EISCAT Scientific Association

Overview

The EISCAT Scientific Association, an international research organisation. Until 2007, was funded and operated by the research councils of Finland, France, Germany, Japan, Norway, Sweden, and the United Kingdom (collectively, the EISCAT Associates). France has left the association end of 2006, and China has joined it at the same time. EISCAT is operating three incoherent scatter radar systems, at UHF (931 MHz) and VHF (224 MHz), in Northern Scandinavia, and at VHF (500 MHz), in Svalbard. The mainland EISCAT transmitter/receiver site is located close to the city of Tromsø, in Norway, and additional receiver stations are located in Sodankylä, Finland, and Kiruna, Sweden. The Svalbard radar is located close to the city of Longyearbyen.

EISCAT (European Incoherent Scattter) studies the interaction between the Sun and the Earth as revealed by disturbances in the magnetosphere and the ionised parts of the atmosphere (these interactions also give rise to the spectacular aurora, or Northern Lights). The Incoherent Scatter Technique allows measurements through the whole ionosphere of the electron density, the electron temperature, the ion temperature and the line of sight ion velocity. At F-region heights, the ion velocity results from the ExB convective drifts: by combining 3-static measurements of the line of sight velocities with the remote sites, a measurement of the ionospheric electric field is thus obtained.

The EISCAT radars are operated about 1500 hours a year for the mainland and about 1000 hours for the Svalbard site, of which half-time is reserved for special programs for the Associates, and the remaining time is run under pre-defined mode as Common Programs, regularly distributed according schedules defined by the EISCAT Scientific Advisory Committee (now called Scientific Oversight Committee).

Since 2007, the observing time distribution between Common programs and special programs was changed, as well as the total number of observing time, but the overall philosophy remains the same.

The various Common Program modes are briefly defined as follows:

CP-1: UHF tristatic program: transmitted beam along the earth Magnetic Field, the remote sites looking at F-Region heights for 3-static measurements of the ion-velocities. Integration time: from 2 to 5 minutes. Purposes: Fine ionospheric structures and E-Field. The VHF radars in Svalbard perform the same kind of observations, but in monostatic mode, either with the 32m mobile antenna pointing close to the magnetic field line, or with the field-aligned fixed 42m antenna.

CP-2: UHF tristatic program: similar to CP-1, but with 4 pointing directions, along B, vertical, southwards and eastwards of Tromso, the remote sites looking at F-Region heights for 3-static measurements of the ion-velocities. Cycle time: 10 minutes. Purposes: Electrodynamics of the ionosphere and neutral atmosphere dynamics. Similar mode is used also at Svalbard with the 32m antenna in monostatic mode.

CP-3: UHF tristatic program: latitude scan from north to south, with remote measurements at F-Region heights. Cycle time 30 minutes. Magnetic latitude coverage from 72 to 62 degrees. Purposes: large-scale latitude coverage of the auroral ionosphere. Similar mode is used also at Svalbard with the 32m antenna in monostatic mode.

CP-4: VHF or combined UHF-VHF program: low elevation monostatic measurements in 2 different azimuth directions northwards from Tromso. Magnetic Latitude coverage from 70 to 78 degrees. Cycle time 5 minutes. Purposes Dynamic structures at high latitudes with good time resolution. Similar mode is used also at Svalbard with the 32m antenna in monostatic mode, pointing either northwards or soutwards.

CP-6: VHF program: looking vertical, with optional eastward pointing second beam with pulse codes adapted for low altitude measurements. Sometime combined with CP-2 UHF programs. Purposes: Low ionosphere and mesosphere studies. Similar mode is also used at Svalbard.

CP-7: VHF program: looking vertical, long pulses adapted for high altitude measurements. Sometime combined with CP-1 UHF programs. Purposes: Structure and vertical dynamics of the high altitude ionosphere.