scholarly journals Taylor scale and effective magnetic Reynolds number determination from plasma sheet and solar wind magnetic field fluctuations

2007 ◽  
Vol 112 (A10) ◽  
pp. n/a-n/a ◽  
Author(s):  
James M. Weygand ◽  
W. H. Matthaeus ◽  
S. Dasso ◽  
M. G. Kivelson ◽  
R. J. Walker
Keyword(s):  
Magnetic Field ◽  
Reynolds Number ◽  
Solar Wind ◽  
Plasma Sheet ◽  
Magnetic Reynolds Number ◽  
Solar Wind Magnetic Field ◽  
Field Fluctuations

scholarly journals Anisotropy of the Taylor scale and the correlation scale in plasma sheet and solar wind magnetic field fluctuations

2009 ◽  
Vol 114 (A7) ◽  
pp. n/a-n/a ◽  
Author(s):  
James M. Weygand ◽  
W. H. Matthaeus ◽  
S. Dasso ◽  
M. G. Kivelson ◽  
L. M. Kistler ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Plasma Sheet ◽  
Solar Wind Magnetic Field ◽  
Field Fluctuations ◽  
Correlation Scale

scholarly journals Predictions of local ground geomagnetic field fluctuations during the 7-10 November 2004 events studied with solar wind driven models

2005 ◽  
Vol 23 (9) ◽  
pp. 3095-3101 ◽  
Author(s):  
P. Wintoft ◽  
M. Wik ◽  
H. Lundstedt ◽  
L. Eliasson
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Flow Direction ◽  
Strong Dependence ◽  
Solar Wind Plasma ◽  
Magnetic Field Data ◽  
Solar Wind Magnetic Field ◽  
Solar Wind Flow ◽  
Field Fluctuations ◽  
Ground Magnetic

Abstract. The 7-10 November 2004 period contains two events for which the local ground magnetic field was severely disturbed and simultaneously, the solar wind displayed several shocks and negative Bz periods. Using empirical models the 10-min RMS and at Brorfelde (BFE, 11.67° E, 55.63° N), Denmark, are predicted. The models are recurrent neural networks with 10-min solar wind plasma and magnetic field data as inputs. The predictions show a good agreement during 7 November, up until around noon on 8 November, after which the predictions become significantly poorer. The correlations between observed and predicted log RMS is 0.77 during 7-8 November but drops to 0.38 during 9-10 November. For RMS the correlations for the two periods are 0.71 and 0.41, respectively. Studying the solar wind data for other L1-spacecraft (WIND and SOHO) it seems that the ACE data have a better agreement to the near-Earth solar wind during the first two days as compared to the last two days. Thus, the accuracy of the predictions depends on the location of the spacecraft and the solar wind flow direction. Another finding, for the events studied here, is that the and models showed a very different dependence on Bz. The model is almost independent of the solar wind magnetic field Bz, except at times when Bz is exceptionally large or when the overall activity is low. On the contrary, the model shows a strong dependence on Bz at all times.

The Earth's plasma sheet as a laboratory for flow turbulence in high-β MHD

1997 ◽  
Vol 57 (1) ◽  
pp. 1-34 ◽  
Author(s):  
JOSEPH E. BOROVSKY ◽  
RICHARD C. ELPHIC ◽  
HERBERT O. FUNSTEN ◽  
MICHELLE F. THOMSEN
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Plasma Sheet ◽  
Sheet Material ◽  
Single Point ◽  
Power Laws ◽  
Fluxgate Magnetometer ◽  
Flow Measurements ◽  
Field Fluctuations ◽  
Flow Velocities

