scholarly journals Significance of Bernoulli Integral Terms for the Solar Wind Protons at 1 au

2021 ◽  
Vol 11 (10) ◽  
pp. 4643
Author(s):  
Georgios Nicolaou ◽  
George Livadiotis ◽  
Mihir I. Desai
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Energy Conservation ◽  
Plasma Density ◽  
Polytropic Index ◽  
Field Observations ◽  
Accurate Calculation ◽  
Solar Wind Proton ◽  
Wind Spacecraft ◽  
Bernoulli Integral

The Bernoulli integral describes the energy conservation of a fluid along specific streamlines. The integral is the sum of individual terms that contain the plasma density, speed, temperature, and magnetic field. Typical solar wind analyses use the fluctuations of the Bernoulli integral as a criterion to identify different plasma streamlines from single spacecraft observations. However, the accurate calculation of the Bernoulli integral requires accurately determining the plasma polytropic index from the analysis of density and temperature observations. To avoid this complexity, we can simplify the calculations by keeping only the dominant terms of the integral. Here, we analyze proton plasma and magnetic field observations obtained by the Wind spacecraft at 1 au, during 1995. We calculate the Bernoulli integral terms and quantify their significance by comparing them with each other. We discuss potential simplifications of the calculations in the context of determining solar wind proton thermodynamics using single spacecraft observations.

scholarly journals Experimental and numerical investigation of plasma parameters in the magnetosheath

2018 ◽  
Vol 145 ◽  
pp. 03003
Author(s):  
Polya Dobreva ◽  
Monio Kartalev ◽  
Olga Nitcheva ◽  
Natalia Borodkova ◽  
Georgy Zastenker
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Numerical Investigation ◽  
Euler Equations ◽  
Ideal Gas ◽  
Bow Shock ◽  
Plasma Parameters ◽  
Wind Spacecraft ◽  
The Magnetic Field ◽  
Good Agreement

We investigate the behaviour of the plasma parameters in the magnetosheath in a case when Interball-1 satellite stayed in the magnetosheath, crossing the tail magnetopause. In our analysis we apply the numerical magnetosheath-magnetosphere model as a theoretical tool. The bow shock and the magnetopause are self-consistently determined in the process of the solution. The flow in the magnetosheath is governed by the Euler equations of compressible ideal gas. The magnetic field in the magnetosphere is calculated by a variant of the Tsyganenko model, modified to account for an asymmetric magnetopause. Also, the magnetopause currents in Tsyganenko model are replaced by numericaly calulated ones. Measurements from WIND spacecraft are used as a solar wind monitor. The results demonstrate a good agreement between the model-calculated and measured values of the parameters under investigation.

Interaction of the solar wind with the planet Mars: Phobos 2 magnetic field observations

1991 ◽  
Vol 39 (1-2) ◽  
pp. 75-81 ◽  
Author(s):  
W. Riedler ◽  
K. Schwingenschuh ◽  
H. Lichtenegger ◽  
D. Möhlmann ◽  
J. Rustenbach ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Field Observations

scholarly journals Evidence for Plasma Heating at Thin Current Sheets in the Solar Wind

2022 ◽  
Vol 924 (2) ◽  
pp. L22
Author(s):  
Zilu Zhou ◽  
Xiaojun Xu ◽  
Pingbing Zuo ◽  
Yi Wang ◽  
Qi Xu ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Plasma Heating ◽  
Magnetic Field Direction ◽  
Current Sheets ◽  
Proton Temperature ◽  
Fast Wind ◽  
Wind Spacecraft ◽  
Slow Wind ◽  
The Magnetic Field

Abstract Plasma heating at thin current sheets in the solar wind is examined using magnetic field and plasma data obtained by the WIND spacecraft in the past 17 years from 2004 to 2019. In this study, a thin current sheet is defined by an abrupt rotation (larger than 45°) of the magnetic field direction in 3 s. A total of 57,814 current sheets have been identified, among which 25,018 current sheets are located in the slow wind and 19,842 current sheets are located in the fast wind. Significant plasma heating is found at current sheets in both slow and fast wind. Proton temperature increases more significantly at current sheets in the fast wind than in the slow wind, while the enhancement in electron temperature is less remarkable at current sheets in the fast wind. The results reveal that plasma heating commonly exists at thin current sheets in the solar wind regardless of the wind speed, but the underlying heating mechanisms might be different.

