A profile of the Io dust cloud and plasma torus as observed from Juno

2020 ◽  
Author(s):  
John L. Jørgensen ◽  
Troelz Denver ◽  
Mathias Benn ◽  
Peter S. Jørgensen ◽  
Matija Herceg ◽  
...  
Keyword(s):  
Particle Flux ◽  
Relativistic Particle ◽  
Dust Cloud ◽  
High Energy ◽  
Trapped Particles ◽  
Field Lines ◽  
Plasma Torus ◽  
High Energy Particles ◽  
The Magnetic Field ◽  
Orbit Insertion

<p>The Juno MAG investigation’s dedicated star tracker, the Advanced Stellar Compass (ASC), has continuously monitored high energy particles fluxes in Jupiter’s magnetosphere subsequent to Juno’s orbit insertion on July 4, 2016. The ASC primary function is to provide an accurate inertial attitude reference, however, the most energetic particles in Jupiter’s trapped population is capable of penetrating the radiation shield of the ASC where they are registered. Such particles have energy >15MeV for electrons, >80MeV for protons, and >~GeV for heavier elements. With a sample cadence of 250ms, the ASC renders a detailed mapping of the trapped particles throughout space traversed by Juno. The particles travelling along the magnetic field lines crossing near the orbit of Io will be strongly influenced by interaction with any matter, moon, dust or plasma, which happens to be in their trajectory. The relativistic particle flux monitored, is highly relativistic, and has as such a modest retention time in any drift shell. The short lifetime of the trapped particles, and the constant scanning of field lines connecting to the Io environment enables a detailed profiling of the dust and plasma density, as well as the effect to/from Io itself. We present the measurement and their implications for the azimuthal and radial dust cloud and plasma torus.</p>

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.

scholarly journals Magnetized Black Holes: Ionized Keplerian Disks and Acceleration of Ultra-High Energy Particles

Proceedings ◽  
2019 ◽  
Vol 17 (1) ◽  
pp. 13 ◽  
Author(s):  
Zdeněk Stuchlík ◽  
Martin Kološ ◽  
Arman Tursunov
Keyword(s):  
Magnetic Field ◽  
Black Holes ◽  
Magnetic Fields ◽  
High Energy ◽  
Weak Magnetic Fields ◽  
Motion Transformation ◽  
Penrose Process ◽  
Field Lines ◽  
High Energy Particles ◽  
Quasiperiodic Oscillations

Properties of charged particle motion in the field of magnetized black holes (BHs) imply four possible regimes of behavior of ionized Keplerian disks: survival in regular epicyclic motion, transformation into chaotic toroidal state, destruction due to fall into the BHs, destruction due to escape along magnetic field lines (escape to infinity for disks orbiting Kerr BHs). The regime of the epicyclic motion influenced by very weak magnetic fields can be related to the observed high-frequency quasiperiodic oscillations. In the case of very strong magnetic fields particles escaping to infinity could form UHECR due to extremely efficient magnetic Penrose process – protons with energy E > 10 21 eV can be accelerated by supermassive black holes with M ∼ 10 10 M ⊙ immersed in magnetic field with B ∼ 10 4 Gs.

scholarly journals GREEN: A new Global Radiation Earth ENvironment model

2018 ◽  
Author(s):  
Angélica Sicard ◽  
Daniel Boscher ◽  
Sébastien Bourdarie ◽  
Didier Lazaro ◽  
Denis Standarovski ◽  
...  
Keyword(s):  
Global Radiation ◽  
High Energy ◽  
Local Models ◽  
Green Is ◽  
New Model ◽  
Environment Model ◽  
Earth Environment ◽  
Low Energies ◽  
Field Lines ◽  
The Magnetic Field

