MM/DD 13:00--14:30 Name
Abstract
05/16 13:00--14:30 Shotaro Sakai
We investigated the magnetosphere-ionosphere coupling with a dust-plasma interaction in Saturn's inner magnetosphere by using a modeling of ionosphere and inner magnetosphere. From our previous model, it was revealed that the magnetospheric ion velocity was significantly reduced by the electric fields generated by the ion-dust collisions when the dust density is high and the thickness of dust distribution is large. It was consistent with observations when the dust density is larger than ~105 m-3 for ionospheric conductivity of 1 S. An average electron density of Saturn's ionosphere obtained from radio occultations by Cassini spacecraft was ~1010 m-3 at 2000 km where density had a peak and gradually decreased with the increasing altitude. The density was ~108 m-3 at 10000 km. Plasma densities calculated by models also were similar to the observations and the topside temperature is ~650 K. However, electron densities from those models were calculated at the altitudes below 4000 km. We estimated the ionospheric Pedersen conductivity from the plasma densities, and the plasma temperatures and velocities by using a magnetohydrodynamics model. We used the magnetospheric plasma temperature, which was 2 eV, as a boundary condition to investigate the magnetospheric influences. The plasma density was about 109 m-3 at the altitude of 1200 km, and it decreased to about 107 m-3 at the altitude of 10000 km. Below 10000 km altitudes the light ion has the upward velocity, while heavy ions have zero or downward velocity at low altitudes. This might be due to the difference of mass. The electron temperature increased to 20000 K at the altitude of 10000 km due to the heat flow from the inner magnetosphere. The electron temperature was about 2000 K at the altitude of 1000 km, and the collision and joule heating were contributing to the temperature below 2000 km. The peak density changed between about 108 and 1010 m-3 during one Saturn’s day, and the electron density decreased with increasing the altitude. On the other hand, the electron temperature didn’t depend on the local time. The Pedersen conductivity was the maximum 0.7 S on day time and the minimum 0.3 S on dawn time. The Pedersen conductivity strongly depends on the ionospheric plasma density. We estimated the magnetospheric ion velocity by using the calculated conductivity. The Pedersen conductivity was the largest value at L = 3 and it decreased with the increase of the distance from Saturn. The conductivity changed in local time. The maximum was on the day time and the minimum was on the dawn time. The calculated ion velocity decreases from the co-rotation speed outside 3.5 RS. The ion velocity was 60-80% of the co-rotation speed in the inner magnetosphere. The ion velocity was smaller than the co-rotation speed since the magnetospheric electric field is smaller than the co-rotational electric field when the current due to the ion-dust collision flows in the inner magnetosphere. The ion velocity strongly depended on the local time since the conductivity also depended on the local time. It is suggested that the dispersion of the observed speeds could show the dependence of local time. The ion velocity is fast during the solar irradiation since the Pedersen conductivity is large, while it becomes slow after the sunset because of the small conductivity. The magnetosphere-ionosphere coupling is significantly important for the dust-plasma interaction. It is impossible to understand the dust-plasma interaction in Saturn's inner magnetosphere without understanding of the Saturn's ionosphere, since the magneto- sphere and ionosphere is intimately-connected.
05/30 13:00--14:30 Masahiro Mihara
Sprites which are mainly caused by positive lightning discharges are transient discharge phenomena occurring in the mesosphere and lower thermosphere. Until now, various properties of sprite have been studied by numerical simulation and optical observation from ground and airplanes. However, the occurrence conditions of sprite have yet to be revealed fully. Recent studies suggested that an activity of the in-cloud discharges preceding a return stroke of a cloud-to-ground discharge would have a severe impact on the determination of the horizontal distribution of sprites. In order to clarify this, it is essential to carry out nadir observations of lightning discharges and sprites from the space. JEM-GLIMS mission which is nadir observations of lightning discharges and sprites from International Space Station (ISS) was started continuous observations from November 20, 2012. The purpose of this research is to identify the relationship between the spatial distributions of sprites and IC activity using observation data of JEM-GLIMS. In this presentation, I will introduce some articles which described how to start propagation of sprite, condition of ionosphere at that time and factor that have an effect behavior of plasma in ionosphere. In addition, I will talk about view of my research from hereafter.
