scholarly journals Dynamical evolution of anisotropies of the solar wind magnetic turbulent outer scale

2011 ◽  
Vol 7 (S286) ◽  
pp. 164-167
Author(s):  
M. E. Ruiz ◽  
S. Dasso ◽  
W. H. Matthaeus ◽  
E. Marsch ◽  
J. M. Weygand
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Dynamical Evolution ◽  
The Sun ◽  
Magnetic Fluctuations ◽  
Integral Scale ◽  
Outer Heliosphere ◽  
Local Mean ◽  
And Diffusion ◽  
Inner Heliosphere

AbstractThe evolution of the turbulent properties in the solar wind, during the travel of the parcels of fluid from the Sun to the outer heliosphere still has several unanswered questions. In this work, we will present results of an study on the dynamical evolution of turbulent magnetic fluctuations in the inner heliosphere. We focused on the anisotropy of the turbulence integral scale, measured parallel and perpendicular to the direction of the local mean magnetic field, and study its evolution according to the aging of the plasma parcels observed at different heliodistances. As diagnostic tool we employed single-spacecraft correlation functions computed with observations collected by Helios 1 & 2 probes over nearly one solar cycle. Our results are consistent with driving modes with wave-vectors parallel to the direction of the local mean magnetic field near the Sun, and a progressive spectral transfer of energy to modes with perpendicular wave-vectors. Advances made in this direction, as those presented here, will contribute to our understanding of the magnetohydrodynamical turbulence and Alfvénic-wave activity for this system, and will provide a quantitative input for models of charged solar and galactic energetic particles propagation and diffusion throughout the inner heliosphere.

MHD and Ion Kinetic Waves in Field-aligned Flows Observed by Parker Solar Probe

2021 ◽  
Vol 922 (2) ◽  
pp. 188
Author(s):  
L.-L. Zhao ◽  
G. P. Zank ◽  
J. S. He ◽  
D. Telloni ◽  
L. Adhikari ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Whistler Wave ◽  
Spectral Energy ◽  
Small Scale ◽  
The Sun ◽  
Fast Mode ◽  
Magnetic Fluctuations ◽  
Background Magnetic Field ◽  
Ion Cyclotron

Abstract Parker Solar Probe (PSP) observed predominately Alfvénic fluctuations in the solar wind near the Sun where the magnetic field tends to be radially aligned. In this paper, two magnetic-field-aligned solar wind flow intervals during PSP’s first two orbits are analyzed. Observations of these intervals indicate strong signatures of parallel/antiparallel-propagating waves. We utilize multiple analysis techniques to extract the properties of the observed waves in both magnetohydrodynamic (MHD) and kinetic scales. At the MHD scale, outward-propagating Alfvén waves dominate both intervals, and outward-propagating fast magnetosonic waves present the second-largest contribution in the spectral energy density. At kinetic scales, we identify the circularly polarized plasma waves propagating near the proton gyrofrequency in both intervals. However, the sense of magnetic polarization in the spacecraft frame is observed to be opposite in the two intervals, although they both possess a sunward background magnetic field. The ion-scale plasma wave observed in the first interval can be either an inward-propagating ion cyclotron wave (ICW) or an outward-propagating fast-mode/whistler wave in the plasma frame, while in the second interval it can be explained as an outward ICW or inward fast-mode/whistler wave. The identification of the exact kinetic wave mode is more difficult to confirm owing to the limited plasma data resolution. The presence of ion-scale waves near the Sun suggests that ion cyclotron resonance may be one of the ubiquitous kinetic physical processes associated with small-scale magnetic fluctuations and kinetic instabilities in the inner heliosphere.

scholarly journals The evolution of inverted magnetic fields through the inner heliosphere

2020 ◽  
Vol 494 (3) ◽  
pp. 3642-3655 ◽  
Author(s):  
Allan R Macneil ◽  
Mathew J Owens ◽  
Robert T Wicks ◽  
Mike Lockwood ◽  
Sarah N Bentley ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Radial Distance ◽  
Occurrence Rate ◽  
Slow Solar Wind ◽  
The Sun ◽  
Radial Evolution ◽  
In Transit ◽  
The Magnetic Field ◽  
Inner Heliosphere