Abstract. GREEN (Global Radiation Earth ENvironment) is a new model providing fluxes at any location between L* = 1 and L* = 8 all along the magnetic field lines and for any energy between 1 keV to 10 MeV for electrons and between 1 keV and 800 MeV for protons. This model is composed of global models: AE8/AP8 and SPM for low energies and local models: SLOT model, OZONE, IGE-2006 for electrons and OPAL and geostationary model for protons. GREEN is not just a collection of various models, it calculates the electron and proton fluxes from the more relevant existing model for a given energy and location. Moreover, some existing models can be updated or corrected in GREEN. For examples, a new version of the SLOT model is presented here and has been integrated in GREEN. Moreover, a new model of proton flux at geostationary orbit (IGP), developed few years ago is also detailed here and integrated in GREEN. Finally a correction of AE8 model at high energy for L* 

Solar Physics: Overview

2020 ◽  
Author(s):  
E.R. Priest
Keyword(s):  
Solar Physics ◽  
Theoretical Models ◽  
High Energy ◽  
The Sun ◽  
Dynamo Action ◽  
Current Time ◽  
Definitive Answer ◽  
Year 2000 ◽  
High Energy Particles ◽  
The Magnetic Field

Solar physics is one of the liveliest branches of astrophysics at the current time, with many major advances that have been stimulated by observations from a series of space satellites and ground-based telescopes as well as theoretical models and sophisticated computational experiments. Studying the Sun is of key importance in physics for two principal reasons. Firstly, the Sun has major effects on the Earth and on its climate and space weather, as well as other planets of the solar system. Secondly, it represents a Rosetta stone, where fundamental astrophysical processes can be investigated in great detail. Yet, there are still major unanswered questions in solar physics, such as how the magnetic field is generated in the interior by dynamo action, how magnetic flux emerges through the solar surface and interacts with the overlying atmosphere, how the chromosphere and corona are heated, how the solar wind is accelerated, how coronal mass ejections are initiated and how energy is released in solar flares and high-energy particles are accelerated. Huge progress has been made on each of these topics since the year 2000, but there is as yet no definitive answer to any of them. When the answers to such puzzles are found, they will have huge implications for similar processes elsewhere in the cosmos but under different parameter regimes.

Trapped particles around Jupiter detected by Advanced Stellar Compass

2020 ◽  
Author(s):  
Matija Herceg ◽  
John L. Jørgensen ◽  
Peter S. Jørgensen ◽  
Jose M. G. Merayo ◽  
Mathias Benn ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Pitch Angle ◽  
Magnetic Field Gradient ◽  
Rotation Period ◽  
High Energy ◽  
Radiation Shielding ◽  
Trapped Particles ◽  
Dipolar Fields ◽  
A Charge ◽  
The Magnetic Field

<p>The Advanced Stellar Compass (ASC), attitude reference for the MAG investigation onboard Juno, has continuously monitored high energy particles fluxes in Jupiter’s magnetosphere since Juno’s orbit insertion. The instrument performs this function by tracking the effects of radiation with sufficient energy to transit the instrument’s radiation shielding. Particles that Juno ASC observes have energy >15MeV for electrons, >80MeV for protons, and >~GeV for heavier elements.</p><p>Completing 24 highly elliptical orbits around Jupiter, results in a fairly detailed mapping of the trapped high energy flux at up to 20 Jupiter radius distances.</p><p>Traveling at velocities close to the speed of light, electrons measured by the ASC, maintain the motion governed by the three adiabatic invariants: gyrating motion around the magnetic field line, a north-south magnetic pole particle bounce, and a charge dependent drift around the planet.</p><p>The bounce period is much smaller than the Jovian rotation period, and a large east-west drift component is caused by the magnetic field gradient. For these reasons, the drift shell description traditionally used for dipolar fields, are far from adequate to describe the behavior of energetic particles travelling close to Jupiter.</p><p>In this work, we present the distribution of the trapped high energy electrons around Jupiter. Furthermore, we have constrained the spatial extent of the stable trapped regions and are presenting the distinctive pitch angle and its correlation with ”life” of a particle. At certain distances from Jupiter, pitch angle dependency is not as important to keep the particle trapped as is the injected energy. We also develop an adiabatic map which describes the radial bands for stable trapped particles as a function of the pitch angle and energy.</p><p> </p>

scholarly journals Electron dynamics during substorm dipolarization in Mercury's magnetosphere

