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    Études Polaires par Interférométrie à Svalbard    

Study of Aurorae in the Polar Cap

Versions :  

Scientific Staff : G. Thuillier, M. Hersé, Service d'Aéronomie, CNRS
C. Lathuillere, J. Lilensten, Laboratoire de Planétologie de Grenoble
J.-M. Perrin, Relations Terre-Soleil, Observatoire de Haute-Provence
Technical Staff : F. Huppert, Relations Terre-Soleil,
Observatoire de Haute-Provence

Polar aurora


Location of measurements


Scientific Objectives

Radar ESR at Svalbard

  The scientific objectives of the EPIS instrument are the dynamics and the thermal structure of the thermosphere and polar high altitude mesosphere. In this aim, EPIS will make interferometric measurements of the horizontal and vertical wind components and of the temperature above 80 km. Installed at Svalbard, EPIS will allow studies using the observations of the ESR polar radar.

Proposed studies are summarised below:

  • Observation and modelling of the neutral and ion dynamics, in particular the neutral wind vertical component, which is an almost unknown domain.
  • Relationships between the horizontal and vertical wind convergence.
  • Relationships between the dynamics and the components of the interplanetary magnetic field and study of the role of their sign.
  • Relations with the aurora. Particular study of the sun aligned arcs (THETA aurora).
  • Study of diurnal and seasonal variations.
  • Gravity wave study (origin, propagation direction and amplitude).
  • Study of the atmospheric tide propagation and their restoration after a magnetic storm.

A MICADO / EISCAT meridional
wind comparison.

species altitude of maximum
emission (km)
phase of reference
O1S 90 et 250 Un et Tn 557,7 Kr (557,0) 563
O1D 250 Un et Tn 630 Ne (630,4) 627
OH 85 Un et Tn 686 Ar (680) 685
O+ 250 Vi 731,9 Ar (738,4) 720

The expected accuracy is 5 m.s-1 on the wind measurements and 10 K on the thermospheric temperatures.

Principle of the measurements

The EISCAT radar and MICADO

  The light emission from the planetary atmospheres contain specific information on their environment :

  • The wavelength identifies the species.
  • The intensity provides their abundance.
  • The spectral line width allows to derive the value of the thermodynamic temperature.
  • The difference between the observed and laboratory line phases allows to mesure the atmospheric velocity.

The choice of atmospheric lines is based on several criteria:

  • Their intensity.
  • Their separation with respect to neighbouring lines emitted by the same species or by other species.
  • the altitude of emission.
  • Their thermalization when they are used to measure the temperature.

Presentation of instrument

The EPIS shelter presently seen at OHP

The Michelson interferometer
of the EPIS instrument,
previously used in MICADO

  EPIS uses a Michelson interferometer with a compensated field and automatic compensation of its intrinsic phase. It analyses the phase variation and the visibility of a natural emission, of which one deduces respectively the wind velocity along the line of sight and the temperature. EPIS uses the lines of oxygen O1D and O1S, O+ and the emission of the radical OH. The previous use of the MICADO instrument in the EISCAT site allowed to design a reliable instrument, totally automatic which will be remotely operated from Observatoire de Haute-Provence.



Experiment schematics

The EPIS instrument is funded by the
Solar-Terrestrial National Program (INSU)


External view of dome

The viewing dome showing the
9 directions of measurement
as presently seen at OHP

Site : the Aurora Page http://www.geo.mtu.edu/weather/aurora

Janvier 2001