RadioAstron reveals a spine-sheath jet structure in 3C 273

AbstractThe gas evolution of a typical Dwarf Spheroidal Galaxy is investigated by means of 3D hydrodynamic simulations, taking into account the feedback of type II and Ia supernovae, the outflow of an Intermediate Massive Black Hole (IMBH) and a static cored dark matter potential. When the IMBH’s outflow is simulated in an homogeneous medium a jet structure is created and a small fraction of the gas is pushed away from the galaxy. No jet structure can be seen, however, when the medium is disturbed by supernovae, but gas is still pushed away. In this case, the main driver of the gas removal are the supernovae. The interplay between the stellar feedback and the IMBH’s outflow should be taken into account.

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Impact of scale, nuclear PDF and temperature variations on the interpretation of medium-modified jet production data from the LHC

Journal of High Energy Physics ◽

10.1007/jhep04(2021)006 ◽

2021 ◽

Vol 2021 (4) ◽

Author(s):

A. Andronic ◽

J. Honermann ◽

M. Klasen ◽

C. Klein-Bösing ◽

J. Salomon

Keyword(s):

Distribution Functions ◽

Production Data ◽

Crossover Temperature ◽

Parton Distribution Functions ◽

Temperature Variations ◽

Nuclear Modification Factor ◽

Nuclear Modification ◽

Modification Factor ◽

The Impact ◽

Jet Structure

Abstract In this paper we present a study of in-medium jet modifications performed with JEWEL and PYTHIA 6.4, focusing on the uncertainties related to variations of the perturbative scales and nuclear parton distribution functions (PDFs) and on the impact of the initial and crossover temperature variations of the medium. The simulations are compared to LHC data for the jet spectrum and the nuclear modification factor. We assess the interplay between the choice of nuclear PDFs and different medium parameters and study the impact of nuclear PDFs and the medium on the jet structure via the Lund plane.

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Mixing of an Acoustically Excited Air Jet With a Confined Hot Crossflow

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.2906306 ◽

1992 ◽

Vol 114 (1) ◽

pp. 46-54 ◽

Cited By ~ 28

Author(s):

P. J. Vermeulen ◽

P. Grabinski ◽

V. Ramesh

Keyword(s):

Strouhal Number ◽

Temperature Profiles ◽

Measured Temperature ◽

Mixing Zone ◽

Wake Region ◽

Mixing Processes ◽

Jet Mixing ◽

Air Jet ◽

Percent Increase ◽

Jet Structure

The mixing of an acoustically pulsed air jet with a confined hot crossflow has been assessed by temperature profile measurements. These novel experiments were designed to examine the effects of acoustic driver power and Strouhal number on jet structure, penetration, and mixing. The results showed that excitation produced strong changes in the measured temperature profiles. This resulted in significant increases in mixing zone size, penetration (at least 100 percent increase), and mixing, and the length to achieve a given mixed state was shortened by at least 70 percent. There was strong modification to the jet-wake region. The increase in jet penetration and mixing was saturating near 90 W, the largest driving power tested. The jet response as determined by penetration and mixing was optimum at a Strouhal number of 0.27. Overall, pulsating the jet flow significantly improved the jet mixing processes in a controllable manner.

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A Mechanism for the Effect of Tropospheric Jet Structure on the Annular Mode–Like Response to Stratospheric Forcing

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-11-0188.1 ◽

2012 ◽

Vol 69 (7) ◽

pp. 2152-2170 ◽

Cited By ~ 18

Author(s):

Isla R. Simpson ◽

Michael Blackburn ◽

Joanna D. Haigh

Keyword(s):

