Steady Flows Detected in Extreme-Ultraviolet Loops

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Steady Flows Detected in Extreme-Ultraviolet Loops

• Winebarger, A.R., Warren, H.,
• van Ballegooijen, A. Deluca, E.E., Golub, L.
• Presented by
• Henry (Trae) Winter III

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Why This Paper ?

• NOT because it was short
• Based on observations
• Launching point for a discussion on coronal loop
  properties
• General properties/assumptions
• Important equations
• Loop heating properties

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General Outline

1. General Assumptions About Coronal Loops
2. Basic Equations Used In Modeling Observing
   Loops
3. Observations Interpretations
4. Critiques

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General Assumptions About Stationary Loops

• Rosner, Tucker, Vaina. 1978 ApJ. (RTV)
• Serio, et al. 1981, ApJ. (RTVS)
• Symmetrical semicircular loops
• Constant width
• Magnetic field only defines geometry

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General Assumptions About Stationary Loops

• For hydrostatic loops Hottest material is
  located at the loop top
• Caveats
• Rayleigh-Taylor instabilities

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General Assumptions About Stationary Loops
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Predictions About Stationary Loops From RTVS

• RTVS predicts a steep temperature rise from
  footpoint to T.R. and slow rise through T.R
• RTVS predicts an observable intensity decrease
  from footpoint to apex due to an exponential
  decrease in pressure due to gravity

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Basic Equations Used In Modeling Stationary Loops
Energy Balance Equation
Heating Rate
Conductive Loss Rate
Radiative Loss Rate
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Basic Equations Used In Observing Loops
Flux Equation
Line Ratios (Isothermal Approximation)
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Observations Interpretations I

• OBS A loop in TRACE that showed very little
  intensity change over two hours
• INT Stable loop structure
• OBS A ratio between the TRACE 195Å/171Å filters
  as well as CDS line ratios is used as a temp.
  diagnostic. Temp Constant
  K
• INT Does not agree with RTVS predictions
• OBS A loop showed showed no exponential
  intensity decrease with height
• INT Does not agree with RTVS predictions

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Figure 1
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Observations Interpretations II

• OBS Red shift in the SUMER Ne VIII 770 (105.8 K)
  line which corresponds to a line of sight
  velocity of 15-40 km s-1 /- 5 km s-1.
• INT Loop is not in hydrostatic equilibrium but
  instead has a steady flow.

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Figure 2
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New Model

• Use a non symmetric heating function to induce a
  steady flow and compare numerical solutions to
  the hydrodynamic problem to the observations

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Figure 3
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Critiques

• Isothermal approx
• Redshift /Blueshift
• Redshift shift

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Critiques
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