scholarly journals On the Variation of Intermittency of Fast and Slow Solar Wind With Radial Distance, Heliospheric Latitude, and Solar Cycle

2021 ◽  
Vol 7 ◽  
Author(s):  
Anna Wawrzaszek ◽  
Marius Echim
Keyword(s):  
Solar Wind ◽  
Solar Cycle ◽  
Current Knowledge ◽  
Radial Distance ◽  
Multifractal Spectrum ◽  
Solar Wind Plasma ◽  
Distribution Functions ◽  
Slow Solar Wind ◽  
Cycle Phase ◽  
Magnetic Fluctuations

Intermittency, an important property of astrophysical plasma turbulence, is studied extensively during last decades from in-situ measurements of the solar wind plasma and magnetic field in the ecliptic plane and at higher latitudes, and heliocentric distances between 0.3 and 5 Astronomical Units. In this paper, we review the main findings on intermittency derived from investigation of solar wind turbulence for the inertial range of scales. It turns out that our current knowledge on the evolution of intermittency in the heliosphere is based on two missions, Helios two and Ulysses. We discuss the importance of data selection methodologies and applications for heliospheric spacecraft, the different data analysis techniques (the anomalous scaling of the structure function, the non-Gaussianity of the probability distribution functions, the local intermittency measure estimated from a wavelet representation and the multifractal spectrum). Studies show that Alvénic solar wind is less intermittent but reveals increase with the radial distance. Moreover, intermittency is stronger for the magnetic than for velocity fluctuations and is considered to be responsible for the increase with the radial distance of the anisotropy of magnetic fluctuations. The intermittency of fast solar wind at solar minimum decreases with latitude. Finally, the level of intermittency in the solar wind depends on solar cycle phase, reflecting the changes of the state of solar wind and suggesting that the deeper study of origin of fast and slow wind can further improve our understanding of the intermittency.

scholarly journals Ion-driven Instabilities in the Inner Heliosphere. I. Statistical Trends

2021 ◽  
Vol 923 (1) ◽  
pp. 116
Author(s):  
Mihailo M. Martinović ◽  
Kristopher G. Klein ◽  
Tereza Ďurovcová ◽  
Benjamin L. Alterman
Keyword(s):  
Solar Wind ◽  
Particle Interaction ◽  
Radial Distance ◽  
Solar Wind Plasma ◽  
Distribution Functions ◽  
Nyquist Criterion ◽  
Velocity Distribution Functions ◽  
Instability Growth ◽  
Statistical Trends ◽  
The Impact

Abstract Instabilities described by linear theory characterize an important form of wave–particle interaction in the solar wind. We diagnose unstable behavior of solar wind plasma between 0.3 and 1 au via the Nyquist criterion, applying it to fits of ∼1.5M proton and α particle Velocity Distribution Functions (VDFs) observed by Helios I and II. The variation of the fraction of unstable intervals with radial distance from the Sun is linear, signaling a gradual decline in the activity of unstable modes. When calculated as functions of the solar wind velocity and Coulomb number, we obtain more extreme, exponential trends in the regions where collisions appear to have a notable influence on the VDF. Instability growth rates demonstrate similar behavior, and significantly decrease with Coulomb number. We find that for a nonnegligible fraction of observations, the proton beam or secondary component might not be detected, due to instrument resolution limitations, and demonstrate that the impact of this issue does not affect the main conclusions of this work.

scholarly journals Perturbations of the solar wind flow by radial and latitudinal pick-up ion pressure gradients

2004 ◽  
Vol 22 (6) ◽  
pp. 2229-2238 ◽  
Author(s):  
H. J. Fahr ◽  
K. Scherer
Keyword(s):  
Solar Wind ◽  
Radial Distance ◽  
Solar Wind Plasma ◽  
Slow Solar Wind ◽  
Pressure Gradients ◽  
Quantitative Calculation ◽  
Symmetric Density ◽  
Solar Wind Flow ◽  
Loading Effects ◽  
Density Perturbations

