The eruption of a quiescent prominence as observed in UV lines

We compare observations of an eruptive and a quiescent prominence in order to better understand the energetic processes in an eruptive prominence. Observations of an eruptive prominence were obtained in H, several UV emission lines (1215–1640 Å), and coronal white light at approximately 19:00 UT on September 20, 1980. The data we present shows the development of the eruption in the H and UV emission lines and is compared with the intensities from similar observations of a quiescent prominence. While the event is coincident with some coronal changes, above 1.2 and up to 1.5 solar radii, it does not result in a true coronal mass ejection event.The comparison between the eruptive and quiescent prominences reveals several differences which suggest that the activation consists not only of a mechanical movement of material, but also changes in the temperature of the prominence plasma. Some prominence material that does not seem to participate in the large scale prominence motion is heated during the eruptive event. Most of this material is heated to transition zone temperatures with almost no cool core (i.e., no or very little H emission). The behavior indicates that there are structures that are first cool and then heat up to transition zone temperatures (apparently remaining stable for some time at these temperatures). Since this is an unstable temperature region for prominence type structures the energy transport that allows this is not understood and presents an interesting theoretical problem.Member of the Carrera del Investigador, CONICET, Argentina, presently at The University of Alabama in Huntsville.     

Motions in the field of two rotating magnetic dipoles. III: Zero-velocity curves and surfaces

The zero-velocity curves and surfaces created by two parallel or antiparallel magnetic dipoles moving on concentric circles are computed. It is found that for all combinations of values of the mass parameter µ and the ratio of the magnitudes of the magnetic moments of the two dipoles, there exist closed regions inside of which charged particles are permanently trapped.     

The University of Durham Southern Hemisphere VHE gamma ray telescope

The design of very high energy (VHE) gamma ray telescopes is discussed and it is shown that a triple-mirror telescope operating in threefold fast coincidence provides an effective instrument. The design, construction and operation of a large VHE gamma ray telescope with an energy threshold of 300 GeV (at the zenith) and incorporating several novel features is described. The use of a coincidence guard ring technique is shown to result in the rejection of about 50% of the off-source (proton) events which form a high background and limit the sensitivity of such telescopes.     

Irish on the move

Trends in emigration from Ireland over time are reviewed. "During the eighteenth and nineteenth centuries overseas migration to the United States and seasonal harvest migration to Britain were the main types of movement, but over the past 100 years the Irish have developed a special affinity for settling in British towns. Although the outflow was halted for a time during the 1970s, when return migration took over, the 1980s have seen a renewal of the exodus. This time, however, the character of the flow has changed from predominantly low-skill construction and factory workers to embrace better-educated emigrants, including many graduates. This shift reflects Ireland's changing position in the international market for labour."     

Studies on post-flare loop prominence of 1981 April 27

By use of the H observations of the Astrophysical Observatory in Catania, Italy and the Purple Mountain Observatory in Nanking, China as well as hard X-ray and gamma-ray burst data from the Solar Maximum Mission (SMM) Gamma-Ray Spectrometer (GRS), a major eruptive loop prominence was studied during the limb solar flare event of 1981 April 27.Our preliminary analysis shows that there seems to exist a second abrupt energy release for this event, almost 20 min after the end of the impulsive phase of the flare. This energy release is probably associated with the rapidity in upward motion or activation of the loop prominence.A possible candidate for such a process could be the reconnection of the old magnetic field with a newly emerging magnetic field.A theoretical gross estimate for the energy release and particle acceleration has also been made in this work. It appears that the proposed model for charged particle acceleration is very efficient.     

The U.S. National 8 m telescope project

The National Optical Astronomy Observatories (NOAO) are planning to buld two 8 m telescopes, one for Mauna Kea, Hawaii, the other for a site in Chile. Optical configurations, primary mirror systems, and the telescope mounting are discussed. A new optical testing method is outlined. The system imaging goal is 0.25 FWHM. Construction could begin in the early 1990's.Paper presented at the Symposium on the JNLT and Related Engineering Developments, Tokyo, November 29–December 2, 1988.Operated by the Association of Universities for Research in Astronomy Inc., under contract with the National Science Foundation.     

