Sunspot penumbrae show a fine structure in continuum intensity that displays considerable dynamics. The magnetic field, in contrast, although also highly structured, has appeared to be relatively static. Here we report the discovery of inward moving magnetic enhancements in the penumbrae of two regular sunspots based on time series of SOHO/MDI magnetograms. Local enhancements of the LOS compone...

Context. The transition of the magnetic field from the ambient magnetic field to the ejecta in the sheath downstream of a coronal mass ejection (CME) driven shock is analyzed in detail. The field rotation in the sheath occurs in a two-layer structure. In the first layer, layer 1, the magnetic field rotates in the coplanarity plane (plane of shock normal and the upstream magnetic field), and in ...

Coronal mass ejections (CMEs) often present destabilization and eruption of a global (or large-scale) magnetic structure in the solar atmosphere. Furthermore, the Earth-directed CMEs are the primary driver of the disastrous space weather. Here we report on five homologous CMEs. They initiated in the early phase of five homologous X-class flares seen in NOAA Active Region 9236 on 2000 November 2...

We compute magnetic helicity and energy spectra of the solar active region NOAA 11158 during 11–15 February 2011 at 20 southern heliographic latitude using observational photospheric vector magnetograms. We adopt the isotropic representation of the Fourier-transformed two-point correlation tensor of the magnetic field. The sign of magnetic helicity turns out to be predominantly positive at all ...

It is shown that the connection of sufficiently fast flows with dynamical channels for particle escape in the Solar Corona is rather direct: it depends on their ability to deform (in specific cases to distort) the ambient magnetic field lines to temporarily stretch (shrink, destroy) the closed field lines so that the flow can escape the local region. Using a dissipative two–fluid code in which ...

The magnetic field topology at the coronal mass ejection (CME) source regions has been one of the major focuses of CME initiationmodels.While the ‘‘breakout’’ model requires a quadrupolar magnetic topology in the solar corona to enable an eruption, other models have shown that a bipolar magnetic topology can be the source region of a CME. In this paper, we use observational data and a potential...

We present a multiwavelength study of the 2005 September 13 eruption from NOAA 10808 that produced total four flares and two fast coronal mass ejections (CMEs) within ∼1.5 hours. Our primary attention is paid to the fact that these eruptions occurred in close succession in time, and that all of them were located along an S-shaped magnetic polarity inversion line (PIL) of the active region. In o...

Two sequences of solar images obtained by the Transition Region and Coronal Explorer in three UV passbands are studied using wavelet and Fourier analysis and compared to the photospheric magnetic flux measured by the Michelson Doppler Interferometer on the Solar Heliospheric Observatory to study wave behaviour in differing magnetic environments. Wavelet periods show deviations from the theoreti...

I investigate the processes at work in the cancellation of normal magnetic flux in solar magnetograms and study the relationships between cancellation and the budget of free magnetic energy in the coronal magnetic field that can power solar flares and CMEs. After defining cancellation mathematically, I derive equations that quantify the evolution of free magnetic energy in response to arbitrary...

Recent advances have made it possible to obtain two-dimensional line-of-sight magnetic field maps of the solar corona from spectropolarimetric observations of the Fe XIII 1075 nm forbidden coronal emission line. Together with the linear polarization measurements that map the azimuthal direction of the coronal magnetic field projected in the plane of the sky containing Sun center, these coronal ...