Polytropic Index of the Solar Wind Ions Near the Earth Calculated Using a Homogeneous Magnetohydrodynamic 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.

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A review of the SCOSTEP’s 5-year scientific program VarSITI—Variability of the Sun and Its Terrestrial Impact

Progress in Earth and Planetary Science ◽

10.1186/s40645-021-00410-1 ◽

2021 ◽

Vol 8 (1) ◽

Author(s):

Kazuo Shiokawa ◽

Katya Georgieva

Keyword(s):

Solar Wind ◽

Interplanetary Space ◽

Solar Wind Plasma ◽

The Sun ◽

Scientific Program ◽

Solar Cycles ◽

Grand Minimum ◽

The Earth ◽

Earth Connection ◽

Near Future

AbstractThe Sun is a variable active-dynamo star, emitting radiation in all wavelengths and solar-wind plasma to the interplanetary space. The Earth is immersed in this radiation and solar wind, showing various responses in geospace and atmosphere. This Sun–Earth connection variates in time scales from milli-seconds to millennia and beyond. The solar activity, which has a ~11-year periodicity, is gradually declining in recent three solar cycles, suggesting a possibility of a grand minimum in near future. VarSITI—variability of the Sun and its terrestrial impact—was the 5-year program of the scientific committee on solar-terrestrial physics (SCOSTEP) in 2014–2018, focusing on this variability of the Sun and its consequences on the Earth. This paper reviews some background of SCOSTEP and its past programs, achievements of the 5-year VarSITI program, and remaining outstanding questions after VarSITI.

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Foreshock ULF fluctuations near the Moon: THEMIS observations

10.5194/egusphere-egu21-2884 ◽

2021 ◽

Author(s):

Anna Salohub ◽

Jana Šafránková ◽

Zdeněk Němeček

Keyword(s):

Solar Wind ◽

Rest Frame ◽

Low Frequency ◽

Solar Wind Plasma ◽

Turbulent Plasma ◽

Bow Shock ◽

Ulf Waves ◽

The Moon ◽

Shock Surface ◽

The Earth

The foreshock is a region filled with a turbulent plasma located upstream the Earth&#8217;s bow shock where interplanetary magnetic field (IMF) lines are connected to the bow shock surface. In this region, ultra-low frequency (ULF) waves are generated due to the interaction of the solar wind plasma with particles reflected from the bow shock back into the solar wind. It is assumed that excited waves grow and they are convected through the solar wind/foreshock, thus the inner spacecraft (close to the bow shock) would observe larger wave amplitudes than the outer (far from the bow shock) spacecraft. The paper presents a statistical analysis of excited ULF fluctuations observed simultaneously by two closely separated THEMIS spacecraft orbiting the Moon under a nearly radial IMF. We found that ULF fluctuations (in the plasma rest frame) can be characterized as a mixture of transverse and compressional modes with different properties at both locations. We discuss the growth and/or damping of ULF waves during their propagation.

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Cellular automata model of magnetospheric-ionospheric coupling

Annales Geophysicae ◽

10.5194/angeo-21-1931-2003 ◽

2003 ◽

Vol 21 (9) ◽

pp. 1931-1938 ◽

Cited By ~ 3

Author(s):

B. V. Kozelov ◽

T. V. Kozelova

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Cellular Automata ◽

Interplanetary Magnetic Field ◽

Control Parameter ◽

Energy Content ◽

Nonlinear Phenomena ◽

Cellular Automata Model ◽

The Earth ◽

Magnetospheric Tail

Abstract. We propose a cellular automata model (CAM) to describe the substorm activity of the magnetospheric-ionospheric system. The state of each cell in the model is described by two numbers that correspond to the energy content in a region of the current sheet in the magnetospheric tail and to the conductivity of the ionospheric domain that is magnetically connected with this region. The driving force of the system is supposed to be provided by the solar wind that is convected along the two boundaries of the system. The energy flux inside is ensured by the penetration of the energy from the solar wind into the array of cells (magnetospheric tail) with a finite velocity. The third boundary (near to the Earth) is closed and the fourth boundary is opened, thereby modeling the flux far away from the tail. The energy dissipation in the system is quite similar to other CAM models, when the energy in a particular cell exceeds some pre-defined threshold, and the part of the energy excess is redistributed between the neighbouring cells. The second number attributed to each cell mimics ionospheric conductivity that can allow for a part of the energy to be shed on field-aligned currents. The feedback between "ionosphere" and "magnetospheric tail" is provided by the change in a part of the energy, which is redistributed in the tail when the threshold is surpassed. The control parameter of the model is the z-component of the interplanetary magnetic field (Bz IMF), "frozen" into the solar wind. To study the internal dynamics of the system at the beginning, this control parameter is taken to be constant. The dynamics of the system undergoes several bifurcations, when the constant varies from - 0.6 to - 6.0. The Bz IMF input results in the periodic transients (activation regions) and the inter-transient period decreases with the decrease of Bz. At the same time the onset of activations in the array shifts towards the "Earth". When the modulus of the Bz IMF exceeds some threshold value, the transition takes place from periodic to chaotic dynamics. In the second part of the work we have chosen as the source the real values of the z-component of the interplanetary magnetic field taken from satellite observations. We have shown that in this case the statistical properties of the transients reproduce the characteristic features observed by Lui et al. (2000).Key words. Magnetospheric physics (magnetosphere-ionosphere interactions) – Space plasma physics (nonlinear phenomena)

