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Astrophysics 2: Stellar and Circumstellar Physics.

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Astrophysics 2: Stellar and Circumstellar Physics. 4. Stellar Winds (1). ~okazaki/astrophys-2/. 4.1.1 Solar wind. 4.1 Observations of stellar winds. Radiative core Convective envelope, where dynamo process is going on
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´╗┐Astronomy 2: Stellar and Circumstellar Physics 4. Stellar Winds (1)

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4.1.1 Solar wind 4.1 Observations of stellar winds Radiative center Convective envelope, where dynamo procedure is going on Corona , where the sunlight based wind starts to blow Structure of the Sun

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Interaction of the Earth's magnetosphere with the sun powered wind

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Northern lights

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Boundary between the close planetary system and the interstellar space

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Why the sun based wind blows? (Parker 1958) Suppose the sunlight based crown is static, then the condition of movement is given by If we accept the crown to be isothermal, i.e., with being the isothermal sound velocity, we have

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where Therefore, the sun based crown can't be static.

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4.1.2 Winds from huge stars: P Cygni profiles P Cygni profile : Profile described by solid discharge lines with relating blueshifted assimilation lines.

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P Cygni profiles: lines from an extending environment/stellar wind Emission Absorption E A Total spectator wavelength

Slide 10 exercise/Stars.html

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Formation of a P Cygni Line-Profile By S. Owocki

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4.2 General conditions and formalism for stellar winds 4.2.1 What is a stellar wind? A stellar wind is: a maintained surge in the external layers of a star, through which the star loses its mass persistently. a wellspring of mass, precise force, and vitality to the interstellar matter.

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4.2.2 Hydrostatic balance in the base of a wind Eq of movement: Eq of state: T changes bit by bit

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In the base of a wind, the air is exponentially stratified with a scale tallness much littler than the stellar range. e.g., Solar photosphere

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4.2.3. General dynamical conditions Mass Momentum Internal vitality EOS

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Steady, round development Mass misfortune rate Momentum Total vitality work warming conduction

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active vitality potential vitality Energy necessity work warming conduction

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Driving system of coronal winds = gas weight slope 4.2.4 A straightforward model of coronal wind: an isothermal wind Assumptions Steady & circularly symmetric. Powers checked are just gravity and weight angle power.

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Coronal wind Corona warming Convective envelope Coronal winds are driven by gas weight because of a high T in the crown.

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Wind eq: Basic conditions Eq of coherence: Eq of movement: Eq of state:

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Wind eq has a peculiarity at The basic point is at The basic point is of seat sort ( x - sort), which is steady for irritations At the basic point, (sonic point),

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Solution bends for an isothermal coronal wind (transonic arrangement)

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4.2.5 Temperature affectability of mass misfortune rate At the base of a subsonic wind with we have

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The thickness dissemination is

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Mass misfortune rate is extremely touchy to the temperature! Mass misfortune rate

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Mass misfortune rate versus temperature (Owocki 2000)

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4.3 Analogy of De laval spouts Critical arrangements have a similarity with streams in rocket spouts.

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Basic conditions Eq of congruity: Eq of movement: Eq of state: Flow eq:

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Wind eq: Flow eq: Both conditions would be indistinguishable if