One-to-one relationship between low latitude whistlers and conjugate source lightning discharges and their propagation characteristics

One-to-one relation with its causative lightning discharges and propagation features of night-time whistlers recorded at low-latitude station, Allahabad (geomag. lat. 16.05°N, L = 1.08), India, from continuous observations made during 1–7 April, 2011 have been studied. The whistler observations were made using the Automatic Whistler Detector (AWD) system and AWESOME VLF receiver. The causative lightning strikes of whistlers were checked in data provided by World-Wide Lightning Location Network (WWLLN). A total of 32 whistlers were observed out of which 23 were correlated with their causative lightnings in and around the conjugate location (geom. lat. 9.87°S) of Allahabad. A multi-flash whistler is also observed on 1 April with dispersions 15.3, 17.5 and 13.6 s^1/2. About 70% (23 out of 32) whistlers were correlated with the WWLLN detected causative lightnings in the conjugate region which supports the ducted mode of propagation at low latitude. The multi-flash and short whistlers also propagated most likely in the ducted mode to this station.     

Statistical study of interplanetary condition effect on geomagnetic storms: 2. Variations of parameters

We investigate the behavior of mean values of the solar wind’s and interplanetary magnetic field’s (IMF) parameters and their absolute and relative variations during the magnetic storms generated by various types of the solar wind. In this paper, which is a continuation of paper [1], we, on the basis of the OMNI data archive for the period of 1976–2000, have analyzed 798 geomagnetic storms with D _st ≤ −50 nT and their interplanetary sources: corotating interaction regions CIR, compression regions Sheath before the interplanetary CMEs; magnetic clouds MC; “Pistons” Ejecta, and an uncertain type of a source. For the analysis the double superposed epoch analysis method was used, in which the instants of the magnetic storm onset and the minimum of the D _st index were taken as reference times. It is shown that the set of interplanetary sources of magnetic storms can be sub-divided into two basic groups according to their slowly and fast varying characteristics: (1) ICME (MC and Ejecta) and (2) CIR and Sheath. The mean values, the absolute and relative variations in MC and Ejecta for all parameters appeared to be either mean or lower than the mean value (the mean values of the electric field E _y and of the B _z component of IMF are higher in absolute value), while in CIR and Sheath they are higher than the mean value. High values of the relative density variation sN/〈N〉 are observed in MC. At the same time, the high values for relative variations of the velocity, B _z component, and IMF magnitude are observed in Sheath and CIR. No noticeable distinctions in the relationships between considered parameters for moderate and strong magnetic storms were observed.     

The Solar Sail Materials (SSM) project – Status of activities

SSM (Solar Sail Materials) is an on-going project for the European Space Agency (ESA) relying on past and recent European solar sail design projects. It aims at developing and testing future technologies suitable for large, operational solar sailcrafts.     

Detonation engine fed by acetylene–oxygen mixture

The advantages of a constant volume combustion cycle as compared to constant pressure combustion in terms of thermodynamic efficiency has focused the search for advanced propulsion on detonation engines. Detonation of acetylene mixed with oxygen in various proportions is studied using mathematical modeling. Simplified kinetics of acetylene burning includes 11 reactions with 9 components. Deflagration to detonation transition (DDT) is obtained in a cylindrical tube with a section of obstacles modeling a Shchelkin spiral; the DDT takes place in this section for a wide range of initial mixture compositions. A modified ka-omega turbulence model is used to simulate flame acceleration in the Shchelkin spiral section of the system. The results of numerical simulations were compared with experiments, which had been performed in the same size detonation chamber and turbulent spiral ring section, and with theoretical data on the Chapman–Jouguet detonation parameters.     

Investigation of CME properties using the data of SDO and PROBA2 spacecraft

Formation and motion (at the initial stage) of six limb CMEs detected in the period June 2010 to June 2011 are investigated using the high-resolution data of the PROBA2 and SDO spacecraft combined with the data of SOHO/LASCO coronagraphs. It is demonstrated that several loop-like structures of enhanced brightness originate in the region of CME formation, and they move one after another with, as a rule, different velocities. These loop-like structures in the final analysis form the frontal structure of CME. Time dependences of the velocity and acceleration of the ejection’s front are obtained for all CMEs under consideration. A conclusion is drawn about possible existence of two classes of CMEs depending on their velocity time profiles. Ejections, whose velocity after reaching its maximum sharply drops by a value of more than 100 km/s and then goes over into a regime of slow change, belong to the first class. Another class of CMEs is formed by ejections whose velocity changes slowly immediately after reaching the maximum. It is demonstrated that the CME’s angular dimension increases at the initial stage of ejection motion up to a factor of 3 with a time scale of doubling the angular size value within the limits 3.5–11 min since the moment of the first measurement of this parameter of an ejection. For three CMEs it is shown that at the initial stage of their motion for a certain time interval they are stronger expanded than grow in the longitude direction.     

