scholarly journals Blob formation and acceleration in the solar wind: role of converging flows and viscosity

2008 ◽  
Vol 26 (10) ◽  
pp. 3049-3060 ◽  
Author(s):  
G. Lapenta ◽  
A. L. Restante
Keyword(s):  
Solar Wind ◽  
Electric Field ◽  
Slow Solar Wind ◽  
Viscous Drag ◽  
Fast Solar Wind ◽  
Momentum Exchange ◽  
Tearing Instability ◽  
Fluid Layers ◽  
Two Sides

Abstract. The effect of viscosity and of converging flows on the formation of blobs in the slow solar wind is analysed by means of resistive MHD simulations. The regions above coronal streamers where blobs are formed (Sheeley et al., 1997) are simulated using a model previously proposed by Einaudi et al. (1999). The result of our investigation is two-fold. First, we demonstrate a new mechanism for enhanced momentum transfer between a forming blob and the fast solar wind surrounding it. The effect is caused by the longer range of the electric field caused by the tearing instability forming the blob. The electric field reaches into the fast solar wind and interacts with it, causing a viscous drag that is global in nature rather than local across fluid layers as it is the case in normal uncharged fluids (like water). Second, the presence of a magnetic cusp at the tip of a coronal helmet streamer causes a converging of the flows on the two sides of the streamer and a direct push of the forming island by the fast solar wind, resulting in a more efficient momentum exchange.

scholarly journals Tearing Instability and Periodic Density Perturbations in the Slow Solar Wind

2020 ◽  
Vol 895 (1) ◽  
pp. L20 ◽  
Author(s):  
Victor Réville ◽  
Marco Velli ◽  
Alexis P. Rouillard ◽  
Benoit Lavraud ◽  
Anna Tenerani ◽  
...  
Keyword(s):  
Solar Wind ◽  
Slow Solar Wind ◽  
Tearing Instability ◽  
Density Perturbations

scholarly journals Solar wind dependence of ion parameters in the Earth's magnetospheric region calculated from CLUSTER observations

2008 ◽  
Vol 26 (3) ◽  
pp. 387-394 ◽  
Author(s):  
M. H. Denton ◽  
M. G. G. T. Taylor
Keyword(s):  
Solar Wind ◽  
Plasma Sheet ◽  
Slow Solar Wind ◽  
Ion Temperature ◽  
Fast Solar Wind ◽  
Science Data ◽  
Ion Distributions ◽  
Modelling Studies ◽  
Cluster Ion ◽  
Using Data

Abstract. Moments calculated from the ion distributions (~0–40 keV) measured by the Cluster Ion Spectrometry (CIS) instrument are combined with data from the Cluster Flux Gate Magnetometer (FGM) instrument and used to characterise the bulk properties of the plasma in the near-Earth magnetosphere over five years (2001–2005). Results are presented in the form of 2-D xy, xz and yz GSM cuts through the magnetosphere using data obtained from the Cluster Science Data System (CSDS) and the Cluster Active Archive (CAA). Analysis reveals the distribution of ~0–40 keV ions in the inner magnetosphere is highly ordered and highly responsive to changes in solar wind velocity. Specifically, elevations in temperature are found to occur across the entire nightside plasma sheet region during times of fast solar wind. We demonstrate that the nightside plasma sheet ion temperature at a downtail distance of ~12 to 19 Earth radii increases by a factor of ~2 during periods of fast solar wind (500–1000 km s−1) compared to periods of slow solar wind (100–400 km s−1). The spatial extent of these increases are shown in the xy, xz and yz GSM planes. The results from the study have implications for modelling studies and simulations of solar-wind/magnetosphere coupling, which ultimately rely on in situ observations of the plasma sheet properties for input/boundary conditions.

scholarly journals On Yaglom’s Law for the Interplanetary Proton Density and Temperature Fluctuations in Solar Wind Turbulence

Entropy ◽  
2020 ◽  
Vol 22 (12) ◽  
pp. 1419
Author(s):  
Giuseppe Consolini ◽  
Tommaso Alberti ◽  
Vincenzo Carbone
Keyword(s):  
Solar Wind ◽  
Structure Function ◽  
Interplanetary Space ◽  
Slow Solar Wind ◽  
Order Structure ◽  
Proton Density ◽  
Linear Scaling ◽  
Fast Solar Wind ◽  
Third Order ◽  
Passive Scalars

