Individual Jets Research Articles

Modeling the Emission from Turbulent Relativistic Jets in Active Galactic Nuclei

We present a numerical model developed to calculate observed fluxes of relativistic jets in active galactic nuclei. The observed flux of each turbulent eddy is dependent upon its variable Doppler boosting factor, computed as a function of the relativistic sum of the individual eddy and bulk jet velocities and our viewing angle to the jet. The total observed flux is found by integrating the radiation from the eddies over the turbulent spectrum. We consider jets that contain turbulent eddies that have either standard Kolmogorov or recently derived relativistic turbulence spectra. We also account for the time delays in receiving the emission of the eddies due to their different simulated positions in the jet, as well as due to the varying beaming directions as they turn over. We examine these theoretical light curves and compute power spectral densities (PSDs) for a range of viewing angles, bulk velocities of the jet, and turbulent velocities. These PSD slopes depend significantly on the turbulent velocity and are essentially independent of viewing angle and bulk velocity. The flux variations produced in the simulations for realistic values of the parameters tested are consistent with the types of variations observed in radio-loud AGN as, for example, recently measured with the Kepler satellite, as long as the turbulent velocities are not too high.

A simple climatology of westerly jet streams in global reanalysis datasets part 1: mid-latitude upper tropospheric jets

A simple closed contour object identification scheme has been applied to the zonal mean monthly mean zonal wind fields from nine global reanalysis data sets for 31 years of the satellite era (1979–2009) to identify objects corresponding to westerly jet streams. The results cluster naturally into six individual jet streams but only the mid-latitude upper-tropospheric jets are considered here. The time series of the jet properties from all reanalyses are decomposed into seasonal means and anomalies, and correlations between variables are evaluated, with the aim of identifying robust features which can form the basis of evaluation metrics for climate model simulations of the twentieth century. There is substantial agreement between all the reanalyses for all jet properties although there are some systematic differences with particular data sets. Some of the results from the object identification applied to the reanalyses are used in a simple example of a model evaluation score for the zonal mean jet seasonal cycle.

Pulse-frequency modulated guidance laws for a mortar missile with a pulse jet control mechanism

AbstractThe impact point dispersion of mortar missiles can be drastically reduced with a control ring of lateral pulse jets located around the centre of gravity and a homing head to measure or to derive estimates of appropriate missile-target states, e.g. the line-of-sight rates. A simulation model including a missile as a six-degree-of-freedom vehicle, a jet pulse flight control system, and a relative missile-to-target motion was used for the comparison of four guidance laws i.e. proportional navigation guidance, augmented proportional navigation, augmented proportional navigation with rendezvous, and adaptive sliding-mode guidance. This paper focuses on the efficiency of pulse jet control on miss distance, and thus makes the assumption that sensor measurements and the guidance states required to apply each of the guidance laws are perfectly known. Proportional navigation and the adaptive sliding mode guidance exhibit a large miss distance due to limited control authority. Augmented proportional navigation is slightly better than augmented proportional navigation with rendezvous for the same design parameters and they both give small miss distances with limited control authority, but they both require a free gyro. A proper selection of the design parameters — the number of pulse jets and the magnitude of the individual pulse jet thrust for a particular dispersion of flight parameters and the instant of the guidance start — is required to achieve optimum dispersion reduction. The minimum intensity of the individual pulse jet impulse required for the ‘pin point’ accuracy (the circular error probable smaller than 1m) of the mortar missile was determined for all presented guidance laws considering dispersion from the nominal trajectory.

The SS433 jet from subparsec to parsec scales

Context. Relativistic jets associated with compact objects, as in the X-ray binary SS433, are known to be multiscale because they spawn over many orders of magnitude in distance. Here we model the precessing SS433 jet and study its dynamics from 𝒪 (0.01) to 𝒪(1) parsec scales.Aims. We aim to solve the discrepancy between the observations on a 0.1 pc scale of SS433, where the jet is clearly precessing with an angle of 20°, and the larger scale observations where the jet of SS433 interacts with the associated supernova remnant W50, requiring a precessing angle of 10°. Methods. We use 3D special relativistic hydrodynamical simulations on a domain of a scale of 1 pc. We use the finite volume code MPI-AMRVAC, solving the relativistic variant of the Euler equations. To cover lengthscale variations from 𝒪(0.001) pc as the jet beam width up to the domain size, we take full advantage of code parallelization and its adaptive mesh refinement scheme.Results. We found that by means of a simple hydrodynamical process, the jet of SS433 can transit from a precessing jet with an angle of 20°, to a continuous hollow non-precessing jet with a smaller opening angle of about 10°. Successive windings of the precessing jet helix undergo gradual deceleration by ISM interaction, to ultimately merge in a hollow straight jet at distances where the ram pressure of individual jet elements match the ISM pressure at about 0.068 pc from the source.Conclusions. We solve the discrepancy with an elegant and simple model that does not require the jet of SS433 to undergo any temporal changes in jet injection dynamics, but does so as a consequence of a hydrodynamically enforced spatial recollimation. Our simulation thus serves to validate simpler model prescriptions for SS433 on large scales, where a continuous jet profile suffices.

