Author name code: cao ADS astronomy entries on 2022-09-14 author:"Cao, Wenda" ------------------------------------------------------------------------ Title: High-precision Multichannel Solar Image Registration Using Image Intensity Authors: Liang, Bo; Chen, Xi; Yu, Lan; Feng, Song; Guo, Yangfan; Cao, Wenda; Dai, Wei; Yang, Yunfei; Yuan, Ding Bibcode: 2022ApJS..261...10L Altcode: Solar images observed in different channels with different instruments are crucial to the study of solar activity. However, the images have different fields of view, causing them to be misaligned. It is essential to accurately register the images for studying solar activity from multiple perspectives. Image registration is described as an optimizing problem from an image to be registered to a reference image. In this paper, we proposed a novel coarse-to-fine solar image registration method to register the multichannel solar images. In the coarse registration step, we used the regular step gradient descent algorithm as an optimizer to maximize the normalized cross correlation metric. The fine registration step uses the Powell-Brent algorithms as an optimizer and brings the Mattes mutual information similarity metric to the minimum. We selected five pairs of images with different resolutions, rotation angles, and shifts to compare and evaluate our results to those obtained by scale-invariant feature transform and phase correlation. The images are observed by the 1.6 m Goode Solar Telescope at Big Bear Solar Observatory and the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory. Furthermore, we used the mutual information and registration time criteria to quantify the registration results. The results prove that the proposed method not only reaches better registration precision but also has better robustness. Meanwhile, we want to highlight that the method can also work well for the time-series solar image registration. Title: Solar Chromospheric Network as a Source for Solar Wind Switchbacks Authors: Lee, Jeongwoo; Yurchyshyn, Vasyl; Wang, Haimin; Yang, Xu; Cao, Wenda; Carlos Martínez Oliveros, Juan Bibcode: 2022ApJ...935L..27L Altcode: Recent studies suggest that the magnetic switchbacks (SBs) detected by the Parker Solar Probe carry information on the scales of solar supergranulation (large scale) and granulation (medium scale). We test this claim using high-resolution Hα images obtained with the visible spectropolarimeters of the Goode Solar Telescope in Big Bear Solar Observatory. As possible solar sources, we count all the spicule-like features standing along the chromospheric networks near the coronal hole boundary visible in the Hα blue-wing but absent in the red-wing images and measure the geometric parameters of dense sections of individual flux tubes. Intervals between adjacent spicules located along the chromospheric networks are found in the range of 0.4-1.5 Mm (0.°03-0.°12) tending to be smaller than the medium scale of SBs. Interdistances between all pairs of the flux tubes are also counted and they appear in a single peak distribution around 0.7 Mm (0.°06) unlike the waiting-time distribution of SBs in a scale-free single power-law form. The length-to-diameter ratio of the dense section of flux tubes is as high as 6-40, similar to the aspect ratio of SBs. The number of spicules along a network can be as high as 40-100, consistent with numerous SBs within a patch. With these numbers, it is argued that the medium scale of SBs can be understood as an equilibrium distance resulting from a random walk within each diverging magnetic field funnel connected to the chromospheric networks. Title: Fan-shaped jet close to a light bridge Authors: Liu, Y.; Ruan, G. P.; Schmieder, B.; Masson, S.; Chen, Y.; Su, J. T.; Wang, B.; Bai, X. Y.; Su, Y.; Cao, Wenda Bibcode: 2022arXiv220713246L Altcode: On the Sun,jets in light bridges are frequently observed with high-resolution instruments.The respective roles played by convection and the magnetic field in triggering such jets are not yet clear.We report a small fan-shaped jet along a LB observed by the 1.6m Goode Solar Telescope(GST) with the TiO Broadband Filter Imager(BFI),the Visible Imaging Spectrometer(VIS) in H{\alpha},and the Near-InfraRed Imaging Spectropolarimeter(NIRIS),along with the Stokes parameters.The high spatial and temporal resolution of those instruments allowed us to analyze the features identified during the jet event.By constructing the H{\alpha} Dopplergrams,we found that the plasma is first moving upward,whereas during the second phase of the jet,the plasma is flowing back.Working with time slice diagrams,we investigated the propagation-projected speed of the fan and its bright base.The fan-shaped jet developed within a few minutes,with diverging beams. At its base,a bright point was slipping along the LB and ultimately invaded the umbra of the sunspot.The H{\alpha} profiles of the bright points enhanced the intensity in the wings, similarly to the case of Ellerman bombs.Co-temporally,the extreme ultraviolet brightenings developed at the front of the dark material jet and moved at the same speed as the fan, leading us to propose that the fan-shaped jet material compressed and heated the ambient plasma at its extremities in the corona.Our multi-wavelength analysis indicates that the fan-shaped jet could result from magnetic reconnection across the highly diverging field low in the chromosphere,leading to an apparent slipping motion of the jet material along the LB.However,we did not find any opposite magnetic polarity at the jet base,as would typically be expected in such a configuration.We therefore discuss other plausible physical mechanisms,based on waves and convection, that may have triggered the event. Title: Chromospheric Recurrent Jets in a Sunspot Group and Their Intergranular Origin Authors: Zhao, Jie; Su, Jiangtao; Yang, Xu; Li, Hui; Schmieder, Brigitte; Ahn, Kwangsu; Cao, Wenda Bibcode: 2022ApJ...932...95Z Altcode: 2022arXiv220506981Z We report on high-resolution observations of recurrent fan-like jets by the Goode Solar Telescope in multiple wavelengths inside a sunspot group. The dynamics behavior of the jets is derived from the Hα line profiles. Quantitative values for one well-identified event have been obtained, showing a maximum projected velocity of 42 km s-1 and a Doppler shift of the order of 20 km s-1. The footpoints/roots of the jets have a lifted center on the Hα line profile compared to the quiet Sun, suggesting a long-lasting heating at these locations. The magnetic field between the small sunspots in the group shows a very high resolution pattern with parasitic polarities along the intergranular lanes accompanied by high-velocity converging flows (4 km s-1) in the photosphere. Magnetic cancellations between the opposite polarities are observed in the vicinity of the footpoints of the jets. Along the intergranular lanes horizontal magnetic field around 1000 G is generated impulsively. Overall, all the kinetic features at the different layers through the photosphere and chromosphere favor a convection-driven reconnection scenario for the recurrent fan-like jets and evidence a site of reconnection between the photosphere and chromosphere corresponding to the intergranular lanes. Title: Magnetic Field Re-configuration Associated With a Slow Rise Eruptive X1.2 Flare in NOAA Active Region 11944 Authors: Yurchyshyn, Vasyl; Yang, Xu; Nita, Gelu; Fleishman, Gregory; Abramenko, Valentina; Inoue, Satoshi; Lim, Eun-Kyung; Cao, Wenda Bibcode: 2022FrASS...916523Y Altcode: Using multi-wavelength observations, we analysed magnetic field variations associated with a gradual X1.2 flare that erupted on January 7, 2014 in active region (AR) NOAA 11944 located near the disk center. A fast coronal mass ejection (CME) was observed following the flare, which was noticeably deflected in the south-west direction. A chromospheric filament was observed at the eruption site prior to and after the flare. We used SDO/HMI data to perform non-linear force-free field extrapolation of coronal magnetic fields above the AR and to study the evolution of AR magnetic fields prior to the eruption. The extrapolated data allowed us to detect signatures of several magnetic flux ropes present at the eruption site several hours before the event. The eruption site was located under slanted sunspot fields with a varying decay index of 1.0-1.5. That might have caused the erupting fields to slide along this slanted magnetic boundary rather than vertically erupt, thus explaining the slow rise of the flare as well as the observed direction of the resulting CME. We employed sign-singularity tools to quantify the evolutionary changes in the model twist and observed current helicity data, and found rapid and coordinated variations of current systems in both data sets prior to the event as well as their rapid exhaustion after the event onset. Title: Design and expected performances of the large acceptance calorimeter for the HERD space mission. Authors: Pacini, L.; Adriani, O.; Bai, Y. l.; Bao, T. w.; Berti, E.; Bottai, S.; Cao, W. w.; Casaus, J.; Cui, X. z.; D'Alessandro, R.; Formato, V.; Gao, J. r.; Li, R.; Liu, X.; Lorusso, L.; Lyu, L. w.; Marín, J.; Martínez, G.; Pizzolotto, C.; Qin, J. j.; Quan, Z.; Shi, D. l.; Starodubtsev, O.; Tang, Z. c.; Tiberio, A.; Vagelli, V.; Wang, B.; Wang, R. j.; Wang, Z. g.; Xu, M.; Yang, Y.; Zhang, L.; Zheng, J. k.; Velasco, M. A. Bibcode: 2022icrc.confE..66P Altcode: 2022PoS...395E..66P No abstract at ADS Title: Abyssal Manganese Nodule Recording of Global Cooling and Tibetan Plateau Uplift Impacts on Asian Aridification Authors: Jiang, X. D.; Zhao, X.; Zhao, X. Y.; Chou, Y. -M.; Roberts, A. P.; Hein, J. R.; Yu, J. M.; Sun, X. M.; Shi, X. F.; Cao, W.; Liu, Q. S. Bibcode: 2022GeoRL..4996624J Altcode: The impact of central Asian aridification on the low latitude North Pacific Ocean since the late Miocene remains unclear. To address this question, we systematically studied an abyssal manganese nodule from the northwestern Pacific Ocean, which is expected to be sensitive to eolian dust sourced from central Asia. Geochemical variations and the fossilized remains of magnetotactic bacteria within the studied nodule manifest two prominent Asian aridification events at ∼8-7 Ma and 3.6-0 Ma. These results suggest that central Asian aridification impacted both primary productivity and abyssal microbial activity in the NW Pacific Ocean via eolian dust inputs. In contrast to the Pliocene aridification event, the late Miocene event was associated with a primary productivity bloom that is not evident in coeval global primary productivity records, which indicates that the ∼8-7 Asian aridification event was likely due to NE Tibetan Plateau uplift rather than to global cooling. Title: A High-resolution Study of Magnetic Field Evolution and Spicular Activity around the Boundary of a Coronal Hole Authors: Wang, Jiasheng; Lee, Jeongwoo; Liu, Chang; Cao, Wenda; Wang, Haimin Bibcode: 2022ApJ...924..137W Altcode: In this study, we analyze high-spatial-resolution (0.″24) magnetograms and high-spatial-resolution (0.″10) Hα off-band (± 0.8 Å) images taken by the 1.6 m Goode Solar Telescope to investigate the magnetic properties associated with small-scale ejections in a coronal hole boundary region from a statistical perspective. With one and a half hours of optical observations under excellent seeing, we focus on the magnetic structure and evolution by tracking the magnetic features with the Southwest Automatic Magnetic Identification Suite (SWAMIS). The magnetic field at the studied coronal hole boundary is dominated by negative polarity with flux cancellations at the edges of the negative unipolar cluster. In a total of 1250 SWAMIS-detected magnetic cancellation events, ~39% are located inside the coronal hole with an average flux cancellation rate of 2.0 × 1018 Mx Mm-2 hr-1, and ~49% are located outside the coronal hole with an average flux cancellation rate of 8.8 × 1017 Mx Mm-2 hr-1. We estimated that the magnetic energy released due to flux cancellation inside the coronal hole is six times more than that outside the coronal hole. Flux cancellation accounts for ~9.5% of the total disappearance of magnetic flux. Other forms of its disappearance are mainly due to fragmentation of unipolar clusters or merging with elements of the same polarity. We also observed a number of significant small-scale ejections associated with magnetic cancellations at the coronal hole boundary that have corresponding EUV brightenings. Title: Multi-passband Observations of a Solar Flare over the He I 10830 Å line Authors: Xu, Yan; Yang, Xu; Kerr, Graham S.; Polito, Vanessa; Sadykov, Viacheslav M.; Jing, Ju; Cao, Wenda; Wang, Haimin Bibcode: 2022ApJ...924L..18X Altcode: 2021arXiv211209949X This study presents a C3.0 flare observed by the Big Bear Solar Observatory/Goode Solar Telescope (GST) and Interface Region Imaging Spectrograph (IRIS) on 2018 May 28 around 17:10 UT. The Near-Infrared Imaging Spectropolarimeter of GST was set to spectral imaging mode to scan five spectral positions at ±0.8, ±0.4 Å and line center of He I 10830 Å. At the flare ribbon's leading edge, the line is observed to undergo enhanced absorption, while the rest of the ribbon is observed to be in emission. When in emission, the contrast compared to the preflare ranges from about 30% to nearly 100% at different spectral positions. Two types of spectra, "convex" shape with higher intensity at line core and "concave" shape with higher emission in the line wings, are found at the trailing and peak flaring areas, respectively. On the ribbon front, negative contrasts, or enhanced absorption, of about ~10%-20% appear in all five wavelengths. This observation strongly suggests that the negative flares observed in He I 10830 Å with mono-filtergram previously were not caused by pure Doppler shifts of this spectral line. Instead, the enhanced absorption appears to be a consequence of flare-energy injection, namely nonthermal collisional ionization of helium caused by the precipitation of high-energy electrons, as found in our recent numerical modeling results. In addition, though not strictly simultaneous, observations of Mg II from the IRIS spacecraft, show an obvious central reversal pattern at the locations where enhanced absorption of He I 10830 Å is seen, which is consistent with previous observations. Title: Stokes Inversion with Stacked Deep Neural Networks Authors: Jiang, Haodi; Li, Qin; Xu, Yan; Ahn, Kwangsu; Cao, Wenda; Wang, Jason T. L.; Wang, Haimin Bibcode: 2021AGUFMNG45B0583J Altcode: Prediction of solar eruptive events is an important topic in space weather research. Acquiring high-quality magnetic and velocity fields through Stokes inversion is crucial for accurate solar eruption prediction. We present here a new deep learning method, dubbed Stacked Deep Neural Networks (SDNN), for Stokes inversion. We apply SDNN to inferring line-of-sight (LOS) velocities and Doppler widths in addition to vector magnetic fields from Stokes profiles of the Near InfraRed Imaging Spectropolarimeter on the 1.6 m Goode Solar Telescope at the Big Bear Solar Observatory. Experimental results show that SDNN is faster, while producing smoother and cleaner LOS velocity maps and Doppler width maps, than the widely used Milne-Eddington method. Furthermore, SDNN outperforms three related machine learning algorithms, including a convolutional neural network, multiple support vector regression model, and multilayer perceptrons model, on different datasets. Thus, the proposed deep learning based SDNN tool can be considered as an alternative and efficient method for Stokes inversion. Title: Possible Signature of Sausage Waves in Photospheric Bright Points Authors: Gao, Yuhang; Li, Fuyu; Li, Bo; Cao, Wenda; Song, Yongliang; Tian, Hui; Guo, Mingzhe Bibcode: 2021SoPh..296..184G Altcode: 2021arXiv211211756G Sausage waves have been frequently reported in solar magnetic structures such as sunspots, pores, and coronal loops. However, they have not been unambiguously identified in photospheric bright points (BPs). Using high-resolution TiO image sequences obtained with the Goode Solar Telescope at the Big Bear Solar Observatory, we analyzed four isolated BPs. It was found that their area and average intensity oscillate for several cycles in an in-phase fashion. The oscillation periods range from 100 to 200 seconds. We interpreted the phase relation as a signature of sausage waves, particularly slow waves, after discussing sausage-wave theory and the opacity effect. Title: Investigations of Sizes and Dynamical Motions of Solar Photospheric Granules by a Novel Granular Segmenting Algorithm Authors: Liu, Yanxiao; Jiang, Chaowei; Yuan, Ding; Zuo, Pingbing; Wang, Yi; Cao, Wenda Bibcode: 2021ApJ...923..133L Altcode: 2021ApJ...923..133Y; 2021arXiv211003951Y Granules observed in the solar photosphere are believed to be convective and turbulent, but the physical picture of the granular dynamical process remains unclear. Here we performed an investigation of granular dynamical motions of full length scales based on data obtained by the 1 m New Vacuum Solar Telescope and the 1.6 m Goode Solar Telescope. We developed a new granule segmenting method, which can detect both small faint and large bright granules. A large number of granules were detected, and two critical sizes, 265 and 1420 km, were found to separate the granules into three length ranges. The granules with sizes above 1420 km follow Gaussian distribution, and demonstrate flat in flatness function, which shows that they are non-intermittent and thus are dominated by convective motions. Small granules with sizes between 265 and 1420 km are fitted by a combination of power-law function and Gauss function, and exhibit nonlinearity in flatness function, which reveals that they are in the mixing motions of convection and turbulence. Mini granules with sizes below 265 km follow the power-law distribution and demonstrate linearity in flatness function, indicating that they are intermittent and strongly turbulent. These results suggest that a cascade process occurs: large granules break down due to convective instability, which transports energy into small ones; then turbulence is induced and grows, which competes with convection and further causes the small granules to continuously split. Eventually, the motions in even smaller scales enter in a turbulence-dominated regime. Title: A deep learning method to estimate magnetic fields in solar active regions from photospheric continuum images Authors: Bai, Xianyong; Liu, Hui; Deng, Yuanyong; Jiang, Jie; Guo, Jingjing; Bi, Yi; Feng, Tao; Jin, Zhenyu; Cao, Wenda; Su, Jiangtao; Ji, Kaifan Bibcode: 2021A&A...652A.143B Altcode: Context. The magnetic field is the underlying cause of solar activities. Spectropolarimetric Stokes inversions have been routinely used to extract the vector magnetic field from observations for about 40 years. In contrast, the photospheric continuum images have an observational history of more than 100 years.
Aims: We suggest a new method to quickly estimate the unsigned radial component of the magnetic field, |Br|, and the transverse field, Bt, just from photospheric continuum images (I) using deep convolutional neural networks (CNN).
Methods: Two independent models, that is, I versus |Br| and I versus Bt, are trained by the CNN with a residual architecture. A total of 7800 sets of data (I, Br and Bt) covering 17 active region patches from 2011 to 2015 from the Helioseismic and Magnetic Imager are used to train and validate the models.
Results: The CNN models can successfully estimate |Br| as well as Bt maps in sunspot umbra, penumbra, pore, and strong network regions based on the evaluation of four active regions (test datasets). From a series of continuum images, we can also detect the emergence of a transverse magnetic field quantitatively with the trained CNN model. The three-day evolution of the averaged value of the estimated |Br| and Bt from continuum images follows that from Stokes inversions well. Furthermore, our models can reproduce the nonlinear relationships between I and |Br| as well as Bt, explaining why we can estimate these relationships just from continuum images.
Conclusions: Our method provides an effective way to quickly estimate |Br| and Bt maps from photospheric continuum images. The method can be applied to the reconstruction of the historical magnetic fields and to future observations for providing the quick look data of the magnetic fields.

