Iranian Journal of Astronomy and AstrophysicsIranian Journal of Astronomy and Astrophysics
http://ijaa.du.ac.ir/
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http://ijaa.du.ac.ir/
Feed provided by Iranian Journal of Astronomy and Astrophysics. Click to visit.Large amplitude dust ion acoustic solitons: considering dust polarity and nonextensive electrons
http://ijaa.du.ac.ir/article_145_31.html
The characteristics of arbitrary amplitude dust ion acoustic solitary waves (DIASWs) are studied in unmagnetized dusty plasmas whose constituents are cold uid ions, nonextensive electrons and stationary negative/positive dust particles. The pseudopotential approach has been used to investigate the structure of localized waves. It is found that, solitary waves exist in a definite interval for the Mach number which depends sensitively to the electron nonextensivity and dust polarity. Our results can be useful to understand the properties of localized electrostatic disturbances that may occur in astrophysical and space dusty plasmas. Sun, 30 Sep 2018 20:30:00 +0100Resonant Absorption of a Solar Coronal Loop Observed by SDO/AIA
http://ijaa.du.ac.ir/article_147_31.html
Solar coronal loops represent variety of fast, intermediate, and slow normal mode oscillations. In this study, the transverse oscillations of a coronal loop observed on 11 October, 2013 are analyzed using the Extreme Ultra-Violet (EUV) images of the Sun. Employing the 171 AA solar images recorded by the Solar Dynamic Observatory (SDO)/Atmospheric Imaging Assembly (AIA), we extracted the oscillation parameters such as period, damping time, loop length, and the loop width. The period and the damping of this loop are obtained to be 19 ± 1 and 70 ± 1 minutes, respectively. Also, the damping quality, the ratio of the damping time to the period, is obtained to be 3.6. Therefore, we conclude that the damping of the transverse oscillation of this loop is in the strong damping regime. It is suggested that the resonant absorption would be a well suitable candidate for the damping mechanism of the studied loop.Sun, 30 Sep 2018 20:30:00 +0100Spining Magnetic Brane of Quartic Quasi-Topological Gravity in the Presence of Nonlinear ...
http://ijaa.du.ac.ir/article_148_31.html
In this paper, we obtain a new class of $(n+1)$-dimensional magnetic brane solutions of quasi-topological gravity in the presence of exponential and logarithmic nonlinear electrodynamics by a spinning magnetic branes with one or more rotation parameters. For the spinning brane, the brane has a net electric charge, when one or more rotation are non zero, and also this electric charge is proportional to the magnitude of the rotation parameter. However, when all the rotation parameters are zero (static brane), the electric field vanishes and the brane has no net electric charge. In the class of solutions, we have a spacetime with an angular magnetic field. These solutions are horizonless and have no curvature, but there is a conic singularity with a deficit angle. In addition, these two forms of nonlinear electrodynamics theory, have the same behaviors for the obtained solutions. Finally, we use the counterterm method and compute conserved quantities of these spacetimes.Sun, 30 Sep 2018 20:30:00 +0100