/VLF wave generation
12 linear class AB tetrode tube power
amplifiers of 100 kW continuous rating each, driven by a 1.5 kW solid state wideband exciter. Minimum pulse length is about 20uS. 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, 6.77, 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.
There is a choice of 3
arrays. Two of the arrays (numbers 2 and 3) have 6x6 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 beamwidth of 14.5 deg 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
Tuning to a new frequency is done by a small microcomputer and can take a few minutes. Tilting of the beam in the north-south plane up to about +/- 30 deg 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. Modulation frequencies in the range 15-200 Hz with duty cyles 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.
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
ionogram shows a "clean" ionospheric trace. The
latest soundings may also be available, but this is still experimental as yet. The Dynasonde does not run continuously so do not be surprised if the latest is not so recent.
There is a
list of all soundings recorded since November 1992 when the computer was upgraded to a PC.