Radio scattering observations of turbulence in the solar wind and the interstellar medium
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Radio Scattering Observations of Turbulence in the Solar Wind and the Interstellar Medium. Steven R. Spangler University of Iowa. Basic physics of extracting information on astrophysical plasma turbulence: the radio refractive index.

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Radio scattering observations of turbulence in the solar wind and the interstellar medium

Radio Scattering Observations of Turbulence in the Solar Wind and the Interstellar Medium

Steven R. Spangler

University of Iowa


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.


Example phase scintillations of a vlbi interferometer
Example: Phase Scintillations of a VLBI Interferometer plasma turbulence: the radio refractive index


Types of scintillation phenomena
Types of Scintillation Phenomena plasma turbulence: the radio refractive index

  • Frequency scintillation

  • Intensity cross-correlation


Scintillation contributions to heliospheric physics
Scintillation Contributions to Heliospheric Physics plasma turbulence: the radio refractive index

  • 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


Shocks in the heliosphere direct measurements
Shocks in the Heliosphere: Direct Measurements plasma turbulence: the radio refractive index

  • 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


Turbulence plasma turbulence: the radio refractive index

properties

Bamert, Kallenbach, et al, 2004


Shocks in the heliosphere radio remote sensing
Shocks in the Heliosphere: Radio Remote Sensing plasma turbulence: the radio refractive index

  • Woo and Schwenn, JGR 96, 21227, 1991 (e.g.)

  • Measurements made of Doppler fluctuations

  • The data


Results from Woo and Schwenn, JGR 96, 21227, 1991 plasma turbulence: the radio refractive index


Mhd shocks in the solar wind

MHD Shocks in the Solar Wind plasma turbulence: the radio refractive index

Comparison and compatibility between two sets of observations not thoroughly explored. There is much to learn.


The interstellar medium

The Interstellar Medium plasma turbulence: the radio refractive index

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


A method of probing supernova remnants
A method of probing supernova remnants plasma turbulence: the radio refractive index

Spitler and Spangler, ApJ 632, 932, 2005


Radio sources viewed through supernova remnants show minimal blurring due to turbulence
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


Present results and open questions
Present Results and Open Questions “blurring” due to turbulence

  • 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


Radio results on coronal turbulence i

Radio Results on Coronal Turbulence I: “blurring” due to turbulence

Speed of irregularities << VA : Irregularities are non-propagating or oblique AIC waves


Radio results on coronal turbulence ii

Radio Results on Coronal Turbulence II: “blurring” due to turbulence

Density spectrum power law with “bulge” at ion inertial length (Coles and Harmon, 1989ff)


Radio results on coronal turbulence iii

Radio Results on Coronal Turbulence III: “blurring” due to turbulence

Smooth variation of turbulent intensity with heliocentric distance; no coronal “Kumasphere”. Not unanimous; see Lotova


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