ABSTRACT Local inversions are often observed in the heliospheric magnetic field (HMF), but their origins and evolution are not yet fully understood. Parker Solar Probe has recently observed rapid, Alfvénic, HMF inversions in the inner heliosphere, known as ‘switchbacks’, which have been interpreted as the possible remnants of coronal jets. It has also been suggested that inverted HMF may be produced by near-Sun interchange reconnection; a key process in mechanisms proposed for slow solar wind release. These cases suggest that the source of inverted HMF is near the Sun, and it follows that these inversions would gradually decay and straighten as they propagate out through the heliosphere. Alternatively, HMF inversions could form during solar wind transit, through phenomena such velocity shears, draping over ejecta, or waves and turbulence. Such processes are expected to lead to a qualitatively radial evolution of inverted HMF structures. Using Helios measurements spanning 0.3–1 au, we examine the occurrence rate of inverted HMF, as well as other magnetic field morphologies, as a function of radial distance r, and find that it continually increases. This trend may be explained by inverted HMF observed between 0.3 and 1 au being primarily driven by one or more of the above in-transit processes, rather than created at the Sun. We make suggestions as to the relative importance of these different processes based on the evolution of the magnetic field properties associated with inverted HMF. We also explore alternative explanations outside of our suggested driving processes which may lead to the observed trend.

Statistical Research of the Intermittency and Cascade of Solar Wind Turbulence Based on Analysis of PSP Measurements

2020 ◽  
Author(s):  
Ying Wang ◽  
Jiansen He ◽  
Die Duan ◽  
Xingyu Zhu
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Break Point ◽  
Inertial Range ◽  
Scaling Exponent ◽  
The Sun ◽  
Peak Point ◽  
Solar Wind Turbulence ◽  
Wind Turbulence ◽  
Inner Heliosphere

<p>By analyzing the turbulent magnetic field data from PSP, we find that: the solar wind turbulence in the inner heliosphere close to the Sun has formed the transition from multifractal intermittency at MHD scales to monofractal intermittency at kinetic scales. The order-dependent scaling exponent of the multi-order structure function shows a concave profile indicating the multifractal property at MHD scales, while its counterpart at kinetic scales shows a linear trend suggesting the monofractal property. We also find that, the closer to the sun, the more obvious the concave profile of the scaling exponent in the inertial range, which indicates that the multifractal characteristic of the magnetic field turbulence intermittency is also more evident when getting closer to the Sun.</p><p>Based on the Castaing description of the probability distribution function(PDF) of the disturbance difference, the key parameters(μ & λ^2) of the Castaing function are estimated as a function of scale. We find that: (1) when close to the sun (R~0.17 AU), the break point of μ is about 0.2 second, and the peak point of λ^2 is about 0.6 second, the two of which are about three times different in scale; (2) when far from the sun (R~0.8 AU), the break point of μ is about 1 second and the peak point of λ^2 is about 3 seconds, the two of which are also about three times different in scale. We also point out that the profiles (including the break/peak position) of both the parameters (μ & λ^2) along with the scale together determine the profile (including the spectral breaks) of the power spectrum.</p><p>Following the PP98 model function of incompressible MHD turbulent cascade rate (εZ), we first compared the cascade rate εZ with εB=<δB^3>/τ at the distance close to the sun, we find that the two trends over scales are in good agreement with one another. We therefore suggest that, to some extent (e.g. in the inertial region), εB=<δB^3>/τ can be used as a proxy of the cascade rate εZ. For the first time, by statistical analysis, we obtained that εB satisfies the following relation with the scale and the heliocentric distance: εB=((τ/τ0)^α)((r/r0)^β). In the inertial range, α changes from about -0.5 to about 0.5 as r increases from 0.17 AU to 0.81 AU, and β is about 6.4; in the kenetic range, when r increases from 0.17 AU to 0.25 AU, α keeps at about 2, and β is about 12.8. The εB(τ,r) expression given in this work, is believed to help understanding the transport and cascade processes of solar wind turbulence in the inner heliosphere. </p><p>Corresponding author:<br>Jiansen HE, [email protected]</p><p>Acknowledgements:<br>We would like to thank the PSP team for providing the data of PSP to the public.</p>

Solar Wind Turbulence at Kinetic Scales in the inner Heliosphere

2020 ◽  
Author(s):  
Olga Alexandrova ◽  
Vamsee Jagarlamudi ◽  
Milan Maksimovic ◽  
Petr Hellinger ◽  
Yuri Shprits ◽  
...  
Keyword(s):  
Solar Wind ◽  
Time Domain ◽  
Coherent Structures ◽  
Larmor Radius ◽  
The Sun ◽  
Magnetic Fluctuations ◽  
Magnetic Vortices ◽  
Dissipation Scale ◽  
The Time Domain ◽  
Inner Heliosphere