Movie is available at https://www.aanda.org Title: Magneto-acoustic oscillations observed in a solar plage region Authors: Ji, Haisheng; Hashim, Parida; Hong, Zhenxiang; Xu, Zhe; Shen, Jinhua; Ji, Kaifan; Cao, Wenda Bibcode: 2021RAA....21..179J Altcode: 2021arXiv210111998J We gave an extensive study for the quasi-periodic perturbations on the time profiles of the line of sight (LOS) magnetic field in 10 × 10 sub-areas in a solar plage region (corresponds to a facula on the photosphere). The perturbations are found to be associated with the enhancement of He I 10830 Å absorption in a moss region, which is connected to loops with million-degree plasma. FFT analysis to the perturbations gives a kind of spectrum similar to that of Doppler velocity: a number of discrete periods around 5 minutes. The amplitudes of the magnetic perturbations are found to be proportional to magnetic field strength over these sub-areas. In addition, magnetic perturbations lag behind a quarter of the cycle in the phase with respect to the p-mode Doppler velocity. We show that the relationships can be well explained with an MHD solution for the magneto-acoustic oscillations in high-β plasma. Observational analysis also shows that, for the two regions with the stronger and weaker magnetic field, the perturbations are always anti-phased. All findings show that the magnetic perturbations are actually magneto-acoustic oscillations on the solar surface, the photosphere, powered by p-mode oscillations. The findings may provide a new diagnostic tool for exploring the relationship between magneto-acoustic oscillations and the heating of the solar upper atmosphere, as well as their role in helioseismology. Title: Multi-passband Observations Of A Negative Flare Near He I 10830 Å Authors: Xu, Y.; Yang, X.; Kerr, G.; Polito, V.; Jing, J.; Cao, W.; Wang, H. Bibcode: 2021AAS...23830305X Altcode: This study presents a C3.0 flare observed by the BBSO/GST and IRIS, on 2018-May-28 around 17:10 UT. The Near Infrared Imaging Spectropolarimeter (NIRIS) was set to spectral imaging mode to scan five spectral positions at ±0.8 Å, ±0.4 Å and line center of He I 10830 Å. Negative contrasts of around 10%, appear in all of the five wavelengths, with a weak dependence of these wavelengths. This means that the line is undergoing enhanced absorption at these times. The observations confirm that the negative flares observed in He I 10830 Å with mono-filtergram previously were not caused by pure Doppler shifts of this spectral line. Instead, the enhanced absorption is a consequence of nonthermal ionization of helium following precipitation of high energy electrons, as found in recent numerical modeling results. In addition, though not strictly simultaneously, the IRIS observations show clear central reversals in Mg II lines and strong Doppler shifts in C II and Mg II lines at the locations where enhanced absorption in He I 10830 Å is occurring, consistent with previous observations and the modeling. In other locations the Mg II profiles appear as single peaked. Title: Magnetic Field Configuration Associated With A Slow Rise Eruptive X1.2 Flare In Active Region 11944 Authors: Yang, X.; Yurchyshyn, V.; Nita, G.; Abramenko, V.; Lim, E.; Cao, W. Bibcode: 2021AAS...23812707Y Altcode: Using multi-wavelength observations, we studied a gradual X1.2 flare that erupted on January 7, 2014, in active region (AR) NOAA 11944 located near the disk center. A fast coronal mass ejection (CME) was observed following the flare; however, it was strongly deflected in the south-west direction. We used SDO/HMI data to perform extrapolation of coronal magnetic fields and to study the evolution of AR magnetic fields before the eruption. Extrapolated data allowed us to detect a flux rope (FR) present at the eruption site several hours before the event. That was the only well-defined FR present in the AR. Although the strapping and core fields in the model have significantly changed after the flare, the model FR did not erupt. We note that a chromospheric filament was observed at the eruption site prior to and after the flare. The eruption site was located under sunspot canopy fields with a decay index of about 0.5, which is not favorable for torus instability to develop. That might have caused the erupting fields to slide along the canopy rather than vertically erupt, thus explaining the slow rise of the flare as well as the observed direction of the resulting CME. We employed sign-singularity tools to quantify the evolutionary changes in a model twist and observed current helicity data, and found rapid enhancements in the current systems in both data sets prior to the event as well as their rapid exhaustion after the event onset. Title: Critical Science Plan for the Daniel K. Inouye Solar Telescope (DKIST) Authors: Rast, Mark P.; Bello González, Nazaret; Bellot Rubio, Luis; Cao, Wenda; Cauzzi, Gianna; Deluca, Edward; de Pontieu, Bart; Fletcher, Lyndsay; Gibson, Sarah E.; Judge, Philip G.; Katsukawa, Yukio; Kazachenko, Maria D.; Khomenko, Elena; Landi, Enrico; Martínez Pillet, Valentín; Petrie, Gordon J. D.; Qiu, Jiong; Rachmeler, Laurel A.; Rempel, Matthias; Schmidt, Wolfgang; Scullion, Eamon; Sun, Xudong; Welsch, Brian T.; Andretta, Vincenzo; Antolin, Patrick; Ayres, Thomas R.; Balasubramaniam, K. S.; Ballai, Istvan; Berger, Thomas E.; Bradshaw, Stephen J.; Campbell, Ryan J.; Carlsson, Mats; Casini, Roberto; Centeno, Rebecca; Cranmer, Steven R.; Criscuoli, Serena; Deforest, Craig; Deng, Yuanyong; Erdélyi, Robertus; Fedun, Viktor; Fischer, Catherine E.; González Manrique, Sergio J.; Hahn, Michael; Harra, Louise; Henriques, Vasco M. J.; Hurlburt, Neal E.; Jaeggli, Sarah; Jafarzadeh, Shahin; Jain, Rekha; Jefferies, Stuart M.; Keys, Peter H.; Kowalski, Adam F.; Kuckein, Christoph; Kuhn, Jeffrey R.; Kuridze, David; Liu, Jiajia; Liu, Wei; Longcope, Dana; Mathioudakis, Mihalis; McAteer, R. T. James; McIntosh, Scott W.; McKenzie, David E.; Miralles, Mari Paz; Morton, Richard J.; Muglach, Karin; Nelson, Chris J.; Panesar, Navdeep K.; Parenti, Susanna; Parnell, Clare E.; Poduval, Bala; Reardon, Kevin P.; Reep, Jeffrey W.; Schad, Thomas A.; Schmit, Donald; Sharma, Rahul; Socas-Navarro, Hector; Srivastava, Abhishek K.; Sterling, Alphonse C.; Suematsu, Yoshinori; Tarr, Lucas A.; Tiwari, Sanjiv; Tritschler, Alexandra; Verth, Gary; Vourlidas, Angelos; Wang, Haimin; Wang, Yi-Ming; NSO and DKIST Project; DKIST Instrument Scientists; DKIST Science Working Group; DKIST Critical Science Plan Community Bibcode: 2021SoPh..296...70R Altcode: 2020arXiv200808203R The National Science Foundation's Daniel K. Inouye Solar Telescope (DKIST) will revolutionize our ability to measure, understand, and model the basic physical processes that control the structure and dynamics of the Sun and its atmosphere. The first-light DKIST images, released publicly on 29 January 2020, only hint at the extraordinary capabilities that will accompany full commissioning of the five facility instruments. With this Critical Science Plan (CSP) we attempt to anticipate some of what those capabilities will enable, providing a snapshot of some of the scientific pursuits that the DKIST hopes to engage as start-of-operations nears. The work builds on the combined contributions of the DKIST Science Working Group (SWG) and CSP Community members, who generously shared their experiences, plans, knowledge, and dreams. Discussion is primarily focused on those issues to which DKIST will uniquely contribute. Title: Research on Multiwavelength Isolated Bright Points Based on Deep Learning Authors: Xu, Li; Yang, Yunfei; Yan, Yihua; Zhang, Yin; Bai, Xianyong; Liang, Bo; Dai, Wei; Feng, Song; Cao, Wenda Bibcode: 2021ApJ...911...32X Altcode: Multiwavelength bright points (BPs) are taken to be cross sections of magnetic flux tubes extending from the surface of the photosphere upward to the higher photosphere. We aim to study the characteristics of isolated multiwavelength BPs using the cotemporal and cospatial TiO band and Hα line wings from the Goode Solar Telescope at Big Bear Solar Observatory. A deep-learning method, based on Track Region-based Convolutional Neural Networks, is proposed to detect, segment, and match the BPs across multiple wavelength observations, including the TiO, Hα + 1 Å, Hα - 1 Å, Hα + 0.8 Å, and Hα - 0.8 Å line wings. Based on the efficient detection and matching result with a precision of 0.98, 1283 groups of BPs matched in all five wavelengths are selected for statistics analysis. The characteristic values of the BPs observed at the same red and blue line wings are averaged. For the BPs of the TiO, averaged Hα ± 1 Å, and averaged Hα ± 0.8 Å line wings, the mean equivalent diameters are 162 ± 32, 254 ± 33, and 284 ± 28 km, respectively. The maximum intensity contrasts are 1.11 ± 0.09, 1.05 ± 0.03, and 1.05 ± 0.02 $\left\langle {I}_{\mathrm{QS}}\right\rangle $ , respectively. The mean eccentricities are 0.65 ± 0.14, 0.63 ± 0.11, and 0.65 ± 0.11, respectively. Moreover, the characteristic ratios of each Hα ± 1 Å and Hα ± 0.8 Å BP to its corresponding TiO BP are derived. Hα ± 1 Å and Hα ± 0.8 Å line wings BPs show 60% and 80% increases compared to TiO BPs, respectively. With increasing height, most BPs almost keep their shapes. This work is helpful for modeling the three-dimensional structure of flux tubes. Title: Failed Eruption Caused by Interacting Multi-current System in the Solar Corona Authors: Yang, Kai; Cao, Wenda; Wheatland, Michael S. Bibcode: 2021cosp...43E1780Y Altcode: Solar flares are one of the most energetic activities of the Sun, and are caused by current systems in the solar corona. Sometimes the eruption of a current system is confined in the solar corona and fails to trigger a coronal mass ejection or jet. A multi-current system (multi-flux rope system) makes the confined/failed eruption process more complex. To further investigate this phenomenon, we conduct a data-driven zero-beta magnetohydrodynamics (MHD) simulation using the Message Passing Interface Adaptive Mesh Refinement Versatile Advection Code (MPI-AMRVAC). The initial condition is obtained by applying the three-dimensional nonlinear force-free model to an observed vector magnetogram from HMI. From the force-free magnetic field, three flux ropes are identified in the active region, and the results are compared with H$\alpha$ observation by the Goode Solar Telescope at Big Bear Solar Observatory. The MHD simulation is driven by the time series of the observed magnetogram and the inferred photospheric plasma velocity. The simulation and observation confirm an interaction between the three flux ropes, which leads to the initial eruption. With the development of the interaction, magnetic reconnection mixes the flux ropes and leads the system to a new stable state. Title: High-resolution He I 10830 Å Narrowband Imaging for an M-class Flare. III. EUV Late Phase Authors: Wang, Ya; Ji, Haisheng; Warmuth, Alexander; Li, Ying; Cao, Wenda Bibcode: 2020ApJ...905..126W Altcode: In this paper, we report the EUV late phase for the M1.8 class flare on 2012 July 5 in the active region (AR) 11515. The late phase is shown by the prominent appearance of EUV emission at 131 Å of two additional flare loop systems (flare arcades 2 and 3, as named in this paper) other than the main flare loop (flare arcade 1), as observed by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamic Observatory (SDO). Three sets of flare arcades connect four flare ribbons, which forms an asymmetric quadrupole magnetic field configuration. While the emission from flare arcade 2, linking the pair of secondary flare ribbons, and arcade 3, linking one of the main flare ribbons and one of the secondary flare ribbons, conjointly contributes to the EUV late phase, their heating mechanisms are quite different. While the brightening of flare arcade 2 is the result of disturbance created by the eruption of EUV hot channels to the overlying coronal magnetic field, the heating of flare arcade 3 was closely associated with two rapid contractions of the overlying filament threads during the partial eruption of the filament. The contractions are discernible in He I 10830 Å images and have signatures in the EUV wavelengths of AIA. The two rapid contractions are the result of a sudden drop in magnetic pressure after the eruption of two hot channels. Clear evidence suggests that magnetic reconnection may occur between the contracting filament threads and the low-lying magnetic field. Title: CYRA: the cryogenic infrared spectrograph for the Goode Solar Telescope in Big Bear Authors: Yang, Xu; Cao, Wenda; Gorceix, Nicolas; Plymate, Claude; Shumoko, Sergey; Bai, XianYong; Penn, Matt; Ayres, Thomas; Coulter, Roy; Goode, Philip R. Bibcode: 2020SPIE11447E..AGY Altcode: 2020arXiv200811320Y CYRA (CrYogenic solar spectrogRAph) is a facility instrument of the 1.6-meter Goode Solar Telescope (GST) at the Big Bear Solar Observatory (BBSO). CYRA focuses on the study of the near-infrared solar spectrum between 1 and 5 microns, an under-explored region which is not only fertile ground for photospheric magnetic diagnostics but also allows a unique window into the chromosphere lying atop the photosphere. CYRA is the first-ever fully cryogenic spectrograph in any solar observatory with its two predecessors, on the McMath-Pierce and Mees Telescopes, being based on warm optics except for the detectors and order sorting filters. CYRA is used to probe magnetic fields in various solar features and the quiet photosphere. CYRA measurements will allow new and better 3D extrapolations of the solar magnetic field and will provide more accurate boundary conditions for solar activity models. The superior spectral resolution of 150,000 and better allows enhanced observations of the chromosphere in the carbon monoxide (CO) spectral bands and will yield a better understanding of energy transport in the solar atmosphere. CYRA is divided into two optical sub-systems: The Fore-Optics Module and the Spectrograph. The Spectrograph is the heart of the instrument and contains the IR detector, grating, slits, filters, and imaging optics all in a cryogenically cooled Dewar (cryostat). The sensor is a 2048 by 2048 pixel HAWAII 2 array produced by Teledyne Scientific and Imaging, LLC. The cryostat interior and the readout electronics are maintained at 90 Kelvin by helium refrigerant-based cryo-coolers, while the IR array is cooled to 30 Kelvin. The Fore-Optics Module de-rotates and stabilizes the solar image, provides scanning capabilities and transfers the GST image to the Spectrograph. CYRA has been installed and is undergoing its commissioning phase. This paper reports on the design, implementation, and operation of CYRA in detail. The preliminary scientific results have been highlighted as well. Title: Doppler shift oscillations of a sunspot detected by CYRA and IRIS Authors: Li, D.; Yang, X.; Bai, X. Y.; Su, J. T.; Ning, Z. J.; Cao, W.; Deng, Y. Y. Bibcode: 2020A&A...642A.231L Altcode: 2020arXiv200906942L Context. The carbon monoxide (CO) molecular line at around 46655 Å in solar infrared spectra is often used to investigate the dynamic behavior of the cold heart of the solar atmosphere, i.e., sunspot oscillation, especially at the sunspot umbra.
Aims: We investigated sunspot oscillation at Doppler velocities of the CO 7-6 R67 and 3-2 R14 lines that were measured by the Cryogenic Infrared Spectrograph (CYRA), as well as the line profile of Mg II k line that was detected by the Interface Region Imaging Spectrograph (IRIS).
Methods: A single Gaussian function is applied to each CO line profile to extract the line shift, while the moment analysis method is used for the Mg II k line. Then the sunspot oscillation can be found in the time-distance image of Doppler velocities, and the quasi-periodicity at the sunspot umbra are determined from the wavelet power spectrum. Finally, the cross-correlation method is used to analyze the phase relation between different atmospheric levels.
Results: At the sunspot umbra, a periodicity of roughly 5 min is detected at the Doppler velocity range of the CO 7-6 R67 line that formed in the photosphere, while a periodicity of around 3 min is discovered at the Doppler velocities of CO 3-2 R14 and Mg II k lines that formed in the upper photosphere or the temperature minimum region and the chromosphere. A time delay of about 2 min is measured between the strong CO 3-2 R14 line and the Mg II k line.
Conclusions: Based on the spectroscopic observations from the CYRA and IRIS, the 3 min sunspot oscillation can be spatially resolved in the Doppler shifts. It may come from the upper photosphere or the temperature minimum region and then propagate to the chromosphere, which might be regarded as a propagating slow magnetoacoustic wave. Title: Formation of a tiny flux rope in the center of an active region driven by magnetic flux emergence, convergence, and cancellation Authors: Zheng, Ruisheng; Chen, Yao; Wang, Bing; Song, Hongqiang; Cao, Wenda Bibcode: 2020A&A...642A.199Z Altcode: 2020arXiv200904082Z
Aims: Flux ropes are generally believed to be core structures of solar eruptions that are significant for the space weather, but their formation mechanism remains intensely debated. We report on the formation of a tiny flux rope beneath clusters of active region loops on 2018 August 24.
Methods: Combining the high-quality multiwavelength observations from multiple instruments, we studied the event in detail in the photosphere, chromosphere, and corona.
Results: In the source region, the continual emergence of two positive polarities (P1 and P2) that appeared as two pores (A and B) is unambiguous. Interestingly, P2 and Pore B slowly approached P1 and Pore A, implying a magnetic flux convergence. During the emergence and convergence, P1 and P2 successively interacted with a minor negative polarity (N3) that emerged, which led to a continuous magnetic flux cancellation. As a result, the overlying loops became much sheared and finally evolved into a tiny twisted flux rope that was evidenced by a transient inverse S-shaped sigmoid, the twisted filament threads with blueshift and redshift signatures, and a hot channel.
Conclusions: All the results show that the formation of the tiny flux rope in the center of the active region was closely associated with the continuous magnetic flux emergence, convergence, and cancellation in the photosphere. Hence, we suggest that the magnetic flux emergence, convergence, and cancellation are crucial for the formation of the tiny flux rope.

Movies associated to Figs. 2, 4, and 7 are available at https://www.aanda.org Title: High-resolution Observations of Small-scale Flux Emergence by GST Authors: Wang, Jiasheng; Liu, Chang; Cao, Wenda; Wang, Haimin Bibcode: 2020ApJ...900...84W Altcode: 2020arXiv200906717W Recent observations demonstrated that emerging flux regions, which constitute the early stage of solar active regions, consist of emergence of numerous small-scale magnetic elements. They in turn interact, merge, and form mature sunspots. However, observations of fine magnetic structures on photosphere with subarcsecond resolution are very rare due to limitations of observing facilities. In this work, taking advantage of the high resolution of the 1.6 m Goode Solar Telescope, we jointly analyze vector magnetic fields, continuum images, and Hα observations of NOAA AR 12665 on 2017 July 13, with the goal of understanding the signatures of small-scale flux emergence, as well as their atmospheric responses as they emerge through multiple heights in the photosphere and chromosphere. Under such a high resolution of 0"1-0"2, our results confirm two kinds of small-scale flux emergence: magnetic flux sheet emergence associated with the newly forming granules, and the traditional magnetic flux loop emergence. With direct imaging in the broadband TiO, we observe that both types of flux emergence are associated with darkening of granular boundaries, while only flux sheets elongate granules along the direction of emerging magnetic fields and expand laterally. With a life span of 10 ∼ 15 minutes, the total emerged vertical flux is on the order of 1018 Mx for both types of emergence. The magnitudes of the vertical and horizontal fields are comparable in the flux sheets, while the former is stronger in flux loops. Hα observations reveal transient brightenings in the wings in the events of magnetic loop emergence, which are most probably the signatures of Ellerman bombs. Title: Spectral Diagnostics of Solar Photospheric Bright Points Authors: Hao, Q.; Fang, C.; Ding, M. D.; Li, Z.; Cao, Wenda Bibcode: 2020ApJ...900..130H Altcode: 2020arXiv200709675H Through the use of the high-resolution spectral data and the broadband imaging obtained with the Goode Solar Telescope at the Big Bear Solar Observatory on 2013 June 6, the spectra of three typical photospheric bright points (PBPs) have been analyzed. Based on the Hα and Ca II 8542 Å line profiles, as well as the TiO continuum emission, for the first time, the non-LTE semiempirical atmospheric models for the PBPs are computed. The attractive characteristic is the temperature enhancement in the lower photosphere. The temperature enhancement is about 200-500 K at the same column mass density as in the atmospheric model of the quiet-Sun. The total excess radiative energy of a typical PBP is estimated to be 1 × 1027-2 × 1027 erg, which can be regarded as the lower limit energy of the PBPs. The radiation flux in the visible continuum for the PBPs is about 5.5 × 1010 erg cm-2 s-1. Our result also indicates that the temperature in the atmosphere above PBPs is close to that of a plage. It gives clear evidence that PBPs may contribute significantly to the heating of the plage atmosphere. Using our semiempirical atmospheric models, we estimate self-consistently the average magnetic flux density B in the PBPs. It is shown that the maximum value is about 1 kG, and it decreases toward both higher and lower layers, reminding us of the structure of a flux tube between photospheric granules. Title: Date Co-alignment for Ground-Based High-Resolution Solar Imaging Authors: Yang, X.; Ji, K.; Cao, W.; Yurchyshyn, V.; Xu, Z. Bibcode: 2020SPD....5120501Y Altcode: The multi-wavelength analysis is a well-spread method in solar physics studies, and the community increasingly relies on coordinated observations involving multiple instruments. The calibration of heliographic coordinates is therefore vital for the co-alignment of such multi-instrument, multi-wavelength data. However, this is particularly difficult for ground-based high-resolution observations because of the limited field of view. Manually co-aligning data with low-contrast features (e.g., photospheric observations of quiet Sun regions) between different telescopes requires exceptional efforts and patience. Here, we developed a technique to accurately determine coordinates of high-resolution images acquired by the Goode Solar Telescope (GST) at the Big Bear Solar Observatory. The technique employs a scale-invariant feature transform (SIFT) method, which performs without human interference. With this new approach, we co-aligned multi-wavelength GST data sets to the continuum intensity data from the Helioseismic and Magnetic Imager (HMI) precisely. The inferred heliographic coordinates are saved in each FITS file header, which is compatible with the common mapping methods available in the Solar SoftWare (SSW) package. GST data are fully open to the scientific community, and a substantial portion of observing time on the GST opens to the community as well. Title: Mare Deposits Identification and Feature Analysis in Mare Australe Based on CE-2 CELMS Data Authors: Meng, Z. G.; Chen, S. B.; Zheng, Y. C.; Cheng, W. M.; Zhu, Y. Q.; Cai, Z. C.; Zhang, Y. Z.; Cao, W.; Hou, L. L. Bibcode: 2020JGRE..12506330M Altcode: The microwave signal has the penetration capability, which provides a potential chance to improve understanding of the mare deposits and the formation process of Mare Australe, a complex, extensive, and poorly understood region on the Moon. In this paper, the Chang'E-2 microwave radiometer (CELMS) data were selected and processed to evaluate the microwave thermal emission features of the mare deposits in Mare Australe. After comparison, the dTB map at 3.0 GHz is employed. The results are as follows. (a) The possible cryptomare is much more extensive in Australe region than that identified with optical data. (b) The basaltic volcanism is re-understood as three major episodes. (c) The high dTB anomaly is interpreted as the location of the vent areas in the mare patches. (d) The K-means algorithm was first used to process the CELMS data, and the identified linear and ring structures indicate some important information about the formation processes of Mare Australe. These special findings will be of fundamental significance to better understand the basaltic volcanism and the evolution of the lunar surface. Title: Astronomical Massive Data Processing Technology Authors: Wang, Feng; Cao, Wenda; Bastieri, Denis; Fan, Junhui; Cui, Chenzhou Bibcode: 2020AdAst2020E...5W Altcode: No abstract at ADS Title: Rapid Evolution of Type II Spicules Observed in Goode Solar Telescope On-disk Hα Images Authors: Yurchyshyn, Vasyl; Cao, Wenda; Abramenko, Valentina; Yang, Xu; Cho, Kyung-Suk Bibcode: 2020ApJ...891L..21Y Altcode: 2020arXiv200504253Y We analyze ground-based chromospheric data acquired at a high temporal cadence of 2 s in wings of the Hα spectral line using the Goode Solar Telescope operating at the Big Bear Solar Observatory. We inspected a 30 minute long Hα-0.08 nm data set to find that rapid blueshifted Hα excursions (RBEs), which are a cool component of type II spicules, experience very rapid morphological changes on timescales of the order of 1 s. Unlike typical reconnection jets, RBEs very frequently appear in situ without any clear evidence of Hα material being injected from below. Their evolution includes inverted "Y," "V," "N," and parallel splitting (doubling) patterns as well as sudden formation of a diffuse region followed by branching. We also find that the same feature may undergo several splitting episodes within about a 1 minute time interval. Title: Generation of solar spicules and subsequent atmospheric heating Authors: Samanta, Tanmoy; Tian, Hui; Yurchyshyn, Vasyl; Peter, Hardi; Cao, Wenda; Sterling, Alphonse; Erdélyi, Robertus; Ahn, Kwangsu; Feng, Song; Utz, Dominik; Banerjee, Dipankar; Chen, Yajie Bibcode: 2019Sci...366..890S Altcode: 2020arXiv200602571S Spicules are rapidly evolving fine-scale jets of magnetized plasma in the solar chromosphere. It remains unclear how these prevalent jets originate from the solar surface and what role they play in heating the solar atmosphere. Using the Goode Solar Telescope at the Big Bear Solar Observatory, we observed spicules emerging within minutes of the appearance of opposite-polarity magnetic flux around dominant-polarity magnetic field concentrations. Data from the Solar Dynamics Observatory showed subsequent heating of the adjacent corona. The dynamic interaction of magnetic fields (likely due to magnetic reconnection) in the partially ionized lower solar atmosphere appears to generate these spicules and heat the upper solar atmosphere. Title: Light Bridge Brightening and Plasma Ejection Driven by a Magnetic Flux Emergence Event Authors: Yang, Xu; Yurchyshyn, Vasyl; Ahn, Kwangsu; Penn, Matt; Cao, Wenda Bibcode: 2019ApJ...886...64Y Altcode: Observations with the Goode Solar Telescope (GST) are presented here showing that the emergence of 1.91 × 1018 Mx of new magnetic flux occurred at the edge of a filamentary light bridge (LB). This emergence was accompanied by brightness enhancement of a photospheric overturning convection cell (OCC) at the endpoints of the emerging magnetic structure. We present an analysis of the origin and the dynamics of this event using high-resolution GST Fe I 1564.85 nm vector magnetic field data, TiO photospheric, and Hα chromospheric images. The emerged structure was 1.5 × 0.3 Mm in size at the peak of development and lasted for 17 minutes. Doppler observations showed presence of systematic upflows before the appearance of the magnetic field signal and downflows during the decay phase. Changes in the orientation of the associated transverse fields, determined from the differential angle, suggest the emergence of a twisted magnetic structure. A fan-shaped jet was observed to be spatially and temporally correlated with the endpoint of the OCC intruding into the LB. Our data suggest that the emerging fields may have reconnected with the magnetic fields in the vicinity of the LB, which could lead to the formation of the jet. Our observation is the first report of flux emergence within a granular LB with evidence in the evolution of vector magnetic field, as well as photosphere convection motions, and supports the idea that the impulsive jets above the LB are caused by magnetic reconnection. Title: High-resolution Observations of Dynamics of Superpenumbral Hα Fibrils Authors: Jing, Ju; Li, Qin; Liu, Chang; Lee, Jeongwoo; Xu, Yan; Cao, Wenda; Wang, Haimin Bibcode: 2019ApJ...880..143J Altcode: We present high-resolution Hα observations of a small solar pore in NOAA active region 12661, using the 1.6 m Goode Solar Telescope equipped with high-order adaptive optics at Big Bear Solar Observatory. The observations reveal copious fine-scale chromospheric superpenumbral fibrils (with an average cross-sectional width of ∼0.″17 ± 0.