Ionization Level Research Articles

First deep images catalogue of extended IPHAS PNe

ABSTRACT We present the first instalment of a deep imaging catalogue containing 58 True, Likely, and Possible extended PNe detected with the Isaac Newton Telescope Photometric H α Survey (IPHAS). The three narrow-band filters in the emission lines of H α, [N ii] λ6584 Å, and [O iii] λ5007 Å used for this purpose allowed us to improve our description of the morphology and dimensions of the nebulae. In some cases even the nature of the source has been reassessed. We were then able to unveil new macro- and micro-structures, which will without a doubt contribute to a more accurate analysis of these PNe. It has been also possible to perform a primary classification of the targets based on their ionization level. A Deep Learning classification tool has also been tested. We expect that all the PNe from the IPHAS catalogue of new extended planetary nebulae will ultimately be part of this deep H α, [N ii], and [O iii] imaging catalogue.

Comparing simulations and experiments of positive streamers in air: steps toward model validation

We compare simulations and experiments of single positive streamer discharges in air at 100 mbar, aiming toward model validation. Experimentally, streamers are generated in a plate–plate geometry with a protruding needle. We are able to capture the complete time evolution of reproducible single-filament streamers with a ns gate-time camera. A 2D axisymmetric drift-diffusion-reaction fluid model is used to simulate streamers under conditions closely matching those of the experiments. Streamer velocities, radii and light emission profiles are compared between model and experiment. Good qualitative agreement is observed between the experimental and simulated optical emission profiles, and for the streamer velocity and radius during the entire evolution. Quantitatively, the simulated streamer velocity is about 20% to 30% lower at the same streamer length, and the simulated radius is about 1 mm (20% to 30%) smaller. The effect of various parameters on the agreement between model and experiment is studied, such as the used transport data, the background ionization level, the photoionization rate, the gas temperature, the voltage rise time and the voltage boundary conditions. An increase in gas temperature due to the 50 Hz experimental repetition frequency could probably account for some of the observed discrepancies.

Estimating Dust Attenuation From Galactic Spectra. II. Stellar and Gas Attenuation in Star-forming and Diffuse Ionized Gas Regions in MaNGA

Abstract We investigate the dust attenuation in both stellar populations and ionized gas in kiloparsec-scale regions in nearby galaxies using integral field spectroscopy data from MaNGA MPL-9. We identify star-forming (H ii) and diffuse ionized gas (DIG) regions from MaNGA data cubes. From the stacked spectrum of each region, we measure the stellar attenuation, E B − V star , using the technique developed by Li et al., as well as the gas attenuation, E B − V gas , from the Balmer decrement. We then examine the correlation of E B − V star , E B − V gas , E B − V gas − E B − V star , and E B − V star / E B − V gas with 16 regional/global properties, and for regions with different Hα surface brightnesses (ΣHα ). We find a stronger correlation between E B − V star and E B − V gas in regions of higher ΣHα . The luminosity-weighted age (t L ) is found to be the property that is the most strongly correlated with E B − V star , and consequently, with E B − V gas − E B − V star and E B − V star / E B − V gas . At fixed ΣHα , log 10 t L is linearly and negatively correlated with E B − V star / E B − V gas at all ages. Gas-phase metallicity and ionization level are important for the attenuation in the gas. Our results indicate that the ionizing source for DIG regions is likely distributed in the outskirts of galaxies, while for H ii regions, our results can be well explained by the two-component dust model of Charlot & Fall.

Modelling correlated variability in accreting black holes: the effect of high density and variable ionization on reverberation lags

ABSTRACT We present a new release of the reltrans model to fit the complex cross-spectrum of accreting black holes as a function of energy. The model accounts for continuum lags and reverberation lags self-consistently in order to consider the widest possible range of X-ray variability time-scales. We introduce a more self-consistent treatment of the reverberation lags, accounting for how the time variations of the illuminating flux change the ionization level of the accretion disc. This process varies the shape of the reflection spectrum in time causing an additional source of lags besides the light crossing delay. We also consider electron densities in the accretion disc up to 1020 cm−3, which are found in most of the stellar mass black holes and in some active galactic nuclei. These high densities increase the amplitude of the reverberation lags below 1 keV since the reflection flux enhances in the same energy range. In addition, we investigate the properties of hard lags produced by variations in the power-law index of the continuum spectrum, which can be interpreted as due to roughly $3{{\ \rm per\ cent}}$ variability in the corona’s optical depth and temperature. As a test case, we simultaneously fit the lag-energy spectra in a wide range of Fourier frequency for the black hole candidate MAXI J1820+0701820 observed with NICER. The best fit shows how the reverberation lags contribute even at the longer time-scales where the hard lags are important. This proves the importance of modelling these two lags together and self-consistently in order to constrain the parameters of the system.

