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Extrapolation of Three-dimensional Magnetic Field Structure in Flare-productive Active Regions with Different Initial Conditions
Shimizu, T.; Inoue, S.; Kawabata, Y.
Nonlinear force-free field (NLFFF) modeling has been extensively used as a tool to infer three-dimensional (3D) magnetic field structure. In this study, the dependency of the NLFFF calculation with respect to the initial guess of the 3D magnetic field is investigated. While major parts of the previous studies used the potential field as the initia…
Magnetohydrodynamic Modeling of the Solar Wind Key Parameters and Current Sheets in the Heliosphere: Radial and Solar Cycle Evolution
Malova, H. V.; Popov, V. Yu.; Petrukovich, A. A. +4 more
We develop an axisymmetric numerical MHD model that allows us to investigate the spatial characteristics of the interplanetary magnetic field (IMF) and key solar wind plasma parameters from 20 to 400 solar radii over all heliolatitudes. The study is aimed at an analysis of the evolution of the spatial structure of the heliosphere through the solar…
Turbulence Near the Venusian Bow Shock: Venus Express Observations
Zhang, T. L.; Vörös, Z.; Chen, Y. Q. +3 more
In terms of composition and size, Venus is an Earth-like planet without a global intrinsic magnetic field. The Venusian bow shock and magnetosheath, reaching only 10% of the size of the Earth, are formed from the interaction of the solar wind with the Venusian ionosphere. Energy injection from the solar wind to the Venusian space environment can b…
Automated detection of block falls in the north polar region of Mars
Oberst, J.; Hauber, E.; Gwinner, K. +1 more
We developed a change detection method for the identification of ice block falls using NASA's HiRISE images of the north polar scarps on Mars. Our method is based on a Support Vector Machine (SVM), trained using Histograms of Oriented Gradients (HOG), and blob detection. The SVM detects potential new blocks between a set of images; the blob detect…
A Retrograde Spin of the Black Hole in MAXI J1659-152
Méndez, Mariano; Vadawale, Santosh; Rout, Sandeep K.
We present the results of spectral analysis of the galactic black hole binary MAXI J1659-152 in the rising phase of the outburst that lasted for about 65 days starting on 2010 September 25. The presence of a broad Fe line, verified by Monte Carlo simulations, and coverage of a wide energy band by utilizing the combined spectral capabilities of XMM…
On Measuring Divergence for Magnetic Field Modeling
Leka, K. D.; Barnes, G.; Wheatland, M. S. +2 more
A physical magnetic field has a divergence of zero. Numerical error in constructing a model field and computing the divergence, however, introduces a finite divergence into these calculations. A popular metric for measuring divergence is the average fractional flux $\left\langle | {f}_{i}| \right\rangle $ . We show that $\left\langle | {f}_{i}| \r…
Determining quasar orientation
Yong, Suk Yee; Bate, Nicholas F.; Webster, Rachel L. +3 more
Since the discovery of active galactic nuclei (AGN) and their subclasses, a unification scheme of AGN has been long sought. Orientation-based unified models predict that some of the diversity within AGN subclasses can be explained by the different viewing angles of the observer. Several orientation categorizations have been suggested, but a widely…
X-raying molecular clouds with a short flare: probing statistics of gas density and velocity fields
Sunyaev, R.; Churazov, E.; Federrath, C. +3 more
We take advantage of a set of molecular cloud simulations to demonstrate a possibility to uncover statistical properties of the gas density and velocity fields using reflected emission of a short (with duration much less than the cloud's light-crossing time) X-ray flare. Such a situation is relevant for the Central Molecular Zone (CMZ) of our Gala…
Ultraviolet Line Identifications and Spectral Formation Near Max Light in Type Ia Supernova 2011fe
Baron, E.; Wang, Lifan; Branch, David +4 more
We present ultraviolet line identifications of near maximum-light Hubble Space Telescope observations of SN 2011fe using synthetic spectra generated from both SYNOW and PHOENIX. We find the spectrum to be dominated by blends of iron group elements Fe, Co, and Ni (as expected due to heavy line blanketing by these elements in the UV) and for the fir…
The dynamics of rings around Centaurs and Trans-Neptunian objects
Sicardy, Bruno; Leiva, Rodrigo; Roques, Françoise +4 more
Since 2013, dense and narrow rings are known around the small Centaur object Chariklo and the dwarf planet Haumea. Dense material has also been detected around the Centaur Chiron, although its nature is debated. This is the first time ever that rings are observed elsewhere than around the giant planets, suggesting that those features are more comm…