″03), along with associated transit and intermittent flows with apparent speeds of 5-14 km s-1. Wavelet analysis and the spatio-temporal pattern of superpenumbral fibrils suggest that the observed flows along fibrils are not likely an oscillation/wave phenomenon. Based on our pseudo-Dopplergrams, we suggest that the observed flows may be a phenomenon similar to inverse Evershed flows in the chromosphere. The three-dimensional potential field model indicates that the pore and the surrounding fibrils are enclosed by fan-field lines forming a separatrix dome configuration. Such a magnetically confined configuration may help to maintain the steadfastness of the superpenumbral fibril dynamics. Title: High-resolution Spectroscopic Imaging of Counter-streaming Motions in Solar Active Region Magnetic Loops Authors: Yang, Xu; Cao, Wenda; Ji, Haisheng; Hashim, Parida; Shen, Jinhua Bibcode: 2019ApJ...881L..25Y Altcode: We carried out high-resolution spectroscopic imaging in He I 10830 Å and H α for a set of active region (NOAA 12569) magnetic loops of different sizes (classified into short and long loops) with the Goode Solar Telescope at the Big Bear Solar Observatory on 2016 July 18. The long loops take the form of an chromospheric arch filament system, yet their extreme ultraviolet (EUV) counterparts are observed by the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory. Animations of blue- and red-wing images give counter-streaming motions; i.e., chromospheric absorption features in blue- and red-wing images move in opposite directions at different strands. The moving pattern is detected with the local correlation tracking method and confirmed by Doppler shifts. We speculate that, combined with the results of wavelet analysis that gives obvious 4 minute oscillation along trailing polarity, counter-streaming motions for short loops could be powered by p-mode leakage. However, for counter-streaming motions in long loops, we show that unidirectional mass flows in two opposite directions are accompanied with simultaneous weak EUV brightenings. Heating processes, probably by magnetic reconnection at footpoints, may have occurred. In addition, plasma flows along the magnetic loops, tracked with absorption features in He I 10830 Å, are found to be ejected from and drained out into inter-granule lane areas at different ends of the loop system. Title: Counter-streaming motions in active region magnetic arches observed by Helium I 10830Å spectroscopy Authors: Yang, Xu; Ya, Wang; Ji, Haisheng; Cao, Wenda Bibcode: 2019AAS...23421706Y Altcode: We report the first high-resolution observations of counter-streaming motions in the active region magnetic arches with Helium I 10830 Å spectroscopy, achieved by the Goode Solar Telescope at Big Bear Solar Observatory. Our observations reveal that the counter-streaming motions are due to unidirectional mass flows along alternative arches, rather than the longitudinal oscillations of filament threads as in some solar filaments. Mass flow, rooting in the magnetic network region, are pumped up from and down to the inter-granulation lanes. The apparent speed of the flow is around 15-50 km s-1 in the He I 10830 Å blue wing and 5-15 km s-1 in the red wing. Co-spatial brightenings in Atmospheric Imaging Assembly 304 Å and 171 Å images are witnessed at the same time, indicating the possible corresponding heating process. The oscillation power peaks around 4 minutes in the roots region of the arches, however, the mass flows inside the long arches seem to be continuous. Title: High-resolution Observations of Dynamics of Superpenumbral Hα Fibrils Authors: Jing, Ju; Li, Qin; Liu, Chang; Lee, Jeongwoo; Xu, Yan; Cao, Wenda; Wang, Haimin Bibcode: 2019AAS...23430502J Altcode: We present unprecedented high-resolution Hα observations of a small solar pore in NOAA Active Region 12661, using the 1.6 m Goode Solar Telescope (GST) equipped with high-order adaptive optics at Big Bear Solar Observatory (BBSO). The observations reveal copious fine-scale chromospheric superpenumbral fibrils (with a cross-sectional width of 0.15") around the pore, along with associated transit and intermittent flows with apparent speeds of 5-20 km s-1. The wavelet analysis suggests that the observed flows along fibrils are not likely a manifestation of oscillations, but rather collections of actual counterstreaming mass motions. The observed flow is interpreted as siphon flow. In addition, the three-dimensional potential field model indicates that the pore and the surrounding fibrils are enclosed by fan field lines forming a separatrix dome configuration. We suggest that such a magnetically confined configuration may help to maintain the steadfastness of the superpenumbral fibril dynamics. Title: Multi-wavelength Multi-height Study of Super Strong Surface and Coronal Magnetic Fields in Active Region 12673 Authors: Wang, Haimin; Chen, Bin; Jing, Ju; Yu, Sijie; Liu, Chang; Yurchyshyn, Vasyl B.; Ahn, Kwangsu; Okamoto, Takenori; Toriumi, Shin; Cao, Wenda; Gary, Dale E. Bibcode: 2019AAS...23440205W Altcode: Using the joint observations of Goode Solar telescope (GST), Expanded Owens Valley Solar Array (EOVSA), Solar Dynamics Observatory (SDO) and Hinode, we study the Solar Active Region (AR) 12673 in September 2017, which is the most flare productive AR in the solar cycle 24. GST observations show the strong photospheric magnetic fields (nearly 6000 G) in polarity inversion line (PIL) and apparent photospheric twist. Consistent upward flows are also observed in Dopplergrams of Hinode, HMI and GST at the center part of that section of PIL, while the down flows are observed in two ends, indicating that the structure was rising from subsurface. Combining Non-Linear Force Free Extrapolation and EOVSA microwave imaging spectroscopy, we also look into the coronal structure of magnetic fields in this unusual AR, including the evolution before and after the X9.3 flare on September 6, 2017. Coronal fields between 1000 and 2000 gauss are found above the flaring PIL at the height range between 8 and 4Mm, outlining the structure of a fluxrope or sheared arcade. Title: Calibration of the Instrumental Crosstalk for the Near-IR Imaging Spectropolarimeter at the NST Authors: Ahn, K.; Cao, W. Bibcode: 2019ASPC..526..317A Altcode: 2019arXiv190912970A The Near-IR Imaging Spectropolarimeter (NIRIS) is a polarimeter that is installed at the New Solar Telescope at Big Bear Solar Observatory. This instrument takes advantage of the highest spatial resolution and flux. The primary mirror is an off-axis type, so it was our interest to evaluate its contribution to the crosstalk among the Stokes parameters since we could not put our calibration optics before the mirror. We would like to present our efforts to compensate for the crosstalk among Stokes profiles caused by the relay optics from the telescope to the detector. The overall data processing pipeline is also introduced. Title: Flame-like Ellerman Bombs and Their Connection to Solar Ultraviolet Bursts Authors: Chen, Yajie; Tian, Hui; Peter, Hardi; Samanta, Tanmoy; Yurchyshyn, Vasyl; Wang, Haimin; Cao, Wenda; Wang, Linghua; He, Jiansen Bibcode: 2019ApJ...875L..30C Altcode: 2019arXiv190301981C Ellerman bombs (EBs) are small-scale intense brightenings in Hα wing images, which are generally believed to be signatures of magnetic reconnection around the temperature minimum region of the solar atmosphere. They have a flame-like morphology when observed near the solar limb. Recent observations from the Interface Region Imaging Spectrograph (IRIS) reveal another type of small-scale reconnection event called an ultraviolet (UV) burst, in the lower solar atmosphere. Though previous observations have shown a clear coincidence between the occurrence of some UV bursts and EBs, the exact relationship between these two phenomena is still debated. We investigate the spatial and temporal relationship between flame-like EBs and UV bursts using joint near-limb observations between the 1.6 m Goode Solar Telescope (GST) and IRIS. In total, 161 EBs have been identified from the GST observations, and ∼20 of them reveal signatures of UV bursts in the IRIS images. Interestingly, we find that these UV bursts have a tendency to appear at the upper parts of their associated flame-like EBs. The intensity variations of most EB-related UV bursts and their corresponding EBs match well. Our results suggest that some of these UV bursts and EBs likely form at different heights during a common reconnection process. Title: Signatures of Magnetic Reconnection at the Footpoints of Fan-shaped Jets on a Light Bridge Driven by Photospheric Convective Motions Authors: Bai, Xianyong; Socas-Navarro, Hector; Nóbrega-Siverio, Daniel; Su, Jiangtao; Deng, Yuanyong; Li, Dong; Cao, Wenda; Ji, Kaifan Bibcode: 2019ApJ...870...90B Altcode: 2018arXiv181103723B Dynamical jets are generally found on light bridges (LBs), which are key to studying sunspot decay. So far, their formation mechanism is not fully understood. In this paper, we used state-of-the-art observations from the Goode Solar Telescope, the Interface Region Imaging Spectrograph, the Spectro-polarimeter on board Hinode, and the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory to analyze the fan-shaped jets on LBs in detail. A continuous upward motion of the jets in the ascending phase is found from the Hα velocity that lasts for 12 minutes and is associated with the Hα line wing enhancements. Two mini jets appear on the bright fronts of the fan-shaped jets visible in the AIA 171 and 193 Å channels, with a time interval as short as 1 minute. Two kinds of small-scale convective motions are identified in the photospheric images, along with the Hα line wing enhancements. One seems to be associated with the formation of a new convection cell, and the other manifests as the motion of a dark lane passing through the convection cell. The finding of three-lobe Stokes V profiles and their inversion with the NICOLE code indicate that there are magnetic field lines with opposite polarities in LBs. From the Hα -0.8 Å images, we found ribbon-like brightenings propagating along the LBs, possibly indicating slipping reconnection. Our observation supports the idea that the fan-shaped jets under study are caused by magnetic reconnection, and photospheric convective motions play an important role in triggering the magnetic reconnection. Title: Evolution of Photospheric Vector Magnetic Field Associated with Moving Flare Ribbons as Seen by GST Authors: Liu, Chang; Cao, Wenda; Chae, Jongchul; Ahn, Kwangsu; Prasad Choudhary, Debi; Lee, Jeongwoo; Liu, Rui; Deng, Na; Wang, Jiasheng; Wang, Haimin Bibcode: 2018ApJ...869...21L Altcode: 2018arXiv181011733L The photospheric response to solar flares, also known as coronal back reaction, is often observed as sudden flare-induced changes in the vector magnetic field and sunspot motions. However, it remains obscure whether evolving flare ribbons, the flare signature closest to the photosphere, are accompanied by changes in vector magnetic field therein. Here we explore the relationship between the dynamics of flare ribbons in the chromosphere and variations of magnetic fields in the underlying photosphere, using high-resolution off-band Hα images and near-infrared vector magnetograms of the M6.5 flare on 2015 June 22 observed with the 1.6 m Goode Solar Telescope. We find that changes of photospheric fields occur at the arrival of the flare ribbon front, thus propagating analogously to flare ribbons. In general, the horizontal field increases and the field lines become more inclined to the surface. When ribbons sweep through regions that undergo a rotational motion, the fields transiently become more vertical with decreased horizontal field and inclination angle, and then restore and/or become more horizontal than before the ribbon arrival. The ribbon propagation decelerates near the sunspot rotation center, where the vertical field becomes permanently enhanced. Similar magnetic field changes are discernible in magnetograms from the Helioseismic and Magnetic Imager (HMI), and an inward collapse of coronal magnetic fields is inferred from the time sequence of nonlinear force-free field models extrapolated from HMI magnetograms. We conclude that photospheric fields respond nearly instantaneously to magnetic reconnection in the corona. Title: Roadmap for Reliable Ensemble Forecasting of the Sun-Earth System Authors: Nita, Gelu; Angryk, Rafal; Aydin, Berkay; Banda, Juan; Bastian, Tim; Berger, Tom; Bindi, Veronica; Boucheron, Laura; Cao, Wenda; Christian, Eric; de Nolfo, Georgia; DeLuca, Edward; DeRosa, Marc; Downs, Cooper; Fleishman, Gregory; Fuentes, Olac; Gary, Dale; Hill, Frank; Hoeksema, Todd; Hu, Qiang; Ilie, Raluca; Ireland, Jack; Kamalabadi, Farzad; Korreck, Kelly; Kosovichev, Alexander; Lin, Jessica; Lugaz, Noe; Mannucci, Anthony; Mansour, Nagi; Martens, Petrus; Mays, Leila; McAteer, James; McIntosh, Scott W.; Oria, Vincent; Pan, David; Panesi, Marco; Pesnell, W. Dean; Pevtsov, Alexei; Pillet, Valentin; Rachmeler, Laurel; Ridley, Aaron; Scherliess, Ludger; Toth, Gabor; Velli, Marco; White, Stephen; Zhang, Jie; Zou, Shasha Bibcode: 2018arXiv181008728N Altcode: The authors of this report met on 28-30 March 2018 at the New Jersey Institute of Technology, Newark, New Jersey, for a 3-day workshop that brought together a group of data providers, expert modelers, and computer and data scientists, in the solar discipline. Their objective was to identify challenges in the path towards building an effective framework to achieve transformative advances in the understanding and forecasting of the Sun-Earth system from the upper convection zone of the Sun to the Earth's magnetosphere. The workshop aimed to develop a research roadmap that targets the scientific challenge of coupling observations and modeling with emerging data-science research to extract knowledge from the large volumes of data (observed and simulated) while stimulating computer science with new research applications. The desire among the attendees was to promote future trans-disciplinary collaborations and identify areas of convergence across disciplines. The workshop combined a set of plenary sessions featuring invited introductory talks and workshop progress reports, interleaved with a set of breakout sessions focused on specific topics of interest. Each breakout group generated short documents, listing the challenges identified during their discussions in addition to possible ways of attacking them collectively. These documents were combined into this report-wherein a list of prioritized activities have been collated, shared and endorsed. Title: Dark Structures in Sunspot Light Bridges Authors: Zhang, Jingwen; Tian, Hui; Solanki, Sami K.; Wang, Haimin; Peter, Hardi; Ahn, Kwangsu; Xu, Yan; Zhu, Yingjie; Cao, Wenda; He, Jiansen; Wang, Linghua Bibcode: 2018ApJ...865...29Z Altcode: 2018arXiv180900146Z We present unprecedented high-resolution TiO images and Fe I 1565 nm spectropolarimetric data of two light bridges taken by the 1.6 m Goode Solar Telescope at Big Bear Solar Observatory. In the first light bridge (LB1), we find striking knot-like dark structures within the central dark lane. Many dark knots show migration away from the penumbra along the light bridge. The sizes, intensity depressions, and apparent speeds of their proper motion along the light bridges of 33 dark knots identified from the TiO images are mainly in the ranges of 80 ∼ 200 km, 30% ∼ 50%, and 0.3 ∼ 1.2 km s-1, respectively. In the second light bridge (LB2), a faint central dark lane and striking transverse intergranular lanes were observed. These intergranular lanes have sizes and intensity depressions comparable to those of the dark knots in LB1 and also migrate away from the penumbra at similar speeds. Our observations reveal that LB2 is made up of a chain of evolving convection cells, as indicated by patches of blueshift surrounded by narrow lanes of redshift. The central dark lane generally corresponds to blueshifts, supporting the previous suggestion of central dark lanes being the top parts of convection upflows. In contrast, the intergranular lanes are associated with redshifts and located at two sides of each convection cell. The magnetic fields are stronger in intergranular lanes than in the central dark lane. These results suggest that these intergranular lanes are manifestations of convergent convective downflows in the light bridge. We also provide evidence that the dark knots observed in LB1 may have a similar origin. Title: Formation of an Active Region Filament Driven By a Series of Jets Authors: Wang, Jincheng; Yan, Xiaoli; Qu, Zhongquan; UeNo, Satoru; Ichimoto, Kiyoshi; Deng, Linhua; Cao, Wenda; Liu, Zhong Bibcode: 2018ApJ...863..180W Altcode: 2018arXiv180700992W We present a formation process of a filament in active region NOAA 12574 during the period from 2016 August 11 to 12. Combining the observations of the Global Oscillation Network Group Hα, the Hida spectrum, and the Solar Dynamics Observatory/AIA 304 Å, the formation process of the filament is studied. It is found that cool material (T ∼ 104 K) is ejected by a series of jets originating from the western footpoint of the filament. Simultaneously, the magnetic flux emerged from the photosphere in the vicinity of the western footpoint of the filament. These observations suggest that cool material in the low atmosphere can be directly injected into the upper atmosphere and the jets are triggered by the magnetic reconnection between pre-existing magnetic fields and new emerging magnetic fields. A detailed study of a jet at 18:02 UT on August 11 with GST/BBSO TiO observations revealed that some dark threads appeared in the vicinity of the western footpoint after the jet and the projection velocity of plasma along the filament axis was about 162.6 ± 5.4 km s-1. Using these observations of the Domeless Solar Telescope/Hida, we find that the injected plasma by a jet at 00:42 UT on August 12 was rotating. Therefore, we conclude that the jets not only supplied the material for the filament, but also injected the helicity into the filament simultaneously. Comparing the quantity of mass injection by the jets with the mass of the filament, we conclude that the estimated mass loading by the jets is sufficient to account for the mass in the filament. Title: Magnetic Flux Emergence Triggered Light Bridge Brightening and Reconnection Jets Authors: Yang, Xu; Cao, Wenda; Yurchyshyn, Vasyl; Ahn, Kwangsu Bibcode: 2018cosp...42E3744Y Altcode: Light bridges (LBs) are elongated, bright, granular structures that divide the umbra of a large and complex sunspot into two or more umbral regions with the same magnetic polarity. Surge-like activities are common phenomenon appear above the LBs which always accompanied by the magnetic flux emergence process. Former works tried to interpret the triggering mechanism for them, however they often lacked the support of high spatial and temporal resolution vector magnetic measurement. Our recent Observation shows a strong magnetic flux emergence happened at the edge of a filamentary Light Bridge (LB) and accompanied by brightness enhancement of photospheric granulations at the endpoints of the emerged magnetic structure. We study the origin and dynamics of this magnetic flux emergence event with high resolution Fe I 1.56 μm polarimetry magnetogram, TiO photosphere image and Hα chromosphere image from the Goode Solar Telescope. The emerged magnetic structure was 1.5 Mm × 0.3 Mm in size at its peak time and lasted for 17 minutes. Doppler map detected upflows before its formation and downflows during the destruction. The magnetic orientation change was obtained by calculating the shear angle and plotting the magnetic field vectors. The result indicates that the new emerged more transverse magnetic field reconnected with the pre-existing more vertical field, which triggered the fan-shaped jets. The expanding fields at the endpoints due to the flux emergence pushed and compressed the existing granulations and led to their enhanced brightness. Title: Project of a New 2.5m Solar Telescope Authors: Fang, Cheng; Chen, P. F.; Li, Zhen; Cao, Wenda; Hao, Qi; Ding, Mingde; Gu, Baizhong; Yuan, Xiangyan Bibcode: 2018cosp...42E1042F Altcode: A project of a 2.5m Solar Telescope has been worked out in China. It is the first facility in the world with a special innovation design and can conduct both high-resolution solar observations and the large-field of view (FOV) night survey. Its scientific objectives cover solar physics and time-domain astronomy, all of which are recent hot topics in astronomy. As a large on-axis solar telescope in the world with a larger FOV (7') than all the large solar telescopes operating at present, it can provide unprecedented high-resolution solar imaging and magnetic field data, which can help us obtain breakthrough achievements on the study of solar active regions and solar eruptions. The data are also very useful for the study of space weather. As a large telescope in China, the telescope is very unique in continuously monitoring short-time transient events by filling the gap in the specific time-zone. Moreover, the telescope can make essential contribution to training the graduate and undergraduate students majoring in observational astronomy. Title: Project of a New 2.5m Solar Telescope Authors: Fang, Cheng; Chen, P. F.; Li, Zhen; Cao, Wenda; Hao, Qi; Ding, Mingde; Gu, Baizhong; Yuan, Xiangyan Bibcode: 2018cosp...42E1041F Altcode: A project of a 2.5m Solar Telescope has been worked out in China. It is the first facility in the world with a special innovation design and can conduct both high-resolution solar observations and the large-field of view (FOV) night survey. Its scientific objectives cover solar physics and time-domain astronomy, all of which are recent hot topics in astronomy. As a large on-axis solar telescope in the world with a larger FOV (7') than all the large solar telescopes operating at present, it can provide unprecedented high-resolution solar imaging and magnetic field data, which can help us obtain breakthrough achievements on the study of solar active regions and solar eruptions. The data are also very useful for the study of space weather. As a large telescope in China, the telescope is very unique in continuously monitoring short-time transient events by filling the gap in the specific time-zone. Moreover, the telescope can make essential contribution to training the graduate and undergraduate students majoring in observational astronomy. Title: High-resolution He I 10830 Å Narrowband Imaging for an M-class Flare. II. Multiple Hot Channels: Their Origin and Destination Authors: Wang, Ya; Su, Yingna; Shen, Jinhua; Yang, Xu; Cao, Wenda; Ji, Haisheng Bibcode: 2018ApJ...859..148W Altcode: In this paper, we report our second-part result for the M1.8 class flare on 2012 July 5, with an emphasis on the initiation process for the flare-associated filament eruption. The data set consists of high-resolution narrowband images in He I 10830 Å and broadband images in TiO 7057 Å taken at Big Bear Solar Observatory with the 1.6 m aperture Goode Solar Telescope. EUV images in different passbands observed by the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory are used to distinguish hot plasma from cool plasma structures during the flare process. High-resolution 10830 Å images clearly show that, below the horizontal fibrils, which correspond to the filament’s spine in full-disk Hα images, a sheared arch filament system (AFS) lies across the penumbra and surrounding satellite sunspots, between which continuous shearing motion is observed. Before the eruption, three microflares occurred successively and were followed by the appearance of three EUV hot channels. Two hot channels erupted, producing two flaring sites and two major peaks in GOES soft X-ray light curves; however, one hot channel’s eruption failed. The 10830 Å imaging enables us to trace the first two hot channels to their very early stage, which is signified by the rising of the AFS after the first two precursors. Continuous flux emergence and localized flare-associated cancellation are observed under the AFS. In addition, EUV ejections were observed during the formation of the EUV hot channels. These observations support the fact that the hot channels are the result of magnetic reconnections during precursors. Title: Evolution of Photospheric Magnetic Field Associated with Flare Ribbons as Seen by GST Authors: Liu, Chang; Cao, Wenda; Xu, Yan; Ahn, Kwangsu; Wang, Haimin Bibcode: 2018tess.conf40803L Altcode: Solar flares produce signatures at various wavelengths and heights, among which the response of photospheric magnetic and flow fields to flare reconnection has drawn increasing attention recently. Such a response has been evidenced as sudden flare-induced photospheric structural evolution, especially vector magnetic field changes and sunspot rotations. However, previous studies on this coronal back-reaction process focused on the magnetic polarity inversion line region and/or the overall temporal relationship. Here we present high-resolution H-alpha off-band images and near-infrared vector magnetograms of a major flare observed with the 1.6 m Goode Solar Telescope (GST), which allow us to probe the relationship between motions of flare ribbons and variations of the underlying field. It is found that changes of photospheric fields occur instantly in a largely step-wise fashion at the arrival of the flare ribbon front, thus exhibit a propagation analogous to flare ribbons. In general, the fields become more inclined to the surface, with enhanced horizontal field and magnetic shear. When ribbons sweep through regions that undergo an apparent rotational motion, the fields transiently turn more vertical with decreased horizontal field and inclination angel, and then become more horizontal. Interestingly, the ribbon decelerates as approaching the sunspot rotation center, where the vertical field becomes persistently enhanced. Overall, NLFFF extrapolation models based on HMI vector field data suggest an inward collapse of magnetic fields. These results indicate that photospheric fields may respond instantaneously and differentially to the coronal field restructuring due to reconnection of individual flux bundles. Title: Observation of Light Bridge Brightening and Plasma Ejection Triggered by a Magnetic Flux Emergence Event Authors: Yang, Xu; Yurchyshyn, Vasyl; Ahn, Kwangsu; Cao, Wenda Bibcode: 2018tess.conf10906Y Altcode: Light bridges (LBs) are elongated, bright, granular structures that divide the umbra of a large and complex sunspot into two or more umbral regions with the same magnetic polarity. Surge-like activities are common phenomenon appear above the LBs which always accompanied by the magnetic flux emergence process. Former works tried to interpret the triggering mechanism for them, however they often lacked the support of high spatial and temporal resolution vector magnetic measurement. Our recent Observation shows a strong magnetic flux emergence happened at the edge of a filamentary Light Bridge (LB) and accompanied by brightness enhancement of photospheric granulations at the endpoints of the emerged magnetic structure. We study the origin and dynamics of this magnetic flux emergence event with high resolution Fe I 1.56 μm polarimetry magnetogram, TiO photosphere image and Hα chromosphere image from the Goode Solar Telescope. The emerged magnetic structure was 1.5 Mm × 0.3 Mm in size at its peak time and lasted for 17 minutes. Doppler map detected upflows before its formation and downflows during the destruction. The magnetic orientation change was obtained by calculating the shear angle and plotting the magnetic field vectors. The result indicates that the new emerged more transverse magnetic field reconnected with the pre-existing more vertical field, which triggered the fan-shaped jets. The expanding fields at the endpoints due to the flux emergence pushed and compressed the existing granulations and led to their enhanced brightness. Title: Study of 3D magnetic Structure Corresponding to Extremely Strong Photospheric Magnetic Fields in Active Region 12673 Authors: Wang, Haimin; Yurchyshyn, Vasyl; Liu, Chang; Chen, Bin; Jing, Ju; Ahn, Kwangsu; Toriumi, Shin; Cao, Wenda Bibcode: 2018tess.conf31902W Altcode: Solar Active Region (AR) 12673 is the most flare productive AR in the solar cycle 24. It produced four X-class flares including the X9.3 flare on 06 September 2017 and the X8.2 limb event on 10 September. Sun and Norton (2017) reported that this region had an unusual high rate of flux emergence, while Huang et al. (2018) reported that the X9.3 flare had extremely strong white-light flare emission. Yang et al. (2017) described the detailed morphological evolution of this AR. In this work, we first study the unusual behaviors of the light bridge (LB) dividing the delta configuration of this AR, namely the strong magnetic fields (above 5500 G) in the LB and the apparent photospheric twist as seen in observations with a 0.1 arcsec spatial resolution obtained by the 1.6m Goode Solar Telescope (GST) at the Big Bear Solar Observatory. Using the newly commissioned Expanded Owens Valley Solar Array (EOVSA), we carried out diagnoses of magnetic fields in this AR with microwave imaging spectroscopy from 2.5 to 18 GHz. Finally, we utilized Non-Linear Force Free Field (NLFFF) extrapolation to reveal 3-D magnetic structure to gain a physical understanding of GST and EOVSA observations of this AR. Title: Milne-Eddington Stokes Inversion of the NIRIS Magnetogram Data Achieved by Machine Learning Technique Authors: Ahn, Kwangsu; Cao, Wenda Bibcode: 2018tess.conf30818A Altcode: The Near InfraRed Imaging Spectrograph (NIRIS) at the Goode Solar Telescope produces Stokes I, Q, U, and V polarimetric profiles at a spectral resolution of 0.01 nm in 1564.8 nm band, with a typical range of -0.25 to +0.25 nm from the line center. This narrow band is achieved with a combination of a pre-filter and dual Fabry-Perot (F-P) etalon system. Typical line scan takes about 30 seconds. We use Milne-Eddington (ME) inversion technique to deduce physical parameters of an image pixel - such as total magnetic field strength, vertical/horizontal component of the magnetic field, Doppler shift of the line center and so on. However, due to many noise factors such inversion attempts are not always reasonable, especially when the profiles are complicated. Most of the ME fitting errors come from the initial guess of the longitudinal field strenghth calcuated from the center-of-gravity method.

