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Bando, T.

Publications and source records attributed to Bando, T..

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2017

Discovery of Short-Timescale Oscillations in the Transition Region by CLASP

High cadence spectroscopic observations by CLASP reveal that intensity fluctuations of blue and red peaks of the hydrogen Lyman-alpha line (121.57 nm) recurrently appear in the quiet Sun at short timescale. The intensity fluctuations of the blue and red peaks are opposite in phase to each other: the blue peak is enhanced during the decease of the red peak, and vice versa. Similar intensity fluctuations also can be seen in Mg II h & k profiles observed with IRIS. It is suggested that the short-timescale oscillatory or torsional phenomena take place in the transition region or the upper chromosphere.

CLASP↗
NASA NTRS2016

Modeling the Scattering Polarization of the Hydrogen Ly-alpha Line Observed by CLASP in a Filament Channel

The 400 arcsec spectrograph slit of CLASP crossed predominantly quiet regions of the solar chromosphere, from the limb towards the solar disk center. Interestingly, in the CLASP slit-jaw images and in the SDO images of the He I line at 304 A, we can identify a filament channel (FC) extending over more than 60 arcsec crossing the spectrograph slit. In order to interpret the peculiar spatial variation of the Q/1 and U/1 signals observed by CLASP in the hydrogen Ly-alpha line (1216 A) and in the Si Ill line (1206 A) in such a filament channel, it is necessary to perform multi-dimensional radiative transfer modeling. In this contribution, we show the first results of the two-dimensional calculations we are carrying out in given filament models, with the aim of determining the filament thermal and magnetic structure by comparing the theoretical and the observed polarization signals.

CLASP↗
NASA NTRS2016

Clasp/SJ Observation of Time Variations of Lyman-Alpha Emissions in a Solar Active Region

The Chromospheric Lyman-alpha SpectroPolarimeter (CLASP) is a sounding rocket experiment launched on September 3, 2015 to investigate the solar chromosphere, and the slit-jaw (SJ) optical system took Lyα images with the high time cadence of 0.6 s. By the CLASP/SJ observation, many time variations in the solar chromosphere with the time scale of <1 minute were discovered (see the poster by Kubo et al., Pa-13). We focused on an active region and investigated the short (<30 s) time variations and relation to the coronal structure observed by SDO/AIA. We compared the Ly(alpha) time variations at footpoints of coronal magnetic fields observed by AIA 211 Å (approx.2 MK) and AIA 171 Å (0.6 MK), and non-loop regions. As the result, we found the <30 s Ly(alpha) time variations had more in the footpoint regions. On the other hand, the <30 s time variations had no dependency on the temperature of the loop.

CLASP↗
NASA NTRS2016

Ubiquitous Fast Propagating Intensity Disturbances in Solar Chromosphere

High cadence observations by the slit-jaw (SJ) optics system of the sounding rocket experiment "the Chromospheric Lyman Alpha SpectroPolarimeter (CLASP)" reveal ubiquitous intensity disturbances that recurrently propagate in either the chromosphere, transition region, or both at a speed much higher than the sound speed.

disturbances↗
NASA NTRS2016

Optical Alignment of the Chromospheric Lyman-Alpha SpectroPolarimeter using Sophisticated Methods to Minimize Activities under Vacuum

The Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) is a sounding-rocket instrument developed at the National Astronomical Observatory of Japan (NAOJ) as a part of an international collaboration. The in- strument main scientific goal is to achieve polarization measurement of the Lyman-alpha line at 121.56 nm emitted from the solar upper-chromosphere and transition region with an unprecedented 0.1% accuracy. For this purpose, the optics are composed of a Cassegrain telescope coated with a "cold mirror" coating optimized for UV reflection and a dual-channel spectrograph allowing for simultaneous observation of the two orthogonal states of polarization. Although the polarization sensitivity is the most important aspect of the instrument, the spatial and spectral resolutions of the instrument are also crucial to observe the chromospheric features and resolve the Ly- pro les. A precise alignment of the optics is required to ensure the resolutions, but experiments under vacuum conditions are needed since Ly-alpha is absorbed by air, making the alignment experiments difficult. To bypass this issue, we developed methods to align the telescope and the spectrograph separately in visible light. We will explain these methods and present the results for the optical alignment of the CLASP telescope and spectrograph. We will then discuss the combined performances of both parts to derive the expected resolutions of the instrument, and compare them with the flight observations performed on September 3rd 2015.

