The spectrum of small-scale density fluctuations in the solar wind

Abstract

Interplanetary scintillation observations at frequencies between 74 and 1400 MHz and solar elongations in the range 10–90° are combined to determine the form of the wavenumber spectrum of electron density fluctuations in the range 10⁻³ < k < 10⁻¹/km (where k = 2π/λ). The data are best explained by a spectrum in which there is a genuine scale-length; they are not consistent with a simple power-law spectrum. This suggests that turbulence may be less important than some kind of plasma instability in generating small-scale density fluctuations. The relevance of these conclusions to the use of IPS for determining radio source structure is discussed.