06/06 13:00--14:30 Yuya Gouda
In the Jupiter’s polar regions, there are stratospheric haze formed by aerosol particles. Using a methane band filter at 889 nm, the stratospheric haze can be observed. It shows bright cap structures covering the polar regions and the edge of the cap shows a wave structure spreading in longitudinal direction. This structure can be brightly seen in the Jupiter’s south pole than the north pole, and wave is clear at the 67S latitude in particular [Sánchez-Lavega, 2008]. The bright cap in the Jupiter’s polar regions have been observed by the Hubble Space Telescope (HST) between 1994 and 1999 and the Cassini ISS in 2000. This wave structure has been seen for several years in the Jupiter’s both polar regions. These observations suggested that this wave structure is caused by a planetary rossby wave because this wave structure presents for a longer period and moves westward relative to the background flow. However, the origin and mechanism keeping to this wave structure, the vertical structure of the wave, change of the propagation velocity of the wave in the short time scale, and north-south asymmetry of the wave structure are unclear so far, because of lack of the observations in short time scale (monthly scale). We have carried out the monthly monitoring of Jupiter from 2011 to 2014 with the 1.6 m Pirka telescope of Hokkaido University. In this presentation , we show the results of observations of the wave structure in the Jupiter south polar region in 2011 and 2014. However, the wave amplitude in 2014 (about 1%) is smaller than standard deviation of the relative intensity at the same latitude (about 4%) between different images. If this goes on, we can't discuss longitudinal movement of wave structure and vertical and meridional wave propagation. We will discuss this large standard deviation from the aspect of observation and analysis.
06/13 13:00--14:30 Masataka Imai
Venus has planetary scale UV cloud features and a unique atmospheric dynamics such as the superrotation. Yamamoto and Tanaka (1997) suggested that the Kelvin and Rossby wave (planetary wave) play an important role in driving the superrotation. They also suggested that the Kelvin and Rossby wave forms the UV feature like letter Y when they balanced. Pioneer Venus observations revealed that the propagation of UV features caused the periodical variation of UV brightness and this periodicity changed like 4-day to 5-day in several month. We investigate the periodicity of UV brightness and intend to verify the association between the mechanism of the superrotation and the planetary wave (theory of Yamamoto and Tanaka (1997)). We observed the Venusian UV brightness variation as a function of latitude and time using the 1.6 m Pirka telescope owned by Hokkaido University. We carried out long-term monitoring of UV brightness by imaging Venus using 365 nm narrowband filter from August 2013 to March 2014. In our data analysis, we normalize the brightness in each latitudinal band with the mean brightness in 70N-70S area to eliminate the extinction effect of Earth's atmosphere. We also analyze Galileo and Venus Express UV images adapting this technique. Our results of Pirka telescope found that there are two types of UV brightness variation. One showed the strong periodicity in equator and mid-latitude, and it also had the symmetric structure between both hemispheres. The other one didn’t show these properties. These destruction of periodical and symmetric structure had not seen in previous observations. In this presentation, I'll show our Pirka telescope observation results and interpret them by comparing with satellite data. And I'll also talk about our future observation plan.
06/20 13:00--14:30 Shuhei Gouda
We are developing the Adaptive optics for observing planets to be carried 1.6-m Pirika telescope of the Hokkaido University, which is located at the Nayoro Observatory of the Faculty of Science, the Hokkaido University. For this adaptive optics, we consider the configuration of MCAO (Multi-Conjugate Adaptive optics) system which is expected to provide a seeing improvement over a wide-field. We need to know the atmospheric turbulence profile to evaluate the performance of AO system. I measured the atmospheric turbulence profile at Nayoro site using MASS-DIMM (Multi-Aperture Scintillation Sensor with Differential Image Motion Monitor; Kornilov et al. 2007) for that. The MASS has four apertures and measures stellar scintillation. The measure of scintillation gives turbulence profile at altitudes of 0.5, 1, 2, 4, 8, 16km. In DIMM, the turbulence integrals as seeing is estimated from the variance of the differential image motion in two small apertures, cut out in the entrance pupil of telescope by a mask. To MASS and DIMM work on the same optical path, two instruments combine as MASS-DIMM. The measured seeing in DIMM is equal to turbulence integrals of all altitudes. So, if the DIMM seeing is subtracted from the MASS seeing, the GL seeing is calculated. I borrow the MASS-DIMM, which NAO requested to Cerro Tororo Observatory. And that instrument is modified to use by Celestron C11, which is Schmidt-Cassegrain telescope and suitable for MASS-DIMM. I measured turbulence profile for 33 days of September 2013 through May 2014. And I measured seeing using Hiroshima-DIMM and MSI simultaneously with MASS-DIMM to assess measurements of MASS-DIMM and to estimate Dome Seeing and Mirror Seeing, which are caused by temperature differences. So I will present results of atmosphericturbulence profile at Nayoro site and of simultaneous measurements with Hiroshima-DIMM and MSI.
06/27 13:00--14:30 Yukihiro Takahashi
Lightning process is an excellent tool to explore the planetary atmosphere as well as Earth based on the knowledge of the relationship between the atmospheric dynamics and electrical charge. It has been suggested for a decade that thunderstorms in Jovian atmosphere contributes not only to the investigation of meteorology, which determines the large scale structures such as belt/zone and big ovals, but also to probing the water abundance of the deep atmosphere, which is crucial to constrain the behavior of volatiles in early solar system. We plan to make observation of thunderstorm activity based on lightning flash detection and cloud imagery using ground-based telescope and spacecraft. We also plan to try to detect the optical flashes using a ground-based 1.6 m reflector named PIRKA. Here we introduce an strategy to observe lightning optical emissions both by PIRKA with narrow-band high speed imaging unit and by JANUS onboard JUICE, the European Jovian exploration mission.