Abstract. It has been found that pick-up ions at their dynamical incorporation into the solar wind modify the original conditions of the asymptotic solar wind plasma flow. In this respect, it has meanwhile been revealed in many papers that these type of solar wind modifications, i.e. deceleration and decrease of effective Mach number, are not only due to the pick-up ion loading effects, but also to the action of pick-up ion pressure gradients. Up to now only the effects of radial pick-up ion pressure gradients were considered, however, analogously but latitudinal pressure gradients also appear to be important. Here we study the effects of radial and latitudinal pick-up ion pressure gradients, occurring especially during solar minimum conditions at mid-latitude regions where slow solar wind streams change to fast solar wind streams. First, we give estimates of the latitudinal wind components connected with these gradients, and then after revealing its importance, present a more quantitative calculation of solar wind velocity and density perturbations resulting from these pressure forces. It is shown that the relative density perturbations near and in the ecliptic increase with radial distance and thus may well explain the measured non-spherically symmetric density decrease with distance. We also show that the solar wind decelerations actually seen with Voyager-1/2 are in conciliation with interstellar hydrogen densities of nH∞≥0.1cm-3, in contrast to earlier claims for nH∞=0.05cm-3.

Reversibility of Turbulent and Non-Collisional Plasmas: Solar Wind

2019 ◽  
Vol 15 (S354) ◽  
pp. 363-366
Author(s):  
Belén Acosta ◽  
Denisse Pastén ◽  
Pablo S. Moya
Keyword(s):  
Magnetic Field ◽  
Time Series ◽  
Solar Wind ◽  
Solar Wind Plasma ◽  
Magnetized Plasma ◽  
Slow Solar Wind ◽  
Magnetic Fluctuations ◽  
Particle In Cell ◽  
Leibler Divergence ◽  
Fast Wind

AbstractWe have studied turbulent plasma as a complex system applying the method known as Horizontal Visibility Graph (HVG) to obtain the Kullback-Leibler Divergence (KLD) as a first approach to characterize the reversibility of the time series of the magnetic fluctuations. For this, we have developed the method on Particle In Cell (PIC) simulations for a magnetized plasma and on solar wind magnetic time series, considering slow and fast wind. Our numerical results show that low irreversibility values are verified for magnetic field time series associated with Maxwellian distributions. In addition, considering the solar wind plasma, our preliminary results seem to indicate that greater irreversibility degrees are reached by the magnetic field associated with slow solar wind.

Ulysses solar wind plasma observations during the declining phase of solar cycle 22

1995 ◽  
Vol 16 (9) ◽  
pp. 85-94 ◽  
Author(s):  
J.L. Phillips ◽  
S.J. Bame ◽  
W.C. Feldman ◽  
J.T. Gosling ◽  
C.M. Hammond ◽  
...  
Keyword(s):  
Solar Wind ◽  
Solar Cycle ◽  
Solar Wind Plasma

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.

scholarly journals Solar wind and kinetic heliophysics

2018 ◽  
Vol 36 (6) ◽  
pp. 1607-1630 ◽  
Author(s):  
Eckart Marsch
Keyword(s):  
Solar Wind ◽  
Interplanetary Space ◽  
Coronal Holes ◽  
Heavy Ion ◽  
Alfven Waves ◽  
Distribution Functions ◽  
Slow Solar Wind ◽  
Alfvén Waves ◽  
The Sun ◽  
Collisionless Dissipation

Abstract. This paper reviews recent aspects of solar wind physics and elucidates the role Alfvén waves play in solar wind acceleration and turbulence, which prevail in the low corona and inner heliosphere. Our understanding of the solar wind has made considerable progress based on remote sensing, in situ measurements, kinetic simulation and fluid modeling. Further insights are expected from such missions as the Parker Solar Probe and Solar Orbiter. The sources of the solar wind have been identified in the chromospheric network, transition region and corona of the Sun. Alfvén waves excited by reconnection in the network contribute to the driving of turbulence and plasma flows in funnels and coronal holes. The dynamic solar magnetic field causes solar wind variations over the solar cycle. Fast and slow solar wind streams, as well as transient coronal mass ejections, are generated by the Sun's magnetic activity. Magnetohydrodynamic turbulence originates at the Sun and evolves into interplanetary space. The major Alfvén waves and minor magnetosonic waves, with an admixture of pressure-balanced structures at various scales, constitute heliophysical turbulence. Its spectra evolve radially and develop anisotropies. Numerical simulations of turbulence spectra have reproduced key observational features. Collisionless dissipation of fluctuations remains a subject of intense research. Detailed measurements of particle velocity distributions have revealed non-Maxwellian electrons, strongly anisotropic protons and heavy ion beams. Besides macroscopic forces in the heliosphere, local wave–particle interactions shape the distribution functions. They can be described by the Boltzmann–Vlasov equation including collisions and waves. Kinetic simulations permit us to better understand the combined evolution of particles and waves in the heliosphere.

