scholarly journals Cluster observations of the high-latitude magnetopause and cusp: initial results from the CIS ion instruments

2001 ◽  
Vol 19 (10/12) ◽  
pp. 1545-1566 ◽  
Author(s):  
J. M. Bosqued ◽  
T. D. Phan ◽  
I. Dandouras ◽  
C. P. Escoubet ◽  
H. Rème ◽  
...  
Keyword(s):  
Magnetic Reconnection ◽  
Boundary Layers ◽  
High Latitude ◽  
Three Dimensional ◽  
Distribution Functions ◽  
Current Layer ◽  
Transfer Event ◽  
Normal Speed ◽  
Field Lines ◽  
The Imf

Abstract. Launched on an elliptical high inclination orbit (apogee: 19.6 RE) since January 2001 the Cluster satellites have been conducting the first detailed three-dimensional studies of the high-latitude dayside magnetosphere, including the exterior cusp, neighbouring boundary layers and magnetopause regions. Cluster satellites carry the CIS ion spectrometers that provide high-precision, 3D distributions of low-energy (<35 keV/e) ions every 4 s. This paper presents the first two observations of the cusp and/or magnetopause behaviour made under different interplanetary magnetic field (IMF) conditions. Flow directions, 3D distribution functions, density profiles and ion composition profiles are analyzed to demonstrate the high variability of high-latitude regions. In the first crossing analyzed (26 January 2001, dusk side, IMF-BZ < 0), multiple, isolated boundary layer, magnetopause and magnetosheath encounters clearly occurred on a quasi-steady basis for ~ 2 hours. CIS ion instruments show systematic accelerated flows in the current layer and adjacent boundary layers on the Earthward side of the magnetopause. Multi-point analysis of the magnetopause, combining magnetic and plasma data from the four Cluster spacecraft, demonstrates that oscillatory outward-inward motions occur with a normal speed of the order of ± 40 km/s; the thickness of the high-latitude current layer is evaluated to be of the order of 900–1000 km. Alfvénic accelerated flows and D-shaped distributions are convincing signatures of a magnetic reconnection occurring equatorward of the Cluster satellites. Moreover, the internal magnetic and plasma structure of a flux transfer event (FTE) is analyzed in detail; its size along the magnetopause surface is ~ 12 000 km and it convects with a velocity of ~ 200 km/s. The second event analyzed (2 February 2001) corresponds to the first Cluster pass within the cusp when the IMF-BZ component was northward directed. The analysis of relevant CIS plasma data shows temporal cusp structures displaying a reverse energy-latitude "saw tooth" dispersion, typical for a bursty reconnection between the IMF and the lobe field lines. The observation of D-shaped distributions indicates that the Cluster satellites were located just a few RE from the reconnection site.Key words. Magnetospheric physics (magnetopause, cusp, and boundary layers; magnetosheath) Space plasma physics (magnetic reconnection)

Origins and Evolution of the Electron and Ion Populations of the Magnetopause’s Boundary Layers

2020 ◽  
Author(s):  
Jean Berchem ◽  
Giovanni Lapenta ◽  
Robert Richard ◽  
William Paterson ◽  
C. Philippe Escoubet
Keyword(s):  
Boundary Layers ◽  
Three Dimensional ◽  
Distribution Functions ◽  
Current Layer ◽  
Filamentary Structure ◽  
Particle In Cell ◽  
Reconnection Region ◽  
Dayside Magnetopause ◽  
Velocity Distribution Functions ◽  
Multiscale Structures

&lt;p&gt;Increasingly sophisticated instruments and simulations have revealed a wide variety of plasma processes and multiscale structures at the dayside magnetopause. In this presentation, we focus on the origins and evolution of the plasma populations observed in the magnetopause boundary layers. We present the results of Particle-In-Cell (PIC) simulations encompassing large volumes of the dayside magnetosphere. The implicit 3D PIC code used in the study was initialized from a global MHD state of the magnetosphere for southward interplanetary field conditions. &amp;#160;Three-dimensional plots of the perpendicular slippage indicates that reconnection occurs over most of the dayside magnetopause. However, the simulation reveals that the reconnection region has a much more filamentary structure than the X-line expected from the extrapolation of 2D models and that multiscale structures thread the reconnection outflow. In particular, the simulation indicates the formation of multiple layers of electrons with significant field-aligned velocities along the main magnetopause current layer. We use velocity distribution functions at different locations in the reconnection outflow to characterize the origins and evolution of the electron and ionpopulations of the magnetosheath and magnetospheric boundary layers and compare them with observations from the MMS and Cluster spacecraft.&lt;/p&gt;

