Non-linear evolution of the tidal elliptical instability in gaseous planets and stars

- Language phylogenesis is often presented as a matter of controversy between followers of continuity vs discontinuity theories of development. Both kinds of theory may be described as projects for mind naturalization. However, the latter seems better to agree with recent paleo-anthropological data, which hint at a non-linear evolution, with no sudden morphological change. The paper presents an account of G. H. Mead's theory which is surprisingly modern and of great relevance for present debates, as it describes the emergence of language as the joint action of adaptive skills already present in nature. Taking sociality as a biological universal, operating in different forms and degrees, Mead can trace the path from more elementary forms of social relation to the most complex and abstract tools of social thinking, typical of human communities.Keywords: Phylogeny of language, Mind, Society, Biology, Subject, Communication.Parole chiave: Filogenesi del linguaggio, Mente, Socialitŕ, Biologia, Soggettivitŕ, Comunicazione

Download Full-text

Non-Linear Evolution of Erupting Coronal Magnetic Fields

Astrophysics and Space Science Library - Observational Plasma Astrophysics: Five Years of Yohkoh and Beyond ◽

10.1007/978-94-011-5220-4_61 ◽

1998 ◽

pp. 353-356

Author(s):

Bambang Setiahadi ◽

Bachtiar Anwar ◽

Maki Akioka ◽

Takashi Sakurai

Keyword(s):

Magnetic Fields ◽

Linear Evolution ◽

Coronal Magnetic Fields ◽

Non Linear

Download Full-text

Non-linear evolution of the resonant drag instability in magnetized gas

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz666 ◽

2019 ◽

Vol 485 (3) ◽

pp. 3991-3998 ◽

Cited By ~ 6

Author(s):

Darryl Seligman ◽

Philip F Hopkins ◽

Jonathan Squire

Keyword(s):

Linear Theory ◽

Coherent Structures ◽

Magnetic Energy ◽

Density Fluctuations ◽

Linear Evolution ◽

Drag Forces ◽

Non Linear ◽

Magnetohydrodynamic Simulations ◽

First Time ◽

Different Parts

Abstract We investigate, for the first time, the non-linear evolution of the magnetized ‘resonant drag instabilities’ (RDIs). We explore magnetohydrodynamic simulations of gas mixed with (uniform) dust grains subject to Lorentz and drag forces, using the gizmo code. The magnetized RDIs exhibit fundamentally different behaviour than purely acoustic RDIs. The dust organizes into coherent structures and the system exhibits strong dust–gas separation. In the linear and early non-linear regime, the growth rates agree with linear theory and the dust self-organizes into 2D planes or ‘sheets.’ Eventually the gas develops fully non-linear, saturated Alfvénic, and compressible fast-mode turbulence, which fills the underdense regions with a small amount of dust, and drives a dynamo that saturates at equipartition of kinetic and magnetic energy. The dust density fluctuations exhibit significant non-Gaussianity, and the power spectrum is strongly weighted towards the largest (box scale) modes. The saturation level can be understood via quasi-linear theory, as the forcing and energy input via the instabilities become comparable to saturated tension forces and dissipation in turbulence. The magnetized simulation presented here is just one case; it is likely that the magnetic RDIs can take many forms in different parts of parameter space.

Download Full-text

Kelvin-Helmholtz Instabilities and the Emission Knots in Herbig-Haro Jets

Symposium - International Astronomical Union ◽

10.1017/s0074180900061751 ◽

1997 ◽

Vol 182 ◽

pp. 335-342 ◽

Cited By ~ 1

Author(s):

S. Massaglia ◽

M. Micono ◽

A. Ferrari ◽

G. Bodo ◽

P. Rossi

Keyword(s):

Numerical Simulations ◽

Astrophysical Jets ◽

General Applicability ◽

Simple Assumption ◽

Linear Evolution ◽

Radiation Losses ◽

Non Linear ◽

Constant Heating ◽

Non Equilibrium

We discuss the non-linear evolution of Kelvin-Helmholtz instabilities in Herbig-Haro jets performing numerical simulations by means of a PPM hydro-code modified as to include non-equilibrium, optically thin, radiation losses and heating. In this paper we discuss in particular the effects of different functional dependences of heating on density. The results obtained show a weak dependency of the instability evolution on the different forms of the heating function, that is largely unknown, therefore the simple assumption of constant heating, adopted in previous papers on this matter, does not lead to severe limitations on the general applicability of the results to the astrophysical jets and, in particular, to the origin of the emission knots.

Download Full-text