Evidence for weak MHD turbulence in the middle magnetosphere of Jupiter

Saur, Joachim; Politano, H.; Pouquet, A.; Matthaeus, W. H.

doi:10.1051/0004-6361:20020305

Cited by 102 publications

(126 citation statements)

References 43 publications

Supporting

Mentioning

116

Contrasting

Unclassified

Order By: Relevance

“…the Jovian magnetosphere [148], where the parameter ζ L is much smaller than the unity over a broad range of length scales. Although as noted above the cascade will evolve in the direction of increasing ζ l for decreasing l, and may reach the strong turbulent regime on very small scales.…”

Section: Weak/intermediate Turbulencementioning

confidence: 99%

MHD Turbulence: Scaling Laws and Astrophysical Implications

Cho

Lazarían

Vishniac

2003

Turbulence and Magnetic Fields in Astrophysics

View full text Add to dashboard Cite

Abstract. Turbulence is the most common state of astrophysical flows. In typical astrophysical fluids, turbulence is accompanied by strong magnetic fields, which has a large impact on the dynamics of the turbulent cascade. Recently, there has been a significant breakthrough on the theory of magnetohydrodynamic (MHD) turbulence. For the first time we have a scaling model that is supported by both observations and numerical simulations. We review recent progress in studies of both incompressible and compressible turbulence. We compare Iroshnikov-Kraichnan and Goldreich-Sridhar models, and discuss scalings of Alfvén, slow, and fast waves. We also discuss the completely new regime of MHD turbulence that happens below the scale at which hydrodynamic turbulent motions are damped by viscosity. In the case of the partially ionized diffuse interstellar gas the viscosity is due to neutrals and truncates the turbulent cascade at ∼parsec scales. We show that below this scale magnetic fluctuations with a shallow spectrum persist and discuss the possibility of a resumption of the MHD cascade after ions and neutrals decouple. We discuss the implications of this new insight into MHD turbulence for cosmic ray transport, grain dynamics, etc., and how to test theoretical predictions against observations.

show abstract

Section: Weak/intermediate Turbulencementioning

confidence: 99%

MHD Turbulence: Scaling Laws and Astrophysical Implications

Cho

Lazarían

Vishniac

2003

Turbulence and Magnetic Fields in Astrophysics

View full text Add to dashboard Cite

show abstract

“…However, it has been demonstrated both analytically and numerically that the energy cascade occurs predominantly in the plane perpendicular to the guiding magnetic field [8,10,15,16], which ensures that even if the turbulence is weak at large scales, it encounters the strong regime as the cascade proceeds to smaller scales. Although weak turbulence may exist in some astrophysical systems (see, e.g., [13,[17][18][19]), magnetic turbulence in nature is typically strong, in which case an exact analytic treatment is not available. In this case, high-resolution, well-optimized numerical simulations play a significant role in guiding our understanding of the turbulent dynamics.…”

Section: Introductionmentioning

confidence: 99%

On the Energy Spectrum of Strong Magnetohydrodynamic Turbulence

et al. 2012

View full text Add to dashboard Cite

The energy spectrum of magnetohydrodynamic turbulence attracts interest due to its fundamental importance and its relevance for interpreting astrophysical data. Here we present measurements of the energy spectra from a series of high-resolution direct numerical simulations of magnetohydrodynamics turbulence with a strong guide field and for increasing Reynolds number. The presented simulations, with numerical resolutions up to 2048 3 mesh points and statistics accumulated over 30 to 150 eddy turnover times, constitute, to the best of our knowledge, the largest statistical sample of steady state magnetohydrodynamics turbulence to date. We study both the balanced case, where the energies associated with Alfvén modes propagating in opposite directions along the guide field, E þ ðk ? Þ and E À ðk ? Þ, are equal, and the imbalanced case where the energies are different. In the balanced case, we find that the energy spectrum converges to a power law with exponent À3=2 as the Reynolds number is increased, which is consistent with phenomenological models that include scale-dependent dynamic alignment. For the imbalanced case, withfor all Reynolds numbers considered, while E þ has a slightly steeper spectrum at small Re. As the Reynolds number increases, E þ flattens. Since E AE are pinned at the dissipation scale and anchored at the driving scales, we postulate that at sufficiently high Re the spectra will become parallel in the inertial range and scale as E þ / E À / k À3=2 ?. Questions regarding the universality of the spectrum and the value of the ''Kolmogorov constant'' are discussed.

show abstract

“…One explanation as to why we did not observe fluctuations on the timescale of one minute or so, even though Saur et al (2002) did see them in the magnetosphere, could be that the three pixels to estimate seeing effects. As in Figure 4, the large negative velocities seen between pixels 122 and 132 are due to uneven illumination across the slit as it crosses the dawn limb of the planet.…”

Section: Resultsmentioning

confidence: 70%

“…Our study is the first attempt to detect velocity fluctuations in the Jovian system to look for this augmented Joule heating. (Saur et al, 2002) found that fluctuations were typically present in all of the Galileo data they examined, and thus a persistent feature of the Jovian magnetosphere. Their analysis was sensitive to timescales between 24 s and 4500 s at a distance of 26 R J from the planet, at which distance they estimated Alfvén travel times in the magnetosphere to be 375 s per Jovian radius (1 R J =71 492 km).…”

Section: Introductionmentioning

confidence: 87%

“…Evidence for turbulence in the Jovian middle magnetosphere has been seen in an analysis of Galileo data and it has been suggested that this turbulence could affect resistivity along magnetic field lines and alter the Hill (1979) mechanism that couples the Jovian atmosphere with the magnetosphere (Saur et al, 2002). This turbulence might also drive electric field fluctuations that would lead to an enhanced Joule heating effect.…”

Section: Introductionmentioning

confidence: 97%

See 1 more Smart Citation

Variability of Jovian ion winds: an upper limit for enhanced Joule heating

et al. 2007

View full text Add to dashboard Cite

Abstract. It has been proposed that short-timescale fluctuations about the mean electric field can significantly increase the upper atmospheric energy inputs at Jupiter, which may help to explain the high observed thermospheric temperatures. We present data from the first attempt to detect such variations in the Jovian ionosphere. Line-of-sight ionospheric velocity profiles in the Southern Jovian auroral/polar region are shown, derived from the Doppler shifting of H + 3 infrared emission spectra. These data were recently obtained from the high-resolution CSHELL spectrometer at the NASA Infrared Telescope Facility. We find that there is no variability within this data set on timescales of the order of one minute and spatial scales of 640 km, putting upper limits on the timescales of fluctuations that would be needed to enhance Joule heating.

show abstract

Evidence for weak MHD turbulence in the middle magnetosphere of Jupiter

Cited by 102 publications

References 43 publications

MHD Turbulence: Scaling Laws and Astrophysical Implications

MHD Turbulence: Scaling Laws and Astrophysical Implications

On the Energy Spectrum of Strong Magnetohydrodynamic Turbulence

Variability of Jovian ion winds: an upper limit for enhanced Joule heating

Contact Info

Product

Resources

About