scholarly journals 2D and 3D turbulent magnetic reconnection

2009 ◽  
Vol 5 (H15) ◽  
pp. 434-435
Author(s):  
A. Lazarian ◽  
G. Kowal ◽  
E. Vishniac ◽  
K. Kulpa-Dubel ◽  
K. Otmianowska-Mazur
Keyword(s):  
Magnetic Field ◽  
Magnetic Reconnection ◽  
Large Scale ◽  
Gamma Ray ◽  
Three Dimensional ◽  
Turnover Time ◽  
Turbulent Fluid ◽  
Astrophysical Objects ◽  
Field Lines ◽  
The Magnetic Field

AbstractA magnetic field embedded in a perfectly conducting fluid preserves its topology for all times. Although ionized astrophysical objects, like stars and galactic disks, are almost perfectly conducting, they show indications of changes in topology, magnetic reconnection, on dynamical time scales. Reconnection can be observed directly in the solar corona, but can also be inferred from the existence of large scale dynamo activity inside stellar interiors. Solar flares and gamma ray busts are usually associated with magnetic reconnection. Previous work has concentrated on showing how reconnection can be rapid in plasmas with very small collision rates. Here we present numerical evidence, based on three dimensional simulations, that reconnection in a turbulent fluid occurs at a speed comparable to the rms velocity of the turbulence, regardless of the value of the resistivity. In particular, this is true for turbulent pressures much weaker than the magnetic field pressure so that the magnetic field lines are only slightly bent by the turbulence. These results are consistent with the proposal by Lazarian & Vishniac (1999) that reconnection is controlled by the stochastic diffusion of magnetic field lines, which produces a broad outflow of plasma from the reconnection zone. This work implies that reconnection in a turbulent fluid typically takes place in approximately a single eddy turnover time, with broad implications for dynamo activity and particle acceleration throughout the universe. In contrast, the reconnection in 2D configurations in the presence of turbulence depends on resistivity, i.e. is slow.

scholarly journals Three-dimensional magnetic reconnection and its application to solar flares

2017 ◽  
Vol 83 (1) ◽  
Author(s):  
Miho Janvier
Keyword(s):  
Kinetic Energy ◽  
Numerical Simulations ◽  
Magnetic Reconnection ◽  
Solar Flares ◽  
Magnetic Energy ◽  
Three Dimensional ◽  
Three Dimensions ◽  
Current Layer ◽  
Solar Observations ◽  
The Universe

Solar flares are powerful radiations occurring in the Sun’s atmosphere. They are powered by magnetic reconnection, a phenomenon that can convert magnetic energy into other forms of energy such as heat and kinetic energy, and which is believed to be ubiquitous in the universe. With the ever increasing spatial and temporal resolutions of solar observations, as well as numerical simulations benefiting from increasing computer power, we can now probe into the nature and the characteristics of magnetic reconnection in three dimensions to better understand the phenomenon’s consequences during eruptive flares in our star’s atmosphere. We review in the following the efforts made on different fronts to approach the problem of magnetic reconnection. In particular, we will see how understanding the magnetic topology in three dimensions helps in locating the most probable regions for reconnection to occur, how the current layer evolves in three dimensions and how reconnection leads to the formation of flux ropes, plasmoids and flaring loops.

scholarly journals Global MHD Simulation of the Weak Southward IMF Condition for Different Time Resolutions

2021 ◽  
Vol 8 ◽  
Author(s):  
Kyung Sun Park
Keyword(s):  
Magnetic Field ◽  
Electric Field ◽  
Magnetic Reconnection ◽  
Three Dimensional ◽  
Slow Solar Wind ◽  
Polar Cap ◽  
Plasma Properties ◽  
Simulation Results ◽  
Field Lines ◽  
The Impact

We performed high-resolution three-dimensional global MHD simulations to determine the impact of weak southward interplanetary magnetic field (IMF) (Bz = −2 nT) and slow solar wind to the Earth’s magnetosphere and ionosphere. We considered two cases of differing, uniform time resolution with the same grid spacing simulation to find any possible differences in the simulation results. The simulation results show that dayside magnetic reconnection and tail reconnection continuously occur even during the weak and steady southward IMF conditions. A plasmoid is generated on closed plasma sheet field lines. Vortices are formed in the inner side of the magnetopause due to the viscous-like interaction, which is strengthened by dayside magnetic reconnection. We estimated the dayside magnetic reconnection which occurred in relation to the electric field at the magnetopause and confirmed that the enhanced electric field is caused by the reconnection and the twisted structure of the electric field is due to the vortex. The simulation results of the magnetic field and the plasma properties show quasi-periodic variations with a period of 9–11 min between the appearances of vortices. Also the peak values of the cross-polar cap potential are both approximately 50 kV, the occurrence time of dayside reconnections are the same, and the polar cap potential patterns are the same in both cases. Thus, there are no significant differences in outcome between the two cases.

