Vertical plasma transport in the ionosphere over Irkutsk during St. Patrick’s Day geomagnetic storm: Observations and modeling

The St. Patrick’s Day storm being the strongest geomagnetic storm of Solar Cycle 24 caused strong changes in ionospheric and thermospheric dynamics. The paper presents a study of vertical plasma transport in the ionosphere during the St. Patrick’s Day storm with using both observations and modeling. The observations give the ionospheric peak height obtained with the chirp vertical sounding ionosonde and the neutral wind velocities obtained with the Fabry-Perot interferometer. The ionospheric peak height is an indicator of the total vertical plasma transport, while meridional wind and electromagnetic drift are the two main drivers of the vertical plasma transport. The Global Self-consistent Model of the Thermosphere, Ionosphere, and Protonosphere used in this study gives the total set of ionospheric and thermospheric parameters including F2-layer peak height, neutral wind velocities, electric field, and neutral composition. The model/data comparison allows us to obtain two main results. The first one is an estimation of the model prediction possibilities under storm conditions. The second result is an indirect assessment of the neutral wind and electric field contribution into the changes in the ionospheric peak height in the case of the St. Patrick’s Day geomagnetic storm.     

Ion Acceleration at the Earth’s Bow Shock

The Earth’s bow shock is the most studied example of a collisionless shock in the solar system. It is also widely used to model or predict the behaviour at other astrophysical shock systems. Spacecraft observations, theoretical modelling and numerical simulations have led to a detailed understanding of the bow shock structure, the spatial organization of the components making up the shock interaction system, as well as fundamental shock processes such as particle heating and acceleration. In this paper we review the observations of accelerated ions at and upstream of the terrestrial bow shock and discuss the models and theories used to explain them. We describe the global morphology of the quasi-perpendicular and quasi-parallel shock regions and the foreshock. The acceleration processes for field-aligned beams and diffuse ion distribution types are discussed with connection to foreshock morphology and shock structure. The different possible mechanisms for extracting solar wind ions into the acceleration processes are also described. Despite several decades of study, there still remain some unsolved problems concerning ion acceleration at the bow shock, and we summarize these challenges.     

Topics in Microphysics of Relativistic Plasmas

Astrophysical plasmas can have parameters vastly different from the more studied laboratory and space plasmas. In particular, the magnetic fields can be the dominant component of the plasma, with energy-density exceeding the particle rest-mass energy density. Magnetic fields then determine the plasma dynamical evolution, energy dissipation and acceleration of non-thermal particles. Recent data coming from astrophysical high energy missions, like magnetar bursts and Crab nebula flares, point to the importance of magnetic reconnection in these objects. In this review we outline a broad spectrum of problems related to the astrophysical relevant processes in magnetically dominated relativistic plasmas. We discuss the problems of large scale dynamics of relativistic plasmas, relativistic reconnection and particle acceleration at reconnecting layers, turbulent cascade in force-fee plasmas. A number of astrophysical applications are also discussed.     

Structural assessment of a solid propellant rocket motor: Effects of aging and damage

The aim of this study is to perform structural analysis of a solid propellant rocket motor using the finite element method and to determine the effects of aging on the analysis results. Thermal and pressure loadings occurring during the shipping, storing and firing are considered to be the most critical in determining long-term behavior of the motor. Stress and strain distribution in the rocket motor under these loading conditions are determined. Maximum hoop strain at the surface of the propellant and bond stresses at the interface between the liner and the insulator are evaluated as indicators of cracking in the propellant grain and debonding at the liner–insulator interface. The analyses are performed for both unaged and aged propellants. The results can be used to estimate the service life of the motor.     

Influence of altered gravity on the cytochemical localization of cytochrome oxidase activity in central and peripheral gravisensory systems in developing cichlid fish.

Cichlid fish larvae were reared from hatching to active free swimming under different gravity conditions: natural environment, increased acceleration in a centrifuge, simulated weightlessness in a clinostat and near weightlessness during space flight. Cytochrome oxidase activity was analyzed semiquantitatively on the ultrastructural level as a marker of regional neuronal activity in a primary, vestibular brainstem nucleus and in gravity receptive epithelia in the inner ear. Our results show, that gravity seems to be positively correlated with cytochrome oxidase activity in the magnocellular nucleus of developing fish brain. In the inner ear the energy metabolism is decreased under microgravity concerning utricle but not saccule. Hypergravity has no effect on cytochrome oxidase activity in sensory inner ear epithelia.     

