scholarly journals Turbulent spectra in the solar wind plasma

2009 ◽  
Vol 76 (2) ◽  
pp. 183-191 ◽  
Author(s):  
DASTGEER SHAIKH ◽  
G. P. ZANK
Keyword(s):  
Solar Wind ◽  
Three Dimensional ◽  
Solar Wind Plasma ◽  
Density Fluctuations ◽  
Magnetized Plasma ◽  
Density Spectrum ◽  
Turbulent Spectrum ◽  
Extended Length ◽  
Turbulent Spectra ◽  
Magnetohydrodynamic Fluid

AbstractObservations of interstellar scintillations at radio wavelengths reveal a Kolmogorov-like scaling of the electron density spectrum with a spectral slope of −5/3 over six decades in wavenumber space. A similar turbulent density spectrum in the solar wind plasma has been reported. The energy transfer process in the magnetized solar wind plasma over such extended length scales remains an unresolved paradox of modern turbulence theories, raising the especially intriguing question of how a compressible magnetized solar wind exhibits a turbulent spectrum that is a characteristic of an incompressible hydrodynamic fluid. To address these questions, we have undertaken three-dimensional time-dependent numerical simulations of a compressible magnetohydrodynamic fluid describing super-Alfvénic, supersonic and strongly magnetized plasma. It is shown that the observed Kolmogorov-like (−5/3) spectrum can develop in the solar wind plasma by supersonic plasma motions that dissipate into highly subsonic motion that passively convect density fluctuations.

scholarly journals Three-dimensional simulations of turbulent spectra in the local interstellar medium

2007 ◽  
Vol 14 (4) ◽  
pp. 351-359 ◽  
Author(s):  
D. Shaikh ◽  
G. P. Zank
Keyword(s):  
Interstellar Medium ◽  
Three Dimensional ◽  
Density Fluctuations ◽  
Spectral Energy ◽  
Local Interstellar Medium ◽  
Laboratory Plasmas ◽  
Self Consistent ◽  
Supersonic Plasma ◽  
Turbulent Spectra ◽  
Three Dimensional Simulations

Abstract. Three-dimensional time dependent numerical simulations of compressible magnetohydrodynamic fluids describing super-Alfvénic, supersonic and strongly magnetized space and laboratory plasmas show a nonlinear relaxation towards a state of near incompressibility. The latter is characterized essentially by a subsonic turbulent Mach number. This transition is mediated dynamically by disparate spectral energy dissipation rates in compressible magnetosonic and shear Alfvénic modes. Nonlinear cascades lead to super-Alfvénic turbulent motions decaying to a sub-Alfvénic regime that couples weakly with (magneto)acoustic cascades. Consequently, the supersonic plasma motion is transformed into highly subsonic motion and density fluctuations experience a passive convection. This model provides a self-consistent explaination of the ubiquitous nature of incompressible magnetoplasma fluctuations in the solar wind and the interstellar medium.

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.

What can Hall-MHD simulations tell us about the transition region in the solar wind proton density spectrum?

2020 ◽  
Author(s):  
Victor Montagud-Camps ◽  
František Němec ◽  
Jana Šafránková ◽  
Zdeněk Němeček ◽  
Roland Grappin ◽  
...  
Keyword(s):  
Solar Wind ◽  
Transition Region ◽  
Spectral Index ◽  
Density Fluctuations ◽  
Power Density Spectrum ◽  
Proton Density ◽  
Density Spectrum ◽  
Significant Difference ◽  
Field Fluctuations ◽  
Hall Mhd

<p>Similarly to the power density spectrum of magnetic field fluctuations in the solar wind, the spectrum of density fluctuations also shows multiple spectral slopes. Both of them present a spectral index varying between –3/2 and –5/3 in the inertial range and close to –2.8 between the proton and electron gyrofrequencies.</p><p>Despite these similarities, the spectrum of density fluctuations has a significant difference with respect to the magnetic and velocity fluctuations spectra: it shows a transition region between the inertial and the kinetic ranges with spectral index typically around –1.</p><p>We have combined the results of compressible Hall-MHD numerical simulations and measurements of the BMSW instrument onboard Spektr-R satellite to study the possible causes of the flattening in the density spectrum. Both numerical and experimental approaches point towards an important role played by Kinetic Alfvén Waves.</p>

Predicting geo-effectiveness of CMEs with EUHFORIA coupled to OpenGGCM

2021 ◽  
Author(s):  
Anwesha Maharana ◽  
Camilla Scolini ◽  
Joachim Raeder ◽  
Stefaan Poedts
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Weather Forecasting ◽  
Flux Rope ◽  
Solar Wind Plasma ◽  
Geomagnetic Disturbance ◽  
Propagation Model ◽  
Magnetized Plasma ◽  
Future Work ◽  
The Impact

