scholarly journals The role of turbulence in coronal heating and solar wind expansion

2015 ◽  
Vol 373 (2041) ◽  
pp. 20140148 ◽  
Author(s):  
Steven R. Cranmer ◽  
Mahboubeh Asgari-Targhi ◽  
Mari Paz Miralles ◽  
John C. Raymond ◽  
Leonard Strachan ◽  
...  
Keyword(s):  
Solar Wind ◽  
Magnetic Reconnection ◽  
Solar Surface ◽  
Ultraviolet Spectroscopy ◽  
Magnetohydrodynamic Turbulence ◽  
Turbulent Fluctuations ◽  
Multi Scale ◽  
Outer Corona ◽  
Hot Corona

Plasma in the Sun's hot corona expands into the heliosphere as a supersonic and highly magnetized solar wind. This paper provides an overview of our current understanding of how the corona is heated and how the solar wind is accelerated. Recent models of magnetohydrodynamic turbulence have progressed to the point of successfully predicting many observed properties of this complex, multi-scale system. However, it is not clear whether the heating in open-field regions comes mainly from the dissipation of turbulent fluctuations that are launched from the solar surface, or whether the chaotic ‘magnetic carpet’ in the low corona energizes the system via magnetic reconnection. To help pin down the physics, we also review some key observational results from ultraviolet spectroscopy of the collisionless outer corona.

A two-step role for plasma expansion in solar wind heat flux regulation

2021 ◽  
Author(s):  
Maria Elena Innocenti ◽  
Elisabetta Boella ◽  
Anna Tenerani ◽  
Marco Velli
Keyword(s):  
Heat Flux ◽  
Solar Wind ◽  
Large Scale ◽  
Box Model ◽  
Plasma Expansion ◽  
Multi Scale ◽  
Simulation Techniques ◽  
Connecting The Dots ◽  
Kinetic Instabilities

<p>Already several decades ago, it was suggested that kinetic instabilities play a fundamental role in heat flux regulation at relatively large distances from the Sun, R> 1 AU [Scime et al, 1994]. Now, Parker Solar Probe observations have established that this is the case also closer to it [Halekas et al, 2020].</p><p>Electron scale instabilities in the solar wind are driven and affected in their evolution by the slow, large scale process of solar wind expansion, as demonstrated observationally [Stverak et al, 2008; Bercic et al, 2020], and via fully kinetic Expanding Box Model simulations [Innocenti et al, 2019b].</p><p>Now, connecting the dots, we examine an indirect role of plasma expansion in heat flux regulation in the solar wind. We show, as a proof of principle, that plasma expansion can modify heat flux evolution as a function of heliocentric distance, with respect to what is expected within an adiabatic framework, due to the onset of kinetic instabilities, in this case, an oblique firehose instability developing self consistently in the presence of a core and suprathermal electron population [Innocenti et al, 2020].</p><p>This result highlights, once again, the deeply multi scale nature of the heliospheric environment, that calls for advanced simulation techniques. In this work, the simulations are done with the fully kinetic, semi-implicit [Markidis et al, 2010], Expanding Box Model [Velli et al, 1992] code EB-iPic3D [Innocenti et al, 2019a].</p>

scholarly journals The role of magnetic handedness in magnetic cloud propagation

2010 ◽  
Vol 28 (5) ◽  
pp. 1075-1100 ◽  
Author(s):  
U. Taubenschuss ◽  
N. V. Erkaev ◽  
H. K. Biernat ◽  
C. J. Farrugia ◽  
C. Möstl ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Magnetic Reconnection ◽  
Interplanetary Magnetic Field ◽  
Equatorial Plane ◽  
Magnetic Clouds ◽  
Geometrical Parameters ◽  
Meridional Plane ◽  
Mhd Simulations

Abstract. We investigate the propagation of magnetic clouds (MCs) through the inner heliosphere using 2.5-D ideal magnetohydrodynamic (MHD) simulations. A numerical solution is obtained on a spherical grid, either in a meridional plane or in an equatorial plane, by using a Roe-type approximate Riemann solver in the frame of a finite volume approach. The structured background solar wind is simulated for a solar activity minimum phase. In the frame of MC propagation, special emphasis is placed on the role of the initial magnetic handedness of the MC's force-free magnetic field because this parameter strongly influences the efficiency of magnetic reconnection between the MC's magnetic field and the interplanetary magnetic field. Magnetic clouds with an axis oriented perpendicular to the equatorial plane develop into an elliptic shape, and the ellipse drifts into azimuthal direction. A new feature seen in our simulations is an additional tilt of the ellipse with respect to the direction of propagation as a direct consequence of magnetic reconnection. During propagation in a meridional plane, the initial circular cross section develops a concave-outward shape. Depending on the initial handedness, the cloud's magnetic field may reconnect along its backside flanks to the ambient interplanetary magnetic field (IMF), thereby losing magnetic flux to the IMF. Such a process in combination with a structured ambient solar wind has never been analyzed in detail before. Furthermore, we address the topics of force-free magnetic field conservation and the development of equatorward flows ahead of a concave-outward shaped MC. Detailed profiles are presented for the radial evolution of magnetoplasma and geometrical parameters. The principal features seen in our MHD simulations are in good agreement with in-situ measurements performed by spacecraft. The 2.5-D studies presented here may serve as a basis under more simple geometrical conditions to understand more complicated effects seen in 3-D simulations.

