Related papers: Spectral line width decrease in the solar corona: …
Alfv\'enic waves are thought to play an important role in coronal heating and acceleration of solar wind. Here we investigated the statistical properties of Alfv\'enic waves along spicules (jets that protrude into the corona) in a polar…
We present a comprehensive model of the global properties of Alfven waves in the solar atmosphere and fast solar wind. Linear non-WKB wave transport equations are solved from the photosphere to 4 AU, and for wave periods ranging from 3…
Spectral observations of the solar transition region (TR) and corona show broadening of spectral lines beyond what is expected from thermal and instrumental broadening. The remaining non-thermal broadening is significant (5-30 km/s) and…
Solar flares are dramatic events in which magnetic reconnection in the corona leads to heating of plasma to tens of MK and acceleration of particles to high energies. They also centrally involve transport between the corona (where the…
The solar ultraviolet intensities of spectral lines originating from Li- and Na-like ions have been observed to surpass the expectations derived from plasmas with coronal approximation. The violation of the coronal approximation can be…
The Sun shrinks during solar maximum and regrows during solar minimum by a few kilometers. Here, we observe, for the first time, that the solar radius variation shows planetary relationship. This suggests that some remote planetary links…
Four decades have gone by since the discovery that the solar wind at 1 AU seems to exist in two relatively distinct states: slow and fast. There is still no universal agreement concerning the primary physical cause of this apparently…
We show that the coronal heating and the fast solar wind acceleration in the coronal holes are natural consequence of the footpoint fluctuations of the magnetic fields at the photosphere, by performing one-dimensional magnetohydrodynamical…
Many cool stars possess complex magnetic fields [1] that are considered to undertake a central role in the structuring and energising of their atmospheres [2]. Alfv\'enic waves are thought to make a critical contribution to energy transfer…
We investigate the morphology and temporal variability of a quiet Sun network region in different solar layers. The emission in several EUV spectral lines through both raster and slot time series, recorded by EIS/Hinode is studied along…
Ultraviolet spectroscopy of the extended solar corona is a powerful tool for measuring the properties of protons, electrons, and heavy ions in the accelerating solar wind. The large coronal holes that expand up from the north and south…
In the lower solar atmosphere, the chromosphere is permeated by jets known as spicules, in which plasma is propelled at speeds of 50 to 150 kilometers per second into the corona. The origin of the spicules is poorly understood, although…
This paper reports the first full-Sun vacuum ultraviolet (VUV) emission line profile originating from the transition region from the chromosphere to the corona. It is based on a raster scan of the whole solar disk using SUMER/SOHO. The…
The fast solar wind shows a wide spectrum of transverse magnetic and velocity field perturbations. These perturbations are strongly correlated in the sense of Alfv\'en waves propagating mostly outward, from the Sun to the interplanetary…
We revisit the role of longitudinal waves in driving the solar wind. We study how the the $p$-mode-like vertical oscillation on the photosphere affects the properties of solar winds under the framework of Alfv\'en-wave-driven winds. We…
The angular broadening of compact radio sources observed through a medium having turbulent density irregularities is usually estimated using the phase structure function. We employ an exact formulation for the phase structure function that…
We find evidence for the first observation of the parametric decay instability (PDI) in the lower solar atmosphere. Specifically, we find that the power spectrum of density fluctuations near the solar transition region resembles the power…
The relevance of resonant scattering (absorption by photo-excitation and re-emission out of the line of sight) in the solar corona has always been discussed controversially. Ratios of emission lines from identical ions but different…
Narrowband radio bursts with durations of the order of milliseconds, called spikes, are known to be associated with solar flares. In order to understand the particle beams responsible for the radio spike phenomena, evolution of electron…
We discuss the optical coronal line spectra observed for a sample of 19 Narrow-Line Seyfert 1 galaxies. We find no correlation between the coronal line strength and the soft X-ray power-law index derived from ROSAT PSPC data. There is a…