Investigation of the Physical Processes Involved in GNSS Amplitude Scintillations at High Latitude: A Case Study

The storm onset on 7 September 2017, triggered several variations in the ionospheric electron density, causing severe phase fluctuations at polar latitudes in both hemispheres. In addition, although quite rare at high latitudes, clear amplitude scintillations were recorded by two Global Navigation Satellite System receivers during the main phase of the storm. This work attempted to investigate the physical mechanisms triggering the observed amplitude scintillations, with the aim of identifying the conditions favoring such events. We investigated the ionospheric background and other conditions that prevailed when the irregularities formed and moved, following a multi-observations approach. Specifically, we combined information from scintillation parameters and recorded by multi-constellation (GPS, GLONASS and Galileo) receivers located at Concordia station (75.10°S, 123.35°E) and SANAE IV base (71.67°S, 2.84°W), with measurements acquired by the Special Sensor Ultraviolet Spectrographic Imager on board the Defense Meteorological Satellite Program satellites, the Super Dual Auroral Radar Network, the Swarm constellation and ground-based magnetometers. Besides confirming the high degree of complexity of the ionospheric dynamics, our multi-instrument observation identified the physical conditions that likely favor the occurrence of amplitude scintillations at high latitudes. Results suggest that the necessary conditions for the observation of this type of scintillation in high-latitude regions are high levels of ionization and a strong variability of plasma dynamics. Both of these conditions are typically featured during high solar activity.

Hygienic Assessment of the Influence of Factors of Digital Environment on Adolescents in the Process of Educational and Leisure Activities

Background: The wide use of digital tools in teaching requires a hygienic assessment of their impact on the health and lifestyle of students. The objective of the study was to assess the impact of the digital environment on the health and lifestyle of adolescents, depending on the duration of use of electronic learning tools in educational and leisure activities. Methods: An anonymous online questionnaire-based survey of 111 high school and college students was conducted to establish their screen time in the educational process, when performing homework and at leisure, as well as indicators of wellbeing and lifestyle and health complaints. In addition, learning conditions in college computer classes, such as illumination, microclimate, air ionization, levels of electromagnetic fields, airborne concentrations of phenol and formaldehyde were assessed. Modern statistical methods (Student’s t-test, chi-squared test) and methods of evidence-based medicine were applied. Results and discussion: Almost 66 % of the respondents reported using electronic teaching aids (a computer or laptop) at school three or more times a week and severer symptoms of fatigue after such classes. Complaints typical of adult professional users were not common in adolescents, except for visual impairment over the past year (48.6 %). In computer classes, microclimate parameters were far from being optimal: illumination was lower than the regulated values; the levels of electromagnetic fields, ionization, and indoor air concentrations of phenol and formaldehyde were comparable to the appropriate standard values. We observed a high involvement of adolescents in the use of digital tools at home for educational purposes and especially at leisure. The intensive use of Internet (more than 4 hours a day) was associated with frequent complaints of headaches, visual impairment, sleep disorders, and poor self-assessment of the physical shape that may be attributed to the established decreasing number of teenagers engaged in physical culture and sports. Conclusion: The length of time spent in the Internet space for homework and leisure activities affects students’ health and lifestyle. This indicates the need to develop and implement preventive and educational programs for adolescents in order to minimize health risks posed by digital environment and confirmed by outcomes of distance learning.

