Outflow Formation Research Articles

Evaluation and verification of the WetSpa model based on selected rural catchments in Poland

Evaluation and verification of the WetSpa model based on selected rural catchments in Poland The paper presents results of calibration and verification of the WetSpa model, which enables the modelling of rainfall-runoff process based on mass and energy balance in the soil-plantatmosphere system in the catchment. It is a model with distributed parameters, using the structure of raster GIS model to determine the spatial diversity of the catchment environment. This enables simulation of runoff from the catchment, including: precipitation, evapotranspiration, interception of plant surface and soil cover, infiltration and capillary rise in soil and groundwater runoff. Simulated processes depend on the required non-distributed parameters, which were calibrated based on hydrometeorological data from the three rural catchments with different physical and geographical characteristics: Mławka, located in the Wkra basin in Central Poland and the rivers Kamienna and Sidra, which are tributaries of the upper Biebrza in north-eastern part of the country. Distributed catchment parameters were specified on the basis of digital soil maps, land use maps and digital elevation model using GIS techniques. Non-distributed model parameters were calibrated for the three catchments using automatic techniques based on the PEST algorithm. The obtained values of these parameters were scrutinized in order to analyse differences resulting from various characteristics of the study areas. The quality of the model was verified upon dependent and independent data. Appropriate quality measures, including Nash-Sutcliffe efficiency measure, were used to assess model quality. For two catchments (the Sidra and Kamienna) the model showed a satisfactory quality for modelling high flows, it was, however, not satisfactory for low flows. The values for the Mławka catchment justified the assessment of the model quality measurements as very good and good. The factors most affecting the process of river outflow formation were determined using the analysis of model sensitivity to relative changes in parameter values. It was found that the evaluation of the model quality depended largely on the quality of meteorological data and proper parameterization of the soil cover.

ACCELERATION AND COLLIMATION OF RELATIVISTIC MAGNETOHYDRODYNAMIC DISK WINDS

We perform axisymmetric relativistic magnetohydrodynamic (MHD) simulations to investigate the acceleration and collimation of jets and outflows from disks around compact objects. The fiducial disk surface (respectively a slow disk wind) is prescribed as boundary condition for the outflow. We apply this technique for the first time in the context of relativistic jets. The strength of this approach is that it allows us to run a parameter study in order to investigate how the accretion disk conditions govern the outflow formation. Our simulations using the PLUTO code run for 500 inner disk rotations and on a physical grid size of 100x200 inner disk radii. In general, we obtain collimated beams of mildly relativistic speed and mass-weighted half-opening angles of 3-7 degrees. When we increase the outflow Poynting flux by injecting an additional disk toroidal field into the inlet, Lorentz factors up to 6 are reached. These flows gain super-magnetosonic speed and remain Poynting flux dominated. The light surface of the outflow magnetosphere tends to align vertically - implying three relativistically distinct regimes in the flow - an inner sub-relativistic domain close to the jet axis, a (rather narrow) relativistic jet and a surrounding subrelativistic outflow launched from the outer disk surface - similar to the spine-sheath structure currently discussed for asymptotic jet propagation and stability. The outer subrelativistic disk wind is a promising candidate for the X-ray absorption winds that are observed in many radio-quiet AGN.

PROTOSTELLAR OUTFLOWS: NEW PERSPECTIVES ON MESOSCOPIC STRUCTURE AND MACROSCOPIC FEEDBACK

This paper presents a brief review of new perspectives in the field of protostellar outflows concentrating on scales above those associated with the launch region (L > 10 AU ). The formation and propagation of protostellar or Young Stellar Object (YSO) jets and collimated outflows has been intensively studied over the last 30 years with enormous progress being made in both theory and observations. As both the resolution and integration of observational platforms increases new features are revealed which have shifted the emphasis of research efforts. In this paper we review results in two different domains of YSO outflows research which focus on these new perspectives. We first review attempts to model jets as intrinsically heterogeneous (clumpy) systems. The role of sub-radial clumps (rc < rj) within a jet are explored and these models are differentiated from the classic paradigm of pulsed jets. In the second section we look at YSO jets in a global, environmental context. The ability of YSO jets and outflows to generate and/or sustain turbulence in star forming environments has been suggested as a major source of feedback in young clusters. Until recently this suggestion has been untested via direct simulations. We review new work on star formation outflow feedback and discuss issues for future studies.

