Related papers: Spectral line width decrease in the solar corona: …
We establish a spherically symmetric model of solar atmosphere, which consists of the whole chromosphere and low corona below the $1.25$ solar radius. It is a hydrodynamic model with heating in the chromosphere through an artificial energy…
The profiles of emission lines formed in the corona contain information on the dynamics and the heating of the hot plasma. Only recently has data with sufficiently high spectral resolution become available for investigating the details of…
The solar corona is a highly-structured plasma which can reach temperatures of more than ~2 MK. At low frequencies (decimetric and metric wavelengths), scattering and refraction of electromagnetic waves are thought to considerably increase…
We have explored the effectiveness of a longitudinal gradient in Alfv\'en speed in reducing the energy of propagating Alfv\'en waves under conditions scaled to match solar coronal holes. The experiments were conducted in the Large Plasma…
Between February 24-25, 2009, the EIS spectrometer onboard the Hinode spacecraft performed special "sit & stare" observations above the South polar coronal hole continuously over more than 22 hours. Spectra were acquired with the 1" slit…
Fine-scale structure in the corona appears not to be well resolved by current imaging instruments. Assuming this to be true offers a simple geometric explanation for several current puzzles in coronal physics, including: the apparent…
We suggest that the global torsional oscillation of solar coronal loop may be observed by the periodical variation of a spectral line width. The amplitude of the variation must be maximal at the velocity antinodes and minimal at the nodes…
An isolated, isothermal, and wide magnetic flux tube embedded either in the solar chromosphere or in the lower solar corona is considered, and the propagation of linear torsional Alfv'en waves is investigated. It is shown that the wideness…
It is now well established that the Alfv\'enic waves are ubiquitous in the solar corona. However, the Alfv\'enic wave energy estimated from the Doppler velocity measurements in the corona was found to be four orders of magnitude less than…
In the solar atmosphere, Alfv\'en waves are believed to play an important role in the transfer of energy from the photosphere to the corona and solar wind, and in the heating of the chromosphere. We perform numerical computations to…
Analyses of the widths and shifts of optically thin emission lines in the ultraviolet spectrum of the active dwarf Epsilon Eri (K2 V) are presented. The spectra were obtained using the Space Telescope Imaging Spectrograph on the Hubble…
Registering periodic variations of spectral line widths serves as the main method for observing torsional Alfv\'{e}n waves. Theoretically, the method seems valid, yet it entails a number of caveats when applied to data. For instance, the…
Solar energetic transients occurring in solar atmosphere are associated with catastrophic release of energy in the solar corona. These transients inject a part of their energy by various physical processes to the deeper, denser photospheric…
We solve the problem of propagation and dissipation of Alfvenic turbulence in a model solar atmosphere consisting of a static photosphere and chromosphere, transition region, and open corona and solar wind, using a phenomenological model…
We present an analysis of several Hinode EIS observations of coronal line widths in the quiet Sun, up to 1.5 Rsun radial distances. No significant variations are found, which indicates no damping of Alfv\'en waves in the quiescent corona.…
Using Hinode EUV Imaging Spectrometer (EIS) spectra recorded daily at Sun center from the end of 2006 to early 2011, we studied the long-term evolution of the quiet corona. The light curves of the higher temperature emission lines exhibit…
High resolution spectra from the Hinode EUV Imaging Spectrometer (EIS) have revealed that coronal spectral line profiles are sometimes asymmetric, with a faint enhancement in the blue wing on the order of 100 km/s. These asymmetries could…
The tenuous supersonic solar wind that streams from the top of the corona passes through a natural boundary -- the Alfv\'en surface -- that marks the causal disconnection of individual packets of plasma and magnetic flux from the Sun…
We study a model of an accretion disc surrounded by an extended corona of the temperature 10^7 - 10^8 K. This corona modifies the disk spectrum since it redirects a significant fraction of the emission from the central parts towards the…
Solar radio spikes are short duration and narrow bandwidth fine structures in dynamic spectra observed from GHz to tens of MHz range. Their very short duration and narrow frequency bandwidth are indicative of sub-second small-scale energy…