The Estimation of D‐Region Electron Densities From Trans‐Ionospheric Very Low Frequency Signals

AbstractDue to the relatively low ionization levels present in the D‐region of the ionosphere (60–90 km), few reliable methods exist for estimating electron densities at this altitude. Very Low Frequency (VLF, 3–30 kHz) radio waves, unlike higher frequency waves used for similar remote sensing applications, are sensitive to these low ionization levels. Much past work has addressed the estimation of D‐region electron densities using ground‐based measurements of signals originating from VLF transmitters or atmospheric lightning. We introduce a new technique for the estimation of ionospheric D‐region electron densities using satellite observations of trans‐ionospheric VLF signals originating from high‐powered VLF transmitters. Although most of the energy radiated from these transmitters is confined to sub‐ionospheric propagation modes, a small fraction penetrates the ionosphere in a right‐hand circularly polarized “whistler mode” which has been observed by many satellites. We show that the modal interference pattern previously observed enables the estimation of the electron density profile in the D‐region from a single satellite pass. Using data from the DEMETER experiment, each collection is compared with results from a validated theoretical model to select a best‐fit D‐region electron density profile. Results show expected seasonal variations and are consistent with rocket observations. Although the D‐region electron density estimates derived with this technique are shown to exhibit long‐term seasonal variations consistent with rocket and ground‐based observations, it is important to note that validation of these results remains difficult due to the lack of other techniques for continuously sensing the D‐region.

Adjusting CCIR Maps to Improve Local Behaviour of Ionospheric Models

The objective of this article is to present a concept for single-frequency Global Navigation Satellite System (GNSS) positioning local ionospheric mitigation over a certain area. This concept is based on input parameters driving the NeQuick-G algorithm (the ionospheric single-frequency GNSS correction algorithm adopted by Galileo GNSS system), estimated on a local as opposed to a global scale, from ionospheric characteristics measured by a digital ionosonde and a collocated dual-frequency Total Electron Content (TEC) monitor. This approach facilitates the local adjustment of Committee Consultative for Ionospheric Radiowave propagation (CCIR) files and the Az ionization level, which control the ionospheric electron density profile in NeQuick-G, therefore enabling better estimation of positioning errors under quiet geomagnetic conditions. This novel concept for local ionospheric positioning error mitigation may be adopted at any location where ionospheric characteristics foF2 and M(3000)F2 can be measured, as a means to enhance the accuracy of single-frequency positioning applications based on the NeQuick-G algorithm.

A study of Kollicoat® MAE100P film’s structure and properties

Generally, an organic-solvent-based film is denser and tougher than a corresponding aqueous-dispersion-based film. However, Kollicoat® MAE100P films prepared from aqueous dispersions had greater tensile strengths compared to the films cast from organic solutions. It was proposed that MAE100P polymer particles in aqueous media had a core–shell structure with a hydrophilic shell and a hydrophobic core. The hydrophilic shell was rich in ionized methacrylic acid (MAA) groups and the hydrophobic core primarily contained unionized MAA and ethyl acrylate (EA). As a result, ionized MAA formed a continuous phase which worked as a rigid frame and greatly improved the mechanical properties of aqueous-dispersion-based films. In order to prove this theory and investigate the effect of ionization level on this polymer system, the properties of pH, turbidity, zeta potential, and particle size of MAE100P dispersions were measured as a function of ionization level. The tensile strengths and thermal and mechanical properties of MAE100P films prepared from organic solution or aqueous dispersions of different ionization levels were investigated as well. FTIR was used to characterize the polymer films. Drug release in 0.1 N HCl from coated pellets was studied using the basket method. The experimental results showed that the original MAE100P polymer particles (if not specified, the ionization level is 6%) had a highly-charged surface. The properties of polymer aqueous dispersions were significantly changed by the ionization levels. Aqueous-dispersion-based MAE100P films or coats were stronger and comparable to or somewhat more effective in inhibiting drug diffusion than were organic-solvent-based coats. The tensile strength initially increased and then decreased with an increase of ionization level, while the water-uptake rate by the films continuously increased. Two endothermic peaks were observed in the DSC thermograms for cured MAE100P films. The high-Tg endothermic peak increased with an increase in ionization level, while the low-Tg peak didn’t exhibit significant change except for the 18% ionization film. In the dynamic mechanical analysis, two relaxations in the storage modulus were observed in the aqueous-dispersion-based films. These data may suggest a two-phase structure in the form of a core–shell structure. The tensile-strength ratio for aqueous-dispersion–based films over organic-solvent-based films for MAE100P was close to that reported for films formed from polymer substances/particles with core–shell structures. In summary, the core–shell structure might result in a two-phase structure in the bulk MAE100P film prepared from aqueous dispersion. This special structure led to significantly-improved mechanical properties for aqueous-dispersion-based MAE100 films. The ionization levels had complicated effects on the polymer system by increasing the amount of ionic aggregates while also solubilizing the polymer and changing the mechanism of film formation.

