We analyze coordinated Hinode XRT and EIS observations of a non-flaring active region to investigate the thermal properties of coronal plasma taking advantage of the complementary diagnostics provided by the two instruments. In particular we want to explore the presence of hot plasma in non-flaring regions. Independent temperature analyses from the XRT multi-filter dataset, and the EIS spectra, including the instrument entire wavelength range, provide a cross-check of the different temperature diagnostics techniques applicable to broad-band and spectral data respectively, and insights into cross-calibration of the two instruments. The emission measure distribution, EM(T), we derive from the two datasets have similar width and peak temperature, but show a systematic shift of the absolute values, the EIS EM(T) being smaller than XRT EM(T) by approximately a factor 2. We explore possible causes of this discrepancy, and we discuss the influence of the assumptions for the plasma element abundances. Specifically, we find that the disagreement between the results from the two instruments is significantly mitigated by assuming chemical composition closer to the solar photospheric composition rather than the often adopted "coronal" composition (Feldman 1992). We find that the data do not provide conclusive evidence on the high temperature (log T[K] >~ 6.5) tail of the plasma temperature distribution, however, suggesting its presence to a level in agreement with recent findings for other non-flaring regions.
Comparison of Hinode/XRT and RHESSI detection of hot plasma in the non-flaring solar corona
我们比较了观测的非耀斑太阳日冕同时与Hinode/XRT和RHESSI。2006年11月12日分析的日冕主要由一个单一的活动区。对排放措施进行了比较。我们推导出发射测量分布与温度的整个活动区从多滤波器XRT数据。我们检查的兼容性与总排放量的测量值估计的流量与RHESSI测量，如果排放来自等温等离子体。我们发现，RHESSI和XRT数据分析一致指向存在一个次要的排放测量组件峰值在log T ~ 6.8-6.9。XRT和RHESSI结果之间的差异在几个因素之内，表明交叉一致性的可接受水平。
This study on plasma heating considers the time-dependent ionization process during a large solar flare on September 10, 2017, observed by Hinode/EIS. The observed FeXXIV / FeXXIII ratios increase downstream of the reconnection outflow, and they are consistent with the time-dependent ionization effect at a constant electron temperature Te = 25 MK. Moreover, this study also shows that the non-thermal velocity, which can be related to the turbulent velocity, reduces significantly along the downstream of the reconnection outflow, even when considering the time-dependent ionization process.
The signatures of energy release and energy transport for a kink-unstable coronal flux rope are investigated via forward modelling. Synthetic intensity and Doppler maps are generated from a 3D numerical simulation. The CHIANTI database is used to compute intensities for three Hinode/EIS emission lines that cover the thermal range of the loop. The intensities and Doppler velocities at simulation resolution are spatially degraded to the Hinode/EIS pixel size (1\arcsec), convolved using a Gaussian point-spread function (3\arcsec), and exposed for a characteristic time of 50 seconds. The synthetic…
We present a new coalignment method for the EUV Imaging Spectrometer (EIS) on board the Hinode spacecraft. In addition to the pointing offset and spacecraft jitter, this method determines the roll angle of the instrument, which has never been systematically measured, and is therefore usually not corrected. The optimal pointing for EIS is computed by maximizing the cross-correlations of the Fe XII 195.119 Å line with images from the 193 Å band of the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO). By coaligning 3336 rasters with high signal-to-noise ratio, we e…
We present an analysis of several Hinode EIS observations of coronal line widths in the quiet Sun, up to 1.5 Rsun radial distances. No significant variations are found, which indicates no damping of Alfvén waves in the quiescent corona. However, the uncertainties in estimating the instrumental width mean that a firm conclusion cannot be reached. We present a discussion of various EIS instrumental issues and suggest that the strongest lines, from Fe XII at 193.5 and 195.1 A, have anomalous instrumental widths. We show how line widths in EIS are uncertain when the signal is low, and that the ins…
