MHD simulations of jet acceleration from Keplerian accretion disks

Zanni, C.; Ferrari, A.; Rosner, R.; Bodo, G.; Massaglia, S.

doi:10.1051/0004-6361:20066400

Cited by 207 publications

(274 citation statements)

References 49 publications

Supporting

Mentioning

244

Contrasting

Order By: Relevance

“…This has been shown with the calculations of magnetized accretion-ejection structures by Ferreira & Pelletier (1995) and confirmed by numerical MHD simulations (Casse & Keppens 2002;Zanni et al 2007). In one sense, making funnel flows involves the same physics as loading mass in magnetized jets.…”

Section: The Disc Truncation Radiussupporting

confidence: 73%

Accretion funnels onto weakly magnetized young stars

Bessolaz

Zanni

Ferreira

et al. 2007

A&A

Self Cite

168

215

View full text Add to dashboard Cite

Aims. We re-examine the conditions required to steadily deviate an accretion flow from a circumstellar disc into a magnetospheric funnel flow onto a slow rotating young forming star. Methods. New analytical constraints on the formation of accretion funnels flows due to the presence of a dipolar stellar magnetic field disrupting the disc are derived. The Versatile Advection Code is used to confirm these constraints numerically. Axisymmetric MHD simulations are performed, where a stellar dipole field enters the resistive accretion disc, whose structure is self-consistently computed.Results. The analytical criterion derived allows to predict a priori the position of the truncation radius from a non perturbative accretion disc model. Accretion funnels are found to be robust features which occur below the co-rotation radius, where the stellar poloidal magnetic pressure becomes both at equipartition with the disc thermal pressure and is comparable to the disc poloidal ram pressure. We confirm the results of Romanova et al. (2002, ApJ, 578, 420) and find accretion funnels for stellar dipole fields as low as 140 G in the low accretion rate limit of 10 −9 M yr −1 . With our present numerical setup with no disc magnetic field, we found no evidence of winds, neither disc driven nor X-winds, and the star is only spun up by its interaction with the disc. Conclusions. Weak dipole fields, similar in magnitude to those observed, lead to the development of accretion funnel flows in weakly accreting T Tauri stars. However, the higher accretion observed for most T Tauri stars (Ṁ ∼ 10 −8 M yr −1 ) requires either larger stellar field strength and/or different magnetic topologies to allow for magnetospheric accretion.

show abstract

Section: The Disc Truncation Radiussupporting

confidence: 73%

Accretion funnels onto weakly magnetized young stars

Bessolaz

Zanni

Ferreira

et al. 2007

A&A

Self Cite

168

215

View full text Add to dashboard Cite

show abstract

“…If the field is slightly below equipartition, rotation remains quasiKeplerian in the disk midplane and angular momentum can be efficiently extracted by magnetic torques to launch a powerful wind from the disk surface, as shown by analytical and numerical 2D solutions of the vertical disk structure (Ferreira 1997;Zanni et al 2007). Pesenti et al (2004) found that a self-similar, steady MHD wind from a warm disk (Casse & Ferreira 2000), with a lever arm parameter λ = (r A /r 0 ) 2 13 could fit the tentative jet rotation signatures observed in the low-velocity [O i] flow (Bacciotti 2002).…”

