Abstract
Context. The equatorial accretion scenario, caused by the development of the Rayleigh-Taylor (RT) instability at the disk edge, was suggested by accurate three-dimensional magnetohydrodynamic (MHD) modelling, but no observational or experimental confirmation of such phenomena has been evidenced yet. Aims. We studied the propagation of a laterally extended laser-generated plasma stream across a magnetic field and investigated if this kind of structure can be scaled to the case of equatorial ‘tongue’ accretion channels in young stellar objects (YSOs); if so, this would support the possibility of equatorial accretion in young accreting stars. Methods. We conducted a scaled laboratory experiment at the PEARL laser facility. The experiment consists in an optical laser pulse that is focused onto the surface of a Teflon target. The irradiation of the target leads to the expansion of a hot plasma stream into the vacuum, perpendicularly to an externally applied magnetic field. We used a Mach-Zehnder interferometer to diagnose the plasma stream propagation along two axes, to obtain the three-dimensional distribution of the plasma stream. Results. The laboratory experiment shows the propagation of a laterally extended laser-generated plasma stream across a magnetic field. We demonstrate that: (i) such a stream is subject to the development of the RT instability, and (ii) the stream, decomposed into tongues, is able to efficiently propagate perpendicular to the magnetic field. Based on numerical simulations, we show that the origin of the development of the instability in the laboratory is similar to that observed in MHD models of equatorial tongue accretion in YSOs. Conclusions. As we verify that the laboratory plasma scales favourably to accretion inflows of YSOs, our laboratory results support the argument in favour of the possibility of the RT-instability-caused equatorial tongue accretion scenario in the astrophysical case.
Highlights
The dynamics of matter accretion onto the surface of young stellar objects (YSOs) has been the subject of intense research in the past few decades
We conducted a laboratory experiment, in which we explored the development of the RT instability of a laser-created plasma stream propagating in a vacuum across an
We conducted laboratory experiments at the PEARL laser facility that describe a laterally extended, hot laser-generated plasma stream expanding into a vacuum perpendicularly to an ambient magnetic field
Summary
The dynamics of matter accretion onto the surface of young stellar objects (YSOs) has been the subject of intense research in the past few decades. The specificity of our work with respect to the abovementioned studies is that here the surface of the target affected by laser irradiation is very large This allows us to launch the plasma across the magnetic field over a wide area, from which we observe the development of the RT instability that breaks the spatially wide expanding plasma into many individual ‘tongues’. 5 we discuss the results and draw conclusions This was done simultaneously along two axes, namely the x axis and y axis, providing two projections of the plasma density in order to obtain the three-dimensional distribution of the plasma stream.
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