In this paper we study the soft X-ray (SXR) signatures of one particular prominence. The X-ray observations used here were made by the Hinode/XRT instrument using two different filters. Both of them have a pronounced peak of the response function around 10 A. One of them has a secondary smaller peak around 170 A, which leads to a contamination of SXR images. The observed darkening in both of these filters has a very large vertical extension. The position and shape of the darkening corresponds nicely with the prominence structure seen in SDO/AIA images. First we have investigated the possibilit…
The target of this work is to investigate the physical nature of polar jets in the solar corona and their possible contribution to coronal heating and solar wind flow based on the analysis of X-ray images acquired by the Hinode XRT telescope. We estimate the different forms of energy associated with many of these small-scale eruptions, in particular the kinetic energy and enthalpy. Two Hinode XRT campaign datasets focusing on the two polar coronal holes were selected to analyze the physical properties of coronal jets; the analyzed data were acquired using a series of three XRT filters. Typical…
We present the study of the X2-class flare which occurred on the 27 October 2014 and was observed with the Interface Region Imaging Spectrograph (IRIS) and the EUV Imaging Spectrometer (EIS) on board the Hinode satellite. Thanks to the high cadence and spatial resolution of the IRIS and EIS instruments, we are able to compare simultaneous observations of the \xxi~1354.08~Å~and \xxiii~263.77~Å~high temperature emission ($\gtrsim$ 10~MK) in the flare ribbon during the chromospheric evaporation phase. We find that IRIS observes completely blue-shifted \xxi~line profiles, up to 200 km s$^{-1}$ dur…
The present work illustrates the potential of a new diagnostic technique that allows the measurement of the coronal magnetic field strength in solar active regions utilizing a handful of bright \ion[Fe x] and \ion[Fe xi] lines commonly observed by the Hinode/EIS high-resolution spectrometer. The importance of this new diagnostic technique lies in two basic facts: 1) the coronal magnetic field is probably the most important quantity in coronal physics, as it is at the heart of the processes regulating Space Weather and the properties of the solar corona, and 2) this technique can be applied to …
We present joint Hinode/EIS and IRIS observations of Fe XII lines in active regions, both on-disk and off-limb. We use an improved calibration for the EIS data, and find that the 192.4 A / 1349 A observed ratio is consistent with the values predicted by CHIANTI and the coronal approximation in quiescent areas, but not in all active region observations, where the ratio is often lower than expected by up to a factor of about two. We investigate a number of physical mechanisms that could affect this ratio, such as opacity and absorption from cooler material. We find significant opacity in the EIS…
Observations from the 2012 transit of Venus are used to derive empirical formulae for long and short-range scattered light at locations on the solar disk observed by the Hinode Extreme ultraviolet Imaging Spectrometer (EIS) and the Solar Dynamics Observatory Atmospheric Imaging Assembly (AIA) instruments. Long-range scattered light comes from the entire solar disk, while short-range scattered light is considered to come from a region within 50" of the region of interest. The formulae were derived from the Fe XII 195.12 A emission line observed by EIS and the AIA 193 A channel. A study of the w…
SDO/AIA and Hinode/EIS Observations of Interaction Between an EUV Wave and Active Region Loops
