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A new model describing the transport and evolution of turbulence in the quiet solar corona is presented. In the low plasma beta environment, transverse photospheric convective fluid motions drive predominantly quasi-2D (nonpropagating) turbulence in the mixed-polarity “magnetic carpet,” together with a minority slab (Alfvénic) component. We use a simplified sub-Alfvénic flow velocity profile to solve transport equations describing the evolution and dissipation of turbulence from (including the Alfvén surface). Typical coronal base parameters are used, although one model uses correlation lengths derived observationally by Abramenko et al., and the other assumes values 10 times larger. The model predicts that (1) the majority quasi-2D turbulence evolves from a balanced state at the coronal base to an imbalanced state, with outward fluctuations dominating, at and beyond the Alfvén surface, i.e., inward turbulent fluctuations are dissipated preferentially; (2) the initially imbalanced slab component remains imbalanced throughout the solar corona, being dominated by outwardly propagating Alfvén waves, and wave reflection is weak; (3) quasi-2D turbulence becomes increasingly magnetized, and beyond , the kinetic energy is mainly in slab fluctuations; (4) there is no accumulation of inward energy at the Alfvén surface; (5) inertial range quasi-2D rather than slab fluctuations are preferentially dissipated within ; and (6) turbulent dissipation of quasi-2D fluctuations is sufficient to heat the corona to temperatures K within , consistent with observations that suggest that the fast solar wind is accelerated most efficiently between . [ABSTRACT FROM AUTHOR]

We examine the turbulent relaxation of solar coronal loops containing non-trivial field line braiding. Such field line tangling in the corona has long been postulated in the context of coronal heating models. We focus on the observational signatures of energy release in such braided magnetic structures using MHD simulations and forward modeling tools. The aim is to answer the following question: if energy release occurs in a coronal loop containing braided magnetic flux, should we expect a clearly observable signature in emissions? We demonstrate that the presence of braided magnetic field lines does not guarantee a braided appearance to the observed intensities. Observed intensities may—but need not necessarily—reveal the underlying braided nature of the magnetic field, depending on the degree and pattern of the field line tangling within the loop. However, in all cases considered, the evolution of the braided loop is accompanied by localized heating regions as the loop relaxes. Factors that may influence the observational signatures are discussed. Recent high-resolution observations from Hi-C have claimed the first direct evidence of braided magnetic fields in the corona. Here we show that both the Hi-C data and some of our simulations give the appearance of braiding at a range of scales. [ABSTRACT FROM AUTHOR]

We demonstrate the trapping of cold atoms in a toroidal geometry using a radio frequency (rf) dressed quadrupole magnetic trap formed by superposing a strong rf-field on a quadrupole trap. This rf-dressed quadrupole trap has the minimum potential away from the quadrupole trap centre on a circular path which facilitates trapping in toroidal geometry. In these experiments, the laser cooled atoms were first trapped in a quadrupole trap, then cooled evaporatively using a weak rf-field, and finally trapped in an rf-dressed quadrupole trap. The radius of the toroid could be varied by varying the frequency of the dressing rf-field. It has also been demonstrated that a single rf source and an antenna can be used for the rf-evaporative cooling as well as for the rf-dressing of atoms. The atoms trapped in the toroidal trap may have applications in the realization of an atom gyroscope as well as in studying the quantum gases in low dimensions. [ABSTRACT FROM AUTHOR]