Spatially resolved spectroscopy across stellar surfaces

Context. High-precision stellar analyses require hydrodynamic 3D modeling. Such models predict changes across stellar disks of spectral line shapes, asymmetries, and wavelength shifts. For testing models in stars other than the Sun, spatially resolved observations are feasible from differential spectroscopy during exoplanet transits, retrieving spectra of those stellar surface segments that successively become hidden behind the transiting planet, as demonstrated in Papers I, II, and III. Aims. Synthetic high-resolution spectra over extended spectral regions are now available from 3D models. Similar to other ab initio simulations in astrophysics, these data contain patterns that have not been specifically modeled but may be revealed after analyses to be analogous to those of a large volume of observations. Methods. From five 3D models spanning Teff = 3964–6726 K (spectral types ~K8 V–F3 V), synthetic spectra at hyper-high resolution (λ/Δλ >1 000 000) were analyzed. Selected Fe I and Fe II lines at various positions across stellar disks were searched for characteristic patterns between different types of lines in the same star and for similar lines between different stars. Results. Spectral-line patterns are identified for representative photospheric lines of different strengths, excitation potentials, and ionization levels, thereby encoding the hydrodynamic 3D structure. Line profiles and bisectors are shown for various stars at different positions across stellar disks. Absolute convective wavelength shifts are obtained as differences to 1D models, where such shifts do not occur. Conclusions. Observable relationships for line properties are retrieved from realistically complex synthetic spectra. Such patterns may also test very detailed 3D modeling, including non-LTE effects. While present results are obtained at hyper-high spectral resolution, the subsequent Paper V examines their practical observability at realistically lower resolutions, and in the presence of noise.

Spatially resolved spectroscopy across stellar surfaces

Context. High-precision stellar analyses require hydrodynamic 3D modeling. Testing such models is feasible by retrieving spectral line shapes across stellar disks, using differential spectroscopy during exoplanet transits. Observations were presented in Papers I, II, and III, while Paper IV explored synthetic data at hyper-high spectral resolution for different classes of stars, identifying characteristic patterns for Fe I and Fe II lines. Aims. Anticipating future observations, the observability of patterns among photospheric lines of different strength, excitation potential and ionization level are examined from synthetic spectra, as observed at ordinary spectral resolutions and at different levels of noise. Time variability in 3D atmospheres induces changes in spectral-line parameters, some of which are correlated. An adequate calibration could identify proxies for the jitter in apparent radial velocity to enable adjustments to actual stellar radial motion. Methods. We used spectral-line patterns identified in synthetic spectra at hyper-high resolution in Paper IV from 3D models spanning Teff = 3964–6726 K (spectral types ~K8 V–F3 V) to simulate practically observable signals at different stellar disk positions at various lower spectral resolutions, down to λ/Δλ = 75 000. We also examined the center-to-limb temporal variability. Results. Recovery of spatially resolved line profiles with fitted widths and depths is shown for various noise levels, with gradual degradation at successively lower spectral resolutions. Signals during exoplanet transit are simulated. In addition to Rossiter-McLaughlin type signatures in apparent radial velocity, analogous effects are shown for line depths and widths. In a solar model, temporal variability in line profiles and apparent radial velocity shows correlations between jittering in apparent radial velocity and fluctuations in line depth. Conclusions. Spatially resolved spectroscopy using exoplanet transits is feasible for main-sequence stars. Overall line parameters of width, depth and wavelength position can be retrieved already with moderate efforts, but a very good signal-to-noise ratio is required to reveal the more subtle signatures between subgroups of spectral lines, where finer details of atmospheric structure are encoded. Fluctuations in line depth correlate with those in wavelength, and because both can be measured from the ground, searches for low-mass exoplanets should explore these to adjust apparent radial velocities to actual stellar motion.