Revealing the Mid‐Infrared Emission Structure of IRAS 16594−4656 and IRAS 07027−7934

TIMMI2 diffraction-limited mid-infrared images of a multipolar proto-planetary nebula IRAS 16594-4656 and a young [WC] elliptical planetary nebula IRAS 07027-7934 are presented. Their dust shells are for the first time resolved (only marginally in the case of IRAS 07027-7934) by applying the Lucy-Richardson deconvolution algorithm to the data, taken under exceptionally good seeing conditions (≤05). IRAS 16594-4656 exhibits a two-peaked morphology at 8.6, 11.5, and 11.7 μm, which is mainly attributed to emission from PAHs. Our observations suggest that the central star is surrounded by a toroidal structure, observed edge-on, with a radius of 04 (~640 AU at an assumed distance of 1.6 kpc) and with its polar axis at P.A. ~ 80°, coincident with the orientation defined by only one of the bipolar outflows identified in the HST optical images. We suggest that the material expelled from the central source is currently being collimated in this direction and that the multiple outflow formation has not been coeval. IRAS 07027-7934 shows a bright, marginally extended emission (FWHM = 03) in the mid-infrared with a slightly elongated shape along the north-south direction, consistent with the morphology detected by HST in the near-infrared. The mid-infrared emission is interpreted as the result of the combined contribution of small, highly ionized PAHs and relatively hot dust continuum. We propose that IRAS 07027-7934 may have recently experienced a thermal pulse (likely at the end of the AGB) which has produced a radical change in the chemistry of its central star.

Alignment of Outflows with Magnetic Fields in Cloud Cores

We estimate the polarized thermal dust emission from MHD simulations of protostellar collapse and outflow formation in order to investigate the alignment of outflows with magnetic fields. The polarization maps indicate that the alignment of an outflow with the magnetic field depends on the field strength inside the cloud core; the direction of the outflow, projected on the plane of the sky, is aligned preferentially with the mean polarization vector for a cloud core with a magnetic field strength of 80 μG, while it does not tend to be aligned for 50 μG as long as the 1000 AU scale is considered. The direction of the magnetic field at the cloud center is probed by the direction of the outflow. In addition, the magnetic field at the cloud center can be revealed by the Atacama Large Millimeter Array (ALMA) even when the source is embedded deeply in the envelope. The Chandrasekhar-Fermi formula is examined using the polarization maps, indicating that the field strength predicted by the formula should be corrected by a factor of 0.24-0.44. The correction factor has a tendency to be lower for a cloud core with a weaker magnetic field.

Directions of Outflows, Disks, Magnetic Fields, and Rotation of Young Stellar Objects in Collapsing Molecular Cloud Cores

The collapse of slowly rotating molecular cloud cores threaded by magnetic fields is investigated by high-resolution numerical simulation. Outflow formation in the collapsing cloud cores is also followed. In the models examined, the cloud core and parent cloud rotate rigidly and are initially threaded by a uniform magnetic field. The simulations show that the cloud core collapses along the magnetic field lines. The magnetic field in the dense region of the cloud core rotates faster than that of the parent cloud as a consequence of spin-up of the central region during the collapse. The cloud core exhibits significant precession of the rotation axis, magnetic field, and disk orientation, with precession highest in the models with low initial field strength (20 μG). Precession in models with initial fields of ~40 μG is suppressed by strong magnetic braking. Magnetic braking transfers angular momentum form the central region and acts more strongly on the component of angular momentum oriented perpendicular to the magnetic field. After the formation of an adiabatic core, outflow is ejected along the local magnetic field lines. Strong magnetic braking associated with the outflow causes the direction of angular momentum to converge with that of the local magnetic field, resulting in the convergence of the local magnetic field, angular momentum, outflow, and disk orientation by the outflow formation phase. The magnetic field of a young star is inclined at an angle of no more than 30° from that of the parent cloud at initial field strengths of ~20 μG, while at an initial field strength of ~40 μG, the magnetic field of the young star is well aligned with that of the parent cloud.

Self-gravitational collapse of a magnetized cloud core: high resolution simulations with three-dimensional MHD nested grid

We investigate self-gravitational collapse of magnetized molecular cloud cores and formation of the outflow. We employ a nested grid in order to resolve fine structures of protostar and outflow generation, of which size is as small as 1 AU, and to follow the whole structure of the molecular cloud core, of which radius reaches 0.1–1 pc, simultaneously. The nested grid allows us to follow the evolution of the cloud core with the high dynamic range of 10 5–10 6 in the spatial resolution. In this paper, we introduce implementations of the self-gravitational MHD nested grid code and show applications to early stages in star formation: gravitational collapse of cloud core, “first core” formation, and bipolar outflow ejection. In both cases of single and binary star formation, magnetic fields play important role in the outflow formation. The outflow region has extremely low beta regions of β=10 −6–10 −3, and our code shows no sign of numerical instability even in these low-beta regions.