SoftKiller, a particle-level pileup removal method.

Existing widely used pileup removal approaches correct the momenta of individual jets. In this article we introduce an event-level, particle-based pileup correction procedure, SoftKiller. It removes the softest particles in an event, up to a transverse momentum threshold that is determined dynamically on an event-by-event basis. In simulations, this simple procedure appears to be reasonably robust and brings superior jet resolution performance compared to existing jet-based approaches. It is also nearly two orders of magnitude faster than methods based on jet areas.

MOJAVE. XII. ACCELERATION AND COLLIMATION OF BLAZAR JETS ON PARSEC SCALES

We report on the acceleration properties of 329 features in 95 blazar jets from the MOJAVE VLBA program. Nearly half the features and three-quarters of the jets show significant changes in speed and/or direction. In general, apparent speed changes are distinctly larger than changes in direction, indicating that changes in the Lorentz factors of jet features dominate the observed speed changes rather than bends along the line of sight. Observed accelerations tend to increase the speed of features near the jet base, $\lesssim 10-20$ parsecs projected, and decrease their speed at longer distances. The range of apparent speeds at fixed distance in an individual jet can span a factor of a few, indicating that shock properties and geometry may influence the apparent motions; however, we suggest that the broad trend of jet features increasing their speed near the origin is due to an overall acceleration of the jet flow out to de-projected distances of order $10^2$ parsecs, beyond which the flow begins to decelerate or remains nearly constant in speed. We estimate intrinsic rates of change of the Lorentz factors in the galaxy frame of order $\dot{\Gamma}/\Gamma \simeq 10^{-3}$ to $10^{-2}$ per year which can lead to total Lorentz factor changes of a factor of a few on the length scales observed here. Finally, we also find evidence for jet collimation at projected distances of $\lesssim 10$ parsecs in the form of the non-radial motion and bending accelerations that tend to better align features with the inner jet.

INTRINSIC BRIGHTNESS TEMPERATURES OF COMPACT RADIO JETS AS A FUNCTION OF FREQUENCY

We present results of our investigation of the radio intrinsic brightness temperatures of compact radio jets. The intrinsic brightness temperatures of about 100 compact radio jets at 2, 5, 8, 15, and 86 GHz are estimated based on large VLBI surveys conducted in 2001-2003 (or in 1996 for the 5 GHz sample). The multi-frequency intrinsic brightness temperatures of the sample of jets are determined by a statistical method relating the observed brightness temperatures with the maximal apparent jet speeds, assuming one representative intrinsic brightness temperature for a sample of jets at each observing frequency. By investigating the observed brightness temperatures at 15 GHz in multiple epochs, we find that the determination of the intrinsic brightness temperature for our sample is affected by the flux density variability of individual jets at time scales of a few years. This implies that it is important to use contemporaneous VLBI observations for the multi-frequency analysis of intrinsic brightness temperatures. Since our analysis is based on the VLBI observations conducted in 2001-2003, the results are not strongly affected by the flux density variability. We find that the intrinsic brightness temperature <TEX>$T_0$</TEX> increases as <TEX>$T_0{\propto}{\nu}^{\xi}_{obs}$</TEX> with <TEX>${\xi}=0.7$</TEX> below a critical frequency <TEX>${\nu}_c{\approx}9GHz$</TEX> where the energy loss begins to dominate the emission. Above <TEX>${\nu}_c$</TEX>, <TEX>$T_0$</TEX> decreases with <TEX>${\xi}=-1.2$</TEX>, supporting the decelerating jet model or particle cascade model. We also find that the peak value of <TEX>$T_0{\approx}3.4{\times}10^{10}$</TEX> K is close to the equipartition temperature, implying that the VLBI cores observable at 2-86 GHz may be representing jet regions where the magnetic field energy dominates the total energy in jets.

