Solar REU 2011Jewels of the Sun

A Statistical Study of X-Ray Bright Point Energetics

Tom ElsdenUniversity of St Andrews, Scotland

Dr Steve Saar

Dr Paolo Grigis

Talk Outline

• Introduction to X-ray bright points• Purpose of the project• What have we learned?• What’s left to do?

Introduction to bright points• What are x-ray bright points (XBPs)?

Bright Points!

Basic Facts

• What do we know about them?• Lifespan: 2 hours – 2 days• Size : 2-10 x104 km• Found at all latitudes• Temperature :1-2MK• Numbers: 100s – 1000s• Emerging magnetic flux

approximately 10000

Missouri’s!

Purpose of study

• Perhaps small scale tells us of large scale• These little guys are relatively unstudied• Are all XBP’s simple magnetic bipoles?• What energizes them?

The Solar Corona

Image, SOHO website

Image, Miloslav Druckmuller

Coronal Temperature

•Generally defined > 106 K.

•Sharp rise in temperature, we believe to be caused by strong magnetic fields.

•We can see the wavelengths used to observe bright points.

Image, Astronomy and Astrophysics

(The magical) Bright Point Finder

In the beginning…

• Analysed the magnetic field in the photosphere.

• Observed that this was not going to be as simple as first planned.

• ‘Simple bipoles’ didn’t quite cover it.

Rogue Bright Points

HMI Magnetogram AIA 193Å image

Aims• Bright point temperatures

• Surrounding environment effects.

• Orientation

• Tangential flow in photosphere surrounding magnetic islands*

• Magnetic flux vs emission

We see a relatively normal distribution, with a gap to higher temperature BP’s caused byusing the 211 filter for higher temperature bright points rather than 171 or 193.

OrientationJoy’s Law & Hale’s law

Expect two peaks at 315-360 & 180-225 degrees in top plot.

Expect one peak at 315-360 degrees in bottom plot.

Flow map

Flow map courtesy Dr Karin Muglach

=> Bright points represent emerging magnetic flux!

Future Work

• Do more statistics!• Much more can be done with the flow maps,

magnetic flux and temperature correlations.• Apply to much more data.

Acknowledgements

• Dr Steve Saar• Dr Paolo Grigis• Dr Karin Muglach• NASA grant NNX09AB03G to the Smithsonian

Astrophysical Observatory.• Thanks SSXG!