Shock chemistry in the molecular clouds associated with SNR IC 443

Several interstellar molecules have been detected toward the highly perturbed B and G clouds associated with the supernova remnant IC 443 via their 3 mm transitions, including N2H+, SiO, SO, CN, HNC, and H13CO+. The (J, K) = (1, 1) and (2, 2) inversion lines of metastable ammonia have also been observed, as well as the J = 3-2 transition of HCO+ at 1.2 mm. Analysis of the (1, 1) and (2, 2) inversion lines of NH3 indicates minimum gas kinetic temperatures of TK = 70 K toward cloud B, and TK = 33 K in cloud G. Modeling of the J = 1-0 and J = 3-2 transitions of HCO+ implies densities greater than 10(5) cm-3 toward both positions. These data clearly show that hot and dense material is present in IC 443, and they suggest the presence of shocks in both regions. A careful analysis of the HCO+ lines indicates that the HCO+ abundance is at most enhanced by factors of a few over that found in cold, quiescent gas. This conclusion contradicts past claims of HCO+ abundance enhancements of several orders of magnitude in the perturbed regions. The N2H+ abundance was also found to be similar to that in cold gas, suggesting that there is no increase in ionization in the clouds. The abundances of SO and CS, as well as CN and NH3, do not appear to differ significantly from those found in cold dark clouds, although chemistry models predict sulfur-containing species to undergo high-temperature enhancements. SiO, however, is found to have an abundance in the perturbed gas 100 times larger than the upper limits observed in the dark cloud TMC 1, a result in agreement with high temperature chemistry models. In addition, the HNC/HCN ratio in both IC 443 B and G was found to be approximately 0.1--far from the ratio of 1 predicted by low-temperature ion-molecule chemistry, but similar to the values observed in clouds where elevated temperatures are present.     

Radiometry of near-earth asteroids

We report 10 micrometers infrared photometry for 22 Aten, Apollo, and Amor asteroids. Thermal models are used to derive the corresponding radiometric albedos and diameters. Several of these asteroids appear to have surfaces of relatively high thermal inertia due to the exposure of bare rock or a coarse regolith. The Apollo asteroid 3103, 1982 BB, is recognized as class E. The Jupiter-crossing Amor asteroid 3552, 1983 SA, is confirmed as class D, but low albedos remain rare for near-Earth asteroids.     

Impact-generated atmospheres over Titan, Ganymede, and Callisto

The competition between impact erosion and impact supply of volatiles to planetary atmospheres can determine whether a planet or satellite accumulates an atmosphere. In the absence of other processes (e.g., outgassing), we find either that a planetary atmosphere should be thick, or that there should be no atmosphere at all. The boundary between the two extreme cases is set by the mass and velocity distributions and intrinsic volatile content of the impactors. We apply our model specifically to Titan, Callisto, and Ganymede. The impacting population is identified with comets, either in the form of stray Uranus-Neptune planetesimals or as dislodged Kuiper belt comets. Systematically lower impact velocities on Titan allow it to retain a thick atmosphere, while Callisto and Ganymede get nothing. Titan's atmosphere may therefore be an expression of a late-accreting, volatile-rich veneer. An impact origin for Titan's atmosphere naturally accounts for the high D/H ratio it shares with Earth, the carbonaceous meteorites, and Halley. It also accounts for the general similarity of Titan's atmosphere to those of Triton and Pluto, which is otherwise puzzling in view of the radically different histories and bulk compositions of these objects.     

The latitude of filament bands at the sunspot minimum and the activity level in the two following 11-year solar cycles

The zonal structure of the distribution of filaments is considered. The mean latitudes of two filament bands are calculated in each solar hemisphere at the minima of the sunspot cycle in the period 1924–1986: middle latitude _{2, m} and low latitude _{1, m} . It is shown that the mean latitude of the filament band _{2, m} at the minimum -m of the cycle correlates, with = 0.94, with the maximum - M sunspot area S(M) and maximum Wolf number W(M) in the succeeding solar cycle M. It is shown that the mean latitude of the low-latitude filament band _{1, m} is linearly dependent on the mean latitude filament band _{2, m + 1} at the succeeding minimum. We found a correlation of the latitude of the low-latitude filament band _{1, m} with the maximum sunspot area in the M + 1 cycle. This enables us to predict the power of two succeeding 11-year solar cycles on the basis of the latitude of filament bands at the minimum of activity, 1985–1986: W(22) - 205 ± 10, W(23) - 210 ± 10. The importance of the relationships found for theory and applied aspects is emphasized. An attempt is made to interpret the relationships physically.