Characterization of the Turbulent Magnetic Integral Length in the Solar Wind: From 0.3 to 5 Astronomical Units

Ruiz, M. E.; Dasso, S.; Matthaeus, W. H.; Weygand, J. M.

doi:10.1007/s11207-014-0531-9

Cited by 40 publications

(46 citation statements)

References 52 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Table I shows quantitative comparisons of correlation scale λ c , frozenin flow correlation scale λ * c , and Eulerian correlation time τ c , obtained by separate analysis of fast and slow wind data. As anticipated the correlation time and correlation length are both larger for the slow wind, which is consistent with the perspective that the slow wind is an older, more developed example of turbulence [30,31]. Further examining these new results, one may readily verify that the correlation lengths reported in Table I are in the same range as many earlier single spacecraft results [30], and are about a factor of two smaller than earlier multispacecraft results [29].…”

supporting

confidence: 80%

“…Further examining these new results, one may readily verify that the correlation lengths reported in Table I are in the same range as many earlier single spacecraft results [30], and are about a factor of two smaller than earlier multispacecraft results [29]. This level of variability in different populations is not unexpected given that the distribution based on of individual samples is broadly distributed (in fact, log-normal [31]). The Eulerian decorrelation time here is found to be longer in slow wind than in fast wind, as estimated earlier using a different (and more approximate) method [19].…”

supporting

confidence: 62%

See 1 more Smart Citation

Ensemble Space-Time Correlation of Plasma Turbulence in the Solar Wind

2016

Self Cite

View full text Add to dashboard Cite

Single point measurement turbulence cannot distinguish variations in space and time. We employ an ensemble of one-and two-point measurements in the solar wind to estimate the space-time correlation function in the comoving plasma frame. The method is illustrated using near Earth spacecraft observations, employing ACE, Geotail, IMP-8, and Wind datasets. New results include an evaluation of both correlation time and correlation length from a single method, and a new assessment of the accuracy of the familiar frozen-in flow approximation. This novel view of the spacetime structure of turbulence may prove essential in exploratory space missions such as Solar Probe Plus and Solar Orbiter for which the frozen-in flow hypothesis may not be a useful approximation.Introduction. The solar wind provides a natural laboratory for fundamental study of plasma turbulence in parameters ranges difficult to achieve in the laboratory (e.g., [1]), and often accessible only through remote sensing [2,3]. Fluctuations in space and time are characteristic of turbulence and each have significant influence in space and astrophysical contexts. The two point correlation functions and associated spectra [4,5] are essential turbulence diagnostics in applications such as plasma heating [6], solar wind acceleration [7], the scattering and transport of energetic particles [8,9], magnetic field connectivity [10,11] and geospace prediction (space weather) [12]. Time correlation enters these applications as well, but in somewhat different ways [9,11], as is also well established in turbulence theory [13]. However, for most in situ interplanetary observations, made by a single spacecraft, there is an almost complete ambiguity between spatial structure and temporal structure. For fast flows, the Taylor frozen-in flow approximation [14] (or, Taylor hypothesis) provides an estimate of purely spatial statistics, with quantifiable limitations on accuracy [15][16][17][18][19]. The time correlation and the space correlation have not been previously treated on the same footing in interplanetary datasets, as far as we are aware. Here we employ a multispacecraft methodology to present a novel view of the space-time correlation of interplanetary turbulence. We show how numerous one-and two-spacecraft measurements may be combined, without use of the Taylor hypothesis, to determine correlation functions in which length and time separations are treated as independent. This method can provide a wealth of information about turbulence structure and dynamics, and may become a valuable tool for interpreting present and future interplanetary datasets.Background. We consider space-time structure of fluctuations in interplanetary space. For simplicity we dis-

show abstract

supporting

confidence: 80%

supporting

confidence: 62%

Ensemble Space-Time Correlation of Plasma Turbulence in the Solar Wind

2016

Self Cite

View full text Add to dashboard Cite

show abstract

“…It indicates that displacements by the wind of the features in each pair are uncorrelated, and we therefore find an upper bound of 250 Mm for the correlation length of any solar wind turbulence near the comet. This measurement is consistent with the range estimated from Helios in-situ data of 270-1200 Mm, 0.5-1 AU from the Sun: the correlation scale is expected to be proportional to distance from the Sun (Ruiz et al 2014), and the comet tail is closer than the cited study range from Helios.…”

