Temperature Profiles of Coronal Loops Kerry Neal

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Temperature Profiles of Coronal LoopsKerry Neal
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The Problem and the Question

• The corona is much hotter than the surface of the
  sun.
• What is causing this heating?
• Eric Priest suggests that if we can determine the
  temperature profiles along the loops, clues to
  the heating of the loops and thus the heating of
  the corona will be revealed.
• Sounds easy enough

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Especially if we put some brains on the topic

• Eric Priest (2000)
• Markus Aschwanden (2001)
• F. Reale (2002)

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All Three Authors Analyzed the SAME loop and

• Priest used a mathematical model.
• Concluded The heating is distributed evenly
  along the coronal loop.

• Aschwanden used hydrostatic equilibrium
  equations.
• Concluded The heating occurs at the footpoints
  of coronal loops.

• Reale drew attention to background subtraction
  and when he fit his model to the observations
  concluded heating is at the apex of the loops.

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So Now What?
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Well they all rely on one methodSo how about
four?

• Filter Ratios
• Line Ratios
• EM Loci
• DEM

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Overview of Project

• Understanding the limitations of the methods I
  use
• Finding candidate loops
• Analyzing the loops

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• Of the methods to be used

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Flux Equation

• FluxAbundance ? G(T) Ne2dV
• A very powerful equation in this analysis, but it
  also has its limitations.
• If the loop is isothermal
• Flux AbundanceG(T0)Ne2V

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Testing a Constructed Spectrum
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Not Great Results

• This method is not very reliable. Each filter
  sees the part of the plasma it is most
  sensitive to.
• Problem The filters may be looking at different
  structures on the sun.

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But we continue!

• On with real data and looking for loops

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What we look for in loops

• Isolated/well defined
• On the limb
• Quiet for a few hours

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Where to find Loops

• EIT (Extreme Ultraviolet Imaging Telescope)
• CDS (Coronal Diagnostic Spectrometer)
• CDS limiting instrument-Atlas
• EIT from the Virtual Solar Observatory

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Candidate 1January 25, 1997
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Candidate 2April 20, 1998
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Candidate 3January 14, 2003
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Filter Ratios

• The ratio between 2 filters is representative of
  a particular temperature between the temperature
  each filter is sensitive to.
• For each pixel a ratio and associated temperature
  is found.
• Based on the solar x and solar y coordinates of
  each pixel can generate a plot of temperature as
  a function of the length along the loop.

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Line Ratios
If you know what elements are in the loop you can
create G(T) functions.
Abundance1 G1 (T) EM Flux1 Abundance2 G2 (T)
EM Flux2
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Line Ratio Flux Ratio
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Combine to get
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EM Loci

• Manipulating the flux equation yet again
• FluxG(T)EM
• F
• Put in G(T) functions with a corresponding
  temperature array. Solve for EM at each Temp and
  voila!

EM
G(T)
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How EM Loci is Supposed to Work
Courtesy of G. Del Zanna and H.E. Mason Solar
Active Regions SOHO/CDS and TRACE Observations
of Quiescent Coronal Loops, AA, 2003
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And the Temperatures of the Loops are
1998 1998 2003

EIT Filter Ratio 6.0
6.0 6.0
Line Ratio 6.5
6.6 6.6
EM Loci Multi-Thermal 6.2-6.3
6.3
Note Temperature in LogK
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Conclusions Cont

• Loops along the length seem isothermal with the
  filter ratio and line ratio techniques.
• Within the loop the loops are multi-thermal, thus
  there is a need for DEM analysis.

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Future Work

• Include TRACE
• Background Subtraction
• DEM analysis
• Start a data base of loops

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Super Thanks to

• Trae Winter for offering superb guidance and
  being an extremely helpful and awesome advisor
• Dick Canfield for putting the whole program
  together
• All the other REU kids for being fantastic!
• Montana for being Montana