Spectroscopic study of plasma parameters for solar active regions and flares

Results are given of the study of active regions and flares by a high resolution Mg XI ion spectra obtained aboard rockets and a satellite. It is shown that there is a noticable similarity in the physical conditions in the plasma of active regions and flares. Plasma of both sources consists okf a thermal component with the temperature T ～ 2.?3.10⁶K for active regions and T ～ 1.5?2.5.10⁷K for flares and in both cases of a relatively small number (～ 1–5%) of suprathermal electrons with an energy E ～ 3–6 kT.     

Particle and Joule heating of the neutral polar thermosphere in cusp region using Atmosphere Explorer-C satellite measurements

Simultaneous measurements taken by instruments on the Atmosphere Explorer - C satellite were used to compare electron and proton particle energy deposition, Joule heating, and neutral density perturbations in the region of the cusp.Altitude profiles of Joule heating, electron energy deposition, and electron density are derived using measurements taken by the satellite as input to a computer model. Electric fields are calculated using ion drift measurements. Figures are presented for a representative orbital pass.A peak Joule heating rate of 0.059 Wm^?2 occurred in the cusp region with a peak of 0.025 Wm^?2 in the evening auroral electrojet. Peak volume heating rates corresponding to these regions were 1.4 × 10^?6Wm^?3 and 7.10^?7 Wm^?3, both occurring at an altitude of 115 km. Particle energy deposition was about an order of magnitude less than Joule heating. Large neutral density perturbations are related to regions of heating.     

Identification of specific gravity sensitive signal transduction pathways in human A431 carcinoma cells.

Epidermal growth factor (EGF) activates a well characterized signal transduction cascade in human A431 epidermoid carcinoma cells. The influence of gravity on EGF-induced EGF-receptor clustering and early gene expression as well as on actin polymerization and actin organization have been investigated. Different signalling pathways induced by the agents TPA, forskolin and A23187 that activate gene expression were tested for sensitivity to gravity. EGF-induced c-fos and c-jun expression were decreased in microgravity. However, constitutive beta-2 microglobulin expression remained unaltered. Under simulated weightlessness conditions EGF- and TPA-induced c-fos expression was decreased, while forskolin- and A23187-induced c-fos expression was independent of the gravity conditions. These results suggest that gravity affects specific signalling pathways. Preliminary results indicate the EGF-induced EGF-receptor clustering remained unaltered irrespective of the gravity conditions. Furthermore, the relative filamentous actin content of steady state A431 cells was enhanced under microgravity conditions and actin filament organization was altered. Under simulated weightlessness actin filament organization in steady state cells as well as in EGF-treated cells was altered as compared to the 1 G reference experiment. Interestingly the microtubule and keratin organization in untreated cells showed no difference with the normal gravity samples. This indicates that gravity may affect specific components of the signal transduction circuitry.     

Marangoni convection in a liquid layer under the simultaneous action of a transverse magnetic field and rotation

Asymptotic stability characteristics with respect to the onset of Marangoni convection in a liquid layer under the simultaneous action of a large transverse magnetic field and a large rate of rotation are investigated. In certain parameter ranges there is a decrease in critical Marangoni number for increasing magnetic field and rotation depending on the coupling between interfacial perturbations and rotation.     

A review of long drop tubes as a supplement/alternative to space experiments

The 100 meter high drop tube at the Marshall Space Flight Center has proven to be a viable facility for studies of containerless solidification. Advantages are that experiments are inexpensive and large numbers of specimens can be processed rapidly. It would not be unusual to run ten specimens in a day. Another significant advantage is that the undercooling behavior can be followed with sufficient sensitivity to easily detect the onset of recalescence and subsequent events.Disadvantages are the restrictions on specimen sizes and types of alloys that can be run in a microgravity environment. Practical specimen sizes range between 50 mg and 500 mg depending on the type of furnace being used. Refractory alloys can be processed in a vacuum (about 10^?5 torr) and therefore at microgravity. Non-refractory alloys demand an atmosphere (about 200 torr) to obtain appreciable undercooling before impact at the bottom of the tube. Under these conditions significant g forces result.Because of the present limitations of the 100 meter drop tube, the most definitive work has been done on niobium based alloys. Large amounts of undercooling have been observed routinely and the effects of undercooling on microstructure have been characterized in detail. X-ray diffraction, scanning electron microscopy, and transmission electron microscopy have been used to determine types of phases, amounts of phases, and compositions of phases. It is clear, as would be expected, that the results bear some resemblance to rapid solidification processing by quenching. However, there are dissimilarities due to the uniqueness of solidification by deep undercooling without quenching in long drop tubes and accompanying recalescence effects.     

IR-spectroscopy of ionosphere from stratospheric balloons

The radiation spectra of the ionosphere in the 4–5 μm region have been determined from stratospheric balloons by means of the specially elaborated method of the registration of angular and spectral distribution of the radiation. The radiation bands of 4.4 μm and 4.8 μm which have 0.1–0.2 erg cm^?2 sr^?1s^?1. brightness obtained in two flights, are identified with the vibration-rotation transitions of the ion NO⁺ (0 - 1) and the molecules N¹⁴N¹⁵ (0 - 1) and CO (0 - 1) and (3 - 2) from altitudes between 120 and 500 km.     

Vertical profiles of halocarbons in the stratosphere

Stratospheric air samples collected between 10 and 35 km altitude my means of a cryogenic sampler were analyzed by gaschromatography. Thus vertical profiles of source gases for halogen radicals were derived, such as CCl₄, CCl₃F, CCl₂F₂, CClF₃, CF₄, C₂F₃Cl₃, C₂F₄Cl₂, C₂F₅Cl, C₂F₆, CH₃Cl, CH₃CCl₃, CHF₂Cl, CH₃Br, CBrF₃, and CBrCl₂F. Systematic discrepancies between measured and modelled halocarbon profiles point to deficiencies of present one- and two-dimensional models. Measurements of fully halogenated hydrocarbons provide a tool for systematically studying these deficiencies and thus improving the models.     

Coding for Ambiguity Reduction in Pulsed Scanning Systems

A technique for suppressing the ambiguities arising in pulsed scanning systems is described. A system of multiple antennas is employed, and a coded sequence of pulses is radiated.     

ELF radio signals produced in the auroral ionosphere by non-linear demodulation of signals from high-power amplitude-modulated transmitters

ELF and VLF radio signals were recorded in the afternoon to early morning (local time) between 24 March and 4 April 1979, in Northern Scandinavia. Apart from signals of natural origin, timing signals, i.e. six pips of equal duration of 105 ± 8 ms, at 1 kHz ± 0.5 Hz, were observed on the hour UT. Such signals only occur on days of relatively high geomagnetic activity during enhanced auroral electrojet activity. They are believed to be generated by non-linear demodulation (self-detection) of signals from two or more amplitude modulated transmitters in the USSR, operating at 173, 200, 236, 263 and 657 kHz. The simplest explanation for the observations is provided by the three transmitters operating at 173 kHz.