07/04 13:00--14:30 Junji Miyazawa
The Martian atmosphere was warm and high pressure several billions of years ago[Carr, 1999]. The Martian atmosphere is dry and low pressure (636 Pa)[McKay and Stoker, 1989; Kerr, 2000; Baker, 2001]. Although about 95% of Martian atmosphere is CO2, about 90% of escaping atmosphere is oxygen ion (O+,O2+) from the observation by Mars Express[Lundin et al., 2009]. Oxygen escape may be important for the evolution of the water of Mars. The important escape mechanisms of Martian atmosphere are Dissociative Recombination, Solar wind pick up and Sputtering. The previous models do not include the effect of the collision of the escaping particles with the atmospheric particles and the escape of the collided secondary particles. Then, we construct a model including dissociative recombination, solar wind pick up and spattering processes, and investigate the amount of the atmospheric escape in Mars. In this presentation, I will show the current state of our model and the result of the parameter study.
07/11 13:00--14:30 Hikaru Nakao
Active galactic nuclei (AGN) are the most energetic persistent objects in the Universe. The broad-line AGNs showing two peakes in the emission originating in an accretion disk. The most studied double-peaked emitter is the active nucleus of Arp 102B. For this object, a study by Chen and halpern (1989) has shown that the double-peaked Balmer lines cannot be driven by local viscous dissipation in the line-emitting part of the disk, as the Hα luminosity is of the order or even exceeds the energy locally available to power the line. This conclusion suggested that the lines are powered by illumination from an external source. The ionizing source could be a geometrically thick accretion flow, located within the inner radius of the line-emitting portion of the disk. In the case of Arp102B Eracleous et al. (2003) found that the spectral energy distribution (SED) of the nucleus is indeed well described by such a structure, a radiatively inefficient accretion flow (RIAF). This has led to the conclusion that an inner RIAF is the ionizing source of the accretion disk in Arp102B. We aim to measurement of RIAF size and variability of the luminosity In this seminar, I will introduce the previous studies of accretion disk of Arp 102B, and report progress of our research.
07/18 13:00--14:30 Nguyen Thi Thao
Vietnam has a long coastline of 3260 km that crosses 13 latitudes, from 8o23’N to 21o39’N. The fisheries sector in Vietnam can be divided in three main sub-sectors including the marine, the inland and aquaculture sub-sector. Marine fisheries are the biggest contributor to fisheries production, followed by aquaculture. There are about 7 % households in the fishery. Therefore, assessing coastal water quality serves the development of the fishery and aquaculture being important for Vietnamese economics. In order to do this, combination of in situ measurement and remote sensing data is necessary. My office, Vietnam National Satellite Center has been responsible for making a micro- satellite to observe ocean color meeting the purpose. The first work to build the micro-satellite is to determine payload mission. Ocean color observation was decided. My research focuses on making the mission requirements.
08/08 13:00--14:30 Katia Nagamine Urata
In the recent years, there has been a significant interest in small satellites with regards to Earth Observation, as they may offer scalability for both fast and economical access to space when compared to traditional programs - generally fomented by space agencies. Especially useful for developing countries, smaller satellites may provide affordable means to obtain remote sensing data. With missions already operating in the high resolution range (some even smaller than 5m GSD) and hundreds of spectral bands, the performance of these sensors may be limited by the laws of physics, which imposes a challenge in coverage, spatial resolution and quality of data obtained from such systems. In addition to that, hyperspectral sensors in small platforms may also face constraints due to limited power and data volume. In this context, we analyse some constraints faced by RISING-2 and RISESAT sensors, both Japanese microsatellites developed by a joint- collaboration between Hokkaido and Tohoku University, with regards to the potential Signal to Noise ratio (SNR) they can deliver, based on characterization of their payload, and its contribution to Earth Observation applications.
08/22 13:00--14:30 Shouta Onishi
There is a good relationship between global atmospheric phenomena and global lightning activities because early studies suggested that lightning activities are good indicators of developing of thunderstorms and convection. [e.g. Deierling and Petersen, 2008] Previous studies suggested that the intra-cloud(IC)-to-cloud- to-ground(CG) ratio is high value in deep tropics and low value in mid-latitude regions. Boccippio et al. (2000) showed another parameters which influence the ratio over the continental United States. (e.g. elevation and total flash rate) However, relationship between the ratio and global atmospheric phenomenon is not discussed yet. In my research I focus about the relationship between the IC:CG ratio and global atmospheric phenomenon using observation data of GEON, JEM-GLIMS and RISING-2. In this presentation, I will introduce some early studies and talk about my future work.
