The Signature of Evolving Turbulence in Quiet Solar Wind as Seen byUlysses

Abstract

Solar wind fluctuations, such as magnetic field or velocity, show power-law power spectra suggestive both of an inertial range of intermittent turbulence (with $À5/3 exponent), and at lower frequencies, of fluctuations of coronal origin (with $À1 exponent). The Ulysses spacecraft spent many months in the quiet fast solar wind above the Sun's polar coronal holes in a highly ordered magnetic field. We use statistical analysis methods such as the generalized structure function (GSF ) and extended self-similarity (ESS) to quantify the scaling of the moments of the probability density function of fluctuations in the magnetic field. The GSFs give power law scaling in the f À1 range of the form hj y(t þ ) À y(t)j m i $ (m) , but ESS is required to reveal scaling in the inertial range, which is of the form hj y(t þ ) À y(t)j m i $ ½g( ) (m) . We find that g( ) is independent of spacecraft position and g( ) $ À log 10 (k ) . The f À1 scaling fluctuates with radial spacecraft position. This confirms that, whereas the f À1 fluctuations are directly influenced by the corona, the inertial range fluctuations are consistent with locally evolving turbulence, but with an envelope g( ), which captures the formation of the quiet fast solar wind.

Multifractal Analysis of Heliospheric Magnetic Field Fluctuations Observed by Ulysses

“…of intermittency for the transversal B T and normal B N components, for which most of the values of parameter ∆ are in the range of about 0.4-0.8, while in the case of B R most results present level of multifractality ∆ below 0.6. This observation confirms previous analyses beyond the ecliptic (Pagel & Balogh 2001Nicol et al 2008). Differences between multifractality (intermittency) of magnetic components in the case of the slow solar wind (Figure 3 (b), (d) and (f)) are rather negligible, with the values of parameter ∆ smaller than 0.6, in general.…”

Deciphering solar turbulence from sunspots records

“…This model is defined by We find p (G) = 0.68, p (M) = 0.68 and p (D) = 0.83. The last value compares surprising well with those for the solar wind measured by the Ulysses spacecraft (Pagel & Balogh 2002; Nicol et al 2008), and for the magnetospheric cusp measured by the Polar satellite (Yordanova et al 2004), even though the frequencies differ by several orders of magnitude.…”

“…We define the SSN increment by where S ( t ) denotes the SSN at time t . Assuming statistical stationarity in the frequency range of interest, the t dependence in δ y ( t , τ) can be dropped and the GSF is then given by (Nicol, Chapman & Dendy 2008) where P is the probability density function (PDF) of δ y , the angle brackets 〈·〉 denote time averaging and m is a positive integer.…”

Vorticity scaling and intermittency in drift-interchange plasma turbulence

“…The latter quantities may, or may not, be conserved at a given level of descriptive model. Studies include direct measurements in the solar wind, 22,23 and the outputs of numerical simulations of turbulence in plasmas using various levels of description. [9][10][11][12][13][14][15][16] We present the first higher order analysis of the velocity, density, and vorticity fluctuations for the extended H-W equations, which are capable of modelling and comparing drift-interchange turbulence on the high field side (HFS) and low field side (LFS) of a tokamak.…”