scholarly journals Solar cycle dependence of scaling in solar wind fluctuations

2008 ◽  
Vol 15 (3) ◽  
pp. 445-455 ◽  
Author(s):  
S. C. Chapman ◽  
B. Hnat ◽  
K. Kiyani
Keyword(s):  
Solar Wind ◽  
Solar Cycle ◽  
Momentum Flux ◽  
Magnetic Fluctuations ◽  
Mhd Turbulence ◽  
Scaling Properties ◽  
Two Component ◽  
Energy And Momentum ◽  
Cycle Dependence

Abstract. In this review we collate recent results for the statistical scaling properties of fluctuations in the solar wind with a view to synthesizing two descriptions: that of evolving MHD turbulence and that of a scaling signature of coronal origin that passively propagates with the solar wind. The scenario that emerges is that of coexistent signatures which map onto the well known "two component" picture of solar wind magnetic fluctuations. This highlights the need to consider quantities which track Alfvénic fluctuations, and energy and momentum flux densities to obtain a complete description of solar wind fluctuations.

Solar cycle dependence of the solar wind dynamics: Pioneer Voyager, and Ulysses from 1 to 5 AU

1996 ◽  
Vol 101 (A11) ◽  
pp. 24359-24371 ◽  
Author(s):  
J. Américo González-Esparza ◽  
Edward J. Smith
Keyword(s):  
Solar Wind ◽  
Solar Cycle ◽  
Cycle Dependence

scholarly journals Solar cycle changes in the geo-effectiveness of small-scale solar wind turbulence measured by Wind and ACE at 1 AU

2007 ◽  
Vol 25 (5) ◽  
pp. 1183-1197 ◽  
Author(s):  
M. L. Parkinson ◽  
R. C. Healey ◽  
P. L. Dyson
Keyword(s):  
Solar Wind ◽  
Solar Cycle ◽  
Solar Minimum ◽  
Large Scale ◽  
Small Scale ◽  
Scaling Exponent ◽  
Mhd Turbulence ◽  
Scaling Exponents ◽  
Solar Wind Turbulence ◽  
Wind Turbulence

Abstract. Multi-scale structure of the solar wind in the ecliptic at 1 AU undergoes significant evolution with the phase of the solar cycle. Wind spacecraft measurements during 1995 to 1998 and ACE spacecraft measurements during 1997 to 2005 were used to characterise the evolution of small-scale (~1 min to 2 h) fluctuations in the solar wind speed vsw, magnetic energy density B2, and solar wind ε parameter, in the context of large-scale (~1 day to years) variations. The large-scale variation in ε most resembled large-scale variations in B2. The probability density of large fluctuations in ε and B2 both had strong minima during 1995, a familiar signature of solar minimum. Generalized Structure Function (GSF) analysis was used to estimate inertial range scaling exponents aGSF and their evolution throughout 1995 to 2005. For the entire data set, the weighted average scaling exponent for small-scale fluctuations in vsw was aGSF=0.284±0.001, a value characteristic of intermittent MHD turbulence (>1/4), whereas the scaling exponents for corresponding fluctuations in B2 and ε were aGSF=0.395±0.001 and 0.334±0.001, respectively. These values are between the range expected for Gaussian fluctuations (1/2) and Kolmogorov turbulence (1/3). However, the scaling exponent for ε changed from a Gaussian-Kolmogorov value of 0.373±0.005 during 1997 (end of solar minimum) to an MHD turbulence value of 0.247±0.004 during 2003 (recurrent fast streams). Changes in the characteristics of solar wind turbulence may be reproducible from one solar cycle to the next.

scholarly journals On the probability distribution function of small-scale interplanetary magnetic field fluctuations

2004 ◽  
Vol 22 (10) ◽  
pp. 3751-3769 ◽  
Author(s):  
R. Bruno ◽  
V. Carbone ◽  
L. Primavera ◽  
F. Malara ◽  
L. Sorriso-Valvo ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Robust Statistics ◽  
Interplanetary Space ◽  
Parametric Instability ◽  
Field Vector ◽  
Small Scale ◽  
Magnetic Fluctuations ◽  
Mhd Turbulence ◽  
The One

Abstract. In spite of a large number of papers dedicated to the study of MHD turbulence in the solar wind there are still some simple questions which have never been sufficiently addressed, such as: a) Do we really know how the magnetic field vector orientation fluctuates in space? b) What are the statistics followed by the orientation of the vector itself? c) Do the statistics change as the wind expands into the interplanetary space? A better understanding of these points can help us to better characterize the nature of interplanetary fluctuations and can provide useful hints to investigators who try to numerically simulate MHD turbulence. This work follows a recent paper presented by some of the authors which shows that these fluctuations might resemble a sort of random walk governed by Truncated Lévy Flight statistics. However, the limited statistics used in that paper did not allow for final conclusions but only speculative hypotheses. In this work we aim to address the same problem using more robust statistics which, on the one hand, forces us not to consider velocity fluctuations but, on the other hand, allows us to establish the nature of the governing statistics of magnetic fluctuations with more confidence. In addition, we show how features similar to those found in the present statistical analysis for the fast speed streams of solar wind are qualitatively recovered in numerical simulations of the parametric instability. This might offer an alternative viewpoint for interpreting the questions raised above.

