Related papers: Coronal emission lines as thermometers
Models of the solar transition region made from lines other than those of helium cannot account for the strength of the helium lines. However, the collisional excitation rates of the helium resonance lines are unusually sensitive to the…
Auroral emission lines result from the interaction between magnetic field and stellar wind, offering valuable insights into physical properties and processes occurring within magnetospheres of celestial bodies. While extensively studied in…
The problem of determination of the electron temperature t_2 in the OII zone of high-metallicity HII region was examined. It was shown that the ratio of nebular to auroral nitrogen line intensities, which is an indicator of the electron…
Cool stars on the main sequence generate X-rays from coronal activity, powered by a convective dynamo. With increasing temperature, the convective envelope becomes smaller and X-ray emission fainter. We present Chandra/HRC-I observations of…
We discuss some experimental facets of electron pair emission from surfaces using two different experimental approaches. In the first case the instrument consists of a pair of hemispherical analyzers which are operated with continuous…
Emission lines of Be-like ions are frequently observed in astrophysical plasmas, and many are useful for density and temperature diagnostics. However, accurate atomic data for energy levels, radiative rates (A-values) and effective electron…
In previous studies a very hot plasma component has been diagnosed in solar active regions through the images in three different narrow-band channels of SDO/AIA. This diagnostic from EUV imaging data has also been supported by the matching…
We discuss the role of the electron temperature in abundance determinations in ionized nebulae (planetary nebulae and giant HII regions). We show that, even when observations provide a direct estimate of Te, abundance determinations may…
Radiation emitted by unpolarized high-energy electrons penetrating crystals may be linearly polarized. This occurs when the particle velocity makes an angle, with respect to some major crystal axis, being sufficiently larger than the…
Thermoelectric power sensors used as power transfer standards are promising devices for further enhancements of the microcalorimetric technique in the high frequency field. A coaxial microcalorimeter has been studied, based on…
We review the terms, spectral radiance and spectral irradiance, and show how their precise definitions are crucial for interpreting observations made with different instruments covering widely different energy or wavelength ranges. We show…
We discuss the determination of elemental abundances from high resolution X-ray data. We emphasize the need for an accurate determination of the underlying temperature structure and advocate the use of a line ratio method which allows us to…
A vexing puzzle in the study of planetary nebulae and \ion{H}{2} regions is that the plasma diagnostic results based on collisionally excited lines systematically differ from those based on recombination lines. A fairly speculative…
We unveil the relationship existing between the temperature of an atomic ensemble of three-level atoms in a \Lambda-configuration, and the width of the emission cone of Stokes photons that are spontaneously emitted when atoms are excited by…
A differential emission measure (DEM) method is used to evaluate the relationship of the electron density and temperature before and after a coronal rain event during an active sun over the period from 20:10 UT on October 6 to 02:10 on…
Recent state-of-the-art calculations of A-values and electron impact excitation rates for Fe III are used in conjunction with the Cloudy modeling code to derive emission line intensity ratios for optical transitions among the fine-structure…
Stellar coronae have been invoked to explain the apparently extragalactic dispersion measures observed in fast radio bursts. This paper demonstrates that the suggested plasma densities would lead to deviations from the standard dispersion…
We use thermal noise induced currents to image the real and imaginary parts of the conductivity of a body. Covariances of the thermal noise currents measured at a few electrodes are shown to be related to a deterministic problem. We use the…
Even in the absence of resolved flares, the corona is heated to several million degrees. However, despite its importance for the structure, dynamics, and evolution of the solar atmosphere, the origin of this heating remains poorly…
Linearly polarized emission is described, in general, in terms of the Stokes parameters $Q$ and $U$, from which the polarization intensity and polarization angle can be determined. Although the polarization intensity and polarization angle…