General relativity does not prohibit the existence of space-times that describe a time travel. Consideration of such spaces gives rise to a lot of questions and paradoxes, among which there are ...thermodynamic ones. This paper considers two situations that describe a time travel, and explains why their existence does not mean that time machines are prohibited.
We study quasiperiodic very low frequency (VLF) emissions observed simultaneously by Van Allen Probes spacecraft and Kannuslehto and Lovozero ground‐based stations on 25 December 2015. Both Van Allen ...Probes A and B detected quasiperiodic emissions, probably originated from a common source, and observed on the ground. In order to locate possible regions of wave generation, we analyze wave‐normal angles with respect to the geomagnetic field, Poynting flux direction, and cyclotron instability growth rate calculated by using the measured phase space density of energetic electrons. We demonstrate that even parallel wave propagation and proper (downward) Poynting flux direction are not sufficient for claiming observations to be in the source region. Agreement between the growth rate and emission bands was obtained for a restricted part of Van Allen Probe A trajectory corresponding to localized enhancement of plasma density with scale of 700 km. We employ spacecraft density data to build a model plasma profile and to calculate ray trajectories from the point of wave detection in space to the ionosphere and examine the possibility of their propagation toward the ground. For the considered event, the wave could propagate toward the ground in the geomagnetic flux tube with enhanced plasma density, which ensured ducted propagation. The region of wave exit was confirmed by the analysis of wave propagation direction at the ground detection point.
Key Points
Complex analysis of generation region of quasiperiodic VLF emissions were observed simultaneously by two Van Allen Probes and on the ground
Wave growth rate frequency band matched the observed emission band only in a localized (∼0.3 Earth radii) region along Van Allen Probe A trajectory
Ray tracing demonstrated the importance of a density duct for wave propagation toward the ground
Cosmic Rays from Heavy Particle Decays Arbuzova, E. V.; Dolgov, A. D.; Nikitenko, A. A.
Physics of atomic nuclei,
02/2024, Letnik:
87, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Multidimensional modification of gravity with a smaller mass scale of the gravitational interaction is considered. Stable by assumption dark matter particles could decay via interactions with virtual ...black holes. The decay rates of such processes are estimated. It is shown that with the proper fixation of the parameters the decays of these ultra-massive particles can give noticeable contribution to the flux of high energy cosmic rays in particular, near the Greisen–Zatsepin–Kuzmin limit. Such particles can also create neutrinos of very high energies observed in the existing huge underwater or ice-cube detectors.
Up from Serfdom Nikitenko, Aleksandr; Jacobson, Helen Saltz
04/2001
eBook
“It was the arbitrary nature of the serfholder’s power that weighed on serfs like Nikitenko, for as they discovered, even the most benevolent patron could turn overnight into an overbearing tyrant. ...In that respect, serfdom and slavery were the same.”—Peter Kolchin, from the foreword Aleksandr Nikitenko, descended from once-free Cossacks, was born into serfdom in provincial Russia in 1804. One of 300,000 serfs owned by Count Sheremetev, Nikitenko as a teenager became fiercely determined to gain his freedom. In this memorable and moving book, here translated into English for the first time, Nikitenko recollects the details of his childhood and youth in servitude as well as the six-year struggle that at last delivered him into freedom in 1824. Among the very few autobiographies ever written by an ex-serf, Up from Serfdom provides a unique portrait of serfdom in nineteenth-century Russia and a profoundly clear sense of what such bondage meant to the people, the culture, and the nation. Rising to eminence as a professor at St. Petersburg University, former serf Nikitenko set about writing his autobiography in 1851, relying on his own diaries (begun at the age of fourteen and maintained throughout his life), his father’s correspondence and documents, and the stories that his parents and grandparents told as he was growing up. He recalls his town, his schooling, his masters and mistresses, and the utter capriciousness of a serf’s existence, illustrated most vividly by his father’s lurching path from comfort to destitution to prison to rehabilitation. Nikitenko’s description of the tragedy, despair, unpredictability, and astounding luck of his youth is a compelling human story that brings to life as never before the experiences of the serf in Russia in the early 1800s.