We present our result of a new approach of inversion by using machine learning technique. Sagemaker, a new platform from Amazon Web Services, was adopted for training and modeling of the line profiles. We used principal component analysis (PCA) algorithm to deduce several physical parameters out of a trained model. This method not only reduces the dimension of the data but also enhances the speed of data processing. The result indicates that our model well fits into the actual measured line profiles as well as saving processing time. We present comparison of our new method to the ME inversion method in terms of accuracy and processing time. Title: The Formation of a Sunspot Penumbra Sector in Active Region NOAA 12574 Authors: Li, Qiaoling; Yan, Xiaoli; Wang, Jincheng; Kong, DeFang; Xue, Zhike; Yang, Liheng; Cao, Wenda Bibcode: 2018ApJ...857...21L Altcode: We present a particular case of the formation of a penumbra sector around a developing sunspot in the active region NOAA 12574 on 2016 August 11 by using the high-resolution data observed by the New Solar Telescope at the Big Bear Solar Observatory and the data acquired by the Helioseismic and Magnetic Imager and the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory satellite. Before the new penumbra sector formed, the developing sunspot already had two umbrae with some penumbral filaments. The penumbra sector gradually formed at the junction of two umbrae. We found that the formation of the penumbra sector can be divided into two stages. First, during the initial stage of penumbral formation, the region where the penumbra sector formed always appeared blueshifted in a Dopplergram. The area, mean transverse magnetic field strength, and total magnetic flux of the umbra and penumbra sector all increased with time. The initial penumbral formation was associated with magnetic emergence. Second, when the penumbra sector appeared, the magnetic flux and area of the penumbra sector increased after the umbra’s magnetic flux and area decreased. These results indicate that the umbra provided magnetic flux for penumbral development after the penumbra sector appeared. We also found that the newly formed penumbra sector was associated with sunspot rotation. Based on these findings, we suggest that the penumbra sector was the result of the emerging flux that was trapped in the photosphere at the initial stage of penumbral formation, and when the rudimentary penumbra formed, the penumbra sector developed at the cost of the umbra. Title: High-resolution Observations of Flares in an Arch Filament System Authors: Su, Yingna; Liu, Rui; Li, Shangwei; Cao, Wenda; Ahn, Kwangsu; Ji, Haisheng Bibcode: 2018ApJ...855...77S Altcode: 2018arXiv180306085S We study five sequential solar flares (SOL2015-08-07) occurring in Active Region 12396 observed with the Goode Solar Telescope (GST) at the Big Bear Solar Observatory, complemented by Interface Region Imaging Spectrograph and SDO observations. The main flaring region is an arch filament system (AFS) consisting of multiple bundles of dark filament threads enclosed by semicircular flare ribbons. We study the magnetic configuration and evolution of the active region by constructing coronal magnetic field models based on SDO/HMI magnetograms using two independent methods, i.e., the nonlinear force-free field (NLFFF) extrapolation and the flux rope insertion method. The models consist of multiple flux ropes with mixed signs of helicity, i.e., positive (negative) in the northern (southern) region, which is consistent with the GST observations of multiple filament bundles. The footprints of quasi-separatrix layers (QSLs) derived from the extrapolated NLFFF compare favorably with the observed flare ribbons. An interesting double-ribbon fine structure located at the east border of the AFS is consistent with the fine structure of the QSL’s footprint. Moreover, magnetic field lines traced along the semicircular footprint of a dome-like QSL surrounding the AFS are connected to the regions of significant helicity and Poynting flux injection. The maps of magnetic twist show that positive twist became dominant as time progressed, which is consistent with the injection of positive helicity before the flares. We hence conclude that these circular shaped flares are caused by 3D magnetic reconnection at the QSLs associated with the AFS possessing mixed signs of helicity. Title: Frequently Occurring Reconnection Jets from Sunspot Light Bridges Authors: Tian, Hui; Yurchyshyn, Vasyl; Peter, Hardi; Solanki, Sami K.; Young, Peter R.; Ni, Lei; Cao, Wenda; Ji, Kaifan; Zhu, Yingjie; Zhang, Jingwen; Samanta, Tanmoy; Song, Yongliang; He, Jiansen; Wang, Linghua; Chen, Yajie Bibcode: 2018ApJ...854...92T Altcode: 2018arXiv180106802T Solid evidence of magnetic reconnection is rarely reported within sunspots, the darkest regions with the strongest magnetic fields and lowest temperatures in the solar atmosphere. Using the world’s largest solar telescope, the 1.6 m Goode Solar Telescope, we detect prevalent reconnection through frequently occurring fine-scale jets in the Hα line wings at light bridges, the bright lanes that may divide the dark sunspot core into multiple parts. Many jets have an inverted Y-shape, shown by models to be typical of reconnection in a unipolar field environment. Simultaneous spectral imaging data from the Interface Region Imaging Spectrograph show that the reconnection drives bidirectional flows up to 200 km s-1, and that the weakly ionized plasma is heated by at least an order of magnitude up to ∼80,000 K. Such highly dynamic reconnection jets and efficient heating should be properly accounted for in future modeling efforts of sunspots. Our observations also reveal that the surge-like activity previously reported above light bridges in some chromospheric passbands such as the Hα core has two components: the ever-present short surges likely to be related to the upward leakage of magnetoacoustic waves from the photosphere, and the occasionally occurring long and fast surges that are obviously caused by the intermittent reconnection jets. Title: Extending Counter-streaming Motion from an Active Region Filament to a Sunspot Light Bridge Authors: Wang, Haimin; Liu, Rui; Li, Qin; Liu, Chang; Deng, Na; Xu, Yan; Jing, Ju; Wang, Yuming; Cao, Wenda Bibcode: 2018ApJ...852L..18W Altcode: 2017arXiv171206783W We analyze high-resolution observations from the 1.6 m telescope at Big Bear Solar Observatory that cover an active region filament. Counter-streaming motions are clearly observed in the filament. The northern end of the counter-streaming motions extends to a light bridge, forming a spectacular circulation pattern around a sunspot, with clockwise motion in the blue wing and counterclockwise motion in the red wing, as observed in the Hα off-bands. The apparent speed of the flow is around 10-60 km s-1 in the filament, decreasing to 5-20 km s-1 in the light bridge. The most intriguing results are the magnetic structure and the counter-streaming motions in the light bridge. Similar to those in the filament, the magnetic fields show a dominant transverse component in the light bridge. However, the filament is located between opposed magnetic polarities, while the light bridge is between strong fields of the same polarity. We analyze the power of oscillations with the image sequences of constructed Dopplergrams, and find that the filament’s counter-streaming motion is due to physical mass motion along fibrils, while the light bridge’s counter-streaming motion is due to oscillation in the direction along the line-of-sight. The oscillation power peaks around 4 minutes. However, the section of the light bridge next to the filament also contains a component of the extension of the filament in combination with the oscillation, indicating that some strands of the filament are extended to and rooted in that part of the light bridge. Title: Strong Transverse Photosphere Magnetic Fields and Twist in Light Bridge Dividing Delta Sunspot of Active Region 12673 Authors: Wang, Haimin; Yurchyshyn, Vasyl; Liu, Chang; Ahn, Kwangsu; Toriumi, Shin; Cao, Wenda Bibcode: 2018RNAAS...2....8W Altcode: 2018RNAAS...2a...8W; 2018arXiv180102928W Solar Active Region (AR) 12673 is the most flare productive AR in the solar cycle 24. It produced four X-class flares including the X9.3 flare on 06 September 2017 and the X8.2 limb event on 10 September. Sun and Norton (2017) reported that this region had an unusual high rate of flux emergence, while Huang et al. (2018) reported that the X9.3 flare had extremely strong white-light flare emissions. Yang at al. (2017) described the detailed morphological evolution of this AR. In this report, we focus on usual behaviors of the light bridge (LB) dividing the delta configuration of this AR, namely the strong magnetic fields (above 5500 G) in the LB and apparent photospheric twist as shown in observations with a 0.1 arcsec spatial resolution obtained by the 1.6m telescope at Big Bear Solar Observatory. Title: Transient rotation of photospheric vector magnetic fields associated with a solar flare Authors: Xu, Yan; Cao, Wenda; Ahn, Kwangsu; Jing, Ju; Liu, Chang; Chae, Jongchul; Huang, Nengyi; Deng, Na; Gary, Dale E.; Wang, Haimin Bibcode: 2018NatCo...9...46X Altcode: 2018arXiv180103171X As one of the most violent eruptions on the Sun, flares are believed to be powered by magnetic reconnection. The fundamental physics involving the release, transfer, and deposition of energy have been studied extensively. Taking advantage of the unprecedented resolution provided by the 1.6 m Goode Solar Telescope, here, we show a sudden rotation of vector magnetic fields, about 12-20° counterclockwise, associated with a flare. Unlike the permanent changes reported previously, the azimuth-angle change is transient and cospatial/temporal with Hα emission. The measured azimuth angle becomes closer to that in potential fields suggesting untwist of flare loops. The magnetograms were obtained in the near infrared at 1.56 μm, which is minimally affected by flare emission and no intensity profile change was detected. We believe that these transient changes are real and discuss the possible explanations in which the high-energy electron beams or Alfve'n waves play a crucial role. Title: 1.56 Micron Spectropolarimetry of Umbral Dots and Their Evolution Associated with a Major Flare Authors: Deng, Na; Liu, Chang; Xu, Yan; Ahn, Kwangsu; Jing, Ju; Cao, Wenda; Wang, Haimin Bibcode: 2017SPD....4830003D Altcode: We present unprecedented high-resolution and high magnetic sensitivity spectropolarimetric characterization of umbral dots (UDs), the prevailing fine scale brightness structure manifesting magneto-convection inside sunspot umbrae where the magnetic fields are strongest and nearly vertical. This is made available by recent development of the Near InfraRed Imaging Spectropolarimeter (NIRIS) using the 1.56 micron FeI line at the 1.6 meter New Solar Telescope of Big Bear Solar Observatory. Vector magnetograms are obtained after Milne-Eddington Stokes inversions, 180-degree azimuthal ambiguity resolution, and correction of projection effects. A βγδ spot in NOAA AR 12371 was observed for six hours on June 22, 2015 with a cadence of 87 s, which covered an M6.6 flare. The overall umbra is separated into several smaller umbrae by light bridges. The umbrae are close to the flaring polarity inversion line and show an average inclination of about 17° and field strength of about 2100 Gauss. The UDs are resolvable in NIRIS vector magnetograms, especially for peripheral UDs. The measured field strength is about 3% lower in UDs comparing to umbral cores (UCs) where the continuum intensity is below the threshold of UDs. The field is more inclined in UDs by 5% ( ≈ 1°) than that in UCs. One of the umbrae showed rapid evolution associated with the flare. Its overall intensity and the number of UDs decrease by at least 7% within two hours after being swept by the flare ribbon. NIRIS vector magnetograms indicate that the average field strength of that umbra has a rapid stepwise increase for about 100 Gauss while the inclination almost has no change. The decreases of the umbral brightness and the number of UDs are thus attributed to the increase of the field strength. The results suggest that the field strength plays the most important role in constraining convective heat transport in umbra. Title: High-resolution Observations of Photospheric Structural Evolution Associated with a Flare Authors: Liu, Chang; Xu, Yan; Ahn, Kwangsu; Jing, Ju; Deng, Na; Cao, Wenda; Wang, Haimin Bibcode: 2017SPD....4810101L Altcode: The structural evolution of the photosphere not only play an important role in contributing to the accumulation of free energy in the corona that powers solar flares, but also may response to the restructuring of coronal field as a result of flare energy release. A better understanding of these issues may be achieved by high-resolution observations of the photospheric structure covering the entire flaring period, which are, however, still rare. Here we present photospheric vector magnetograms and TiO images (at 0.2" and 0.09" resolution, respectively) from before to after a major flare, taken by the 1.6 m New Solar Telescope at Big Bear Solar Observatory. In the pre-flare state, a small-scale magnetic structure of opposite-polarity configuration is seen near the footpoints of sheared magnetic loops; its magnetic fluxes and currents enhance till the flare start time and decline afterwards. During the main phase, as one flare ribbon sweeps across a sunspot, its different portions accelerate at different times corresponding to peaks of flare hard X-ray emission. We suggest that the small-scale flux emergence between the two sheared flux systems triggers the flare reconnection, and that the sunspot rotation is driven by the surface Lorentz-force change due to the coronal back reaction. Title: Magnetic vector rotation in response to the energetic electron beam during a flare Authors: Xu, Yan; Cao, Wenda; Kwangsu, Ahn; Jing, Ju; Liu, Chang; Chae, Jongchul; Huang, Nengyi; Deng, Na; Gary, Dale E.; Wang, Haimin Bibcode: 2017SPD....4810001X Altcode: As one of the most violent forms of eruption on the Sun, flares are believed to be powered by magnetic reconnection, by which stored magnetic energy is released. The fundamental physical processes involving the release, transfer and deposition of energy in multiple layers of the solar atmosphere have been studied extensively with significant progress. Taking advantage of recent developments in observing facilities, new phenomena are continually revealed, bringing new understanding of solar flares. Here we report the discovery of a transient rotation of vector magnetic fields associated with a flare observed by the 1.6-m New Solar Telescope at Big Bear Solar Observatory. After ruling out the possibility that the rotation is caused by line profile changes due to flare heating, our observation shows that the transverse field rotateded by about 12-20 degrees counterclockwise, and returned quickly to previous values after the flare ribbons swept through. More importantly, as a consequence of the rotation, the flare loops untwisted and became more potential. The vector magnetograms were obtained in the near infrared at 1560 nm, which is minimally affected by flare emission and no intensity profile change was detected. Therefore, we believe that these transient changes are real, and conclude the high energy electron beams play an crucial role in the field changes. A straightforward and instructive explanation is that the induced magnetic field of the electron beam superimposed on the pre-flare field leads to a transient rotation of the overall field. Title: The Eruption of a Small-scale Emerging Flux Rope as the Driver of an M-class Flare and of a Coronal Mass Ejection Authors: Yan, X. L.; Jiang, C. W.; Xue, Z. K.; Wang, J. C.; Priest, E. R.; Yang, L. H.; Kong, D. F.; Cao, W. D.; Ji, H. S. Bibcode: 2017ApJ...845...18Y Altcode: 2017arXiv170700073Y Solar flares and coronal mass ejections are the most powerful explosions in the Sun. They are major sources of potentially destructive space weather conditions. However, the possible causes of their initiation remain controversial. Using high-resolution data observed by the New Solar Telescope of Big Bear Solar Observaotry, supplemented by Solar Dynamics Observatory observations, we present unusual observations of a small-scale emerging flux rope near a large sunspot, whose eruption produced an M-class flare and a coronal mass ejection. The presence of the small-scale flux rope was indicated by static nonlinear force-free field extrapolation as well as data-driven magnetohydrodynamics modeling of the dynamic evolution of the coronal three-dimensional magnetic field. During the emergence of the flux rope, rotation of satellite sunspots at the footpoints of the flux rope was observed. Meanwhile, the Lorentz force, magnetic energy, vertical current, and transverse fields were increasing during this phase. The free energy from the magnetic flux emergence and twisting magnetic fields is sufficient to power the M-class flare. These observations present, for the first time, the complete process, from the emergence of the small-scale flux rope, to the production of solar eruptions. Title: Data processing pipeline of the Near-Infrared Imaging Spectropolarimeter at the NST Authors: Ahn, Kwangsu; Cao, Wenda Bibcode: 2017SPD....4811504A Altcode: The Near-Infrared Imaging Spectropolarimeter (NIRIS) is made for imaging magnetic field structures on the Sun. The data acquired undergoes extensive post-processing to ensure high resolution, high signal to noise ratio, and high accuracy. We would like to introduce how the data are processed by demonstrating data processing pipeline. In this manner, the capabilities and the limits in data analysis would be evaluated. The NIRIS is dedicated to Fe I 15648 band observation for now, while it has potential for expanding their choice of bands as well as improving data quality. Such upgrade plans should be discussed and prioritized. Title: Extending Counter-Streaming Motion from an Active Region Filament to Sunspot Light Bridge Authors: Wang, Haimin; Liu, Rui; Deng, Na; Liu, Chang; Xu, Yan; Jing, Ju; Wang, Yuming; Cao, Wenda Bibcode: 2017SPD....4810405W Altcode: In this study, we analyze the high-resolution observations from the 1.6 m New Solar Telescope at Big Bear Solar Observatory that cover an entire active region filament. The southern end of the filament is well defined by a narrow lane situated in the negative magnetic polarity, while the northern end lies in the positive polarity, extending to a much larger area. Counter-streaming motions are clearly seen in the filament. The northern end of the counter-streaming motions extends to a light bridge, forming a spectacular circulation pattern around a sunspot, with clockwise motion in the blue wing and counterclockwise motion in the red wing as observed in H-alpha off-band. The apparent speed of the flow is around 10 km/s. We show that the southern end of the filament is consistent with that of a flux rope in a NLFFF extrapolation model, but the northern ends of the modeled flux rope and observed H-alpha footpoints have a significant spatial mismatch. The most intriguing results are the magnetic structure and the counter-streaming motions in the light bridge. Similar to those in the filament, magnetic fields show a dominant transverse component in the light bridge. However, the filament is located between opposite magnetic polarities, while the light bridge is between strong fields of the same polarity. We studied the correlation coefficients of image sequences of constructed Dopplergrams, and found that the filament and the section of light bridge next to it do not show oscillation motions, while a small section of light bridge shows a prominent oscillation pattern. Therefore, we conclude that the observed circulating counter-streaming motions are largely collections of physical mass flows in the transverse direction from the filament extending to a large section of the light bridge, rather than a form of periodic oscillatory mass motions in line-of-sight direction generated by perturbations omnipresent in the chromosphere. Title: High-Resolution Observations of Flares in an Arch Filament System Authors: Su, Yingna; Liu, Rui; Li, Shangwei; Cao, Wenda; Ji, Haisheng Bibcode: 2017SPD....4840604S Altcode: We present high-resolution observations of five sequential solar flares occurring in NOAA Active Region (AR) 12396 taken with the 1.6-m New Solar Telescope at the Big Bear Solar Observatory, complemented by IRIS and SDO observations. The main flaring region is an arch filament system (AFS) consisting of multiple bundles of dark filament threads enclosed by scattered flare brightenings. We study the magnetic configuration and evolution of the active region by constructing coronal magnetic field models based on SDO/HMI magnetograms using two independent methods, i.e., the nonlinear force-free field (NLFFF) extrapolation and the flux rope insertion method. We are able to identify multiple flux ropes based on magnetic twist derived from the extrapolated NLFFF, which is consistent with the NST observations of multiple filaments. Both models suggest that the filament bundles may posses mixed signs of helicity, i.e., positive (negative) in the north (south). The footprints of quasi-separatrix layers (QSLs) derived from the extrapolated NLFFF compare favorably with the observed flare ribbons. Moreover, magnetic field lines traced along the semi-circular footprint of a dome-like QSL surrounding the flaring region are connected to the regions of significant helicity and Poynting flux injection. An interesting double-ribbon fine structure located at the east border of the AFS is consistent with the fine structure of the QSL's footprint. The maps of magnetic twist show that positive twist became dominant as time progressed, which is consistent with the injection of positive helicity during a 26 hour interval before the flares. The trigger mechanisms and detailed dynamics of the observed flares are also discussed. Title: Multi-wavelength Spectral Analysis of Ellerman Bombs Observed by FISS and IRIS Authors: Hong, Jie; Ding, M. D.; Cao, Wenda Bibcode: 2017ApJ...838..101H Altcode: 2017arXiv170304268H Ellerman bombs (EBs) are a kind of solar activity that is suggested to occur in the lower solar atmosphere. Recent observations using the Interface Region Imaging Spectrograph (IRIS) show connections between EBs and IRIS bombs (IBs), which imply that EBs might be heated to a much higher temperature (8 × 104 K) than previous results. Here we perform a spectral analysis of EBs simultaneously observed by the Fast Imaging Solar Spectrograph and IRIS. The observational results show clear evidence of heating in the lower atmosphere, indicated by the wing enhancement in Hα, Ca II 8542 Å, and Mg II triplet lines and also by brightenings in images of the 1700 Å and 2832 Å ultraviolet continuum channels. Additionally, the intensity of the Mg II triplet line is correlated with that of Hα when an EB occurs, suggesting the possibility of using the triplet as an alternative way to identify EBs. However, we do not find any signal in IRIS hotter lines (C II and Si IV). For further analysis, we employ a two-cloud model to fit the two chromospheric lines (Hα and Ca II 8542 Å) simultaneously, and obtain a temperature enhancement of 2300 K for a strong EB. This temperature is among the highest of previous modeling results, albeit still insufficient to produce IB signatures at ultraviolet wavelengths. Title: High-resolution observations of flare precursors in the low solar atmosphere Authors: Wang, Haimin; Liu, Chang; Ahn, Kwangsu; Xu, Yan; Jing, Ju; Deng, Na; Huang, Nengyi; Liu, Rui; Kusano, Kanya; Fleishman, Gregory D.; Gary, Dale E.; Cao, Wenda Bibcode: 2017NatAs...1E..85W Altcode: 2017arXiv170309866W Solar flares are generally believed to be powered by free magnetic energy stored in the corona1, but the build up of coronal energy alone may be insufficient to trigger the flare to occur2. The flare onset mechanism is a critical but poorly understood problem, insights into which could be gained from small-scale energy releases known as precursors. These precursors are observed as small pre-flare brightenings in various wavelengths3-13 and also from certain small-scale magnetic configurations such as opposite-polarity fluxes14-16, where the magnetic orientation of small bipoles is opposite to that of the ambient main polarities. However, high-resolution observations of flare precursors together with the associated photospheric magnetic field dynamics are lacking. Here we study precursors of a flare using the unprecedented spatiotemporal resolution of the 1.6-m New Solar Telescope, complemented by new microwave data. Two episodes of precursor brightenings are initiated at a small-scale magnetic channel17-20 (a form of opposite-polarity flux) with multiple polarity inversions and enhanced magnetic fluxes and currents, lying near the footpoints of sheared magnetic loops. Microwave spectra corroborate that these precursor emissions originate in the atmosphere. These results provide evidence of low-atmospheric small-scale energy release, possibly linked to the onset of the main flare. Title: Magnetic Separatrix as the Source Region of the Plasma Supply for an Active-region Filament Authors: Zou, P.; Fang, C.; Chen, P. F.; Yang, K.; Cao, Wenda Bibcode: 2017ApJ...836..122Z Altcode: 2017arXiv170101526Z Solar filaments can be formed via chromospheric evaporation followed by condensation in the corona or by the direct injection of cool plasma from the chromosphere to the corona. We here confirm with high-resolution Hα data observed by the 1.6 m New Solar Telescope of the Big Bear Solar Observatory on 2015 August 21 that an active-region filament is maintained by the continuous injection of cold chromospheric plasma. We find that the filament is rooted along a bright ridge in Hα, which corresponds to the intersection of a magnetic quasi-separatrix layer with the solar surface. This bright ridge consists of many small patches whose sizes are comparable to the width of the filament threads. It is found that upflows originate from the brighter patches of the ridge, whereas the downflows move toward the weaker patches of the ridge. The whole filament is composed of two opposite-direction streams, implying that longitudinal oscillations are not the only cause of the counterstreamings, and unidirectional siphon flows with alternative directions are another possibility. Title: A novel 3-D calorimeter for the High Energy cosmic-Radiation Detection (HERD) Facility onboard China's Future Space Station Authors: Dong, Y.; HERD Collaboration; Xu, M.; Wang, Z.; Adriani, O.; Albergo, S.; Ambrosi, G.; Azzarello, P.; Bai, Y.; Bao, T.; Bernardini, P.; Bertucci, B.; Bi, X.; Bongi, M.; Bottai, S.; Cao, W.; Chai, J.; Chen, Z.; D'Alessandro, R.; Santo, M. D.; Duranti, M.; Fang, K.; Feng, H.; Formato, V.; Fusco, P.; Gao, J.; Gargano, F.; Giglietto, N.; Hu, P.; Li, R.; Li, Y.; Lin, S.; Liu, H.; Liu, X.; Loparco, F.; Lyu, J.; Marsella, G.; Mazziottai, M. N.; Mitri, I. D.; Mori, N.; Papini, P.; Peng, W.; Pohl, M.; Quan, Z.; Shi, D.; Sun, X.; Surdo, A.; Vannuccini, E.; Walter, R.; Wang, B.; Wang, B.; Wang, J.; Wang, L.; Wang, R.; Wu, B.; Wu, Q.; Wu, X.; Zhang, L.; Zhang, S. N. Bibcode: 2017ICRC...35..253D Altcode: 2017PoS...301..253D No abstract at ADS Title: Introduction to the High Energy cosmic-Radiation Detection (HERD) Facility onboard China's Future Space Station Authors: Zhang, S. N.; Adriani, O.; Consortium, H.; Albergo, S.; Ambrosi, G.; An, Q.; Azzarello, P.; Bai, Y.; Bao, T.; Bernardini, P.; Bertucci, B.; Bi, X.; Bongi, M.; Bottai, S.; Cao, W.; Cao, Z.; Chai, J.; Chang, J.; Chen, G.; Chen, Y.; Chen, Z.; Cui, X. H.; Dai, Z. G.; D'Alessandro, R.; Santo, M. D.; Dong, Y.; Duranti, M.; Fan, Y.; Fang, K.; Feng, C. Q.; Feng, H.; Formato, V.; Fusco, P.; Gao, J.; Gargano, F.; Giglietto, N.; Gou, Q.; Guo, Y. Q.; He, H. H.; Hu, H.; Hu, P.; Huang, G. S.; Huang, J.; Huang, Y. F.; Li, H.; Li, R.; Li, Y.; Li, Z.; Liang, E. W.; Lin, S.; Liu, H.; Liu, H.; Liu, J. B.; Liu, S. B.; Liu, S. M.; Liu, X.; Loparco, F.; Lyu, J.; Marsella, G.; Mazziottai, M. N.; Mitri, I. D.; Mori, N.; Papini, P.; Pearce, M.; Peng, W.; Pohl, M.; Quan, Z.; Ryde, F.; Shi, D.; Su, M.; Sun, X. L.; Sun, X.; Surdo, A.; Tang, Z. C.; Vannuccini, E.; Walter, R.; Wang, B.; Wang, B.; Wang, J. C.; Wang, J. M.; Wang, J.; Wang, L.; Wang, R.; Wang, X. L.; Wang, X. Y.; Wang, Z.; Wei, D. M.; Wu, B.; Wu, J.; Wu, Q.; Wu, X.; Wu, X. F.; Xu, M.; Xu, Z. Z.; Yan, H. R.; Yin, P. F.; Yu, Y. W.; Yuan, Q.; Zha, M.; Zhang, L.; Zhang, L.; Yi, Z.; Zhang, Y. L.; Zhao, Z. G. Bibcode: 2017ICRC...35.1077Z Altcode: 2017PoS...301.1077Z No abstract at ADS Title: Objective Image Quality Assessment for High Resolution Photospheric Images by Median Filter Gradient Similarity Authors: Deng, Hui; Zhang, Dandan; Wang, Tianyu; Ji, Kaifan; Wang, Feng; Liu, Zhong; Xiang, Yongyuan; Jin, Zhenyu; Cao, Wenda Bibcode: 2017arXiv170105300D Altcode: All next generation ground-based and space-based solar telescopes require a good quality assessment metric in order to evaluate their imaging performance. In this paper, a new image quality metric, the median filter gradient similarity (MFGS) is proposed for photospheric images. MFGS