OCTAD-S: Digital Fast Fourier Transform Spectrometers by FPGA

We have developed a digital fast Fourier transform (FFT) spectrometer made of an analog-to-digital converter (ADC) and a field-programmable gate array (FPGA). The base instrument has independent ADC and FPGA modules, which allow us to implement different spectrometers in a relatively easy manner. Two types of spectrometers have been instrumented, one with 4.096 GS/s sampling speed and 2048 frequency channels and the other with 2.048 GS/s sampling speed and 32768 frequency channels. The signal processing in these spectrometers has no dead time and the accumulated spectra are recorded in external media every 8 ms. A direct sampling spectroscopy up to 8 GHz is achieved by a microwave track-and-hold circuit, which can reduce the analog receiver in front of the spectrometer. Highly stable spectroscopy with a wide dynamic range was demonstrated in a series of laboratory experiments and test observations of solar radio bursts.Comment: 20 pages, 7 figures, accepted for publication in Earth, Planets and Spac

Real-time monitor of geomagnetic field in the near-pole regions as an index of magnetospheric electric field

Solar wind electric field that penetrates into the magnetosphere is an important key for causes of magnetosphenc disturbances. Since PC index, produced from the variation of the magnetic field in the near-pole regions is known to be a good indicator of magnetospheric electric field, monitoring the magnetic activity in the near-pole regions in real-time is useful for nowcasting/forecasting space weather. From the comparison of horizontal components of the magnetic field data between two stations, Eureka and Thule, it is found that the correlation between these two stations are quite high except for the summer months. This result suggests that magnetic field variations in the near-pole region are uniform, and the index can be produced throughout the year using magnetic field data in the northern and southern near-pole region

Intercomparison of ionospheric observations obtained by 10C-type ionosonde and by FMCW-type ionosondes at Syowa station, Antarctica - Part.2 -

第3回極域科学シンポジウム/第36回極域宙空圏シンポジウム 11月26日（月）、27日（火） 国立極地研究所 2階ラウン

イオノゾンデ オヨビ ファブリ・ペロー カンショウケイ ニ ヨッテ カンソク サレタ シゴメン ネツケンフウ ノ ヒカク

電離圏ダイナミクスに大きく寄与する熱圏風についての理解を深めるため,イオノゾンデの磁気共役点観測により推定された南北方向の熱圏風(推定熱圏風)と,ファブリ・ペロー干渉計(FPI)観測により直接測定された南北方向の熱圏風との相関を調べた.推定熱圏風は,磁気共役点における熱圏風は等しい(赤道横断風モードが卓越する)という仮定のもとで導出される.2 つの手法で観測された夜間の熱圏風を比較するのは本研究が初めてである.2010 年のチェンマイ(タイ)とコトタバン(インドネシア)のイオノゾンデとFPI データを比較した結果,両者はおおむね良い相関を示したが,相関が悪い日もあった.相関が悪い事例は,赤道から収束・発散する成分を無視できず,赤道横断風モードが卓越するという仮定が成立しないと解釈されるものである.また,2 つの手法で求めた熱圏風の相関を季節別に調べると,2-4 月に両者の相関が高い一方,5-7 月に両者の相関が低いことがわかった.To comprehend ionospheric-thermospheric coupling, one must understand the thermospheric wind system. However, measuring the thermospheric wind using a Fabry-Perot interferometer (FPI) is not an easy task. Because of this difficulty, some researchers have estimated meridional wind velocities using data obtained from a pair of ionosonde stations near the geomagnetic conjugate points, under the assumption that the meridional wind is the same at the two ionosonde stations (transequatorial mode wind). In this paper, we construct the first comparison of the estimated meridional wind velocitieswith meridional wind observed with FPIs. We analyzed data from the ionosondes and FPIs installed at Chiang Mai, Thailand, and Kototabang, Indonesia, from 2010. We found that the estimated and observed wind velocities were generally in good agreement on most nights, although on some nights, the wind velocities were different. The assumption that the meridional wind is equal anywhere between the two ionosonde stations would not be suitable for the days when the winds were not in good agreement. We also investigated the seasonal dependence of the correlation between the estimated and observed meridional winds. They were in good agreement from February to April and were not in good agreement from May to July

Suzaku monitoring of hard X-ray emission from η carinae over a single binary orbital cycle