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This paper is the world’s first to generalize and analyze worldwide data on the chemical composition of waters from 175 onshore mud volcanoes. Empirical probability density functions are obtained ...for the dominant anions and cations, whose average concentrations (Clarke values) were also estimated. Correlations between the geochemical parameters of the samples (Na and Cl concentrations, Na/Cl ratio and
concentration, Cl/Br ratio and Cl concentration, Cl/B ratio and
concentration, etc.) were determined and used in the further analysis of conditions under which mud volcanic waters are formed. The waters are mainly slightly alkaline, with mineralization (TDS) in the range of 5 to 25 g/L and mostly belong to the Cl–Na type (about 58%), with waters of the Cl–HCO
3
–Na (about 23%) and HCO
3
–Cl–Na (about 12%) types being less common. When mud volcanic chambers are formed, mainly connate (sedimentation–buried seawaters) waters are localized in them. The further evolution of mud volcanic waters is controlled largely by interaction in the water–rock–gas system (in the channel of the mud volcanoes). These interactions involve, first of all, the influx of CO
2
in mud volcanoes, hydrolysis of aluminosilicates, sorption–desorption from the exchange complex of clay, smectite illitization, sulfate reduction, and the precipitation of carbonate minerals. Therewith the processes of dilution (with water formed during the dehydration of clay minerals and by meteoric waters) and evaporation are demonstrated to also play important roles. An interplay of all of these processes, whose intensity varies from one mud volcano to another, determines the diversity of the chemical composition of mud volcanic waters.
An energy spectrum of electrons from 180 to 550 keV precipitating into the dayside polar ionosphere was observed under a geomagnetically quiet condition (AE ≤ 100 nT, Kp = 1‐). The observation was ...carried out at 73–184 km altitudes by the HEP instrument onboard the RockSat‐XN sounding rocket that has been launched from Andøya, Norway. The observed energy spectrum of precipitating electrons follows a power law of −4.9 ± 0.4 and the electron flux does not vary much over the observation period (∼274.4 s). A nearby ground‐based VLF receiver observation at Lovozero, Russia shows the presence of whistler‐mode wave activities during the rocket observation. A few minutes before the RockSat‐XN observation, POES18/MEPED observed precipitating electrons, which also suggest whistler‐mode chorus wave activities at the location close to the rocket trajectory. A test‐particle simulation for wave‐particle interactions was carried out using the data of the Arase satellite as the initial condition which was located on the duskside. The result of the simulation shows that whistler‐mode waves can resonate with sub‐relativistic electrons at high latitudes. These results suggest that the precipitation observed by RockSat‐XN is likely to be caused by the wave‐particle interactions between whistler‐mode waves and sub‐relativistic electrons.
Plain Language Summary
Sub‐relativistic electrons precipitating into the Earth's dayside polar ionosphere are observed by a sounding rocket under geomagnetically quiet conditions. An energy spectrum of these electrons in an energy range from 180 to 550 keV is reported at the rocket altitude. A possible mechanism for generating this precipitation is the resonance scattering of electrons by whistler‐mode waves, which we conducted a test‐particle simulation based on the ground and satellite observations.
Key Points
A sounding rocket observed an energy spectrum of sub‐relativistic electron precipitation in the dayside polar ionosphere during quiet time
Ground and satellite observations suggest that the precipitation observed by RockSat‐XN was caused by the whistler‐mode waves
A test‐particle simulation for wave‐particle interactions based on the data of the Arase satellite supports the RockSat‐XN observation
Results are presented from an analysis of auroral hiss bursts and geomagnetic pulsations recorded at the Lovozero observatory. The dynamics of the region on the Earth’s surface illuminated by the ...auroral hiss is compared to that of the aurora accompanying its occurrence. Events when hiss bursts and pulsations occur simultaneously with the emergence of an aurora or an increase in their brightness are identified. A mechanism of a possible connection between the observed phenomena is proposed on the basis of the analysis.
Population dynamics of Atlantic chub mackerel
Scomber colias
in the central-eastern Atlantic Ocean is described by the Schaefer production model using the fish abundance index as input. Developing of ...the representative species abundance index is considered as an example for a multispecies fishery prevailing in the area. A procedure for processing the daily fishing reports database is proposed, which includes an algorithm for forming a representative sample, testing the hypothesis of statistical homogeneity of observations, and standardizing the population index by the method of generalized linear models (GLM). The fishery of pelagic fish in the central-eastern Atlantic Ocean is not selective, and the seasonal spatial distribution of the species and the capacity of fishing vessels are the most significant factors of productivity. The recent catch (420 thousand tons in 2018) is a historical maximum; according to the productivity model, it approaches the estimate of the upper limit of the sustainable catch (499 thousand tons). Exceeding this target of fishing impact will inevitably lead to the overfishing and sharp reduction of the Atlantic chub mackerel population.
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