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 wind plasma associated with Dst -50 nT during solar cycle 24

2017 ◽  
Vol 12 (21) ◽  
pp. 280-285
Author(s):  
R.Singh P. ◽  
Ahmad S. ◽  
Nigam B. ◽  
K. Chamadia P. ◽  
K. Saxena A. ◽  
...  
Keyword(s):  
Solar Wind ◽  
Solar Cycle ◽  
Solar Wind Plasma ◽  
Solar Cycle 24 ◽  
Cycle 24

scholarly journals Different magnetospheric modes: solar wind driving and coupling efficiency

2009 ◽  
Vol 27 (11) ◽  
pp. 4281-4291 ◽  
Author(s):  
N. Partamies ◽  
T. I. Pulkkinen ◽  
R. L. McPherron ◽  
K. McWilliams ◽  
C. R. Bryant ◽  
...  
Keyword(s):  
Solar Wind ◽  
Solar Wind Speed ◽  
Coupling Efficiency ◽  
Slow Solar Wind ◽  
Cycle Phase ◽  
Particle Injection ◽  
Superposed Epoch Analysis ◽  
Magnetospheric Convection ◽  
Epoch Analysis ◽  
Steady Convection

Abstract. This study describes a systematic statistical comparison of isolated non-storm substorms, steady magnetospheric convection (SMC) intervals and sawtooth events. The number of events is approximately the same in each group and the data are taken from about the same years to avoid biasing by different solar cycle phase. The very same superposed epoch analysis is performed for each event group to show the characteristics of ground-based indices (AL, PCN, PC potential), particle injection at the geostationary orbit and the solar wind and IMF parameters. We show that the monthly occurrence of sawtooth events and isolated non-stormtime substorms closely follows maxima of the geomagnetic activity at (or close to) the equinoxes. The most strongly solar wind driven event type, sawtooth events, is the least efficient in coupling the solar wind energy to the auroral ionosphere, while SMC periods are associated with the highest coupling ratio (AL/EY). Furthermore, solar wind speed seems to play a key role in determining the type of activity in the magnetosphere. Slow solar wind is capable of maintaining steady convection. During fast solar wind streams the magnetosphere responds with loading–unloading cycles, represented by substorms during moderately active conditions and sawtooth events (or other storm-time activations) during geomagnetically active conditions.

scholarly journals Combined electron firehose and electromagnetic ion cyclotron instabilities: quasilinear approach

2020 ◽  
Vol 499 (1) ◽  
pp. 659-667
Author(s):  
Z Ali ◽  
M Sarfraz ◽  
P H Yoon
Keyword(s):  
Solar Wind ◽  
Dynamical Evolution ◽  
Solar Wind Plasma ◽  
Distribution Functions ◽  
Temperature Anisotropy ◽  
Spatial And Temporal Scales ◽  
Proton Temperature ◽  
Ion Cyclotron ◽  
Velocity Distribution Functions ◽  
High Beta

ABSTRACT Various plasma waves and instabilities are abundantly present in the solar wind plasma, as evidenced by spacecraft observations. Among these, propagating modes and instabilities driven by temperature anisotropies are known to play a significant role in the solar wind dynamics. In situ measurements reveal that the threshold conditions for these instabilities adequately explain the solar wind conditions at large heliocentric distances. This paper pays attention to the combined effects of electron firehose instability driven by excessive parallel electron temperature anisotropy (T⊥e < T∥e) at high beta conditions, and electromagnetic ion cyclotron instability driven by excessive perpendicular proton temperature anisotropy (T⊥i > T∥i). By employing quasilinear kinetic theory based upon the assumption of bi-Maxwellian velocity distribution functions for protons and electrons, the dynamical evolution of the combined instabilities and their mutual interactions mediated by the particles is explored in depth. It is found that while in some cases, the two unstable modes are excited and saturated at distinct spatial and temporal scales, in other cases, the two unstable modes are intermingled such that a straightforward interpretation is not so easy. This shows that when the dynamics of protons and electrons are mutually coupled and when multiple unstable modes are excited in the system, the dynamical consequences can be quite complex.

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