The flow structure of jets from transient sources and implications for modeling short‐duration explosive volcanic eruptions

AbstractWe used laboratory experiments to examine the rise process in neutrally buoyant jets that resulted from an unsteady supply of momentum, a condition that defines plumes from discrete Vulcanian and Strombolian‐style eruptions. We simultaneously measured the analog‐jet discharge rate (the supply rate of momentum) and the analog‐jet internal velocity distribution (a consequence of momentum transport and dilution). Then, we examined the changes in the analog‐jet velocity distribution over time to assess the impact of the supply‐rate variations on the momentum‐driven rise dynamics. We found that the analog‐jet velocity distribution changes significantly and quickly as the supply rate varied, such that the whole‐field distribution at any instant differed considerably from the time average. We also found that entrainment varied in space and over time with instantaneous entrainment coefficient values ranging from 0 to 0.93 in an individual unsteady jet. Consequently, we conclude that supply‐rate variations exert first‐order control over jet dynamics, and therefore cannot be neglected in models without compromising their capability to predict large‐scale eruption behavior. These findings emphasize the fundamental differences between unsteady and steady jet dynamics, and show clearly that: (i) variations in source momentum flux directly control the dynamics of the resulting flow; (ii) impulsive flows driven by sources of varying flux cannot reasonably be approximated by quasi‐steady flow models. New modeling approaches capable of describing the time‐dependent properties of transient volcanic eruption plumes are needed before their trajectory, dilution, and stability can be reliably computed for hazards management.

Abstract 20132: Quantification of Multiple Mitral Regurgitant Jets: An in vitro Assessment of Doppler Methods Pertaining to MitraClip

Introduction: Mitraclip deployment creates a double orifice valve with multiple regurgitant jets making quantification of mitral regurgitation (MR) difficult. Hypothesis: Our objective was to evaluate the accuracy of double jet MR quantification by summation of individual jet 3D echo-derived vena contracta area (VCA) or 2D proximal isovelocity surface area (PISA) estimation of regurgitant volume (RV). Methods: In a pulsatile flow loop model, six valve constructs were evaluated with RV of 25 ml, 45 ml, and 65ml/beat. Regurgitant orifices tested were: a single circular hole (n=6), two symmetric circular holes (n=6), and an asymmetric configuration with a circular hole and an elliptical hole (n=6). RV was compared with true flow measurements from in vitro flow transducers. RV was calculated as: 1) PISA-Effective regurgitant orifice area x Doppler time velocity interval (TVI) or 2) VCA x Doppler TVI. Results: RV derived by PISA method correlated well with reference standard flow measures for both single orifice and double orifice valve constructs (R=0.96 vs R=0.90, p&lt;0.0001, respectively). PISA-RV also demonstrated a good correlation to true RV when tested through symmetric or asymmetric double orifice disks (R=0.96 vs R=0.87,p&lt;0.0001). 3D-VCA derived RV showed a superior correlation using the symmetric vs asymmetric disks (R=0.946 vs R=0.63,p&lt;0.001). Conclusions: In a pulsatile model of double orifice MR, total RV is accurately measured by summation of PISA-derived RV or VCA -derived RV from each orifice. These methods deserve further evaluation in the clinical setting.

Control of the electric field–polymer solution interaction by utilizing ultra-conductive fluids

Dramatically raising the conductivity of a polymer solution by using a salt additive allows control over the electric field-induced jet feed rate when electrospinning from an unconfined fluid without altering the applied voltage. As the solution conductivity increases, the flow rate drops by an order of magnitude. At a high voltage level and fluid conductivity value, the jets undergo a whipping instability over almost the entire path from the source to the collector experiencing only a negligibly short linear region which, along with the flow rate data, indicates that the jet narrows due to the high conductivity. Under these conditions, even while possessing relatively large individual jet feed rates, thin diameter nanofibers (200–300 nm) are readily produced. In contrast with other approaches to obtain narrow fibers from unconfined fluids (e.g., voltage reduction to control feed rate), here the fiber forming jets are present indefinitely. Continuous, scaled up nanofiber production rate of >125× over the traditional single needle electrospinning method is observed from the presence of multiple jets, each possessing a relatively high solution feed rate. These fundamental experiments reveal new pathways for exploring novel electrospinning configurations where the jet feed rate can be controlled by manipulating the solution conductivity.