Heavy ion induced double strand breaks in bacteria and bacteriophages.

DNA damage induced by heavy ions in bacterial cells and bacteriophages such as Bacillus subtilis, E. coli and Bacteriophage T1 were investigated by analyzing the double strand breaks in the chromosomal DNA. This kind of lesion is considered as one of the main reasons for lethal events. To analyze double strand breaks in long molecules of DNA--up to some Mbp in length--the technique of pulse field agarose gel electrophoresis has been used. This allows the detection of one double strand break per genome. Cell lysis and DNA isolation were performed in small agarose blocks directly. This procedure secured minimum DNA destruction by shearing forces. After running a gel, the DNA was stained with ethidium bromide. The light intensity of ethidium bromide fluorescence for both the outcoming (running) DNA and the remaining intact DNA were measured by scanning. The mean number of double strand breaks was calculated by determining the quotient of these intensities. Strand break induction after heavy ion and X-ray irradiation was compared.     

Generation mechanisms of the ELF-ULF waves related to the flux transfer events

Satellite observations near the magnetopause and within the magnetosheath revealed the existence of some structures characterised by specific magnetic field and plasma signatures. They have been called “Flux Transfer Events”. One of the models of FTEs is a reconnected fluxtube, extending from the inner magnetosphere into the magnetosheath. ELF-ULF waves are often observed in together with other FTE's signatures. Wideband emissions are associated with the boundaries of FTEs with characteristic maxima at lower hybrid and ion-cyclotron frequencies. They provide a tool for better timing of the events. These emissions might also be related to the reconnection process. Observations of FTE's by Prognoz-8 satellite are presented in our paper. Wave signatures of the FTEs are described. Various mechanisms of generation of the emissions by instabilities depending on local plasma conditions are discussed along with non-local aspects of such waves. Numerical solutions of the dispersion equation for the typical conditions in FTEs are presented. Possible relation of these waves to the reconnection process are discussed.     

Temporal evolution of statistical features of the sunspot cycles

Analysis of the general statistical features of the sunspot cycles in the period 1700–1996 AD, including the Gnevyshev–Ohl rule, Waldmeier rule and an amplitude–period effect, was performed for both Wolf numbers and group sunspot numbers. It was shown that for both solar indices all the statistical effects are weaker over the time interval 1700–1855 AD than over the time interval 1856–1996 AD. Possible causes of this difference are discussed.     

Efficient multi-response adaptive sampling algorithm for construction of variable-fidelity aerodynamic tables

Adaptive sampling is an iterative process for the construction of a global approximation model. Most of engineering analysis tools computes multiple parameters in a single run. This research proposes a novel multi-response adaptive sampling algorithm for simultaneous construction of multiple surrogate models in a time-efficient and accurate manner. The new algorithm uses the Jackknife cross-validation variance and a minimum distance metric to construct a sampling criterion function. A weighted sum of the function is used to consider the characteristics of multiple surrogate models. The proposed algorithm demonstrates good performance on total 22 numerical problems in comparison with three existing adaptive sampling algorithms. The numerical problems include several two-dimensional and six-dimensional functions which are combined into singleresponse and multi-response systems. Application of the proposed algorithm for construction of aerodynamic tables for 2 D airfoil is demonstrated. Scaling-based variable-fidelity modeling is implemented to enhance the accuracy of surrogate modeling. The algorithm succeeds in constructing a system of three highly nonlinear aerodynamic response surfaces within a reasonable amount of time while preserving high accuracy of approximation.     

Partially Ionized Plasmas in Astrophysics

Partially ionized plasmas are found across the Universe in many different astrophysical environments. They constitute an essential ingredient of the solar atmosphere, molecular clouds, planetary ionospheres and protoplanetary disks, among other environments, and display a richness of physical effects which are not present in fully ionized plasmas. This review provides an overview of the physics of partially ionized plasmas, including recent advances in different astrophysical areas in which partial ionization plays a fundamental role. We outline outstanding observational and theoretical questions and discuss possible directions for future progress.