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An investigation of ULF disturbances and auroral acceleration processes in the coupled magnetosphere-ionosphere system using high power HF modification experiments

Project information

Grant agreement ID: INTAS-2001-00614

  • Start date

    1 May 2002

  • End date

    30 April 2005

Funded under:

IC-INTAS

Coordinated by:

University of Leicester

United Kingdom

Objective

The EISCAT Heating Facility has a longstanding history of ionospheric modification experiments. Recently new results have been obtained which have demonstrated that the ionospheric modification can lead to disturbances in the coupled magnetosphere-ionosphere. This proposal aims to extend this new and exciting work by bringing together the very considerable and diverse technical and theoretical expertise of the teams from the various INTAS nations.
Initial disturbances from RF heating experiments can, in principle, release energy stored in the magnetosphere due to a coupling between the ionosphere and the magnetosphere. Such interactions may strongly change the artificial disturbances in their intensity, spatial and temporal scales. There are many geophysical phenomena whose generation is explained in terms of this magnetosphere-ionosphere interaction. The investigation of similar phenomena, which originate from an artificially modified ionosphere, is a very interesting and complicated problem. Practical difficulties with such experiments exist in the requirement for suitable geomagnetic conditions. On the one hand the level of background activity should be significant enough to provide a process with positive feedback. On the other hand intensive natural phenomena swamp the artificial disturbance development and mask the modification effect. In addition, suitable satellite conjunctions, which can add a new dimension to such experiments, are rare. The need for additional experiments is therefore pressing.
On the basis of the results of both numerical modelling and experimental verification there is good evidence that periodic current systems produced in the ionosphere via electron heating by a ground-based HF transmitter can excite disturbances which propagate into the magnetosphere. Recent observations have demonstrated a 3 Hz emission injected at least up to the altitude of FAST spacecraft. However the study of the artificial signals with low altitude satellite has a disadvantage, namely, time of their observation is too short. The proposed project is aimed to study the artificial emissions with data from the CLUSTER satellites during intervals when they are magnetically conjugate with Tromsø. It is also proposed to use the ground-based geophysical complex operated in Scandinavia for the observation magnetic field disturbances (IMAGE magnetometer network), ionospheric electric field (CUTLASS radars), auroral particle precipitations (MIRACLE all-sky cameras) and energetic particle precipitation (IRIS imaging riometer). In addition a new technique for study of magnetic disturbances - gradient measurements providing the possibility of detecting small-scale signals of low intensity - will be employed. The gradient data processing gives an opportunity to locate the direction of the pulsation.
Effective generation of the ULF emissions with frequency around 0.01 Hz is expected under conditions of low electron density in the D-region (winter night-time ionosphere). The current density under appropriate conditions can reach the value of 80mA m-2. These currents propagate into magnetosphere as Alfvén or ion-cyclotron modes and could be detected by CLUSTER. These waves should interact with the energetic protons modifying the pitch-angle distribution. Modified distribution function of the proton should be unstable and may lead to secondary effects: generation of the waves and even to the proton precipitation. These effects will also be studied from the data of CLUSTER and other spacecraft and ground-based instruments. For the stimulated emissions (secondary ion-cyclotron waves) it will be very interesting and significant to study their spatial structure using the location of the source projection into ionosphere via the imaging riometer (IRIS) at Kilpisjarvi.
Incoherent scatter radar measurements provide the most important ionospheric parameters for the numerical modelling of artificially-generated disturbances, and the EISCAT facility remains unique in being able to provide such measurements. Measurements of the electron temperature exist for the upper E- and F-regions. The ionospheric electric field is an equally important parameter obtainable from EISCAT ion drift measurements in the F-region, and from the easternmost pair of SuperDARN radars. EISCAT can measure the ionospheric parameters only in a single point, sometimes a fatal limitation. However coordinated experiments with SuperDARN can provide the spatial information required. Recently, a new aspect of the heating experiments has been shown in Yeoman and Wright (2001). Unmodulated heating in F-region makes it possible to observe systematically uncorrelated ULF waves in the ionosphere electric field by CUTLASS. These waves could not be observed on the ground as magnetic pulsations because of their large wave number. This suggests that using the gradient technique will allow an examination of the magnetic component of these waves.

Coordinator

University of Leicester

Address

University Road
Le1 7rh Leicester

United Kingdom

Participants (4)

Cola Branch of Russian Academy of Science

Russia

St.Petersburg Filial of IZMIRAN

Russia

St.Petersburg State University

Russia

Swedish Institute for Space Physics

Sweden

Project information

Grant agreement ID: INTAS-2001-00614

  • Start date

    1 May 2002

  • End date

    30 April 2005

Funded under:

IC-INTAS

Coordinated by:

University of Leicester

United Kingdom