08/29 13:00--14:30 To Anh Duc
The polarization measurements achieved by the POLDER (POLarization and Directionality of the Earth’s Reflectances)instrument are used for the remote sensing of aerosol cycling, cloud-radiation interactions, the Earth radiation budget, ocean primary productivity, and the continental biosphere dynamics. Using appropriate model and from POLDER’s unique features like: 1) observed polarized reflectance in both visible and infrared regions; 2) the ability to observe the target at 12 different angles , we can acquire both the Bidirectional Reflectance Distribution Function (BRDF) and Bidirectional Polarization Distribution Function (BPDF) of the objects. Some other parameters of clouds and aerosols can also be deduced from combination of POLDER data and models. In my presentation, I will talk about the method of polarized channels as well as some results from POLDER.
09/05 13:00--14:30 Junichi Kurihara
New types of remote-sensing sensors for 50-kg class microsatellites have been developed at Hokkaido University. In those sensors, a liquid crystal tunable filter (LCTF) was applied for the first time in the world to a space-borne multispectral sensor onboard the RISING-2 microsatellite, which was launched on 24th May, 2014. The LCTF is a kind of optical band pass filter with the center wavelength electrically controlled at 1 nm intervals in the visible (420-700 nm) and near infrared (650-1050 nm) regions. Compared to conventional multispectral sensors using a rotating filter wheel with (normally less than 20) selected spectral bands, the advanced sensor using the LCTF has the great advantage of enabling multispectral observations with hundreds of bands. The LCTF can also reduce size, weight, and power consumption of multispectral sensors and the advanced sensors using the LCTF are suitable for small and dynamically unstable platforms such as UAVs and microsatellites. In this presentation, applications of the advanced sensor using the LCTF to the Earth observations by UAVs and microsatellites are introduced.
09/12 13:00--14:00 Chiharu Shimizu
Previous studies suggested that there is close relation between lightning activities and meteorological phenomena. For example, Mansell et al. [2007] reported that lightning data assimilated into a meteorological model improved the prediction accuracy of the rainfall area and amount. Price [2009] found that lightning occurrence numbers were well correlated with the maximum sustained wind speed and minimum pressures in hurricanes. However, in these studies, only the occurrence frequencies of lightning discharges are analyzed. As lightning is a discharging phenomenon, it is more important to investigate the relation between electrical properties of lightning discharges and the parameters of the severe weather. Electromagnetic waves emitted by lightning discharges can propagate long distance in the Earth- ionosphere cavity. Thus, it is possible to monitor regional and global lightning activities in real time, and these waves can be a useful tool to monitor severe weather [Price, 2013]. Recently, it is shown that the lightning-generated induction magnetic field in the ELF frequency range is well comparable to lightning current waveform [Sato et al., 2013]. Therefore, the more quantitative relation between ELF waveforms and the current waveforms will be evaluated as a first step in my study, then the relation between the charge amount derived from ELF waveform data and parameters of severe weather, such as heavy rainfall, tornadoes, downburst, typhoon, will be studies as a next step. In this presentation, recent studies on the relation between lightning activities and severe weather are reviewed, and my research objective and plan are presented.
09/12 14:10--15:10 Tsuyoshi Sato
Transient Luminous Events (TLEs)現象はelves、sprite、halo、gigantic jet などのタイプに分けられる。TLEsがどのような環境で発生するのかを知るた めにはTLEの全球頻度分布は重要な役割を果たすと思われる。先の研究ではTLEs の全球頻度分布をImager of Sprites and Upper Atmospheric Lightnings (ISUAL)を用いて求めた。ISUALは衛星FORMOSAT-2に搭載したTLE観測機器で、初 めて宇宙からの長期観測を行った。 しかしその研究には欠点がある。FORMOSAT-2は太陽同期極軌道面を通るので、 観測データは常に限られたローカルタイムのものしか得られない点である。TLE がローカルタイム依存性を持つ場合、先の研究結果ではTLE現象を知るには不十 分であると思われる。その問題を克服するために私はGLIMSを用いて全球頻度分 布を求める。GLIMSはInternational Space Station (ISS)に搭載されており、太 陽同期軌道をとらないのですべてのローカルタイムを網羅することが可能であ る。 私の研究ではローカルタイム依存性を考慮することにより、先行研究に比べて より信憑性の高いTLEの全球頻度分布を求めることを目的とする。目的に向け て、比較対象とした研究についての論文をレビューし、私の研究の参考とする。
09/19 13:00--14:30 Mitsuteru Sato
The main objective of the JEM-GLIMS mission is to conduct nadir observations of lightning discharges and lightning-associated transient luminous events (TLEs) from the International Space Station (ISS) and to identify the physical reasons determining the horizontal distribution of sprites. JEM-GLIMS was launched by H-IIB rocket and installed at the Japanese Experiment Module (JEM), Exposed facility (EF) on August, 2012. Since November 20, 2012, JEM-GLIMS started the continuous measurements and succeeded in detecting thousands of transient optical events, which are mostly lightning events. At the presentation, I will briefly show the new results derived from two-years JEM-GLIMS operations, and will summarize the future research topics and plans.
