1. Steven R. Spangler University of Iowa
Radio Scattering Observations of Turbulence in the Solar Wind and the Interstellar Medium
Steven R. Spangler
University of Iowa

2. Basic physics of extracting information on astrophysical plasma turbulence: the radio refractive index
Radio propagation effects primarily diagnose density fluctuations.
Are secondary indicators of B.

3. Example: Phase Scintillations of a VLBI Interferometer

4. Types of Scintillation Phenomena
Frequency scintillation
Intensity cross-correlation

5. Scintillation Contributions to Heliospheric Physics
Radial evolution in turbulence
Velocity structure of the solar wind
Possible identification of coronal kinetic Alfven waves (Harmon and Coles 2005)
Remote sensing of heliospheric shocks

6. Shocks in the Heliosphere: Direct Measurements
Bamert, Kallenbach, et al, ApJ 609, L99, 2004
Studied dependence of turbulence and cosmic ray intensities on distance upstream of shock (< 0.11 au)
Two order of magnitude enhancement in turbulence level before crossing shock jump
Additional factor of 10 jump in turbulence at shock

7. Bamert, Kallenbach, et al, 2004
Turbulence
properties
Bamert, Kallenbach, et al, 2004

8. Shocks in the Heliosphere: Radio Remote Sensing
Woo and Schwenn, JGR 96, 21227, 1991 (e.g.)
Measurements made of Doppler fluctuations
The data

9. Results from Woo and Schwenn, JGR 96, 21227, 1991

10. MHD Shocks in the Solar Wind
Comparison and compatibility between two sets of observations not thoroughly explored. There is much to learn.

11. The Interstellar Medium
The ISM has powerful shock waves (supernova remnants) that accelerate the cosmic rays. Image from Univ. of Wisconsin WHAM instrument, R. Reynolds, M. Haffner, et al

12. A method of probing supernova remnants
Spitler and Spangler, ApJ 632, 932, 2005

13. Radio sources viewed through supernova remnants show minimal “blurring” due to turbulence
Intensity of turbulence in downstream region enhanced by less than a factor of 30,000 (G127) and 2000 (S147) relative to undisturbed ISM

14. Present Results and Open Questions
Radio scattering observations provide good diagnostics of heliospheric shocks.
A detailed comparison of radio and in-situ measurements would be an interesting astrophysical exercise.
Similar scattering effects not yet seen for supernova remnants. Work by Bamert and Kallenbach indicates further inquiries are of interest.
Thanks

15. Radio Results on Coronal Turbulence I:
Speed of irregularities << VA : Irregularities are non-propagating or oblique AIC waves

16. Radio Results on Coronal Turbulence II:
Density spectrum power law with “bulge” at ion inertial length (Coles and Harmon, 1989ff)

17. Radio Results on Coronal Turbulence III:
Smooth variation of turbulent intensity with heliocentric distance; no coronal “Kumasphere”. Not unanimous; see Lotova