Magnetic Ap Stars Research Articles

Some limits on cosmic-ray heating ofHI clouds by magnetic stars

Estimates are made of the low-energy, cosmic-ray power generated by the rotational braking of magnetic Ap stars through interaction with the interstellar medium. The resulting cosmic-ray power density (≲1.4×10−29 J s−1 m−3) in the galactic plane is at least three orders too small to maintain the observed kinetic temperatures (∼100 K) ofHi clouds. About 0.4% ofHi clouds contain an Ap star; in such cases ∼1026 J s−1 may be generated by the star during the early part of its Main Sequence life-time, but this makes only a small contribution to the heating of the cloud.