Ionization equilibrium in a highly imperfect smoke plasma

The ionization equilibrium in a heterogeneous strongly nonideal smoky plasmas containing condensed particles and an easily ionized addition of cesium atoms in the gas phase is considered. To determine the charges of particles, the nonlinear Poisson-Boltzmann equation was used, and for the ionization of atoms of the gas phase, the Saha equation taking into account the effect of the displacement of the ionization equilibrium. The dependences of the concentration of electrons and particle charges, as well as the interface between the regions of positive and negative charges of particles, on the concentration of cesium atoms and the concentration of aluminum oxide particles are obtained.

GENERAL CHARACTERIZATION AND IONIZATIONRECOMBINATION PROPERTIES OF ELECTRONEGATIVE ELEMENTS PRESENT IN PLASMA DISCHARGES AT PLASMA CURRENT SWITCH OPERATION. PART I

Based on literary sources, we present here the data on electron affinity values for a variety of negative atomic ions, and also, for some molecules and radicals being of interest for current experimental studies. Besides, the ionization potentials are given for nearly all ionization states of some electronegative elements (C, O, F, Cl). For the said elements, the ionization-recombination parameters and the dependences of the fractional values (ionic fraction) for ionization states and on the electron temperature within the framework of ionization equilibrium are given. A comparison is carried out between the calculated and experimental distributions of the fractions of multicharged C+4 ions versus electron temperature.

Discovery of recombining plasma associated with the candidate supernova remnant G189.6+3.3 with Suzaku

We present the results of an X-ray spectral analysis of the northeast region of the candidate supernova remnant G189.6+3.3 with Suzaku. K-shell lines from highly ionized Ne, Mg, Si, and S were detected in the spectrum for the first time. In addition, a radiative recombining continuum (RRC) from He-like Si was clearly seen near 2.5 keV. This detection of an RRC reveals for the first time that G189.6+3.3 possesses an X-ray-emitting recombining plasma (RP). The extracted X-ray spectrum in the 0.6–10.0 keV energy band is well fitted with a model consisting of a collisional ionization equilibrium plasma component (associated with the interstellar medium) and an RP component (associated with the ejecta). The spectral feature shows that G189.6+3.3 is most likely to be a middle-aged SNR with an RP.

Effects of density on the oxygen ionization equilibrium in collisional plasmas

ABSTRACT The ion populations most frequently adopted for diagnostics in collisional plasmas are derived from the density independent coronal approximation. In higher density, lower temperature conditions, ionization rates are enhanced once metastable levels become populated, and recombination rates are suppressed if ions recombine into Rydberg levels. As a result, the formation temperatures of ions shift, altering the diagnostics of the plasma. To accurately model the effect of ionization from metastable levels, new electron impact ionization cross-sections have been calculated for oxygen, both for direct ionization and excitation–auto-ionization of the ground and metastable levels. The results have been incorporated into collisional radiative modelling to show how the ionization equilibrium of oxygen changes once metastable levels become populated. Suppression of dielectronic recombination has been estimated and also included in the modelling, demonstrating the shifts with density in comparison to the coronal approximation. The final results for the ionization equilibrium are used in differential emission measure modelling to predict line intensities for many lines emitted by O ii–O vi in the solar transition region. The predictions show improved agreement by 15–40 per cent for O ii, O vi, and the intercombination lines of O iii–O v, when compared to results from coronal approximation modelling. While there are still discrepancies with observations of these lines, this could, to a large part, be explained by variability in the observations.

X-ray emission from the mixed-morphology supernova remnant HB 9

We present the results of a spectral analysis of the central region of the mixed-morphology supernova remnant HB 9. A prior Ginga observation of this source detected a hard X-ray component above 4 keV, and the origin of this particular X-ray component is still unknown. Our results demonstrate that the extracted X-ray spectra are best represented by a model consisting of a collisional ionization equilibrium plasma with a temperature of ∼0.1–0.2 keV (interstellar matter component) and an ionizing plasma with a temperature of ∼0.6–0.7 keV and an ionization timescale of >1 × 1011 cm−3 s (ejecta component). No significant X-ray emission was found in the central region above 4 keV. The recombining plasma model reported by a previous work does not explain our spectra.

Characterization of diffuse X-ray emission from IGR J17448$-$3232: an implication of a line-of-sight merging activity

The results of spectral analysis for the galaxy cluster IGR J17448$-$3232 are presented. The intracluster medium (ICM) in the central region ($r\lt 300^{\prime \prime }$, $320\:$kpc) has a high electron temperature plasma of $kT_{\rm e} \sim 13$–$15\:$keV, and an ionization temperature estimated from an intensity ratio of Fe xxvi Ly$\alpha /$Fe xxv He$\alpha$ lines is lower than the electron temperature, which suggests that the ICM is in the non-ionization equilibrium (NEI) state. The spectrum in the central region can be also fitted with a two-component model: a two-temperature plasma model in a collisional ionization equilibrium (CIE) with temperatures of $7.9\:$keV and $\gt 34\:$keV, or a CIE$+$power-law model with a temperature of $9.4\:$keV and a photon index of 1.1. The two-component models can represent the intensity ratio of Fe xxvi Ly$\alpha /$Fe xxv He$\alpha$ lines. On the other hand, the spectrum in the outer region ($r\gt 300^{\prime \prime }$) can be explained by a single CIE plasma model with a temperature of 5–$8\:$keV. Based on the spectral feature and its circular structure, we propose that the NEI plasma was produced by merging along the line-of-sight direction.

Signatures of the non-Maxwellian κ-distributions in optically thin line spectra

Aims. We investigated the possibility of diagnosing the degree of departure from the Maxwellian distribution using the Fe XVII–Fe XVIII spectra originating in plasmas in collisional ionization equilibrium, such as in the cores of solar active regions or microflares. Methods. The original collision strengths for excitation are integrated over the non-Maxwellian electron κ-distributions characterized by a high-energy tail. Synthetic X-ray emission line spectra were calculated for a range of temperatures and κ. We focus on the 6–24 Å spectral range to be observed by the upcoming Marshall Grazing-Incidence X-ray Spectrometer MaGIXS. Results. We find that many line intensity ratios are sensitive to both T and κ. Best diagnostic options are provided if a ratio involving both Fe XVII and Fe XVIII is combined with another ratio involving lines formed within a single ion. The sensitivity of such diagnostics to κ is typically a few tens of per cent. Much larger sensitivity, of about a factor of two to three, can be obtained if the Fe XVIII 93.93 Å line observed by SDO/AIA is used in conjuction with the X-ray lines. Conclusions. We conclude that the MaGIXS instrument is well-suited for detection of departures from the Maxwellian distribution, especially in active region cores.

Shift of ionization equilibrium in spatially confined laser induced plasma

Spatial confinement of laser-induced plasma leads to shift of ionization equilibrium and can improve determination of elements by their resonant atomic lines.