arXiv subjects

S. Mendoza

Publications and source records attributed to S. Mendoza.

46 records · Page 3Linked to original sources

arXiv2005

A possible hydrodynamical equivalence for astrophysical jets

The idea of a unified model for quasars and micro-quasars has been considered for a long time, despite the different environments and physical conditions where both classes of objects reside. Here we show the existence of a simple scaling law, relating the maximum size of a jet to the properties of the gas medium into which it expands. This appears to be valid for all types of hydrodynamical jets, and can be thought of as a broad unified model. The expansion velocity of the jet and the physical properties of the surrounding gas combine in such a way that a limit to the maximum extent of jets at different scales can be obtained.

astro-ph↗

arXiv2005

Hydrodynamical scaling laws for astrophysical jets

The idea of a unified model for all astrophysical jets has been considered for some time now. We present here some hydrodynamical scaling laws relevant for all type of astrophysical jets, analogous to those of Sams et al. (1996). We use Buckingham's Pi theorem of dimensional analysis to obtain a family of dimensional relations among the physical quantities associated with the jets.

astro-ph↗

arXiv2005

Relativistic solutions to the problem of jets with time-dependent injection velocities

We present a ballistic description of the propagation of the working surface of a relativistic jet. Using simple laws of conservation of mass and linear momentum at the working surface, we obtain a full description of the jet flow parametrised by the initial velocity and mass injection. This analysis will soon be applied to particular cases of time-dependent injection of mass and velocity into the jet.

astro-ph↗

arXiv2004

Possible cosmological implications in electrodynamics due to variations of the fine structure constant

Astronomical observations are suggesting that the fine structure constant varies cosmologically. We present an analysis on the consequences that these variations might induce on the electromagnetic field as a whole. We show that under these circumstances the electrodynamics in vacuum could be described by two fields, the ``standard'' Maxwell's field and a new scalar field. We provide a generalised Lorentz force which can be used to test our results experimentally.

astro-ph↗

arXiv2004

Ion Chambers for Monitoring the NuMI Neutrino Beam at FNAL

The Neutrinos at the Main Injector (NuMI) beamline will deliver an intense muon neutrino beam by focusing a beam of mesons into a long evacuated decay volume. The beam must be steered with 1 mRad angular accuracy toward the Soudan Underground Laboratory in northern Minnesota. We have built 4 arrays of ionization chambers to monitor the neutrino beam direction and quality. The arrays are located at 4 stations downstream of the decay volume, and measure the remnant hadron beam and tertiary muons produced along with neutrinos in meson decays. We review how the monitors will be used to make beam quality measurements, and as well we review chamber construction details, radiation damage testing, calibration, and test beam results.

physics.acc-ph↗

arXiv2004

Hydrodynamical interaction between an accretion flow and a stellar wind

Molecular clouds in the interstellar medium suffer gravitational instabilities that lead to the formation of one or multiple stars. A recently formed star inside a cold cloud communicates its gravitational force to the surrounding environment and soon an accretion flow falling into the star develops. After their formation, all stars soon eject a wind of gas that interacts with the external accretion flow. This interaction produces a shock wave that evolves with time. The work presented in this article formulates a simple prescription for the evolution of this interaction. With the aid of this model we construct a few radio continuum maps of the source.

astro-ph↗

arXiv2002

Formation of internal shock waves in bent jets

We discuss the circumstances under which the bending of a jet can generate an internal shock wave. The analysis is carried out for relativistic and non-relativistic astrophysical jets. The calculations are done by the method of characteristics for the case of steady simple waves. This generalises the non-relativistic treatment first used by Icke (1991). We show that it is possible to obtain an upper limit to the bending angle of a jet in order not to create a shock wave at the end of the curvature. This limiting angle has a value of 75 degrees for non-relativistic jets with a polytropic index k = 4/3, 135 degrees for non-relativistic jets with k = 5/3) and 50 degrees for relativistic jets with k = 5/3. We also discuss under which circumstances jets will form internal shock waves for smaller deflection angles.

astro-ph↗

arXiv2001

Hydrodynamical interaction between a shock wave and a cloud. One dimensional approach

The collision of a plane parallel shock wave with a plane parallel cloud of uniform density is analysed for the case in which magnetic fields and radiative losses are not considered. General analytic solutions are discussed for the case in which the density of the cloud is greater than that of the surrounding environment. This problem generalises one of the classical problems in gas dynamics: the collision between a shock wave and a solid wall.

physics.flu-dyn↗

arXiv2001

Deflection of Jets Induced by Jet-Cloud Interactions

A non--relativistic and relativistic model in which astrophysical jets are deflected on passing through an isothermal high density region is analysed. The criteria for the stability of jets due to the formation of internal shocks are discussed.

astro-ph↗

arXiv2001

Deflection of jets induced by jet-cloud & jet-galaxy interactions

The model first introduced by Raga & Canto (1996) in which astrophysical jets are deflected on passing through an isothermal high density region is generalised by taking into account gravitational effects on the motion of the jet as it crosses the high density cloud. The problem is also generalised for relativistic jets in which gravitational effects induced by the cloud are neglected. Two further cases, classical and relativistic, are discussed for the cases in which the jet is deflected on passing through the interstellar gas of a galaxy in which a dark matter halo dominates the gravitational potential. The criteria for the stability of jets due to the formation of internal shocks are discussed.

astro-ph↗