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Long-Term Variability of the Polytropic Index of Solar Wind Protons at 1 AU

Solar Physics ◽

10.1007/s11207-013-0401-x ◽

2013 ◽

Vol 289 (4) ◽

pp. 1371-1378 ◽

Cited By ~ 38

Author(s):

G. Nicolaou ◽

G. Livadiotis ◽

X. Moussas

Keyword(s):

Solar Wind ◽

Polytropic Index

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3D MHD study of the Earth magnetosphere response during extreme space weather conditions

10.5194/egusphere-egu21-1684 ◽

2021 ◽

Author(s):

Jacobo Varela Rodriguez ◽

Sacha A. Brun ◽

Antoine Strugarek ◽

Victor Réville ◽

Filippo Pantellini ◽

...

Keyword(s):

Solar Wind ◽

Space Weather ◽

Coronal Mass Ejections ◽

Main Sequence ◽

Dynamic Pressure ◽

Weather Conditions ◽

The Sun ◽

Earth Surface ◽

The Earth ◽

The Imf

The aim of the study is to analyze the response of the Earth magnetosphere for various space weather conditions and model the effect of interplanetary coronal mass ejections. The magnetopause stand off distance, open-closed field lines boundary and plasma flows towards the planet surface are investigated. We use the MHD code PLUTO in spherical coordinates to perform a parametric study regarding the dynamic pressure and temperature of the solar wind as well as the interplanetary magnetic field intensity and orientation. The range of the parameters analyzed extends from regular to extreme space weather conditions consistent with coronal mass ejections at the Earth orbit. The direct precipitation of the solar wind on the Earth day side at equatorial latitudes is extremely unlikely even during super coronal mass ejections. For example, the SW precipitation towards the Earth surface for a IMF purely oriented in the Southward direction requires a IMF intensity around 1000 nT and the SW dynamic pressure above 350 nPa, space weather conditions well above super-ICMEs. The analysis is extended to previous stages of the solar evolution considering the rotation tracks from Carolan (2019). The simulations performed indicate an efficient shielding of the Earth surface 1100 Myr after the Sun enters in the main sequence. On the other hand, for early evolution phases along the Sun main sequence once the Sun rotation rate was at least 5 times faster (< 440 Myr), the Earth surface was directly exposed to the solar wind during coronal mass ejections (assuming today&#180;s Earth magnetic field). Regarding the satellites orbiting the Earth, Southward and Ecliptic IMF orientations are particularly adverse for Geosynchronous satellites, partially exposed to the SW if the SW dynamic pressure is 8-14 nPa and the IMF intensity 10 nT. On the other hand, Medium orbit satellites at 20000 km are directly exposed to the SW during Common ICME if the IMF orientation is Southward and during Strong ICME if the IMF orientation is Earth-Sun or Ecliptic. The same way, Medium orbit satellites at 10000 km are directly exposed to the SW if a Super ICME with Southward IMF orientation impacts the Earth.This work was supported by the project 2019-T1/AMB-13648 founded by the Comunidad de Madrid, grants ERC WholeSun, Exoplanets A and PNP. We extend our thanks to CNES for Solar Orbiter, PLATO and Meteo Space science support and to INSU/PNST for their financial support.

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Water on the Moon

Proceedings of the International Astronomical Union ◽

10.1017/s1743921316005652 ◽

2015 ◽

Vol 11 (A29B) ◽

pp. 402-406 ◽

Cited By ~ 1

Author(s):

Yvonne J. Pendleton

Keyword(s):

Solar Wind ◽

Thermal Cycling ◽

Volcanic Glass ◽

Glass Beads ◽

The Moon ◽

Modern Equipment ◽

Know How ◽

The Earth ◽

The World

AbstractAfter years of thinking the Moon is dry, we now know there are three manifestations in which water appears on the Moon today: 1) Previously hypothesized buried deposits of volatiles at the lunar poles were found at Cabeus crater. There are questions about the origin of such volatiles (i.e., in-falling comets & meteorites, migration of recently formed surficial OH/H2O, and accumulated release from the interior), but there is no doubt the water is there. 2) Widespread, thinly-distributed, surficial OH (or H2O) has been clearly detected across all types of lunar terrain. The consensus is that the OH is derived from solar wind, but we do not know how quickly it forms, nor how mobile it is. 3) The amount of water present soon after the Moon formed is now documented in new analyses of lunar materials in volcanic glass beads, apatites and plagioclase feldspars. Apollo era sample analyses were not precise enough to distinguish between indigenous lunar water and terrestrial contamination. Measurements with modern equipment are more precise (both elemental and isotopic), and can better constrain a host of processes (e.g. diffusion, thermal cycling). Scientists around the world are studying lunar water. Ongoing analyses are informing a number of hypotheses and theories about the connection between the Earth and its wet Moon.