The bulk flows and magnetic-field fluctuations of the plasma sheet are investigated using single-point measurements from the ISEE-2 Fast Plasma Experiment and fluxgate magnetometer. Ten several-hour-long intervals of continuous data (with 3 s and 12 s time resolution) are analysed. The plasma-sheet flow appears to be strongly ‘turbulent’ (i.e. the flow is dominated by fluctuations that are unpredictable, with rms velocities[Gt ]mean velocities and with field fluctuations≈mean fields). The flow velocities are typically sub-Alfvénic. The flow-velocity probability distribution P(v) is constructed, and is found to be well fitted by exponential functions. Autocorrelation functions [Ascr ](τ) are constructed, and the autocorrelation times τcorr for the flow velocities are found to be about 2 min. From the flow measurements, an estimate of the mixing length in the plasma sheet is produced, yielding Lmix≈2 Earth radii; correspondingly, the plasma-sheet material appears to be well mixed in density and temperature. An eddy viscosity for the plasma sheet is also estimated. Power spectra, which are constructed from the v(t) and B(t) time series, have portions that are power laws with spectral indices that are near the range of those expected for turbulence theories. The plasma sheet may provide a laboratory for the study of turbulence in parameter regimes different from that of solar-wind turbulence: the plasma sheet is a β[Gt ]1, hot-ion plasma, and the turbulence may be strongly driven rather than well developed. The turbulent nature of the flow and the disordered nature of the magnetic field have implications for the transport of plasma-sheet material, for the penetration of the solar-wind electric field into the plasma sheet, and for the calculation of particle orbits in the magnetotail.

Turbulent dynamo action at low magnetic Reynolds number

1970 ◽  
Vol 41 (2) ◽  
pp. 435-452 ◽  
Author(s):  
H. K. Moffatt
Keyword(s):  
Magnetic Field ◽  
Reynolds Number ◽  
Large Scale ◽  
Isotropic Turbulence ◽  
Magnetic Energy ◽  
Magnetic Reynolds Number ◽  
Dynamo Action ◽  
Ohmic Dissipation ◽  
Magnetic Energy Density ◽  
Magnetic Diffusivity

The effect of turbulence on a magnetic field whose length-scale L is initially large compared with the scale l of the turbulence is considered. There are no external sources for the field, and in the absence of turbulence it decays by ohmic dissipation. It is assumed that the magnetic Reynolds number Rm = u0l/λ (where u0 is the root-mean-square velocity and λ the magnetic diffusivity) is small. It is shown that to lowest order in the small quantities l/L and Rm, isotropic turbulence has no effect on the large-scale field; but that turbulence that lacks reflexional symmetry is capable of amplifying Fourier components of the field on length scales of order Rm−2l and greater. In the case of turbulence whose statistical properties are invariant under rotation of the axes of reference, but not under reflexions in a point, it is shown that the magnetic energy density of a magnetic field which is initially a homogeneous random function of position with a particularly simple spectrum ultimately increases as t−½exp (α2t/2λ3) where α(= O(u02l)) is a certain linear functional of the spectrum tensor of the turbulence. An analogous result is obtained for an initially localized field.

Tsallis Distribution Functions in the Solar Wind: Magnetic Field and Velocity Observations

2007 ◽  
Author(s):  
Leonard F. Burlaga ◽  
Adolfo F. Viñas ◽  
Sumiyoshi Abe ◽  
Hans Herrmann ◽  
Piero Quarati ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Distribution Functions ◽  
Solar Wind Magnetic Field ◽  
Tsallis Distribution

scholarly journals Finite size scaling in the solar wind magnetic field energy density as seen by WIND

2002 ◽  
Vol 29 (10) ◽  
pp. 86-1-86-4 ◽  
Author(s):  
B. Hnat ◽  
S. C. Chapman ◽  
G. Rowlands ◽  
N. W. Watkins ◽  
W. M. Farrell
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Energy Density ◽  
Finite Size ◽  
Field Energy ◽  
Finite Size Scaling ◽  
Size Scaling ◽  
Magnetic Field Energy ◽  
Solar Wind Magnetic Field ◽  
Field Energy Density
Sign in / Sign up

Export Citation Format

Share Document