Modeling Grain Rotational Disruption by Radiative Torques and Extinction of Active Galactic Nuclei

Extinction curves observed toward individual Active Galactic Nuclei (AGN) usually show a steep rise toward far-ultraviolet (FUV) wavelengths and can be described by the Small Magellanic Cloud (SMC)-like dust model. This feature suggests the dominance of small dust grains of size a ≤ 0.1 μm in the local environment of AGN, but the origin of such small grains is unclear. In this paper, we aim to explain this observed feature by applying the RAdiative Torque Disruption (RATD) to model the extinction of AGN radiation from FUV to mid-infrared (MIR) wavelengths. We find that in the intense radiation field of AGN, large composite grains of size a ≥ 0.1 μm are significantly disrupted to smaller sizes by RATD up to d RATD > 100 pc in the polar direction and d RATD ∼ 10 pc in the torus region. Consequently, optical–MIR extinction decreases, whereas FUV-near-ultraviolet extinction increases, producing a steep far-UV rise extinction curve. The resulting total-to-selective visual extinction ratio thus significantly drops to R V < 3.1 with decreasing distances to AGN center due to the enhancement of small grains. The dependence of R V with the efficiency of RATD will help us to study the dust properties in the AGN environment via photometric observations. In addition, we suggest that the combination of the strength between RATD and other dust destruction mechanisms that are responsible for destroying very small grains of a ≤ 0.05 μm is the key for explaining the dichotomy observed “SMC” and “gray” extinction curve toward many AGN.

Defining the Structural Stability Field of Disordered Fluorite Oxides

Fluorite-structured oxides constitute an important class of materials for energy technologies. Despite their high level of structural symmetry and simplicity, these materials can accommodate atomic disorder without losing crystallinity, making them indispensable for uses in environments with high temperature, changing chemical compositions, or intense radiation fields. In this contribution, we present a set of simple rules that predict whether a compound may adopt a disordered fluorite structure. This approach is closely aligned with Pauling’s rules for ionic crystal structures and Goldschmidt’s rules for ionic substitution.

Low Ionosphere under Influence of Strong Solar Radiation: Diagnostics and Modeling

Solar flares (SFs) and intense radiation can generate additional ionization in the Earth’s atmosphere and affect its structure. These types of solar radiation and activity create sudden ionospheric disturbances (SIDs), affect electronic equipment on the ground along with signals from space, and potentially induce various natural disasters. Focus of this work is on the study of SIDs induced by X-ray SFs using very low frequency (VLF) radio signals in order to predict the impact of SFs on Earth and analyze ionosphere plasmas and its parameters. All data are recorded by VLF BEL stations and the model computation is used to obtain the daytime atmosphere parameters induced by this extreme radiation. The obtained ionospheric parameters are compared with results of other authors. For the first time we analyzed physics of the D-region—during consecutive huge SFs which continuously perturbed this layer for a few hours—in detail. We have developed an empirical model of the D-region plasma density and gave a simple approximative formula for electron density.

Evidence for local acceleration of heavy >10 MeV/n oxygen and sulphur in Jupiter's innermost radiation belts