11/26 13:00--14:30 Junji Miyazawa
The Martian atmosphere was warm and high pressure several billions of years ago[Carr, 1999]. The Martian atmosphere is dry and low pressure (636 Pa)[McKay and Stoker, 1989; Kerr, 2000; Baker, 2001]. Although about 95% of Martian atmosphere is CO2, about 90% of escaping atmosphere is oxygen ion (O+,O2+) from the observation by Mars Express[Lundin et al., 2009]. Oxygen escape may be important for the evolution of the water of Mars. The important escape mechanisms of Martian atmosphere are Dissociative Recombination, Solar wind pick up and Sputtering. The previous models do not include the effect of the collision of the escaping particles with the atmospheric particles and the escape of the collided secondary particles. Then, I construct a model including dissociative recombination, solar wind pick up and spattering processes, and investigate the amount of the atmospheric escape in Mars. In this presentation, I will show the current state of my model and the result of the parameter study.
12/03 13:00--14:30 Yuya Gouda
In the Jupiter’s polar regions, there are stratospheric haze formed by aerosol particles. Using a deep methane band filter at 889 nm, the stratospheric haze can be observed. It shows bright cap structures covering the polar regions and the edge of the cap shows a wave structure spreading in longitudinal direction. This structure can be brightly seen in the Jupiter’s south pole than the north pole, and wave is clear at the 67S latitude in particular [Sánchez-Lavega, 2008]. The bright cap in the Jupiter’s polar regions have been observed by the Hubble Space Telescope (HST) between 1994 and 1999 and the Cassini ISS in 2000. This wave structure has been seen for several years in the Jupiter’s both polar regions. These observations suggested that this wave structure is caused by a planetary rossby wave because this wave structure presents for a longer period and moves westward relative to the background flow. However, the origin and mechanism keeping to this wave structure, the vertical structure of the wave, change of the propagation velocity of the wave in the short time scale, and north-south asymmetry of the wave structure are unclear so far, because of lack of the observations in short time scale (monthly scale). We have carried out the monthly monitoring of Jupiter from 2011 to 2014 with the 1.6 m Pirka telescope of Hokkaido University. In this presentation, I'll show the results of observations of the spatial structure and temporal variation of wave in the Jupiter south polar region in 2011 and 2014. It is revealed that the wave structure is maintained over few years and wave structure in both polar regions are North-South asymmetry. I'll also talk about next step of analysis of wave in Jupiter and our future observation plan.
11/26 16:00--17:30 Masahiro Mihara
Sprite is a lightning-associated transient discharge phenomena occurring in the mesosphere and lower thermosphere. Though sprite was first discovered in 1989, the physical mechanism determining the horizontal distribution of sprite is not clear so far. Recent studies suggested that an activity of the in-cloud discharges preceding a return stroke of a cloud-to-ground discharge would have a severe impact on the determination of the horizontal distribution of sprites. In order to clarify this, it is essential to carry out nadir observations of lightning discharges and sprites from the space. JEM-GLIMS is a space mission to carry out nadir observations of lightning discharges and sprites from ISS and started continuous observations from November 20, 2012. In this mission, lightning and sprite emissions can be measured by Lightning and Sprite Imager (LSI), which consists of two CMOS cameras and captures images at difference wavelength. A wide-band camera named LSI-1 is equipped with an optical filter whose pass-band ranges from 740-830nm and observes mainly lightning emission, while a narrow-band camera named LSI-2 is equipped with an optical filter whose transmittance center at the wavelength of 762nm and has 10 nm FWHM and observes mainly sprite emission since the lightning emission at 762 nm would be severely absorbed by oxygen molecules. Since the spatial resolution of LSI is about 300 m/pix at an altitude of 70 km, it is possible to detect the emissions of a columniform sprite whose horizontal scale is a few km typically. For the purpose to distinguish weak sprite emission from strong lightning emission, we have developed an image subtraction method using LSI-1 and LSI-2 image data. Arrival direction of VHF radio wave emitted in-cloud discharges is estimated interferometric method and group delay characteristic method. We have analyzed transient optical emission events captured by LSI and succeeded in detecting sprite emission and clarifying the horizontal distribution of sprites. We estimated dimension of sprite emission using subtracted image, a distance between sprite emission and peak point of lightning emission assumed return stroke. At the presentation, we will show the characteristics of the horizontal distribution of sprites and their parent lightning discharges, result of arrival direction of VHF pulses using 2 estimating method more in detail.