Crossflows from jet array impingement cooling: Hole spacing, target plate distance, Reynolds number effects

Data which illustrate the combined and separate effects of hole array spacing, jet-to-target plate distance, and Reynolds number on cross-flows, and the resulting heat transfer, for an impingement jet array are presented. The array of impinging jets are directed to one flat surface of a channel which is bounded on three sides. Considered are Reynolds numbers ranging from 8000 to 50,000, jet-to-target plate distances of 1.5D, 3.0D, 5.0D, and 8.0D, and steamwise and spanwise hole spacing of 5D, 8D, and 12D, where D is the impingement hole diameter. In general, the cumulative accumulations of cross-flows, from sequential rows of jets, reduce the effectiveness of each individual jet (especially for jets at larger streamwise locations). In other situations, the impingement cross-flow results in locally augmented Nusselt numbers. Such variations most often occur at larger downstream locations, as jet interactions are more vigorous, and local magnitudes of mixing and turbulent transport are augmented. This occurs in channels at lower Reynolds numbers, where impingement jets are confined by smaller hole spacing, and smaller jet-to-target plate distance. The overall result is complex dependence of local, line-averaged, and spatially-averaged Nusselt numbers on hole array spacing, jet-to-target plate distance, and impingement jet Reynolds number.

Effect of Varying Jet Diameter on the Heat Transfer Distributions of Narrow Impingement Channels

The development of integrally cast turbine airfoils allows the production of narrow impingement channels in a double-wall configuration, where the coolant is practically injected within the wall of the airfoil providing increased heat transfer capabilities. This study examines the cooling performance of narrow impingement channels with varying jet diameters using a single exit design in an attempt to regulate the generated crossflow. The channel consists of a single row of five inline jets tested at two different channel heights and over a range of engine representative Reynolds numbers. Detailed heat transfer coefficient distributions are evaluated over the complete interior surfaces of the channel using the transient liquid crystal technique. Additionally, local jet discharge coefficients are determined by probe traversing measurements for each individual jet. A 10%-increasing and a 10%-decreasing jet diameter pattern are compared with a baseline geometry of uniform jet size distribution, indicating a considerable effect of varying jet diameter on the heat transfer level and the development of the generated crossflow.

TANAMI monitoring of Centaurus A: The complex dynamics in the inner parsec of an extragalactic jet

Centaurus A is the closest radio-loud active galaxy. Very Long Baseline Interferometry (VLBI) enables us to study the jet-counterjet system on milliarcsecond (mas) scales, providing essential information for jet emission and propagation models. We study the evolution of the central parsec jet structure of Cen A over 3.5 years. The proper motion analysis of individual jet components allows us to constrain jet formation and propagation and to test the proposed correlation of increased high energy flux with jet ejection events. Cen A is an exceptional laboratory for such detailed study as its proximity translates to unrivaled linear resolution, where 1 mas corresponds to 0.018 pc. The first 7 epochs of high-resolution TANAMI VLBI observations at 8 GHz of Cen A are presented, resolving the jet on (sub-)mas scales. They show a differential motion of the sub-pc scale jet with significantly higher component speeds further downstream where the jet becomes optically thin. We determined apparent component speeds within a range of 0.1c to 0.3c, as well as identified long-term stable features. In combination with the jet-to-counterjet ratio we can constrain the angle to the line of sight to ~12{\deg} to 45{\deg}. The high resolution kinematics are best explained by a spine-sheath structure supported by the downstream acceleration occurring where the jet becomes optically thin. On top of the underlying, continuous flow, TANAMI observations clearly resolve individual jet features. The flow appears to be interrupted by an obstacle causing a local decrease in surface brightness and a circumfluent jet behavior. We propose a jet-star interaction scenario to explain this appearance. The comparison of jet ejection times with high X-ray flux phases yields a partial overlap of the onset of the X-ray emission and increasing jet activity, but the limited data do not support a robust correlation.