The Suzaku X-ray observatory monitored the supermassive binary system η Carinae 10 times during the whole 5.5 yr orbital cycle between 2005 and 2011. This series of observations presents the first long-term monitoring of this enigmatic system in the extremely hard X-ray band between 15 and 40 keV. During most of the orbit, the 15-25 keV emission varied similarly to the 2-10 keV emission, indicating an origin in the hard energy tail of the kT ∼ 4 keV wind-wind collision (WWC) plasma. However, the 15-25 keV emission declined only by a factor of three around periastron when the 2-10 keV emission dropped by two orders of magnitude due probably to an eclipse of the WWC plasma. The observed minimum in the 15-25 keV emission occurred after the 2-10 keV flux had already recovered by a factor of ∼3. This may mean that the WWC activity was strong, but hidden behind the thick primary stellar wind during the eclipse. The 25-40 keV flux was rather constant through the orbital cycle, at the level measured with INTEGRAL in 2004. This result may suggest a connection of this flux component to the γ-ray source detected in this field. The helium-like Fe Kα line complex at ∼6.7 keV became strongly distorted toward periastron as seen in the previous cycle. The 5-9 keV spectra can be reproduced well with a two-component spectral model, which includes plasma in collision equilibrium and a plasma in non-equilibrium ionization (NEI) with τ ∼ 1011 cm-3 s-1. The NEI plasma increases in importance toward periastron

An observation plan of ionospheric scintillations by use of GPS signals received in Syowa Station, Antarctica – preliminary result

第2回極域科学シンポジウム/第35回極域宙空圏シンポジウム 11月16日（水） 統計数理研究所 3階リフレッシュフロ

Intercomparison of ionospheric observations obtained by 10C-type ionosonde and by FMCW-type ionosondes at Syowa station, Antarctica - initial results -

第2回極域科学シンポジウム/第35回極域宙空圏シンポジウム 11月15日（火） 国立極地研究所 2階大会議室前フロ

The ASTRO-H X-ray Observatory

The joint JAXA/NASA ASTRO-H mission is the sixth in a series of highly successful X-ray missions initiated by the Institute of Space and Astronautical Science (ISAS). ASTRO-H will investigate the physics of the high-energy universe via a suite of four instruments, covering a very wide energy range, from 0.3 keV to 600 keV. These instruments include a high-resolution, high-throughput spectrometer sensitive over 0.3-2 keV with high spectral resolution of Delta E < 7 eV, enabled by a micro-calorimeter array located in the focal plane of thin-foil X-ray optics; hard X-ray imaging spectrometers covering 5-80 keV, located in the focal plane of multilayer-coated, focusing hard X-ray mirrors; a wide-field imaging spectrometer sensitive over 0.4-12 keV, with an X-ray CCD camera in the focal plane of a soft X-ray telescope; and a non-focusing Compton-camera type soft gamma-ray detector, sensitive in the 40-600 keV band. The simultaneous broad bandpass, coupled with high spectral resolution, will enable the pursuit of a wide variety of important science themes.Comment: 22 pages, 17 figures, Proceedings of the SPIE Astronomical Instrumentation "Space Telescopes and Instrumentation 2012: Ultraviolet to Gamma Ray

The Quiescent Intracluster Medium in the Core of the Perseus Cluster

Clusters of galaxies are the most massive gravitationally-bound objects in the Universe and are still forming. They are thus important probes of cosmological parameters and a host of astrophysical processes. Knowledge of the dynamics of the pervasive hot gas, which dominates in mass over stars in a cluster, is a crucial missing ingredient. It can enable new insights into mechanical energy injection by the central supermassive black hole and the use of hydrostatic equilibrium for the determination of cluster masses. X-rays from the core of the Perseus cluster are emitted by the 50 million K diffuse hot plasma filling its gravitational potential well. The Active Galactic Nucleus of the central galaxy NGC1275 is pumping jetted energy into the surrounding intracluster medium, creating buoyant bubbles filled with relativistic plasma. These likely induce motions in the intracluster medium and heat the inner gas preventing runaway radiative cooling; a process known as Active Galactic Nucleus Feedback. Here we report on Hitomi X-ray observations of the Perseus cluster core, which reveal a remarkably quiescent atmosphere where the gas has a line-of-sight velocity dispersion of 164+/-10 km/s in a region 30-60 kpc from the central nucleus. A gradient in the line-of-sight velocity of 150+/-70 km/s is found across the 60 kpc image of the cluster core. Turbulent pressure support in the gas is 4% or less of the thermodynamic pressure, with large scale shear at most doubling that estimate. We infer that total cluster masses determined from hydrostatic equilibrium in the central regions need little correction for turbulent pressure.Comment: 31 pages, 11 Figs, published in Nature July