is a no-reference/blind objective image quality metric (IQM) by a measurement result between 0 and 1 and has been performed on short-exposure photospheric images captured by the New Vacuum Solar Telescope (NVST) of the Fuxian Solar Observatory and by the Solar Optical Telescope (SOT) onboard the Hinode satellite, respectively. The results show that: (1)the measured value of MFGS changes monotonically from 1 to 0 with degradation of image quality; (2)there exists a linear correlation between the measured values of MFGS and root-mean-square-contrast (RMS-contrast) of granulation; (3)MFGS is less affected by the image contents than the granular RMS-contrast. Overall, MFGS is a good alternative for the quality assessment of photospheric images. Title: Unprecedented Fine Structures during a Solar Eruptive Event Observed by the 1.6-m New Solar Telescope at Big Bear Solar Observatory Authors: Xu, Y.; Jing, J.; Li, Q.; Cao, W.; Wang, H. Bibcode: 2016AGUFMSH41E..04X Altcode: A solar eruptive event includes both large-scale and small-scale structures. Flares, filament eruptions and CMEs are large-scale features and have been studied extensively in the literature. On the other hand, fine structures (below 500 km) are rarely observed and are accessible to only a fewinstruments world-wide. Using the 1.6-m New Solar Telescope (NST) at Big Bear Solar Observatory (BBSO), an M6.5 flare was captured on June 22, 2015. This extraordinary observation reveals the process of the magnetic energy release in unprecedented detail, including the flare ribbon propagating across the sunspots, sunspot rotation, magnetic channels (elongated structurescomprising alternating magnetic polarity inversion lines), coronal rain (made of condensing plasma) streaming down along the post-flare loops, and the chromosphere's response to the impact of coronal rain, showing fine-scale brightenings at the footpoints of the falling plasma. Here we present our analysis of this event in a comprehensive manner covering the above phenomena. Title: High Resolution He I 10830 AA Narrow-band Imaging of an M-class Flare. I - Analysis of Sunspot Dynamics during Flaring Authors: Wang, Ya; Su, Yingna; Hong, Zhenxiang; Zeng, Zhicheng; Ji, Kaifan; Goode, Philip R.; Cao, Wenda; Ji, Haisheng Bibcode: 2016ApJ...833..250W Altcode: In this paper, we report our first-step results of high resolution He I 10830 Å narrow-band imaging (bandpass: 0.5 Å) of an M1.8 class two-ribbon flare on 2012 July 5. The flare was observed with the 1.6 m aperture New Solar Telescope at Big Bear Solar Observatory. For this unique data set, sunspot dynamics during flaring were analyzed for the first time. By directly imaging the upper chromosphere, running penumbral waves are clearly seen as an outward extension of umbral flashes; both take the form of absorption in the 10830 Å narrow-band images. From a space-time image made of a slit cutting across a flare ribbon and the sunspot, we find that the dark lanes for umbral flashes and penumbral waves are obviously broadened after the flare. The most prominent feature is the sudden appearance of an oscillating absorption strip inside the ribbon when it sweeps into the sunspot’s penumbral and umbral regions. During each oscillation, outwardly propagating umbral flashes and subsequent penumbral waves rush out into the inwardly sweeping ribbon, followed by a return of the absorption strip with similar speed. We tentatively explain the phenomena as the result of a sudden increase in the density of ortho-helium atoms in the area of the sunspot being excited by the flare’s extreme ultraviolet illumination. This explanation is based on the observation that 10830 Å absorption around the sunspot area gets enhanced during the flare. Nevertheless, questions are still open and we need further well-devised observations to investigate the behavior of sunspot dynamics during flares. Title: Material Supply and Magnetic Configuration of an Active Region Filament Authors: Zou, P.; Fang, C.; Chen, P. F.; Yang, K.; Hao, Q.; Cao, Wenda Bibcode: 2016ApJ...831..123Z Altcode: 2017arXiv170102407Z It is important to study the fine structures of solar filaments with high-resolution observations, since it can help us understand the magnetic and thermal structures of the filaments and their dynamics. In this paper, we study a newly formed filament located inside the active region NOAA 11762, which was observed by the 1.6 m New Solar Telescope at Big Bear Solar Observatory from 16:40:19 UT to 17:07:58 UT on 2013 June 5. As revealed by the Hα filtergrams, cool material is seen to be injected into the filament spine with a speed of 5-10 km s-1. At the source of the injection, brightenings are identified in the chromosphere, which are accompanied by magnetic cancellation in the photosphere, implying the importance of magnetic reconnection in replenishing the filament with plasmas from the lower atmosphere. Counter-streamings are detected near one endpoint of the filament, with the plane-of-the-sky speed being 7-9 km s-1 in the Hα red-wing filtergrams and 9-25 km s-1 in the blue-wing filtergrams. The observations are indicative that this active region filament is supported by a sheared arcade without magnetic dips, and the counter-streamings are due to unidirectional flows with alternative directions, rather than due to the longitudinal oscillations of filament threads as in many other filaments. Title: Spectropolarimetry of Atomic and Molecular Lines near 4135 nm Authors: Penn, Matthew James; Uitenbroek, Han; Clark, Alan; Coulter, Roy; Goode, Phil; Cao, Wenda Bibcode: 2016SoPh..291.2243P Altcode: 2015arXiv151204451P; 2016SoPh..tmp..142P New spatially scanned spectropolarimetry sunspot observations are made of photospheric atomic and molecular absorption lines near 4135 nm. The relative splittings among several atomic lines are measured and shown to agree with values calculated with configuration interaction and intermediate coupling. Large splitting is seen in a line identified with Fe I at 4137 nm, showing multiple Stokes V components and an unusual linear polarization. This line will be a sensitive probe of quiet-Sun magnetic fields, with a magnetic sensitivity of 2.5 times higher than that of the well-known 1565 nm Fe I line. Title: High resolution He I 10830 angstrom narrow-band imaging of an M-class flare.I-analysis of sunspot dynamics during flaring Authors: Wang, Ya; Su, Yingna; Hong, Zhenxiang; Zeng, Zhicheng; Ji, Kaifan; Goode, Philip R.; Cao, Wenda; Ji, Haisheng Bibcode: 2016usc..confE..38W Altcode: 2016arXiv161009227W We report our first-step results of high resolution He I 1083 nm narrow-band imaging of an M 1.8 class two-ribbon flare on July 5,2012. The flare was observed with the 1.6 meter aperture New Solar Telescope at Big Bear Solar Observatory. For this unique data set, sunspot dynamics during flaring were analyzed for the first time. By directly imaging the upper chromosphere, running penumbral waves are clearly seen as an outward extention of umbral flashes, both take the form of absorption in our 1083 nm narrow-band images. From a space-time image made of a slit cutting across the ribbon and the sunspot, we find that dark lanes for umbral flashes and penumbral waves are obviously broadened after the flare. The most prominent feature is the sudden appearance of an oscillating absorption strip inside one ribbon of the flare when it sweeps into sunspot's penumbral and umbral regions. During each oscillation, outwardly propagating umbral flashes and subsequent penumbral waves rush out into the inwardly sweeping ribbon, followed by a returning of the absorption strip with similar speed. We tentatively explain the phenomenon as the result of a sudden increase in the density of ortho-Helium atoms in the area of the sunspot area being excited by the flare's EUV illumination. This explanation is based on the obsevation that 1083 nm absorption in the sunspot area gets enhanced during the flare. Nevertheless, questions are still open and we need further well-devised observations to investigate the behavior of sunspot dynamics during flares. Title: Flare differentially rotates sunspot on Sun's surface Authors: Liu, Chang; Xu, Yan; Cao, Wenda; Deng, Na; Lee, Jeongwoo; Hudson, Hugh S.; Gary, Dale E.; Wang, Jiasheng; Jing, Ju; Wang, Haimin Bibcode: 2016NatCo...713104L Altcode: 2016arXiv161002969L Sunspots are concentrations of magnetic field visible on the solar surface (photosphere). It was considered implausible that solar flares, as resulted from magnetic reconnection in the tenuous corona, would cause a direct perturbation of the dense photosphere involving bulk motion. Here we report the sudden flare-induced rotation of a sunspot using the unprecedented spatiotemporal resolution of the 1.6 m New Solar Telescope, supplemented by magnetic data from the Solar Dynamics Observatory. It is clearly observed that the rotation is non-uniform over the sunspot: as the flare ribbon sweeps across, its different portions accelerate (up to ~50° h-1) at different times corresponding to peaks of flare hard X-ray emission. The rotation may be driven by the surface Lorentz-force change due to the back reaction of coronal magnetic restructuring and is accompanied by a downward Poynting flux. These results have direct consequences for our understanding of energy and momentum transportation in the flare-related phenomena. Title: High-resolution Observations of a Large Fan-shaped Surge Authors: Li, Zhen; Fang, Cheng; Guo, Yang; Chen, P. F.; Zou, Peng; Cao, Wenda Bibcode: 2016ApJ...826..217L Altcode: We present high-resolution observations of a large fan-shaped surge, which was observed on 2013 June 5 with the current largest solar telescope, the 1.6 m New Solar Telescope (NST), at the Big Bear Solar Observatory. The observations are made at TiO, Hα, and 10830 Å wavebands with a spatial resolution better than 0\buildrel{\prime\prime}\over{.} 1 and a full-run cadence of ∼30 s. The fan-shaped surge consists of many small-scale threads with a typical width of 100 km and a length of up to 200 Mm at the maximum. The threads come from material ejections, which start with a velocity of several km s-1, and then accelerate up to 60-80 km s-1 over six to seven minutes with an acceleration of up to 0.2-0.3 km s-2. The threads can be observed in the Hα band and in SDO/AIA 171 Å images as absorbed objects, implying that they are cool material ejections. The surge is ejected along open magnetic field lines in the extrapolated non-linear force-free field, which might actually be a part of a large-scale magnetic loop stretching back to the solar surface. After 10-20 minutes, the ejections gradually decay and the surge eventually vanishes. The total lifetime is about 35 minutes. The Hα brightening at the root of the fan-shaped surge implies that there is heating in the chromosphere, which could be produced by low-atmosphere interchange magnetic reconnection. Our observation provides evidence of the reconnection model for the fan-shaped surges, which was proposed by Jiang et al. Title: Data Processing of the magnetograms for the Near InfraRed Imaging Spectropolarimeter at Big Bear Solar Observatory Authors: Ahn, Kwangsu; Cao, Wenda; Shumko, Sergiy; Chae, Jongchul Bibcode: 2016SPD....47.0207A Altcode: We want to present the processing result of the vector magnetograms from the Near InfraRed Imaging Spectropolarimeter (NIRIS) at Big Bear Solar Observatory. The NIRIS is a successor of an old magnetograph system at BBSO, which equips with the new infrared detector and the improved Fabry-Perot filter system. While there are several upgrades to the new hardware, there are also some challenges as the data acquisition rate increases and we deal with the a larger detector array. The overall process includes dark and flat correction, image alignment, de-stretch, Stokes parameter selection, calibration of instrumental crosstalk, and Milne-Eddington inversion. Title: Ultra-Narrow Negative Flare Front Observed in Helium-10830 Å Using the1.6m New Solar Telescope Authors: Xu, Yan; Cao, Wenda; Ding, Mingde; Kleint, Lucia; Su, Jiangtao; Liu, Chang; Ji, Haisheng; Chae, Jongchul; Jing, Ju; Cho, Kyuhyoun; Cho, Kyung-Suk; Gary, Dale E.; Wang, Haimin Bibcode: 2016SPD....47.0633X Altcode: Solar flares are sudden flashes of brightness on the Sun and are often associated with coronal mass ejections and solar energetic particles that have adverse effects on the near-Earth environment. By definition, flares are usually referred to as bright features resulting from excess emission. Using the newly commissioned 1.6-m New Solar Telescope at Big Bear Solar Observatory, we show a striking “negative” flare with a narrow but unambiguous “dark” moving front observed in He I 10830 Å, which is as narrow as 340 km and is associated with distinct spectral characteristics in Hα and Mg II lines. Theoretically, such negative contrast in He I 10830 Å can be produced under special circumstances by nonthermal electron collisions or photoionization followed by recombination. Our discovery, made possible due to unprecedented spatial resolution, confirms the presence of the required plasma conditions and provides unique information in understanding the energy release and radiative transfer in solar flares. Title: BBSO/NST Observations of the Sudden Differential Rotation of a Sunspot Caused by a Major Flare Authors: Liu, Chang; Xu, Yan; Deng, Na; Cao, Wenda; Lee, Jeongwoo; Hudson, Hugh S.; Gary, Dale E.; Wang, Jiasheng; Jing, Ju; Wang, Haimin Bibcode: 2016SPD....47.0615L Altcode: Sunspots are concentrations of magnetic field visible on the solar surface (photosphere), from which the field extends high into the corona. Complex plasma motions that drag field in the photosphere can build up free energy in the corona that powers solar eruptions. It is known that solar flares and the often associated coronal ejections (CMEs) can produce various radiations in the low atmosphere. However, it was considered implausible that disturbances created in the tenuous corona would cause a direct perturbation of the dense photosphere involving bulk motion. Here we report the sudden rotational motion of a sunspot clearly induced by a major solar flare (SOL2015-06-22T18:23 M6.6), using the unprecedented spatiotemporal resolution of the 1.6 m New Solar Telescope (NST) at Big Bear Solar Observatory (BBSO). It is particularly striking that the rotation is not uniform over the sunspot: as the flare ribbon sweeps across, its different portions accelerate (up to ~50 degree per hour) at different times corresponding to peaks of flare hard X-ray emission. The intensity and magnetic field of the sunspot also change significantly associated with the flare. Our results reveal an intrinsic relationship between the photospheric plasma bulk motions and coronal energy release, with direct consequences for our understanding of energy and momentum balance in the flare/CME phenomenon. This work is mainly supported by NASA grants NNX13AF76G and NNX13AG13G (LWS), and NNX16AF72G, and NSF grants AGS 1250818 and 1408703. Title: Multi-wavelength Observations of a Subarcsecond Penumbral Transient Brightening Event Authors: Bai, X. Y.; Su, J. T.; Cao, W. D.; Liu, S. Q.; Deng, Y. Y.; Priya, T. G. Bibcode: 2016ApJ...823...60B Altcode: We report a subarcsecond penumbral transient brightening event with the high-spatial resolution observations from the 1.6 m New Solar Telescope (NST), Interface Region Imaging Spectrograph (IRIS), and the Solar Dynamics Observatory. The transient brightening, whose thermal energy is in the range of nanoflares, has signatures in the chromosphere, the transient region, and the corona. NST's Hα channel reveals the fine structure of the event with a width as narrow as 101 km (0.″14), which is much smaller than the width from the previous observation. The transient brightening lasts for about 3 minutes. It is associated with a redshift of about 17 km s-1, found in the Si IV 1402.77 Å line and exhibits an inward motion to the umbra with a speed of 87 km s-1. The small-scale energy released from the event has a multi-temperature component. Spectral analysis of the brightening region from IRIS shows that not only the transition region lines such as Si IV 1402.77 Å and C II 1334.53 Å, but also the chromospheric Mg II k 2796.35 Å line are significantly enhanced and broadened. In addition, the event can be found in all the extreme-ultraviolet passbands of the Atmospheric Imaging Assembly and the derived differential emission measure profile increases between 4 and 15 MK (or 6.6 ≤ log T ≤ 7.2) in the transient brightening phase. It is possible that the penumbral transient brightening event is caused by magnetic reconnection. Title: High-Resolution Observations of Flare Precursors and Their Relationship with Magnetic Channels Authors: Wang, Haimin; Xu, Yan; Ahn, Kwangsu; Jing, Ju; Liu, Chang; Deng, Na; Huang, Nengyi; Gary, Dale E.; Cao, Wenda Bibcode: 2016SPD....4720501W Altcode: The study of precursors of flares is important for understanding the basic magnetic instability leading to solar flares, which can aid the forecasting of eruptions potentially related to severe space weather effects. Although literatures reported many important clues, high-resolution observations of pre-flare activities before a well-observed solar flare have been rare. Even rarely, the associated magnetic structures in fine scale (below 1") were also observed. In this study we take advantage of multiwavelength high-resolution observations completely covering the 2015 June 22 M6.6 flare, which were obtained under excellent seeing condition with the 1.6 m New Solar Telescope (NST) at Big Bear Solar Observatory. The NST data includes observations of the H-alpha line in five spectral positions at a spatial resolution of 0.1" and magnetograms at a resolution of 0.25". These are complemented by IRIS UV observations with a resolution of 0.25". We find that there are two episodes of pre-flare brightenings (precursors), which are spatially associated with magnetic channels, i.e., elongated structures comprising alternating magnetic polarity inversion lines (Zirin & Wang, 1993, Nature, 363, 426). The pre-flare chromospheric and coronal features reflect an extremely sheared magnetic topology, while the initiation of main flare brightenings correspond to a much less sheared configuration. RHESSI HXR observations reveal that the precursors have both thermal and nonthermal components, and the latter is further evidenced by the microwave observations of the newly expanded Solar Radio Array at Owens Valley.We further investigate the electric current system above the magnetic channels using NLFFF extrapolations, which show strong current sheets above the channel structure. This is consistent with the MHD modeling of Kusano et al (2012, Ap.J., 760, 31), who noted the importance of localized small-scale magnetic structure in triggering the eruption of the whole active region. We suggest that small-scale magnetic reconnection along the channels destabilizes the magnetic structure of the active region and subsequently triggers the main M6.6 flare and the associated halo CME. Title: Unprecedented Fine Structure of a Solar Flare Revealed by the 1.6~m New Solar Telescope Authors: Jing, Ju; Xu, Yan; Cao, Wenda; Liu, Chang; Gary, Dale E.; Wang, Haimin Bibcode: 2016SPD....47.0601J Altcode: Solar flares signify the sudden release of magnetic energy and are sources of so called space weather. The fine structures (below 500 km) of flares are rarely observed and are accessible to only a few instruments world-wide. Here we present observation of a solar flare using exceptionally high resolution images from the 1.6~m New Solar Telescope (NST) equipped with high order adaptive optics at Big Bear Solar Observatory (BBSO). The observation reveals the process of the flare in unprecedented detail, including the flare ribbon propagating across the sunspots, coronal rain (made of condensing plasma) streaming down along the post-flare loops, and the chromosphere's response to the impact of coronal rain, showing fine-scale brightenings at the footpoints of the falling plasma. Taking advantage of the resolving power of the NST, we measure the cross-sectional widths of flare ribbons, post-flare loops and footpoint brighenings, which generally lie in the range of 80-200 km, well below the resolution of most current instruments used for flare studies. Confining the scale of such fine structure provides an essential piece of information in modeling the energy transport mechanism of flares, which is an important issue in solar and plasma physics. Title: Unprecedented Fine Structure of a Solar Flare Revealed by the 1.6 m New Solar Telescope Authors: Jing, Ju; Xu, Yan; Cao, Wenda; Liu, Chang; Gary, Dale; Wang, Haimin Bibcode: 2016NatSR...624319J Altcode: 2016arXiv160408562J Solar flares signify the sudden release of magnetic energy and are sources of so called space weather. The fine structures (below 500 km) of flares are rarely observed and are accessible to only a few instruments world-wide. Here we present observation of a solar flare using exceptionally high resolution images from the 1.6 m New Solar Telescope (NST) equipped with high order adaptive optics at Big Bear Solar Observatory (BBSO). The observation reveals the process of the flare in unprecedented detail, including the flare ribbon propagating across the sunspots, coronal rain (made of condensing plasma) streaming down along the post-flare loops, and the chromosphere’s response to the impact of coronal rain, showing fine-scale brightenings at the footpoints of the falling plasma. Taking advantage of the resolving power of the NST, we measure the cross-sectional widths of flare ribbons, post-flare loops and footpoint brighenings, which generally lie in the range of 80-200 km, well below the resolution of most current instruments used for flare studies. Confining the scale of such fine structure provides an essential piece of information in modeling the energy transport mechanism of flares, which is an important issue in solar and plasma physics. Title: Resolving the Fan-spine Reconnection Geometry of a Small-scale Chromospheric Jet Event with the New Solar Telescope Authors: Zeng, Zhicheng; Chen, Bin; Ji, Haisheng; Goode, Philip R.; Cao, Wenda Bibcode: 2016ApJ...819L...3Z Altcode: 2016arXiv160204237Z Jets are ubiquitously present in both quiet and active regions on the Sun. They are widely believed to be driven by magnetic reconnection. A fan-spine structure has been frequently reported in some coronal jets and flares, and has been regarded as a signature of ongoing magnetic reconnection in a topology consisting of a magnetic null connected by a fan-like separatrix surface and a spine. However, for small-scale chromospheric jets, clear evidence of such structures is rather rare, although it has been implied in earlier works that showed an inverted-Y-shaped feature. Here we report high-resolution (0.″16) observations of a small-scale chromospheric jet obtained by the New Solar Telescope (NST) using 10830 Å filtergrams. Bi-directional flows were observed across the separatrix regions in the 10830 Å images, suggesting that the jet was produced due to magnetic reconnection. At the base of the jet, a fan-spine structure was clearly resolved by the NST, including the spine and the fan-like surface, as well as the loops before and after the reconnection. A major part of this fan-spine structure, with the exception of its bright footpoints and part of the base arc, was invisible in the extreme ultraviolet and soft X-ray images (observed by the Atmosphere Imaging Assembly and the X-Ray Telescope, respectively), indicating that the reconnection occurred in the upper chromosphere. Our observations suggest that the evolution of this chromospheric jet is consistent with a two-step reconnection scenario proposed by Török et al. Title: Bidirectional Outflows as Evidence of Magnetic Reconnection Leading to a Solar Microflare Authors: Hong, Jie; Ding, M. D.; Li, Ying; Yang, Kai; Cheng, Xin; Chen, Feng; Fang, Cheng; Cao, Wenda Bibcode: 2016ApJ...820L..17H Altcode: 2016arXiv160300941H Magnetic reconnection is a rapid energy release process that is believed to be responsible for flares on the Sun and stars. Nevertheless, such flare-related reconnection is mostly detected to occur in the corona, while there have been few studies concerning the reconnection in the chromosphere or photosphere. Here, we present both spectroscopic and imaging observations of magnetic reconnection in the chromosphere leading to a microflare. During the flare peak time, chromospheric line profiles show significant blueshifted/redshifted components on the two sides of the flaring site, corresponding to upflows and downflows with velocities of ±(70-80) km s-1, comparable with the local Alfvén speed as expected by the reconnection in the chromosphere. The three-dimensional nonlinear force-free field configuration further discloses twisted field lines (a flux rope) at a low altitude, cospatial with the dark threads in He I 10830 Å images. The instability of the flux rope may initiate the flare-related reconnection. These observations provide clear evidence of magnetic reconnection in the chromosphere and show the similar mechanisms of a microflare to those of major flares. Title: Ultra-narrow Negative Flare Front Observed in Helium-10830 Å Using the 1.6 m New Solar Telescope Authors: Xu, Yan; Cao, Wenda; Ding, Mingde; Kleint, Lucia; Su, Jiangtao; Liu, Chang; Ji, Haisheng; Chae, Jongchul; Jing, Ju; Cho, Kyuhyoun; Cho, Kyungsuk; Gary, Dale; Wang, Haimin Bibcode: 2016ApJ...819...89X Altcode: 2016arXiv160104729X Solar flares are sudden flashes of brightness on the Sun and are often associated with coronal mass ejections and solar energetic particles that have adverse effects on the near-Earth environment. By definition, flares are usually referred to as bright features resulting from excess emission. Using the newly commissioned 1.6 m New Solar Telescope at Big Bear Solar Observatory, we show a striking “negative” flare with a narrow but unambiguous “dark” moving front observed in He I 10830 Å, which is as narrow as 340 km and is associated with distinct spectral characteristics in Hα and Mg II lines. Theoretically, such negative contrast in He I 10830 Å can be produced under special circumstances by nonthermal electron collisions or photoionization followed by recombination. Our discovery, made possible due to unprecedented spatial resolution, confirms the presence of the required plasma conditions and provides unique information in understanding the energy release and radiative transfer in astronomical objects. Title: Observations of Oppositely Directed Umbral Wavefronts Rotating in Sunspots Obtained from the New Solar Telescope of BBSO Authors: Su, J. T.; Ji, K. F.; Cao, W.; Banerjee, D.; Priya, T. G.; Zhao, J. S.; Bai, X. Y.; Chen, J.; Zhang, M.; Ji, H. S. Bibcode: 2016ApJ...817..117S Altcode: We study the umbral waves as observed by chromospheric imaging observations of two sunspots with the New Solar Telescope at the Big Bear Solar Observatory. We find that the wavefronts (WFs) rotate clockwise and form a one-armed spiral structure in the first sunspot, whereas two- and three-armed structures arise in the second sunspot where the WFs rotate anticlockwise and clockwise alternately. All the spiral arms display propagation outwards and become running penumbral waves once they cross the umbral boundaries, suggesting that the umbral and penumbral waves propagate along the same inclined field lines. We propose that the one-armed spiral structure may be produced by the WF reflections at the chromospheric umbral light bridge, and the multi-armed spirals may be related to the twist of the magnetic field in the umbra. Additionally, the time lag of the umbral oscillations in between the data of He I 10830 Å and {{H}}α -0.4 Å is ∼17 s, and it is ∼60 s for that in between the data of 304 Å and {{H}}α -0.4 Å. This indicates that these disturbances are slow magnetoacoustic waves in nature, and that they propagate upward along the inclined lines with fast radial expansions causing horizontal velocities of the running waves. Title: Interference of the Running Waves at Light Bridges of a Sunspot Authors: Su, J. T.; Ji, K. F.; Banerjee, D.; Cao, W. D.; Priya, T. G.; Zhao, J. S.; Yu, S. J.; Ji, H. S.; Zhang, M. Bibcode: 2016ApJ...816...30S Altcode: The observations of chromospheric oscillations of two umbral light bridges (LBs) within a sunspot from NOAA Active Region 12127 are presented. It was found that the running umbral waves with periods of 2.2-2.6 minutes underwent very fast damping before approaching umbral boundaries, while those with higher periods (>2.6 minutes) could propagate outside umbrae. On two sides of each LB adjacent to umbrae, the cross-wavelet spectra displayed that the oscillations on them had a common significant power region with dominant frequencies of 2-6 minutes and phase differences of ∼90°. A counterstream of two running umbral waves in the 2-6 minute frequency range propagated toward the LBs, where they encountered each other and gave rise to constructive or even destructive interference on the LBs. In addition, the velocity and density perturbations on the LBs were found in opposite phases suggesting that the perturbations were caused by the downward propagating waves. Title: Statistical Analysis of Filament Features Based on the Hα Solar Images