Theoretical plasma distributions consistent with Ulysses magnetic field observations in a solar wind tangential discontinuity

Solar Physics ◽  
1996 ◽  
Vol 166 (2) ◽  
pp. 415-422 ◽  
Author(s):  
J. De Keyser ◽  
M. Roth ◽  
J. Lemaire ◽  
B. T. Tsurutani ◽  
C. M. Ho ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Tangential Discontinuity ◽  
Field Observations

Turbulent properties of CME-driven sheath regions

2020 ◽  
Author(s):  
Dominique Fontaine ◽  
Emiliya Kilpua ◽  
Matti Alalathi ◽  
Erika Palmerio ◽  
Adnane Osmane ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Interplanetary Coronal Mass Ejections ◽  
Physical Mechanisms ◽  
Complex Process ◽  
Wind Spacecraft ◽  
Sheath Formation ◽  
Field Fluctuations ◽  
Key Drivers ◽  
Good Agreement

<p>We have analysed magnetic field fluctuations in sheath regions ahead of interplanetary coronal mass ejections (CMEs). CME sheaths are one of the key drivers of space weather disturbances, but their detailed structure and formation are relatively poorly understood. The level of magnetic field fluctuations in sheaths is generally much higher than in the ambient solar wind. We compare fluctuation properties in different parts of a sheath observed at the orbit of Earth using by the Wind spacecraft. Our findings show that in general the transition from the preceding solar wind to the sheath generates new fluctuations that are mostly compressive and which increase intermittency.  Spectral indices are mostly steeper than the -5/3 Kolmogorov index. The standard p-model did not show a good fit (in either the Kraichnan or Kolmogorov form), but the extended p-model was in a very good agreement. This suggests that turbulence may not be fully developed in CME sheaths in general. Our study also reveals that turbulent properties can vary considerably between different sheaths and in different subregions of the sheath, and can be significantly modified by the presence of small coherent structures. The findings support the view that sheath formation is a complex process with multiple physical mechanisms playing a role in generating the turbulence. </p>

Long-term properties of the solar wind and their relation to solar cycles

2020 ◽  
Author(s):  
Anna Salohub ◽  
Jana Šafránkova ◽  
Zdeněk Němeček ◽  
Lubomír Přech ◽  
Tereza Ďurovcová
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Dynamic Pressure ◽  
Solar Wind Speed ◽  
Solar Wind Plasma ◽  
Solar Cycles ◽  
Plasma Parameters ◽  
Wind Spacecraft ◽  
Slow Wind ◽  
Density Dynamic

<p>The solar wind variations during particular solar cycles have been described in many previous studies including the solar cycle 23 that was characterized by a long, deep, and very complex solar minimum with very low values of many solar wind parameters.</p><p>Using statistical methods, we analyzed 25 years of Wind spacecraft measurements with motivation to reveal differences and similarities in magnetic field components and solar wind plasma parameters in individual solar cycles. We tracked the changes of the solar magnetic field strength, and components, solar wind speed, density, dynamic pressure, temperature, and composition). Except quiet solar wind conditions during solar minima and maxima, we also selected significant discontinuities (ICME and CIRs) and investigated their influence on profiles of average parameters. For this, we followed other quantities connected with their presence as their average front normals, regions of transitions between high and slow wind streams, special interplanetary magnetic field orientations, etc.). We discuss a behavior of investigated parameters over solar cycles as well as on shorter time scales (in the order of days and hours).</p>

scholarly journals Long-Term Independence of Solar Wind Polytropic Index on Plasma Flow Speed

