Astronomy & Astrophysics

The Standing Wave Phenomenon in Radio Telescopes; Frequency Modulation of the WSRT Primary Beam

by Attila Popping

The Simulated HI Sky at low redshift

by Attila Popping

The WSRT Virgo Hi filament survey II; Cross Correlation Data

by Attila Popping

The WSRT Virgo HI filament survey I; Total Power Data

by Attila Popping

Diffuse neutral hydrogen in the HI Parkes All Sky Survey

by Attila Popping

Molecular Gas in Intermediate Redshift ULIRGs

by Attila Popping

Basic Testing of the Duchamp Source Finder

by Attila Popping

Observable Signatures of the low-z Circum-Galactic and Inter-Galactic Medium : UV Line Emission in Simulations

by Attila Popping

Comparison of potential ASKAP HI survey source finders

by Attila Popping

Multidimensionale Universen

by Hans-Peter Keiseler

veröffentlicht in diversen Zeitungen, Mai 2012

Multidimensionale Universen

by Hans-Peter Keiseler

veröffentlicht in diversen Zeitungen, Mai 2012

Multidimensionale Universen

by Hans-Peter Keiseler

veröffentlicht in diversen Zeitungen, Mai 2012

Near‐Infrared Imaging Spectrophotometry of the Gravitational Mirage Q2237+0305

by Geneviève Arboit

Dead Zones around Young Stellar Objects: FU Orionis Outbursts and Transition Discs

by Rebecca G. Martin

Rebecca G. Martin, Stephen H. Lubow, Mario Livio, J. E. Pringle, 2012, MNRAS, accepted

We perform global time-dependent simulations of an accretion disc around a young stellar object with a dead zone (a... more We perform global time-dependent simulations of an accretion disc around a young stellar object with a dead zone (a region where the magneto-rotational instability cannot drive turbulence because the material is not sufficiently ionised). For infall accretion rates on to the disc of around 10^-7 Msun/yr, dead zones occur if the critical magnetic Reynolds number is larger than about 10^4. We model the collapse of a molecular gas cloud. At early times when the infall accretion rate is high, the disc is thermally ionised and fully turbulent. However, as the infall accretion rate drops, a dead zone may form if the critical magnetic Reynolds number is sufficiently large, otherwise the disc remains fully turbulent. With a dead zone the disc can become unstable to the gravo-magneto instability. The mass of the star grows in large accretion outbursts that may explain FU Orionis events. At late times there is not sufficient mass in the disc for outbursts to occur but the dead zone becomes even more prominent as the disc cools. Large inner dead zones in the later stages of disc evolution may help to explain observations of transition discs with an inner hole.

Interplanetary Evolution of fast Coronal Mass Ejections, Shocks and Type II Radio Bursts emission

by Pedro Corona-Romero

Co-authored with J. A. GONZALEZ-ESPARZA, E. AGUILAR-RODRIGUEZ. In revision in Solar Physics

Fast CMEs driving interplanetary shocks are one of the most important space weather phenomena. We present an analytic... more Fast CMEs driving interplanetary shocks are one of the most important space weather phenomena. We present an analytic model to study the evolution of these events in the interplanetary medium. The model shows that the CME/shock evolution is constituted by three phases: 1) driving, 2) decoupling; and 3) decaying. We compare the model's predictions with some study cases using coronograph, type II radio burst emissions and in-situ data. We found a good agreement between the model and the observational data. The model reproduces the shock-ICME evolution and the type II drift spectra.

A stationary bow shock model for plasmas: the spherical blunt obstacle problem

by Pedro Corona-Romero

Co-authored with J.A. Gonzalez-Esparza. In revision in Advances in Space Research.

We present an analytic model of stationary bow shock which describes the interaction between a supermagnetosonic... more We present an analytic model of stationary bow shock which describes the interaction between a supermagnetosonic ambient wind and an obstacle with spherical-like frontal shape. We develop expressions for the bow shocks geometry and the physical properties of the plasma sheath as functions of the upstream conditions. The model allows to use any value of the upstream Mach number and the polytropic index. The solution is limited to axisymmetric magnetic fields. The model points out the influence of the politropic index for the magnetosheath compression and the sbow shock shape. If the Mach number is small the upstream magnetic field orientation can affect the bow shock shape. We compare our results with other models and with in-situ data. By comparing our solution with observational data point we find a reasonable qualitative agreement; however, it seems that our model underestimates the magnetosheath size.

Dynamics of Coronal Mass Ejections in the interplanetary medium: an analytic perspective

by Pedro Corona-Romero

Co-authored with J.A. Gonzalez-Esparza. Draft in preparation for Journal of Geophysical Research.

We present a study about the posible forces, according the magnetohidrodynamics theory, goberning the propagation of... more We present a study about the posible forces, according the magnetohidrodynamics theory, goberning the propagation of coronal mass ejections (CMEs) along their propagation thorugh interplanetary (IP) medium. Such forces arise from the interaction between the CME and the ambient solar wind (SW). We also compare and discuss of some analytic approches to modeling the CME-SW dynamic coupling.

Dynamic evolution of Interplanetary Shock Waves driven by CMEs

by Pedro Corona-Romero

Co-authored with J.A. Gonzalez-Esparza. Proceedings IAU Symposium No. 286, 2011.

We present a study about the propagation of interplanetary shock waves driven by super magnetosonic coronal mass... more We present a study about the propagation of interplanetary shock waves driven by super magnetosonic coronal mass ejections (CMEs). The discussion focus on a model which discribes the dynamic relationship between the CME and its driven shock and the way to approximate the trajectory of shocks based on those relationships from near the Sun to 1 AU. We apply the model in the analysis of a study case, in which our calculations show quantitative and cualitative agreements with different kind of data. We discuss the importance of solar wind and CME initial conditions on the shock wave evolution.

Aristotele, De caelo - Giordano Bruno, De l'Infinito: confronto e commento.

by Stefano Ulliana

Pi ist genau 3 - Veränderung von Naturkonstanten

by Hans-Peter Keiseler

veröffentlicht in diversen Zeitungen in Deutschland, März 2012