Understanding the atmospheric properties and chemical composition of the ultra-hot Jupiter HAT-P-7b

Context. Ultra-hot Jupiters are the hottest exoplanets that have been discovered so far. They present a unique possibility to explore hot and cold chemistry on one object. The tidally locked ultra-hot Jupiter HAT-P-7b has a day-to-night temperature difference of ≃2500 K, confining cloud formation to the nightside and efficient ionisation to the dayside. Both have distinct observational signatures. Aims. We analyse plasma and magnetic processes in the atmosphere of the ultra-hot Jupiter HAT-P-7b to investigate the formation of an ionosphere and the possibility of magnetically coupling the atmospheric gas as the base for an extended exosphere. We show which ions and atoms may be used as spectral tracers, and if and where conditions for lightning may occur within the clouds of HAT-P-7b. Methods. We used 3D modelling results as input for a kinetic cloud formation code and evaluated characteristic plasma and magnetic coupling parameters. A local thermodynamical equilibrium radiative transfer was solved for the ionised gas phase. This study is confined to thermal ionisation only. Results. The ionisation throughout HAT-P-7b’s atmosphere varies drastically between day- and nightside. The dayside has high levels of thermal ionisation and long-range electromagnetic interactions dominate over kinetic electron–neutral interactions, suggesting a day–night difference in magnetic coupling. K+, Na+, Li+, Ca+, and Al+ are more abundant than their atomic counterparts on the dayside. The minimum magnetic flux density for electrons for magnetic coupling is B < 0.5 G for all regions of HAT-P-7b’s atmosphere. Conclusions. HAT-P-7b’s dayside has an asymmetric ionosphere that extends deep into the atmosphere, the nightside has no thermally driven ionosphere. A corresponding asymmetry is imprinted in the ion and neutral composition at the terminators. The ionosphere on HAT-P-7b may be directly traced by the Ca+ H&K lines if the local temperature is ≥5000 K. The whole atmosphere may couple to a global, large-scale magnetic field, and lightning may occur on the nightside.

A broad absorption line outflow associated with the broad emission line region in the quasar SDSS J075133.35+134548.3

We report on the discovery of unusual broad absorption lines (BALs) in the bright quasar SDSS J075133.35+134548.3 at z ∼ 1, using archival and newly obtained optical and NIR spectroscopic data. The BALs are detected reliably in He i* λ3889, He i* λ10830 and tentatively in Al iii, Mg ii. These BALs show complex velocity structures consisting of two major components: a high-velocity component (HV), with a blueshifted velocity range of Δv HV ∼ −9300 − −3500 km s−1, which can be reliably detected in He i* λ10830, and tentatively in Al iii and Mg ii, whereas it is undetectable in He i* λ3889 and a low-velocity component (LV), with Δ v LV ∼ −3500 − −1800 km s−1, is only detected in He i* and He i* λ10830. With the BALs from different ions, the HV outflowing gas can be constrained to have a density of n H ∼1010.3–1011.4 cm−3, a column density of N H ∼ 1021 cm−2 and an ionization parameter of U ∼10−1.83–10−1.72; inferring a distance of R HV∼0.5 pc from the central continuum source with a monochromatic luminosity λ Lλ (5100) = 7.0×1045 erg s−1 at 5100 Å. This distance is remarkably similar to that of the normal broad line region (BLR) estimated from reverberation experiments, suggesting association of the BLR and the HV BAL outflowing gas. Interestingly, a blueshifted component is also detected in Al iii and Mg ii broad emission lines (BELs), and the Al iii/Mg ii of such a BEL component can be reproduced by the physical parameters inferred from the HV BAL gas. The LV BAL gas likely has a larger column density, a higher ionization level and hence a smaller distance than the HV BAL gas. Further spectroscopy with a high S/N ratio and broader wavelength coverage is needed to confirm this to shed new light on the possible connection between BALs and BELs.