我们提出了详细的分析极紫外（EUV）波和它的相互作用与活动区（AR）的太阳动力学观测/大气成像组件和日出极紫外成像光谱仪（EIS）所观察到的环路。该波于2011年8月4日从AR 11261开始，以430- 910 km \s的速度传播。观察到它穿过另一个AR并穿过其路径上的细丝通道。EUV波扰动邻近的AR环并激发向这些环的足点传播的扰动。对AR环的EIS观测表明，在波过境时，原始红移增加了约3 km \s，而原始蓝移略有下降。波过境后，这些变化被逆转。当极紫外波到达极冕洞边界时，会先后产生两个反射波，其中一部分反射波在日边上方传播。第一波反射波在太阳边缘上方遇到了一个大规模的环路系统，第二波以更高的速度在它前面144 Mm处迅速出现。这些发现可以解释在一个快速模式的磁声波解释的EUV波，其中观察到的EUV波产生的扩展日冕物质抛射的框架。
Plasma diagnostics of an EIT wave observed by Hinode/EIS and SDO/AIA
我们提出了等离子体诊断的EIT波的观察与高节奏的Hinode/EIS坐盯光谱和SDO/AIA图像在HOP-180观测活动期间获得的2011年2月16日。在传播的EIT波前，我们观察到向下的等离子体流的EIS Fe XII，Fe XIII，和Fe XVI谱线（log T ~ 6.1-6.4）的视线（LOS）的速度高达20公里/秒。这些红移之后是蓝移，向上的速度高达-5 km/s，表明波前后面的等离子体弛豫。在波的演化过程中，向下的速度脉冲从几公里/秒变陡到20公里/秒，随后衰减，与线强度的相对变化相关。在EIT波阵面的等离子体密度的预期增加估计从观察到的强度增加位于我们的密度诊断从EIS XIII 202/203 AA线比的噪声水平。没有显着的LOS等离子体运动中观察到的He II线，这表明波脉冲是不够强，扰动底层色球。这与没有Halpha Moreton波与事件相关的结果一致。沿EIS狭缝传播的EIT波显示出~ -540 m/s ~ 2的强减速度和~ 590 km/s的起始速度。这些发现与日冕快模式MHD波的通过是一致的，它将等离子体向下推动并在日冕底部压缩。
Study of the three-dimensional shape and dynamics of coronal loops observed by Hinode/EIS
我们研究了2006年12月3日用日之出的极紫外成像光谱仪（EIS）观测到的NOAA活动区10926中沿选定日冕环的等离子体流动。从强度图像上追踪的环的形状和沿其长度测量的多普勒频移，我们使用一个简单的几何模型计算它们的三维（3D）形状和等离子体流速。对Fe VIII 185 Ang.中可见的环进行该计算，Fe X 184角，Fe XII 195 Ang.，Fe XIII 202 Ang.，和Fe XV 284 Ang.谱线。在大多数情况下，从一个足迹到另一个足迹的流动是单向的，但也有从循环顶部到其足迹的排水运动的情况。我们的研究结果表明，相同的环路可能会显示不同的流动模式时，在不同的谱线观察，这表明一个动态的复杂，而不是一个整体结构。我们还进行了磁外推的线性无力场近似使用SOHO/MDI磁图，旨在对一阶识别的外推磁场线对应的重建的循环。在所有情况下，最佳拟合的外推线都表现出左手扭曲（α < 0），与该区域的主导扭曲一致。
In the present work we study Hinode/EIS observations of an active region taken before, during and after a small C2.0 flare in order to monitor the evolution of the magnetic field evolution and its relation to the flare event. We find that while the flare left the active region itself unaltered, the event included a large Magnetic Field Enhancement (MFE), which consisted of a large increase of the magnetic field to strengths just short of 500~G in a rather small region where no magnetic field was measured before the flare. This MFE is observed during the impulsive phase of the flare at the foot…
Spectroscopic diagnostics of solar coronal plasmas critically depends on the uncertainty in the measured line intensities. One of the main sources of uncertainty is instrumental scattered light, which is potentially most important in low-brightness areas. In the solar corona, such areas include polar and equatorial coronal holes, which are the source regions of the solar wind; instrument-scattered light must thus pose a significant obstacle to studies of the source regions of the solar wind. In this paper we investigate the importance of instrument-scattered light on observations of equatorial…
We analyze the spectra of high temperature \fexxiv~lines observed by \emph{Hinode}/EIS during the impulsive phase of the X8.3--class flare on September 10, 2017. The line profiles are broad, show pronounced wings, and clearly depart from a single Gaussian shape. The lines can be well fitted with $κ$ distributions, with values of $κ$ varying between~$\approx$1.7 to 3. The regions where we observe the non-Gaussian profiles coincide with the location of high-energy ($\approx$100--300 keV) HXR sources observed by \emph{RHESSI}, suggesting the presence of particle acceleration or turbulence, also c…
We perform plasma diagnostics, including that of the non-Maxwellian $κ$-distributions, in several structures observed in the solar corona by the Extreme-Ultraviolet Imaging Spectrometer (EIS) onboard the Hinode spacecraft. To prevent uncertainties due to the in-flight calibration of EIS, we selected spectral atlases observed shortly after the launch of the mission. One spectral atlas contains an observation of an active region, while the other is an off-limb quiet Sun region. To minimize the uncertainties of the diagnostics, we rely only on strong lines and we average the signal over a spatial…
