Mapping magnetic field and relativistic electrons along a solar flare current sheet

2020 ◽  
Author(s):  
Gregory Fleishman ◽  
Bin Chen ◽  
Gary Dale ◽  
Gelu Nita et al.
Keyword(s):  
Magnetic Field ◽  
Solar Flare ◽  
Current Sheet ◽  
Energy Release ◽  
Large Scale ◽  
Local Maximum ◽  
High Energy ◽  
Relativistic Electrons ◽  
Flare Loop ◽  
Magnetic Bottle

<p>In the standard model of solar flares, a large-scale reconnection current sheet (RCS) is postulated as the central engine for powering the flare energy release and accelerating particles. However, where and how the energy release and particle acceleration occur remain unclear due to the lack of measurements for the magnetic properties of the RCS. Here we report the first measurement of spatially-resolved magnetic field and flare-accelerated relativistic electrons along a large-scale RCS in a solar flare. The measured magnetic field profile shows a local maximum where the reconnecting field lines of opposite polarities closely approach each other, known as the reconnection X point. The measurements also reveal a local minimum near the bottom of the RCS above the flare loop-top, referred to as a "magnetic bottle". This spatial structure agrees with theoretical predictions and numerical modeling results. A strong reconnection electric field of over 4000 V/m is inferred near the X point. This location, however, shows a local depletion of microwave-emitting relativistic electrons. In contrast, the relativistic electrons concentrate at or near the magnetic bottle structure, where more than 99% of them reside at each instant. Our observations suggest crucial new input to the current picture of high energy electron acceleration.</p>

scholarly journals Measurement of magnetic field and relativistic electrons along a solar flare current sheet

2020 ◽  
Vol 4 (12) ◽  
pp. 1140-1147 ◽  
Author(s):  
Bin Chen ◽  
Chengcai Shen ◽  
Dale E. Gary ◽  
Katharine K. Reeves ◽  
Gregory D. Fleishman ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Flare ◽  
Current Sheet ◽  
Relativistic Electrons

scholarly journals Importance of Magnetic Effects in a Two-Flow Model for Extragalactic Radio Jets

1990 ◽  
Vol 140 ◽  
pp. 445-445
Author(s):  
H. Sol ◽  
G. Pelletier ◽  
E. Asseo
Keyword(s):  
Magnetic Field ◽  
Coming Out ◽  
Large Scale ◽  
Flow Model ◽  
Minimal Distance ◽  
Relativistic Electrons ◽  
Ambient Plasma ◽  
Relaxation Zone ◽  
Radio Jets ◽  
The Magnetic Field

We propose a model for extragalactic radio jets in which two different flows of particles are taken into account, (i) a beam of relativistic electrons and positrons extracted from the funnel of accretion disc and responsible for the observed superluminal motion, (ii) a classical or mildly relativistic wind of electrons and protons coming out from all parts of the disc (Sol et al., 1989). Studying the mutual interaction of the two flows, we show that the configuration is not destroyed by the plasma-beam instability as long as the magnetic field, assumed longitudinal, is strong enough, with an electron gyrofrequency ωc = eB/mec greater than the ambient plasma frequency ωp = (4πnpe2)1/2 (Pelletier et al., 1988). When ωc < ωp, the relativistic beam loses its energy and its momentum mainly through the development of strong Langmuir turbulence in the wind, and disappears quietly after some relaxation zone where heating and entrainment of the wind occur. This emphasizes one aspect of the important role likely played by the magnetic field in the dynamics of extragalactic jets and provides one example in which the magnetic field, acting on the microscopic scale of an interaction, induces strong effects on large–scale structures. Detailed data on the closest known superluminal radio source 3C120 (Walker et al., 1987, 1988; Benson et al., 1988) allow a check on the likelihood of our model. Observational estimates of the variation along the jet of the magnetic field and of the ambient plasma density np suggest that the magnetic field reaches its critical value (corresponding to ωc = ωp) at a minimal distance of about 1.4 kpc from the central engine. This is amazingly close to the location of the 4′–radio knot, a “rather curious structure” described by Walker et al. (1987), which we interpret as the beam relaxation zone in the context of our two–flow model (Sol et al., 1989).

scholarly journals The Magnetic Field Near the Local Bubble

1997 ◽  
Vol 166 ◽  
pp. 227-238
Author(s):  
Carl Heiles
Keyword(s):  
Magnetic Field ◽  
Large Scale ◽  
Zeeman Splitting ◽  
Relativistic Electrons ◽  
Local Bubble ◽  
Scale Field ◽  
Large Scale Field ◽  
Field Lines ◽  
Hi Shells ◽  
The Magnetic Field

AbstractThere are almost no direct observational indicators of the magnetic field inside the local bubble. Just outside the bubble, the best tracers are stellar polarization and HI Zeeman splitting. These show that the local field does not follow the large-scale Galactic field. Here we discuss whether the deformation of the large-scale field by the local HI shells is consistent with the observations. We concentrate on the Loop 1 region, and find that the field lines are well-explained by this idea; in addition, the bright radio filaments of Radio Loop 1 delineate particular field lines that are “lit up” by an excess of relativistic electrons.

scholarly journals Very High-Energy Emission from the Direct Vicinity of Rapidly Rotating Black Holes

Galaxies ◽  
2018 ◽  
Vol 6 (4) ◽  
pp. 122 ◽  
Author(s):  
Kouichi Hirotani
Keyword(s):  
Magnetic Field ◽  
Black Holes ◽  
Black Hole ◽  
Electric Field ◽  
Gamma Rays ◽  
Accretion Rate ◽  
High Energy ◽  
Relativistic Electrons ◽  
Field Lines ◽  
The Magnetic Field