from 1988 to 2013 by Computer Automated Detection Method Authors: Hao, Q.; Fang, C.; Cao, W.; Chen, P. F. Bibcode: 2015ApJS..221...33H Altcode: 2015arXiv151104692H We improve our filament automated detection method which was proposed in our previous works. It is then applied to process the full disk Hα data mainly obtained by the Big Bear Solar Observatory from 1988 to 2013, spanning nearly three solar cycles. The butterfly diagrams of the filaments, showing the information of the filament area, spine length, tilt angle, and the barb number, are obtained. The variations of these features with the calendar year and the latitude band are analyzed. The drift velocities of the filaments in different latitude bands are calculated and studied. We also investigate the north-south (N-S) asymmetries of the filament numbers in total and in each subclass classified according to the filament area, spine length, and tilt angle. The latitudinal distribution of the filament number is found to be bimodal. About 80% of all the filaments have tilt angles within [0°, 60°]. For the filaments within latitudes lower (higher) than 50°, the northeast (northwest) direction is dominant in the northern hemisphere and the southeast (southwest) direction is dominant in the southern hemisphere. The latitudinal migrations of the filaments experience three stages with declining drift velocities in each of solar cycles 22 and 23, and it seems that the drift velocity is faster in shorter solar cycles. Most filaments in latitudes lower (higher) than 50° migrate toward the equator (polar region). The N-S asymmetry indices indicate that the southern hemisphere is the dominant hemisphere in solar cycle 22 and the northern hemisphere is the dominant one in solar cycle 23. Title: Detection of a Fine-scale Discontinuity of Photospheric Magnetic Fields Associated with Solar Coronal Loop Brightenings Authors: Song, Donguk; Chae, Jongchul; Park, Soyoung; Cho, Kyung-Suk; Lim, Eun-Kyung; Ahn, Kwangsu; Cao, Wenda Bibcode: 2015ApJ...810L..16S Altcode: We present the transient brightening of a coronal loop and an associated fine-scale magnetic discontinuity detected in the photosphere. Utilizing the high-resolution data taken with the Fast Imaging Solar Spectrograph and InfraRed Imaging Magnetograph of the New Solar Telescope at Big Bear Solar Observatory, we detect a narrow lane of intense horizontal magnetic field representing a magnetic discontinuity. It was visible as a dark lane partially encircling a pore in the continuum image, and was located near one of the footpoints of a small coronal loop that experienced transient brightenings. The horizontal field strength gradually increased before the loop brightening, and then rapidly decreased in the impulsive phase of the brightening, suggesting the increase of the magnetic non-potentiality at the loop footpoint and the sudden release of magnetic energy via magnetic reconnection. Our results support the nanoflare theory that coronal heating events are caused by magnetic reconnection events at fine-scale magnetic discontinuities. Title: Objective Image-Quality Assessment for High-Resolution Photospheric Images by Median Filter-Gradient Similarity Authors: Deng, Hui; Zhang, Dandan; Wang, Tianyu; Ji, Kaifan; Wang, Feng; Liu, Zhong; Xiang, Yongyuan; Jin, Zhenyu; Cao, Wenda Bibcode: 2015SoPh..290.1479D Altcode: 2015SoPh..tmp...34D All next-generation ground-based and space-based solar telescopes require a good quality-assessment metric to evaluate their imaging performance. In this paper, a new image quality metric, the median filter-gradient similarity (MFGS) is proposed for photospheric images. MFGS is a no-reference/blind objective image-quality metric (IQM) by a measurement result between 0 and 1 and has been performed on short-exposure photospheric images captured by the New Vacuum Solar Telescope (NVST) of the Fuxian Solar Observatory and by the Solar Optical Telescope (SOT) onboard the Hinode satellite, respectively. The results show that (1) the measured value of the MFGS changes monotonically from 1 to 0 with degradation of image quality; (2) there exists a linear correlation between the measured values of the MFGS and the root-mean-square contrast (RMS-contrast) of the granulation; (3) the MFGS is less affected by the image contents than the granular RMS-contrast. Overall, the MFGS is a good alternative for the quality assessment of photospheric images. Title: Negative Flare Emissions Observed in Euv By SDO/AIA Authors: Xu, Y.; Liu, C.; Cao, W.; Jing, J.; Wang, H. Bibcode: 2014AGUFMSH51C4165X Altcode: In this study, we present a large flare showing negative emissions in the EUV passbands observed by SDO/AIA. Contrary to ordinary flare emission represented by an increase of intensity, negative flare emission refers to as a decrease of intensity during flares. In the literature, negative flare emissions were usually reported by stellar observations. Only a few negative solar flares were observed in He I D3 in 1970s and one event observed in the near Infrared at 8542 Å in 2001. On 2014-Jan-07, an X1.2 flare occurred near the solar disk center with a complex magnetic configuration, showing multiple flare ribbons. Among them a remote flare ribbon is located to the southwest from the flare core region. A small portion of the remote ribbon became darkened from about 18:45 UT, while the rest of the ribbon remained bright. This darkening lasted for more than one hour and did not show obvious motion. Therefore, we exclude the possibility of transient coronal hole associated with EUV waves. By comparing with SDO/HMI LOS magnetograms, we find that the negative flare regions are associated with weak magnetic fields, lower than 50 Gauss. In contrast, the bright flare ribbons are co-spatial with strong magnetic fields above 200 Gauss. Furthermore, we investigate the properties of the negative emission by examining the temporal evolution of its intensity and area. Finally, we discuss the possible mechanisms in generating the negative emissions. Title: Active Region Coronal Rain Event Observed by the Fast Imaging Solar Spectrograph on the NST Authors: Ahn, Kwangsu; Chae, Jongchul; Cho, Kyung-Suk; Song, Donguk; Yang, Heesu; Goode, Philip R.; Cao, Wenda; Park, Hyungmin; Nah, Jakyung; Jang, Bi-Ho; Park, Young-Deuk Bibcode: 2014SoPh..289.4117A Altcode: 2014SoPh..tmp...98A The Fast Imaging Solar Spectrograph (FISS) is being operated on the New Solar Telescope of the Big Bear Solar Observatory. It simultaneously records spectra of Hα and Ca II 8542 Å lines, and this dual-spectra measurement provides an estimate of the temperature and nonthermal speed components. We observed a loop structure in AR 11305 using the FISS, SDO/AIA, and STEREO/EUVI in 304 Å, and found plasma material falling along the loop from a coronal height into the umbra of a sunspot, which accelerated up to 80 km s−1. We also observed C2 and C7 flare events near the loop. The temperature of the downflows was in the range of 10 000 - 33 000 K, increasing toward the umbra. The temperature of the flow varied with time, and the temperature near the footpoint rose immediately after the C7 flare, but the temperature toward the umbra remained the same. There seemed to be a temporal correlation between the amount of downflow material and the observed C-class flares. The downflows decreased gradually soon after the flares and then increased after a few hours. These high-speed red-shift events occurred continuously during the observations. The flows observed on-disk in Hα and Ca II 8542 Å appeared as fragmented, fuzzy condensed material falling from the coronal heights when seen off-limb with STEREO/EUVI at 304 Å. Based on these observations, we propose that these flows were an on-disk signature of coronal rain. Title: A Flare Observed in Coronal, Transition Region, and Helium I 10830 Å Emissions Authors: Zeng, Zhicheng; Qiu, Jiong; Cao, Wenda; Judge, Philip G. Bibcode: 2014ApJ...793...87Z Altcode: 2014arXiv1408.0236Z On 2012 June 17, we observed the evolution of a C-class flare associated with the eruption of a filament near a large sunspot in the active region NOAA 11504. We obtained high spatial resolution filtergrams using the 1.6 m New Solar Telescope at the Big Bear Solar Observatory in broadband TiO at 706 nm (bandpass: 10 Å) and He I 10830 Å narrow band (bandpass: 0.5 Å, centered 0.25 Å to the blue). We analyze the spatio-temporal behavior of the He I 10830 Å data, which were obtained over a 90''×90'' field of view with a cadence of 10 s. We also analyze simultaneous data from the Atmospheric Imaging Assembly and Extreme Ultraviolet Variability Experiment instruments on board the Solar Dynamics Observatory spacecraft, and data from the Reuven Ramaty High Energy Solar Spectroscopic Imager and GOES spacecrafts. Non-thermal effects are ignored in this analysis. Several quantitative aspects of the data, as well as models derived using the "0D" enthalpy-based thermal evolution of loops model code, indicate that the triplet states of the 10830 Å multiplet are populated by photoionization of chromospheric plasma followed by radiative recombination. Surprisingly, the He II 304 Å line is reasonably well matched by standard emission measure calculations, along with the C IV emission which dominates the Atmosphere Imaging Assembly 1600 Å channel during flares. This work lends support to some of our previous work combining X-ray, EUV, and UV data of flares to build models of energy transport from corona to chromosphere. Title: Spectral Observations of Ellerman Bombs and Fitting with a Two-cloud Model Authors: Hong, Jie; Ding, M. D.; Li, Ying; Fang, Cheng; Cao, Wenda Bibcode: 2014ApJ...792...13H Altcode: 2014arXiv1407.3048H We study the Hα and Ca II 8542 Å line spectra of four typical Ellerman bombs (EBs) in the active region NOAA 11765 on 2013 June 6, observed with the Fast Imaging Solar Spectrograph installed at the 1.6 m New Solar Telescope at Big Bear Solar Observatory. Considering that EBs may occur in a restricted region in the lower atmosphere, and that their spectral lines show particular features, we propose a two-cloud model to fit the observed line profiles. The lower cloud can account for the wing emission, and the upper cloud is mainly responsible for the absorption at line center. After choosing carefully the free parameters, we get satisfactory fitting results. As expected, the lower cloud shows an increase of the source function, corresponding to a temperature increase of 400-1000 K in EBs relative to the quiet Sun. This is consistent with previous results deduced from semi-empirical models and confirms that local heating occurs in the lower atmosphere during the appearance of EBs. We also find that the optical depths can increase to some extent in both the lower and upper clouds, which may result from either direct heating in the lower cloud, or illumination by an enhanced radiation on the upper cloud. The velocities derived from this method, however, are different from those obtained using the traditional bisector method, implying that one should be cautious when interpreting this parameter. The two-cloud model can thus be used as an efficient method to deduce the basic physical parameters of EBs. Title: AO-308: the high-order adaptive optics system at Big Bear Solar Observatory Authors: Shumko, Sergey; Gorceix, Nicolas; Choi, Seonghwan; Kellerer, Aglaé; Cao, Wenda; Goode, Philip R.; Abramenko, Volodymyr; Richards, Kit; Rimmele, Thomas R.; Marino, Jose Bibcode: 2014SPIE.9148E..35S Altcode: In this paper we present Big Bear Solar Observatory's (BBSO) newest adaptive optics system - AO-308. AO-308 is a result of collaboration between BBSO and National Solar Observatory (NSO). AO-308 uses a 357 actuators deformable mirror (DM) from Xinetics and its wave front sensor (WFS) has 308 sub-apertures. The WFS uses a Phantom V7.3 camera which runs at 2000 Hz with the region of interest of 416×400 pixels. AO-308 utilizes digital signal processors (DSPs) for image processing. AO-308 has been successfully used during the 2013 observing season. The system can correct up to 310 modes providing diffraction limited images at all wavelengths of interest. Title: Control and operation of the 1.6 m New Solar Telescope in Big Bear Authors: Varsik, J.; Plymate, C.; Goode, P.; Kosovichev, A.; Cao, W.; Coulter, R.; Ahn, K.; Gorceix, N.; Shumko, S. Bibcode: 2014SPIE.9147E..5DV Altcode: The 1.6m New Solar Telescope (NST) has developed a modern and comprehensive suite of instruments which allow high resolution observations of the Sun. The current instrument package comprises diffraction limited imaging, spectroscopic and polarimetric instruments covering the wavelength range from 0.4 to 5.0 microns. The instruments include broadband imaging, visible and near-infrared scanning Fabry-Perot interferometers, an imaging spectropolarimeter, a fast visible-light imaging spectrograph, and a unique new scanning cryogenic infrared spectrometer/spectropolarimeter that is nearing completion. Most instruments are operated with a 308 subaperture adaptive optics system, while the thermal-IR spectrometer has a correlation tracker. This paper reports on the current observational programs and operational performance of the telescope and instrumentation. The current control, data processing, and archiving systems are also briefly discussed. Title: Optical design of the Big Bear Solar Observatory's multi-conjugate adaptive optics system Authors: Zhang, Xianyu; Gorceix, Nicolas; Schmidt, Dirk; Goode, Philip R.; Cao, Wenda; Rimmele, Thomas R.; Coulter, Roy Bibcode: 2014SPIE.9148E..50Z Altcode: A multi-conjugate adaptive optics (MCAO) system is being built for the world's largest aperture 1.6m solar telescope, New Solar Telescope, at the Big Bear Solar Observatory (BBSO). The BBSO MCAO system employs three deformable mirrors to enlarge the corrected field of view. In order to characterize the MCAO performance with different optical configurations and DM conjugated altitudes, the BBSO MCAO setup also needs to be flexible. In this paper, we present the optical design of the BBSO MCAO system. Title: Study of Two Successive Three-ribbon Solar Flares Using BBSO/NST Observations Authors: Wang, Haimin; Liu, Chang; Deng, Na; Zeng, Zhicheng; Xu, Yan; Jing, Ju; Cao, Wenda Bibcode: 2014AAS...22412304W Altcode: We studied two rarely observed three-ribbon flares (M1.9 and C9.2) on 2012 July 6 in NOAA AR 11515, which we found using Hα observations of 0.1 arcsec resolution from the New Solar Telescope and Ca II H images from Hinode. The flaring site is characterized by an intriguing "fish-bone-like" morphology evidenced by both Halpha images and a nonlinear force-free field (NLFFF) extrapolation, where two semi-parallel rows of low-lying, sheared loops connect an elongated, parasitic negative field with the sandwiching positive fields. The NLFFF model also shows that the two rows of loops are asymmetric in height and have opposite twists, and are enveloped by large-scale field lines including open fields. The two flares occurred in succession within half an hour and are located at the two ends of the flaring region. The three ribbons of each flare run parallel to the magnetic polarity inversion line, with the outer two lying in the positive field and the central one in the negative field. Both flares show surge-like flows in Halpha apparently toward the remote region, while the C9.2 flare is also accompanied by EUV jets possibly along the open field lines. Interestingly, the 12-25 keV hard X-ray sources of the C9.2 flare first line up with the central ribbon then shift to concentrate on the top of the higher branch of loops. These results are discussed in favor of reconnection along the coronal null line, producing the three flare ribbons and the associated ejections. Title: A FLARE OBSERVED IN CORONAL, TRANSITION REGION AND HELIUM I 10830 Å EMISSIONS Authors: Zeng, Zhicheng; Qiu, Jiong; Cao, Wenda; Judge, Philip G. Bibcode: 2014AAS...22412309Z Altcode: On June 17, 2012, we observed the evolution of a C-class flare associated with the eruption of a filament near a large sunspot in the active region NOAA 11504. We obtained high spatial resolution filtergrams using the 1.6 m New Solar Telescope at the Big Bear Solar Observatory in TiO broad-band (bandpass: 10 Å)and He I 10830 Å narrow-band (bandpass: 0.5 Å, centered 0.25 Å to the blue). We analyze the spatio-temporal behavior of the He I 10830 Å data, which were obtained over a 90×90 arcsends field of view with a cadence of 10 sec. We also analyze simultaneous data from the Atmospheric Imaging Assembly and Extreme Ultraviolet Variability Experiment instruments on board the Solar Dynamics Observatoryspacecraft, and data from Reuven Ramaty High Energy Solar Spectroscopic Imager and GOES spacecrafts. Several quantitative aspects of the data, as well as models derived using the “0D” Enthalpy-Based Thermal Evolution of Loops model (EBTEL: Klimchuk et al. 2008) code, indicate that the 10830 Å multiplet is formed primarily by photoionization of chromospheric plasma followed by radiative recombination. Surprisingly, the He II 304 Å line is reasonably well matched by standard emission measure calculations, along with the C IV emission which dominates the AIA 1600 Å channel during flares. This work lends support to some of our previous work combining X-ray, EUV and UV data of flares to buildmodels of energy transport from corona to chromosphere. Title: High-resolution Observation of the Smallest Ellerman Bombs Authors: Fang, Cheng; Tang, Yu-hua; Li, Zhen; Xu, Zhi; Cao, Wenda; Guo, Yang Bibcode: 2014cosp...40E.834F Altcode: By use of the high-resolution spectral data obtained with the largest solar telescope NST/BBSO in 2013 June, the characteristics of 3 well-observed smallest EBs have been analyzed. Their sizes are less than 0.5 are second and their durations are only 2-3 minutes. The most obvious characteristic of the EB spectra is the two emission bumps at the two wings of both Hα and CaII 8542 Å lines. They are located near the longitudinal magnetic polarity inversion lines and accompanied by mass motions. The semi-empirical atmospheric models for the EBs are computed. The common characteristic is the heating in the upper photosphere. The temperature enhancement is about 400-500 K. These imply that the EBs can probably be produced by the magnetic reconnection in the solar lower atmosphere. The radiative and kinetic energies of the EBs are estimated, and the possible mechanism of triggering the EBs is discussed. Title: Study of Two Successive Three-ribbon Solar Flares on 2012 July 6 Authors: Wang, Haimin; Liu, Chang; Deng, Na; Zeng, Zhicheng; Xu, Yan; Jing, Ju; Cao, Wenda Bibcode: 2014ApJ...781L..23W Altcode: 2013arXiv1312.6649W This Letter reports two rarely observed three-ribbon flares (M1.9 and C9.2) on 2012 July 6 in NOAA AR 11515, which we found using Hα observations of 0.''1 resolution from the New Solar Telescope and Ca II H images from Hinode. The flaring site is characterized by an intriguing "fish-bone-like" morphology evidenced by both Hα images and a nonlinear force-free field (NLFFF) extrapolation, where two semi-parallel rows of low-lying, sheared loops connect an elongated, parasitic negative field with the sandwiching positive fields. The NLFFF model also shows that the two rows of loops are asymmetric in height and have opposite twists, and are enveloped by large-scale field lines including open fields. The two flares occurred in succession within half an hour and are located at the two ends of the flaring region. The three ribbons of each flare run parallel to the magnetic polarity inversion line, with the outer two lying in the positive field and the central one in the negative field. Both flares show surge-like flows in Hα apparently toward the remote region, while the C9.2 flare is also accompanied by EUV jets possibly along the open field lines. Interestingly, the 12-25 keV hard X-ray sources of the C9.2 flare first line up with the central ribbon then shift to concentrate on the top of the higher branch of loops. These results are discussed in favor of reconnection along the coronal null line, producing the three flare ribbons and the associated ejections. Title: Temperature of Solar Prominences Obtained with the Fast Imaging Solar Spectrograph on the 1.6 m New Solar Telescope at the Big Bear Solar Observatory Authors: Park, Hyungmin; Chae, Jongchul; Song, Donguk; Maurya, Ram Ajor; Yang, Heesu; Park, Young-Deuk; Jang, Bi-Ho; Nah, Jakyoung; Cho, Kyung-Suk; Kim, Yeon-Han; Ahn, Kwangsu; Cao, Wenda; Goode, Philip R. Bibcode: 2013SoPh..288..105P Altcode: We observed solar prominences with the Fast Imaging Solar Spectrograph (FISS) at the Big Bear Solar Observatory on 30 June 2010 and 15 August 2011. To determine the temperature of the prominence material, we applied a nonlinear least-squares fitting of the radiative transfer model. From the Doppler broadening of the Hα and Ca II lines, we determined the temperature and nonthermal velocity separately. The ranges of temperature and nonthermal velocity were 4000 - 20 000 K and 4 - 11 km s−1. We also found that the temperature varied much from point to point within one prominence. Title: Fast Imaging Solar Spectrograph of the 1.6 Meter New Solar Telescope at Big Bear Solar Observatory Authors: Chae, Jongchul; Park, Hyung-Min; Ahn, Kwangsu; Yang, Heesu; Park, Young-Deuk; Nah, Jakyoung; Jang, Bi Ho; Cho, Kyung-Suk; Cao, Wenda; Goode, Philip R. Bibcode: 2013SoPh..288....1C Altcode: 2012SoPh..tmp..248C For high resolution spectral observations of the Sun - particularly its chromosphere, we have developed a dual-band echelle spectrograph named Fast Imaging Solar Spectrograph (FISS), and installed it in a vertical optical table in the Coudé Lab of the 1.6 meter New Solar Telescope at Big Bear Solar Observatory. This instrument can cover any part of the visible and near-infrared spectrum, but it usually records the Hα band and the Ca II 8542 Å band simultaneously using two CCD cameras, producing data well suited for the study of the structure and dynamics of the chromosphere and filaments/prominences. The instrument does imaging of high quality using a fast scan of the slit across the field of view with the aid of adaptive optics. We describe its design, specifics, and performance as well as data processing Title: Doppler Shifts of the Hα Line and the Ca II 854.2 nm Line in a Quiet Region of the Sun Observed with the FISS/NST Authors: Chae, Jongchul; Park, Hyung-Min; Ahn, Kwangsu; Yang, Heesu; Park, Young-Deuk; Cho, Kyung-Suk; Cao, Wenda Bibcode: 2013SoPh..288...89C Altcode: The characteristics of Doppler shifts in a quiet region of the Sun are compared between the Hα line and the Ca II infrared line at 854.2 nm. A small area of 16″×40″ was observed for about half an hour with the Fast Imaging Solar Spectrograph (FISS) of the 1.6 meter New Solar Telescope (NST) at Big Bear Solar Observatory. The observed area contains a network region and an internetwork region, and identified in the network region are fibrils and bright points. We infer Doppler velocity vm from each line profile at each individual point with the lambdameter method as a function of half wavelength separation Δλ. It is confirmed that the bisector of the spatially averaged Ca II line profile has an inverse C-shape with a significant peak redshift of + 1.8 km s−1. In contrast, the bisector of the spatially averaged Hα line profile has a C-shape with a small peak blueshift of − 0.5 km s−1. In both lines, the bisectors of bright network points are significantly redshifted not only at the line centers, but also at the wings. The Ca II Doppler shifts are found to be correlated with the Hα ones with the strongest correlation occurring in the internetwork region. Moreover, we find that here the Doppler shifts in the two lines are essentially in phase. We discuss the physical implications of our results in view of the formation of the Hα line and Ca II 854.2 nm line in the quiet region chromosphere. Title: Connection Between Chromospheric Events and Photospheric Dynamics Authors: Anđić, A.; Chae, J.; Park, H.; Yang, H.; Ahn, K.; Cao, W.; Park, Y. D. Bibcode: 2013SoPh..288...55A Altcode: 2012SoPh..tmp..232A We analyzed chromospheric events and their connection to oscillation phenomena and photospheric dynamics. The observations were done with the New Solar Telescope of Big Bear Solar Observatory using a broad-band imager at the wavelength of a TiO band and FISS spectrograph scanning Ca II and Hα spectral lines. The event in Ca II showed strong plasma flows and propagating waves in the chromosphere. The movement of the footpoints of flux tubes in the photosphere indicated flux tube entanglement and magnetic reconnection as a possible cause of the observed brightening and waves propagating in the chromosphere. An upward propagating train of waves was observed at the site of the downflow event in Hα. There was no clear relationship between photospheric waves and the Ca II and Hα events. Our observations indicate that chromospheric waves that were previously thought to originate from the photosphere may be generated by some events in the chromosphere as well. Title: Infrared Observations from the New Solar Telescope at Big Bear Authors: Goode, Philip R.; Cao, Wenda Bibcode: 2013SoPh..287..315G Altcode: The 1.6 m clear aperture solar telescope in Big Bear is operational and with its adaptive optics (AO) system it provides diffraction limited solar imaging and polarimetry in the near-infrared (NIR). While the AO system is being upgraded to provide diffraction limited imaging at bluer wavelengths, the instrumentation and observations are concentrated in the NIR. The New Solar Telescope (NST) operates in campaigns, making it the ideal ground-based telescope to provide complementary/supplementary data to SDO and Hinode. The NST makes photometric observations in Hα (656.3 nm) and TiO (705.6 nm) among other lines. As well, the NST collects vector magnetograms in the 1565 nm lines and is beginning such observations in 1083.0 nm. Here we discuss the relevant NST instruments, including AO, and present some results that are germane to NASA solar missions. Title: Study of Rapid Formation of a δ Sunspot Associated with the 2012 July 2 C7.4 Flare Using High-resolution Observations of the New Solar Telescope Authors: Wang, Haimin; Liu, Chang; Wang, Shuo; Deng, Na; Xu, Yan; Jing, Ju; Cao, Wenda Bibcode: 2013ApJ...774L..24W Altcode: 2013arXiv1308.2639W Rapid, irreversible changes of magnetic topology and sunspot structure associated with flares have been systematically observed in recent years. The most striking features include the increase of the horizontal field at the polarity inversion line (PIL) and the co-spatial penumbral darkening. A likely explanation of the above phenomenon is the back reaction to the coronal restructuring after eruptions: a coronal mass ejection carries the upward momentum while the downward momentum compresses the field lines near the PIL. Previous studies could only use low-resolution (above 1'') magnetograms and white-light images. Therefore, the changes are mostly observed for X-class flares. Taking advantage of the 0.''1 spatial resolution and 15 s temporal cadence of the New Solar Telescope at the Big Bear Solar Observatory, we report in detail the rapid formation of sunspot penumbra at the PIL associated with the C7.4 flare on 2012 July 2. It is unambiguously shown that the solar granulation pattern evolves to an alternating dark and bright fibril structure, the typical pattern of penumbra. Interestingly, the appearance of such a penumbra creates a new δ sunspot. The penumbral formation is also accompanied by the enhancement of the horizontal field observed using vector magnetograms from the Helioseismic and Magnetic Imager. We explain our observations as being due to the eruption of a flux rope following magnetic cancellation at the PIL. Subsequently, the re-closed arcade fields are pushed down toward the surface to form the new penumbra. NLFFF extrapolation clearly shows both the flux rope close to the surface and the overlying fields. Title: Characteristic Length of Energy-containing Structures at the Base of a Coronal Hole Authors: Abramenko, V. I.; Zank, G. P.; Dosch, A.; Yurchyshyn, V. B.; Goode, P. R.; Ahn, K.; Cao, W. Bibcode: 2013ApJ...773..167A Altcode: 2013arXiv1307.4421A An essential parameter for models of coronal heating and fast solar wind acceleration that rely on the dissipation of MHD turbulence is the characteristic energy-containing length λ of the squared velocity and magnetic field fluctuations (u 2 and b 2) transverse to the mean magnetic field inside a coronal hole (CH) at the base of the corona. The characteristic length scale directly defines the heating rate. We use a time series analysis of solar granulation and magnetic field measurements inside two CHs obtained with the New Solar Telescope at Big Bear Solar Observatory. A data set for transverse magnetic fields obtained with the Solar Optical Telescope/Spectro-Polarimeter on board the Hinode spacecraft was utilized to analyze the squared transverse magnetic field fluctuations b_t^2. Local correlation tracking was applied to derive the squared transverse velocity fluctuations u 2. We find that for u 2 structures, the Batchelor integral scale λ varies in a range of 1800-2100 km, whereas the correlation length sigmav and the e-folding length L vary between 660 and 1460 km. Structures for b_t^2 