scholarly journals THE EFFECT OF LARGE-SCALE MAGNETIC TURBULENCE ON THE ACCELERATION OF ELECTRONS BY PERPENDICULAR COLLISIONLESS SHOCKS

2010 ◽  
Vol 715 (1) ◽  
pp. 406-411 ◽  
Author(s):  
Fan Guo ◽  
Joe Giacalone
Keyword(s):  
Large Scale ◽  
Collisionless Shocks ◽  
Magnetic Turbulence

scholarly journals Investigation of the strong turbulence in the geospace environment

2015 ◽  
Vol 13 ◽  
pp. 243-250
Author(s):  
O. Kharshiladze ◽  
K. Chargazia
Keyword(s):  
Large Scale ◽  
Good Description ◽  
Observation Data ◽  
Plasma Medium ◽  
Magnetic Turbulence ◽  
Transfer Processes ◽  
Power Spectral ◽  
Power Spectral Densities ◽  
Vortex Chain ◽  
Plasma Vortices

Abstract. Plasma vortices are often detected by spacecraft in the geospace (atmosphere, ionosphere, magnetosphere) environment, for instance in the magnetosheath and in the magnetotail region. Large scale vortices may correspond to the injection scale of turbulence, so that understanding their origin is important for understanding the energy transfer processes in the geospace environment. In a recent work, turbulent state of plasma medium (especially, ionosphere) is overviewed. Experimental observation data from THEMIS mission (Keiling et al., 2009) is investigated and numerical simulations are carried out. By analyzing the THEMIS data for that event, we find that several vortices in the magnetotail are detected together with the main one and these vortices constitute a vortex chain. Such vortices can cause the strong turbulent state in the different media. The strong magnetic turbulence is investigated in the ionsophere as an ensemble of such strongly localized (weakly interacting) vortices. Characteristics of power spectral densities are estimated for the observed and analytical stationary dipole structures. These characteristics give good description of the vortex structures.

scholarly journals Competitive X-Ray and Optical Cooling in the Collisionless Shocks of WR 140

2021 ◽  
Vol 923 (2) ◽  
pp. 191
Author(s):  
A. M. T. Pollock ◽  
M. F. Corcoran ◽  
I. R. Stevens ◽  
C. M. P. Russell ◽  
K. Hamaguchi ◽  
...  
Keyword(s):  
Large Scale ◽  
Optical Emission ◽  
Collisionless Shocks ◽  
X Ray ◽  
Band Emission ◽  
Optical Cooling ◽  
Estimate Mass Loss ◽  
Star Binary ◽  
X Ray Absorption ◽  
Rayet Star

Abstract The long-period, highly eccentric Wolf-Rayet star binary system WR 140 has exceptionally well-determined orbital and stellar parameters. Bright, variable X-ray emission is generated in shocks produced by the collision of the winds of the WC7pd+O5.5fc component stars. We discuss the variations in the context of the colliding-wind model using broadband spectrometry from the RXTE, Swift, and NICER observatories obtained over 20 yr and nearly 1000 observations through three consecutive 7.94 yr orbits, including three periastron passages. The X-ray luminosity varies as expected with the inverse of the stellar separation over most of the orbit; departures near periastron are produced when cooling shifts to excess optical emission in C iii λ5696 in particular. We use X-ray absorption to estimate mass-loss rates for both stars and to constrain the system morphology. The absorption maximum coincides closely with the inferior conjunction of the WC star and provides evidence of the ion-reflection mechanism that underlies the formation of collisionless shocks governed by magnetic fields probably generated by the Weibel instability. Comparisons with K-band emission and He i λ10830 absorption show that both are correlated after periastron with the asymmetric X-ray absorption. Dust appears within a few days of periastron, suggesting formation within shocked gas near the stagnation point. The X-ray flares seen in η Car have not occurred in WR 140, suggesting the absence of large-scale wind inhomogeneities. Relatively constant soft emission revealed during the X-ray minimum is probably not from recombining plasma entrained in outflowing shocked gas.

scholarly journals Generation and decay of the magnetic field in collisionless shocks

2016 ◽  
Vol 12 (S324) ◽  
pp. 62-65
Author(s):  
Mikhail Garasev ◽  
Evgeny Derishev
Keyword(s):  
Magnetic Field ◽  
Large Scale ◽  
Field Energy ◽  
Magnetic Field Generation ◽  
Collisionless Shocks ◽  
Particle In Cell ◽  
Magnetic Field Energy ◽  
Relativistic Shocks ◽  
Continuous Injection ◽  
The Magnetic Field

AbstractWe present the results of numerical particle-in-cell (PIC) simulations of the magnetic field generation and decay in the upstream of collisionless shocks. We use the model, where the magnetic field in the incoming flow is generated by continuous injection of anisotropic electron-positron pairs. We found that the continuous injection of anisotropic plasma in the upstream of the shock-wave generates the large-scale, slowly decaying magnetic field that is later amplified during the passage of the shock front. In our simulations the magnetic field energy reached ~0.01 of the equipartition value, after that it slowly decays on the time scale proportional to the duration of the injection in the upstream. Thus, the magnetic field survives for a sufficiently long time, and supports efficient synchrotron radiation from relativistic shocks, e.g., in GRBs.

Some comments about observations and image processing of comet 29P/Schwassmann-Wachmann 1

1999 ◽  
Vol 173 ◽  
pp. 243-248
Author(s):  
D. Kubáček ◽  
A. Galád ◽  
A. Pravda
Keyword(s):  
Image Processing ◽  
Large Scale ◽  
Harvard College ◽  
Oak Ridge ◽  
Large Scale Structures ◽  
Short Period Comet ◽  
Short Period ◽  
Scale Structures ◽  
Harvard College Observatory ◽  
Period Comet

AbstractUnusual short-period comet 29P/Schwassmann-Wachmann 1 inspired many observers to explain its unpredictable outbursts. In this paper large scale structures and features from the inner part of the coma in time periods around outbursts are studied. CCD images were taken at Whipple Observatory, Mt. Hopkins, in 1989 and at Astronomical Observatory, Modra, from 1995 to 1998. Photographic plates of the comet were taken at Harvard College Observatory, Oak Ridge, from 1974 to 1982. The latter were digitized at first to apply the same techniques of image processing for optimizing the visibility of features in the coma during outbursts. Outbursts and coma structures show various shapes.

Evolution of Large-Scale Coronal Structures

1994 ◽  
Vol 144 ◽  
pp. 29-33
Author(s):  
P. Ambrož
Keyword(s):  
Magnetic Field ◽  
Field Line ◽  
Large Scale ◽  
Coronal Magnetic Field ◽  
Source Surface ◽  
Solar Cycles ◽  
Characteristic Relationship ◽  
The Magnetic Field ◽  
Coronal Structures

AbstractThe large-scale coronal structures observed during the sporadically visible solar eclipses were compared with the numerically extrapolated field-line structures of coronal magnetic field. A characteristic relationship between the observed structures of coronal plasma and the magnetic field line configurations was determined. The long-term evolution of large scale coronal structures inferred from photospheric magnetic observations in the course of 11- and 22-year solar cycles is described.Some known parameters, such as the source surface radius, or coronal rotation rate are discussed and actually interpreted. A relation between the large-scale photospheric magnetic field evolution and the coronal structure rearrangement is demonstrated.

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