The effect of diffusion of magnetic field on flow structure in close binaries

Жилкин, А. Г.; Bisikalo, D. V.

doi:10.1016/j.asr.2009.09.006

Cited by 19 publications

(22 citation statements)

References 31 publications

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“…Our mCV simulations were carried out using the Nurgush 3D parallel numerical code [27][28][29]31]. This code is based on a finite-difference Godunovtype scheme with a high approximation order.…”

Section: Methodsmentioning

confidence: 99%

“…This code was used in [27,29,30] to investigate the flow structure in a close binary system (SS Cyg was taken as an example) with a relatively weak, purely dipolar magnetic field (10 5 G at the surface). A modification of the code was introduced in [31], which enables simulations of systems with strong dipolar magnetic fields (10 7 −10 8 G).…”

Section: Introductionmentioning

confidence: 99%

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Full 3D MHD calculations of accretion flow structure in magnetic cataclysmic variables with strong, complex magnetic fields

2012

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We have performed three-dimensional magnetohydrodynamical calculations of stream accretion in cataclysmic variable stars for which the white dwarf primary possesses a strong, complex magnetic field. These calculations were motivated by observations of polars: cataclysmic variables containing white dwarfs with magnetic fields sufficiently strong to prevent the formation of an accretion disk. In this case, an accretion stream flows from the L 1 point and impacts directly onto one or more spots on the surface of the white dwarf. Observations indicate that the white dwarfs in some binaries possess complex (non-dipolar) magnetic fields. We performed simulations of ten polars, with the only variable being the azimuthal angle of the secondary with respect to the white dwarf. These calculations are also applicable to asynchronous polars, where the spin period of the white dwarf differs by a few percent from the orbital period. Our results are equivalent to calculating the structure of one asynchronous polar at ten different spin-orbit beat phases. Our models have an aligned dipolar plus quadrupolar magnetic field centered on the whitedwarf primary. We find that, with a sufficiently strong quadrupolar component, an accretion spot arises near the magnetic equator for slightly less than half our simulations, while a polar accretion zone is active for most of the remaining simulations. For two configurations, accretion at a dominant polar region and in an equatorial zone occurs simultaneously. Most polar studies assume that the magnetic field is dipolar, especially for single-pole accretors. We demonstrate that, with the orbital parameters and magnetic-field strengths typical of polars, the accretion flow patterns can vary widely in the case of a complex magnetic field. This may make it difficult for many polars to determine observationally whether the field is pure dipolar or is more complex, but there shoulid be indications for some systems. In particular, a complex magnetic field should be suspected if there is an accretion zone near the white dwarf's equator (assumed to be in the orbital plane) or if there are two or more accretion regions that cannot be fitted by dipolar magnetic field. Magnetic-field constraints are expected to be substantially stronger for asynchronous polars, with clearer signs of complex field geometry due to changes in the accretion flow structure as a function of azimuthal angle. These indications become clearer in asynchronous polars because each azimuthal angle corresponds to a different spin-orbit beat phase.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Full 3D MHD calculations of accretion flow structure in magnetic cataclysmic variables with strong, complex magnetic fields

2012

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“…However, effects associated with the presence of a poloidal velocity in the disk and redistribution of the magnetic field in the disk could also be important here [156]. The magnetic field can interact with waves arising in the inner part of the disk [128], leading to quasi-periodic variations of the rate of accretion onto the star [157]. Current sheets could form in the accretion disk [154] if the co-rotation radius exceeds the magnetosphere radius.…”

Section: Magnetic Cataclysmic Variablesmentioning

confidence: 99%

Scientific problems addressed by the Spektr-UV space project (world space Observatory—Ultraviolet)

et al. 2016

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Abstract-The article presents a review of scientific problems and methods of ultraviolet astronomy, focusing on perspective scientific problems (directions) whose solution requires UV space observatories. These include reionization and the history of star formation in the Universe, searches for dark baryonic matter, physical and chemical processes in the interstellar medium and protoplanetary disks, the physics of accretion and outflows in astrophysical objects, from Active Galactic Nuclei to close binary stars, stellar activity (for both low-mass and high-mass stars), and processes occurring in the atmospheres of both planets in the solar system and exoplanets. Technological progress in UV astronomy achieved in recent years is also considered. The well advanced, international, Russian-led Spektr-UV (World Space Observatory-Ultraviolet) project is described in more detail. This project is directed at creating a major space observatory operational in the ultraviolet (115-310 nm). This observatory will provide an effective, and possibly the only, powerful means of observing in this spectral range over the next ten years, and will be an powerful tool for resolving many topical scientific problems.

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“…However, since the problem is very complicated, the investigations have been performed either in the frame of simplified models (King 1993;Wynn & King 1995;Wynn et al 1997;King & Wynn 1999;Norton et al 2004;Ikhsanov et al 2004;Norton et al 2008), or in a limited region of the stellar magnetosphere (Koldoba et al 2002;Romanova et al 2003Romanova et al , 2004aRomanova et al , 2004b. Only over the last few years, the authors have managed to develop a comprehensive 3D numerical model to calculate the flow structure in close binaries (Zhilkin & Bisikalo 2009, 2010a, 2010b, 2010c. In our approach, we use a complete system of MHD equations that allows one to describe all 510 D. V. Bisikalo & A. G. Zhilkin the main dynamic effects concerned with the magnetic field.…”

Section: Introductionmentioning

confidence: 99%

Flow Structure in Magnetic CVs

Бисикало

Жилкин

2011

Proc. IAU

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Abstract. We present a review of the modern concept of physical processes which go on in magnetic CVs with the mass transfer between the components. Using results of 3D MHD simulations, we investigated variations of the main characteristics of accretion disks depending on the value of the magnetic induction on the surface of the accreting star. In the frame of a self-consistent description of the MHD flow structure in close binaries, we formulate conditions of the disk formation and find a criterion that separates two types of flows corresponding to intermediate polars (intermediate magnetic field) and polars (strong field).The influence of asynchronous rotation of the accretor on the flow structure in magnetic close binaries is also discussed. Simulations show that the accretion instability arising in binaries with rapid rotation of accretor ("propeller" regime) can explain the mechanism of quasi-periodic dwarf nova outbursts observed in DQ Her systems.

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The effect of diffusion of magnetic field on flow structure in close binaries

Cited by 19 publications

References 31 publications

Full 3D MHD calculations of accretion flow structure in magnetic cataclysmic variables with strong, complex magnetic fields

Full 3D MHD calculations of accretion flow structure in magnetic cataclysmic variables with strong, complex magnetic fields

Scientific problems addressed by the Spektr-UV space project (world space Observatory—Ultraviolet)

Flow Structure in Magnetic CVs

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