2019A&A...628A.121N


Query : 2019A&A...628A.121N

2019A&A...628A.121N - Astronomy and Astrophysics, volume 628A, 121-121 (2019/8-1)

What is wrong with steady accretion discs?

NIXON C.J. and PRINGLE J.E.

Abstract (from CDS):

In a standard, steady, thin accretion disc, the radial distribution of the dissipation of the accretion energy is determined simply by energy considerations. Here we draw attention to the fact that while the (quasi-)steady discs in dwarf novae in outburst are in agreement with the expected emission distribution, the steady discs in the nova-like variables are not. We note that essentially the only difference between these two sets of discs is the time for which they have been in the high viscosity, high accretion rate state. In such discs, the major process by which angular momentum is transported outwards is MHD turbulence. We speculate that such turbulence gives rise to corona-like structures (here called magnetically controlled zones, or MCZs) which are also able to provide non-negligible angular momentum transport, the magnitude of which depends on the spatial scale L of the magnetic field structures in such zones. For short-lived, high accretion rate discs (such as those in dwarf novae) we expect L∼H and the MCZ to have little effect. But, with time (such as in the nova-like variables) an inverse cascade in the MHD turbulence enables L, and the net effect of the MCZ, to grow. We present a simple toy model which demonstrates that such ideas can provide an explanation for the difference between the dwarf novae and the nova-like variable discs.

Abstract Copyright: © ESO 2019

Journal keyword(s): accretion - accretion disks - magnetic fields - magnetohydrodynamics (MHD) - novae - cataclysmic variables

Simbad objects: 8

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Number of rows : 8
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2024
#notes
1 V* V592 Cas CV* 00 20 52.2230598456 +55 42 16.235113356 12.07 12.86 12.79 12.783   OB 105 0
2 V* VW Hyi CV* 04 09 11.3967378648 -71 17 41.554528260   12.786 12.543 14.160   ?+L0:e 649 0
3 EGB 4 CV* 06 29 33.9600353880 +71 04 36.394613580   13.29 13.27 13.04   ~ 157 0
4 HS 0805+3822 CV* 08 09 08.3945706216 +38 14 06.206132976           ~ 28 0
5 V* IX Vel CV* 08 15 18.9688659456 -49 13 20.671780368 8.64 10.04 10.10 9.84 9.347 sdOBe 242 0
6 V* RW Sex CV* 10 19 56.6224471752 -08 41 56.106711816   10.674 10.645 10.747 10.598 DAe 206 0
7 V* MV Lyr CV* 19 07 16.2886463256 +44 01 07.869892008   13.040 12.920 12.489 12.578 M5Ve 287 0
8 V* SS Cyg CV* 21 42 42.8034497592 +43 35 09.867842484 11.07 12.651 12.032 9.326   K5V 1293 1

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