yield λ ≈ 1600 km, sigmav ≈ 640 km, and L ≈ 620 km. An averaged (over λ, sigmav, and L) value of the characteristic length of u 2 fluctuations is 1260 ± 500 km, and that of b_t^2 is 950 ± 560 km. The characteristic length scale in the photosphere is approximately 1.5-50 times smaller than that adopted in previous models (3-30 × 103 km). Our results provide a critical input parameter for current models of coronal heating and should yield an improved understanding of fast solar wind acceleration. Title: The New Solar Telescope (NST): What’s Next ? Authors: Cao, Wenda; Goode, P. R.; NST Team Bibcode: 2013SPD....4440006C Altcode: The 1.6 m, off-axis, clear aperture New Solar Telescope (NST) has been in regular operation in Big Bear Solar Observatory since 2009. The NST is the first facility class solar telescope built in the U.S. in a generation, which already offers a significant improvement in ground-based high angular resolution capabilities. This presentation reports the up-to-date progress on the NST and its 2nd generation instruments including the AO system (AO-308), the Near-InfraRed Imaging Spectro-polarimeter (NIRIS), the Visible Imaging Spectrometer (VIS), and the Cryogenic Infrared Spectrograph (CYRA). Title: Observation of Magnetic Reconnection Driven by Granular Scale Advection Authors: Zeng, Zhichen; Cao, W.; Ji, H. Bibcode: 2013SPD....44...01Z Altcode: We report the first evidence of magnetic reconnection driven by advection in a rapidly developing large granule, using high spatial resolution observations of a small surge event (base size 4‧‧ by 4‧‧) with the 1.6 meter aperture New Solar Telescope (NST) at Big Bear Solar Observatory. The observations were carried out in narrow-band (0.5 Å) Helium I 10830 Å and broad-band (10 Å) TiO 7057 Å. Since He I 10830 Å triplet has very high excitation level and is optically thin, its filtergrams enable us to investigate the surge from the photosphere through the chromosphere into the lower corona. Simultaneous space data from Atmospheric Imaging Assembly (AIA) and Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO) were used in the analysis. It is shown that the surge is spatio-temporally associated with magnetic flux emergence in the rapidly developing large granule. During the development of the granule, its advecting flow ( 2 km/ s) squeezed the magnetic flux into an intergranular lane area, where a magnetic flux concentration was formed and the neighboring flux with opposite magnetic polarity was cancelled. During the cancellation, the surge was produced as absorption in He I 10830 Å filtergrams while simultaneous EUV brightening occurred at its base. The observations clearly indicate evidence of finest-scale reconnection process driven by the granule’s motion. Title: Observation of Magnetic Reconnection Driven by Granular Scale Advection Authors: Zeng, Zhicheng; Cao, Wenda; Ji, Haisheng Bibcode: 2013ApJ...769L..33Z Altcode: We report the first evidence of magnetic reconnection driven by advection in a rapidly developing large granule using high spatial resolution observations of a small surge event (base size ~ 4'' × 4'') with the 1.6 m aperture New Solar Telescope at the Big Bear Solar Observatory. The observations were carried out in narrowband (0.5 Å) He I 10830 Å and broadband (10 Å) TiO 7057 Å. Since He I 10830 Å triplet has a very high excitation level and is optically thin, its filtergrams enable us to investigate the surge from the photosphere through the chromosphere into the lower corona. Simultaneous space data from the Atmospheric Imaging Assembly and Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory were used in the analysis. It is shown that the surge is spatio-temporally associated with magnetic flux emergence in the rapidly developing large granule. During the development of the granule, its advecting flow (~2 km s-1) squeezed the magnetic flux into an intergranular lane area, where a magnetic flux concentration was formed and the neighboring flux with opposite magnetic polarity was canceled. During the cancellation, the surge was produced as absorption in He I 10830 Å filtergrams while simultaneous EUV brightening occurred at its base. The observations clearly indicate evidence of a finest-scale reconnection process driven by the granule's motion. Title: NIRIS: The Second Generation Near-Infrared Imaging Spectro-polarimeter for the 1.6 Meter New Solar Telescope Authors: Cao, W.; Goode, P. R.; Ahn, K.; Gorceix, N.; Schmidt, W.; Lin, H. Bibcode: 2012ASPC..463..291C Altcode: The largest aperture solar telescope, the 1.6 m New Solar Telescope (NST) has been installed at the Big Bear Solar Observatory (BBSO). To take full advantage of the NST's greatest potential, we are upgrading the routinely operational InfraRed Imaging Magnetograph (IRIM) to its second generation, the NIRIS (Near-InfraRed Imaging Spectropolarimeter). NIRIS will offer unprecedented high resolution spectroscopic and polarimetric imaging data of the solar atmosphere from the deepest photosphere through the base of the corona. With the aid of the BBSO adaptive optics (AO) system, the spatial resolution will be close to the diffraction limit of the NST. The spectroscopic cadence will reach one second, while polarimetric measurements, including Stokes I, Q, U, V profiles, remain at a better than 10 s cadence. Polarization sensitivity is expected to be reach ∼ 10-4Ic. NIRIS will cover a broad spectral range from 1.0 to 1.7μm, with particular attention to two unique spectral lines: the Fe I 1565 nm doublet has already proven to be the most sensitive to Zeeman effect for probing the magnetic field in the deepest photosphere; the He I 1083 nm multiplet is one of the best currently available diagnostic of upper chromospheric magnetic fields that allows one to map the vector field at the base of the corona. NIRIS will be built on dual Fabry-Pérot Interferometers (FPIs), each of which has an aperture of 100 mm. The larger aperture of FPIs allows the available field-of-view up to one and half minutes with a spectral power of ∼ 105. Title: The 1.6 m Off-Axis New Solar Telescope (NST) in Big Bear Authors: Goode, P. R.; Cao, W. Bibcode: 2012ASPC..463..357G Altcode: The New Solar Telescope (NST) in Big Bear is the first facility-class solar telescope built in the US in a generation, and it has an off-axis design as is planned for the Advanced Technology Solar Telescope (ATST). The NST is in regular operation with adaptive optics (AO) correcting the light currently feeding photometric and near-IR polarimetric systems, as well as an imaging spectrograph. Here we show the high resolution capabilities of the NST. As well, we sketch our plans for, and reasoning behind the next generation NST instrumentation. Title: The 1.6 m New Solar Telescope (NST) in Big Bear Authors: Cao, W. Bibcode: 2012IAUSS...6E.202C Altcode: The 1.6 m clear aperture, off-axis New Solar Telescope (NST) is in regular operation in Big Bear Solar Observatory. The NST is the first facility-class solar telescope built in the U.S. in a generation. The NST provides high resolution and high sensitivity observations of the solar photosphere and chromosphere in the visible and near infrared (NIR). A high order adaptive optics system delivers corrected light to an ensemble of state-of-the-art scientific instruments in the coude laboratory including the Broad-band Filter Imagers (BFIs), NIR Imaging Spectro-polarimeter (NIRIS), Visible Imaging Spectro-polarimeter (VIS) and Fast Imaging Solar Spectrograph (FISS). Some early scientific results from the NST will be presented, followed by a progress report on NST instrument development projects, as well as upgrades to existing instruments. Title: The 1.6 m off-axis New Solar Telescope (NST) in Big Bear Authors: Goode, Philip R.; Cao, Wenda Bibcode: 2012SPIE.8444E..03G Altcode: The 1.6-m New Solar Telescope (NST) has been used to observe the Sun for more than three years with ever increasing capabilities as its commissioning phase winds down. The NST is the first facility-class solar telescope built in the U.S. in a generation, and it has an off-axis design as is planned for the 4 m Advanced Technology Solar Telescope. Lessons learned will be discussed. Current NST post-focus instrumentation includes adaptive optics (AO) feeding photometric and near-IR polarimetric sytems, as well as an imaging spectrograph. On-going instrumentation projects will be sketched, including Multi-Conjugate AO (MCAO), next generation (dual Fabry- Perot) visible light and near-IR polarimeters and a fully cryogenic spectrograph. Finally, recent observational results illustrating the high resolution capabilities of the NST will be shown. Title: Small Scale Field Emergence and Its Impact on Photospheric Granulation Authors: Yurchyshyn, V.; Ahn, K.; Abramenko, V.; Goode, P.; Cao, W. Bibcode: 2012arXiv1207.6418Y Altcode: We used photospheric intensity images and magnetic field measurements from the New Solar Telescope in Big Bear and Helioseismic Magnetic Imager on board Solar Dynamics Observatory (SDO) to study the the effect that the new small-scale emerging flux induces on solar granulation. We report that emerging flux appears to leave different types of footprint on solar granulation: i) diffuse irregular patches of increased brightness, ii) well defined filament-like structures and accompanied bright points, and iii) bright point-like features that appear inside granules. We suggest that the type of the footprint depends on the intensity of emerging fields. Stronger fields, emerging as a part of large magnetic structure, create on the solar surface a well defined filamentary pattern with bright points at the ends of the filaments, while weak turbulent fields are associated with bright patches inside the host granule. Title: Profiles of the daytime atmospheric turbulence above Big Bear solar observatory Authors: Kellerer, A.; Gorceix, N.; Marino, J.; Cao, W.; Goode, P. R. Bibcode: 2012A&A...542A...2K Altcode: Context. Space weather has become acutely critical for today's global communication networks. To understand its driving forces we need to observe the Sun with high angular-resolution, and within large fields-of-view, i.e. with multi-conjugate adaptive optics correction.
Aims: The design of a multi-conjugate adaptive optical system requires the knowledge of the altitude distribution of atmospheric turbulence. We have therefore measured daytime turbulence profiles above the New Solar Telescope (NST), on Big Bear Lake.
Methods: To this purpose, a wide-field wavefront sensor was installed behind the NST. The variation of the wavefront distortions with angular direction allows the reconstruction of the distribution of turbulence.
Results: The turbulence is found to have three origins: 1. a ground layer (<500 m) that contains 55-65% of the turbulence, 2. a boundary layer between 1-7 km comprises 30-40% of the turbulent energy, 3. and the remaining ~5% are generated in the tropopause, which is above 12 km in summer and between 8 and 12 km in winter.
Conclusions: A multi-conjugate adaptive optical system should thus aim at correcting the ground turbulence, the center of the boundary layer at roughly 3 km altitude and, eventually, the upper boundary layer around 6 km altitude. Title: Characteristic Size of Flare Kernels in the Visible and Near-infrared Continua Authors: Xu, Yan; Cao, Wenda; Jing, Ju; Wang, Haimin Bibcode: 2012ApJ...750L...7X Altcode: In this Letter, we present a new approach to estimate the formation height of visible and near-infrared emission of an X10 flare. The sizes of flare emission cores in three wavelengths are accurately measured during the peak of the flare. The source size is the largest in the G band at 4308 Å and shrinks toward longer wavelengths, namely the green continuum at 5200 Å and NIR at 15600 Å, where the emission is believed to originate from the deeper atmosphere. This size-wavelength variation is likely explained by the direct heating model as electrons need to move along converging field lines from the corona to the photosphere. Therefore, one can observe the smallest source, which in our case is 0farcs65 ± 0farcs02 in the bottom layer (represented by NIR), and observe relatively larger kernels in upper layers of 1farcs03 ± 0farcs14 and 1farcs96 ± 0farcs27, using the green continuum and G band, respectively. We then compare the source sizes with a simple magnetic geometry to derive the formation height of the white-light sources and magnetic pressure in different layers inside the flare loop. Title: Observation of Ultrafine Channels of Solar Corona Heating Authors: Ji, Haisheng; Cao, Wenda; Goode, Philip R. Bibcode: 2012ApJ...750L..25J Altcode: We report the first direct observations of dynamical events originating in the Sun's photosphere and subsequently lighting up the corona. Continuous small-scale, impulsive events have been tracked from their origin in the photosphere on through to their brightening of the local corona. We achieve this by combining high-resolution ground-based data from the 1.6 m aperture New Solar Telescope (NST) at Big Bear Solar Observatory (BBSO), and satellite data from the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO). The NST imaging observations in helium I 10830 Å reveal unexpected complexes of ultrafine, hot magnetic loops seen to be reaching from the photosphere to the base of the corona. Most of these ultrafine loops are characterized by an apparently constant, but surprisingly narrow diameter of about 100 km all along each loop, and the loops originate on the solar surface from intense, compact magnetic field elements. The NST observations detect the signature of upward injections of hot plasma that excite the ultrafine loops from the photosphere to the base of the corona. The ejecta have their individual footpoints in the intergranular lanes between the Sun's ubiquitous, convectively driven granules. In many cases, AIA/SDO detects cospatial and cotemporal brightenings in the overlying, million degree coronal loops in conjunction with the upward injections along the ultrafine loops. Segments of some of the more intense upward injections are seen as rapid blueshifted events in simultaneous Hα blue wing images observed at BBSO. In sum, the observations unambiguously show impulsive coronal heating events from upward energy flows originating from intergranular lanes on the solar surface accompanied by cospatial mass flows. Title: Calibration of data from InfraRed Imaging Magnetograph for the New Solar Telescope Authors: Ahn, Kwangsu; Cao, W.; Gorceix, N.; Goode, P. R. Bibcode: 2012AAS...22020616A Altcode: The InfraRed Imaging Magnetograph (IRIM) takes advantage of the high spatial resolution of New Solar Telescope (NST). It adopts a rotating birefringent polymer to modulate polarization signals and two Wollaston prisms as analyzer. Dual beam setup is used to minimize the effect of image motion caused by seeing. Its field of view is 50" x 25" and the wavelengths of operation are Fe I 15648 A and He I 10830 A. Due to the off-axis shape of the NST primary and secondary mirrors, multiple calibration techniques should be combined to reconstruct the original Stokes parameters. Here, we would like to introduce current status of our calibration efforts and discuss how IRIM data can be used for scientific purposes. Title: Characteristic Size Of Flare Kernels In Visible And The Near-infrared Continua Authors: Xu, Yan; Cao, W.; Jing, J.; Wang, H. Bibcode: 2012AAS...22020413X Altcode: In this study, we present a new approach to estimate the formation height of visible and the near-infrared emission during an X10 flare. The sizes of flare cores in three wavelengths are accurately measured during the peak time. The result shows that the source size is the largest in G-band at 4308 Å and shrinks towards longer wavelengths, namely the green continuum at 5200 Å and NIR at 15600 Å, where the emission is believed to originate from deeper atmosphere. This size-wavelength variation is likely explained by the direct heating model as electrons need to move along converging field lines. In this model, energetic electrons are confined by the magnetic field lines, which converge from the corona to the photosphere. Therefore one can observe the smallest source, which in our case is 0.65 ± 0".02 (radius by assuming a circular shape) in the bottom layer (represented by NIR) and observe relatively large kernels in upper layers of 1".03 ± 0".14 and 1".96 ± 0".27, using the green continuum and G-band respectively. We then compare the source sizes with a simple magnetic geometry to derived the formation height of the white-light sources and magnetic pressure in different layers inside the flare loop. Title: Origin of Rapid Blueshifted Events in Coronal Holes Authors: Yurchyshyn, Vasyl B.; Ahn, K.; Abramenko, V.; Goode, P.; Cao, W. Bibcode: 2012AAS...22042304Y Altcode: Clusters of photospheric bright points are surrounded by chromospheric rosette-like structures. These rosettes, when observed in the far off-band (-0.1nm) Halpha images often appear to consist of short living, narrow rapid blueshifted events (RBEs). RBEs, in turn, are thought to be disk counterparts of type II spicules (spicules II), detected in Hinode data, which may be playing play an important role in coronal heating since they are thought to supply mass to the solar corona. The search for the origin of type II spicules was one of the main focus of solar physics research in the recent years.

Here we present our findings on the possible driving mechanism of spicules II, which are based on high resolution photospheric, chromospheric and magnetic field data from the New Solar Telescope (NST) collected in a coronal hole. We report that the majority of RBEs, occurring around a network cluster, are associated with appearance of opposite polarity features within the unipolar cluster fields, suggesting that magnetic reconnection may be the driving mechanism. We will present these observations in details and discuss possible implications. Title: Observation of Hyperfine Channels of Solar Corona Heating Authors: Cao, Wenda; Ji, H.; Goode, P. R. Bibcode: 2012AAS...22042301C Altcode: We report here the first direct observations of dynamical events originating in the sun’s cool photosphere and subsequently lighting up the corona. Continuous impulsive events have been tracked from their origin in the photosphere on through to their brightening of the local corona. We achieve this by combining high resolution ground-based data from the 1.6 meter aperture New Solar Telescope (NST) at Big Bear Solar Observatory (BBSO),and satellite data from the Atmospheric Imaging Assembly (AIA) on-board the Solar Dynamics Observatory (SDO). The NST observations in a narrow band absorption line, Helium I 10830 Å, reveal unexpected complexes of hyperfine, hot magnetic loops seen to be reaching from the photosphere to the base of the corona. Most of these hyperfine loops are characterized by an apparently constant, but surprisingly narrow diameter of about 100 km all along each loop, and the loops originate on the solar surface from intense, small-scale magnetic field elements. The NST observations detect upward injections of hot plasma that excite the hyperfine loops from the photosphere to the base of the corona. The ejecta have their individual footpoints in the intergranular lanes between the sun’s ubiquitous, convectively driven granules. In many cases, AIA/SDO detects co-spatial and co-temporal brightenings in the overlying, million-degree coronal loops in conjunction with the upward injections along the hyperfine loops. Segments of some of the more intense upward injections are seen as rapid blue-shifted events in simultaneous Hα blue wing images observed at BBSO. In sum, the observations unambiguously show impulsive coronal heating events from upward energy flows originating from intergranular lanes on the solar surface accompanied by co-spatial mass flows. Title: Depth profiling of dopants implanted in Si using the synchrotron radiation based high-resolution grazing emission technique Authors: Kayser, Y.; Banaś, D.; Cao, W.; Dousse, J. -Cl.; Hoszowska, J.; Jagodziński, P.; Kavčič, M.; Kubala-Kukuś, A.; Nowak, S.; Pajek, M.; Szlachetko, J. Bibcode: 2012XRS....41...98K Altcode: No abstract at ADS Title: Properties of Umbral Dots as Measured from the New Solar Telescope Data and MHD Simulations Authors: Kilcik, A.; Yurchyshyn, V. B.; Rempel, M.; Abramenko, V.; Kitai, R.; Goode, P. R.; Cao, W.; Watanabe, H. Bibcode: 2012ApJ...745..163K Altcode: 2011arXiv1111.3997K We studied bright umbral dots (UDs) detected in a moderate size sunspot and compared their statistical properties to recent MHD models. The study is based on high-resolution data recorded by the New Solar Telescope at the Big Bear Solar Observatory and three-dimensional (3D) MHD simulations of sunspots. Observed UDs, living longer than 150 s, were detected and tracked in a 46 minute long data set, using an automatic detection code. A total of 1553 (620) UDs were detected in the photospheric (low chromospheric) data. Our main findings are (1) none of the analyzed UDs is precisely circular, (2) the diameter-intensity relationship only holds in bright umbral areas, and (3) UD velocities are inversely related to their lifetime. While nearly all photospheric UDs can be identified in the low chromospheric images, some small closely spaced UDs appear in the low chromosphere as a single cluster. Slow-moving and long-living UDs seem to exist in both the low chromosphere and photosphere, while fast-moving and short-living UDs are mainly detected in the photospheric images. Comparison to the 3D MHD simulations showed that both types of UDs display, on average, very similar statistical characteristics. However, (1) the average number of observed UDs per unit area is smaller than that of the model UDs, and (2) on average, the diameter of model UDs is slightly larger than that of observed ones. Title: Properties of Umbral Dots as Measured from the New Solar Telescope Data and MHD Simulations Authors: Yurchyshyn, V.; Kilcik, A.; Rempel, M.; Abramenko, V.; Kitai, R.; Goode, P. R.; Cao, W.; Watanabe, H. Bibcode: 2011sdmi.confE..86Y Altcode: We studied bright umbral dots (UDs) detected in the main sunspot of AR NOAA 11108 and compare their statistical properties to a state-of-the-art MHD model of a sunspot. The study is based on high resolution data recorded on September 20, 2010 by the New Solar Telescope (NST) at Big Bear Solar Observatory and 3D MHD simulations of sunspots. The 46 min data set included photospheric (0.3nm TiO filter centered at 705.7 nm) and chromospheric (0.025nm Hα Lyot filter) adaptive optics corrected and speckle reconstructed images. Bright UDs, living longer than 150 s, were detected and tracked using an automatic UD detection code. Total 1553 (620) UDs were detected in the photospheric (chromospheric) data. Our main findings are: i) none of the analyzed UDs is of an exact circular shape, ii) the diameter-intensity relationship only works for bright umbral areas, and iii) UD velocities inversely related to their life time. Comparison of photospheric and chromospheric data showed that nearly all photospheric UDs can be identified in the chromospheric images. However, it appears that some small closely spaced UDs appear in the chromospheric images as a single cluster, which may lead to the underestimation of the total number of detected chromospheric UDs. Also, while slow moving and long living UDs seem to exist in both chromosphere and photosphere, fast moving and short living ones are detected mainly in the photospheric images. Comparison of model and observed data shows that both types of UDs display very similar statistical characteristics. The main difference between parameters of model and observed UDs is that i) the average number of observed UDs per unit area is smaller than that of the model UDs, and ii) on average, the diameter of model UDs is slightly larger than that of observed ones. Title: High-resolution observations of the solar dynamics and magnetism Authors: Goode, Phil; Cao, Wenda; Yurchyshyn, Vasyl Bibcode: 2011sdmi.confE..28G Altcode: The NST is the first facility-class solar telescope built in the US in a generation. Images and movies illustrating the high resolution capabilities of the NST will be shown. In particular, high resolution NST observations reveal vortices in the granular field that are associated with newly discovered, but ubiquitous small-scale jets, which are much smaller-scale than Hinode type-II jets. NST observations have been used to probe the nature of the diffusion of magnetic bright points, which seems consistent with the operation of small-scale dynamos, while seeming to be sufficient on large-scales to support the Wang-Sheeley dynamo picture. Other recent NST results correlated with satellite observations will be shown and discussed. Title: Photospheric Signatures of Granular-scale Flux Emergence and Cancellation at the Penumbral Boundary Authors: Lim, Eun-Kyung; Yurchyshyn, Vasyl; Abramenko, Valentyna; Ahn, Kwangsu; Cao, Wenda; Goode, Philip Bibcode: 2011ApJ...740...82L Altcode: 2011arXiv1107.5254L We studied flux emergence events of sub-granular scale in a solar active region. The New Solar Telescope (NST) of the Big Bear Solar Observatory made it possible to clearly observe the photospheric signature of flux emergence with very high spatial (0farcs11 at 7057 Å) and temporal (15 s) resolution. From TiO observations with the pixel scale of 0farcs0375, we found several elongated granule-like features (GLFs) stretching from the penumbral filaments of a sunspot at a relatively high speed of over 4 km s-1. After a slender arched darkening appeared at the tip of a penumbral filament, a bright point (BP) developed and quickly moved away from the filament, forming and stretching a GLF. The size of a GLF was approximately 0farcs5 wide and 3'' long. The moving BP encountered nearby structures after several minutes of stretching, and the well-defined elongated shape of the GLF faded away. Magnetograms from the Solar Dynamics Observatory/Helioseismic and Magnetic Imager and NST/InfraRed Imaging Magnetograph revealed that those GLFs are photospheric indicators of small-scale flux emergence, and their disappearance is related to magnetic cancellation. From two well-observed events, we describe detailed development of the sub-structures of GLFs and different cancellation processes that each of the two GLFs underwent. Title: Umbral Dynamics in the Near-infrared Continuum Authors: Anđić, A.; Cao, W.; Goode, P. R. Bibcode: 2011ApJ...736...79A Altcode: 2011arXiv1105.1825A We detected peaks of oscillatory power at 3 and ~6.5 minutes in the umbra of the central sunspot of the active region NOAA AR 10707 in data obtained in the near-infrared (NIR) continuum at 1565.7 nm. The NIR data set captured umbral dynamics around 50 km below the τ500 = 1 level. The umbra does not oscillate as a whole, but rather in distinct parts that are distributed over the umbral surface. The most powerful oscillations, close to a period of ~6.5, do not propagate upward. We noted a plethora of large umbral dots (UDs) that persisted for >=30 minutes and stayed in the same locations. The peaks of oscillatory power above the detected UDs are located at 3 and 5 minute oscillations, but are very weak in comparison with the oscillations of ~6.5 minutes. Title: Near-infrared Imaging Spectropolarimeter For The Nst Authors: Cao, Wenda; Ahn, K.; Gorceix, N.; Shumko, S.; Coulter, R.; Goode, P. Bibcode: 2011SPD....42.0606C Altcode: 2011BAAS..43S.0606C The NST Near-Infrared Imaging Spectropolarimeter is one of the first imaging solar spectro-polarimeters working in the near infrared (NIR). It has been installed and commissioned in the Coude Lab of the 1.6-meter NST at Big Bear Solar Observatory (BBSO). This innovative system, which includes a 2.5 nm interference filter, a unique 0.25 nm birefringent Lyot filter, and a Fabry-Perot etalon, is capable of providing a bandpass as low as 0.01 nm over a field-of-view (FOV) of 50" in a telecentric configuration. An NIR waveplate rotates ahead of M3 in the NST as the polarimeter modulator, and ahead of it a calibration unit is located to reduce polarization cross-talk induced by subsequent oblique mirrors. Dual-beam differential polarimetry is employed to minimize seeing-induced spurious polarization. Based on the unique advantages in IR window, the very capable NST with adaptive optics, it will provide unprecedented solar spectro-polarimetry with high Zeeman sensitivity (10-3Ic), high spatial resolution (0.2"), and high cadence (15s). In this presentation, we discuss the design, fabrication, and calibration, as well as showing the results of the first light observations. Title: Sunspot Umbral Dots Detected with the New Solar Telescope Authors: Kilcik, Ali; Yurchyshyn, V.; Abramenko, V.; Goode, P.; Cao, W. Bibcode: 2011SPD....42.1901K Altcode: 2011BAAS..43S.1901K We present a study of bright umbral dots detected inside a large sunspot of NOAA AR 11108. This study is based on high resolution data recorded on September 20, 2010 with the New Solar Telescope (NST) at Big Bear Solar Observatory. The data set, spanning 46 min, consists of a total of 184 adaptive optics corrected and speckle reconstructed images obtained with a 0.3 nm passband TiO filter centered on the 705.7 nm spectral line. The image cadence is 15 s and the pixel size of 0.0375 arcsec.