Section: Extended Mhd Disk Windmentioning

confidence: 99%

Sub-arcsecond [Fe ii] spectro-imaging of the DG Tauri jet

Agra-Amboage

Dougados

Cabrit

et al. 2011

A&A

111

View full text Add to dashboard Cite

Context. The origin of protostellar jets as well as their impact on the regulation of angular momentum and the inner disk physics are still crucial open questions in star formation. Aims. We aim to test the different proposed ejection processes in T Tauri stars through high-angular resolution observations of forbidden-line emission from the inner DG Tauri microjet. Methods. We present spectro-imaging observations of the DG Tauri jet obtained with SINFONI/VLT in the lines of [Fe ii]λ1.64 μm, 1.53 μm with 0. 15 angular resolution and R = 3000 spectral resolution. We analyze the morphology and kinematics, derive electronic densities and mass-flux rates and discuss the implications for proposed jet launching models. Results. (1) We observe an onion-like velocity structure in [Fe ii] in the blueshifted jet, similar to that observed in optical lines. Highvelocity (HV) gas at -200 km s −1 is collimated inside a half-opening angle of 4 • and medium-velocity (MV) gas at -100 km s −1 in a cone with an half-opening angle 14.• (2) Two new axial jet knots are detected in the blue jet, as well as a more distant bubble with corresponding counter-bubble. The periodic knot ejection timescale is revised downward to 2.5 yrs. (3) The redshifted jet is detected only beyond 0. 7 from the star, yielding revised constraints on the disk surface density. (4) From comparison to [O i] data we infer iron depletion of a factor 3 at high velocities and a factor 10 at speeds below -100 km s −1 . (5) The mass-fluxes in each of the medium and high-velocity components of the blueshifted lobe are 1.6 ± 0.8 × 10 −8 M yr −1 , representing 0.02−0.2 of the disk accretion rate. Conclusions. The medium-velocity conical [Fe ii] flow in the DG Tau jet is too fast and too narrow to trace photo-evaporated matter from the disk atmosphere. Both its kinematics and collimation cannot be reproduced by the X-wind, nor can the "conical magnetospheric wind". The level of Fe gas phase depletion in the DG Tau medium-velocity component also rules out a stellar wind and a cocoon ejected sideways from the high-velocity beam. A quasi-steady centrifugal MHD disk wind ejected over 0.25−1.5 AU and/or episodic magnetic tower cavities launched from the disk appear as the most plausible origins for the [Fe ii] medium velocity component in the DG Tau jet. The same disk wind model can also account for the properties of the high-velocity [Fe ii] flow, although alternative origins in magnetospheric and/or stellar winds cannot be excluded for this component.

show abstract

“…In case of massive protostellar systems that are formed deeply embedded in molecular clouds, they contribute to the feedback mechanism that can either halt or induce the infall process (Frank et al 2014). Numerical simulations predict the generation of jets from disk winds with the magnetic field playing a prominent role (Zanni et al 2007;Fendt 2006;Ouyed & Pudritz 1997). The regions close to the launch of protostellar jets have been examined using high resolution spectroscopy in optical wavebands leading to a better understanding ⋆ E-mail: sarita@iist.ac.in of the collimation properties and velocity structure at the base (Coffey, Bacciotti & Podio 2008).…”

Section: Introductionmentioning

confidence: 99%

Detection of non-thermal emission from the massive protostellar jet HH80-81 at low radio frequencies using GMRT

Vig

Veena

Mandal

et al. 2017

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

Low radio frequencies are favourable for the identification of emission from non-thermal processes such as synchrotron emission. The massive protostellar jet associated with IRAS 18162-2048 (also known as the HH80-81 system) has been imaged at low radio frequencies: 325, 610 and 1300 MHz, using the Giant Metrewave Radio Telescope, India. This is the first instance of detection of non-thermal emission from a massive protostellar jet at such low radio frequencies. The central region displays an elongated structure characteristic of the jet. In addition, the associated Herbig-Haro objects such as HH80, HH81, HH80N, and other condensations along the inner regions of the jet exhibit negative spectral indices. The spectral indices of most condensations are ∼ −0.7, higher than the value of −0.3 determined earlier using high frequency measurements. The magnetic field values derived using radio flux densities in the present work, under the assumption of equipartition near minimum energy condition, lie in the range 116 − 180 µG. We probe into the hard X-ray nature of a source that has been attributed to HH80, in an attempt to reconcile the non-thermal characteristics of radio and X-ray measurements. The flux densities of condensations at 610 MHz, measured nearly 11 yrs apart, display variability that could be ascribed to the cooling of condensations, and emphasize the importance of coeval or nearly-coeval measurements for estimation of spectral indices.

show abstract

MHD simulations of jet acceleration from Keplerian accretion disks

Cited by 207 publications

References 49 publications

Accretion funnels onto weakly magnetized young stars

Accretion funnels onto weakly magnetized young stars

Sub-arcsecond [Fe ii] spectro-imaging of the DG Tauri jet

Detection of non-thermal emission from the massive protostellar jet HH80-81 at low radio frequencies using GMRT

Contact Info

Product

Resources

About