Investigation of Ionospheric Response to June 2009 Sarychev Peak Volcano Eruption

Global Navigation Satellite Systems have been extensively used to investigate the ionosphere response to various natural and man-made phenomena for the last three decades. However, ionospheric reaction to volcano eruptions is still insufficiently studied and understood. In this work we analyzed the ionospheric response to the 11–16 June 2009 VEI class 4 Sarychev Peak volcano eruption by using surrounding Russian and Japanese GPS networks. Prominent covolcanictotal electron content (TEC)ionospheric disturbances (CVIDs) with amplitudes and periods ranged between 0.03–0.15 TECU and 2.5–4.5 min were discovered for the three eruptive events occurred at 18:51 UT, 14 June; at 01:15 and 09:18 UT, 15 June 2009. The estimates of apparent CVIDs velocities vary within 700–1000 m/s in the far-field zone (300–900 km to the southwest from the volcano) and 1300–1800 m/s in close proximity toSarychev Peak. The characteristics of the observed TEC variations allow us to attribute them to acoustic mode. The south-southwestward direction is preferred for CVIDs propagation. We concluded that the ionospheric response to a volcano eruption is mainly determined by a ratio between explosion strength and background ionization level. Some evidence of secondary (F2-layer) CVIDs’ source eccentric location were obtained.

СТАНОВЛЕНИЕ И РАЗВИТИЕ СПЕЛЕОТЕРАПИИ В МИРОВОЙ ПРАКТИКЕ

Speleotherapy (ST) is a non-drug method of treatment which uses the microclimate of underground spaces. Such spaces may be represented by karst caves, salt mines, rock-salt and metal mine workings. The specific environment of underground spaces is the main factor affecting the patient's body. Speleoenvironment is formed by the combination of medical and health-improving components. Microfine salt aerosol is the main component of the speleoenvironment. It is based on the light negative ions arising at high levels of air ionization. The other components of the speleoenvironment are the constancy of the microclimate, temperature background, humidity, air flow rate. Another important factors are the absence of allergens and low bacterial contamination. Shielding effect ot the underground space, protecting from the exposure to radio-magnetic radiation is also mentioned. The main stages of the formation and development of the ST method in the world practice are also discussed in the article. Various types of speleological hospitals and the peculiarities of their geographic location are described. The factors of the speleoenvironment are presented. These factors affect the patient's body if the method is used under various conditions.

Simulation of positive streamers in CO2 and in air: the role of photoionization or other electron sources

Positive streamer discharges have been studied and modelled extensively in air. Here we study positive streamers in CO2 with and without oxygen admixtures; they are relevant for current high voltage technology as well as for discharges in the atmosphere of Venus. We discuss that no efficient photoionization mechanism is known for gases with a large CO2 fraction, as photons in the relevant energy range are rapidly absorbed. Hence positive streamers can propagate only due to some other source of free electrons ahead of the ionization front. Therefore we study positive streamer propagation in CO2 with different levels of background ionization to provide these free electrons. The effect of replacing photoionization by background ionization is studied with simulations in air. Simulating streamers in background fields of 16 to 20 kV cm−1 at standard temperature and pressure within a gap of 6.4 cm, we find that streamer propagation is rather insensitive to the level of photoionization or background ionization. We also discuss that the results depend not only on the value of breakdown field and applied electric field, and on preionization or photoionization, but also on the electron mobility μ(E) and the effective ionization coefficient α eff(E), that are gas-dependent functions of the electron energy or the electric field.

A different view of the ionospheric winter anomaly

The Winter Anomaly (WA) is an ionospheric phenomenon, particularly related to the F2-layer, that is classically defined as the situation in which the ionization level during winter is higher than during summer for a certain location. This situation is anomalous because it contradicts what would be naturally expected with summer’s ionization levels higher than winter ones. This phenomenon has been a matter of study since the early decades of the XX century.This contribution tackles the study of the WA based on long time series (up to two solar cycles) of Total Electron Content (TEC) measurements over a globally distributed network of stations. The work done relies on a threefold strategy including: a classical approach based on the comparison of the winter and summer maximum TEC values, that confirmed the results previously documented; an intermediate approach with maximum TEC values modelled as linear functions of the solar radiation level, that allowed to identify stations where the WA is likely to be observed (and at what solar radiation level) and where is not; a final original approach where the maximum TEC values are modelled using Chapman’s function for the seasonal variations, linear regressions for the solar activity dependence and the introduction of site and month dependent equivalent ionization coefficients for the remaining effects. The main conclusions are that the coefficients for winter months seem to depend mainly on geomagnetic latitude, to increase towards high latitudes and to be asymmetric between hemisphere. In accordance to these findings, the occurrences of WA effects would be regulated by proper combinations of these three effects.

