139 research outputs found
Auroral O+ 732/733 nm emission and its relation to ion upflow
Observations of auroral oxygen ion emission at 732/733 nm were made at the Aurora station in Longyearbyen (78.2.N, 16.3.E; lm=74.9.) using an all-sky spectrograph (ASG) during the winter season of 2000/2001. A statistical analysis showed that the highest occurrence of oxygen ion auroras at Longyearbyen was seen in the dayside of the 09-12MLT region; the intensities of these auroras were also larger than those on the night side. To study the mechanism of ion up゜ow in the polar ionosphere, ASG data obtained on December 7, 2000, was analyzed together with simultaneous ionospheric data obtained by EISCAT Svalbard radar (ESR). Enhancements of electron temperature and ion upward velocity were associated with an increase in the auroral OII intensity at the magnetic zenith. This result suggests that an ambipolar electric field associated with electron temperature enhancement caused by soft electron precipitation may be involved in the mechanisms that drive ionospheric ions upward
A new meridian imaging spectrogarph for the auroral spectroscopy
Spectroscopic and monochromatic imaging observations of emissions in the upper atmosphere are mutually complementary. A meridian imaging auroral spectrograph (ASG) that can measure a spectrum in the visible region along a meridian has been developed for research on the auroral physics and the polar upper-atmosphere dynamics. Combination of a fast optical system inherited from a monochromatic all-sky imager, a grism as a dispersive element, and a cooled CCD camera has enabled a wide field-of-view of 180° along a meridian, spectral coverage of 420-730 nm, spectral resolution of 1.5-2.0 nm, and high sensitivity to be obtained. The absolute sensitivity over a full-image field was calibrated using a National Institute of Standards and Technology (NIST) traceable integrating sphere and determined to be 0.06 cts/s/R at a wavelength of 560 nm at the zenith. The ASG was installed at Longyearbyen in March 2000, and routine operation was started in the 2000/2001 winter season. An example of an auroral spectral image is presented in this report to demonstrate the performance of the ASG
3-years Occurrence Variability of Concentric Gravity Waves in the Mesopause Observed by IMAP/VISI
第6回極域科学シンポジウム分野横断型セッション:[IM] 横断 中層大気・熱圏11月17日(火) 統計数理研究所 セミナー室2(D304
Aurora and Airglow Observations with an All-Sky Imager on Shirase to Fill the Observation Gap over the Southern Ocean
The Tenth Symposium on Polar Science/Special session: [S] Future plan of Antarctic research: Towards phase X of the Japanese Antarctic Research Project (2022-2028) and beyond, Tue. 3 Dec. / Entrance Hall (1st floor) at National Institute of Polar Research (NIPR
High-precision broadband linear polarimetry of early-type binaries IV. Binary system of DH Cephei in the open cluster of NGC 7380
DH~Cephei is a well known massive O+O-type binary system on the northern sky,
residing in the young open cluster NGC~7380. Our high-precision multi-band
polarimetry has clearly revealed that variations of linear polarizations in
this system are synchronous with the phase of the orbital period. We have used
the observed variations of Stokes parameters and to derive the orbital
inclination , orientation , and the direction of rotation. In order
to determine the contribution from interstellar polarization, we have carried
out new observations of polarization of field stars with precisely measured
parallaxes.
The variations of Stokes parameters in all three , , and passbands
clearly exhibit an unambiguous periodic signal at 1.055 d with the amplitude of
variations which corresponds to half of known orbital period of
2.11 d. This type of polarization variability is expected for a binary system
with light scattering material distributed symmetrically with respect to the
orbital plane. Even though most of the observed polarization (2) is
of interstellar origin, about one third of it is due to the intrinsic
component. In addition to the regular polarization variability, there is a
non-periodic component, strongest in the passband. We obtained in the
passband our most reliable values for the orbital inclination and the orientation of the orbit on the sky
, with 1 confidence intervals. The
direction of the binary system rotation on the plane of the sky is clockwise
Temporal and spatial variations of pulsating auroras in fine-scale obtained from ground-based observations
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
Current status of ground-based optical observations for short-wavelength infrared aurora and airglow emissions in Northern Europe
The Tenth Symposium on Polar Science/Ordinary sessions: [OS] Space and upper atmospheric sciences, Wed. 4 Dec. /Entrance Hall (1st floor) at National Institute of Polar Research (NIPR
High-precision broadband linear polarimetry of early-type binaries
Aims. The fact that the O-type close binary star system AO Cassiopeiae exhibits variable phase-locked linear polarization has been known since the mid-1970s. In this work, we re-observe the polarization arising from this system more than 50 yr later to better estimate the interstellar polarization and to independently derive the orbital parameters, such as inclination, i, orientation, Omega, and the direction of the rotation for the inner orbit from the phase-folded polarization curves of the Stokes q and u parameters.Methods. The Dipol-2 polarimeter was used to obtain linear polarization measurements of AO Cassiopeiae in the B, V, and R passbands with the T60 remotely controlled telescope at an unprecedented accuracy level of similar to 0.003%. We have obtained the first proper quantification of the interstellar polarization in the direction heading towards AO Cas by observing the polarization of three neighboring field stars. We employed a Lomb-Scargle algorithm and detected a clear periodic signal for the orbital period of AO Cas. The standard analytical method based on a two-harmonics Fourier fit was used to obtain the inclination and orientation of the binary orbit.Results. Our polarimetric data exhibited an unambiguous periodic signal at 1.76 days, thus confirming the orbital period of the binary system of 3.52 days. Most of the observed polarization is of interstellar origin. The de-biased values of the orbital inclination are i = 63. + 2. /-3. and orientation of Omega = 29.(209.) +/- 8.. The direction of the binary system rotation on the plane of the sky is clockwise.</p
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