Particle acceleration in the process of eruptive opening and reconnection of magnetic fields
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Svestka, Z.↗
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AM Herculis binaries - Particle acceleration, radio emission and synchronization
It has been suggested that the recently discovered radio emission from AM Her arises as a result of gyrosynchrotron radiation from electrons at energies approximately 400 keV in the magnetosphere of the white dwarf. However, no mechanism for producing such energetic electrons was discussed. In this paper, it is argued that small departures from synchronous rotation can cause the companion star to act as a unipolar inductor. This leads to high voltages being produced across the companion star, which provides the necessary acceleration mechanism. This also implies that if the magnetic white dwarf was formed with a rapid rotation, synchronization would be achieved on a time scale approximately 10,000 yr.
Chanmugam, G.↗
Particle acceleration parallel and perpendicular to the magnetic field observed by DE-2
Observations by the instrument payload on DE-2 have been used to study the plasma and electrodynamic properties of the ionosphere when field-aligned currents approaching 100 microA/sq m flow at about 900-km altitude. In such a situation, it is found that the thermal ions may account for a substantial fraction of the current carriers and that the bulk of the energetic electron population has undergone a net acceleration of a few hundred electron volts. Large amplitude electrostatic waves that have a maximum near 100 Hz and an energetic ion population that shows evidence for both parallel and perpendicular acceleration to about 30 eV also accompany such events. The horizontal thermal ion drift (electric field) that accompanies these plasma phenomena has extremely large gradients over small spatial scales. Such a signature is consistent with a requirement for a large field-aligned current, and a limit to the available field-aligned potential difference that may be applied to the plasma.
Heelis, R. A.↗
Space experiments with particle accelerators
Electron and plasma beams and neutral gas plumes were injected into the space environment by instruuments on Spacelab 1, and various diagnostic measurements including television camera observations were performed. The results yield information on vehicle charging and neutralization, beam-plasma interactions, and ionization enhancement by neutral beam injection.
Obayashi, T.↗
Primary gamma-rays with E gamma or = to 10(15) eV: Evidence for ultrahigh energy particle acceleration in galactic sources
The recently observed primary ultra high energy gamma-rays (UHEGR) testify to the cosmic ray (CR) acceleration in the Galaxy. The available data may be interpreted as gamma-ray production due to photomeson production in CR sources.
Aharonian, F. A.↗
Efficiency of regular acceleration of particles by a shock wave at different injection regimes
A significant fraction of the inflowing plasma energy in the collisionless shock vicinity might be transferred to the particles accelerated by a regular acceleration mechanism. The accelerated particles back pressure modifies an ininite planar shock structure so that a profile of the plasma flow velocity in the shock frame has two characteristic length scales.
Berezhko, E. G.↗
Giant molecular clouds as regions of particle acceleration
One of the most interesting results of investigations carried out on the satellites SAS-II and COS-B is the discovery of unidentified discrete gamma sources. Possibly a considerable part of them may well be giant molecular clouds. Gamma emission from clouds is caused by the processes with participation of cosmic rays. The estimation of the cosmic ray density in clouds has shown that for the energy E approx. = I GeV their density can 10 to 1000 times exceed the one in intercloud space. We have made an attempt to determine the mechanism which could lead to the increase in the cosmic ray density in clouds.
Dogiel, V. A.↗
Pulsars as cosmic ray particle accelerators: Proton orbits
Proton orbits are calculated in the electromagnetic vacuum field of a magnetic point dipole rotating with its angular velocity omega perpendicular to its dipole moment mu by numerical integration of the Lorentz-Dirac equation. Trajectories are shown and discussed for various initial conditions. A critical surface is shown separating initial positions of protons which finally hit the pulsar in the polar region from those which finally recede to infinity.
Thielheim, K. O.↗
Pulsars as cosmic ray particle accelerators: Dynamics of electrons
The Lorentz-Dirac-equation with Landau approximation has been solved numerically for electrons in the electromagnetic field of a magnetic dipole rotating with the angular velocity omega perpendicular to its magnetic moment mu. Results are discussed with respect to electron orbits and energy development.