Formation of solar coronal loops through magnetic reconnection in an emerging active region

2021 ◽  
Author(s):  
Zhenyong Hou ◽  
Hui Tian ◽  
Hechao Chen ◽  
Xiaoshuai Zhu ◽  
Jiansen He ◽  
...  
Keyword(s):  
Magnetic Reconnection ◽  
Current Sheet ◽  
Emission Measure ◽  
Three Dimensional ◽  
Transverse Field ◽  
Power Spectral Analysis ◽  
Active Regions ◽  
Building Blocks ◽  
Coronal Loops ◽  
Field Lines

&lt;p&gt;Coronal loops are building blocks of solar active regions (ARs). However, their formation is not well understood. Here we present direct observational evidence for the formation of coronal loops through magnetic reconnection as new magnetic fluxes emerge to the solar atmosphere. Observations in the EUV passbands of SDO/AIA clearly show the newly formed loops following magnetic reconnection within a vertical current sheet. Formation of the loops is also seen in the H&amp;#945; images taken by NVST. The SDO/HMI observations show that a positive-polarity flux concentration moves toward a negative-polarity one with a speed of ~0.5 km s&lt;sup&gt;-1&lt;/sup&gt;&amp;#160;before the apparent formation of coronal loops. During the formation of coronal loops, we found signatures of flux cancellation and subsequent enhancement of the transverse field between the two polarities. We have reconstructed the three-dimensional magnetic field structure through a magnetohydrostatic model, which shows field lines consistent with the loops in AIA images. Numerous bright blobs with a width of ~1.5 Mm appear intermittently in the current sheet and move upward with apparent velocities of ~80 km s&lt;sup&gt;-1&lt;/sup&gt;. We have also identified plasma blobs moving to the footpoints of the newly formed large loops, with apparent velocities ranging from 30 to 50 km s&lt;sup&gt;-1&lt;/sup&gt;. A differential emission measure analysis shows that the temperature, emission measure and density of the bright blobs are 2.5-3.5 MK, 1.1-2.3&amp;#215;10&lt;sup&gt;28&lt;/sup&gt;&amp;#160;cm&lt;sup&gt;-5&lt;/sup&gt;&amp;#160;and 8.9-12.9&amp;#215;10&lt;sup&gt;9&lt;/sup&gt;&amp;#160;cm&lt;sup&gt;-3&lt;/sup&gt;, respectively. Power spectral analysis of these blobs indicates that the magnetic reconnection is inconsistent with the turbulent reconnection scenario.&lt;/p&gt;

scholarly journals 3D Magnetic Reconnection

2010 ◽  
Vol 6 (S271) ◽  
pp. 227-238 ◽  
Author(s):  
Clare E. Parnell ◽  
Rhona C. Maclean ◽  
Andrew L. Haynes ◽  
Klaus Galsgaard
Keyword(s):  
Magnetic Reconnection ◽  
Energy State ◽  
Single Point ◽  
Three Dimensional ◽  
Two Dimensions ◽  
Three Dimensions ◽  
Wide Range ◽  
Field Lines ◽  
Magnetohydrodynamic Models ◽  
The Magnetic Field

AbstractMagnetic reconnection is an important process that is prevalent in a wide range of astrophysical bodies. It is the mechanism that permits magnetic fields to relax to a lower energy state through the global restructuring of the magnetic field and is thus associated with a range of dynamic phenomena such as solar flares and CMEs. The characteristics of three-dimensional reconnection are reviewed revealing how much more diverse it is than reconnection in two dimensions. For instance, three-dimensional reconnection can occur both in the vicinity of null points, as well as in the absence of them. It occurs continuously and continually throughout a diffusion volume, as opposed to at a single point, as it does in two dimensions. This means that in three-dimensions field lines do not reconnect in pairs of lines making the visualisation and interpretation of three-dimensional reconnection difficult.By considering particular numerical 3D magnetohydrodynamic models of reconnection, we consider how magnetic reconnection can lead to complex magnetic topologies and current sheet formation. Indeed, it has been found that even simple interactions, such as the emergence of a flux tube, can naturally give rise to ‘turbulent-like’ reconnection regions.