2005 ◽  
Vol 23 (10) ◽  
pp. 3389-3398 ◽  
Author(s):  
D. C. Delcourt ◽  
K. Seki ◽  
N. Terada ◽  
Y. Miyoshi
Keyword(s):  
Magnetic Field ◽  
High Energy ◽  
Expansion Phase ◽  
Earth’S Magnetosphere ◽  
High Energy Electrons ◽  
Earth's Magnetosphere ◽  
Magnetic Field Model ◽  
Particle Simulations ◽  
Field Lines ◽  
The Magnetic Field

Abstract. We examine the nonlinear dynamics of electrons during the expansion phase of substorms at Mercury using test particle simulations. A simple model of magnetic field line dipolarization is designed by rescaling a magnetic field model of the Earth's magnetosphere. The results of the simulations demonstrate that electrons may be subjected to significant energization on the time scale (several seconds) of the magnetic field reconfiguration. In a similar manner to ions in the near-Earth's magnetosphere, it is shown that low-energy (up to several tens of eV) electrons may not conserve the second adiabatic invariant during dipolarization, which leads to clusters of bouncing particles in the innermost magnetotail. On the other hand, it is found that, because of the stretching of the magnetic field lines, high-energy electrons (several keVs and above) do not behave adiabatically and possibly experience meandering (Speiser-type) motion around the midplane. We show that dipolarization of the magnetic field lines may be responsible for significant, though transient, (a few seconds) precipitation of energetic (several keVs) electrons onto the planet's surface. Prominent injections of energetic trapped electrons toward the planet are also obtained as a result of dipolarization. These injections, however, do not exhibit short-lived temporal modulations, as observed by Mariner-10, which thus appear to follow from a different mechanism than a simple convection surge.

Plasma flows in a converging and diverging configuration and the associated plasma particle acceleration: kinetic approach

1975 ◽  
Vol 13 (3) ◽  
pp. 481-497 ◽  
Author(s):  
M. Fridman
Keyword(s):  
Magnetic Field ◽  
Average Velocity ◽  
Particle Flux ◽  
Plasma Particle ◽  
Series Development ◽  
Field Lines ◽  
The One ◽  
The Relationship ◽  
The Magnetic Field ◽  
Transport Laws

Transport laws in collisionless systems must be derived from the one-particle Liouville equation. The simplest cases are those of the CGL invariants along the magnetic field lines, together with the resulting equations of continuity and motion, in circumstances where a supersonic particle flux is parallel to a diminishing magnetic field. We give functional expressions for the two contributions to the parallel heat flux, with integrated forms of kinetic theory. The general expressions, corresponding to the moments of greater order, coincide with those obtained by series development of the differential equation of moments. Moreover, we illustrate a case of both parallel and convergent flux, for which the equation of continuity gives considerable acceleration to the precipitation flux average velocity in the absence of any important electric field, because that acceleration is important in understanding the relationship between the plasmasheet and the ionosphere.

scholarly journals Plasma Energetics in Solar Flares

1980 ◽  
Vol 5 ◽  
pp. 343-350 ◽  
Author(s):  
Gerard Van Hoven
Keyword(s):  
Gamma Rays ◽  
Solar Flares ◽  
High Energy ◽  
Physical Mechanisms ◽  
Very High Energy ◽  
Physical Effects ◽  
High Energy Particles ◽  
The Magnetic Field ◽  
Dissipation Processes ◽  
Very High