Identifying and Quantifying the Role of Magnetic Reconnection in Space Plasma Turbulence

2020 ◽  
Author(s):  
Jeffersson Andres Agudelo Rueda ◽  
Daniel Verscharen ◽  
Robert Wicks ◽  
Christopher Owen ◽  
Georgios Nicolaou ◽  
...  
Keyword(s):  
Solar Wind ◽  
Magnetic Reconnection ◽  
Space Plasma ◽  
Plasma Turbulence ◽  
Close Link ◽  
Particle In Cell ◽  
Open Questions ◽  
Strong Current ◽  
Characteristic Features

<p>One of the outstanding open questions in space plasma physics is the heating problem in the solar corona and the solar wind. In-situ measurements, as well as MHD and kinetic simulations, suggest a relation between the turbulent nature of plasma and the onset of magnetic reconnection as a channel of energy dissipation, particle acceleration and a heating mechanism. It has also been proven that non-linear interactions between counter propagating Alfvén waves drives plasma towards a turbulent state. On the other hand, the interactions between particles and waves becomes stronger at scales near the ion(electron) gyroradious ρi (ρe ), and so turbulence can enhance conditions for reconnection and increase the number of reconnection sites. Therefore, there is a close link between turbulence and reconnection. We use fully kinetic particle in cell (PIC) simulations, able to resolve the kinetic phenomena, to study the onset of reconnection in a 3D simulation box with parameters similar to the solar wind under Alfvénic turbulence. We identify in our simulations characteristic features of reconnection sites as steep gradients of the magnetic field strength alongside with the formation of strong current sheets and inflow-outflow patterns of plasma particles near the diffusion regions. These results will be used to quantify the role reconnection in plasma turbulence.</p>

scholarly journals Spectral scaling in the turbulent Earth's plasma sheet revisited

2007 ◽  
Vol 14 (4) ◽  
pp. 535-541 ◽  
Author(s):  
Z. Vörös ◽  
W. Baumjohann ◽  
R. Nakamura ◽  
A. Runov ◽  
M. Volwerk ◽  
...  
Keyword(s):  
Magnetic Reconnection ◽  
Plasma Sheet ◽  
Large Scale ◽  
Spatial Scales ◽  
Inertial Range ◽  
Bulk Flow ◽  
Magnetic Fluctuations ◽  
Magnetohydrodynamic Turbulence ◽  
Multi Scale ◽  
Bursty Bulk Flow

Abstract. Bursty bulk flow associated magnetic fluctuations exhibit at least three spectral scaling ranges in the Earth's plasma sheet. Two of the three scaling ranges can be associated with multi-scale magnetohydrodynamic turbulence between the spatial scales from ~100 km to several RE (RE is the Earth's radius). These scales include the inertial range and below ~0.5 RE a steepened scaling range, theoretically not fully understood yet. It is shown that, in the near-Earth plasma sheet, the inertial range can be robustly identified only if multi-scale quasi stationary (MSQS) data intervals are selected. Multiple bursty flow associated magnetic fluctuations, however, exhibit 1/f type scaling indicating that large-scale fluctuations are controlled by multiple uncorrelated driving sources of the bulk flows (e.g. magnetic reconnection, instabilities).

scholarly journals The multi-scale nature of the solar wind

2019 ◽  
Vol 16 (1) ◽  
Author(s):  
Daniel Verscharen ◽  
Kristopher G. Klein ◽  
Bennett A. Maruca
Keyword(s):  
Solar Wind ◽  
Distribution Functions ◽  
Magnetized Plasma ◽  
Global Dynamics ◽  
Spatial And Temporal Scales ◽  
Multi Scale ◽  
Expansion Time ◽  
Collective Plasma

AbstractThe solar wind is a magnetized plasma and as such exhibits collective plasma behavior associated with its characteristic spatial and temporal scales. The characteristic length scales include the size of the heliosphere, the collisional mean free paths of all species, their inertial lengths, their gyration radii, and their Debye lengths. The characteristic timescales include the expansion time, the collision times, and the periods associated with gyration, waves, and oscillations. We review the past and present research into the multi-scale nature of the solar wind based on in-situ spacecraft measurements and plasma theory. We emphasize that couplings of processes across scales are important for the global dynamics and thermodynamics of the solar wind. We describe methods to measure in-situ properties of particles and fields. We then discuss the role of expansion effects, non-equilibrium distribution functions, collisions, waves, turbulence, and kinetic microinstabilities for the multi-scale plasma evolution.