Proton acceleration in three-dimensional non-null magnetic reconnection

2016 ◽  
Vol 82 (5) ◽  
Author(s):  
Z. Akbari ◽  
M. Hosseinpour ◽  
M. A. Mohammadi
Keyword(s):  
Magnetic Field ◽  
Energy Distribution ◽  
Magnetic Reconnection ◽  
Electric Fields ◽  
Three Dimensional ◽  
Null Point ◽  
Proton Acceleration ◽  
Electric And Magnetic Fields ◽  
Field Lines ◽  
The Magnetic Field

In a three-dimensional non-null magnetic reconnection, the process of magnetic reconnection takes place in the absence of a null point where the magnetic field vanishes. By randomly injecting a population of 10 000 protons, the trajectory and energy distribution of accelerated protons are investigated in the presence of magnetic and electric fields of a particular model of non-null magnetic reconnection with the typical parameters for the solar corona. The results show that protons are accelerated along the magnetic field lines away from the non-null point only at azimuthal angles where the magnitude of the electric field is strongest and therefore particles obtain kinetic energies of the order of thousands of MeV and even higher. Moreover, the energy distribution of the population depends strongly on the amplitude of the electric and magnetic fields. Comparison shows that a non-null magnetic reconnection is more efficient in accelerating protons to very high GeV energies than a null-point reconnection.

scholarly journals Quantification of Cold-Ion Beams in a Magnetic Reconnection Jet

2021 ◽  
Vol 8 ◽  
Author(s):  
Yu-Xuan Li ◽  
Wen-Ya Li ◽  
Bin-Bin Tang ◽  
C. Norgren ◽  
Jian-Sen He ◽  
...  
Keyword(s):  
Magnetic Reconnection ◽  
Plasma Sheet ◽  
Ion Beams ◽  
Distribution Functions ◽  
Diffusion Region ◽  
Hot Plasma ◽  
Order Of Magnitude ◽  
Velocity Distribution Functions ◽  
Cold Ions ◽  
Field Lines

Cold (few eV) ions of ionospheric origin are widely observed in the lobe region of Earth’s magnetotail and can enter the ion jet region after magnetic reconnection is triggered in the magnetotail. Here, we investigate a magnetotail crossing with cold ions in one tailward and two earthward ion jets observed by the Magnetospheric Multiscale (MMS) constellation of spacecraft. Cold ions co-existing with hot plasma-sheet ions form types of ion velocity distribution functions (VDFs) in the three jets. In one earthward jet, MMS observe cold-ion beams with large velocities parallel to the magnetic fields, and we perform quantitative analysis on the ion VDFs in this jet. The cold ions, together with the hot ions, are reconnection outflow ions and are a minor population in terms of number density inside this jet. The average bulk speed of the cold-ion beams is approximately 38% larger than that of the hot plasma-sheet ions. The cold-ion beams inside the explored jet are about one order of magnitude colder than the hot plasma-sheet ions. These cold-ion beams could be accelerated by the Hall electric field in the cold ion diffusion region and the shrinking magnetic field lines through the Fermi effect.

scholarly journals Jets of energetic particles generated by magnetic reconnection at a three-dimensional magnetic null

2006 ◽  
Vol 2 (14) ◽  
pp. 98-98
Author(s):  
Silvia Dalla ◽  
Philippa K. Browning
Keyword(s):  
Particle Acceleration ◽  
Magnetic Reconnection ◽  
Energetic Particle ◽  
Three Dimensional ◽  
Null Point ◽  
Numerical Code ◽  
Coronal Magnetic Fields ◽  
Field Lines ◽  
Magnetic Null ◽  
Magnetic Null Point

AbstractMagnetic reconnection is a candidate mechanism for particle acceleration in a variety of astrophysical contexts. It is now widely accepted that reconnection plays a key role in solar flares, and reconstructions of coronal magnetic fields indicate that three-dimensional (3D) magnetic null points can be present during flares. We investigate particle acceleration during spine reconnection at a 3D magnetic null point, using a test particle numerical code. We observe efficient particle acceleration and find that two energetic populations are produced: a trapped population of particles that remain in the vicinity of the null, and an escaping population, which leave the configuration in two symmetric jets along field lines near the spine. While the parameters used in our simulation aim to represent solar coronal plasma conditions of relevance for acceleration in flares, the fact that the 3D spine reconnection configuration naturally results in energetic particle jets may be of importance in other astrophysical situations. We also compare the results obtained for the spine reconnection regime with those for the other possible mode of 3D reconnection, fan reconnection. We find that in the latter case energetic particle jets are not produced, though acceleration is observed.

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