scholarly journals Motion of Flare Footpoint Emission and Inferred Electric Field in Reconnecting Current Sheets

2002 ◽  
Vol 565 (2) ◽  
pp. 1335-1347 ◽  
Author(s):  
Jiong Qiu ◽  
Jeongwoo Lee ◽  
Dale E. Gary ◽  
Haimin Wang
Keyword(s):  
Electric Field ◽  
Current Sheets

Solar Orbiter observations of solar wind current sheets and their deHoffman-Teller frames

2021 ◽  
Author(s):  
Konrad Steinvall ◽  
Yuri Khotyaintsev ◽  
Giulia Cozzani ◽  
Andris Vaivads ◽  
Christopher Owen ◽  
...  
Keyword(s):  
Solar Wind ◽  
Electric Field ◽  
Wind Velocity ◽  
Solar Wind Velocity ◽  
Field Measurements ◽  
Velocity Measurements ◽  
Current Sheets ◽  
Spacecraft Orbit ◽  
Electric Field Measurements ◽  
Good Agreement

<p>Solar wind current sheets have been extensively studied at 1 AU. The recent advent of Parker Solar Probe and Solar Orbiter (SolO) has enabled us to study these structures at a range of heliocentric distances.</p><p>We present SolO observations of current sheets in the solar wind at heliocentric distances between 0.55 and 0.85 AU, some of which show signatures of ongoing magnetic reconnection. We develop a method to find the deHoffman-Teller frame which minimizes the Y-component (the component tangential to the spacecraft orbit) of the electric field. Using the electric field measurements from RPW and magnetic field measurements from MAG, we use our method to determine the deHoffman-Teller frame of solar wind current sheets. The same method can also be used on the Alfvénic turbulence and structures found in the solar wind to obtain a measure of the solar wind velocity.</p><p>Our preliminary results show a good agreement between our modified deHoffmann-Teller analysis based on the single component E-field, and the conventional deHoffman-Teller analysis based on 3D plasma velocity measurements from PAS. This opens up the possibility to use the RPW and MAG data to obtain an estimate of the solar wind velocity when particle data is unavailable.</p>

scholarly journals Particle acceleration in coalescent and squashed magnetic islands

2018 ◽  
Vol 620 ◽  
pp. A121 ◽  
Author(s):  
Q. Xia ◽  
V. Zharkova
Keyword(s):  
Particle Acceleration ◽  
Electric Field ◽  
Power Laws ◽  
Particle Energy ◽  
Energy Spectra ◽  
Magnetic Islands ◽  
Current Sheets ◽  
The Difference ◽  
Energy Gains ◽  
Electron Clouds

Aims. Magnetic reconnection in large Harris-type reconnecting current sheets (RCSs) with a single X-nullpoint often leads to the occurrence of magnetic islands with multiple O- and X-nullpoints. Over time these magnetic islands become squashed, or coalescent with two islands merging, as has been observed indirectly during coronal mass ejection and by in-situ observations in the heliosphere and magnetotail. These points emphasise the importance of understanding the basic energising processes of ambient particles dragged into current sheets with magnetic islands of different configuration. Methods. Trajectories of protons and electrons accelerated by a reconnection electric field are investigated using a test particle approach in RCSs with different 3D magnetic field topologies defined analytically for multiple X- and O-nullpoints. Trajectories, densities, and energy distributions are explored for 106 thermal particles dragged into the current sheets from different sides and distances. Results. This study confirms that protons and electrons accelerated in magnetic islands in the presence of a strong guiding field are ejected from a current sheet into the opposite semiplanes with respect to the midplane. Particles are found to escape O-nullpoints only through the neighbouring X-nullpoints along (not across) the midplane following the separation law for electrons and protons in a given magnetic topology. Particles gain energy either inside O-nullpoints or in the vicinity of X-nullpoints that often leads to electron clouds formed about the X-nullpoint between the O-nullpoints. Electrons are shown to be able to gain sub-relativistic energies in a single magnetic island. Energy spectra of accelerated particles are close to power laws with spectral indices varying from 1.1 to 2.4. The more squashed the islands the larger the difference between the energy gains by transit and bounced particles, which leads to their energy spectra having double maxima that gives rise to fast-growing turbulence. Conclusions. Particles are shown to gain the most energy in multiple X-nullpoints between O-nullpoints (or magnetic islands). This leads to the formation of electron clouds between magnetic islands. Particle energy gains are much larger in squashed islands than in coalescent ones. In summary, particle acceleration by a reconnection electric field in magnetic islands is much more effective than in an RCS with a single X-nullpoint.

