PRISM - Plasmapause Related boundaries in the topside Ionosphere as derived from Swarm Measurements

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PRISM is a collaborative project between the Mining and Geological Survey of Hungary (Magyar Bányászati és Földtani Szolgálat, MBFSZ), Hungary and Helmholtz Centre Potsdam - GFZ German Research Centre for Geosciences, Germany.

The position of the plasmapause (PP) is a key parameter in space weather. The variation of the PP location is a very sensitive indicator of geomagnetic activity. There are many space phenomena (e.g. cold plasma and energetic particle populations, various ULF-ELF-VLF wave populations) separated spatially by the PP, as well as a number of space processes (e.g. wave generation and grow mechanisms, wave propagation, various resonances, particle precipitation, high-latitude magnetosphere-ionosphere coupling processes etc.) that are dynamically linked to the location of the plasmapause. In this project, "Plasmapause Related boundaries in the topside Ionosphere as determined from Swarm Measurements", we develop products that characterize PP related phenomena in the topside ionosphere.

These are the mid-latitude ionospheric trough (MIT) based on electron density and temperature measurements of the Langmuir probe onboard and also from GPS TEC estimates, as well as the equatorward boundary of small-scale field-aligned currents (SSFACs) leading to an index that can be used as an estimate of the midnight position of the plasmapause. The MIT appears as a few-degree-wide depleted zone, where electron density (Ne) drops by orders of magnitude, primarily observable on the dark hemisphere. MIT is often associated with a plasma flow stagnation zone between the convection dominated plasma of the outer magnetosphere and the plasmasphere corotating with the Earth. An elevated Te is typically observed near the trough mini-mum, which is believed to be caused by precipitation or frictional heating or decreased cooling (due to decreased density). The MIT equatorward/poleward edge is closely related to the ionospheric footprint of the PP/the auroral oval, respectively.

The idea of PRISM is based on findings reported in Heilig and Lühr (2013, 2018) and is complementary to ESA’s EPHEMERIS project lead by the Mining and Geological Survey of Hungary.

At the completion of the PRISM project, both the MIT location and the midnight PP index, will be provided as operational Swarm products in daily files separately for the three individual Swarm satellites. They will be available from the start of the Swarm mission. It is planned to visualise the MIT and PP index within the virtual research service (VirES for Swarm), where it can be compared to time series of other Swarm measurements, such as electron density and temperature, or TEC.


Nov 2019 – Mar 2021


The European Space Agency (ESA) through Technical University of Denmark (DTU) - ITT 2.2 for Midlatitude Ionospheric Trough, Plasmapause and possibly related boundaries as determined from Swarm measurements




  • Mining and Geological Survey of Hungary (Magyar Bányászati és Földtani Szolgálat, MBFSZ), Ungarn
  • Danmarks Tekniske Universitet (DTU), Denmark


  • Heilig, B. and Lühr, H. (2018). Quantifying the relationship between the plasmapause and the inner boundary of small-scale field-aligned currents, as deduced from Swarm observations, Ann. Geophys., 36, 595–607,
  • Heilig, B. and Lühr, H. (2013). New plasmapause model derived from CHAMP field-aligned current signatures, Ann. Geophys., 31, 529–539.