Relativistic Outflow Magnetically Driven by Black Hole Rotation

In the universe, several kinds of relativistic jets have been discovered, and it is believed that they are formed by violent phenomena near black holes. Despite the advancement of observations and black hole physics, their acceleration mechanisms are still not understood. Here, using numerical simulations, we show that the relativistic outflow is formed spontaneously by the magnetic field very near the rapidly rotating black hole. Previous simulations showed electromagnetic energy emission and nonrelativistic outflow formation in the black hole magnetosphere, but actual relativistic outflows have not yet been obtained. The present simulation shows that magnetic flux tubes, oblique to the rotation axis across the black hole horizon, are twisted into the shape of screws and propel plasma around the black hole to the relativistic regime.

Collimated Outflow Formation via Binary Stars: Three‐Dimensional Simulations of Asymptotic Giant Branch Wind and Disk Wind Interactions

We present three-dimensional hydrodynamic simulations of the interaction of a slow from an asymptotic giant branch (AGB) star and a jet blown by an orbiting companion. The jet or collimated fast wind is assumed to originate from an accretion disk that forms via Bondi accretion of the AGB or Roche lobe overflow. We present two distinct regimes in the wind-jet interaction determined by the ratio of the AGB to jet momentum flux. Our results show that when the momentum flux overwhelms the flux in the jet, a more disordered outflow results with the jet assuming a corkscrew pattern and multiple shock structures driven into the AGB wind. In the opposite regime, the jet dominates and will drive a highly collimated, narrow-waisted outflow. We compare our results with scenarios described by Soker & Rappaport and extrapolate to the structures observed in planetary nebulae (PNs) and symbiotic stars.

A General Relativistic Magnetohydrodynamic Simulation of Outflow Formation around Rotating Black Hole

In the universe, several kinds of relativistic jets have been discovered, and it is believed they are formed by violent phenomena near black holes. Despite advancement of observations and black hole physics, their acceleration mechanisms are still mystery. Here we show that relativistic outflow is formed spontaneously by magnetic field near rapidly rotating black hole with numerical simulations. Previous simulations showed electromagnetic energy emission and non-relativistic out flow formation in the black hole magnetosphere, but actual relativistic outflows have not yet been obtained. Present simulation shows magnetic flux tubes oblique to the rotation axis across black hole horizon are twisted in the shape of screws and propel plasma around the black hole to relativistic regime'.

Trabecular Outflow Facility and Formation Rate of Aqueous Humor During Anesthesia with Sevoflurane-Nitrous Oxide or Sevoflurane-Remifentanil in Rabbits

Trabecular Outflow Facility and Formation Rate of Aqueous Humor During Anesthesia with Sevoflurane-Nitrous Oxide or Sevoflurane-Remifentanil in Rabbits

A Study of the Mutual Interaction between the Monoceros R2 Outflow and Its Surrounding Core

We present high-resolution (12''-24'')12CO(J = 2-1),13CO(2-1), CS(2-1), CS(3-2), and CS(5-4) maps of the central 4' × 4' of Mon R2 and study the bipolar outflow, the dense core, and their mutual interaction. The high-velocity 12CO and 13CO emissions that trace the bipolar outflow show that the outflow lobes are limb-brightened shells of accelerated gas that have the Mon R2 IR cluster near their apex and extend approximately toward the north and south. These shells of gas are clumpy, and their emission at the highest velocities arises from discrete condensations that move with the flow but each has a slightly different speed. The CS data, on the other hand, trace the ambient core at low velocities, but also trace the accelerated gas of the outflow at higher speeds. The ambient CS emission shows that the core has a cavity along the path of the outflow, and that the walls of this cavity coincide in position and orientation with the shells of the bipolar flow. The accelerated CS emission concentrates along the cavity walls and arises from the same clumpy shells of gas that form the outflow lobes in 12CO and 13CO. This outflow material, therefore, is rather dense, and a solution of the CS radiative transfer shows that it is as dense as the gas in the core (≈ 4 × 105 cm-3), suggesting that what we see as outflow is in fact gas from the dense core that has been set into motion. With the same radiative transfer analysis of the CS lines, we estimate that from a total of 1000 M☉ of dense gas in the core, more than 170 M☉ have been accelerated and incorporated into the bipolar flow. In addition, the CS spectra show a systematic enhancement of the line width toward the IR cluster that suggests the outflow has increased the gas turbulence in its vicinity. The amount of kinetic energy contained in both the bipolar and turbulent motions is comparable to the total binding energy of the dense gas, and this shows that the action of the outflow on the core can be strong enough to affect the distribution of dense gas in the core. We therefore propose that the cavity in the dense gas is the result of the evacuation of a channel by the outflow, and that the material initially filling its volume has been accelerated and incorporated into the flow. The Mon R2 system, therefore, illustrates how bipolar molecular outflows form through the acceleration of ambient molecular gas and that the process of molecular outflow formation is accompanied by a partial destruction of the dense gas environment of the newly formed star.

