Searcharxiv⌕ Search
Home/Archive/arXiv

arXiv · 2610.26176

Competitive roles of turbulence and magnetic field on the formation of unipolar outflows in isolated molecular cloud cores

Daisuke Takaishi·Yusuke Tsukamoto·Miyu Kido·Shigehisa Takakuwa·Yoshiaki Misugi·Yuki Kudoh·Yasushi Suto
View original source ↗Read source document ↗Export metadata ↓

Abstract

We investigate the impact of turbulence and magnetic field on the formation of unipolar outflows in the gravitational collapse of isolated low-mass cloud cores using three-dimensional non-ideal magnetohydrodynamics simulations. In the models explored in this study, we find that unipolar outflows are formed in cloud cores with the super-Alfvénic turbulence of $M_{\rm{A}}>1$, where $M_{\rm{A}}$ is the Alfvén Mach number of the initial cloud core. In contrast, bipolar outflows are formed in cloud cores with $M_{\rm{A}}\lesssim1$. Our results suggest that the relative strength of the turbulence to the magnetic field in the initial cloud core plays a key role in the formation of unipolar outflows. We also find that no outflow is formed in cloud cores with the strong magnetic field of the dimensionless mass-to-flux ratio $μ=2$. The outflow morphologies can be used as tracers to indirectly estimate the relative strengths of the turbulence and magnetic field of the parent cloud cores.

Explore related subjects

astro-ph.SRastro-ph.EPastro-ph.GA

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Daisuke Takaishi, Yusuke Tsukamoto, Miyu Kido, Shigehisa Takakuwa, Yoshiaki Misugi, Yuki Kudoh, Yasushi Suto. 2026-10-19. Competitive roles of turbulence and magnetic field on the formation of unipolar outflows in isolated molecular cloud cores. https://arxiv.org/abs/2610.26176

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Magnetic pressure anisotropy in ultra-dense white dwarfs: Landau quantization and neutronization effects

Strong magnetic fields modify the thermodynamics of white dwarf (WD) matter by quantizing the transverse motion of degenerate electrons into Landau levels and splitting the pressure into components parallel and perpendicular to the magnetic field. We investigate how this microscopic pressure anisotropy affects ultra-dense WD sequences when Coulomb lattice contributions, electron capture thresholds, neutron drip limits, and nuclear composition are treated consistently in the equation of state (EoS). The stellar equilibrium structure is obtained by solving an anisotropic extension of the Tolman--Oppenheimer--Volkoff (TOV) equations, where $P_r = P_\parallel$ and $P_t = P_\perp$ denote the radial and tangential pressures, respectively. We compare the post-electron-capture branches with their corresponding pre-capture sequences for pure $^{12}\rm{C}$, $^{16}\rm{O}$, $^{20}\rm{Ne}$, and $^{24}\rm{Mg}$ compositions, as well as for fixed 50/50 C/O, Ne/O, and Mg/Ne mixtures. The EoS predicts $P_\perp < P_\parallel$ in density ranges where only a few Landau levels are occupied. Consequently, pressure anisotropy shifts the stellar sequences toward smaller radii, with only minor changes in the maximum masses. We also find that post-capture configurations cannot be interpreted from the mass--radius plane alone, since the corresponding $M(ρ_c)$ curves reveal unstable portions after the maximum mass is reached. Our results show that strong magnetic fields significantly reduce the radii of low-mass WDs, yielding better agreement with the observational data available in the Montreal White Dwarf Database and suggesting that future high-precision observations of massive magnetic WDs could help assess the role of magnetic pressure anisotropy in determining their masses and radii.

astro-ph.SR↗
arXiv2026

A giant magnetic eruption from the asymptotic giant branch star Mira A

Mass loss during the advanced evolutionary stages of low- and intermediate-mass stars is traditionally attributed to dust-driven winds, whereas the influence of magnetic fields remains poorly constrained. However, recent observations show massive directional mass ejections from the nearby asymptotic giant branch (AGB) star Mira~A that appear not to be driven by radiation pressure on the dust. We observationally investigate whether magnetic fields are responsible for the mass loss ejections from Mira A. We obtained full-polarisation ALMA observations of the SiO $v=1$, $J=5\rightarrow4$ maser transition at 215 GHz with angular resolutions of 1.5-2.6 au. The observations reveal a highly magnetized loop-like mass ejection traced by strongly polarised SiO masers extending to approximately eight stellar radii. The morphology, polarisation pattern, energetics, and kinematics indicate a magnetically driven eruption analogous to a stellar coronal mass ejection. The observations demonstrate that magnetic eruptions can dominate mass loss from evolved stars and imply that magnetic fields must become an integral component of future models of AGB, and potentially other cool giant, winds.

astro-ph.SR↗
arXiv2026

Periodic activity on the (sub)mm surface of the AGB star Mira A

Evolved stars on the asymptotic giant branch (AGB) lose mass through stellar winds launched from their dynamic extended atmospheres. Recent high-angular-resolution observations of the archetypal AGB star Mira A (o Ceti) have revealed compact hotspots on its (sub)millimetre surface, whose origin remains unclear. We aim to characterise the (sub)millimetre photosphere of Mira A and investigate the properties and temporal behaviour of the compact hotspots detected on its surface. We analysed 19 epochs of high-angular-resolution observations obtained with ALMA in Bands 4, 6, 7, and 9. The complex visibilities were fitted with parametric models to derive the flux density, size, morphology, and brightness temperature of the stellar disc and an additional, more compact component across multiple pulsation phases and observing frequencies. Our results show that, near maximum light, the flux density of the stellar disc increases with frequency while its apparent size decreases, in agreement with the expected stratified radio photosphere. In Band 6, both the flux density and the size of the stellar disc appear to vary with pulsation phase, with the largest measured values occurring close to optical maximum light and the lowest observed around minimum light. Compact hotspots are detected in Bands 6 and 7 near maximum light, with their brightness temperatures exceeding those of the stellar disc by several thousand kelvin and reaching a temperature excess of ~8200 K in Band 6. They are highly energetic and are detected over timescales of weeks, while the available observations also suggest potential longer-term changes in both their position and intensity. Hotspot activity appears to occur repeatedly across multiple pulsation cycles and may be linked to strong shocks, magnetic activity, and/or episodic mass ejections, and could therefore play an important role in the mass-loss process in AGB stars.

astro-ph.SR↗