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Paper: Evolution from Coronal Wind to Structured Chromospheric Wind
Volume: 472, New Quests in Stellar Astrophysics III: A Panchromatic View of Solar-like Stars, With and Without Planets
Page: 247
Authors: Suzuki, T. K.
Abstract: In this article, I introduce our results on the evolution of the stellar wind from low-mass stars with surface convective layers, following Suzuki (2007). By performing magnetohydrodynamical simulations from the photospheres to a few tens of stellar radii, we study the dynamics and energetics of the stellar winds. The main process in driving the stellar winds is nonlinear dissipation of Alfvénic waves excited from the surface convection zones. When the stellar radius becomes ∼ 10 times that of the Sun, the steady hot corona with temperature 106 K, suddenly disappears because the atmospheric material streams out before heated up to the the coronal temperature. Instead, many hot and warm (105 – 106 K) bubbles form in cool (T < 2 × 104 K) chromospheric winds because of the thermal instability of the radiative cooling function; the red giant wind is not a steady stream but structured outflow.
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