scholarly journals A High-Resolution View of the Solar Chromosphere and Corona

1980 ◽  
Vol 5 ◽  
pp. 557-569 ◽  
Author(s):  
G. E. Brueckner
Keyword(s):  
Solar Wind ◽  
Heat Conduction ◽  
High Speed ◽  
Interplanetary Medium ◽  
Dominant Role ◽  
Coronal Holes ◽  
Solar Chromosphere ◽  
Coronal Density ◽  
Hot Corona

Skylab has demonstrated the dominant role of magnetic fields in the solar atmosphere. The solar wind is not a necessary consequence of the pressure imbalance between the hot corona and the interplanetary medium. High speed solar windstreams are originating in coronal holes where coronal density and temperature are less than in the quiet sun. Older models of the solar wind invoke heat conduction from the hot corona as the prime energy source for the solar wind. However in coronal holes the energy supplied by heat conduction is less than in the ordinary sun while the high speed windstreams require an amount of energy which cannot be supplied by conduction alone.

The Role of Magnetic Reconnection–associated Processes in Local Particle Acceleration in the Solar Wind

2019 ◽  
Vol 873 (1) ◽  
pp. 72 ◽  
Author(s):  
L. Adhikari ◽  
O. Khabarova ◽  
G. P. Zank ◽  
L.-L. Zhao
Keyword(s):  
Solar Wind ◽  
Particle Acceleration ◽  
Magnetic Reconnection

Alpha-Effect, Current and Kinetic Helicities for Magnetically Driven Turbulence, and Solar Dynamo

2000 ◽  
Vol 179 ◽  
pp. 387-388
Author(s):  
Gaetano Belvedere ◽  
V. V. Pipin ◽  
G. Rüdiger
Keyword(s):  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Convection Zone ◽  
Solar Surface ◽  
Momentum Transport ◽  
Angular Momentum Transport ◽  
Magnetic Buoyancy ◽  
Alpha Effect ◽  
Current Helicity

Extended AbstractRecent numerical simulations lead to the result that turbulence is much more magnetically driven than believed. In particular the role ofmagnetic buoyancyappears quite important for the generation ofα-effect and angular momentum transport (Brandenburg & Schmitt 1998). We present results obtained for a turbulence field driven by a (given) Lorentz force in a non-stratified but rotating convection zone. The main result confirms the numerical findings of Brandenburg & Schmitt that in the northern hemisphere theα-effect and the kinetic helicityℋkin= 〈u′ · rotu′〉 are positive (and negative in the northern hemisphere), this being just opposite to what occurs for the current helicityℋcurr= 〈j′ ·B′〉, which is negative in the northern hemisphere (and positive in the southern hemisphere). There has been an increasing number of papers presenting observations of current helicity at the solar surface, all showing that it isnegativein the northern hemisphere and positive in the southern hemisphere (see Rüdigeret al. 2000, also for a review).

scholarly journals The Location of Magnetic Reconnection at Earth’s Magnetopause

2021 ◽  
Vol 217 (3) ◽  
Author(s):  
K. J. Trattner ◽  
S. M. Petrinec ◽  
S. A. Fuselier
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Magnetic Reconnection ◽  
Ion Beams ◽  
Review Article ◽  
Observational Evidence ◽  
Magnetic Shear ◽  
General Direction ◽  
Shear Model ◽  
Wide Range

AbstractOne of the major questions about magnetic reconnection is how specific solar wind and interplanetary magnetic field conditions influence where reconnection occurs at the Earth’s magnetopause. There are two reconnection scenarios discussed in the literature: a) anti-parallel reconnection and b) component reconnection. Early spacecraft observations were limited to the detection of accelerated ion beams in the magnetopause boundary layer to determine the general direction of the reconnection X-line location with respect to the spacecraft. An improved view of the reconnection location at the magnetopause evolved from ionospheric emissions observed by polar-orbiting imagers. These observations and the observations of accelerated ion beams revealed that both scenarios occur at the magnetopause. Improved methodology using the time-of-flight effect of precipitating ions in the cusp regions and the cutoff velocity of the precipitating and mirroring ion populations was used to pinpoint magnetopause reconnection locations for a wide range of solar wind conditions. The results from these methodologies have been used to construct an empirical reconnection X-line model known as the Maximum Magnetic Shear model. Since this model’s inception, several tests have confirmed its validity and have resulted in modifications to the model for certain solar wind conditions. This review article summarizes the observational evidence for the location of magnetic reconnection at the Earth’s magnetopause, emphasizing the properties and efficacy of the Maximum Magnetic Shear Model.

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