When a black hole accretes plasmas at very low accretion rate, an advection-dominated accretion flow (ADAF) is formed. In an ADAF, relativistic electrons emit soft gamma-rays via Bremsstrahlung. Some MeV photons collide with each other to materialize as electron-positron pairs in the magnetosphere. Such pairs efficiently screen the electric field along the magnetic field lines, when the accretion rate is typically greater than 0.03–0.3% of the Eddington rate. However, when the accretion rate becomes smaller than this value, the number density of the created pairs becomes less than the rotationally induced Goldreich–Julian density. In such a charge-starved magnetosphere, an electric field arises along the magnetic field lines to accelerate charged leptons into ultra-relativistic energies, leading to an efficient TeV emission via an inverse-Compton (IC) process, spending a portion of the extracted hole’s rotational energy. In this review, we summarize the stationary lepton accelerator models in black hole magnetospheres. We apply the model to super-massive black holes and demonstrate that nearby low-luminosity active galactic nuclei are capable of emitting detectable gamma-rays between 0.1 and 30 TeV with the Cherenkov Telescope Array.

The Tearing Mode Instability in a Partially Ionized Plasma

1979 ◽  
Vol 3 (6) ◽  
pp. 367-368 ◽  
Author(s):  
N. F. Cramer ◽  
I. J. Donnelly
Keyword(s):  
Magnetic Field ◽  
Star Formation ◽  
Solar Flare ◽  
Experimental Evidence ◽  
Energy Release ◽  
Release Mechanism ◽  
Tearing Mode ◽  
Mode Instability ◽  
Laboratory Plasma ◽  
Tearing Instability

The resistive tearing mode instability is a mechanism that in some cases will render unstable a magnetohydrodynamic equilibrium of a plasma that is ideally stable, i.e. stable if no dissipative oiesses are taken into account. There is much experimental evidence that this instability is the cause of the current disruptions observed in laboratory plasma devices (von Goeler et al. 1974). In the astrophysical context, the instability has been invoked in connection with the solar flare energy release mechanism (Coppi and Friedland 1971) and the problem of the disconnection of the protostar matter from the interstellar magnetic field during star formation (Mestel 1966). In the latter problem the tearing instability gives rise to a much smaller timescale for magnetic reconnection than does ordinary resistive diffusion.

scholarly journals On the flux of high-energy cosmogenic neutrinos and the influence of the extragalactic magnetic field

2019 ◽  
Vol 488 (1) ◽  
pp. L119-L122 ◽  
Author(s):  
David Wittkowski ◽  
Karl-Heinz Kampert
Keyword(s):  
Magnetic Field ◽  
Cosmic Rays ◽  
Large Scale ◽  
Neutrino Flux ◽  
Cosmic Ray ◽  
High Energy ◽  
Observation Time ◽  
Cosmological Time ◽  
Cosmic Background ◽  
The Universe

ABSTRACT Cosmogenic neutrinos originate from interactions of cosmic rays propagating through the universe with cosmic background photons. Since both high-energy cosmic rays and cosmic background photons exist, the existence of high-energy cosmogenic neutrinos is certain. However, their flux has not been measured so far. Therefore, we calculated the flux of high-energy cosmogenic neutrinos arriving at the Earth on the basis of elaborate 4D simulations that take into account three spatial degrees of freedom and the cosmological time-evolution of the universe. Our predictions for this neutrino flux are consistent with the recent upper limits obtained from large-scale cosmic-ray experiments. We also show that the extragalactic magnetic field has a strong influence on the neutrino flux. The results of this work are important for the design of future neutrino observatories, since they allow to assess the detector volume and observation time that are necessary to detect high-energy cosmogenic neutrinos in the near future. An observation of such neutrinos would push multimessenger astronomy to hitherto unachieved energy scales.

scholarly journals Dynamics of Variable Dusk-Dawn Flow Associated with Magnetotail Current Sheet Flapping

2021 ◽  
Author(s):  
James Henry Lane ◽  
Adrian Grocott ◽  
Nathan Anthony Case ◽  
Maria-Theresia Walach
Keyword(s):  
Magnetic Field ◽  
Current Sheet ◽  
Field Data ◽  
Large Scale ◽  
Magnetic Field Data ◽  
Analysis Technique ◽  
Upstream Solar Wind ◽  
Magnetotail Dynamics ◽  
Magnetotail Current Sheet

Abstract. Previous observations have provided a clear indication that the dusk-dawn (v⊥y) sense of both slow (< 200 km s−1) and fast (> 200 km s−1) convective magnetotail flows is strongly governed by the Interplanetary Magnetic Field (IMF) By conditions. The related “untwisting hypothesis” of magnetotail dynamics is commonly invoked to explain this dependence, in terms of a large-scale magnetospheric asymmetry. In the current study, we present Cluster spacecraft observations from 12 October 2006 of earthward convective magnetotail plasma flows whose dusk-dawn sense disagrees with the untwisting hypothesis of IMF By control of the magnetotail flows. During this interval, observations of the upstream solar wind conditions from OMNI, and ionospheric convection data using SuperDARN, indicate a large-scale magnetospheric morphology consistent with positive IMF By penetration into the magnetotail. Inspection of the in-situ Cluster magnetic field data reveals a flapping of the magnetotail current sheet; a phenomenon known to influence dusk-dawn flow. Results from the curlometer analysis technique suggest that the dusk-dawn flow perturbations may have been driven by the J x B force associated with a dawnward-propagating flapping of the magnetotail current sheet, locally overriding the expected IMF By control of the flows. We conclude that invocation of the untwisting hypothesis may be inappropriate when interpreting intervals of dynamic magnetotail behaviour such as during current sheet flapping.

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