SJC 2/28/2002 Steady Flows Detected in EUV 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

SJC 2/28/2002 Steady Flows Detected in EUV Loops

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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

SJC 2/28/2002 Steady Flows Detected in EUV Loops

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General Outline

I. General Assumptions About Coronal Loops

II. Basic Equations Used In Modeling & Observing Loops

III. Observations & Interpretations

IV. Critiques

SJC 2/28/2002 Steady Flows Detected in EUV Loops

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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

SJC 2/28/2002 Steady Flows Detected in EUV Loops

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• For hydrostatic loops: Hottest material is located at the loop top– Caveats

• Rayleigh-Taylor instabilities

General Assumptions About Stationary Loops

SJC 2/28/2002 Steady Flows Detected in EUV Loops

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General Assumptions About Stationary Loops

SJC 2/28/2002 Steady Flows Detected in EUV Loops

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• 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

Predictions About Stationary Loops From RTVS

SJC 2/28/2002 Steady Flows Detected in EUV Loops

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Basic Equations Used In Modeling Stationary Loops

cRH EEE

2

2

3

2

22

5

0 2

5

ds

dTT

ds

TdTEC

Energy Balance Equation

Conductive

Loss Rate

Radiative Loss Rate

dl

dTTQTPER )(2)( eR nTPE

hh s

sAE expHeating Rate

SJC 2/28/2002 Steady Flows Detected in EUV Loops

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Basic Equations Used In Observing Loops

dlnTGACF eeij 2

Flux Equation

dTTQTGACF ij )(

Line Ratios

(Isothermal Approximation)

ee

e TTGA

TGA

F

F

22

11

2

1

SJC 2/28/2002 Steady Flows Detected in EUV Loops

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OBS: A loop in TRACE that showed very little intensity change over two hours

INT: Stable loop structureOBS: 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 predictionsOBS: A loop showed showed no exponential

intensity decrease with heightINT: Does not agree with RTVS predictions

Observations & Interpretations I

05.095.510

SJC 2/28/2002 Steady Flows Detected in EUV Loops

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Figure 1

SJC 2/28/2002 Steady Flows Detected in EUV Loops

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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.

Observations & Interpretations II

SJC 2/28/2002 Steady Flows Detected in EUV Loops

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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

LsL

s

sLAE

hh 2

2exp

22

Lss

sAE

hh

0exp

11

SJC 2/28/2002 Steady Flows Detected in EUV Loops

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Figure 3

SJC 2/28/2002 Steady Flows Detected in EUV Loops

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Critiques

• Isothermal approx

• Redshift /Blueshift

• Redshift shift

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Critiques

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