I want to begin with the observation, which I will try to make clear in the following, that a solar flare comprises an incredibly complex set of phenomena. This is not only true with respect to what is seen and measured in spectacular examples, but also when one considers the constituent parts of simple, even idealized, cases. A series of different physical effects lead, as one illustration, to radiations from the flare-instability site and its surroundings which span the range from meter waves to gamma rays (Svestka 1976, Sturrock 1979).To fit within the context of this discussion, I will concentrate on the high-temperature and quasi-thermal aspects of a flare, and on the basic physical mechanisms connected with the primary energization and dissipation processes. Thus, I will treat the reconnection of the magnetic field, the bulk acceleration of particles, the thermalization and the ultimate radiation of the energy. I will not treat the optical manifestations or, at the other extreme, the acceleration of very high energy particles.

scholarly journals Cosmic ray interactions in the solar atmosphere

2019 ◽  
Vol 491 (4) ◽  
pp. 4852-4856 ◽  
Author(s):  
Hugh S Hudson ◽  
Alec MacKinnon ◽  
Mikolaj Szydlarski ◽  
Mats Carlsson
Keyword(s):  
Magnetic Field ◽  
Open Field ◽  
Solar Atmosphere ◽  
Cosmic Ray ◽  
High Energy ◽  
Emission Anisotropy ◽  
Flux Tubes ◽  
Wide Range ◽  
High Energy Particles ◽  
The Magnetic Field

ABSTRACT High-energy particles enter the solar atmosphere from Galactic or solar coronal sources, and produce ‘albedo’ emission from the quiet Sun that is now observable across a wide range of photon energies. The interaction of high-energy particles in a stellar atmosphere depends essentially upon the joint variation of the magnetic field and plasma density, which heretofore has been characterized parametrically as P ∝ Bα with P the gas pressure and B the magnitude of the magnetic field. We re-examine that parametrization by using a self-consistent 3D MHD model (Bifrost) and show that this relationship tends to P ∝ B3.5 ± 0.1 based on the visible portions of the sample of open-field flux tubes in such a model, but with large variations from point to point. This scatter corresponds to the strong meandering of the open-field flux tubes in the lower atmosphere, which will have a strong effect on the prediction of the emission anisotropy (limb brightening). The simulations show that much of the open flux in coronal holes originates in weak-field regions within the granular pattern of the convective motions seen in the simulations.

A thruster using magnetic reconnection to create a high-speed plasma jet

2018 ◽  
Vol 84 (2) ◽  
pp. 20801 ◽  
Author(s):  
Stephen N. Bathgate ◽  
Marcela M.M. Bilek ◽  
Iver H. Cairns ◽  
David R. McKenzie
Keyword(s):  
Magnetic Reconnection ◽  
Solar Flares ◽  
High Speed ◽  
Laboratory Experiments ◽  
Argon Plasma ◽  
High Energy ◽  
High Energy Electrons ◽  
Lorentz Forces ◽  
Field Lines ◽  
The Magnetic Field

Plasma thrusters propel spacecraft by the application of Lorentz forces to ionized propellants. Despite evidence that Lorentz forces resulting from magnetic reconnection in solar flares and Earth's magnetopause produce jets of energetic particles, magnetic reconnection has only recently been considered as a means of accelerating plasma in a thruster. Based on theoretical principles, a pulsed magnetic reconnection thruster consisting of two parallel-connected slit coaxial tubes was constructed. The thruster was operated in argon plasma produced by RF energy at 13.56 MHz. A 1.0 ms current pulse of up to 1500 A was applied to the tubes. Three results provide evidence for magnetic reconnection. (1) The production of high-energy electrons resembling the outflow that is observed in the reconnection of field lines in solar flares and in laboratory experiments. (2) The high-energy electron current coincided with the rise of the magnetic field in the thruster and was followed by a large ion current. (3) In accordance with known physics of magnetic reconnection, ion currents were found to increase as the plasma became less collisional. The Alfvén speed of the outflowing ions was calculated to be 8.48 × 103 m s−1 corresponding to an Isp of 860 s.

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