V.L.A. observations of flare build-up in coronal loops

Very Large Array (V.L.A.) measurements at 20 cm wavelength map emission from coronal loops with second-of-arc angular resolution at time intervals as short as 3.3 seconds. The total intensity of the 20 cm emission describes the evolution and structure of the hot plasma that is detected by satellite X-ray observations of coronal loops. The circular polarization of the 20 cm emission describes the evolution, strength and structure of the coronal magnetic field. Preburst heating and magnetic changes that precede burst emission on time scales of between 1 and 30 minutes are discussed. Simultaneous 20 cm and soft X-ray observations indicate an electron temperature $\text{T}{}_{\mathrm{e}}\textcolor{red}{}\text{2.5 × 10}{}^7\text{K}$ and electron density $\text{N}{}_{\mathrm{e}}\textcolor{red}{}\text{10}{}^{10}\text{cm}{}^{\mathrm{?3}}$ during preburst heating in a coronal loop that was also associated with twisting of the entire loop in space. We also discuss the successive triggering of bursts from adjacent coronal loops; highly polarized emission from the legs of loops with large intensity changes over a 32 MHz change in observing frequency; and apparent motions of hot plasma within coronal loops at velocities V > 2,000 kilometerspersecond.     

Acceleration theory for 5–40 keV ions at interplanetary shocks

Power-law spectra f(E)∝E^?2.7 of < 40 keV suprathermal ions within ～10⁷ km of propagating interplanetary shocks are explained by diffusive scattering near a plane shock. The theory fits the 25 November 1977 event with a mean free path perpendicular to the shock with is 0.01 AU in front of the shock and less than .0003 AU behind it, for 1 keV ions. The theory predicts a steepening spectrum at higher energies, of the form $\text{f(v)∝v}{}^{\mathrm{?4}}\text{exp(??λdv/ur)}\text{where}\text{u = (ΔV)}{}^2\text{/2V}{}_{\mathrm{W}}$ depends on the plasma velocity jump ΔV and the plasma speed V_W and mean free path λ in front of the shock     

Collisional excitation of vinylidene (H2CC)

Though H₂CO, H₂CS, H₂CCC, H₂CCCC, H₂CCO have been identified in cool interstellar molecular clouds, identification of H₂CC is still awaited. To analyze its spectrum, collisional rate coefficients are required. We have calculated collisional rate coefficients for rotational transitions between 23 levels of ortho and para H₂CC for kinetic temperatures 10, 20, 30, 40, and 50 K. The scattering problem is analyzed using the computer code MOLSCAT where the colliding partner is He atom. The interaction between H₂CC and He has been calculated with GAUSSIAN 2003. For the interaction potential obtained with GAUSSIAN 2003, MOLSCAT is used to derive the parameters q(L,M,M^′|E)$q(L\text{,}M\text{,}{M}^{\prime }|E)$ as a function of energy E   of the colliding partner. After averaging the parameters q(L,M,M^′|E)$q(L\text{,}M\text{,}{M}^{\prime }|E)$ over a Maxwellian distribution, the parameters Q(L,M,M^′|T)$Q(L\text{,}M\text{,}{M}^{\prime }|T)$ as a function of the kinetic temperature T in the cloud are obtained. Finally, the collisional rate coefficients have been calculated.     

Preliminary results of the Giotto radio science experiment

Doppler and ranging measurements using the radio signal of the GIOTTO spacecraft were taken before, during, and after the encounter with Comet Halley on $\text{13}\text{14}$ March 1986. The spacecraft velocity was found to decrease by a total of 23.3 cm s^?1 due to impacting gas and (primarily) dust in the cometary atmosphere. A preliminary dust production rate $\text{Q}{}_{\mathrm{d}}\text{? 10 × 10}{}^3\text{kg s}{}^{\mathrm{?1}}$ is found to be consistent with this deceleration. Power spectra of the carrier phase fluctuations reveal an increase in level and a flattening of the spectrum just prior to encounter, presumably associated with the enhanced dust impact rate. Finally, simulated Doppler time profiles are computed using the radial dependence of plasma density observed by the GIOTTO $\text{in situ}$ investigations. It is shown that the cometary electron content profile would have been clearly seen if a dual-frequency downlink radio configuration had been available at encounter.     

Sensitivity on nonequilibrium chemical systems to gravitational field

We note that far-from-equilibrium chemical systems can respond very sensitively to gravity. The response could be in selection of possible structures or in the formation of propagating bands. In these cases the sensitivity is characterized by the factor $\text{(E}{}_{\mathrm{g}}\text{/kT)}{}^{\mathrm{<mtext>1</mtext><mtext>n</mtext>}}$, where n=2 or 3, E_g the interaction energy, k the Boltzmann constant and T, the temperature. Also, taking the thermodynamic fluctuations into account, we obtain the theoretical limit for the minimum field strength measurable by such systems.     