11/26 13:00--14:30 Hikaru Nakao
Active galactic nuclei (AGN) are the most energetic persistent objects in the Universe. The broad-line AGNs showing two peakes in the emission originating in an accretion disk. The most studied double-peaked emitter is the active nucleus of Arp 102B. For this object, a study by Chen and Halpern (1989) has shown that the double-peaked Balmer lines cannot be driven by local viscous dissipation in the line-emitting part of the disk, as the Hα luminosity is of the order or even exceeds the energy locally available to power the line. This conclusion suggested that the lines are powered by illumination from an external source. The ionizing source could be a geometrically thick accretion flow, located within the inner radius of the line-emitting portion of the disk. In the case of Arp102B Eracleous et al. (2003) found that the spectral energy distribution (SED) of the nucleus is indeed well described by such a structure, a radiatively inefficient accretion flow (RIAF). This has led to the conclusion that an inner RIAF is the ionizing source of the accretion disk in Arp102B. We expect that Arp 102B bring about a short-term variability like RIAF. We aim to measurement of short time scale variability of the double-peaked profile of Arp 102B. In this seminar, I will introduce the previous studies of accretion disk of Arp 102B, and report progress of our research.
11/26 13:00--14:30 Masataka Imai
Active galactic nuclei (AGN) are the most energetic persistent objects in the Universe. The broad-line AGNs showing two peakes in the emission originating in an accretion disk. The most studied double-peaked emitter is the active nucleus of Arp 102B. For this object, a study by Chen and Halpern (1989) has shown that the double-peaked Balmer lines cannot be driven by local viscous dissipation in the line-emitting part of the disk, as the Hα luminosity is of the order or even exceeds the energy locally available to power the line. This conclusion suggested that the lines are powered by illumination from an external source. The ionizing source could be a geometrically thick accretion flow, located within the inner radius of the line-emitting portion of the disk. In the case of Arp102B Eracleous et al. (2003) found that the spectral energy distribution (SED) of the nucleus is indeed well described by such a structure, a radiatively inefficient accretion flow (RIAF). This has led to the conclusion that an inner RIAF is the ionizing source of the accretion disk in Arp102B. We expect that Arp 102B bring about a short-term variability like RIAF. We aim to measurement of short time scale variability of the double-peaked profile of Arp 102B. In this seminar, I will introduce the previous studies of accretion disk of Arp 102B, and report progress of our research.
01/07 13:00--14:30 To Anh Duc
South China Sea with the area of 3,500,000 km^2 is the 4th biggest ocean in the world. The Ocean with its diversity and abundance of natural resources can brings a lots of advantages to its surrounded countries. From thousands years ago, Vietnam, a country which is located on the west of this ocean, has achieved much of benefits from South China Sea. However, Vietnam fishermen with lack of knowledge and technology, cannot utilize the Ocean’s resources in the way it should be. These people often rely too much on their experiences, which is an abstract and risky criteria. In shorts, the way we’re utilizing South China Sea at the moment is inconsistent with its potential. Base on satellite’s data, we can measure the chlorophyll-a concentration and sea surface temperature, which are two of the most important indexes that indicate the Ocean’s water quality. Sea surface temperature affects the behavior of the Earth’s atmosphere above, so their initialization into atmospheric model is important. Chlorophyll-a is a photosynthetic pigment that need for photosynthesis process of phytoplankton (phytoplankton is the foundation of the oceanic food chain). By having an overview on these indexes, combine with their broad experiences, I believe that Vietnam fisherman can significantly improve their working efficiency. Therefore, on this presentation, using MODIS’s data for the last two years(2013,2014), I will try to give out the chlorophyll-a concentration and sea surface temperature in South China Sea.
01/14 13:00-14:00 Chiharu Simizu
Previous studies suggested that there is close relation between lightning activities and meteorological phenomena. But in these studies, only the occurrence frequencies of lightning discharges are analyzed. As lightning is a discharging phenomenon, it is more important to investigate the relation between electrical properties of lightning discharges such as charge amount and the parameters of the severe weather. Electromagnetic waves emitted by lightning discharges can propagate long distance in the Earth-ionosphere cavity. Thus, it is possible to monitor regional and global lightning activities in real time, and these waves can be a useful tool to monitor severe weather [Price, 2013]. Recently, it is shown that the lightning-generated induction magnetic field in the ELF frequency range is well comparable to lightning current waveform [Sato et al., 2013]. Therefore, the more quantitative relation between ELF waveforms and the current waveforms will be evaluated as a first step in my study, then the relation between the charge amount derived from ELF waveform data and parameters of severe weather, such as heavy rainfall, tornadoes, downburst, typhoon, will be studies as a next step. For the first step, the lightning current waveform obtained from Mt. Ogami and ELF waveform obtained from Onagawa ELF station were analyzed. Actually, since the observed ELF waveform is affected by the frequency characteristic possessed by the observation device, the output ELF waveform has to be reconstructed with characteristics of gain and phase. On that basis, the value of integral calculated from ELF waveform and charge amount obtained from current waveform were compared. In this presentation, the analysis approaches of the two waveforms are described, and results of my analysis are discussed.