Trabecular outflow facility and formation rate of aqueous humor during intravenous cocaine or lidocaine in rabbits.

This study examined the effect of cocaine and lidocaine on intraocular pressure (IOP), fluid formation, outflow facility, and compliance. Fourteen New Zealand White rabbits were anesthetized with halothane (0.8-1.0% inspired concentration) in nitrous oxide (2 L/min) and oxygen (1 L/min). Pancuronium was given intravenously (i.v.) to produce neuromuscular block, and the lungs were mechanically ventilated through a tracheal tube. In one group (n = 8) cocaine 0.5 mg/kg followed by 1.0 microgram.kg-1.min-1 i.v. was added to halothane/nitrous oxide/oxygen anesthesia. In the second group (n = 6) lidocaine 0.5 mg/kg followed by 1.0 microgram.kg-1.min-1 i.v. was added to halothane/nitrous oxide/oxygen anesthesia. In both groups a series of intraocular infusions was made via a 30-gauge needle in the anterior chamber and IOP, the rate of aqueous humor formation, trabecular outflow facility, and intraocular compliance were determined. In Group I, IOP was 15.0 +/- 6.3 mmHg prior to and 14.5 +/- 7.1 mm Hg after cocaine. The rate of anterior chamber aqueous formation was 3.79 +/- 1.25 microL/min and trabecular outflow facility was 0.141 +/- 0.090 microL.min-1.mm Hg-1. In Group 2, IOP was 14.4 +/- 4.8 mm Hg prior to lidocaine and IOP decreased (P < 0.05 compared to precocaine in Group 1 and prelidocaine in Group 2) to 11.9 +/- 6.8 mm Hg after lidocaine. The rate of anterior chamber aqueous formation was 2.59 +/- 0.86 microL/min and trabecular outflow facility decreased (P < 0.05 compared to Group 1) to 0.077 +/- 0.040 microL.min-1.mm Hg-1. Intraocular compliance during cocaine, 36 +/- 12 nL/mm Hg, was similar to that during lidocaine, 33 +/- 14 nL/mm Hg.(ABSTRACT TRUNCATED AT 250 WORDS)

The cause of negative initial outflow with the Muskingum method

The cause of negative or reduced outflow formation at the beginning of a Muskingum solution is examined in two steps. The first step involves a physical interpretation of the Muskingum weighted discharge and the storage equation, using theory based on an extension of the Kalinin-Milyukov method. The second step involves the derivation of an analytical solution for the weighted discharge based on linear systems analysis theory, and then subsequently the Muskingum solution from that analytical solution using the assumption of linear variation of discharge within the reach. It is proved that this assumption causes the formation of negative or reduced outflow at the beginning of a Muskingum solution.

The cause of negative initial outflow with the Muskingum method

The cause of negative or reduced outflow formation at the beginning of a Muskingum solution is examined in two steps. The first step involves a physical interpretation of the Muskingum weighted discharge and the storage equation, using theory based on an extension of the Kalinin-Milyukov method. The second step involves the derivation of an analytical solution for the weighted discharge based on linear systems analysis theory, and then subsequently the Muskingum solution from that analytical solution using the assumption of linear variation of discharge within the reach. It is proved that this assumption causes the formation of negative or reduced outflow at the beginning of a Muskingum solution.

Perfusion studies on the monkey eye

A method of measuring facility of outflow and aqueous formation using constant pressure perfusion is described. Values obtained in normal Cynomolgus monkey eyes corresponded well with previous reports. Pilocarpine was found to cause a large increase in facility but also to cause a rise in episcleral venous pressure and an increase in aqueous production. Atropine had no detectable effect on the facility of outflow. Trabeculotomy in four eyes had little effect on facility of outflow, and following pilocarpine these eyes showed a similar increase in facility to that in normal eyes. The results are discussed in relation to the site of resistance to aqueous outflow in the monkey eye.