A filament eruption and accompanying coronal field changes on November 5, 1992

An H filament eruption on November 5, 1992 was fully observed in H with the Hida Flare Monitoring Telescope, while Yohkoh's Soft X-ray Telescope observed the pre- and post-eruption evolution of the coronal magnetic fields. From the H data, including the red and blue wings, we have reconstructed the rise of the filament, including trajectory, velocity, and acceleration. In combination with the Yohkoh data this reconstruction suggests that the filament had several interactions with other coronal magnetic fields during the eruption. The Yohkoh data also shows pre-eruption changes in the coronal fields and several post-eruption bright coronal structures. The pre-eruption changes are interpreted as a partial opening of the corona, indicating that it is not necessary to have a complete opening of the corona in order for a filament to erupt and we discuss the several possible contributions from emerging flux. The post-event bright coronal structures are compared with theory and with a cleaner filament eruption event on July 31, 1992. These comparisons suggest that, although there are many similarities, it is hard to completely reconcile the observations with the existing theory.     

Fine structure in the inner corona observed at the 1970 eclipse

On the slit spectrogram obtained at the 1970 eclipse in Mexico, the intensities of four coronal lines (Nixiii 5116, Fexiv 5303, Fex 6374, and Nixv 6702) and the continuum were measured as a function of distance along the slit. It is found that there exist a lot of fine fluctuations both in the lines and in the continuum intensities superposed on a large scale formation. The correspondence of such fluctuations between the continuum and the lines is good, with the exception of the line 6374 which shows a peculiar fluctuation. It is shown that the intensities of the three lines 5116, 5303, and 6702 seem to be proportional to the square of the continuum intensity while the 6374 line intensity may be proportional to the fourth power or more.     

Air-sea CO2 exchange of beach and near-coastal waters of the Chukchi Sea near Barrow, Alaska

Partial pressure of CO₂ in equilibrium with sample water (pCO₂) for the coastal water in the Chukchi Sea was continuously observed in summer, 2008. Average daily CO₂ flux calculated from the pCO₂ and gas transfer coefficients ranged from −0.144 to −0.0701 g C m⁻² day⁻¹ depending on which gas transfer coefficient was used. The pCO₂ before the landfast ice sheets melted appeared to be highly biologically controlled based on the following information: (1) the diurnal pattern of pCO₂ was strongly correlated with Photosynthetic Photon Flux Density (PPFD); (2) high chlorophyll density was observed during periods of peak uptake; and (3) the day-to-day variation in the pCO₂ strongly correlated with the presence or absence of near-shore ice sheets. The lowest pCO₂ of 35 ppm together with the highest PPFD of 1362 μmol E m⁻² s⁻¹ were observed in the afternoon on June 28 in the presence of sea ice. The very low pCO₂ observed in late June was likely caused by high photosynthetic rates related to high phytoplankton densities typically observed from spring to early summer near the ice edge, and by water low in salinity and CO₂ released by melting sea ice early in the season.     

A Multiple Flare Scenario where the Classic Long-Duration Flare Was Not the Source of a CME

A series of flares (GOES class M, M and C) and a CME were observed in close succession on 20 January 2004 in NOAA 10540. Radio observations, which took the form of types II, III and N bursts, were associated with these events. We use the combined observations from TRACE, EIT, Hα images from Kwasan, MDI magnetograms and GOES to understand the complex development of this event. Contrary to a standard interpretation, we conclude that the first two impulsive flares are part of the CME launch process while the following long-duration event flare represents simply the recovery phase. Observations show that the flare ribbons not only separate but also shift along the magnetic inversion line so that magnetic reconnection progresses stepwise to neighboring flux tubes. We conclude that “tether cutting” reconnection in the sheared arcade progressively transforms it to a twisted flux tube, which becomes unstable, leading to a CME. We interpret the third flare, a long-duration event, as a combination of the classical two-ribbon flare with the relaxation process following forced reconnection between the expanding CME structure and neighboring magnetic fields. Electronic Supplementary Material  The online version of this article () contains supplementary material, which is available to authorized users.     

