分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： The Si I 6560.58 \r{A} line in the H$\alpha$ blue wing is blended with a telluric absorption line from water vapor in ground-based observations. Recent observations with the space-based telescope CHASE provide a new window to study this line. We aim to study the Si I line statistically and to explore possible diagnostics. We select three scannings in the CHASE observations, and measure the equivalent width (EW) and the full width at half maximum (FWHM) for each pixel on the solar disk. We then calculate the theoretical EW and FWHM from the VALC model. An active region is also studied in particular for difference in the quiet Sun and the sunspots. The Si I line is formed at the bottom of the photosphere. The EW of this line increases from the disk center to $\mu$ = 0.2, and then decreases toward the solar limb, while the FWHM shows a monotonically increasing trend. Theoretically predicted EW agrees well with observations, while the predicted FWHM is far smaller due to the absence of unresolved turbulence in models. The macroturbulent velocity is estimated to be 2.80 km s$^{-1}$ at the disk center, and increases to 3.52 km s$^{-1}$ at $\mu$ = 0.2. We do not find any response to flare heating in current observations. Doppler shifts and line widths of the Si I 6560.58 \r{A} and Fe I 6569.21 \r{A} lines can be used to study the mass flows and turbulence of the different photospheric layers. The Si I line has good potentials to diagnose the dynamics and energy transport in the photosphere.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： The Si I 6560.58 \r{A} line in the H$\alpha$ blue wing is blended with a telluric absorption line from water vapor in ground-based observations. Recent observations with the space-based telescope CHASE provide a new window to study this line. We aim to study the Si I line statistically and to explore possible diagnostics. We select three scannings in the CHASE observations, and measure the equivalent width (EW) and the full width at half maximum (FWHM) for each pixel on the solar disk. We then calculate the theoretical EW and FWHM from the VALC model. An active region is also studied in particular for difference in the quiet Sun and the sunspots. The Si I line is formed at the bottom of the photosphere. The EW of this line increases from the disk center to $\mu$ = 0.2, and then decreases toward the solar limb, while the FWHM shows a monotonically increasing trend. Theoretically predicted EW agrees well with observations, while the predicted FWHM is far smaller due to the absence of unresolved turbulence in models. The macroturbulent velocity is estimated to be 2.80 km s$^{-1}$ at the disk center, and increases to 3.52 km s$^{-1}$ at $\mu$ = 0.2. We do not find any response to flare heating in current observations. Doppler shifts and line widths of the Si I 6560.58 \r{A} and Fe I 6569.21 \r{A} lines can be used to study the mass flows and turbulence of the different photospheric layers. The Si I line has good potentials to diagnose the dynamics and energy transport in the photosphere.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Ye Qiu
ShiHao Rao
Chuan Li
Cheng Fang
MingDe Ding
Zhen Li
YiWei Ni
WenBo Wang
Jie Hong
Qi Hao
Yu Dai
PengFei Chen
XiaoSheng Wan
Zhi Xu
Wei You
Yuan Yuan
HongJiang Tao
XianSheng Li
YuKun He
Qiang Liu
摘要： The H{\alpha} line is an important optical line in solar observations containing the information from the photosphere to the chromosphere. To study the mechanisms of solar eruptions and the plasma dynamics in the lower atmosphere, the Chinese H{\alpha} Solar Explorer (CHASE) was launched into a Sun-synchronous orbit on October 14, 2021. The scientific payload of the CHASE satellite is the H{\alpha} Imaging Spectrograph (HIS). The CHASE/HIS acquires, for the first time, seeing-free H{\alpha} spectroscopic observations with high spectral and temporal resolutions. It consists of two observational modes. The raster scanning mode provides full-Sun or region-of-interest spectra at H{\alpha} (6559.7-6565.9 {\AA}) and Fe I (6567.8-6570.6 {\AA}) wavebands. The continuum imaging mode obtains full-Sun photospheric images at around 6689 {\AA}. In this paper, we present detailed calibration procedures for the CHASE/HIS science data, including the dark-field and flat-field correction, slit image curvature correction, wavelength and intensity calibration, and coordinate transformation. The higher-level data products can be directly used for scientific research.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： Ellerman bombs (EBs) and UV bursts are both small-scale solar activities that occur in active regions. They are now believed to form at different heights in the lower atmosphere. In this paper, we use one-dimensional radiative hydrodynamic simulations to calculate various line profiles in response to heating in different atmospheric layers. We confirm that heating in the upper photosphere to the lower chromosphere can generate spectral features of typical EBs, while heating in the mid to upper chromosphere can generate spectral features of typical UV bursts. The intensity evolution of the H$\alpha$ line wing in EBs shows a rise--plateau pattern, while that of the Si IV 1403 \r{A} line center in UV bursts shows a rise--fall pattern. However, the predicted enhancement of FUV continuum near 1400 \r{A} for EBs is rarely reported and requires further observations to check it. With two heating sources or an extended heating source in the atmosphere, both EB and UV burst features could be reproduced simultaneously.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： Plasmon-free surface-enhanced Raman scattering (SERS) substrates have attracted tremendous attention for their abundant sources, excellent chemical stability, superior biocompatibility, good signal uniformity, and unique selectivity to target molecules. Recently, researchers have made great progress in fabricating novel plasmon-free SERS substrates and exploring new enhancement strategies to improve their sensitivity. This review summarizes the recent developments of plasmon-free SERS substrates and specially focuses on the enhancement mechanisms and strategies. Furthermore, the promising applications of plasmon-free SERS substrates in biomedical diagnosis, metal ions and organic pollutants sensing, chemical and biochemical reactions monitoring, and photoelectric characterization are introduced. Finally, current challenges and future research opportunities in plasmon-free SERS substrates are briefly discussed.
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