scholarly journals Emergence of intermittent structures and reconnection in MHD turbulence

2010 ◽  
Vol 6 (S274) ◽  
pp. 116-119
Author(s):  
Antonella Greco ◽  
Sergio Servidio ◽  
William H. Matthaeus ◽  
Pablo Dmitruk
Keyword(s):  
Numerical Simulation ◽  
Solar Wind ◽  
Magnetic Reconnection ◽  
Numerical Algorithms ◽  
Magnetic Fluctuations ◽  
Mhd Turbulence ◽  
Local Origin ◽  
Tangential Discontinuities

AbstractIn recent analyses of numerical simulation and solar wind dataset, the idea that the magnetic discontinuities may be related to intermittent structures that appear spontaneously in MHD turbulence has been explored in details. These studies are consistent with the hypothesis that discontinuity events founds in the solar wind might be of local origin as well, i.e. a by-product of the turbulent evolution of magnetic fluctuations.Using simulations of 2D MHD turbulence, we are exploring a possible link between tangential discontinuities and magnetic reconnection. The goal is to develop numerical algorithms that may be useful for solar wind applications.

scholarly journals SPATIAL CORRELATION OF SOLAR WIND FLUCTUATIONS AND THEIR SOLAR CYCLE DEPENDENCE

2008 ◽  
Vol 690 (1) ◽  
pp. 734-742 ◽  
Author(s):  
R. T. Wicks ◽  
S. C. Chapman ◽  
R. O. Dendy
Keyword(s):  
Solar Wind ◽  
Solar Cycle ◽  
Spatial Correlation ◽  
Cycle Dependence

scholarly journals Solar wind, mass and momentum losses during the solar cycle

2010 ◽  
Vol 6 (S271) ◽  
pp. 395-396
Author(s):  
R. Pinto ◽  
S. Brun ◽  
L. Jouve ◽  
R. Grappin
Keyword(s):  
Solar Wind ◽  
Solar Cycle ◽  
Wind Speed ◽  
Mass Flux ◽  
Solar Minimum ◽  
Momentum Flux ◽  
Loss Rate ◽  
Convection Zone ◽  
Mass Loss Rate ◽  
Good Agreement

AbstractWe study the connections between the sun's convection zone evolution and the dynamics of the solar wind and corona. We input the magnetic fields generated by a 2.5D axisymmetric kinematic dynamo code (STELEM) into a 2.5D axisymmetric coronal MHD code (DIP). The computations were carried out for an 11 year cycle. We show that the solar wind's velocity and mass flux vary in latitude and in time in good agreement with the well known time-latitude assymptotic wind speed diagram. Overall sun's mass loss rate, momentum flux and magnetic breaking torque are maximal near the solar minimum.

Energy and momentum flux around comet 67P throughout the Rosetta mission

2020 ◽  
Author(s):  
Hans Nilsson ◽  
Hayley Williamson ◽  
Gabriella Stenberg Wieser ◽  
Ingo Richter ◽  
Charlotte Götz
Keyword(s):  
Solar Wind ◽  
Energy Flux ◽  
Momentum Flux ◽  
Population Based ◽  
Ion Fluxes ◽  
Relative Contribution ◽  
Rosetta Mission ◽  
Order Of Magnitude ◽  
Energy And Momentum ◽  
Comet 67P

<p>We calculate the momentum and energy flux of ions measured by the Ion Composition Analyzer (ICA) on the Rosetta mission at comet 67P/Churyumov-Gerasimenko. We find that the total ion energy and momentum flux stay roughly constant over the mission, but the relative contribution of solar wind ions and cometary ions changes drastically depending on the spacecraft position in the ionosphere and distance from the comet to the sun. We also see that the magnetic pressure, calculated from the magnetic field measured by the Rosetta magnetometer, is on the order of the total ion momentum flux and roughly corresponds with the cometary ion momentum flux. Near both the beginning and end of the mission, solar wind momentum and energy flux are roughly two orders of magnitude larger than the corresponding heavy cometary ion fluxes. When the spacecraft enters the solar wind ion cavity near the comet’s periapsis, the solar wind energy and momentum flux drop drastically, mainly due to reduced density. Meanwhile, the cometary energy flux increases to be roughly equal to the solar wind flux earlier in the mission and the cometary momentum flux as measured by ICA becomes roughly an order of magnitude higher than previous and later solar wind fluxes. We also examine the changes in flux on two excursions, one on the dayside and one on the nightside of the comet, and see that during the nightside excursion, the cometary ion fluxes drop off roughly with the square of the distance from the comet. During the dayside excursion the flux was approximately constant, indicating that the excursion distance was small compared to the region where the observed ions were produced. ICA does not measure the lowest energy ions, so we also discuss the energy and momentum of the full ion population based on density estimates from the LAP and MIP instruments.</p>

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