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Swarm+Innovation, Polar Cap Products

In this project we develop Polar Cap Products (PCP) based on the in-situ data from the Swarm satellites. PCP will provide essential information on polar cap patches, which are an important element of the space weather in the polar regions. The project is supported by the European Space Agency, through STSE Swarm+ Innovation.

Swarm is a European Space Agency mission consisting of three satellites. Credits: ESA


PCP (Polar Cap Products) is a project funded by the European Space Agency (Contract No. 4000114121/15/NL/MP) in the framework of the STSE (Support To Science Element) Swarm + Innovation Program.


In this project we develop Polar Cap Products (PCP) based on in-situ data from the Swarm satellites. PCP will provide essential information on polar cap patches, which are an important element of space weather in the polar regions. PCP will allow establishing models for the space weather forecasting at high lattitudes.


Swarm is the fifth Earth Explorer mission approved in ESA's Living Planet Programme, and was successfully launched on 22 November 2013. The objective of the Swarm mission is to provide the best-ever survey of the geomagnetic field and its temporal evolution as well as the electric field in the atmosphere using a constellation of three identical satellites carrying sophisticated magnetometers and electric field instruments. The three satellites orbit the Earth at altitudes between 460 and 530 km above the Earth. They orbit around the Earth 15 times per day at an inclination close to 90 degrees. Therfefor, they provide measurements of the ionosphere in the polar regions.

Each of the satellites carries the following instruments:

  • Absolute Scalar Magnetometer (ASM)
  • Vector Field Magnetometer (VFM)
  • Electrical Field Instrument (EFI)
  • Accelerometer (ACC)
  • Laser Retro Reflector (LRR)

EFI contains the Suprathermal Ion Imagers and the Langmuir probe. It provides measurements of the electron density and temperature, and ion flow velocity. This is the main instrument used in this project.

Background: Polar Cap Patches

Schematic illustration of the polar cap patches travelling from dayside to nightside (after Moen et al. 2013).

Polar cap patches are regions of enhanced plasma density in the ionospheric F region inside the polar cap, i.e., poleward of the auroral oval. The plasma density of polar cap patches is more than twice that of the background. Polar cap patches are convected over the magnetic poles from the dayside towards nightside. While travelling they are subject to instabilities (e.g., gradient drift instability), and thereby become structured. The resulting plasma irregularities can have negative consequences on the communication with satellites - they lead to scintillations of satellite signals and influence the reliability of Global Navigation Satellite Systems (GNSS), such as Galileo, GPS, or GLONASS. Scinitllations in the polar regions can lead to navigation errors and even satellite-based navigation failure. Thus, polar cap patches are an important part of space weather, which has an increasing impact on today's society.


  • Automatic detection of polar cap patches and calculating the corresponding polar cap patch index.
  • Estimation of the gradient drift instability growth time within the polar cap patch.


We use data from the electric field instrument on board Swarm to determine both the location of polar cap patches and also calculate the gradient drift instability growth time. The plasma density measurements provided by the Langmuir probe are used to estimate the background plasma density within the polar cap, which is used to then identify those regions where the plasma density is enhanced by a factor of two. The plasma density gradient is also calculated and, combined with the ion drift velocity measured by the thermal ion imager, the gradient drift instability growth time can be calculated.


The results of the project are available as overview plots (an example is shown below), or data files. Please click here to access the results.


The project is financed by the European Space Agency, Support To Science Element (STSE) Programme, which is an element of the ESA's Earth Observation Envelope Program (EOEP-4) aiming to reinforce the scientific component of the ESA Living Planet Programme. The Swarm+ Innovation is the set of activities dedicated to support the scientific exploitation of Swarm on key scientific topics such as nowcasts and forecasts of space weather phenomena, ocean applications (e.g., general ocean circulation and its seasonal variations) or mass changes in combination with GOCE and GRACE.

Published Sep. 23, 2015 1:10 PM - Last modified Aug. 17, 2016 1:03 PM