HOW THE GEYSERS, TIDAL STRESSES, AND THERMAL EMISSION ACROSS THE SOUTH POLAR TERRAIN OF ENCELADUS ARE RELATED

We present the first comprehensive examination of the geysering, tidal stresses, and anomalous thermal emission across the south pole of Enceladus and discuss the implications for the moon's thermal history and interior structure. A 6.5 yr survey of the moon's south polar terrain (SPT) by the Cassini imaging experiment has located ~100 jets or geysers erupting from four prominent fractures crossing the region. Comparing these results with predictions of diurnally varying tidal stresses and with Cassini low resolution thermal maps shows that all three phenomena are spatially correlated. The coincidence of individual jets with very small (~10 m) hot spots detected in high resolution Cassini VIMS data strongly suggests that the heat accompanying the geysers is not produced by shearing in the upper brittle layer but rather is transported, in the form of latent heat, from a sub-ice-shell sea of liquid water, with vapor condensing on the near-surface walls of the fractures. Normal stresses modulate the geysering activity, as shown in the accompanying paper; we demonstrate here they are capable of opening water-filled cracks all the way down to the sea. If Enceladus' eccentricity and heat production are in steady state today, the currently erupting material and anomalous heat must have been produced in an earlier epoch. If regional tidal heating is occurring today, it may be responsible for some of the erupting water and heat. Future Cassini observations may settle the question.

Behavior of Multiple-Jet Interactions in a Hypersonic Boundary Layer

The fundamental flow physics of the interaction between an array of fuel jets and a hypersonic boundary layer is investigated. Hydrogen is injected at jet-to-freestream dynamic pressure ratios ranging from 0.350 to 0.875 on a flat plate into a Mach 4.5 crossflow. The injection array consists of four streamwise-aligned flush circular portholes. Both the streamwise spacing and jet-to-freestream dynamic pressure ratio are varied in a parametric study. The injection was performed completely within the boundary layer, with the intention of application to film-cooling drag reduction and boundary-layer combustion. Numerical simulations of four streamwise-aligned transverse sonic injectors in a fully turbulent hypersonic boundary layer revealed a very complex jet interaction flowfield. Variation of the streamwise injector port spacing, along with the jet-to-freestream dynamic pressure ratio, induced a variety of flow structures in the cases investigated. For all downstream interactions, the associated flow behavior was found to be a direct result of both the various upstream effects and interactions between adjacent injectors. Variations in the jet-to-freestream dynamic pressure ratio had a strong effect on the flow behavior. At low injection mass flow rates, coupling of adjacent injectors was small, whereas high mass flow rates increased the effect of jet-to-jet coupling. Variations in the streamwise jet-to-jet spacing were also found to play a critical role in the flow behavior. At very close spacings, intense interactions coupled the behavior of the individual jets; however, at increased spacings, the larger spatial freedom allowed individual jets to develop more naturally, leading to less jet-to-jet interactions. At the maximum spacing investigated, the jet interactions behaved more like discrete jets in crossflow.

COLLECTIVE OUTFLOW FROM A SMALL MULTIPLE STELLAR SYSTEM

The formation of high-mass stars is usually accompanied by powerful protostellar outflows. Such high-mass outflows are not simply scaled-up versions of their lower-mass counterparts, since observations suggest that the collimation degree degrades with stellar mass. Theoretically, the origins of massive outflows remain open to question because radiative feedback and fragmentation of the accretion flow around the most massive stars, with M > 15 M_Sun, may impede the driving of magnetic disk winds. We here present a three-dimensional simulation of the early stages of core fragmentation and massive star formation that includes a subgrid-scale model for protostellar outflows. We find that stars that form in a common accretion flow tend to have aligned outflow axes, so that the individual jets of multiple stars can combine to form a collective outflow. We compare our simulation to observations with synthetic H_2 and CO observations and find that the morphology and kinematics of such a collective outflow resembles some observed massive outflows, such as Cepheus A and DR 21. We finally compare physical quantities derived from simulated observations of our models to the actual values in the models to examine the reliability of standard methods for deriving physical quantities, demonstrating that those methods indeed recover the actual values to within a factor of 2-3.