01/14 14:10-15:10 Tsuyoshi Sato
I study about identification of global distribution and occurrence rate of transient luminous events (TLEs) based on the Global Lightning and sprite MeasurementS (GLIMS) experiment onboard the ISS. While the global distribution and occurrence rate of TLEs has been documented, there was a limitation in the local time ranges of the observation. The frequency of occurrence of TLEs depends on local time. It is necessary to get data during night in local time in order to take into account the local time dependence of TLEs. This is the first time that TLEs are observed during night in local time. In order to identify the global distribution and occurrence rate of TLEs, it is necessary to evaluate the number of TLEs per unit time per unit area. I divided the surface area of the earth into 3.0°by 3.0°grid. I estimated the activity time of GLIMS and observation time in each grid. When the center of one grid is inside the FOV, I counted 1 second in the grid. I will estimate the number of events and identify the global distribution and occurrence rate of TLEs.
01/21 13:00-14:30 Nguyen Thi Thao
Ocean-colour radiometry by earth-orbiting spacecraft has already been conducted for some thirty years. It has proved to be one of the most fruitful remote sensing technologies. The results of ocean colour have revolutionized the field of biological oceanography, and have made important contributions to biogeochemistry, to physical oceanography, to ocean-system modeling and to fisheries oceanography. Current ocean colour data with low and moderate resolution are mostly useful to cover broad expanses of open waters, where colour variations chiefly depend on the presence and abundance of planktonic pigments. However, Coastal and estuarine systems are often characterized by optically complex waters including planktonic pigments, dissolved organic matter, suspended sediments, and much smaller geographical scales. For these systems, high resolution data is required. My study is to develop a new sensor to observe coastal and estuarine systems. In this seminar, I describe how to take good images to avoid sunglint effect.
01/28 13:00-14:30 Shuhei Gouda
The amount of CO in Jovian stratosphere is twice larger than the amount of CO in troposphere.It is not known that where water comes from.In previous study, it suggests that that the water is provided from comets and CO in stratosphere may be formed by shock chemistry due to impacts which sizes are bigger than 0.3km.Impact rates are proposed three models.If impact rates are determined, it is enable to restrict the cause of CO production in stratosphere. To do this, I have to observe the condition of SR(Strehl ratio)>0.02 at 0.9micron entirely jupiter(>50").So we are developing MCAO (Multi-Conjugate Adaptive Optics) system that increases spatial resolution and extends the Field of View. To estimate MCAO performance, I used Yao that is simulation tool for AO system.I used results of MASS/DMMM measurements in period from September,2013 to October, 2014 for turbulence parameters of simulations.As results of simulations, we found that the MCAO performance is adequate if the number of DM actuators is more than 120 and the number of DM is more than 2.
02/06 13:00-14:30 Shota Ohnishi
Previous studies have suggested that there exists good relationship between lightning activity and atmospheric convection [Deierling and Petersen, 2008]. Lightning data can be used as a proxy for the presence or absence of deep atmospheric convection. Kudo (2013) suggested that electrical properties of CG change according to the developing process of thunderstorm in some cases and the charge moment change are more directly associated with atmospheric parameters. On the other hand, another observation method of the lightning activities is optical observation using satellites. Previous researches estimated statistically the total lightning flashes for understanding the relationship the lightning activities and atmospheric convection. But it is difficult for optical observation to estimation electrical property lightning of discharge. If we can estimate relationship electrical property of each lightning and the flash of lightning, it is possible to understand more detailed relationship between the lightning activity and atmospheric convection. Therefore, combined optical observation using satellite and ground-based observation is required. We can estimate the charge moment change using ground-based observation of the Extremely Low Frequency (ELF, 3-3000Hz). But it is believed that most of –CG is small charge moment change. In order to estimate the small charge moment change, the observation of the Very Low Frequency (VLF, 3- 30 kHz) is required. However, it is difficult for current method of analysis to estimation of small CMC of CG occurred long range (>200 km) because of overlapping of sky waves. Therefore, a method considered effect of sky waves is required. In this study, we estimate the location of lightning and electrical characteristics of each lightning using VLF band observation in SE-Asia region using Asia VLF observation Network. We establish the method considered effect of sky waves to estimate small CMC of CG occurred at long range (>200 km). Finally, we investigate the relationship the electrical properties of lightning and each lightning flashes for understanding. In this seminar, we discuss prevent the error of lightning geolocation and estimation of CMC using VLF band.