On the Velocity Drift between Ions in the Solar Atmosphere

Abstract The solar atmosphere is composed of many species, which are populated at different ionization and excitation levels. The upper chromosphere, transition region, and corona are nearly collisionless. Consequently, slippage between, for instance, ions and neutral particles, or interactions between separate species, may play important roles. We have developed a 3D MFMS numerical code (Ebysus) to investigate such effects. Ebysus is capable of treating species (e.g., hydrogen, helium, etc.) and fluids (neutrals, excited and ionized elements) separately, including nonequilibrium ionization, momentum exchange, radiation, thermal conduction, and other complex processes in the solar atmosphere. Treating different species as different fluids leads to drifts between different ions and an electric field that couples these motions. The coupling for two ionized fluids can lead to an anti-phase rotational motion between them. Different ionized species and momentum exchange can dissipate this velocity drift, i.e., convert wave kinetic energy into thermal energy. High-frequency Alfvén waves driven by, e.g., reconnection thought to occur in the solar atmosphere, can drive such multi-ion velocity drifts.

Successive line-locked C iv doublets in quasar SDSS J115122.14+020426.3

ABSTRACT Rodríguez Hidalgo et al. (2013, ApJ, 775, 14) have reported the transition of a C iv mini-broad absorption line (mini-BAL) into a BAL in quasar SDSS J115122.14+020426.3 (hereafter J1151+0204). Based on the two-epoch spectra obtained from the Sloan Digital Sky Survey, we further investigate the three BAL systems (systems A, B and C) in J1151+0204. First, we confirm that the absorption-line variability in J1151+0204 is most likely caused by the change in ionization in response to the continuum variation, according to at least the following observational factors: coordinated strengthening is detected between multiple absorption troughs, and the continuum shows obvious weakening. According to photoionization simulations, asynchronized variability between the continuum and absorption lines indicates that the mini-BAL (system A) of J1151+0204 actually represents the state of a higher ionization level and lower C iv column density of the outflow, while its BAL identifies the state of a lower ionization level and higher C iv column density. Second, we find a rare case of a quintuple, which is due to four successive line-locked C iv doublets, within system C. This indicates that these outflow clouds have achieved a high degree of clumpiness, and that the radiative forces play a significant role in the acceleration process of these clumpy outflow clouds.

Ionization: a possible explanation for the difference of mean disk sizes in star-forming regions

Context. Surveys of protoplanetary disks in star-forming regions of similar age revealed significant variations in average disk mass in some regions. For instance, disks in the Orion Nebular Cluster (ONC) and Corona Australis (CrA) are on average smaller than disks observed in Lupus, Taurus, Chamaeleon I, or Ophiuchus. Aims. In contrast to previous models that studied the truncation of disks at a late stage of their evolution, we investigate whether disks may already be born with systematically smaller disk sizes in more massive star-forming regions as a consequence of higher ionization rates. Methods. Assuming various cosmic-ray ionization rates, we computed the resistivities for ambipolar diffusion and Ohmic dissipation with a chemical network, and performed 2D nonideal magnetohydrodynamical protostellar collapse simulations. Results. A higher ionization rate leads to stronger magnetic braking, and hence to the formation of smaller disks. Accounting for recent findings that protostars act as forges of cosmic rays and considering only mild attenuation during the collapse phase, we show that a high average cosmic-ray ionization rate in star-forming regions such as the ONC or CrA can explain the detection of smaller disks in these regions. Conclusions. Our results show that on average, a higher ionization rate leads to the formation of smaller disks. Smaller disks in regions of similar age can therefore be the consequence of different levels of ionization, and may not exclusively be caused by disk truncation through external photoevaporation. We strongly encourage observations that allow measuring the cosmic-ray ionization degrees in different star-forming regions to test our hypothesis.