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Accueil > Recherche > Plasmas Spatiaux > Thématiques scientifiques > Magnetic substorms

Magnetic substorms

 LPP team

O. Le Contel, A. Retino

 Selected publications

 Mystery of substorms

The Earth is a strongly magnetized planet. Its magnetic field interacts with the plasma constantly ejected by the Sun (solar wind) in the interplanetary medium. This interaction leads to spectacular phenomena. Some of their effects have implications for human activity.

The Earth’s magnetic field pushes the solar wind at a distance of about ten Earth radii from the planet on the day side, acting as a magnetic shield. The Earth environment, dominated by its intrinsic magnetic field, is called magnetosphere. On the night side of the planet, the magnetosphere stretches for hundreds of Earth radii, forming the so-called magnetotail. This region is the seat of magnetospheric substorm phenomena.

JPEG - 57.1 ko
Aurore boréale à Sodankyla en Finlande
© CNRS Photothèque - Michel HERSE

Substorms cause the acceleration of charged particles toward Earth. The arrival of these particles into the upper atmosphere is at the origin of polar auroras. We can see their nice bright draped from the surface of the Earth. The precipitation of these particles is also causing disruptions of power lines and telecommunication networks. If one observes the effects, little is known about the genesis of the acceleration of charged particles.

Knowing where and when substorms are trigger is at the heart of scientific debate for over thirty years. The first space missions launched to study the origin of magnetospheric substorms were composed of single spacecraft. These phenomena extend in minutes over large distances. These missions are faced with the difficulty of determining their starting point, which could even not be resolved by the first bi-satellite missions as ISEE 1 and 2 (ESA / NASA) (1978-1987). That is why multi satellite missions have been designed, such THEMIS mission (NASA) launched in 2007 with 5 satellites.

CNRS Ecole Polytechnique Sorbonne Université Université Paris-Saclay Observatoire de Paris
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Directeur de la publication : Dominique Fontaine (Directrice)