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Stellar jets like

This is a new configuration possible with the Planeterrella. Here, the large sphere is a star, and we are increasing the pressure in the gas chamber to more than 100 Pa. We are in the presence of a highly magnetized star with a dense atmosphere (for a stellar corona). Under this pressure, we had an expanding solar wind. But above this limit, this corona narrows to focus around magnetic poles in stellar jets. The Debye area is clearly visible close to the star, but more spectacular, a cone of light traces the path of electrons and looks very similar to stellar jets.

What happens here? The physics is quite different. Electrons are emitted from the whole surface of the sphere as in all other cases. But since the gas is dense, so that the electrons are slowed down through collisions after a few centimetres. They are then trapped by the local magnetic tube and driven to northern or southern ovals: they come back toward the star from which they were ejected. Close to magnetic poles, their density becomes high enough so that emissions due to collisions become visible, looking like stellar jets : the star feeds itself with its own stellar wind.
The discovery of stellar jets dates from the late twentieth century, and their physical condition is still uncertain. There are very few photographs of stellar jets: the stars that produce them are too far away to be seen with good accuracy. However, a NASA satellite, Chandra proposes some pictures. It is assumed that an intense magnetic field (a Magnetar) could produce high currents (larger than a thousand amperes) and generate jets. But nothing has been established yet ...

Stellar jet planeterrella Stellar jet observed with the planeterrella

Stellar jet Chandra Stellar jet observed by the Chandra satellite. Credit: X-ray: NASA/CXC/GSFC/M.Corcoran et al.; Optical: NASA/STScI

Institut de Planétologie et d'Astrophysique de Grenoble (IPAG)