Thielheim, K. O.↗
Stochastic particle acceleration in flaring stars
The acceleration of electrons by the Fermi-Parker mechanisms in a quasistationary turbulent plasma of dimension l, mean magnetic field strength B, and mean number density n are considered. The electrons suffer radiative and ionization losses and have a scattering mean free path that increases linearly with their momentum. Analytic solutions for the steady-state electron energy spectra are presented. The spectra are characterized by an exponential cutoff above a given momentum determined by the synchrontron or the confinement time, depending on the physical characteristics of the accelerating region.
Bogdan, T. J.↗
Particle acceleration and MHD wave excitation upstream of interplanetary shocks
The theory of diffusive shock acceleration and its application in interplanetary space are reviewed. Special emphasis is placed on the distinction between diffusive and shock-drift shock acceleration, on ion-excitation of MHD waves upstream of the shock and the resulting self-consistent configuration of waves and accelerated ions, and on the mathematical theory of that configuration at quasi-parallel supercritical interplanetary travelling shocks. A comparison of predicted and observed proton anisotropies for the 12 November 1978 event is presented.
Lee, M. A.↗
Numerical studies of particle acceleration at turbulent, oblique shocks with an application to prompt ion acceleration during solar flares
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Decker, R. B.↗
Compositional changes, time and density variations in the magnetosphere associated with Birkeland currents and particle acceleration
Birkeland currents, parallel electric fields and plasma instabilities often occur together in time and space and play an important role in large scale plasma motions between the ionosphere and magnetosphere and along the magnetic field in the magnetosphere. The results of the plasma movements are large density and composition variations in the ionosphere and magnetosphere. Observations from ISIS-2 at 1400 km altitude show large densities with heavy ions dominating in regions with upward Birkeland currents, and low densities and light ions in regions with downward currents. Observations from ISEE-1 in field aligned current regions at 10,000 to 15,000 km altitude show transverse heating of protons and oxygen ions to 250 eV. Because of the different mobility of the protons and oxygen ions the proton flow is important in the beginning of the events but later the outflow becomes almost pure oxygen. Similarly ISEE-1 observations of outgoing field ion beams at 10,000 to 15,000 km altitude show time variations in the H+/O+ ratios and a dominance of O+ later in the events.
Ungstrup, E.↗
Solar radio bursts with special regard to particle acceleration and mass ejection
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Melrose, D. B.↗
Soft X-ray emissions, meter-wavelength radio bursts, and particle acceleration in solar flares
A detailed study of the relationship between metric radio bursts and soft X-ray flares has been made using an extensive data set covering 15 yr. It is found that type IV emission is mainly associated with long-duration 1-8 A events that are known to be well associated with coronal mass ejections. In contrast, type II and type III bursts originate primarily in impulsive soft X-ray events that are not necessarily accompanied by mass ejection. Strong type III bursts, in particular, appear to occur only in association with relatively impulsive flares. It is suggested that coronal shocks responsible for type II bursts are blast waves generated in impulsive energy releases.
Cane, H. V.↗
Particle acceleration in accreting magnetospheres
The possibility that energetic protons are accelerated within the closed magnetosphere of accelerating neutron stars is considered. The accelerating mechanism is suggested to be plasma turbulence excited by the accretion flow. Rough estimates show that this mechanism may be capable of accelerating protons to the energies of about 10 to the 16th eV required to explain observations of about 10 to the 15th eV gamma rays from some thermal X-ray sources. Proton synchrotron radiation may be observable at energies ranging from the infrared to about GeV gamma rays.
Katz, J. I.↗
Particles accelerated by shocks in the heliosphere
The populations of energetic ions accelerated by shocks in the heliosphere are reviewed briefly. Characteristic spectra and representative fluxes are given.
Lee, Martin A.↗
Current sheet interaction and particle acceleration in the Jovian magnetosphere
The thin, rapidly rotating current sheet in Jupiter's magnetodisk can energize heavy ions by hundreds of keV. If the magnetic field lines are azimuthally swept back, energetic ions undergoing nonadiabatic current sheet interactions will step radially outward and be centrifugally energized. Estimated energization times can be comparable to the Jovian rotation period. Nonadiabatic interactions with the rotating Jovian current sheet may be an important energization mechanism for heavy ions, but are not effective for energizing electrons or light ions like protons.
Cheng, Andrew F.↗