Investigating the Mechanism of the Acceleration of Cosmic Rays during Solar Flares Using the Electric Field in Current Sheets of the Solar Corona

2021 ◽  
Vol 85 (8) ◽  
pp. 925-927
Author(s):  
A. I. Podgorny ◽  
I. M. Podgorny ◽  
A. V. Borisenko ◽  
E. V. Vashenyuk ◽  
Yu. V. Balabin ◽  
...  
Keyword(s):  
Cosmic Rays ◽  
Electric Field ◽  
Solar Corona ◽  
Solar Flares ◽  
Current Sheets

scholarly journals The structure of strongly tilted current sheets in the Earth magnetotail

2014 ◽  
Vol 32 (2) ◽  
pp. 133-146 ◽  
Author(s):  
I. Y. Vasko ◽  
A. V. Artemyev ◽  
A. A. Petrukovich ◽  
R. Nakamura ◽  
L. M. Zelenyi
Keyword(s):  
Magnetic Field ◽  
Electric Field ◽  
Current Density ◽  
Neutral Plane ◽  
Current Sheets ◽  
Transverse Current ◽  
The Earth ◽  
Electron Current Density ◽  
Total Current Density ◽  
Using Data

Abstract. We investigate strongly tilted (in the y–z GSM plane) current sheets (CSs) in the Earth magnetotail using data from the Cluster mission. We analyze 29 CS crossings observed in 2001–2004. The characteristic current density, magnetic field at the CS boundary and the CS thickness of strongly tilted CSs are similar to those reported previously for horizontal (not tilted) CSs. We confirm that strongly tilted CSs are generally characterized by a rather large northward component of the magnetic field. The field-aligned current in strongly tilted CSs is on average two times larger than the transverse current. The proton adiabaticity parameter, κp, is larger than 0.5 in 85% of strongly tilted CSs due to the large northward magnetic field. Thus, the proton dynamics is stochastic for 18 current sheets with 0.5 < κp < 3 and protons are magnetized for 6 sheets with κp > 3, whereas electrons are magnetized for all observed current sheets. Strongly tilted CSs provide a unique opportunity to measure the electric field component perpendicular to the CS plane. We find that most of the electric field perpendicular to the CS plane is due to the decoupling of electron and ion motions (plasma polarization). For 27 CSs we determine profiles of the electrostatic potential, which is due to the plasma polarization. Drops in the potential between the neutral plane and the CS boundary are within the range of 200 V to 12 kV, while maximal values of the electric field are within the range of 0.2 mV m−1 to 8 mV m−1. For 16 CSs the observed potentials are in accordance with Ohm's law, if the electron current density is assumed to be comparable to the total current density. In 15 of these CSs the profile of the polarization potential is approximately symmetric with respect to the neutral plane and has minimum therein.

Resolution in photoelectron microscopy

1991 ◽  
Vol 49 ◽  
pp. 458-459
Author(s):  
G. F. Rempfer
Keyword(s):  
Electron Microscopy ◽  
Electric Field ◽  
Ultraviolet Light ◽  
Uniform Field ◽  
Virtual Image ◽  
Lens System ◽  
Photoemission Electron Microscopy ◽  
Planar Electrode ◽  
Electron Lens ◽  
Photoemission Electron

In photoelectron microscopy (PEM), also called photoemission electron microscopy (PEEM), the image is formed by electrons which have been liberated from the specimen by ultraviolet light. The electrons are accelerated by an electric field before being imaged by an electron lens system. The specimen is supported on a planar electrode (or the electrode itself may be the specimen), and the accelerating field is applied between the specimen, which serves as the cathode, and an anode. The accelerating field is essentially uniform except for microfields near the surface of the specimen and a diverging field near the anode aperture. The uniform field forms a virtual image of the specimen (virtual specimen) at unit lateral magnification, approximately twice as far from the anode as is the specimen. The diverging field at the anode aperture in turn forms a virtual image of the virtual specimen at magnification 2/3, at a distance from the anode of 4/3 the specimen distance. This demagnified virtual image is the object for the objective stage of the lens system.

Field-assisted ionization theory for microscopists

1994 ◽  
Vol 52 ◽  
pp. 820-821
Author(s):  
Patrick P. Camus
Keyword(s):  
Electric Field ◽  
Electron Tunneling ◽  
Ionization Probability ◽  
Critical Distance ◽  
Tunneling Probability ◽  
Field Ionization ◽  
Radius Of Curvature ◽  
Field Evaporation ◽  
A Value ◽  
Ion Emission

The theory of field ion emission is the study of electron tunneling probability enhanced by the application of a high electric field. At subnanometer distances and kilovolt potentials, the probability of tunneling of electrons increases markedly. Field ionization of gas atoms produce atomic resolution images of the surface of the specimen, while field evaporation of surface atoms sections the specimen. Details of emission theory may be found in monographs.Field ionization (FI) is the phenomena whereby an electric field assists in the ionization of gas atoms via tunneling. The tunneling probability is a maximum at a critical distance above the surface,xc, Fig. 1. Energy is required to ionize the gas atom at xc, I, but at a value reduced by the appliedelectric field, xcFe, while energy is recovered by placing the electron in the specimen, φ. The highest ionization probability occurs for those regions on the specimen that have the highest local electric field. Those atoms which protrude from the average surfacehave the smallest radius of curvature, the highest field and therefore produce the highest ionizationprobability and brightest spots on the imaging screen, Fig. 2. This technique is called field ion microscopy (FIM).

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