The scientific objective of the SWARM mission is to provide the best ever survey of the geomagnetic field and its temporal evolution, in order to gain new insights into the Earth system by improving our understanding of the Earth's climate and interior.

A constellation is to be used in order to better separate contributions from various sources of the Earth's magnetic field in the models by using the different altitudes and local times. The science carried out using these models will study the processes at the origin of these various sources of magnetic field:

the geodynamo in the external core of the Earth whose operation is still poorly understood (comparison between data gathered by SWARM and models of the geodynamo),
the magnetization of the Earth's crust (and its relationship with the geological history of the crust),
the circulations of electrical currents within the ionosphere and the magnetosphere,
the weak magnetic field induced by ocean currents which the SWARM mission should be able to identify.

© ESA

Another important aspect of SWARM is to ensure temporal continuity in the monitoring of the Earth's magnetic field from space in conjunction with measurements from ground based observatories. Data is currently provided by the Ørsted, Champ and Sac-C satellites, however, these missions are not scheduled to continue beyond 2010. The scientific importance of continuing this type of continuous measurements is shown by the great spatial and temporal diversity in the Earth's magnetic field. Geomagnetic jerks can be taken as an example of phenomenon that affects the behaviour of the field generated by the geodynamo in a brutal way at the scale of a few years and which is still poorly understood.
It is also essential to monitor the medium-term evolution of the intensity of the magnetic field in order to follow the evolution of the intensity minimum observed in the South Atlantic (also called the South Atlantic Anomaly) which is a high-risk area for satellites and space stations in low orbit because of the high quantity of radiation (area of weakness in the "protective shield" against the solar wind provided by the magnetic field).

For more information about the Earth magnetism, see the following links:

CNES MAG éduc, Dossier : le Champ Magnétique (in French)
Le Champ Magnétique : Comment le Mesurer ? A quelles applications sert-il ? (in French)
Vidéothèque numérique de l'enseignement supérieur (in French)