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Modelling X-ray Bright Points on the Quiet Sun. Parameter fitting to a Coronal Heating solution. Matthew Chantry. University of St Andrews. Mentor: Aad van Ballegooijen. Modelling X-ray Bright Points on the Quiet Sun. What is an X-ray Bright point?.

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modelling x ray bright points on the quiet sun

Modelling X-ray Bright Points on the Quiet Sun.

Parameter fitting to a Coronal Heating solution.

Matthew Chantry

University of St Andrews

Mentor: Aad van Ballegooijen

what is an x ray bright point

Modelling X-ray Bright Points on the Quiet Sun.

What is an X-ray Bright point?
  • X-ray bright points are small dynamic loop structures that are observed all over the solar corona.
  • They have a correspondence with small bipolar magnetic regions (Krieger et al. 1971, Tousey et al. 1973).

Matthew Chantry

University of St Andrews

REU Symposium

slide3

Modelling X-ray Bright Points on the Quiet Sun.

Aim
  • To find coronal heating parameters that enable modelling of XRT intensities in multiple filters.

Method

  • Construct a potential field from a magnetogram.
  • Solve the energy equation for each field line.
  • Compute XRT intensities.
  • Compare to XRT data.

Matthew Chantry

University of St Andrews

REU Symposium

construct potential field

Modelling X-ray Bright Points on the Quiet Sun.

Construct Potential field

Line of sight

Matthew Chantry

University of St Andrews

REU Symposium

coronal heating rate per unit volume

Modelling X-ray Bright Points on the Quiet Sun.

Coronal Heating rate per unit volume

(van Ballegooijen 1986)

Bphoto – 1500G, field strength in the photospheric network (Stenflo1984).

Bmag – the magnetic field strength at each point along the field line.

f – filling factor, the heat is not applied evenly along the LOS, but is applied to a proportion of each part of the LOS.

LT – the total length of the field line

Lp & τ – variables which describe the length and time scales of the granulations which input the energy into the system.

f& Lp are the unknown variables which make up our parameter space.

Matthew Chantry

University of St Andrews

REU Symposium

field line

Modelling X-ray Bright Points on the Quiet Sun.

Solving the Energy Equation

Field line

Temperature

Temperature

Density

Density

Line of sight

Matthew Chantry

University of St Andrews

REU Symposium

field line1

Modelling X-ray Bright Points on the Quiet Sun.

Field line

Computing XRT Intensities

Line of sight

Matthew Chantry

University of St Andrews

REU Symposium

slide8

Modelling X-ray Bright Points on the Quiet Sun.

Comparing to XRT data

Ti-poly

Bp 1

Model: Full line

Data: Dashed line

Matthew Chantry

University of St Andrews

REU Symposium

measuring the fit

Modelling X-ray Bright Points on the Quiet Sun.

Measuring the fit

Bp 1

Ti-poly

Al-poly/Ti-poly

C-poly/Ti-poly

C-poly

Matthew Chantry

University of St Andrews

REU Symposium

combined fit

Modelling X-ray Bright Points on the Quiet Sun.

Combined fit

Bp 1

Minimum

Matthew Chantry

University of St Andrews

REU Symposium

fitting the temperature

Modelling X-ray Bright Points on the Quiet Sun.

Fitting the Temperature

Ti-poly

Bp 1

Matthew Chantry

University of St Andrews

REU Symposium

fitting the temperature1

Modelling X-ray Bright Points on the Quiet Sun.

Fitting the Temperature

Be-thin

Bp 1

Matthew Chantry

University of St Andrews

REU Symposium

fitting the temperature2

Modelling X-ray Bright Points on the Quiet Sun.

Fitting the Temperature

Ti-poly

Bp 1

Matthew Chantry

University of St Andrews

REU Symposium

intensities in other filters

Modelling X-ray Bright Points on the Quiet Sun.

Intensities in other filters

Al-poly/Ti-poly

C-poly/Ti-poly

Bp 1

Bp 1

C-poly

Be-thin

Bp 1

Bp 1

Matthew Chantry

University of St Andrews

REU Symposium

errors

Modelling X-ray Bright Points on the Quiet Sun.

Errors
  • Using this XRT data, we cannot uniquely determine the filling factor. Need longer exposures in thicker filters?
  • Other sources of error/uncertainty:
  • Alignment of XRT images to the magnetogram.
  • Calibration of XRT intensities.
  • Unclear what the statistical errors are.
  • XRT response rates.
  • Heating model is time averaged, but bright point intensities oscillate (Kariyappa & Varghese 2008).
  • Plasma beta > 1 for low filling factors.

Matthew Chantry

University of St Andrews

REU Symposium

conclusions

Modelling X-ray Bright Points on the Quiet Sun.

Conclusions
  • For this bright point a good fit can be achieved for all 5 filters.
  • This method has also been successfully applied to other bright points (in this and other data-sets).
  • Fits are not always found for more complicated magnetic structures.
  • Systematic difference found at the sides of the features.
  • Work with density sensitive line ratios has found bright point filling factors < 0.1 (Dere 2008 & 2009).

Thanks to Aad van Ballegooijen, Steve Saar, Henry (Trae) Winter III, Kelly Koreck and everyone else!

Matthew Chantry

University of St Andrews

REU Symposium