In the past decades, there has been an increasing literature on the presence of an inertial energy cascade in interplanetary space plasma, being interpreted as the signature of Magnetohydrodynamic turbulence (MHD) for both fields and passive scalars. Here, we investigate the passive scalar nature of the solar wind proton density and temperature by looking for scaling features in the mixed-scalar third-order structure functions using measurements on-board the Ulysses spacecraft during two different periods, i.e., an equatorial slow solar wind and a high-latitude fast solar wind, respectively. We find a linear scaling of the mixed third-order structure function as predicted by Yaglom’s law for passive scalars in the case of slow solar wind, while the results for fast solar wind suggest that the mixed fourth-order structure function displays a linear scaling. A simple empirical explanation of the observed difference is proposed and discussed.

scholarly journals The origin of slow Alfvénic solar wind at solar minimum

2019 ◽  
Vol 492 (1) ◽  
pp. 39-44 ◽  
Author(s):  
D Stansby ◽  
L Matteini ◽  
T S Horbury ◽  
D Perrone ◽  
R D’Amicis ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Alpha Particle ◽  
Coronal Holes ◽  
Slow Solar Wind ◽  
Kinetic Properties ◽  
Fast Solar Wind ◽  
Lower Corona ◽  
Field Lines ◽  
Slow Wind

ABSTRACT Although the origins of slow solar wind are unclear, there is increasing evidence that at least some of it is released in a steady state on overexpanded coronal hole magnetic field lines. This type of slow wind has similar properties to the fast solar wind, including strongly Alfvénic fluctuations. In this study, a combination of proton, alpha particle, and electron measurements are used to investigate the kinetic properties of a single interval of slow Alfvénic wind at 0.35 au. It is shown that this slow Alfvénic interval is characterized by high alpha particle abundances, pronounced alpha–proton differential streaming, strong proton beams, and large alpha-to-proton temperature ratios. These are all features observed consistently in the fast solar wind, adding evidence that at least some Alfvénic slow solar wind also originates in coronal holes. Observed differences between speed, mass flux, and electron temperature between slow Alfvénic and fast winds are explained by differing magnetic field geometry in the lower corona.

scholarly journals Scaling Laws of Turbulence and Heating of Fast Solar Wind: The Role of Density Fluctuations

2009 ◽  
Vol 103 (6) ◽  
Author(s):  
V. Carbone ◽  
R. Marino ◽  
L. Sorriso-Valvo ◽  
A. Noullez ◽  
R. Bruno
Keyword(s):  
Solar Wind ◽  
Scaling Laws ◽  
Density Fluctuations ◽  
Fast Solar Wind

On the direction of the velocity and magnetic field fluctuations in undisturbed solar wind

2021 ◽  
Vol 30 (1) ◽  
pp. 184-190
Author(s):  
Dmitry V. Erofeev
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Solar Activity ◽  
Alfven Waves ◽  
High Solar Activity ◽  
Slow Solar Wind ◽  
Alfvén Waves ◽  
Velocity Fluctuations ◽  
Field Fluctuations

Abstract Measurements of velocity and magnetic field in near-Earth heliosphere is analized in order to investigate systematical deflection from transversality of the velocity and magnetic field fluctuations in undisturbed solar wind. Fluctuations occurred in the meridional plain of heliosphere (RN plain of the RTN reference system) are transversal with respect to mean magnetic field during periods of high solar activity, but they become non-transversal close to solar cycle minima. This phenomenon is investigated focusing on a role of Alfvén waves. It is shown that deflections from transversality is mostly expressed by fluctuations in slow solar wind streams with low contribution of Alfvén waves, whereas strongly Alfvénic turbulence undergo such deflection in a less degree. In addition, we consider orientation of velocity fluctuations in the azimuthal (RT) plain of heliosphere, which also indicates some interesting features.

scholarly journals Conditions for the existence of Kelvin-Helmholtz instability in a CME

2015 ◽  
Vol 11 (S320) ◽  
pp. 218-220
Author(s):  
Andrés Páez ◽  
Vera Jatenco-Pereira ◽  
Diego Falceta-Gonçcalves ◽  
Merav Opher
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Field Intensity ◽  
Magnetic Field Intensity ◽  
Slow Solar Wind ◽  
Fast Solar Wind ◽  
Helmholtz Instability ◽  
Initiation Phase ◽  
Local Properties ◽  
Zone Ii

AbstractThe presence of Kelvin-Helmholtz instability (KHI) in the sheaths of Coronal Mass Ejections (CMEs) has been proposed and observed by several authors in the literature. In the present work, we assume their existence and propose a method to constrain the local properties, like the CME magnetic field intensity for the development of KHI. We study a CME in the initiation phase interacting with the slow solar wind (Zone I) and with the fast solar wind (Zone II). Based on the theory of magnetic KHI proposed by Chandrasekhar (1961) we found the radial heliocentric interval for the KHI existence, in particular we constrain it with the CME magnetic field intensity. We conclude that KHI may exist in both CME Zones but it is perceived that Zone I is more appropriated for the KHI formation.

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