Parametric Study of Synthetic-Jet-Based Control for Performance Enhancement of a Vertical Tail

Application of aerodynamic flow control to the vertical tail of an aircraft could enable significant decrease in its size, with corresponding reductions in drag, weight, and fuel costs. Wind-tunnel experiments at a Reynolds number of 350,000 were conducted on a sweptback tapered vertical tail capable of sideslip rotation. The model used in the present work was approximately th scale with a NACA 0012 airfoil section. It was instrumented with an array of finite-span synthetic jet actuators distributed along the span, just upstream of the rudder hingeline. When the synthetic jets were activated, the side force coefficient was increased by a maximum of 0.17 (34%) over the baseline vertical tail. A primary objective of this work was to explore the effect of the orientation, location, and geometry of the synthetic jet orifices on control effectiveness. The parameters under investigation were orifice aspect ratio, spacing between adjacent orifice edges, the chordwise jet location, spanwise location, skew angle, and spanwise actuator density. This set of experiments suggested that the actuators’ spanwise spacing can be too dense (that is, maintaining constant individual jet strength and reducing the spanwise density of active actuators such that the total area-based momentum decreased, did not have a detrimental effect on side force enhancement for some conditions). The relative importance of other parameters that are typically used to quantify synthetic jet strength was also analyzed; the area-based momentum coefficient was determined to be a much more dominant factor than the blowing ratio and chord-based momentum coefficient.

MOJAVE: MONITORING OF JETS IN ACTIVE GALACTIC NUCLEI WITH VLBA EXPERIMENTS. XI. SPECTRAL DISTRIBUTIONS

We have obtained milliarcsecond-scale spectral index distributions for a sample of 190 extragalactic radio jets through the MOJAVE project. The sources were observed in 2006 at 8.1, 8.4, 12.1, and 15.4 GHz, and we study the four-frequency spectrum in individual jet features. We performed detailed simulations to study the effects of image alignment and (u,v)-plane coverage on the spectral index maps to verify our results. The core spectral indices are on average flat, while the jet spectrum is in general steep with a mean index of -1.04. A simple power-law fit is often inadequate for the core regions, as expected if the cores are partially self-absorbed. The overall jet spectrum steepens at a rate of about -0.001 to -0.004 per deprojected parsec when moving further out from the core with flat spectrum radio quasars having significantly steeper spectra than the BL Lac objects. The spectrum in both types of objects flattens at the locations of the jet components indicating particle acceleration or density enhancements along the jet. The mean spectral index at the component locations of -0.81 corresponds to a power-law index of ~2.6 for the electron energy distribution. We find a significant trend that jet components with linear polarization parallel to the jet (magnetic field perpendicular to the jet) have flatter spectra, as expected for transverse shocks. Compared to quasars, BL Lacs have more jet components with perpendicular magnetic field alignment, which may explain their generally flatter spectra. The overall steepening of the spectra with distance can be explained with radiative losses if the jets are collimating or with the evolution of the high-energy cutoff in the electron spectrum if the jets are conical. This interpretation is supported by a significant correlation with the age of the component and the spectral index, with older components having steeper spectra. (abridged)

Near-field mixing of jets issuing from an array of round nozzles

This article presents results of an experimental study of the confluence of low Reynolds number jets in the near field of a 6×6 in-line array of round nozzles. Particle Image Velocimetry (PIV) and Laser Doppler Anemometry (LDA) were employed to measure mean velocities and turbulence statistics. The comparison of the results from PIV and LDA measurements along different cross-sectional profiles and geometrical centerlines showed good agreement. However, LDA enabled more accurate results very close to the nozzle exits. The evolution of all the individual jets in the array into a single jet showed flow regions similar to twin jets (i.e., initial, converging including mixing transition, merging and combined regions). The lateral displacements play an important role for a confluent jet, where all jets to some degree are deflected towards the center of the nozzle plate. The jet development in terms of velocity decay, length of potential core and lateral displacement varies significantly with the position of the jet in the array. A comparison with single jet and twin jets flow showed considerable differences in velocity decay as well as location and velocity in the combined point. The flow field of confluent jets showed asymmetrical distributions of Reynolds stresses around the axis of the jets and highly anisotropic turbulence. Additionally, the lateral displacement as well as the turbulence development in the proximal region of the studied confluent jet was shown to be dependent on Reynolds number.

Cooperative Merging of Atmospheric Pressure Plasma Jet Arrays

Scaling of large area atmospheric pressure plasma jet arrays remains a key challenge due to electrical and hydrodynamical coupling between individual plasma jets. Here, we present a novel means by which to obtain a large-volume large-surface-area atmospheric plasma jet array in helium. The individual jets of the plasma jet array are confined to expand in a secondary jet tube. The secondary jet tube assists the individual jets in mixing to form a single large-volume large-surface-area plasma jet on a downstream substrate. It is envisaged that the present system will facilitate more homogeneous treatment of large surface areas in both surface treatment and plasma medicine applications.