Section: Analysis Of Tail Feature Separationsupporting

confidence: 90%

Turbulence in the Solar Wind Measured With Comet Tail Test Particles

DeForest

Matthaeus

Howard

et al. 2015

ApJ

Self Cite

View full text Add to dashboard Cite

By analyzing the motions of test particles observed remotely in the tail of Comet Encke, we demonstrate that the solar wind undergoes turbulent processing enroute from the Sun to the Earth and that the kinetic energy entrained in the large-scale turbulence is sufficient to explain the well-known anomalous heating of the solar wind. Using the heliospheric imaging (HI-1) camera on board NASAʼs STEREO-A spacecraft, we have observed an ensemble of compact features in the comet tail as they became entrained in the solar wind near 0.4 AU. We find that the features are useful as test particles, via mean-motion analysis and a forward model of pickup dynamics. Using population analysis of the ensembleʼs relative motion, we find a regime of random-walk diffusion in the solar wind, followed, on larger scales, by a surprising regime of semiconfinement that we attribute to turbulent eddies in the solar wind. The entrained kinetic energy of the turbulent motions represents a sufficient energy reservoir to heat the solar wind to observed temperatures at 1 AU. We determine the Lagrangian-frame diffusion coefficient in the diffusive regime, derive upper limits for the small scale coherence length of solar wind turbulence, compare our results to existing Eulerian-frame measurements, and compare the turbulent velocity with the size of the observed eddies extrapolated to 1 AU. We conclude that the slow solar wind is fully mixed by turbulence on scales corresponding to a 1-2 hr crossing time at Earth; and that solar wind variability on timescales shorter than 1-2 hr is therefore dominated by turbulent processing rather than by direct solar effects.

show abstract

“…At 150 Gm, typical values of the turbulent velocity Z(150 Gm) and correlation length L(150 Gm) are 25 km s −1 and 1 Gm, respectively (Ruiz et al 2014;Isaacs et al 2015). Both of these quantities are approximately log-normally distributed, soextreme outliers are to be expected.…”

Section: Fading Of the Striaementioning

confidence: 99%

Fading Coronal Structure and the Onset of Turbulence in the Young Solar Wind

DeForest

Matthaeus

Viall

et al. 2016

ApJ

Self Cite

View full text Add to dashboard Cite

Above the top of the solar corona, the young, slow solar wind transitions from low-β, magnetically structured flow dominated by radial structuresto high-β, less structured flow dominated by hydrodynamics. This transition, long inferred via theory, is readily apparent in the sky region close to 10°from the Sunin processed, backgroundsubtracted solar wind images. We present image sequences collected by the inner Heliospheric Imager instrument on board the Solar-Terrestrial Relations Observatory (STEREO/HI1) in 2008 December, covering apparent distances from approximately 4°to24°from the center of the Sun and spanning this transition in thelarge-scale morphology of the wind. We describe the observation and novel techniques to extract evolving image structure from the images, and we use those data and techniques to present and quantify the clear textural shift in the apparent structure of the corona and solar wind in this altitude range. We demonstrate that the change in apparent texture is due both to anomalous fading of the radial striae that characterize the coronaand to anomalous relative brightening of locally dense puffs of solar wind that we term "flocculae."Weshow that these phenomena are inconsistent with smooth radial flow, but consistent with theonset of hydrodynamic or magnetohydrodynamic instabilities leading to a turbulent cascade in the young solar wind.

show abstract

Characterization of the Turbulent Magnetic Integral Length in the Solar Wind: From 0.3 to 5 Astronomical Units

Cited by 40 publications

References 52 publications

Ensemble Space-Time Correlation of Plasma Turbulence in the Solar Wind

Ensemble Space-Time Correlation of Plasma Turbulence in the Solar Wind

Turbulence in the Solar Wind Measured With Comet Tail Test Particles

Fading Coronal Structure and the Onset of Turbulence in the Young Solar Wind

Contact Info

Product

Resources

About