Collisional and Radiative Processes in Optically Thin Plasmas

Most of our knowledge of the physical processes in distant plasmas is obtained through measurement of the radiation they produce. Here we provide an overview of the main collisional and radiative processes and examples of diagnostics relevant to the microphysical processes in the plasma. Many analyses assume a time-steady plasma with ion populations in equilibrium with the local temperature and Maxwellian distributions of particle velocities, but these assumptions are easily violated in many cases. We consider these departures from equilibrium and possible diagnostics in detail

EUV EMISSION LINE RATIOS FOR Si IV IN THE SOLAR TRANSITION REGION

Theoretical electron temperature sensitive emission line ratios in Si IV involving the 3d 2D - 3p 2P and 4s 2S - 3p 2P multiplets at ~1125Å and 816Å respectively are derived using R-matrix electron excitation rate calculations. A comparison of these with observational data for a solar active region obtained with the Harvard S-055 spectrometer on board Skylab reveals that there is good agreement between theory and observation for the ratio that includes the 2D3/2,5/2 - 2P3/2 transition at 1128.3Å. This is in contrast to the findings of Keenan, Dufton and Kingston, and provides support for the atomic data adopted in the calculations. However the 2D3/2 - 2P1/2 line at 1122.5Å appears to be severely blended, as it leads to electron temperature estimates that differ significantly from that expected in ionisation equilibrium. The fact that the I (1122.5Å)/I (1128.3Å) intensity ratios determined from several flare spectra are closer to theory than that for the active region indicates that the blending is probably due to species with relatively low ionisation potentials, such as an Fe III transition at 1122,53Å, as suggested previously by Burton and Ridgeley, and Feldman and Doschek. Electron temperatures deduced for a sunspot are much lower than that predicted from ionisation balance calculations, in agreement with earlier results, and imply that a cooling flow may be present

The O IV and S IV intercombination lines in the ultraviolet spectra of astrophysical sources.

New electron density diagnostic line ratios are presented for the O IV 2s(2)2p P-2-2s2p(24)P and S IV 3s(2)3p P-2-3s3p(24)P intercombination lines around 1400 Angstrom comparison of these with observational data for the symbiotic star RR Telescopii (RR Tel), obtained with the Space Telescope Imaging Spectrograph (STIS), reveals generally very good agreement between theory and observation. However the S IV P-2(3/2)-P-4(1/2) transition at 1423.824 Angstrom is found to be blended with an unknown feature at 1423.774 Angstrom. The linewidth for the latter indicates that the feature arises from a species with a large ionization potential. In addition, the S IV P-2(1/2)-P-4(3/2) transition at 1398.044 Angstrom is identified for the first time (to our knowledge) in an astrophysical source other than the Sun, and an improved wavelength of 1397.166 Angstrom is measured for the O IV P-2(1/2)-P-4(3/2) line. The O IV and S IV line ratios in a sunspot plume spectrum, obtained with the Solar Ultraviolet Measurements of the Emitted Radiation (SUMER) instrument on the Solar and Heliospheric Observatory, are found to be consistent, and remove discrepancies noted in previous comparisons of these two ions

Induced out-of-season spawning of the mud crab, Scylla paramamosain (Estampador) and effects of temperature on embryo development

Treated with combined bilateral eyestalk ablation and maintenance of water temperature at 22.5±1.5 °C, mud crab Scylla paramamosain females with mature ovaries were induced to produce eggs outside the natural spawning season in subtropical southern China. Newly extruded eggs from a crab were incubated in vitro at 10, 15, 20, 25, 27, 30, 35 °C, respectively, and the embryonic development was closely monitored. Abnormal cell division was observed at temperatures 10 and 35 °C. At 15 °C, development remained at the gastrula stage by day 32 post-spawn, at which time the experiment was terminated. Hatching of in vitro incubated eggs occurred between 20 and 30 °C. An increase in incubation temperature from 20 to 25 °C reduced the incubation duration by 14 days, 2.6 times of that measured for a similar 5 °C increase from 25 to 30 °C. Embryonic development of S. paramamosain was divided into stage 0–10, and the duration of each stage was recorded for each incubation temperature. The information obtained allows accurate prediction of hatching time of female crabs incubated under variable temperatures. Larvae hatched from in vitro incubated eggs were reared to reach first juvenile crab stage and their dry weights were similar to those of larvae hatched naturally