<div> <p>The <strong>EU</strong>ropean <strong>H</strong>eliospheric <strong>FOR</strong>ecasting <strong>I</strong>nformation <strong>A</strong>sset (<strong>EUHFORIA</strong>, Pomoell and Poedts, 2018) is a physics-based heliospheric and CME propagation model designed for space weather forecasting. Although EUHFORIA can predict the solar wind plasma and magnetic field parameters at Earth, it is not designed to evaluate indices like Disturbance-storm-time (Dst) or Auroral Electrojet (AE) that quantify the impact of the magnetized plasma encounters on Earth’s magnetosphere. To overcome this limitation, we coupled EUHFORIA with <strong>Open</strong> <strong>G</strong>eospace <strong>G</strong>eneral <strong>C</strong>irculation <strong>M</strong>odel (<strong>OpenGGCM</strong>, Raeder et al, 1996) which is a magnetohydrodynamic model of Earth’s magnetosphere. In this coupling, OpenGGCM takes the solar wind and interplanetary magnetic field obtained from EUHFORIA simulation as input to produce the magnetospheric and ionospheric parameters of Earth. We perform test runs to validate the coupling with real CME events modelled using flux rope models like Spheromak and FRi3D. We compare these simulation results with the indices obtained from OpenGGCM simulations driven by the measured solar wind data from spacecrafts like WIND. We further discuss how the choice of CME model and observationally constrained parameters influences the input parameters, and hence the geomagnetic disturbance indices estimated by OpenGGCM. We highlight limitations of the coupling and suggest improvements for future work. </p> </div>

scholarly journals Three-Dimensional Simulation Study of Plasmoid Injection into Magnetized Plasma

1998 ◽  
Vol 188 ◽  
pp. 209-210
Author(s):  
Y. Suzuki ◽  
T.-H. Watanabe ◽  
A. Kageyama ◽  
T. Sato ◽  
T. Hayashi
Keyword(s):  
Solar Wind ◽  
Simulation Study ◽  
Solar Flares ◽  
Interplanetary Medium ◽  
Three Dimensional ◽  
Magnetized Plasma ◽  
Important Process ◽  
Plasma Region ◽  
Mhd Simulations ◽  
Dimensional Simulation

Resent observations suggest that, during solar flares, plasmoids are injected into the interplanetary medium (Stewart et al., 1982). It has also been pointed out that solar wind irregularities modeled as plasmoids are penetrated into the magnetosphere (Lemaire, 1977). These plasmoid injections are considered to be an important process because they transfer mass, momentum, and energy into such magnetized plasma regions. Our objective is to investigate the dynamics of a plasmoid, which is injected into a magnetized plasma region and to reveal mechanisms to transfer them. To achieve this, we carried out three-dimensional magnetohydrodynamic (MHD) simulations.

scholarly journals Hybrid models of solar wind plasma heating

2011 ◽  
Vol 29 (6) ◽  
pp. 1071-1079 ◽  
Author(s):  
L. Ofman ◽  
A.-F. Viñas ◽  
P. S. Moya
Keyword(s):  
Solar Wind ◽  
Heavy Ions ◽  
Plasma Heating ◽  
Wave Spectrum ◽  
Solar Wind Plasma ◽  
Ion Temperature ◽  
Temperature Anisotropy ◽  
Streaming Instability ◽  
Turbulent Spectrum

Abstract. Remote sensing and in-situ observations show that solar wind ions are often hotter than electrons, and the heavy ions flow faster than the protons by up to an Alfvén speed. Turbulent spectrum of Alfvénic fluctuations and shocks were detected in solar wind plasma. Cross-field inhomogeneities in the corona were observed to extend to several tens of solar radii from the Sun. The acceleration and heating of solar wind plasma is studied via 1-D and 2-D hybrid simulations. The models describe the kinetics of protons and heavy ions, and electrons are treated as neutralizing fluid.The expansion of the solar wind is considered in 1-D hybrid model. A spectrum of Alfvénic fluctuations is injected at the computational boundary, produced by differential streaming instability, or initial ion temperature anisotropy, and the parametric dependence of the perpendicular heating of H+-He++ solar wind plasma is studied. It is found that He++ ions are heated efficiently by the Alfvénic wave spectrum below the proton gyroperiod.

scholarly journals A Model for Coronal Inflows and In/Out Pairs

2021 ◽  
Author(s):  
Benjamin Lynch
Keyword(s):  
Solar Wind ◽  
White Light ◽  
Mass Density ◽  
Three Dimensional ◽  
Solar Wind Plasma ◽  
Slow Solar Wind ◽  
Intrinsic Variability ◽  
Density Depletion ◽  
In Situ Observations

<div> <div> <div> <p>We present a three-dimensional (3D) numerical magnetohydrodynamics (MHD) model of the white-light coronagraph observational phenomena known as coronal inflows and in/out pairs. Coronal inflows in the LASCO/C2 field of view (approximately 2–6 Rs) were thought to arise from the dynamic and intermittent release of solar wind plasma associated with the helmet streamer belt as the counterpart to outward-propagating streamer blobs, formed by magnetic reconnection. The MHD simulation results show relatively narrow lanes of density depletion form high in the corona and propagate inward with sinuous motion that has been characterized as "tadpole-like" in coronagraph imagery. The height–time evolution and velocity profiles of the simulation inflows and in/out pairs are compared to their corresponding observations and a detailed analysis of the underlying magnetic field structure associated with the synthetic white-light and mass density evolution is presented. Understanding the physical origin of this structured component of the slow solar wind’s intrinsic variability could make a significant contribution to solar wind modeling and the interpretation of remote and in situ observations from Parker Solar Probe and Solar Orbiter.</p> </div> </div> </div>

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