Inferring possible magnetic field strength of accreting inflows in EXor-type objects from scaled laboratory experiments

Abstract

Aims. EXor-type objects are protostars that display powerful UV-optical outbursts caused by intermittent and powerful events of magnetospheric accretion. These objects are not yet well investigated and are quite difficult to characterize. Several parameters, such as plasma stream velocities, characteristic densities, and temperatures, can be retrieved from present observations. As of yet, however, there is no information about the magnetic field values and the exact underlying accretion scenario is also under discussion. Methods. We use laboratory plasmas, created by a high power laser impacting a solid target or by a plasma gun injector, and make these plasmas propagate perpendicularly to a strong external magnetic field. The propagating plasmas are found to be well scaled to the presently inferred parameters of EXor-type accretion event, thus allowing us to study the behaviour of such episodic accretion processes in scaled conditions. Results. We propose a scenario of additional matter accretion in the equatorial plane, which claims to explain the increased accretion rates of the EXor objects, supported by the experimental demonstration of effective plasma propagation across the magnetic field. In particular, our laboratory investigation allows us to determine that the field strength in the accretion stream of EXor objects, in a position intermediate between the truncation radius and the stellar surface, should be of the order of 100 G. This, in turn, suggests a field strength of a few kilogausses on the stellar surface, which is similar to values inferred from observations of classical T Tauri stars.

Electron Energization Dynamics in Interaction of Self-Generated Magnetic Vortices in Upstream of Collisionless Electron/Ion Shocks

“…It is worth mentioning that high power laser facilities provide a unique opportunity for laboratory experiments using plasma flows driven by high energy laser systems which opens a new era in astrophysics and space exploration. Laboratory experiments open the door to investigate the electron-ion sub-relativistic and relativistic collisionless shocks, magnetic field generation and amplification, magnetic reconnection, and particle acceleration in a short temporal and limited spatial scale via laser-plasma interactions [32][33][34] . Energy transfer from fast ion flow to electromagnetic fields and fast particles (electrons and ions), at a time scale much shorter than electron-ion collisional energy exchange time can be modelled in laboratory conditions.…”

What governs the spin distribution of very young < 1 Myr low-mass stars

“…In addition, the small number of available measurements does not have to be representative. There are, however, estimates on the magnetic field strength of Class I (0) objects ranging from ∼ 0.1 kG to ∼ 1 kG based on flux conservation during the core collapse (Tsukamoto et al 2022), near-infrared K-band spectra (Laos et al 2021), and laboratory plasma experiments (Burdonov et al 2021). These estimates match the inferred field strengths for WL 17 and V347 Aur.…”