Flares and plasma flow caused by interacting coronal loops

Active region NOAA 7360 was observed in 1992 December with various instruments including the Yohkoh satellite. In this region, a small loop emerged near one of the footpoints of a pre-existing large coronal loop. These loops show evidence that interactions between coronal loops cause flares, microflares, and plasma flow. All of the four flares observed in this region show that brightenings in the small loop occurred first, and then the large loop flared up. The brightenings in the large loop can not occur by themselves, but must be triggered by the brightenings in the small loop. There must be interactions between the loops to cause these flares. As well as the flares, many microflares occurred in the small loop. More than half of them are accompanied by plasma ejection phenomena from the small loop into the large loop. The large loop is filled with ejected plasma with velocities of about 1000 km s^–1. These ejection phenomena are considered as X-ray jets. The associated occurrences of the microflares and the jets suggest that they are also caused by interactions between the loops. The recurrent occurrences of the homologous flares and microflares mean that the magnetic field structure in this region inevitably causes the activity due to loop-loop interactions; the flares and jets occur under a common magnetic field structure.     

Emission curve of growth for Feii in chromospheric limb spectra

The 270 chromospheric emission lines of Feii ranging between 2000 and 3200 Å observed by Skylab at a height of 4 (2900 km) above the limb of the quiet Sun are analyzed by the emission curve of growth method, using newly calculated gf-values. It is derived that the excitation temperature is 7.2 × 10³ K and that the turbulent velocity is consistent with the previous results that the microturbulent velocity is lower than 10 km s^–1 in the cool (<10⁴ K) region of the chromosphere.Contributions from the Kwasan and Hida Observatories, University of Kyoto, No. 270.     

Seasonal dynamics influencing coastal primary production and phytoplankton communities along the southern Myanmar coast

Myanmar is tenth among the world’s fish-producing countries and third in ASEAN (Association of Southeast Asian Nations). To understand the mechanisms underlying the high production, oceanographic and phytoplankton surveys, including primary productivity measurements based on pulse amplitude modulation fluorometry, were conducted near an active fishing ground near Myeik City. Three surveys, one in each of the representative seasons and covering the characteristic coastal environments, showed well-defined seasonality in primary production and phytoplankton occurrence. End of the dry season was the most productive, with productivity of 2.59 ± 1.56 g C m^?2 day^?1 and high concentration of chlorophyll a (3.14 ± 2.64 µg L^?1). In this season, the phytoplankton population was dominated by high densities of the diatoms Bellerochea horologicalis and Chaetoceros curvisetus, whereas primary productivity was low at the onset of the dry season, 1.36 ± 0.77 g C m^?2 day^?1. However, this low primary production might be compensated by activation of microbial food chains originating from high dissolved organic carbon. The rainy season exhibited the lowest production, 6.6% of the end of the dry season, due to the extensive discharge of turbid water from the rivers which lowered euphotic layer depth and resulted in an unusually high diffuse attenuation coefficient of 2.30 ± 1.03 m^?1. This incident of turbid water may be related to soil erosion from deforestation and mangrove deterioration. This research reveals the seasonal trend in Myanmar’s coastal productivity and its relationship to the tropical monsoon climate as well as emphasizing the importance of tropical coastal environments to the sustainability of the fisheries.     

Levels and distribution of polybrominated diphenyl ethers and organochlorine compounds in sea turtles from Japan

Three species of sea turtles (green, hawksbill and loggerhead turtles) stranded along the coasts or caught (by-catch) around Ishigaki Island and Kochi, Japan were collected between 1998 and 2006 and analyzed for six organohalogen compounds viz., PBDEs, PCBs, DDTs, CHLs, HCHs and HCB. The present study is the first and foremost to report the occurrence of organohalogen compounds in the sea turtles from Japan. Among the compounds analyzed, concentrations of PCBs, DDTs and CHLs were the highest in all the turtle samples. PBDEs were ubiquitously present in all the turtle species. Comparing with the other two species, concentrations of organohalogens in green turtle were relatively low and decreasing trend in the concentrations were noted with increasing carapace length. Concentrations of OCs in sea turtles from the coasts of Ishigaki Island and Kochi were relatively low as compared to those from other locations in the world.     