02/18 13:00-14:30 Katia N. Urata
RISING-2 is a 50kg microsatellite successfully launched with the H-IIA rocket piggybacked on the ALOS-2 mission in May 2014. It is the result of a synergic joint collaboration between Hokkaido University and Tohoku University. Mission instruments consist of a VLF receiver, bolometer camera, wide field camera, lightning and sprite imager and a high precision telescope (HPT). This last comprises a reflecting telescope of 5m ground sample distance followed by two optical channels - visible and near infrared, respectively coupled with RGB filters and a liquid crystal tunable filter (LCTF). The onboard LCTF is a compact (30mm cube) and light weight (80g) component developed by Hokkaido University, and as the world’s first space LCTF, its spectral features are promising for the multi and hyperspectral data community, with configurable bands within 650-1050nm, 1nm/step, 10 to 30nm bandwidth. In the current seminar, we demonstrate the RISING-2 HPT-LCTF imagery pre-processing chain as well as its spatial and spectral capabilities, comparing its performance to existing systems. Quality metrics used for this analysis are Noise to Signal ratio, Modulation Transfer Function and Normalized Difference Vegetation Index comparison.
02/25 13:00-14:30 Tetsuya Fukuhara
An uncooled microbolometer camera for detecting a wild fire has been developed for a small satellite mission called “UNIFORM”. The thermal infrared camera detects wavelengths of 8-14 μm with spatial resolution of ~156 m and provides us an information which contributes to hot spot hazard. The small satellite has been designed and assembled within 50 kg and successfully launched by H2A rocket as a piggyback in 24 May 2014. The infrared camera has acquired the first light after the 72 hours of the launch, further, some observations started after initial check have successfully detected hotspots such as wild fires and volcano. Preliminary results of the mission will be presented.
03/04 13:00-14:00 Ngo Duc Minh
The need for more effective environmental monitoring of the open and coastal ocean has recently led to notable advances in satellite ocean color technology and algorithm research. Satellite ocean color sensors’ data are widely used for the detection, mapping and monitoring of phytoplankton blooms because earth observation provides a synoptic view of the ocean, both spatially and temporally. Algal blooms are indicators of marine ecosystem health; thus, their monitoring is a key component of effective management of coastal and oceanic resources. Since the late 1970s, a wide variety of operational ocean color satellite sensors and algorithms have been developed. The comprehensive review presented in this article captures the details of the progress and discusses the advantages and limitations of the algorithms used with the multi-spectral ocean color sensors CZCS, SeaWiFS, MODIS and MERIS. Present challenges include overcoming the severe limitation of these algorithms in coastal waters and refining detection limits in various oceanic and coastal environments. To understand the spatio-temporal patterns of algal blooms and their triggering factors, it is essential to consider the possible effects of environmental parameters, such as water temperature, turbidity, solar radiation and bathymetry. Hence, this review will also discuss the use of statistical techniques and additional datasets derived from ecosystem models or other satellite sensors to characterize further the factors triggering or limiting the development of algal blooms in coastal and open ocean waters.
03/04 14:10-15:10 Vi Duc Huan
"Harmful algal blooms (HABs) in the southeastern Vietnamese coastal waters have caused large economic losses in aquacultured and wild fisheries in recent years; however, there have been few oceanographic studies on these HAB events. The present study reports an extensive HAB off southeastern Vietnamese waters during late June to July 2002 with in situ observations and analyzes the oceanographic conditions using satellite remote sensing data. The HAB had high chlorophyll a (Chl a) concentrations (up to 4.5 mg m−3) occurring ∼200 km off the coast and ∼200 km northeast of the Mekong River mouth for a period of ∼6 weeks. The bloom was dominated by the harmful algae haptophyte Phaeocystis cf. globosa and caused a very significant mortality of aquacultured fish and other marine life. In the same period, sea surface temperature (SST) imagery showed a cold water plume extending from the coast to the open sea, and QuikScat data showed strong southwesterly winds blowing parallel to the coastline. This study indicated that the HAB was induced and supported by offshore upwelling that brings nutrients from the deep ocean to the surface and from coastal water to offshore water and that the upwelling was driven by strong wind through Ekman transport when winds were parallel to the coastline. This study demonstrated the possibility of utilizing a combination of satellite data of Chl a, SST, and wind velocity together with coastal bathymetric information and in situ observations to give a better understanding of the biological oceanography of HABs."
03/18 13:10-14:30 Koji Nakau
Wild fire is not only disaster, but also ineligible source of greenhouse gases (GHGs) or trans- boundary haze. Active wildfire location (so called hotspot; HS) product is utilized to estimate those effects as well as to decide tactics of firefighting. On the other hand, because it is difficult to estimate the current status of active wildfire, wildfire monitoring by satellite is inadequate to reduce such impacts as well as to tact firefights. Thus wildfire monitoring by wildfire is one of the major applications of satellite remote sensing. Toward such change of use, Hokkaido University and collaborative organizations are developing wildfire monitoring system for Asian countries including fire information providing system as well as wildfire detection and fire danger index under collaboration with Asian countries.