Wave and plasma measurements on the Vega-1 and Vega-2 spacecraft in the environment of comet Halley

The Vega-1 and Vega-2 wave and plasma measurements performed on 6 and 9 March 1986 in the environment of comet Halley present similar characteristics. Field spectral intensity of up to $\text{5}\text{mVm}{}^{\mathrm{?1}}\text{Hz}{}^{\mathrm{?}}\text{1}\text{2}$ at 300 Hz is measured at closest approach; enhanced signals are detected in the whistler mode and in the vicinity of the lower hybrid resonance frequency within respective average distances of 130,000 km and 60,000 km from the nucleus. The plasma density rises from 100 cm^?3 at 200,000 km up to 3000 cm^?3 at 25,000 km. The spacecraft potential is of the order of +3 V beyond a distance of 200,000 km and decreases to about +0.5 V at 8,000 km.     

The chemical conditions on the parent body of the murchison meteorite: Some conclusions based on amino, hydroxy and dicarboxylic acids

Amino and hydroxy acids have been identified in the Murchison meteorite. Their presence is consistent with a synthetic pathway involving aldehydes, hydrogen cyanide and ammonia in an aqueous environment (Strecker-cyanohydrin synthesis). From the various equilibrium and rate constants involved in this synthesis, four independent estimates of the ammonium ion concentrations on the parent body at the time of compound synthesis are obtained; all values are about 2 × 10^?3 M. Succinic acid and β-alanine have also been detected in the Murchison meteorite. Their presence is consistent with a synthesis from acrylonitrile, hydrogen cyanide and ammonia. Using the equilibrium and rate constants for this synthetic pathway, and the succinic acid/β-alanine ratio measured in the Murchison meteorite, an estimate of the hydrogen cyanide concentration of 10^?3 to 10^?2 M is obtained. Since hydrogen cyanide hydrolyzes relatively rapidly in an aqueous environment ($\text{t}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{< 10}{}^4\text{yrs}$) this high concentration implies a period of synthesis of organic compounds as short as 10⁴ years on the Murchison meteorite parent body.     

The optical emission lines of type 1 X-ray bright Active Galactic Nuclei

A strong X-ray emission is one of the defining signatures of nuclear activity in galaxies. According to the Unified Model for Active Galactic Nuclei (AGN), both the X-ray radiation and the prominent broad emission lines, characterizing the optical and UV spectra of Type 1 AGNs, are originated in the innermost regions of the sources, close to the Super Massive Black Holes (SMBH), which power the central engine. Since the emission is concentrated in a very compact region (with typical size r?0.1$r?0.1$ pc) and it is not possible to obtain resolved images of the source, spectroscopic studies of this radiation represent the only valuable key to constrain the physical properties of matter and its structure in the center of active galaxies. Based on previous studies on the physics of the Broad Line Region (BLR) and on the X-ray spectra of broad (FWHM_Hβ ? 2000 km s⁻¹) and narrow line (1000 km s⁻¹ ?FWHM_Hβ ? 2000 km s⁻¹) emitting objects, it has been observed that the kinematic and ionization properties of matter close to the SMBHs are related together, and, in particular, that ionization is higher in narrow line sources. Here we report on the study of the optical and X-ray spectra of a sample of Type 1 AGNs, selected from the Sloan Digital Sky Survey (SDSS) database, within an upper redshift limit of z=0.35$z=0.35$, and detected at X-ray energies. We present analysis of the broad emission line fluxes and profiles, as well as the properties of the X-ray continuum and Fe Kα emission and we use these parameters to assess the consistency of our current AGN understanding.     

Girl — the German infrared laboratory for spacelab

GIRL is a liquid helium cooled 50 cm telescope equipped with four focal plane instruments dedicated to astronomical and aeronomical observations. These instruments, a detector array, a photopolarimeter, an Ebert-Fastie-spectrometer and a Michelson-interferometer make up an “infrared observatory” having high sensitivity and high spectral and spatial resolution. Si:Ga-, Si:Sb-, Si:As-, Si:P-, Ge:Be-, Ge:Cu- and Ge:Ga-detectors with NEP-values as low as $\text{3 10}{}^{\mathrm{?17}}\text{W Hz}{}^{\mathrm{<mtext>?1</mtext><mtext>2</mtext>}}$ have been tested and will be used to cover the wavelength range 3…120 μm. A full size “thermal model” of the GIRL cryostat containing 300 1 of superfluid helium at 1.6 K has been tested at the industrial prime contractor MBB; results of these tests will be presented in a following paper by F. Dahl et al. Several new techniques for cold telescopes are used in GIRL, for instance a glass ceramics primary mirror, a low power chopping secondary and an active helium phase separator. The scientific objectives include studies of star formation regions and active galaxies as well as measurements of spurious gases in the earth atmosphere. GIRL will be pointed by the Instrument Pointing System (IPS) and is scheduled to fly on Spacelab in 1986/87.