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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. 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.

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  1. 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

  2. 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

  3. 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

  4. Modelling X-ray Bright Points on the Quiet Sun. Construct Potential field Line of sight Matthew Chantry University of St Andrews REU Symposium

  5. 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

  6. 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

  7. 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

  8. 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

  9. 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

  10. Modelling X-ray Bright Points on the Quiet Sun. Combined fit Bp 1 Minimum Matthew Chantry University of St Andrews REU Symposium

  11. Modelling X-ray Bright Points on the Quiet Sun. Fitting the Temperature Ti-poly Bp 1 Matthew Chantry University of St Andrews REU Symposium

  12. Modelling X-ray Bright Points on the Quiet Sun. Fitting the Temperature Be-thin Bp 1 Matthew Chantry University of St Andrews REU Symposium

  13. Modelling X-ray Bright Points on the Quiet Sun. Fitting the Temperature Ti-poly Bp 1 Matthew Chantry University of St Andrews REU Symposium

  14. 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

  15. 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

  16. 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

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