Highlights - Volume 466-1 (April IV 2007)

“Emergence and interaction of twisted flux tubes in the Sun”, by V. Archontis, A.W Hood, and C. Brady A&A 466, p. 367

Magnetic field concentrations on the surface of the Sun such as sunspots are a manifestation of the dynamo process generating magnetic fields in the interior of our star. While it is generally agreed that these sunspots show the cross sections of large magnetic flux tubes sticking out of the surface layer, the detailed processes of the emergence of magnetic flux at the surface are still being discussed.
In this paper the authors present the first 2.5D simulations in which two flux tubes emerge from the surface layer. While previous studies used an imposed magnetic field in the atmosphere of the Sun, this new investigation studies two flux tubes: the first expands intothe atmosphere and establishes a more realistic environment for the second to expand into. Through this a new level of self-consistency in modeling the emergence of magnetic flux is reached. Even though the energeticsof the solar atmosphere cannot be treated properly yet, these simulations show that eruptive events in the corona are ultimately related to the emergence of magnetic flux from the interior.

Near-IR imaging of the cluster Westerlund 2

Infrared imaging is essential for working out the physics of star formation, as it allows us to see young stellar clusters throughtheir dust shrouds; thereby deriving the mass function (MF) of the newly-formed stars. Using deep near IR imaging of the Westerlund2 cluster, the authors find its distance and its age by comparison with theoretical isochrones. They then derive the MF and offer interesting evidence of radial stellar-mass segregation.