标题： 在X1耀斑的爆发相期间氦线偏振情况 显示英文标题

标题： On helium line polarization during the impulsive phase of an X1 flare

摘要： 我们分析了在X1耀斑SOL2014-03-29T17:48期间，使用邓恩太阳望远镜上的设施红外光谱仪（FIRS）获得的He I 1083~nm多重线（$1s2s~^3\!S_1 - 1s2p~^3\!P^o_{2,1,0}$）的光谱偏振数据。在扫描活动区NOAA 12017时，FIRS狭缝在爆发相穿过耀斑条带，此时氦线强度在$<$处变为发射线，强度是连续谱的两倍。它们的线偏振轮廓在整个多重线中符号相同，包括1082.9 nm，强度类似，在$<5$%的连续谱强度处。也观察到了较弱的塞曼诱导的线偏振。只有最强的线偏振与由雷文·拉马蒂高能太阳光谱成像仪观测到的30-70 keV硬X射线（HXR）发射相吻合。偏振通常比HXR发射更广泛且持续时间更长。1082.9~nm组分的上部$J=0$能级不可偏振，因此较低能级的偏振是原因。我们进行了非LTE辐射转移计算，在热板中优化仅匹配强度。通过辐射各向异性随波长的系统性符号变化，当1082.9组分的板光学深度为$< 1$时，线偏振自然再现。粒子束的碰撞既不需要，也不能产生1082.9和1083.0 nm组分相同的偏振符号。He I线偏振只需足够的加热以产生所需厚度的板。之前报道的H$\alpha$广泛不同的偏振是由不同光学深度的板产生的不同辐射各向异性解释的。 显示英文摘要

摘要： We analyze spectropolarimetric data of the He I 1083~nm multiplet ($1s2s~^3\!S_1 - 1s2p~^3\!P^o_{2,1,0}$) during the X1 flare SOL2014-03-29T17:48, obtained with the Facility Infrared Spectrometer (FIRS) at the Dunn Solar Telescope. While scanning active region NOAA 12017, the FIRS slit crossed a flare ribbon during the impulsive phase, when the helium line intensities turned into emission at $<$ twice the continuum intensity. Their linear polarization profiles are of the same sign across the multiplet including 1082.9 nm, intensity-like, at $<5$\% of the continuum intensity. Weaker Zeeman-induced linear polarization is also observed. Only the strongest linear polarization coincides with hard X-ray (HXR) emission at 30-70 keV observed by the Reuven Ramaty High Energy Solar Spectroscope Imager. The polarization is generally more extended and lasts longer than the HXR emission. The upper $J=0$ level of the 1082.9~nm component is unpolarizable, thus lower level polarization is the culprit. We make non-LTE radiative transfer calculations in thermal slabs optimized to fit only intensities. The linear polarizations are naturally reproduced, through a systematic change of sign with wavelength of the radiation anisotropy when slab optical depths of the 1082.9 component are $< 1$. Collisions with beams of particles are neither needed nor can they produce the same sign of polarization of the 1082.9 and 1083.0 nm components. The He I line polarization merely requires heating sufficient to produce slabs of the required thickness. Widely different polarizations of H$\alpha$, reported previously, are explained by different radiative anisotropies arising from slabs of different optical depths.