Goichi Kimura

An observational search for giant cells in the Sun

Abstract With the supergranular network pattern seen in Hα wing image of the Sun as tracers, we derived large-scale horizontal flow field over the solar surface by a local-correlation-tracking method. We have found some evidences of the existence of large scale flow cells on the Sun.

Development of a universal tunable filter for future solar observations

We have developed a new narrowband tunable filter to perform imaging spectroscopy of the solar chromosphere. Using Liquid Crystal Variable Retarders (LCVRs) as the tuning elements for wavelength, wide-band polarizers and super achromatic half-wave plates, it is possible to make high speed tuning (about 0.1Sec), to exclude mechanical drives (and oil tank), and to cover a wide wavelength range (510-100nm). This filter builds up with seven stages each consisting of a pair of calcites, LCVR, half-wave plates and linear polarizer. The full width at half maximum (FWHM) of the filter transmission is about 0.025nm at 656.3nm.We demonstrate that the concept of the universal tunable filter using the LCVRs as tuning elements is highly promising for future application to space mission and ground based observations.

Developments of the wideband spectropolarimeter of theDomeless Solar Telescope at Hida Observatory

We developed a new universal spectropolarimeter on the Domeless Solar Telescope at Hida Observatory to realize precise spectropolarimetric observations in a wide range of wavelength in visible and near infrared. The system aims to open a new window of plasma diagnostics by using Zeeman effect, Hanle effect, Stark effect, and impact polarization to measure the external magnetic field, electric field, and anisotropies in atomic excitation in solar atmosphere. The polarimeter consists of a 60 cm aperture vacuum telescope, a high dispersion vacuum spectrograph, polarization modulator and analyser composed of a continuously rotating waveplate whose retardation is constant in 400 - 1100 nm and Wallaston prisms located closely behind the focus of the telescope, and a fast and high sensitive CCD camera or a infrared camera. The duration for this polarimeters achieving photometric accuracy of 10-3 is 30 - 60 s. Instrumental polarization of the telescope is calibrated by using a remotely controllable turret accommodating linear polarizer attached at the entrance window of the telescope to induce well known polarized light into the telescope. Thus a Mueller matrix model of the telescope is established to compensate the instrumental polarization included in observed data within the required accuracy.

The CHAIN-Project and Installation of Flare Monitoring Telescopes in Developing Countries

The Flare Monitoring Telescope (FMT) was constructed in 1992 at Hida Observatory in Japan to investigate the long-term variation of solar activity and explosive events. It has five solar imaging telescopes that simultaneously observe the full-disk Sun at different wavelengths around the H-alpha absorption line or in different modes. Therefore, the FMT can measure the three-dimensional velocity field of moving structures on the full solar disk. The science target of the FMT is to monitor solar flares and erupting filaments continuously all over the solar disk and to investigate correlation between the characteristics of the erupting phenomena and the geoeffectiveness of the corresponding coronal mass ejections (CMEs). We are planning to start up a new worldwide project, the Continuous H-alpha Imaging Network (CHAIN) project, as an important IHY project of our observatories. As part of this project, we are examining the possibility of installing telescopes similar to the FMT in developing countries. We have selected Peru and Algeria as the countries where the first and second overseas FMTs will be installed, and we are aiming to start operation of these FMTs by the end of 2010 before the maximum phase of solar cycle 24. To create such an international network, it will be necessary to improve the information technologies applied in our observation-system. In this paper, we explain the current status and future areas of work regarding our system.

Developments of a multi-wavelength spectro-polarimeter on the Domeless Solar Telescope at Hida Observatory

To obtain full Stokes spectra in multi-wavelength windows simultaneously, we developed a new spectro-polarimeter on the Domeless Solar Telescope at Hida Observatory. The new polarimeter consists of a 60 cm aperture vacuum telescope on an altazimuth mount, an image rotator, a high dispersion spectrograph, polarization modulator and analyzer composed of a continuously rotating waveplate with a retardation nearly constant around 127

Observations of Solar Hα Filament Disappearances with a New Solar Flare-Monitoring-Telescope at Hida Observatory

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A New Solar Imaging System for Observing High-Speed Eruptions: Solar Dynamics Doppler Imager (SDDI)

in 500 - 1100 nm and a polarizing beam splitter located closely behind the focus of the telescope, fast and large format CMOS cameras and an infrared camera. The slit spectrograph allows us to obtain spectra in as many wavelength windows as the number of cameras. We characterized the instrumental polarization of the entire system and established the polarization calibration procedure. The cross-talks among the Stokes Q,U and V are evaluated to be about 0.06%

The Tandem Etalon Magnetograph of the Solar Magnetic Activity Research Telescope (SMART) at Hida Observatory

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The tandem Fabry-Perot filter imaging spectro-polarimeter for the Solar Magnetic Activity Research Telescope (SMART)

1.2% depending on the degree of the intrinsic polarizations. In a typical observing setup, a sensitivity of 0.03% can be achieved in 20 - 60 second for 500 nm - 1100 nm. The new polarimeter is expected to provide a powerful tool to diagnose the 3D magnetic field and other vector physical quantities in the solar atmosphere.