Taro Sakao

SPIE Astronomical Telescopes + Instrumentation, 2024 X-Ray, Optical, and Infrared Detectors for Astronomy XI

SPIE Astronomical Telescopes + Instrumentation, 2024 Space Telescopes and Instrumentation 2024: Ultraviolet to Gamma Ray

SPIE Astronomical Telescopes + Instrumentation, 2024 Space Telescopes and Instrumentation 2024: Ultraviolet to Gamma Ray

Heliophysics 2024 Decadal Whitepapers

Abstract The CLASP2 (Chromospheric LAyer Spectro-Polarimeter 2) sounding rocket mission was launched on 2019 April 11. CLASP2 measured the four Stokes parameters of the Mg iih and k spectral region around 2800 Å along a 200″ slit at three locations on the solar disk, achieving the first spatially and spectrally resolved observations of the solar polarization in this near-ultraviolet region. The focus of the work presented here is the center-to-limb variation of the linear polarization across these resonance lines, which is produced by the scattering of anisotropic radiation in the solar atmosphere. The linear polarization signals of the Mg iih and k lines are sensitive to the magnetic field from the low to the upper chromosphere through the Hanle and magneto-optical effects. We compare the observations to theoretical predictions from radiative transfer calculations in unmagnetized semiempirical models, arguing that magnetic fields and horizontal inhomogeneities are needed to explain the observed polarization signals and spatial variations. This comparison is an important step in both validating and refining our understanding of the physical origin of these polarization signatures, and also in paving the way toward future space telescopes for probing the magnetic fields of the solar upper atmosphere via ultraviolet spectropolarimetry.

Context. Spatially unresolved observations show that the cooling phase in solar flares can be much longer than theoretical models predict. It has not yet been determined whether this is also the case for different subregions within the flare structure. Aims. We aim to investigate whether or not the cooling times, which are observed separately in coronal loops and the supra-arcade fan (SAF), are in accordance with the existing cooling models, and whether the temperature and emission measure of supra-arcade downflows (SADs) are different from their surroundings. Methods. We analysed the M5.6 limb flare on 13 January 2015 using SDO/AIA observations. We applied a differential emission measure (DEM) reconstruction code to derive spatially resolved temperature and emission measure maps, and used the output to investigate the thermal evolution of coronal loops, the SAF, and the SADs. Results. In the event of 13 January 2015, the observed cooling times of the loop arcade and the SAF are significantly longer than predicted by the Cargill model, even with suppressed plasma heat conduction. The observed SADs show different temperature characteristics, and in all cases a lower density than their surroundings. Conclusions. In the limb flare event studied here, continuous heating likely occurs in both loops and SAF during the gradual flare phase and leads to an extended cooling phase.

The third Japanese solar-observing satellite, Hinode, has been revolutionalizing our understanding on magneto-plasma activities that prevail all layers of the solar atmosphere, namely, photosphere, chromosphere, transition region and corona. We present highlights of solar observations so far made with Hinode, and discuss possible future solar mission which has been under extensive investigation, based on Hinode results, among Japanese and international solar community.

We present highlights of observations of the Sun with Japanese Hinode mission launched by JAXA in September 2006. The scientific objective of Hinode mission is to observe, in an unprecedented detail, a wide variety of plasma activities in the Sun's corona together with magnetic activities on the photosphere and in the chromosphere, utilizing a suite of three state-of-the-art telescopes; Solar Optical Telescope (SOT), X-Ray Telescope (XRT), and EUV Imaging Spectrometer (EIS). Since the beginning of the observations late in October 2006, Hinode has been providing ample information on activities of magnetized plasmas in the solar atmosphere some of which are totally new to us. In this article, we present an overview of the Hinode mission as well as some highlights of the observations.

The Hinode (Solar-B) was launched by M-V rocket on 22 September 2006 UT. The telemetry data of the Hinode X-ray Telescope (XRT) showed that the X-ray count rate detected with the XRT had decreased rapidly since the operational heaters on the XRT telescope tube were turned on. This is attributed to the fact that molecular contaminants accumulated onto the CCD with the temperature of −60ºC resulting in the degradation of the XRT sensitivity. We baked the CCD at the temperature of 35ºC in order to remove the contaminants from the CCD surface. However many contaminant spots appeared on the surface. We found that major contaminant source existed in the telescope tube, and identified the contaminants as diethylhexyl phthalate (DEHP) or DEHP-like organics. The mechanisms to yield the contaminant spots were discussed.