Hostname: page-component-cd9895bd7-p9bg8 Total loading time: 0 Render date: 2024-12-28T02:46:41.204Z Has data issue: false hasContentIssue false
  • English
  • Français

VLBI Observations of Turbulence in the Inner Solar Wind

Published online by Cambridge University Press:  12 April 2016

Steven R. Spangler
Steven R. Spangler*
Affiliation:
Dept. of Physics and AstronomyUniversity of IowaIowa City, Iowa52242

Abstract

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

I discuss the use of Very Long Baseline Interferometer (VLBI) phase scintillations to probe the conditions of plasma turbulence in the solar wind. Specific results from 5.0 and 8.4 GHz observations with the Very Long Baseline Array (VLBA) are shown. There are several advantages of phase scintillation measurements. They are sensitive to fluctuations on scales of hundreds to thousands of kilometers, much larger than those probed by IPS intensity scintillations. In addition, with the frequency versatility of the VLBA one can measure turbulence from the outer corona ~ 5 –10 R⊙ to well past the perihelion approach of the Helios spacecraft. This permits tests of the consistency of radio propagation and direct in-situ measurements of turbulence. Such a comparison is made in the present paper. Special attention is dedicated to measuring the dependence of the normalization coefficient of the density power spectrum, on distance from the sun. Our results are consistent with the contention published several years ago by Aaron Roberts, that there is insufficient turbulence close to the sun to account for the heating and acceleration of the solar wind. In addition, an accurate determination of the relationship could aid the detection of transients in the solar wind.

Type
Coronal Heating and Solar Wind Acceleration
Information
International Astronomical Union Colloquium , Volume 154: Solar and Interplanetary Transients , 1996 , pp. 65 - 75
Copyright
Copyright © Kluwer 1997

References

Bourgois, G. (1993) in Spatio Temporal Analysis for Resolving Plasma Turbulence, ESA publication WPP-047, p. 157.Google Scholar
Coles, W.A. (1978), Space Sci. Rev. 21, 411.Google Scholar
Coles, W.A. and Harmon, J.K. (1989) Ap. J. 337, 1023.Google Scholar
Coles, W.A., Esser, R., Lovhaug, U.P., and Markkanen, J. (1991) J. Geophys. Res. 96, 13849.Google Scholar
Hewish, A. (1955), Proc. R. Soc. London A. 228, 238.Google Scholar
Klein, L., Bruno, R., Bavassano, B., and Rosenbauer, H. (1993), J. Geophys. Res. 98, 7837.Google Scholar
Marsch, E. and Tu, C.Y. (1990), J. Geophys. Res. 95, 11945.Google Scholar
Roberts, D.A. (1989), J. Geophys. Res. 94, 6899.Google Scholar
Spangler, S.R. and Sakurai, T. (1995), Ap. J. in press (June 1, 1995).Google Scholar
Sakurai, T., Spangler, S.R., and Armstrong, J.W. (1992), J. Geophys. Res. 97, 17141.Google Scholar
Sakurai, T. (1993), Ph.D. thesis, University of Iowa.Google Scholar
Woo, R. and Armstrong, J.W. (1979), J. Geophys. Res. 84, 4288.Google Scholar