7.6 Today´s new entry:
Reconstruction of a helical prominence in 3D from IRIS spectra and images
B. Schmieder, M. Zapiór, A. López Ariste, P. Levens, N. Labrosse, R. Gravet
Context: Movies of prominences obtained by space instruments e.g. the Solar Optical Telescope (SOT) aboard the Hinode satellite and the Interface Region Imaging Spectrograph (IRIS) with high temporal and spatial resolution revealed the tremendous dynamical nature of prominences. Knots of plasma belonging to prominences appear to travel along both vertical and horizontal thread-like loops, with highly dynamical nature.
Aims: The aim of the paper is to reconstruct the 3D shape of a helical prominence observed over two and a half hours by IRIS.
Methods: From the IRIS Mg ii k spectra we compute Doppler shifts of the plasma inside the prominence and from the slit-jaw images (SJI) we derive the transverse field in the plane of the sky. Finally we obtain the velocity vector field of the knots in 3D.
Results: We reconstruct the real trajectories of nine knots travelling along ellipses.
Conclusions: The spiral-like structure of the prominence observed in the plane of the sky is mainly due to the projection effect of long arches of threads (up to 8 × 10e4 km). Knots run along more or less horizontal threads with velocities reaching 65 km/s. The dominant driving force is the gas pressure.
Journal: Astronomy & Astrophysics, accepted for publication
URL: Download preprint
Submitted by: Maciej Zapiór
7.5 Today´s new entry:
Hybrid polygon and hydrodynamic nebula modeling with multi-waveband radiation transfer in astrophysics
Wolfgang Steffen & Nico Koning
Abstract: We demonstrate the potential for research and outreach of mixed polygon and hydrodynamic modeling and multi-waveband rendering in the interactive 3-D astrophysical virtual laboratory Shape. In 3-D special effects and animation software for the mass media, computer graphics techniques that mix polygon and numerical hydrodynamics have become commonplace. In astrophysics, however, interactive modeling with polygon structures has only become available with the software Shape. Numerical hydrodynamic simulations and their visualization are usually separate, while in Shape it is integrated with the polygon modeling approach that requires no programming by the user. With two generic examples, we demonstrate that research and outreach modeling can be achieved with techniques similar to those used in the media industry with the added capability for physical rendering at any wavelength band, yielding more realistic radiation modeling. Furthermore, we show how the hydrodynamics and the polygon mesh modeling can be mixed to achieve results that are superior to those obtained using either one of these modeling techniques alone.
Journal: Astronomy and Computing, in press
Comments: download accompanying mpeg movie here
URL: Download preprint
Submitted by: W. Steffen
The other day I overheard a discussion between me and myself about pigeons. It was more about what their eyes and brains see when they walk back and forth picking up breadcrumbs that little kids and their granddads throw on the ground in front of a park bench. We have all seen it, haven´t we?
It´s like a discussion in stereo, you and yourself take a slightly different angle on a subject and discuss it vigorously in your head. The result is a confusing, but a slightly more complete picture of the matter. Continue reading