1. Radioastronomical Remote Sensing of Turbulence and Current Sheets in the Solar Corona Steven R. Spangler Department of Physics and Astronomy University of Iowa

2. The concept of coronal Faraday Rotation

3. Plasma Contributions to the Faraday Rotation Integral We need enough observations to sort out various contributions to coronal density and magnetic field

4. Differential Faraday Rotation A difference in Rotation Measure between two closely-spaced lines of sight

5. Coronal Heating Mechanisms: AC vs DC In DC mechanisms, heating is done by currents (possibly turbulent) in the corona. We want to measure these currents

6. Coronal Heating Mechanisms: AC vs DC In DC mechanisms, heating is done by currents (possibly turbulent) in the corona. We want to measure these currents

7. Differential Faraday Rotation and Ampere’s Law

8. Differential Faraday Rotation and Ampere’s Law II Method utilized in Wisconsin Reversed Field Pinch (RFP) by Ding, Brower, et al (PRL 90, 035002, 2003)

9. Observations of Differential Faraday Rotation on August 16, 18 2004 Total Faraday RotationDifferential Faraday Rotation

10. Estimates of Coronal Currents 1.0 GAmp 0.3 GAmp Smaller measurements of ~ 0.1 Gamp for Aug. 18, 2003

11. Ampere’s Law and Coronal Heating Having I does not directly give volumetric heating rate. Need to know number, length, and thickness of current sheets, and resistivity for volumetric heating rate.

12. Conclusions Differential FR measurements with VLA give electrical current inside boxes of various sizes. Values of order 0.1 – 1 G-Amp Future observations could improve on these results. Targeted observations (such as good sources occulted by streamers). Observations closer to Sun at 5 GHz. And thanks to :