Relationship between Salinity and Nutrients in the Subsurface Layer in the Suruga Bay

We investigated the water structure and nutrient distribution in the Suruga Bay from April 2000 to July 2002, especially the Offshore Water, which occupies a large part of the bay. The maximum salinity in the upper 200 m varied between 34.49 and 34.71, indicating a temporal change in the influence of Kuroshio Water on the Offshore Water. Seasonal variation in nutrient concentrations was largest from surface to 50 m. On the other hand, the variance in nutrient concentrations within each season was largest in the subsurface layer of 100–300 m in spring, summer and fall. In the Offshore Water, the change of nutrients was negatively correlated with that of salinity in each season. This suggests that an increasing intrusion of saline water brings about a lower nutrient concentration in the Offshore Water. Likewise, negative correlations were observed between the change of the maximum salinity and chlorophyll a (Δ [chl.a-int])/nutrients integrated in the upper 200 m. Δ[chl.a-int] was significantly correlated with the changes of nitrate and phosphorus, but there were no significant correlations between Δ[chl.a-int] and the change of silicate. These results suggest that the concentrations of chlorophyll a and nutrients in the Offshore Water were decreased due to the increasing intrusion of Kuroshio Water. The Offshore Water is likely to be related to the regulation of primary production by nitrate.     

Coronal Mass Ejections Observed at the Total Solar Eclipse on 13 November 2012

White-light observations of the total solar eclipse on 13 November 2012 were made at two sites, where the totality occurred 35 min apart. The structure of the corona from the solar limb to a couple of solar radii was observed with a wide dynamic range and a high signal-to-noise ratio. An ongoing coronal mass ejection (CME) and a pre-CME loop structure just before the eruption were observed in the height range between 1?–?2 R_⊙. The source region of CMEs was revealed to be in this height range, where the material and the magnetic field of CMEs were located before the eruption. This height range includes the gap between the extreme ultraviolet observations of the low corona and the spaceborne white-light observations of the high corona, but the eclipse observation shows that this height range is essential for the study of CME initiation. The eclipse observation is basically just a snapshot of CMEs, but it indicates the importance of a continuous coverage of CME observations in this height range in the future.     

Outflow Propagation in Collapsars: Collimated Jets and Expanding Outflows

We investigate the outflow propagation in the collapsar in the context of gamma-ray bursts (GRBs) with 2D relativistic hydrodynamic simulations. We vary the specific internal energy and bulk Lorentz factor of the injected outflow from non-relativistic regime to relativistic one, fixing the power of the outflow to be 10⁵¹erg s⁻¹. We observed the collimated outflow, when the Lorentz factor of the injected outflow is roughly greater than 2. To the contrary, when the velocity of the injected outflow is slower, the expanding outflow is observed. The transition from collimated jet to expanding outflow continuously occurs by decreasing the injected velocity. Different features of the dynamics of the outflows would cause the difference between the GRBs and similar phenomena, such as, X-ray flashes.     

Mass motions in active region filaments

Mass motions in active region filaments of regions NOAA 4171 and McMath 16208 are analyzed. Both regions were continuously observed with the Zeiss Lyot filter for about a week at the Hida Observatory. As for NOAA 4171, Dopplergrams are made from the H filtergrams of 7 wavelengths for the qualitative study of the velocity fields in the filament, and Beckers' cloud model analysis is employed for a quantitative study of them. Dopplergrams of McMath 16208 are also constructed for qualitative analyses to determine whether the results derived from the analysis of NOAA 4171 are applicable to this region.The following results are obtained. Matter in the long-lived filaments, which lie along the magnetic neutral lines, flows generally horizontally and along the axes of the filaments. Since the matter in the filaments is considered to flow along the magnetic field, the magnetic fields in the filaments must be highly sheared. The same patterns of mass flow are found in the same filaments on successive days; some of them last for at least several days. Some filaments show long-lived symmetrical downflows to both of their ends in which the velocity is about 30 km s^-1. Such flows are seen both in NOAA 4171 and McMath 16208. We show a morphological model of such flows.Contributions from the Kwasan and Hida Observatory, Kyoto University, No. 295.     

Long-term simulations of the sulfur concentrations over the China, Japan and Korea: A model comparison study

Three comprehensive acid deposition models were used to simulate the sulfur concentrations over northeast Asia over the period covering entire year of 2002, and discussed the aggregated uncertainties and discrepancies of the three models. The participating models are from the countries participating in the project of Longrange Transboundary Air Pollutants in Northeast Asia (LTP): China, Japan and Korea. The Eulerian Model-3/CMAQ (by China), Regional Air Quality Model (RAQM, by Japan), and Comprehensive Acid Deposition Model (CADM, by Korea) were employed by each country with common emissions data established by the administrative agencies of China, Japan and Korea. The episodic simulation results between 1 to 15, March 2002 are also presented, during which aircraft measurements were carried out over the Yellow sea. The episodic results show both a wide short-term variability in simulations against measurements, and maximum concentration differences of 3～5 times among the three models, requiring that further attention before confidence among the three models can be claimed for short-term simulations. However, the year-long cumulative simulations showed almost the same general features, with lower aggregated uncertainties between the three models, produced by the long term integration over northeast Asia.