Survival of dormant organisms after long-term exposure to the space environment

The RF SRC—Institute of Biomedical Problems, Russian Academy of Sciences, developed Biorisk hardware to study the effects of long-term exposure of dormant forms of various organisms to outer space and used it to complete a series of experiments on the Russian Module (RM) of the International Space Station (ISS).The experiments were performed using prokaryotes (Bacillus bacteria) and eukaryotes (Penicillium, Aspergillus, and Cladosporium fungi), as well as spores, dormant forms of higher plants, insects, lower crustaceans, and vertebrates. The biological samples were housed in two containers that were exposed to outer space for 13 or 18 months. The results of the 18-month experiment showed that, in spite of harsher temperature than in the first study, most specimens remained viable.These experiments provided evidence that not only bacterial and fungal spores but also dormant forms of organisms that reached higher levels of evolutionary development had the capability to survive a long-term exposure to outer space. This observation suggests that they can be transferred on outer walls of space platforms during interplanetary missions.     

A Lunar Laser Ranging Retroreflector Array for the 21st Century

Over the past 40 years, the Lunar Laser Ranging Program (LLRP) to the Apollo Cube Corner (CCR) Retroreflector Arrays (ALLRRA) [1] has supplied almost all of the significant tests of General Relativity. The LLRP has evaluated the PPN parameters, addressed the possible changes in the gravitational constant and the properties of the self-energy of the gravitational field. In addition, the LLRP has provided significant information on the composition and origin of the moon. This is the only Apollo experiment that is still in operation. Initially the ALLRRAs contributed a negligible fraction of the ranging error budget. Over the decades, the ranging capabilities of the ground stations have improved by more than two orders of magnitude. Now, because of the lunar librations, the existing Apollo retroreflector arrays contribute a significant fraction of the limiting errors in the range measurements.The University of Maryland, as the Principal Investigator for the original Apollo arrays, is now proposing a new approach to the Lunar Laser Array technology [2]. The investigation of this new technology, with Professor Currie as Principal Investigator, is currently being supported by two NASA programs and by the INFN-LNF in Frascati, Italy. Thus after the proposed installation during the next lunar landing, the new arrays will support ranging observations that are a factor 100 more accurate than the current ALLRRAs.The new fundamental cosmological physics and the lunar physics [3] that this new Lunar Laser Ranging Retroreflector Array for the 21st Century (LLRRA-21) can provide will be described. In the design of the new array, there are three major challenges: (1) validate the ability to fabricate a CCR of the required specifications, which is significantly beyond the properties of current CCRs, (2) address the thermal and optical effects of the absorption of solar radiation within the CCR, reduce the transfer of heat from the CCR housing and (3) validate an accurate emplacement technique to install the CCR package on the lunar surface. The latter requires a long-term stable relation between the optical center of the array and the deep regolith, that is, below the thermally driven expansion and contraction of the regolith during the lunar day/night cycle.     

Thermodynamic properties of mixed fuel combustion products

In this paper, the results of calculating the processes of two fuel mixture combustion in different proportions are presented. The values of temperature, thermal capacity, specific gas constant and isentropic expansion ratio of combustion products are given. Also shown is the distinction of thermodynamic properties from the additivity law.     

Materials selection for electronic enclosures in space environment considering electromagnetic interference effect

Using low power electronic devices for space applications to reduce the mass and energy consumption has lead to electromagnetic interference (EMI) problem. Electronic enclosures are used to shield electronic devices against EMI. In the past, electromagnetic shielding has been mainly the only criteria considered in electronic enclosure design. However, there are several structural and thermal requirements for selection of shielding materials which should also be taken into account. In this research work, three quantitative materials selection methods, i.e. Digital Logic (DL), Modified Digital Logic (MDL), and Z-transformation, are employed to select the best material from among a list of candidate materials. Composite and metallic electronic enclosures are explored and the best material is selected. Z-transformation method is applicable to both of the considered case studies while DL and MDL can only be used for solving one of them. Z-transformation method ranks aluminum as the first choice among various metallic materials. The wide range of Z-transformation application and its practical results confirm the superiority of Z-transformation method over DL and MDL methods.     

Synthesizing the control system of a small gliding unmanned aerial vehicle with high-aspect ratio wing

In this paper, we consider a problem of synthesizing the control system of a small gliding (unpowered) aerial vehicle (GAV) with a high-aspect ratio wing (?? ?? 10). This wing makes it possible to increase significantly the flight range and improve the maneuvering characteristics of the aerial vehicle itself.