Momentum Flux ◽

General Circulation ◽

General Circulation Models ◽

Lower Latitude ◽

Mean Flow ◽

Zonal Winds ◽

Feedback Strength ◽

Poleward Shift ◽

Climate Forcings ◽

Jet Structure

Abstract For many climate forcings the dominant response of the extratropical circulation is a latitudinal shift of the tropospheric midlatitude jets. The magnitude of this response appears to depend on climatological jet latitude in general circulation models (GCMs): lower-latitude jets exhibit a larger shift. The reason for this latitude dependence is investigated for a particular forcing, heating of the equatorial stratosphere, which shifts the jet poleward. Spinup ensembles with a simplified GCM are used to examine the evolution of the response for five different jet structures. These differ in the latitude of the eddy-driven jet but have similar subtropical zonal winds. It is found that lower-latitude jets exhibit a larger response due to stronger tropospheric eddy–mean flow feedbacks. A dominant feedback responsible for enhancing the poleward shift is an enhanced equatorward refraction of the eddies, resulting in an increased momentum flux, poleward of the low-latitude critical line. The sensitivity of feedback strength to jet structure is associated with differences in the coherence of this behavior across the spectrum of eddy phase speeds. In the configurations used, the higher-latitude jets have a wider range of critical latitude locations. This reduces the coherence of the momentum flux anomalies associated with different phase speeds, with low phase speeds opposing the effect of high phase speeds. This suggests that, for a given subtropical zonal wind strength, the latitude of the eddy-driven jet affects the feedback through its influence on the width of the region of westerly winds and the range of critical latitudes on the equatorward flank of the jet.

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A Case Study of Observed and Modeled Barrier Flow in the Denmark Strait in May 2015

Monthly Weather Review ◽

10.1175/mwr-d-16-0386.1 ◽

2017 ◽

Vol 145 (6) ◽

pp. 2385-2404 ◽

Cited By ~ 8

Author(s):

Alice K. DuVivier ◽

John J. Cassano ◽

Steven Greco ◽

G. David Emmitt

Keyword(s):

Wrf Model ◽

Horizontal Resolution ◽

Surface Energy Budget ◽

Vertical Resolution ◽

Structure Comparison ◽

Denmark Strait ◽

Pbl Scheme ◽

Barrier Jets ◽

The Impact ◽

Jet Structure

Abstract Mesoscale barrier jets in the Denmark Strait are common in winter months and have the capability to influence open ocean convection. This paper presents the first detailed observational study of a summertime (21 May 2015) barrier wind event in the Denmark Strait using dropsondes and observations from an airborne Doppler wind lidar (DWL). The DWL profiles agree well with dropsonde observations and show a vertically narrow (~250–400 m) barrier jet of 23–28 m s−1 near the Greenland coast that broadens (~300–1000 m) and strengthens farther off coast. In addition, otherwise identical regional high-resolution Weather Research and Forecasting (WRF) Model simulations of the event are analyzed at four horizontal grid spacings (5, 10, 25, and 50 km), two vertical resolutions (40 and 60 levels), and two planetary boundary layer (PBL) parameterizations [Mellor–Yamada–Nakanishi–Niino, version 2.5 (MYNN2.5) and University of Washington (UW)] to determine what model configurations best simulate the observed jet structure. Comparison of the WRF simulations with wind observations from satellites, dropsondes, and the airborne DWL scans indicate that the combination of both high horizontal resolution (5 km) and vertical resolution (60 levels) best captures observed barrier jet structure and speeds as well as the observed cloud field, including some convective clouds. Both WRF PBL schemes produced reasonable barrier jets with the UW scheme slightly outperforming the MYNN2.5 scheme. However, further investigation at high horizontal and vertical resolution is needed to determine the impact of the WRF PBL scheme on surface energy budget terms, particularly in the high-latitude maritime environment around Greenland.

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THE PARABOLIC JET STRUCTURE IN M87 AS A MAGNETOHYDRODYNAMIC NOZZLE

The Astrophysical Journal ◽

10.1088/0004-637x/775/2/118 ◽

2013 ◽

Vol 775 (2) ◽

pp. 118 ◽

Cited By ~ 64

Author(s):

Masanori Nakamura ◽

Keiichi Asada

Keyword(s):

Jet Structure

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Austral Spring Stratospheric and Tropospheric Circulation Interannual Variability

Journal of Climate ◽

10.1175/2010jcli3418.1 ◽

2011 ◽

Vol 24 (11) ◽

pp. 2629-2647 ◽

Cited By ~ 7

Author(s):

Eduardo Andrés Agosta ◽

Pablo Osvaldo Canziani

Keyword(s):