&lt;p&gt;Jupiter's radiation belts constitute a multi-component system, trapping high intensities of electrons, protons and heavier ions. We revisit measurements from Galileo's Heavy Ion Counter (HIC) instrument, a high-quality dataset that extends considerably the energy range covered by Galileo/EPD and Juno/JEDI (&lt;10 MeV/n) up to ~100 MeV/n, providing key complementary observations for those two instruments in the equatorial radiation belts. Thanks to HIC's large geometry factor and event-based measurement capabilities, the instrument clearly resolves trace ions of both heliospheric and magnetospheric origin, such as Carbon, Nitrogen, Sodium, Magnesium, Iron and others, besides the much more abundant Oxygen and Sulfur. In this work we re-evaluate aspects of HIC's calibration, particularly for the analysis of measurements obtained at the innermost, intense radiation belts of Jupiter, which are currently monitored by Juno. We concentrate on previously unpublished observations from Galileo's last two orbits, reaching inward of Amalthea's orbit, including a close flyby of this moon. We show that the structure and composition of the heavy ion belts depends strongly on energy, L-shell and pitch angle. We find that above 50 MeV/n, Jupiter's heavy ion radiation belts are dominated by oxygen, appearing stable and are highly structured by strong losses at the orbits of Io, Thebe and Amalthea, a structure reminiscent of that observed in Saturn's proton radiation belts. In addition, heavy ion spectra and the corresponding phase space density profiles indicate that a local source of energy exists at least inward of Amalthea, accelerating oxygen above 100 MeV/n and sulphur above &amp;#732;50 MeV/n. Between the orbits of Io and Amalthea, PSD profiles indicate contributions from local and adiabatic acceleration for both ion species, with the former dominating at the highest energies resolved in that region (&amp;#732;50 MeV/n). In conclusion, unlike Earth's radiation belts, where the highest energy protons or ions observed reach the terrestrial magnetosphere pre-accelerated to the MeV range in the form of solar, anomalous or galactic cosmic rays, Jupiter can efficiently accelerate oxygen and sulphur, which originate at at eV energies at Io and its torus, by 7-8 decades in energy.&lt;/p&gt;

Does Hyperoxia Restrict Pyrenean Rock Lizards Iberolacerta bonnali to High Elevations?

Ectothermic animals living at high elevation often face interacting challenges, including temperature extremes, intense radiation, and hypoxia. While high-elevation specialists have developed strategies to withstand these constraints, the factors preventing downslope migration are not always well understood. As mean temperatures continue to rise and climate patterns become more extreme, such translocation may be a viable conservation strategy for some populations or species, yet the effects of novel conditions, such as relative hyperoxia, have not been well characterised. Our study examines the effect of downslope translocation on ectothermic thermal physiology and performance in Pyrenean rock lizards (Iberolacerta bonnali) from high elevation (2254 m above sea level). Specifically, we tested whether models of organismal performance developed from low-elevation species facing oxygen restriction (e.g., hierarchical mechanisms of thermal limitation hypothesis) can be applied to the opposite scenario, when high-elevation organisms face hyperoxia. Lizards were split into two treatment groups: one group was maintained at a high elevation (2877 m ASL) and the other group was transplanted to low elevation (432 m ASL). In support of hyperoxia representing a constraint, we found that lizards transplanted to the novel oxygen environment of low elevation exhibited decreased thermal preferences and that the thermal performance curve for sprint speed shifted, resulting in lower performance at high body temperatures. While the effects of hypoxia on thermal physiology are well-explored, few studies have examined the effects of hyperoxia in an ecological context. Our study suggests that high-elevation specialists may be hindered in such novel oxygen environments and thus constrained in their capacity for downslope migration.

How the space environment influences organisms: an astrobiological perspective and review

The unique environment of space is characterized by several stress factors, including intense radiation, microgravity, high vacuum and extreme temperatures, among others. These stress conditions individually or in-combination influence genetics and gene regulation and bring potential evolutionary changes in organisms that would not occur under the Earth's gravity regime (1 × g). Thus, space can be explored to support the emergence of new varieties of microbes and plants, that when selected for, can exhibit increased growth and yield, improved resistance to pathogens, enhanced tolerance to drought, low nutrient and disease, produce new metabolites and others. These properties may be more difficult to achieve using other approaches under 1 × g. This review provides an overview of the space microgravity and ionizing radiation conditions that significantly influence organisms. Changes in the genomics, physiology, phenotype, growth and metabolites of organisms in real and simulated microgravity and radiation conditions are illustrated. Results of space biological experiments show that the space environment has significant scientific, technological and commercial potential. Combined these potentials can help address the future of life on Earth, part of goal e of astrobiology.

A new look at some aspects of geometry, particle physics, inertia, radiation and cosmology

Continuing along the line of our previous report (Ter-Kazarian, 2021a), in present communication we briefly outline several closely related issues, carried out also in Byurakan Astrophysical Observatory, not touched in it for brevity reasons. These issues reveal and further develop novel aspects of the fundamental nature and structure of the space-time geometry and the high energy physics, the inertia effects, the intense radiation physics, and the notion of relative velocity in a curved space-time.