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 … Show more
“…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.…”
Relativistic collisionless shocks are considered responsible for particle energization mechanisms leading to particle acceleration. While electron energization in shock front region of electron/ion collisionless shocks are the most commonly studied, the mechanism of electron energization in interaction with self-generated magnetic vortices (MVs) in upstream region is still unclear. We investigate electron energization mechanism in upstream region of electron/ion relativistic collisionless shocks, using two dimensional particle-in-cell (PIC) simulations. We discuss mechanism of electron energization which takes place in upstream region of the shock, where the counter stream particles interact with incoming flow. The energy gain of electrons happens during their interaction with evolving fields of self-generated magnetic vortices in this region. Three Fermi-like electron energization scenarios are discussed. Stochastic acceleration of electrons in interaction with fields of MV leads to anisotropic heating of fast electrons due to diffusion in the momentum space of electrons and, finally, synergetic effect of evolving fields of MVs leads to the formation of a power-law tail of supra-thermal particles.
“…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.…”
Relativistic collisionless shocks are considered responsible for particle energization mechanisms leading to particle acceleration. While electron energization in shock front region of electron/ion collisionless shocks are the most commonly studied, the mechanism of electron energization in interaction with self-generated magnetic vortices (MVs) in upstream region is still unclear. We investigate electron energization mechanism in upstream region of electron/ion relativistic collisionless shocks, using two dimensional particle-in-cell (PIC) simulations. We discuss mechanism of electron energization which takes place in upstream region of the shock, where the counter stream particles interact with incoming flow. The energy gain of electrons happens during their interaction with evolving fields of self-generated magnetic vortices in this region. Three Fermi-like electron energization scenarios are discussed. Stochastic acceleration of electrons in interaction with fields of MV leads to anisotropic heating of fast electrons due to diffusion in the momentum space of electrons and, finally, synergetic effect of evolving fields of MVs leads to the formation of a power-law tail of supra-thermal particles.
“…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.…”
Context. The origin of the stellar spin distribution at young ages is still unclear. Even in very young clusters (∼ 1 Myr), a significant spread is observed in rotational periods ranging from 1 to ∼ 10 days. Aims. We aim to study the parameters that might govern the spin distribution of low mass ( 1.0 M ) stars during the first million years of their evolution. Methods. We compute the evolution and rotational periods of young stars, using the MESA code, starting from a stellar seed, and take protostellar accretion, stellar winds, and the magnetic star-disk interaction into account. Furthermore, we add a certain fraction of the energy of accreted material into the stellar interior as additional heat and combine the resulting effects on stellar evolution with the stellar spin model. Results. For different combinations of parameters, stellar periods at an age of 1 Myr range between 0.6 days and 12.9 days. Thus, during the relatively short time period of 1 Myr, a significant amount of stellar angular momentum can already be removed by the interaction between the star and its accretion disk. The amount of additional heat added into the stellar interior, the accretion history, and the presence of disk and stellar winds have the strongest impact on the stellar spin evolution during the first million years. The slowest stellar rotations result from a combination of strong magnetic fields, a large amount of additional heat, and effective winds. The fastest rotators combine weak magnetic fields and ineffective winds or result from a small amount of additional heat added to the star. Scenarios that could lead to such configurations are discussed. Different initial rotation periods of the stellar seed, on the other hand, quickly converges and do not affect the stellar period at all. Conclusions. Our model matches up to 90% of the observed rotation periods in six young ( 3 Myr) clusters. Based on these intriguing results, we motivate to combine our model with a hydrodynamic disk evolution code to self-consistently include several important aspects such as episodic accretion events, magnetic disk winds, internal, and external photo-evaporation. Such a combined model could replace the widely-used disk-locking model during the lifetime of the accretion disk and provide valuable insights into the origin of the rotational period distribution of young clusters.
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