Interannual Variability ◽

High Index ◽

Stationary Waves ◽

Energy Propagation ◽

Central Pacific ◽

Austral Spring ◽

Circulation Patterns ◽

Tropospheric Circulation ◽

Phase Variability ◽

Jet Structure

Abstract The relationship between the October (spring) total ozone column (TOC) midlatitude zonal asymmetry over the Southern Hemisphere (SH) and the stratospheric quasi-stationary wave 1 (QSW1) interannual phase variability is analyzed. Once contributions to the TOC from known global predictors, estimated with a multiregression model, are removed, the residual TOC interannual variability is observed to be dynamically coupled to the stratospheric QSW1 phase behavior. The stratospheric QSW1 interannual phase variability, when classified according to specifically designed indices, yields different circulation patterns in the troposphere and stratosphere. High (upper quartile) index values correspond to a westward rotation of the midlatitude ozone trough and the stratospheric QSW1 phase, while low (lower quartile) index values represent their eastward-rotated state. These values can be associated with statistically different tropospheric circulation patterns: a predominantly single poleward tropospheric jet structure for high index values and a predominantly double-jet structure for low index values. For the latter, there is a higher daily probability of double-jet occurrence in the troposphere and a stronger stratospheric jet. These jet structures and their daily behavior are supported by significant synoptic-scale activity anomalies over SH mid- to high latitudes as well as changes in tropospheric quasi-stationary waves 1–3. The wave activity flux (W flux) diagnosis shows the contribution of active quasi-stationary waves in the observed tropospheric anomalies associated with high and low index values. With low index values, the quasi-stationary waves lead to a self-sustaining state of the stratospheric–tropospheric coupled system. With high index values, the overall mid- to high latitude circulation is associated with wave energy propagation from the tropical central Pacific into higher latitudes. Thus, during the austral spring, there are interactions between the troposphere and stratosphere, leading to the locally well-defined upward and downward propagation of wave anomalies, that is, significant upper troposphere (UT)–lower stratosphere (LS) interactions can occur within a spring month itself.

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Polarization VLBI Observations of a Complete Sample of Northern BL Lacertae Objects

International Astronomical Union Colloquium ◽

10.1017/s0252921100045024 ◽

1998 ◽

Vol 164 ◽

pp. 165-166

Author(s):

A. B. Pushkarev ◽

D. C. Gabuzda

Keyword(s):

Magnetic Field ◽

Radio Emission ◽

Synchrotron Emission ◽

Complete Sample ◽

Bl Lacertae Objects ◽

Bl Lacertae ◽

Vlbi Observations ◽

Core Components ◽

Jet Structure ◽

The Magnetic Field

AbstractThe polarization electric vectors in the VLBI jets of BL Lacertae objects are typically aligned with the jet structure. If the jet radio emission is optically thin synchrotron emission, this implies that the magnetic field is perpendicular to the jet, usually interpreted as a signature of shocks. The distribution of polarization position angles in the VLBI core components appears to be bimodal, with the polarization angles either aligned with or perpendicular to the jet direction. In order to study the origin of this characteristic polarization structure, we have made VLBI polarization observations of all 34 sources in the Kühr and Schmidt sample of BL Lacertae objects.

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The limb-brightened jet of M87 down to the 7 Schwarzschild radii scale

Astronomy and Astrophysics ◽

10.1051/0004-6361/201832921 ◽

2018 ◽

Vol 616 ◽

pp. A188 ◽

Cited By ~ 29

Author(s):

J.-Y. Kim ◽

T. P. Krichbaum ◽

R.-S. Lu ◽

E. Ros ◽

U. Bach ◽

...

Keyword(s):

Brightness Temperature ◽

Angular Resolution ◽

Magnetic Energy ◽

Large Mass ◽

High Angular Resolution ◽

Data Sets ◽

Jet Formation ◽

Physical Conditions ◽

Self Similar ◽

Jet Structure

Messier 87 (M 87) is one of the nearest radio galaxies with a prominent jet extending from sub-pc to kpc scales. Because of its proximity and the large mass of its central black hole (BH), it is one of the best radio sources for the study of jet formation. We study the physical conditions near the jet base at projected separations from the BH of ~7–100 Schwarzschild radii (Rsch). Global mm-VLBI Array (GMVA) observations at 86 GHz (λ = 3.5 mm) provide an angular resolution of ~50 μas, which corresponds to a spatial resolution of only 7 Rsch and reach the small spatial scale. We use five GMVA data sets of M 87 obtained from 2004 to 2015 and present new high angular resolution VLBI maps at 86 GHz. In particular, we focus on the analysis of the brightness temperature, the jet ridge lines, and the ratio of jet to counter-jet. The imaging reveals a parabolically expanding limb-brightened jet which emanates from a resolved VLBI core of ~(8–13) Rsch in size. The observed brightness temperature of the core at any epoch is ~(1–3) × 1010 K, which is below the equipartition brightness temperature and suggests magnetic energy dominance at the jet base. We estimate the diameter of the jet at its base to be ~5 Rsch assuming a self-similar jet structure. This suggests that the sheath of the jet may be anchored in the very inner portion of the accretion disk. The image stacking reveals faint emission at the center of the edge-brightened jet on sub-pc scales. We discuss its physical implication within the context of the spine-sheath structure of the jet.

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