Reduction of future disaster damages by learning from disaster experiences

This paper examines the effect of a country’s own past disaster experiences and nearby countries’ past experiences on subsequent disaster damage. We use global disaster data from 1990 to 2010, which include disaster-related death tolls for both natural and technological disasters that are further divided into sub-categories. Overall, we find evidence of a reduction effect of past disaster damage on future disaster damage. More detailed analyses show that an adaptation effect seems to be present for certain combinations of disaster types and levels of economic development. The results show that a country’s own experiences reduce future damage for natural disasters but that the marginal effect is larger for lower-income countries. On the other hand, for technological disasters, a robust impact of experiences was found only in higher-income countries. In terms of the disaster experiences of nearby countries, the adaptation effect was found only for natural disasters, and the marginal impact was relatively higher for higher-income countries.     

Ultrasonic measurements of Vp and Qp: relaxation spectrum of complex modulus on basalt melts

Ultrasonic compressional wave velocity V_p and quality factor Q_p have been measured in alkali basalt, olivine basalt and basic andesite melts in the frequency range of 3.4–22 MHz and in the temperature range of 1100–1400°C. Velocity and attenuation of the melts depend on frequency and temperature, showing that there are relaxation mechanisms in the melts. Complex moduli are calculated from the ultrasonic data. The results fit well a complex modulus of Arrhenius temperature dependence with log-normal Gaussian distribution in relaxation times of attenuation. The analysis yields average relaxation time, its activation energy, relaxed modulus, unrelaxed modulus and width of Gaussian distribution in relaxation times. Relaxed modulus is smaller (17.5 GPa) for basic andesite melt of high silica and high alumina contents than for the other two basalt melts (18.1–18.4 GPa). The most probable relaxation times decrease from ～ 3 × 10^?10 s for basic andesite to ～ 10^?11 s for alkali basalt at 1400°C. Activation energies of attenuation, ranging from 270 to 340 kJ mol^?1 in the three melts, are highest in basic andesite. Longitudinal viscosity values and their temperature dependences are also calculated from V_p and Q_p data. The volume viscosity values are estimated from the data using the shear viscosity values. Longitudinal, volume and shear viscosities and their activation energies are highest in the basic andesite melt of the most polymerized structure.     

Subsidence of the Miyako‐Sone submarine carbonate platform,east of Miyako‐jima Island,northwestern Pacific Ocean

Bathymetric mapping and observations of the seafloor using a remotely operated vehicle (ROV, Hyper‐Dolphin 3K) were carried out on the slopes of the Miyako‐Sone submarine platform, east of Miyako‐jima in the Ryukyu Islands, northwestern Pacific Ocean. The bathymetric map indicates that terraces are present at water depths of approximately 140 m, 330 m, 400 m, and 680 m on the northwestern slope of the platform. A number of NW–SE trending lineaments, probably faults, extend perpendicular to the axis of the Ryukyu Island Arc. Two ROV surveys were conducted at water depths ranging from 519 m (on the slope) to 121 m (shallowest part of the platform). The surveys revealed that well‐indurated carbonate rocks are exposed at terrace margins and on upper slopes, and that the lower slopes are covered with modern sediments consisting of unconsolidated, coarse‐sand‐sized bioclastic carbonates. Calcareous nannofossils from the well‐indurated carbonate rocks indicate a Middle–Late Pleistocene age, which suggests that the rocks correlate with the Quaternary reef and fore‐reef deposits of the Ryukyu Group (Ryukyu Limestone) on the Ryukyu Islands. No siliciclastic deposits corresponding to the upper Miocene–lower Pleistocene Shimajiri Group (as exposed on Okinawa‐jima and Miyako‐jima islands) were recovered during the surveys. Coeval well‐indurated carbonate rocks, all of which formed in a similar sedimentary environment, have been downthrown towards the west due to displacements on the western sides of normal faults. Subsidence of the Miyako‐Sone submarine platform was the result of large vertical displacements on such normal faults. The timing of initial subsidence cannot be tightly constrained, but the presence of the youngest limestone at progressively lower levels towards the west suggests the subsidence continued until after 0.265 Ma.