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 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.

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 Cometary ion dynamics observed in the close vicinity of comet 67P/Churyumov–Gerasimenko during the intermediate activity period

2018 ◽  
Vol 613 ◽  
pp. A57 ◽  
Author(s):  
L. Berčič ◽  
E. Behar ◽  
H. Nilsson ◽  
G. Nicolaou ◽  
G. Stenberg Wieser ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Electric Field ◽  
Field Measurements ◽  
Distribution Functions ◽  
Activity Period ◽  
Ion Density ◽  
Ion Flow ◽  
Velocity Distribution Functions ◽  
Comet 67P

Aims. Cometary ions are constantly produced in the coma, and once produced they are accelerated and eventually escape the coma. We describe and interpret the dynamics of the cometary ion flow, of an intermediate active comet, very close to the nucleus and in the terminator plane. Methods. We analysed in situ ion and magnetic field measurements, and characterise the velocity distribution functions (mostly using plasma moments). We propose a statistical approach over a period of one month. Results. On average, two populations were observed, separated in phase space. The motion of the first is governed by its interaction with the solar wind farther upstream, while the second one is accelerated in the inner coma and displays characteristics compatible with an ambipolar electric field. Both populations display a consistent anti-sunward velocity component. Conclusions. Cometary ions born in different regions of the coma are seen close to the nucleus of comet 67P/Churyumov–Gerasimenko with distinct motions governed in one case by the solar wind electric field and in the other case by the position relative to the nucleus. A consistent anti-sunward component is observed for all cometary ions. An asymmetry is found in the average cometary ion density in a solar wind electric field reference frame, with higher density in the negative (south) electric field hemisphere. There is no corresponding signature in the average magnetic field strength.

scholarly journals Sonification of Astronomical Data

2011 ◽  
Vol 7 (S285) ◽  
pp. 133-136 ◽  
Author(s):  
Wanda L. Diaz-Merced ◽  
Robert M. Candey ◽  
Nancy Brickhouse ◽  
Matthew Schneps ◽  
John C. Mannone ◽  
...  
Keyword(s):  
Solar Wind ◽  
Time Series Data ◽  
Solar Wind Plasma ◽  
Series Data ◽  
Astronomical Data ◽  
X Ray ◽  
The Earth ◽  
Polar Type ◽  
Mass Ejection ◽  
The Impact

AbstractThis document presents Java-based software called xSonify that uses a sonification technique (the adaptation of sound to convey information) to promote discovery in astronomical data. The prototype is designed to analyze two-dimensional data, such as time-series data. We demonstrate the utility of the sonification technique with examples applied to X-ray astronomy and solar data. We have identified frequencies in the Chandra X-Ray observations of EX Hya, a cataclysmic variable of the intermediate polar type. In another example we study the impact of a major solar flare, with its associated coronal mass ejection (CME), on the solar wind plasma (in particular the solar wind between the Sun and the Earth), and the Earth's magnetosphere.

scholarly journals Whistler waves observed by Solar Orbiter during its first orbit

2021 ◽  
Author(s):  
Matthieu Kretschmar ◽  
Thomas Chust ◽  
Daniel Graham ◽  
Volodya Krasnosekskikh ◽  
Lucas Colomban ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Electromagnetic Waves ◽  
Heliocentric Distance ◽  
Plasma Waves ◽  
Distribution Functions ◽  
The Sun ◽  
Whistler Waves ◽  
Velocity Distribution Functions ◽  
The Waves

<p>Plasma waves can play an important role in the evolution of the solar wind and the particle velocity distribution functions in particular. We analyzed the electromagnetic waves observed above a few Hz by the Radio Plasma Waves (RPW) instrument suite onboard Solar Orbiter, during its first orbit, which covered a distance from the Sun between 1 AU and 0.5 AU.  We identified the majority of the detected waves as whistler waves with frequency around  0.1 f_ce and right handed circular polarisation. We found these waves to be mostly aligned or anti aligned with the ambient magnetic field, and rarely oblique. We also present and discuss their direction of propagation and the variation of the waves' properties with heliocentric distance.</p>

On the multifractality of plasma turbulence in the solar wind

2019 ◽  
Vol 15 (S354) ◽  
pp. 371-374
Author(s):  
Sebastián Echeverría ◽  
Pablo S. Moya ◽  
Denisse Pastén
Keyword(s):  
Solar Wind ◽  
Velocity Distribution ◽  
Distribution Functions ◽  
Fluctuation Analysis ◽  
Magnetic Fluctuations ◽  
Multifractal Detrended Fluctuation Analysis ◽  
Particle In Cell ◽  
Velocity Distribution Functions ◽  
Detrended Fluctuation

AbstractIn this work we have analyzed turbulent plasma in the kinetic scale by the characterization of magnetic fluctuations time series. Considering numerical Particle-In-Cell (PIC) simulations we apply a method known as MultiFractal Detrended Fluctuation Analysis (MFDFA) to study the fluctuations of solar-wind-like plasmas in thermodynamic equilibrium (represented by Maxwellian velocity distribution functions), and out of equilibrium plasma represented by Tsallis velocity distribution functions, characterized by the kappa (κ) parameter, to stablish relations between the fractality of magnetic fluctuation and the kappa parameter.

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.

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