Very long baseline interferometer measurements of plasma turbulence in the solar wind

1992 ◽  
Vol 97 (A11) ◽  
pp. 17141 ◽  
Author(s):  
Takayuki Sakurai ◽  
Steven R. Spangler ◽  
John W. Armstrong
Keyword(s):  
Solar Wind ◽  
Plasma Turbulence ◽  
Long Baseline

scholarly journals Very Long Baseline Interferometer measurements of turbulence in the inner solar wind

2002 ◽  
Vol 384 (2) ◽  
pp. 654-665 ◽  
Author(s):  
S. R. Spangler ◽  
D. W. Kavars ◽  
P. S. Kortenkamp ◽  
M. Bondi ◽  
F. Mantovani ◽  
...  
Keyword(s):  
Solar Wind ◽  
Long Baseline

scholarly journals KINETIC PLASMA TURBULENCE IN THE FAST SOLAR WIND MEASURED BYCLUSTER

2013 ◽  
Vol 769 (1) ◽  
pp. 58 ◽  
Author(s):  
O. W. Roberts ◽  
X. Li ◽  
B. Li
Keyword(s):  
Solar Wind ◽  
Plasma Turbulence ◽  
Fast Solar Wind

scholarly journals The small amplitude of density turbulence in the inner solar wind

2003 ◽  
Vol 10 (1/2) ◽  
pp. 113-120 ◽  
Author(s):  
S. R. Spangler
Keyword(s):  
Solar Wind ◽  
Spatial Scales ◽  
Power Spectra ◽  
Solar Wind Plasma ◽  
Density Fluctuations ◽  
Long Baseline ◽  
Interferometer Phase ◽  
The Mean ◽  
Pass Through ◽  
Rms Amplitude

Abstract. Very Long Baseline Interferometer (VLBI) observations were made of radio sources close to the Sun, whose lines of sight pass through the inner solar wind (impact parameters 16-26 RE). Power spectra were analyzed of the interferometer phase fluctuations due to the solar wind plasma. These power spectra provide information on the level of plasma density fluctuations on spatial scales of roughly one hundred to several thousand kilometers. By specifying an outer scale to the turbulence spectrum, we can estimate the root-mean-square (rms) amplitude of the density fluctuations. The data indicate that the rms fluctuation in density is only about 10% of the mean density. This value is low, and consistent with extrapolated estimates from more distant parts of the solar wind. Physical speculations based on this result are presented.

Free energy sources in kinetic scale current sheets formed in collisionless plasma turbulence

2020 ◽  
Author(s):  
Neeraj Jain ◽  
Joerg Buechner
Keyword(s):  
Solar Wind ◽  
Free Energy ◽  
Collisionless Plasma ◽  
Plasma Turbulence ◽  
Energy Sources ◽  
Ion Temperature ◽  
Temperature Anisotropy ◽  
Current Sheets ◽  
Adiabatic Cooling ◽  
Collisionless Dissipation

<p>Spacecraft observations show the radial dependence of the solar wind temperature to be slower than what is expected from the adiabatic cooling of the solar wind expanding radially outwards from the sun. The most viable process considered to explain the observed slower-than-adiabatic cooling is the heating of the solar wind plasma by dissipation of the turbulent fluctuations. In solar wind which is  a collisionless plasma in turbulent state, macroscopic energy is cascaded down to kinetic scales where kinetic plasma processes can finally dissipate the energy into heat. The kinetic scale plasma processes responsible  for the dissipation of energy are, however, not well understood. A number of observational and simulation studies have shown that the heating is concentrated in and around current sheets self-consistently formed at kinetic scales. The current sheets contain free energy sources for the growth of plasma instabilities which can serve as the mechanism of the collisionless dissipation. A detailed information on the free energy sources contained in these current sheets of plasma turbulence is lacking but essential to understand the role of  plasma instabilities in collisionless dissipation.</p><p>We carry out 2-D hybrid simulations of kinetic plasma turbulence to study in detail free energy sources available in the current sheets formed in the turbulence. We focus on three free energy sources, namely, plasma density gradient, velocity gradients for both ions and electrons and ion temperature anisotropy. Our simulations show formation of current sheets in which electric current parallel to the externally applied magnetic field flows in a thickness of the order of an ion inertial length. Inside a current sheet, electron flow velocity dominates ion flow velocity in the parallel direction resulting in a larger cross-gradient of the former. The perpendicular electron velocity inside a current sheet also has variations sharper than the corresponding ion velocity. Cross gradients in plasma density are weak (under 10 % variation inside current sheets). Ion temperature is anisotropic in current sheets. Thus the current in the sheets is primarily due to electron shear flow. A theoretical model to explain the difference between electron and ion velocities in current sheets is developed. Spacecraft observations of electron shear flow in space plasma turbulence will be pointed out.   </p><p>These results suggest that the current sheets formed in kinetic plasma turbulence are close to the force free equilibrium rather than the often assumed Harris equilibrium.  This demands investigations of the linear stability properties and nonlinear evolution of force free current sheets with temperature anisotropy. Such studies can provide effective dissipation coefficients to be included in macroscopic model of the solar wind evolution.   </p>

Anisotropy in Space Plasma Turbulence: Solar Wind Observations

2011 ◽  
Vol 172 (1-4) ◽  
pp. 325-342 ◽  
Author(s):  
T. S. Horbury ◽  
R. T. Wicks ◽  
C. H. K. Chen
Keyword(s):  
Solar Wind ◽  
Space Plasma ◽  
Plasma Turbulence

scholarly journals VLASOV SIMULATIONS OF MULTI-ION PLASMA TURBULENCE IN THE SOLAR WIND

2012 ◽  
Vol 762 (2) ◽  
pp. 99 ◽  
Author(s):  
D. Perrone ◽  
F. Valentini ◽  
S. Servidio ◽  
S. Dalena ◽  
P. Veltri
Keyword(s):  
Solar Wind ◽  
Plasma Turbulence ◽  
Ion Plasma

Ion acoustic instability in the presence of plasma turbulence in the solar wind

Solar Physics ◽  
1982 ◽  
Vol 79 (1) ◽  
pp. 187-194
Author(s):  
P. Revathy ◽  
S. R. Prabhakaran Nayar
Keyword(s):  
Solar Wind ◽  
Plasma Turbulence ◽  
Acoustic Instability ◽  
Ion Acoustic
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