Brightening phenomena in prominences at the center of the Hα line

Two examples of sudden brightenings in local regions of active prominences as observed at the center of the H line are described. The origin of the brightenings is discussed in terms of Doppler shifts along the line of sight, Doppler brightenings and intrinsic changes of physical conditions. It is shown that the two examples presented here have common characteristics and the origin may probably be attributed to intrinsic changes of physical conditions.Contributions from the Kwasan and Hida Observatories, University of Kyoto, No. 257.     

On the intensity ratio of emission lines of Nai D1 to D2 in prominences

Spectroscopic observations of the Nai D emission lines of prominences were made with the Domeless Solar Telescope in Hida Observatory. When active prominences are bright in the D₂ emission line, the intensity ratio of D₁ to D₂ is found to deviate significantly from the theoretical ratio of the optically-thin case. On the other hand, the intensity ratio is close to the theoretical ratio for the most part of quiescent prominences. Furthermore, the full widths at half maximum intensity of the D₂ emission line for active prominences become wider than those of the D₁ line, as the intensity of the D₂ line gets higher. These observed features clearly show that the emitting region of the Nai D lines is optically thick in some types of prominences. Non-LTE calculations were made by taking the ionization degree of hydrogen atoms and the thickness of the prominences and the electron temperature as free parameters. It is shown that the electron temperature of the emitting region of the Nai D lines should be as low as 4000 K for an explanation of the large optical thickness of the Nai D lines for active prominences. Brief discussions are included about the possible existence of low temperatures in active prominences.     

Myctophid fishes of the genusMyctophum (myctophidae) in the pacific and Indian oceans

The key to the nine species:M. nitidulum Garman,M. aurolaternatum Garman,M. spinosum (Steindachner),M. asperum Richardson,M. obtusirostrum Tåning,M. orientale (Gilbert),M. phengodes (Lütken),M. selenoides Wisner andM. brachygnathum (Bleeker), was prepared for the genusMyctophum, typical surface migrating myctophid fishes, from the Pacific and Indian Oceans. The three species ofM. cuvieri (Castelnau),M. indicus (Day),M. novaeseelandidae (Steindachner) were excluded from the present key, since they have not been reported since they were originally described.M. lychnobium Bolin formsM. spinosumlychnobium complex and was also excluded. The systematic accounts were given for seven species.     

Morphological study of the solar granulation

A time sequence of granulation images of 46 min long has allowed us to make a detailed study of the evolution of granules in an area of approximately 17″ × 17″ on the solar surface. It is found that the granules evolve by repeated fragmentation into smaller granules or merging with adjacent ones and that there are few granules which appear in the intergranular lanes as new granules (Table III). The statistical nature of granules is as follows:

1. A family of granules is defined as a group of granules produced from a single granule by fragmentation or merging. The lifetime is estimated for single granules and for families of granules. The lifetime shows a close correlation with the maximum size of a single granule or with that of the largest granule belonging to a family (Figures 5 and 7).
2. The smaller the size, the more probably a granule will disappear without further fragmentation or merging. The granule whose size is larger than 2″ will certainly split or merge as the next evolutional step (Table IV).

     

Formation of intermediate-mass black holes as primordial black holes in the inflationary cosmology with running spectral index

Formation of primordial black holes (PBHs) on astrophysical mass scales is a natural consequence of inflationary cosmology, if the primordial perturbation spectrum has a large and negative running of the spectral index as observationally suggested today because double inflation is required to explain it and fluctuations on some astrophysical scales are enhanced in the field-oscillation regime in between. It is argued that PBHs thus produced can serve as intermediate-mass black holes (IMBHs), which act as the observed ultraluminous X-ray sources (ULXs) by choosing appropriate values of the model parameters in their natural ranges. Our scenario can be observationally tested in near future because the mass of PBHs is uniquely determined once we specify the values of the amplitude of the curvature perturbation, spectral index and its running on large scales.     

Identification of SH Deltav=1 Ro-vibrational Lines in R Andromedae

We report the detection of a broad 22 μm emission feature in the Carina Nebula H ii region by the Infrared Space Observatory (ISO) short-wavelength spectrometer. The feature shape is similar to that of the 22 μm emission feature of newly synthesized dust observed in the Cassiopeia A supernova remnant. This finding suggests that both of the features are arising from the same carrier and that supernovae are probably the dominant production sources of this new interstellar grain. A similar broad emission dust feature is also found in the spectra of two starburst galaxies from the ISO archival data. This new dust grain could be an abundant component of interstellar grains and can be used to trace the supernova rate or star formation rate in external galaxies. The existence of the broad 22 μm emission feature complicates the dust model for starburst galaxies and must be taken into account correctly in the derivation of dust color temperature. Mg protosilicate has been suggested as the carrier of the 22 μm emission dust feature observed in Cassiopeia A. The present results provide useful information in studies on the chemical composition and emission mechanism of the carrier.     

Coronal prominences on the disk observed on 29 October 1972

A group of coronal prominences appeared over a large sunspot group near the central meridian on October 29, 1972. The bright points, which were most clearly seen on the H-image taken at the line center, are interpreted as the points of inflow of the prominence matter into the penumbra. The amount of mass transported by the largest prominence among the group is found to share a considerable fraction of the total mass which may be contained in the permanent coronal condensation over the spot group. The observational data for the microwave emission from the spot group is discussed in relation to this phenomenon.     

Vertical heat transfer based on direct microstructure measurements in the ice-free Pacific-side Arctic Ocean: the role and impact of the Pacific water intrusion

This study quantifies diapycnal mixing and vertical heat transfer in the Pacific side of the Arctic Ocean, where sea-ice cover has disappeared between July and September in the last few decades. We conducted microstructure measurements in the open water region around the Canada Basin from late summer to fall in 2009 and 2010 using R/V Mirai. In the study domain, the dissipation rate of turbulent kinetic energy, ε, is typically as low level as O(10^?10) W kg^?1, resulting in vertical heat diffusivity of O(10^?7) m² s^?1, which is close to the molecular diffusivity of heat, suggesting comparatively little predominance of mechanical turbulent mixing. An exception is the case at the Barrow Canyon, where the strong baroclinic throughflow generates substantial vertical mixing, producing ε > O(10^?7) W kg^?1, because of the shear flow instability. Meanwhile, in the confluence region, where the warm/salty Pacific water and the cold/fresh Arctic basin water encounter, the micro-temperature profiles revealed a localized enhancement in vertical diffusivity of heat, reaching O(10^?5) m² s^?1 or greater. In this region, an intrusion of warm Pacific water creates a horizontally interleaved structure, where the double-diffusive mixing facilitates vertical heat transfer between the intruding Pacific water and the surrounding basin waters.