Entropy ◽  
2018 ◽  
Vol 20 (10) ◽  
pp. 799 ◽  
Author(s):  
George Livadiotis
Keyword(s):  
Solar Wind ◽  
Plasma Flow ◽  
Solar Wind Speed ◽  
Solar Wind Plasma ◽  
Flow Speed ◽  
Polytropic Index ◽  
Solar Cycles ◽  
Solar Wind Proton ◽  
Plasma Flow Speed

The paper derives the polytropic indices over the last two solar cycles (years 1995–2017) for the solar wind proton plasma near Earth (~1 AU). We use ~92-s datasets of proton plasma moments (speed, density, and temperature), measured from the Solar Wind Experiment instrument onboard Wind spacecraft, to estimate the moving averages of the polytropic index, as well as their weighted means and standard errors as a function of the solar wind speed and the year of measurements. The derived long-term behavior of the polytropic index agrees with the results of other previous methods. In particular, we find that the polytropic index remains quasi-constant with respect to the plasma flow speed, in agreement with earlier analyses of solar wind plasma. It is shown that most of the fluctuations of the polytropic index appear in the fast solar wind. The polytropic index remains quasi-constant, despite the frequent entropic variations. Therefore, on an annual basis, the polytropic index of the solar wind proton plasma near ~1 AU can be considered independent of the plasma flow speed. The estimated all-year weighted mean and its standard error is γ = 1.86 ± 0.09.

scholarly journals Compressive fluctuations in the solar wind and their polytropic index

1996 ◽  
Vol 14 (5) ◽  
pp. 510-517 ◽  
Author(s):  
B. Bavassano ◽  
R. Bruno ◽  
H. Rosenbauer
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Solar Rotation ◽  
Polytropic Index ◽  
Constant Density ◽  
The Sun ◽  
Thermal Pressure ◽  
Fast Wind ◽  
Pressure Equilibrium ◽  
Interplanetary Plasma

Abstract. Magnetohydrodynamic compressive fluctuations of the interplanetary plasma in the region from 0.3 to 1 AU have been characterized in terms of their polytropic index. Following Chandrasekhar's approach to polytropic fluids, this index has been determined through a fit of the observed variations of density and temperature. At least three different classes of fluctuations have been identified: (1) variations at constant thermal pressure, in low-speed solar wind and without a significant dependence on distance, (2) adiabatic variations, mainly close to 1 AU and without a relevant dependence on wind speed, and (3) variations at nearly constant density, in fast wind close to 0.3 AU. Variations at constant thermal pressure are probably a subset of the ensemble of total-pressure balanced structures, corresponding to cases in which the magnetic field magnitude does not vary appreciably throughout the structure. In this case the pressure equilibrium has to be assured by its thermal component only. The variations may be related to small flow-tubes with approximately the same magnetic-field intensity, convected by the wind in conditions of pressure equilibrium. This feature is mainly observed in low-velocity solar wind, in agreement with the magnetic topology (small open flow-tubes emerging through an ensemble of closed structures) expected for the source region of slow wind. Variations of adiabatic type may be related to magnetosonic waves excited by pressure imbalances between contiguous flow-tubes. Such imbalances are probably built up by interactions between wind flows with different speeds in the spiral geometry induced by the solar rotation. This may account for the fact that they are mainly found at a large distance from the sun. Temperature variations at almost constant density are mostly found in fast flows close to the sun. These are the solar wind regions with the best examples of incompressible behaviour. They are characterized by very stable values for particle density and magnetic intensity, and by fluctuations of Alfvénic type. It is likely that temperature fluctuations in these regions are a remnant of thermal features in the low solar atmosphere. In conclusion, the polytropic index appears to be a useful tool to understand the nature of the compressive turbulence in the interplanetary plasma, as far as the frozen-in magnetic field does not play a crucial role.

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