Observations of stellar coronae

Physics of Stellar Coronae

Solar and Stellar Coronae

The existence of hot coronae throughout the HR diagram has been proved by the observations of the Einstein observatory since the late 1970's This nding has stimulated a new interest in the study of stellar activity. The general picture relating stellar activity in late type stars to the internal generation, photospheric emergence, and chromospheric and coronal dissipation of magnetic elds, was ...

Multiwavelength Aspects of Stellar Coronae

Coronae express different facets of their energy release processes in different wavelength regions. While soft X-ray and EUV emission dominates the radiative losses of the thermal plasma, hard X-ray emission (>10 keV) can be produced from non-thermal high-energy particles accelerated as a consequence of flare processes, and radio emission is often emitted from mildly relativistic electrons trap...

Flare Heating in Stellar Coronae

An open question in the field of solar and stellar astrophysics is the source of heating that causes stellar coronae to reach temperatures of millions of degrees. One possibility is that the coronae are heated by a large number of small flares. On the Sun, flares with energies as low as those of microflares are distributed with energy as a power law of the form dN dE ∝ E −α with α ≈ 1.8, and α ...

X-ray Astronomy of Stellar Coronae ⋆

X-ray emission from stars in the cool half of the Hertzsprung-Russell diagram is generally attributed to the presence of a magnetic corona that contains plasma at temperatures exceeding 1 million K. Coronae are ubiquitous among these stars, yet many fundamental mechanisms operating in their magnetic fields still elude an interpretation through a detailed physical description. Stellar X-ray astr...