<p>We study magnetic fluctuations at sub-ion scales and down to sub-electron scales using Helios/SCM measurements in the inner Heliosphere and Cluster/STAFF data at the Earth's orbit. Using these data we test the generality of the kinetic spectrum and we show that it follows the ~k<sup>-8/3</sup>exp(-kl<sub>d</sub>) law at different radial distances from the Sun (k being a wavenumber). We show as well that the dissipation scale l<sub>d</sub> correlates well with the electron Larmor radius ρ<sub>e</sub> at 0.3 AU and at 1 AU. Then, in the time domain, at 1 AU, using the wavelet transform, we study the nature of magnetic fluctuations, which form the kinetic spectrum. It appears, that the spectrum is dominated by non-linear coherent structures in the form of magnetic vortices with the smallest resolved scale of the order of ρ<sub>e</sub>. Finally, we comparer our results with measurements of the Parker Solar Probe/FIELDS and, hopefully, of the Solar Orbiter/RPW in the inner Heliosphere.</p>

scholarly journals Geometry of Magnetic Fluctuations near the Sun from the Parker Solar Probe

2021 ◽  
Vol 923 (2) ◽  
pp. 193
Author(s):  
R. Bandyopadhyay ◽  
D. J. McComas
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Large Scale ◽  
Inertial Range ◽  
Local Magnetic Field ◽  
The Sun ◽  
Magnetic Fluctuations ◽  
Outer Scale ◽  
Degree Of Anisotropy ◽  
Dissipation Range

Abstract Solar wind magnetic fluctuations exhibit anisotropy due to the presence of a mean magnetic field in the form of the Parker spiral. Close to the Sun, direct measurements were not available until the recently launched Parker Solar Probe (PSP) mission. The nature of the anisotropy and geometry of the magnetic fluctuations play a fundamental role in dissipation processes and in the transport of energetic particles in space. Using PSP data, we present measurements of the geometry and anisotropy of the inner heliosphere magnetic fluctuations, from fluid to kinetic scales. The results are surprising and different from 1 au observations. We find that fluctuations evolve characteristically with size scale. However, unlike 1 au solar wind, at the outer scale, the fluctuations are dominated by wavevectors quasi-parallel to the local magnetic field. In the inertial range, average wavevectors become less field aligned, but still remain more field aligned than near-Earth solar wind. In the dissipation range, the wavevectors become almost perpendicular to the local magnetic field in the dissipation range, to a much higher degree than those indicated by 1 au observations. We propose that this reduced degree of anisotropy in the outer scale and inertial range is due to the nature of large-scale forcing outside the solar corona.

scholarly journals Solar cycle changes of large-scale solar wind structure

2009 ◽  
Vol 5 (S264) ◽  
pp. 356-358 ◽  
Author(s):  
P. K. Manoharan
Keyword(s):  
Solar Wind ◽  
Solar Cycle ◽  
Large Scale ◽  
Interplanetary Space ◽  
The Sun ◽  
Wind Structure ◽  
Level Of Activity ◽  
Solar Wind Structure ◽  
Current Minimum ◽  
Inner Heliosphere

AbstractIn this paper, I present the results on large-scale evolution of density turbulence of solar wind in the inner heliosphere during 1985–2009. At a given distance from the Sun, the density turbulence is maximum around the maximum phase of the solar cycle and it reduces to ~70%, near the minimum phase. However, in the current minimum of solar activity, the level of turbulence has gradually decreased, starting from the year 2005, to the present level of ~30%. These results suggest that the source of solar wind changes globally, with the important implication that the supply of mass and energy from the Sun to the interplanetary space has significantly reduced in the present low level of activity.

scholarly journals Aging of anisotropy of solar wind magnetic fluctuations in the inner heliosphere

2011 ◽  
Vol 116 (A10) ◽  
pp. n/a-n/a ◽  
Author(s):  
M. E. Ruiz ◽  
S. Dasso ◽  
W. H. Matthaeus ◽  
E. Marsch ◽  
J. M. Weygand
Keyword(s):  
Solar Wind ◽  
Magnetic Fluctuations ◽  
Inner Heliosphere

The Sun

2015 ◽  
Author(s):  
Joanna D. Haigh ◽  
Peter Cargill
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Solar Atmosphere ◽  
Space Weather ◽  
Extreme Ultraviolet ◽  
The Sun ◽  
Base Level ◽  
Earth’S Climate ◽  
The Magnetic Field ◽  
Terrestrial Magnetic Field

This chapter discusses how there are four general factors that contribute to the Sun's potential role in variations in the Earth's climate. First, the fusion processes in the solar core determine the solar luminosity and hence the base level of radiation impinging on the Earth. Second, the presence of the solar magnetic field leads to radiation at ultraviolet (UV), extreme ultraviolet (EUV), and X-ray wavelengths which can affect certain layers of the atmosphere. Third, the variability of the magnetic field over a 22-year cycle leads to significant changes in the radiative output at some wavelengths. Finally, the interplanetary manifestation of the outer solar atmosphere (the solar wind) interacts with the terrestrial magnetic field, leading to effects commonly called space weather.

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.

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