ترغب بنشر مسار تعليمي؟ اضغط هنا

Magnetic and Kinetic Power Spectra as a Tool to Probe the Turbulent Dynamo

206   0   0.0 ( 0 )
 نشر من قبل Valentyna Abramenko
 تاريخ النشر 2011
  مجال البحث فيزياء
والبحث باللغة English




اسأل ChatGPT حول البحث

Generation and diffusion of the magnetic field on the Sun is a key mechanism responsible for solar activity on all spatial and temporal scales - from the solar cycle down to the evolution of small-scale magnetic elements in the quiet Sun. The solar dynamo operates as a non-linear dynamical process and is thought to be manifest in two types: as a global dynamo responsible for the solar cycle periodicity, and as a small-scale turbulent dynamo responsible for the formation of magnetic carpet in the quiet Sun. Numerous MHD simulations of the solar turbulence did not yet reach a consensus as to the existence of a turbulent dynamo on the Sun. At the same time, high-resolution observations of the quiet Sun from Hinode instruments suggest possibilities for the turbulent dynamo. Analysis of characteristics of turbulence derived from observations would be beneficial in tackling the problem. We analyse magnetic and velocity energy spectra as derived from Hinode/SOT, SOHO/MDI, SDO/HMI and the New Solar Telescope (NST) of Big Bear Solar Observatory (BBSO) to explore the possibilities for the small-scale turbulent dynamo in the quiet Sun.


قيم البحث

اقرأ أيضاً

The dipolar interaction is known to substantially affect the properties of magnetic nanoparticles. This is particularly important when the particles are kept in a fluid suspension or packed inside nano-carriers. In addition to its usual long-range na ture, in these cases the dipolar interaction may also induce the formation of clusters of particles, thereby strongly modifying their magnetic anisotropies. In this paper we show how AC susceptibility may be used to obtain important information regarding the influence of the dipolar interaction in a sample. We develop a model which includes both aspects of the dipolar interaction and may be fitted directly to the susceptibility data. The usual long-range nature of the interaction is implemented using a mean-field solution, whereas the particle-particle aggregation is modeled using a distribution of anisotropy constants. The model is then applied to two samples studied at different concentrations. One consists of spherical magnetite nanoparticles dispersed in oil and the other of cubic magnetite nanoparticles embedded on PLGA nanospheres. We also introduce a simple technique to access the importance of the dipolar interaction in a given sample, based on the height of the AC susceptibility peaks for different driving frequencies. Our results help illustrate the important effect that the dipolar interaction has in most nanoparticle samples.
We study the effect of confinement on glassy liquids using Random First Order Transition theory as framework. We show that the characteristic length-scale above which confinement effects become negligible is related to the point-to-set length-scale i ntroduced to measure the spatial extent of amorphous order in super-cooled liquids. By confining below this characteristic size, the system becomes a glass. Eventually, for very small sizes, the effect of the boundary is so strong that any collective glassy behavior is wiped out. We clarify similarities and differences between the physical behaviors induced by confinement and by pinning particles outside a spherical cavity (the protocol introduced to measure the point-to-set length). Finally, we discuss possible numerical and experimental tests of our predictions.
Solar analogs, broadly defined as stars similar to the Sun in mass or spectral type, provide a useful laboratory for exploring the range of Sun-like behaviors and exploring the physical mechanisms underlying some of the Suns most elusive processes li ke coronal heating and the dynamo. We describe a series of heliophysics-motivated, but astrophysics-like studies of solar analogs. We argue for a range of stellar observations, including (a) the identification and fundamental parameter determination of new solar analogs, and (b) characterizing emergent properties like activity, magnetism, and granulation. These parameters should be considered in the framework of statistical studies of the dependences of these observables on fundamental stellar parameters like mass, metallicity, and rotation.
By 2050, we expect that CME models will accurately describe, and ideally predict, observed solar eruptions and the propagation of the CMEs through the corona. We describe some of the present known unknowns in observations and models that would need t o be addressed in order to reach this goal. We also describe how we might prepare for some of the unknown unknowns that will surely become challenges.
التعليقات
جاري جلب التعليقات جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
mircosoft-partner

هل ترغب بارسال اشعارات عن اخر التحديثات في شمرا-اكاديميا