NuSTAR is a highly sensitive focusing hard X-ray (HXR) telescope and has observed several small microflares in its initial solar pointings. In this paper, we present the first joint observation of a microflare with NuSTAR and Hinode/XRT on 2015 April 29 at ~11:29 UT. This microflare shows heating of material to several million Kelvin, observed in Soft X-rays (SXRs) with Hinode/XRT, and was faintly visible in Extreme Ultraviolet (EUV) with SDO/AIA. For three of the four NuSTAR observations of this region (pre-, decay, and post phases) the spectrum is well fitted by a single thermal model of 3.2…
Active Region Moss: Doppler Shifts from Hinode/EIS Observations
研究苔藓区的多普勒频移和多普勒频移与温度的关系，可以帮助我们了解活动区核心的加热过程。在本文中，我们使用了一个活跃的区域观测记录的极紫外成像光谱仪（EIS）在2007年12月12日出测量的多普勒频移的苔藓地区。我们通过定义Tripathi等人（2010年）推导的低密度截止值，将苔藓区域与其他活动区域区分开来。我们根据Young等人（2012）中描述的方法对EIS波长校准进行了非常仔细的分析。对于在log T = 5.85和log T = 6.25 K之间具有最大灵敏度的谱线，我们发现速度分布峰值在0 km/s附近，估计误差为4-5 km/s。分布的宽度随温度而减小。分布的平均值显示出随温度升高而增加的蓝移，并且分布也显示出朝向蓝移的不对称性。将这些结果与不同的日冕加热模型预测的观测值进行比较，我们发现这些结果与稳定和脉冲加热情景是一致的。然而，事实上，有大量的像素显示速度振幅超过5公里的不确定性的$^{-1}$是暗示脉冲加热。显然，需要进一步的观测约束来区分这两种加热情景。
Evidence of widespread hot plasma in a non-flaring coronal active region from Hinode/XRT
纳米耀斑，在空间上无法分辨的磁链中的短而强的热脉冲，现在被认为是解决日冕加热问题的主要候选者。然而，频繁出现的纳米耀斑要求耀斑热等离子体始终存在于日冕中。到目前为止，它的探测被证明是难以捉摸的，部分原因是预测的强度非常微弱。在这里，我们报告的一个活跃的区域观察到的5个过滤器的日之出/XRT在2006年11月的分析。我们已经使用的过滤器比率的方法来获得软，硬比率的温度和排放量的地图。这些图是近似的，因为等离子体被假设为沿着每个视线是等温的。尽管如此，最难的可用比率揭示了约10 MK的血浆的明显存在。为了获得更详细的等离子体特性的信息，我们进行了蒙特卡罗模拟假设各种非等温发射测量分布沿视线。我们发现，所观察到的过滤器的比率意味着双峰分布组成的一个强冷（log T ~ 6.3-6.5）的组件和较弱（百分之几）和较热（6.6 < log T < 7.2）的组件。数据与沿所有视线的双峰分布一致，即，整个活跃区域。我们还发现，从过滤器的比率推断的等温温度敏感地依赖于冷组件的精确温度。该分量的轻微偏移可能导致热分量在硬比率测量中被遮蔽。因此，以硬比率和软比率制作的温度图往往是反相关的。我们的结论是，这一观察结果支持存在广泛的nanoflaring活动的活跃区域。
Thermal structure of hot non-flaring corona from Hinode/EIS
在以往的研究中，人们曾通过SDO/AIA三个不同窄带通道的图像诊断出太阳活动区存在一个非常热的等离子体成分。这种诊断从EUV成像数据也支持了匹配形态的发射在热的Ca XVII线，与Hinode/EIS观察。这一证据是有争议的，因为未知的分布的排放措施沿视线。在这里，我们详细调查的热分布的一个这样的区域使用EUV光谱数据。在SDO/AIA，Hinode/EIS和XRT观测到的活动区域中，我们选择了一个具有非常热的等离子体成分的子区域和另一个较冷的子区域进行比较。提取两者的平均光谱，并选择14条强谱线进行分析，这些谱线均匀地探测5.5 < log T < 7的温度范围。从这些线的发射测量分布与MCMC方法重建。结果进行交叉检查与比较的两个分区，用不同的反演方法，与图像的形态，并与从窄和宽带成像仪测量的通量。我们发现，而冷区域具有平坦且无特征的分布，其在温度log T >= 6.3时下降，热区域的分布在log T = 6.6处显示出明确的峰值，并且在两侧上逐渐减小趋势，从而支持用成像仪诊断的热分量的非常热的性质。其他交叉检查与此结果一致。这项研究提供了一个完整的活动区组件的分析，并由此产生的方案支持在核心的一个小的非常热的等离子体组件的存在，与温度log T > 6.6。
Recently, it has been proposed that the magnetic-field-induced transition (MIT) in Fe X can be used to measure coronal magnetic field strengths. Several techniques, the direct line ratio technique and the weak and strong magnetic field techniques, are developed to apply the MIT theory to spectroscopic observations taken by EUV Imaging Spectrometer (EIS) onboard Hinode. However, the suitability of coronal magnetic field measurements based on the weak and strong magnetic field techniques has not been evaluated. Besides, temperature diagnostics is also important for measuring coronal magnetic fie…
Coronal active regions are studied using Hinode/EIS observations in the EUV line Fe XII λ195.12 by analyzing their line profiles from 2006 December to 2019 December. The period covers the last 2 yr of solar cycle 23 and solar cycle 24 fully. Active regions are the main source of magnetic field in the solar atmosphere, important in its heating and dynamics. Line profiles were obtained from various active regions spread across the Sun on a monthly basis from which we obtained the intensity, line width, Doppler velocity, and centroid and examined their variation during the solar cycle. The histog…
The contribution of plumes to the solar wind has been subject to hot debate in the past decades. The EUV Imaging Spectrometer (EIS) on board Hinode provides a unique means to deduce outflow velocities at coronal heights via direct Doppler shift measurements of coronal emission lines. Such direct Doppler shift measurements were not possible with previous spectrometers. We measure the outflow velocity at coronal heights in several on-disk long-duration plumes, which are located in coronal holes and show significant blue shifts throughout the entire observational period. In one case, a plume is m…
