We compare the substructures of the 1997 February 07 coronal mass ejection (CME) observed near the Sun with a corresponding event in the interplanetary medium to determine the origin of magnetic clouds (MCs). We find that the eruptive prominence core of the CME observed near the Sun may not directly become a magnetic cloud as suggested by some authors and that it might instead become the ”press...

We present high-resolution studies of the solar polar magnetic elds near sunspot maximum in 1989 and towards sunspot minimum in 1995. We show that, in 1989, the polar latitudes were covered by several unipolar regions of both polarities. In 1995, however, after the polar eld reversal was complete, each pole exhibited only one dominant polarity region. Each unipolar region contains magnetic knot...

With the recent advent of the Swedish 1-m Solar Telescope (SST), advanced image processing techniques, as well as numerical simulations that provide a more realistic view of the chromosphere, a comprehensive understanding of chromospheric jets such as spicules, mottles and fibrils is now within reach. In this paper, we briefly summarize results from a recent analysis of dynamic fibrils, short-l...

It is shown that a generalized magneto–Bernoulli mechanism can effectively generate high velocity flows in the Solar chromosphere by transforming the plasma pressure energy into kinetic energy. It is found that at reasonable heights and for realistic plasma parameters, there is a precipitous pressure fall accompanied by a sharp amplification of the flow speed. Subject headings: Sun: atmosphere ...

I examine diierent aspects of the physics of mixing in stars: convection model, mixing timescales, mixing at the convective borders (overshooting), and mixing linked to a \second parameter" (rotation and related magnetic elds), in several astrophysical contexts, going from dating of open clusters to lithium destruction and production in stars.

In many situations, it is diicult to measure strong currents directly, so the currents are measured by their magnetic elds (e.g., by sensors glued onto the cable surface). If we have only one cable, then it is easy to reconstruct the current from the magnetic eld. But in many real-life situations, there is a neighboring cable whose current is also unknown. Moreover, the cables are hanging freel...

High-cadence, multiwavelength optical observations of a solar active region (NOAA 10969), obtained with the Swedish Solar Telescope, are presented. Difference imaging of white light continuum data reveals a white light brightening, 2 min in duration, linked to a co-temporal and co-spatial C2.0 flare event. The flare kernel observed in the white light images has a diameter of 300 km, thus render...

The Sun’s magnetic cycle manifests itself in an year periodic variation in the number of sunspots seen on the solar surface and a periodic reversal in the polarity of its large-scale magnetic fields. Exploring the origins of this magnetic cycle can unravel the physical mechanisms at work in the interior of magnetized stars like the Sun. Such studies are also important for understanding how the ...

We conduct comprehensive analysis of an X2.0 flare to derive quantities indicative of magnetic reconnection in solar corona by following temporally and spatially resolved flare ribbon evolution in the lower atmosphere. The analysis reveals a macroscopically distinctive two-stage reconnection (Moore et al. 2001) marked by a clear division in morphological evolution, reconnection rate, and energy...

The simplest interior magnetic field Bi that can explain the observed uniform rotation of the Sun’s radiative envelope is an axial dipole stabilized by a deep toroidal field. It can explain the uniform rotation only if confined in the polar caps. The field must be prevented from diffusing up into the high-latitude convection zone, whose slower rotation must remain decoupled from the interior. T...