Low-frequency angular broadening and diffuse interstellar plasma turbulence

  • Steven R. Spangler
  • John W. Armstrong
V. Scattering in the ISM and Pulsar Observations
Part of the Lecture Notes in Physics book series (LNP, volume 362)


A low-frequency radio interferometer is potentially a powerful tool for studies of diffuse plasma turbulence. The scattering angular size of a source due to interstellar scattering is proportional to the square of the observing wavelength. Synchrotron self-absorption, an intrinsic mechanism for making a source larger at lower frequencies, produces an angular size proportional to the first power of the wavelength. Thus, observations at a longer wavelength will always be more sensitive to scattering than observations at higher frequencies. In this article we consider in detail two issues. (1) The effect of turbulence in the interplanetary medium is considered. We conclude that interplanetary scattering will limit the effective sensitivity of a low-frequency interferometer to far above its theoretical value. Any serious design considerations for a low-frequency, space-borne interferometer must include a detailed investigation of the effect of the interplanetary medium. (2) If the limitations imposed by the interplanetary medium can be overcome, a low-frequency interferometer could be used to search for turbulence near supernova remnants. Such turbulence has been hypothesized to play an important role in the acceleration of the cosmic rays, and observational evidence for its existence would be a major accomplishment. Finally, we discuss a couple of additional, more minor topics which could be addressed with such an instrument, such as studies to verify if the low-frequency variability of extragalactic radio sources is a scintillation phenomenon.


Solar Wind Interstellar Medium Angular Size Supernova Remnant Interplanetary Medium 
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  1. Armstrong, J.W., Woo, R., 1980. Jet Propulsion Interoffice Memorandum 3331-80-070.Google Scholar
  2. Armstrong, J.W., Woo, R., 1981. Astr. Astrophys., 103, 415.Google Scholar
  3. Bourgois, G., Cheynet, C., 1972. Astr. Astrophys., 21, 33.Google Scholar
  4. Coles, W.A., 1978. Space Sci. Rev., 21, 411.CrossRefGoogle Scholar
  5. Coles, W.A., Harmon, J.K., 1989. Astrophys. J., 337, 1023.CrossRefGoogle Scholar
  6. Cordes, J.M., Weisberg, J.M., Boriakoff, V., 1985. Astrophys. J., 288, 221.CrossRefGoogle Scholar
  7. Cordes, J.M., Rickett, B.J., Backer, D.C., 1988. In Amer. Inst. Phys. Conf. Proc. #174, Radio Wave Scattering in the Interstellar Medium.Google Scholar
  8. Cornwell, T.J., Anantharamaiah, K.R., Narayan, R., 1988. In Amer. Inst. Phys. Conf. Proc. #174, Radio Wave Scattering in the Interstellar Medium, p. 92.Google Scholar
  9. Erickson, W.C., 1964. Astrophys. J., 139, 1290.Google Scholar
  10. Goodman, J., Narayan, R., 1989. Mon. Not. R. Astr. Soc., 238, 995.Google Scholar
  11. Gwinn, C.R., Moran, J.M., and Reid, M.J., 1988. In Amer. Inst. Phys. Conf. Proc. #174, Radio Wave Scattering in the Interstellar Medium, p. 106.Google Scholar
  12. Lee, M.A., 1982. J. Geophys. Res., 87, 5063.Google Scholar
  13. Marscher, A.P., 1977. Astrophys. J., 216, 244.CrossRefGoogle Scholar
  14. Mutel, R.L., Hodges, M.W., 1986. Astrophys. J., 307, 472.CrossRefGoogle Scholar
  15. Rickett, B.J., 1977. Ann. Rev. Astr. Astrophys., 15, 479.CrossRefGoogle Scholar
  16. Rickett, B.J., Coles, W.A., Bourgois, G. 1984. Astron. Astrophys., 134, 390.Google Scholar
  17. Spangler, S.R., Mutel, R.L., Benson, J.M., Cordes, J.M., 1986. Astrophys. J., 301, 312.Google Scholar
  18. Spangler, S.R., Cordes, J.M., 1988. Astrophys. J., 322, 346.CrossRefGoogle Scholar
  19. Spangler, S.R., Fey, A.L., Cordes, J.M., 1987. Astrophys. J., 322, 909.CrossRefGoogle Scholar
  20. Spangler, S.R., Fanti, R., Gregorini, L., Padrielli, L., 1989. Astron. Astrophys. J., 209, 315.Google Scholar
  21. Spangler, S.R., Gwinn, C.R., 1990. Astrophys. J. (in press).Google Scholar

Copyright information

© Springer-Verlag 1990

Authors and Affiliations

  • Steven R. Spangler
    • 1
  • John W. Armstrong
    • 2
  1. 1.Department of Physics and AstronomyUniversity of IowaIowa CityUSA
  2. 2.Jet Propulsion LaboratoryPasadenaUSA

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