The ideal helical kink instability of a force-free coronal magnetic flux rope, anchored in the photosphere, is studied as a model for solar eruptions. Using the flux rope model of Titov & Démoulin (1999) as the initial condition in MHD simulations, both the development of helical shape and the rise profile of a confined (or failed) filament eruption (on 2002 May 27) are reproduced in excellent ...

We investigate the emergence of magnetic flux in the quiet Sun at very small spatial scales, focusing on the magnetic connection between the photosphere and chromosphere. The observational data consist of spectropolarimetric measurements and filtergrams taken with the Hinode satellite and the Dutch Open Telescope. We find that a significant fraction of the magnetic flux present in internetwork ...

The solar wind carries magnetic flux from the photosphere into the heliosphere, making it topologically open in the corona. Open magnetic flux is unevenly distributed at the solar surface, but at some distance in the outer corona it becomes uniformly distributed and approximately radial. Standard potential field models do not provide such uniform distribution of open flux in the heliosphere. A ...

The upper atmosphere of the Sun is governed by the complex structure of the magnetic field. This controls the heating of the coronal plasma to over a million kelvin. Numerical experiments in the form of three-dimensional magnetohydrodynamic simulations are used to investigate the intimate interaction between magnetic field and plasma. These models allow one to synthesize the coronal emission ju...

We use limb synoptic plots to study long-lived features of the lower solar corona. The most persistent features are the polar sinusoids, which are generated by streamers associated with active regions. We Ðnd that the lifetimes of these structures (up to about 10 solar rotations) are much longer than the lifetimes of individual sunspots (typically less than one solar rotation). The long lifetim...

The Sun’s corona is millions of degrees hotter than its 5,000 K photosphere. This heating enigma is typically addressed by invoking the deposition at coronal heights of non-thermal energy generated by the interplay between convection and magnetic field near the photosphere. However, it remains unclear how and where coronal heating occurs and how the corona is filled with hot plasma. We show tha...

We adopt an isotropic representation of the Fourier-transformed two-point correlation tensor of the magnetic field for estimating magnetic energy and helicity spectra as well as current helicity spectra of individual active regions and the change of their spectral indices with the solar cycle. The departure of the spectral index of current helicity from 5/3 is analyzed, and it is found that it ...

A proxy for horizontal electric currents in the solar photosphere was suggested. For a set of evolving active regions (ARs) observed with Solar and Heliospheric Observatory (SOHO) Michelson Doppler Imager (MDI) in the high resolution mode, the dissipation spectrum, kE(k), and the spatial structure of dissipation, i.e., the Stokes dissipation function ε(x, y), were calculated from the observed B...