The Hβ Chromospheric Magnetic Field in a Quiescent Filament     

Xing-Ming Bao  Hong-Qi ZhangNational Astronomical Observatories  Chinese Academy of Sciences  Beijing  baoxm@sunlO.bao.ac.cn 《中国天文和天体物理学报》2003,3(1):87-97

We observed the line-of-sight magnetic field in the chromosphereand photosphere of a large quiescent filament on the solar disk on September 6, 2001 using the Solar Magnetic Field Telescope in Huairou Solar Observing Station. The chromospheric and photospheric magnetograms together with Hβ filtergrams of the filament were examined. The filament was located on the neutral line of the large scale longitudinal magnetic field in the photosphere and the chromosphere. The lateral feet of the filament were found to be related to magnetic structures with opposite polarities. Two small lateral feet are linked to weak parasitic polarity. There is a negative magnetic structure in the photosphere under a break of the filament. At the location corresponding to the filament in the chromospheric magnetograms, the magnetic strength is found to be about 40-70 Gauss (measuring error about 39 Gauss). The magnetic signal indicates the amplitude and orientation of the internal magnetic field in the filament. We discuss several possible causes which may produce such a measured signal. A twisted magnetic configuration inside the filament is suggested .  相似文献   

Transient Coronal Sigmoids and Rotating Erupting Flux Ropes     

L. M. Green  B. Kliem  T. Török  L. van Driel-Gesztelyi  G. D. R. Attrill 《Solar physics》2007,246(2):365-391

To determine the relationship between transient coronal (soft X-ray or EUV) sigmoids and erupting flux ropes, we analyse four events in which a transient sigmoid could be associated with a filament whose apex rotates upon eruption and two further events in which the two phenomena were spatially but not temporally coincident. We find the helicity sign of the erupting field and the direction of filament rotation to be consistent with the conversion of twist into writhe under the ideal MHD constraint of helicity conservation, thus supporting our assumption of flux rope topology for the rising filament. For positive (negative) helicity the filament apex rotates clockwise (counterclockwise), consistent with the flux rope taking on a reverse (forward) S shape, which is opposite to that observed for the sigmoid. This result is incompatible with two models for sigmoid formation: one identifying sigmoids with upward arching kink-unstable flux ropes and one identifying sigmoids with a current layer between two oppositely sheared arcades. We find instead that the observations agree well with the model by Titov and Démoulin (Astron. Astrophys. 351, 707, 1999), which identifies transient sigmoids with steepened current layers below rising flux ropes.  相似文献   

Diamagnetic screening of the magnetic field in accreting neutron stars     

Arnab Rai Choudhuri  Sushan Konar 《Monthly notices of the Royal Astronomical Society》2002,332(4):933-944

A possible mechanism for screening of the surface magnetic field of an accreting neutron star, by the accreted material, is investigated. We model the material flow in the surface layers of the star by an assumed two-dimensional velocity field satisfying all the physical requirements. Using this model velocity we find that, in the absence of magnetic buoyancy, the surface field is screened (i.e. there is submergence of the field by advection) within the time-scale of material flow of the top layers. On the other hand, if magnetic buoyancy is present, the screening happens over a time-scale that is characteristic of the slower flow of the deeper (and hence, denser) layers. For accreting neutron stars, this longer time-scale turns out to be about 10⁵ yr, which is of a similar order of magnitude to the accretion time-scale of most massive X-ray binaries.  相似文献   

An electrically powered binary star?     

KinwahWu  MarkCropper  GavinRamsay  KazuhiroSekiguchi 《Monthly notices of the Royal Astronomical Society》2002,331(1):221-227

We propose a model for stellar binary systems consisting of a magnetic and a non-magnetic white dwarf pair which is powered principally by electrical energy. In our model the luminosity is caused by resistive heating of the stellar atmospheres arising from induced currents driven within the binary. This process is reminiscent of the Jupiter–Io system, but greatly increased in power because of the larger companion and stronger magnetic field of the primary. Electrical power is an alternative stellar luminosity source, following on from nuclear fusion and accretion. We find that this source of heating is sufficient to account for the observed X-ray luminosity of the 9.5-min binary RX J1914+24, and provides an explanation for its puzzling characteristics.  相似文献   

Emission altitudes in young and old radio pulsars     

Jaros&#;aw Kijak 《Monthly notices of the Royal Astronomical Society》2001,323(3):537-541

This paper presents a comparison of emission altitudes in very young and very old radio pulsars. The author confirms that the altitudes at which radio emission at a given frequency is generated depend on the pulsar period and age, although the latter dependence is quite weak.  相似文献   

Resonant origin for density fluctuations deep within the Sun: helioseismology and magneto-gravity waves     

C. P. Burgess  N. S. Dzhalilov  T. I. Rashba  V. B. Semikoz  J. W. F. Valle 《Monthly notices of the Royal Astronomical Society》2004,348(2):609-624

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The magnetization of protoplanetary discs     

G. T. Birk  H. Wiechen  A. Kopp  H. Lesch 《Monthly notices of the Royal Astronomical Society》2003,339(2):455-459

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Magnetized fragmented mass transfer in cataclysmic variables: AE Aquarii, a trial case     

P. J. Meintjes 《Monthly notices of the Royal Astronomical Society》2004,352(2):416-426

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Formation of Solar Delta Active Regions： Twist and Writhe of Magnetic Ropes     

Hong-Qi ZhangNational Astronomical Observatories  Chinese Academy of Sciences  Beijing   《中国天文和天体物理学报》2004,4(6):563-577

We analyze the process of formation of delta configuration in some well-known super active regions based on photospheric vector magnetogram observations. It is found that the magnetic field in the initial developing stage of some delta active regions shows a potential-like configuration in the solar atmosphere, the magnetic shear develops mainly near the magnetic neutral line with magnetic islands of opposite polarities, and the large-scale photospheric twisted field forming gradually later. Some results are obtained: (1) The analysis of magnetic writhe of whole active regions cannot be limited in the strong field of sunspots, because the contribution of the fraction of decayed magnetic field is non-negligible. (2) The magnetic model of kink magnetic ropes, supposed to be generated in the subatmosphere, is not consistent with the evolution of large-scale twisted photospheric transverse magnetic field and not entirely consistent with the relationship with magnetic shear in some delta active regions. (3) T  相似文献   

Magnetic field evolution in accreting white dwarfs   总被引：1，自引：0，他引：1  

Andrew Cumming † 《Monthly notices of the Royal Astronomical Society》2002,333(3):589-602

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