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The mechanical advantage of the magnetosphere: solar-wind-related forces in the magnetosphere-ionosphere-Earth system

Annales Geophysicae ◽

10.5194/angeo-25-255-2007 ◽

2007 ◽

Vol 25 (1) ◽

pp. 255-269 ◽

Cited By ~ 18

Author(s):

V. M. Vasyliūnas

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Lorentz Force ◽

Linear Momentum ◽

Neutral Atmosphere ◽

Earth System ◽

Mechanical Advantage ◽

The Earth ◽

Earth’S Interior ◽

Earth's Interior

Abstract. Magnetosphere-ionosphere interactions involve electric currents that circulate between the two regions; the associated Lorentz forces, existing in both regions as matched opposite pairs, are generally viewed as the primary mechanism by which linear momentum, derived ultimately from solar wind flow, is transferred from the magnetosphere to the ionosphere, where it is further transferred by collisions to the neutral atmosphere. For a given total amount of current, however, the total force is proportional to ℒB and in general, since ℒ2B~ constant by flux conservation, is much larger in the ionosphere than in the magnetosphere (ℒ = effective length, B = magnetic field). The magnetosphere may be described as possesing a mechanical advantage: the Lorentz force in it is coupled with a Lorentz force in the ionosphere that has been amplified by a factor given approximately by the square root of magnetic field magnitude ratio (~20 to 40 on field lines connected to the outer magnetosphere). The linear momentum transferred to the ionosphere (and thence to the atmosphere) as the result of magnetic stresses applied by the magnetosphere can thus be much larger than the momentum supplied by the solar wind through tangential stress. The added linear momentum comes from within the Earth, extracted by the Lorentz force on currents that arise as a consequence of magnetic perturbation fields from the ionosphere (specifically, the shielding currents within the Earth that keep out the time-varying external fields). This implies at once that Fukushima's theorem on the vanishing of ground-level magnetic perturbations cannot be fully applicable, a conclusion confirmed by re-examining the assumptions from which the theorem is derived. To balance the inferred Lorentz force within the Earth's interior, there must exist an antisunward mechanical stress there, only a small part of which is the acceleration of the entire Earth system by the net force exerted on it by the solar wind. The solar-wind interaction can thus give rise to internal forces, significantly larger than the force exerted by the solar wind itself, between the ionosphere and the neutral atmosphere as well as within the current-carrying regions of the Earth's interior.

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A global study of hot flow anomalies using Cluster multi-spacecraft measurements

Annales Geophysicae ◽

10.5194/angeo-27-2057-2009 ◽

2009 ◽

Vol 27 (5) ◽

pp. 2057-2076 ◽

Cited By ~ 30

Author(s):

G. Facskó ◽

Z. Németh ◽

G. Erdős ◽

A. Kis ◽

I. Dandouras

Keyword(s):

Solar Wind ◽

Particle Density ◽

Solar Wind Speed ◽

Solar Wind Plasma ◽

Separation Distance ◽

Magnetic Shear ◽

The Earth ◽

Global Study ◽

Time Periods ◽

Tangential Discontinuities

Abstract. Hot flow anomalies (HFAs) are studied using observations of the magnetometer and the plasma instrument aboard the four Cluster spacecraft. We study several specific features of tangential discontinuities on the basis of Cluster measurements from the time periods of February–April 2003, December 2005–April 2006 and January–April 2007, when the separation distance of spacecraft was large. The previously discovered condition (Facskó et al., 2008) for forming HFAs is confirmed, i.e. that the solar wind speed and fast magnetosonic Mach number values are higher than average. Furthermore, this constraint is independent of the Schwartz et al. (2000)’s condition for HFA formation. The existence of this new condition is confirmed by simultaneous ACE magnetic field and solar wind plasma observations at the L1 point, at 1.4 million km distance from the Earth. The temperature, particle density and pressure parameters observed at the time of HFA formation are also studied and compared to average values of the solar wind plasma. The size of the region affected by the HFA was estimated by using two different methods. We found that the size is mainly influenced by the magnetic shear and the angle between the discontinuity normal and the Sun-Earth direction. The size grows with the shear and (up to a certain point) with the angle as well. After that point it starts decreasing. The results are compared with the outcome of recent hybrid simulations.

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