相关论文: Measuring stellar magnetic helicity density
Magnetic helicity is an invariant of ideal magnetohydrodynamics (MHD) that encodes information on the topology of magnetic field lines. It has long been appreciated that magnetic topology is an important constraint for the evolution of…
We study the stellar mass content of massive haloes in the redshift range 0.86<z<1.34, by measuring: (1) The stellar mass in the central galaxy versus total dynamical halo mass. (2) The total stellar mass (including satellites) versus total…
Magnetic fields are an important ingredient to cool star physics, and there is great interest in measuring fields and their geometry in order to understand stellar dynamos and their influence on star formation and stellar evolution. During…
We continue our attempt to connect observational data on current helicity in solar active regions with solar dynamo models. In addition to our previous results about temporal and latitudinal distributions of current helicity (Kleeorin et…
The quasilinear mean-field theory for driven MHD turbulence leads to the result that the observed cross helicity <u \cdot b> may directly yield the magnetic eddy diffusivity \eta_{T} of the quiet Sun. In order to model the cross helicity at…
The emergence of dipolar magnetic features on the solar surface is an idealization. Most of the magnetic flux emergence occurs in complex multipolar regions. Here, we show that the surface pattern of magnetic structures alone can reveal the…
We analyse a sample of over 1000 stars from 32 fields imaged in the V and I bands with the Wide Field and Planetary Camera, on board of the Hubble Space Telescope. The fields are located at Galactic latitudes | b | >= 15deg and in various…
By defining an appropriate field line helicity, we apply the powerful concept of magnetic helicity to the problem of global magnetic field evolution in the Sun's corona. As an ideal-magnetohydrodynamic invariant, the field line helicity is…
The energy of the stochastic magnetic field is bounded from below by a topological quantity expressing the degree of linkage of the field lines. When the bound is saturated one can assume that the storage of a certain magnetic energy…
In the solar corona, magnetic helicity slowly and continuously accumulates in response to plasma flows tangential to the photosphere and magnetic flux emergence through it. Analyzing this transfer of magnetic helicity is key for identifying…
Using a 3D non-linear mean-field solar dynamo model, we investigate the magnetic helicity flux and magnetic twist, and tilt parameters of bipolar magnetic regions (BMRs) emerging from the solar convection zone due to the magnetic buoyancy…
The stellar Rossby number, a dimensionless parameter quantifying the influence of Coriolis forces on convective motions, plays a pivotal role in understanding magnetic stellar evolution. In this work, we explore the connection between the…
This paper reports a blind search for magnetospheric emissions from planets around nearby stars. Young stars are likely to have much stronger stellar winds than the Sun, and because planetary magnetospheric emissions are powered by stellar…
We report in this letter our analysis of a large sample of photospheric vector magnetic field measurements. Our sample consists of 17200 vector magnetograms obtained from January 1997 to August 2004 by Huairou Solar Observing Station of the…
Stellar photometry obtained using the Hubble Space Telescope is used to study the distributions of the number densities of stars of various ages in 12 irregular and dwarf spiral galaxies viewed edge-on. Two subsystems can be distinguished…
In the solar atmosphere the twist parameter $\alpha$ has the same sign as magnetic helicity. It has been observed using photospheric vector magnetograms that negative/positive helicity is dominant in the northern/southern hemisphere of the…
A stellar evolution computer model has been used to determine changes in the luminosity L and effective temperature T(e) of single stars during their time on the main sequence. The range of stellar masses investigated was from 0.5 to 1.5…
We investigate how the observed large-scale surface magnetic fields of low-mass stars (~0.1 -- 2 Msun), reconstructed through Zeeman-Doppler imaging (ZDI), vary with age t, rotation and X-ray emission. Our sample consists of 104 magnetic…
The evolution of the magnetism, winds and rotation of low-mass stars are all linked. One of the most common ways to probe the magnetic properties of low-mass stars is with the Zeeman-Doppler imaging (ZDI) technique. The magnetic properties…
Metallicity is one of the crucial factors that determine stellar evolution. To characterize the properties of stellar populations one needs to know the fraction of stars forming at different metallicities. Knowing how this fraction evolves…