Related papers: Deriving the Coronal Hole Electron Temperature: El…
We consider the deconvolution of the thermal and the turbulent profiles for a pair of ions with different atomic weights under the condition that the lines are formed in an absorbing medium with fluctuating density and velocity fields. Our…
The temperature of the solar atmosphere increases from thousands to millions of degrees moving from the lower layer (chromosphere) to the outermost one (corona), while the density drops accordingly. The mechanism behind this phenomenon,…
Images taken in the band centered at 30.4 nm are routinely used to map the radiance of the He II Ly alpha line on the solar disk. That line is one of the strongest, if not the strongest, line in the EUV observed in the solar spectrum, and…
Daily differential emission measure (DEM) distributions of the solar corona are derived from spectra obtained by the Extreme-ultraviolet Variability Experiment (EVE) over a 4-year period starting in 2010 near solar minimum and continuing…
The question why the solar corona is much hotter than the visible solar surface still puzzles solar researchers. Most theories of the coronal heating involve a tight coupling between the coronal magnetic field and the associated thermal…
X-ray and EUV observations are an important diagnostic of various plasma parameters of the solar atmosphere during solar flares. Soft X-ray and EUV observations often show coronal sources near the top of flaring loops, while hard X-ray…
The high-speed solar wind is typically the simplest and least stochastic type of large-scale plasma flow in the heliosphere. For much of the solar cycle, it is connected magnetically to large polar coronal holes on the Sun's surface.…
Accreting black holes in galactic X-ray sources are surrounded by hot plasma. The innermost part of these systems is likely a corona with different temperatures for ions and electrons. In the so-called low-hard state, hot electrons…
Context: The sharp temperature and density gradients in the coronal transition region are a challenge for models and observations. Aims: We set out to get linearly- and quadratically-weighted average electron densities in the region…
Observations with {\em RHESSI} have enabled the detailed study of the structure of dense hard X-ray coronal sources in solar flares. The variation of source extent with electron energy has been discussed in the context of streaming of…
We study a series of relations between physical parameters in coronal loops of the quiet Sun reconstructed by combining tomographic techniques and modeling of the coronal magnetic field. We use differential emission measure tomography…
Coronal holes are the darkest and least active regions of the Sun, as observed both on the solar disk and above the solar limb. Coronal holes are associated with rapidly expanding open magnetic fields and the acceleration of the high-speed…
Recent spectroscopic models of active galactic nuclei (AGN) have indicated that the recommended electron-ion recombination rate coefficients for iron ions with partially filled M-shells are incorrect in the temperature range where these…
The dielectronic recombination rate coefficients of N V and Ne VIII ions have been measured at a heavy-ion storage ring. The investigated energy ranges covered all dielectronic recombination resonances attached to 2s -> 2p (Delta n=0) core…
We present analyses of observations of epsilon Eridani (K2 V) made with the Low Energy Transmission Grating Spectrometer on Chandra and the Extreme Ultraviolet Explorer, supplemented by observations made with the Space Telescope Imaging…
We study the evolution of ultracold plasmas by measuring the electron temperature. Shortly after plasma formation, competition between heating and cooling mechanisms drives the electron temperature to a value within a narrow range…
We analyzed a coronal loop observed with the Normal Incidence Spectrometer (NIS), which is part of the Coronal Diagnostic Spectrometer (CDS) on board the Solar and Heliospheric Observatory (SOHO). The measured Doppler shifts and proper…
Dielectronic recombination (DR) of xenonlike W20+ forming W19+ has been studied experimentally at a heavy-ion storage-ring. A merged-beams method has been employed for obtaining absolute rate coefficients for electron-ion recombination in…
Cosmic rays are an important source of heating in the interstellar medium, in particular in dense molecular cloud cores shielded from the external ultraviolet radiation field. The limits placed on the cosmic-ray ionization rate from…
In observations of flare-heated electrons in the solar corona, a longstanding problem is the unexplained prolonged lifetime of the electrons compared to their transit time across the source. This suggests confinement. Recent…