CLASP↗
NASA NTRS2016

In-Flight Performance of the Polarization Modulator in the CLASP Rocket Experiment

We developed a polarization modulation unit (PMU), a motor system to rotate a waveplate continuously. We applied this PMU for the Chromospheric Lyman-alpha SpectroPolarimeter (CLASP), a sounding rocket experiment to observe the linear polarization of the Lyman-alpha emission (121.6 nm vacuum ultraviolet) from the upper chromosphere and transition region of the Sun with a high polarization sensitivity of 0.1% for the first time and investigate the vector magnetic field. Rotation non-uniformity of the waveplate causes error in the polarization degree (i.e. scale error) and crosstalk between Stokes components. In the ground tests, we confirmed that PMU has superior rotation uniformity. CLASP was successfully launched on September 3, 2015, and PMU functioned well as designed. PMU achieved a good rotation uniformity during the flight and the high precision polarization measurement of CLASP was successfully achieved.

CLASP↗
NASA NTRS2016

Discovery of Ubiquitous Fast Propagating Intensity Disturbances by the Chromospheric Lyman Alpha Spectropolarimeter (CLASP)

High cadence observations by the slit-jaw (SJ) optics system of the sounding rocket experiment known as the Chromospheric Lyman Alpha SpectroPolarimeter (CLASP) reveal ubiquitous intensity disturbances that recurrently propagate in one or both of the chromosphere or transition region at a speed much higher than the sound speed. The CLASP/SJ instrument provides a time series of 2D images taken with broadband filters centered on the Ly(alpha) line at a 0.6 s cadence. The fast propagating intensity disturbances are detected in the quiet Sun and in an active region, and at least 20 events are clearly detected in the field of view of 527′′ x 527′′ during the 5-minute observing time. The apparent speeds of the intensity disturbances range from 150 to 350 km/s, and they are comparable to the local Alfven speed in the transition region. The intensity disturbances tend to propagate along bright elongated structures away from areas with strong photospheric magnetic fields. This suggests that the observed propagating intensity disturbances are related to the magnetic canopy structures. The maximum distance traveled by the intensity disturbances is of about 10′′, and the widths are a few arcseconds, which is almost determined by the pixel size of 1.′′03. The timescale of each intensity pulse is shorter than 30 s. One possible explanation of the fast propagating intensity disturbances observed by CLASP is magneto-hydrodynamic fast mode waves.

CLASP↗
NASA NTRS2015

Experimental Estimation of CLASP Spatial and Spectral Resolutions: Results of the Instrument's Optical Alignment

The Chromospheric Lyman-Alpha SpectroPolarimeter is a sounding rocket experiment design to measure for the first time the polarization signal of the Lyman-Alpha line (121.6nm), emitted in the solar upper-chromosphere and transition region. This instrument aims to detect the Hanle effect's signature hidden in the Ly-alpha polarization, as a tool to probe the chromospheric magnetic field. Hence, an unprecedented polarization accuracy is needed ((is) less than 10 (exp -3). Nevertheless, spatial and spectral resolutions are also crucial to observe chhromospheric feature such as spicules, and to have precise measurement of the Ly-alpha line core and wings. Hence, this poster will present how the telescope and the spectrograph were separately aligned, and their combined spatial and spectral resolutions.

spatial resolution↗
NASA NTRS2014

A Sounding Rocket Experiment for the Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP)

A sounding-rocket experiment called the Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) is presently under development to measure the linear polarization profiles caused by scattering processes and the Hanle effect in the hydrogen Lyman-alpha line (121.567nm). Accurate measurements of the linear polarization signals caused by scattering processes and the Hanle effect are essential to explore the strength and structures of weak magnetic fields. The primary target of future solar telescopes is to measure the weak magnetic field in outer solar atmospheres (from the chromosphere to the corona through the transition region). The hydrogen Lyman-alpha-line is one of the best lines for the diagnostics of magnetic fields in the outer solar atmospheres. CLASP is to be launched in 2015, and will provide, for the first time, the observations required for magnetic field measurements in the upper chromosphere and transition region. CLASP is designed to have a polarimetric sensitivity of 0.1% and a spectral resolution of 0.01nm for the Lyman-alpha line. CLASP will measure two orthogonal polarizations simultaneously for about 5-minute flight. Now the integration of flight mirrors and structures is in progress. In addition to our strategy to realize such a high-precision spectro-polarimetry in the UV, we will present a progress report on our pre-launch evaluation of optical and polarimetric performances of CLASP.

solar↗