Bright umbral dots (UDs) were detected and tracked using an automatic routine. Here we only focus on long living UDs (>150 s in life time) and a total of 513 such features were detected during the observed period. We found that the average lifetime of a UD is 7.4 min and an average size is 0.34 arcsec. There is a tendency for larger UDs to be brighter (and more circular). Many UDs are not of circular shape. We will also present probability distribution of various physical parameters and compare the results to similar earlier studies. Title: Active Region High Velocity Events Observed by Fast Imaging Solar Spectrograph on the NST Authors: Ahn, Kwangsu; Chae, J.; Nah, J.; Park, H.; Jang, B.; Yang, H.; Park, Y.; Cao, W.; Goode, P. R. Bibcode: 2011SPD....42.1904A Altcode: 2011BAAS..43S.1904A The Fast Imaging Solar Spectrograph (FISS) is the only spectrograph-based instrument on the NST that is currently operational. With a high spectral resolution of 1.4 x 105 and simultaneous dual spectral band imaging, this instrument can accurately determine the physical parameters of chromospheric features --- filaments, jets and so on. Initial observations captured several peculiar dynamic events that showed high line-of-sight velocities of the order of 20 km s-1 in the vicinity of sunspots. We expect that FISS will provide a better understanding of the physics in the chromosphere with the aid of the unprecedentedly high spatial resolution of NST. Title: Response of Granulation to Small-scale Bright Features in the Quiet Sun Authors: Anđić, A.; Chae, J.; Goode, P. R.; Cao, W.; Ahn, K.; Yurchyshyn, V.; Abramenko, V. Bibcode: 2011ApJ...731...29A Altcode: 2011arXiv1102.3404A We detected 2.8 bright points (BPs) per Mm2 in the quiet Sun with the New Solar Telescope at Big Bear Solar Observatory, using the TiO 705.68 nm spectral line at an angular resolution ~0farcs1 to obtain a 30 minute data sequence. Some BPs formed knots that were stable in time and influenced the properties of the granulation pattern around them. The observed granulation pattern within ~3'' of knots presents smaller granules than those observed in a normal granulation pattern, i.e., around the knots a suppressed convection is detected. Observed BPs covered ~5% of the solar surface and were not homogeneously distributed. BPs had an average size of 0farcs22, they were detectable for 4.28 minutes on average, and had an averaged contrast of 0.1% in the deep red TiO spectral line. Title: The New Solar Telescope in Big Bear: Polarimetry II Authors: Cao, W.; Ahn, K.; Goode, P. R.; Shumko, S.; Gorceix, N.; Coulter, R. Bibcode: 2011ASPC..437..345C Altcode: IRIM (Infrared Imaging Magnetograph) is one of the first imaging solar spectro-polarimeters working in the near infrared (NIR). IRIM is being installed and commissioned in the Coudé Lab of the 1.6-meter New Solar Telescope (NST) at Big Bear Solar Observatory (BBSO). This innovative system, which includes a 2.5 nm interference filter, a unique 0.25 nm birefringent Lyot filter, and a Fabry-Pérot etalon, is capable of providing a bandpass as low as 0.01 nm over a field-of-view of 50" in a telecentric configuration. An NIR waveplate rotates ahead of M3 in the NST as the polarimeter modulator, and ahead of it locates a calibration unit to reduce polarization cross-talk induced by subsequent oblique mirrors. Dual-beam differential polarimetry is employed to minimize seeing-induced spurious polarization. Based on the unique advantages in IR window, the very capable NST with adaptive optics, IRIM will provide unprecedented solar spectro-polarimetry with high Zeeman sensitivity (10-3Ic), high spatial resolution (0.2"), and high cadence (15 s). In this paper, we discuss the design, fabrication, and calibration of IRIM, as well as the results of the first light observations. Title: Time Distributions of Large and Small Sunspot Groups Over Four Solar Cycles Authors: Kilcik, A.; Yurchyshyn, V. B.; Abramenko, V.; Goode, P. R.; Ozguc, A.; Rozelot, J. P.; Cao, W. Bibcode: 2011ApJ...731...30K Altcode: 2011arXiv1111.3999K Here we analyze solar activity by focusing on time variations of the number of sunspot groups (SGs) as a function of their modified Zurich class. We analyzed data for solar cycles 20-23 by using Rome (cycles 20 and 21) and Learmonth Solar Observatory (cycles 22 and 23) SG numbers. All SGs recorded during these time intervals were separated into two groups. The first group includes small SGs (A, B, C, H, and J classes by Zurich classification), and the second group consists of large SGs (D, E, F, and G classes). We then calculated small and large SG numbers from their daily mean numbers as observed on the solar disk during a given month. We report that the time variations of small and large SG numbers are asymmetric except for solar cycle 22. In general, large SG numbers appear to reach their maximum in the middle of the solar cycle (phases 0.45-0.5), while the international sunspot numbers and the small SG numbers generally peak much earlier (solar cycle phases 0.29-0.35). Moreover, the 10.7 cm solar radio flux, the facular area, and the maximum coronal mass ejection speed show better agreement with the large SG numbers than they do with the small SG numbers. Our results suggest that the large SG numbers are more likely to shed light on solar activity and its geophysical implications. Our findings may also influence our understanding of long-term variations of the total solar irradiance, which is thought to be an important factor in the Sun-Earth climate relationship. Title: The New Solar Telescope in Big Bear: Polarimetry I Authors: Goode, P. R.; Cao, W.; Ahn, K.; Gorceix, N.; Coulter, R. Bibcode: 2011ASPC..437..341G Altcode: We present here the near-term polarimetry plans for the 1.6 m clear aperture, off-axis telescope in Big Bear. The first scientific data were taken in the Summer of 2009 at the Nasmyth focus, and first observations corrected by adaptive optics were taken in the Summer of 2010. The first polarimetry for this telescope will be done in the near infrared at 1.56 μm, which is close to the photospheric opacity minimum. We show and explain reasons for the general layout of the polarimetric hardware for the telescope. Title: Hard X-ray Source Distributions on EUV Bright Kernels in a Solar Flare Authors: Ning, Zongjun; Cao, Wenda Bibcode: 2011SoPh..269..283N Altcode: 2010SoPh..tmp..247N We explore the hard X-ray source distributions of an C1.1 flare occurred on 14 December 2007. Both Hinode/EIS and RHESSI observations are used. One of EIS rasters perfectly covers the double hard X-ray footpoints, where the EUV emission appears strong from the cool line of He II (log T=4.7) to the hot line of Fe XVI (log T=6.4). We analyze RHESSI X-ray images at different energies and different times before the hard X-ray maximum. The results show a similar topology for the time-dependent source distribution (i.e. at 14:14:35 UT) as that for energy-dependent source distribution (i.e. at a given energy band of 6 - 9 keV) overlapped on EUV bright kernels, which seems to be consistent with the evaporation model. Title: Development of the Fast Imaging Solar Spectrograph for 1.6 m New Solar Telescope Authors: Nah, Ja-Kyoung; Chae, Jong-Chul; Park, Young-Deuk; Park, Hyung-Min; Jang, Bi-Ho; Ahn, Kwang-Su; Yang, Hee-Su; Cho, Kyung-Suk; Kim, Yeon-Han; Kim, Kwang-Dong; Cao, Wenda; Gorceix, Nicolas; Goode, Philip. R. Bibcode: 2011PKAS...26...45N Altcode: No abstract at ADS Title: Measurement of Sky Brightness and Suppression of Scattering in Sky Brightness Monitor Authors: Liu, N. P.; Liu, Y.; Shen, Y. D.; Zhang, X. F.; Cao, W. D.; Arnaud, J. Bibcode: 2011AcASn..52..160L Altcode: A modern Sky Brightness Monitor (SBM) was developed for the site survey in West China for the future large solar equipment installation. The performance of this new SBM was tested in the recent preliminary experiments. A lot of sky brightness data had been obtained at a few sites in Yunnan. The blue channel result shows that the sky brightness near the noon time on Jiaozi Snow Mountain is as low as a few millionths of the solar center intensity, indicating the low scattering level inside our SBM instrument. The scattering is mainly from two parts: the diffraction rings from the occulter edges, distributed in the inner field of view but outside the occulter region containing the ND4 filter; the diffraction from the baffle rings, distributed in the extreme edges of the field of view. To suppress the scattering of the latter part, experiments with different aperture sizes of baffle rings are made. The result shows that, by mounting new baffle rings with proper aperture size into the SBM telescope tube, diffraction in the extreme edges of the field of view can be effectively reduced. Title: Ferroelectrics, Thermodynamic Phenomenology of Authors: Cao, W. Bibcode: 2011emst.book.3074C Altcode: Phenomenological theories of ferroelectrics, such as the Landau-Ginzburg-Devonshire type models, are based on thermodynamic principles and the structural symmetry relationship between the paraelectric and ferroelectric phases. The primary order parameter for describing a ferroelectric system is the electrical polarization, and the elastic strain, as a secondary order parameter, almost always plays a key role in the phase transition, domain formation, and other related physical phenomena. Phenomenological theories are field theories; however, they do reflect the discrete atomic displacement patterns and the symmetry changes in the unit cell associated with the ferroelectric phase transition. <ce:anchor Title: Chromospheric Signatures of Small-scale Flux Emergence as Observed with New Solar Telescope and Hinode Instruments Authors: Yurchyshyn, V. B.; Goode, P. R.; Abramenko, V. I.; Chae, J.; Cao, W.; Andic, A.; Ahn, K. Bibcode: 2010ApJ...722.1970Y Altcode: 2011arXiv1102.1034Y With the ever-increasing influx of high-resolution images of the solar surface obtained at a multitude of wavelengths, various processes occurring at small spatial scales have become a greater focus of our attention. Complex small-scale magnetic fields have been reported that appear to have enough stored energy to heat the chromosphere. While significant progress has been made in understanding small-scale phenomena, many specifics remain elusive. We present here a detailed study of a single event of disappearance of a magnetic dipole and associated chromospheric activity. Based on New Solar Telescope Hα data and Hinode photospheric line-of-sight magnetograms and Ca II H images, we report the following. (1) Our analysis indicates that even very small dipoles (elements separated by about 0farcs5 or less) may reach the chromosphere and trigger non-negligible chromospheric activity. (2) Careful consideration of the magnetic environment where the new flux is deposited may shed light on the details of magnetic flux removal from the solar surface. We argue that the apparent collision and disappearance of two opposite polarity elements may not necessarily indicate their cancellation (i.e., reconnection, emergence of a "U" tube, or submergence of Ω loops). In our case, the magnetic dipole disappeared by reconnecting with overlying large-scale inclined plage fields. (3) Bright points (BPs) seen in off-band Hα images are very well correlated with the Ca II H BPs, which in turn are cospatial with G-band BPs. We further speculate that, in general, Hα BPs are expected to be cospatial with photospheric BPs; however, a direct comparison is needed to refine their relationship. Title: Patterns of Flows in an Intermediate Prominence Observed by Hinode Authors: Ahn, Kwangsu; Chae, Jongchul; Cao, Wenda; Goode, Philip R. Bibcode: 2010ApJ...721...74A Altcode: The investigation of plasma flows in filaments/prominences gives us clues to understanding their magnetic structures. We studied the patterns of flows in an intermediate prominence observed by Hinode/SOT. By examining a time series of Hα images and Ca II H images, we have found horizontal flows in the spine and vertical flows in the barb. Both of these flows have a characteristic speed of 10-20 km s-1. The horizontal flows displayed counterstreaming. Our detailed investigation revealed that most of the moving fragments in fact reversed direction at the end point of the spine near a footpoint close to the associated active region. These returning flows may be one possible explanation of the well-known counterstreaming flows in prominences. In contrast, we have found vertical flows—downward and upward—in the barb. Most of the horizontal flows in the spine seem to switch into vertical flows when they approach the barb, and vice versa. We propose that the net force resulting from a small deviation from magnetohydrostatic equilibrium, where magnetic fields are predominantly horizontal, may drive these patterns of flow. In the prominence studied here, the supposed magnetohydrostatic configuration is characterized by magnetic field lines sagging with angles of 13° and 39° in the spine and the barb, respectively. Title: Evidence of Filament Upflows Originating from Intensity Oscillations on the Solar Surface Authors: Cao, Wenda; Ning, Zongjun; Goode, Philip R.; Yurchyshyn, Vasyl; Ji, Haisheng Bibcode: 2010ApJ...719L..95C Altcode: A filament footpoint rooted in an active region (NOAA 11032) was well observed for about 78 minutes with the 1.6 m New Solar Telescope at the Big Bear Solar Observatory on 2009 November 18 in Hα ±0.75 Å. This data set had high cadence (~15 s) and high spatial resolution (~0farcs1) and offered a unique opportunity to study filament dynamics. As in previous findings from space observations, several dark intermittent upflows were identified, and they behave in groups at isolated locations along the filament. However, we have two new findings. First, we find that the dark upflows propagating along the filament channel are strongly associated with the intensity oscillations on the solar surface around the filament footpoints. The upflows start at the same time as the peak in the oscillations, illustrating that the upflow velocities are well correlated with the oscillations. Second, the intensity of one of the seven upflows detected in our data set exhibits a clear periodicity when the upflow propagates along the filament. The periods gradually vary from ~10 to ~5 minutes. Our results give observational clues on the driving mechanism of the upflows in the filament. Title: Investigation of Chromospheric Evaporation in a Neupert-type Solar Flare Authors: Ning, Zongjun; Cao, Wenda Bibcode: 2010ApJ...717.1232N Altcode: The Neupert effect implies a flare model in which the hard X-rays (HXRs) are produced by energetic electrons via electron-ion bremsstrahlung as they lose their energies in the chromosphere, while the soft X-rays (SXRs) are produced by thermal bremsstrahlung from "chromospheric evaporation" due to plasma being heated by those same electrons. Based on this concept, we investigate the evidence for chromospheric evaporation in a Neupert-type flare on 2004 October 30. First, we demonstrate that this event is consistent with the Neupert effect. Using the RHESSI data, both thermal and nonthermal energies are derived after the onset of this flare. The high correlation between the derivative of the SXRs and HXRs and between the derivative of the thermal energy and nonthermal energy indicates that the 2004 October 30 flare is a Neupert-type event. Second, chromospheric evaporation is necessarily expected during the flare's rising phase. We analyze RHESSI images at different energies and different times around the flare maximum. The HXR emission tends to move the footpoints close to each other, finally merging them into a single source with the same position as the loop-top source. When the projection effect (due to this event being near the disk center) is taken into account, this fact can be regarded as the signature of chromospheric evaporation in the X-ray observations. RHESSI observations show three kinds of evidence that are consistent with the evaporation model. First, at a given instant, the higher energy X-rays originate from the deeper layers of the atmosphere or further away from the loop top. Second, in a given energy band, i.e., at 20-30 keV, the earlier X-rays originate from the deeper layers or further away from the loop top. Third, the X-ray footpoint sources at higher energies disappear at later times. Based on these characteristics, chromospheric evaporation took about 100 s for the 2004 October 30 flare. X-rays at all energy bands do not show evidence of evaporation probably because measurements are the most sensitive only between 12 and 30 keV. After measuring the source scale as a function of time, we roughly estimate the shrinkage velocities at different energies, for instance, 238 km s-1 for 12-15 keV, 285 km s-1 for 15-20 keV, and 846 km s-1 for 20-30 keV. If the evaporation processes primarily contribute to the source shrinkage, these values are considered as the evaporation velocities, indicating that the evaporation flow would be faster during the latter part of flare. Title: Oscillatory Behavior in the Quiet Sun Observed with the New Solar Telescope Authors: Anđić, A.; Goode, P. R.; Chae, J.; Cao, W.; Ahn, K.; Yurchyshyn, V.; Abramenko, V. Bibcode: 2010ApJ...717L..79A Altcode: 2010arXiv1007.0272A Surface photometry of the quiet Sun has achieved an angular resolution of 0farcs1 with the New Solar Telescope at Big Bear Solar Observatory, revealing that a disproportionate fraction of the oscillatory events appear above observed bright point-like structures. During the tracking of these structures, we noted that the more powerful oscillatory events are cospatial with them, indicating that observed flux tubes may be the source of many observed oscillatory events. Title: Repackaging and characterizing of a HgCdTe CMOS infrared camera for the New Solar Telescope Authors: Cao, Wenda; Coulter, Roy; Gorceix, Nicolas; Goode, Philip R. Bibcode: 2010SPIE.7742E..20C Altcode: 2010SPIE.7742E..55C The 1.6-meter New Solar Telescope (NST) is currently the world's largest aperture solar telescope. The NST is newly built at Big Bear Solar Observatory (BBSO). Among other instruments, the NST is equipped with several focal plane instruments operating in the near infrared (NIR). In order to satisfy the diverse observational requirements of these scientific instruments, a 1024 × 1024 HgCdTe TCM8600 CMOS camera manufactured by Rockwell Scientific Company has been repackaged and upgraded at Infrared Laboratories Inc. A new ND-5 dewar was designed to house the TCM8600 array with a low background filter wheel, inverted operation and at least 12 hours of hold time between fills. The repackaged camera will be used for high-resolution NIR photometry at the NST Nasmyth focus on the telescope and high-precision NIR spectro-polarimetry in the NST Coudé Lab below. In March 2010, this repackaged camera was characterized in the Coudé Lab at BBSO. This paper presents the design of new dewar, the detailed process of repackaging and characterizing the camera, and a series of test results. Title: Investigation of the Neupert Effect in the Various Intervals of Solar Flares Authors: Ning, Zongjun; Cao, Wenda Bibcode: 2010SoPh..264..329N Altcode: 2010SoPh..tmp..124N; 2010SoPh..tmp..112N The Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) gives us a chance to investigate the theoretical Neupert effect using the correlation between the thermal-energy derivative and the nonthermal energy, or the thermal energy and the integral nonthermal energy. Based on this concept, we analyze four M-class RHESSI flares on 13 November 2003, 4 November 2004, 3 and 25 August 2005. According to the evolution of the temperature [T], emission measure [EM], and thermal energy [Eth], each event is divided into three phases during the nonthermal-energy input [\frac {dE_{nth}}{dt} in the units of erg s−1]. Phase 1 is identified as the interval before the temperature maximum, while after the thermal-energy maximum is phase 3, between them is phase 2. We find that these four flares show the Neupert effect in phase 1, but not in phase 3. The Neupert effect still works well in the second phase, although the cooling becomes slightly important. We define the parameter μ in the relation of dE_{th}/dt=μdE_{nth}(t)/dt or E_{th}(t0)=μ\int0^{t0}dE_{nth}(t)/dt dt when the cooling is ignored in phase 1. Considering the uncertainties in estimating the energy from the observations, it is not possible to precisely determine the fraction of the known energy in the nonthermal electrons transformed into the thermal energy of the hottest plasma observed by RHESSI. After a rough estimate of the flare volume and the assumption of the filling factor, we investigate the parameter μ in these four events. Its value ranges from 0.02 to 0.20, indicating that a small fraction (2% - 20%) of the nonthermal energy can be efficiently transformed into thermal energy, which is traced by the soft X-ray emission, and the bulk of the energy is lost possibly due to cooling. Title: Nasmyth focus instrumentation of the New Solar Telescope at Big Bear Solar Observatory Authors: Cao, Wenda; Gorceix, Nicolas; Coulter, Roy; Wöger, Friedrich; Ahn, Kwangsu; Shumko, Sergiy; Varsik, John; Coulter, Aaron; Goode, Philip R. Bibcode: 2010SPIE.7735E..5VC Altcode: 2010SPIE.7735E.194C The largest solar telescope, the 1.6-m New Solar Telescope (NST) has been installed and is being commissioned at Big Bear Solar Observatory (BBSO). It has an off-axis Gregorian configuration with a focal ratio of F/52. Early in 2009, first light scientific observations were successfully made at the Nasmyth focus, which is located on the east side of the telescope structure. As the first available scientific instruments for routine observation, Nasmyth focus instrumentation (NFI) consists of several filtergraphs offering high spatial resolution photometry in G-band 430 nm, Ha 656 nm, TiO 706 nm, and covering the near infrared 1083 nm, 1.6 μm, and 2.2 μm. With the assistance of a local correlation tracker system, diffraction limited images were obtained frequently over a field-of-view of 70 by 70 after processed using a post-facto speckle reconstruction algorithm. These data sets not only serve for scientific analysis with an unprecedented spatial resolution, but also provide engineering feedback to the NST operation, maintenance and optimization. This paper reports on the design and the implementation of NFI in detail. First light scientific observations are presented and discussed. Title: First light of the 1.6 meter off-axis New Solar Telescope at Big Bear Solar Observatory Authors: Cao, Wenda; Gorceix, Nicolas; Coulter, Roy; Coulter, Aaron; Goode, Philip R. Bibcode: 2010SPIE.7733E..30C Altcode: 2010SPIE.7733E..93C New Jersey Institute of Technology, in collaboration with the University of Hawaii and the Korea Astronomy & Space Science Institute, has successfully developed and installed a 1.6 m clear aperture, off-axis New Solar Telescope (NST) at the Big Bear Solar Observatory. The NST will be the largest aperture solar telescope in the world until the 4 m Advanced Technology Solar Telescope (ATST) and 4 m European Solar Telescope (EST) begin operation in the next decade. Meanwhile, the NST will be the largest off-axis telescope before the 8.4 m segmented Giant Magellan Telescope (GMT) comes on-line. The NST is configured as an off-axis Gregorian system consisting of a parabolic primary, prime focus field stop and heat reflector, elliptical secondary and diagonal flats. The primary mirror is made of Zerodur from Schott and figured to a final residual error of 16 nm rms by Steward Observatory Mirror Lab. The final focal ratio is f/52. The 180 circular opening in the field stop defines the maximal square field-of-view. The working wavelength range will cover 0.4 to 1.7 μm in the Coud´e Lab two floors beneath the telescope, and all wavelengths including far infrared at the Nasmyth focus on an optical bench attached to the side of the telescope structure. First-light scientific observations have been attained at the Nasmyth focus and in the Coud´e Lab. This paper presents a detailed description of installation and alignment of the NST. First-light observational results are also shown to demonstrate the validity of the NST optical alignment. Title: High resolution observations of white-light emissions from the opacity minimum during an X-class flare Authors: Xu, Y.; Cao, W.; Jing, J.; Wang, H. Bibcode: 2010AN....331..596X Altcode: Using high cadence, high resolution near infrared (NIR) observations of the X10 white-light flare (WLF) on 2003 October 29, we investigated the evolution of the core-halo structure of white-light emission during the two-second period flare peak. We found that size and intensity of the halo remained almost constant in the range of 10 Mm2. However, the core area was very compact and expanded rapidly from about 1 Mm2 to 4 Mm2. At the same time, the total emission of the core increased nearly twenty times. This distinct behavior indicates that different heating mechanisms might be responsible for core and halo emissions. In addition to the temporal analysis, we compared the intensity enhancements of the flare core and halo. The result shows that the halo contrast increased by about 8% compared to the flare-quiet region, which could be explained by a combination of direct-heating and backwarming models. Title: The NST: First results and some lessons for ATST and EST Authors: Goode, P. R.; Coulter, R.; Gorceix, N.; Yurchyshyn, V.; Cao, W. Bibcode: 2010AN....331..620G Altcode: In January 2009, first light observations with the NST (New Solar Telescope) in Big Bear Solar Observatory (BBSO) were made. NST has a 1.7 m primary with a 1.6 m clear aperture. First observational results in TiO and Hα are shown and discussed. The NST primary mirror is the most aspheric telescope mirror deployed to date. The NST is early in its commissioning, and the plans for this phase will be sketched. Lessons learned in building and implementing the NST are germane for the ATST and EST telescopes and will be discussed. The NST has an off-axis Gregorian configuration consisting of a parabolic primary, heat-stop, elliptical secondary and diagonal flats. The focal ratio of the primary mirror is f/2.4. The working wavelength range covers from 0.4 to 1.7 μm in the Coudé Lab beneath the telescope and all wavelengths including the far infrared at the Nasmyth focus on the dome floor. Title: Scientific instrumentation for the 1.6 m New Solar Telescope in Big Bear Authors: Cao, W.; Gorceix, N.; Coulter, R.; Ahn, K.; Rimmele, T. R.; Goode, P. R. Bibcode: 2010AN....331..636C Altcode: The NST (New Solar Telescope), a 1.6 m clear aperture, off-axis telescope, is in its commissioning phase at Big Bear Solar Observatory (BBSO). It will be the most capable, largest aperture solar telescope in the US until the 4 m ATST (Advanced Technology Solar Telescope) comes on-line late in the next decade. The NST will be outfitted with state-of-the-art scientific instruments at the Nasmyth focus on the telescope floor and in the Coudé Lab beneath the telescope. At the Nasmyth focus, several filtergraphs already in routine operation have offered high spatial resolution photometry in TiO 706 nm, H\alpha 656 nm, G-band 430 nm and the near infrared (NIR), with the aid of a correlation tracker and image reconstruction system. Also, a Cryogenic Infrared Spectrograph (CYRA) is being developed to supply high signal-to-noise-ratio spectrometry and polarimetry spanning 1.0 to 5.0 μm. The Coudé Lab instrumentation will include Adaptive Optics (AO), InfraRed Imaging Magnetograph (IRIM), Visible Imaging Magnetograph (VIM), and Fast Imaging Solar Spectrograph (FISS). A 308 sub-aperture (349-actuator deformable mirror) AO system will enable nearly diffraction limited observations over the NST's principal operating wavelengths from 0.4 μm through 1.7 μm. IRIM and VIM are Fabry-Pérot based narrow-band tunable filters, which provide high resolution two-dimensional spectroscopic and polarimetric imaging in the NIR and visible respectively. FISS is a collaboration between BBSO and Seoul National University focussing on chromosphere dynamics. This paper reports the up-to-date progress on these instruments including an overview of each instrument and details of the current state of design, integration, calibration and setup/testing on the NST. Title: Highest Resolution Observations of the Quietest Sun Authors: Goode, Philip R.; Yurchyshyn, Vasyl; Cao, Wenda; Abramenko, Valentyna; Andic, Aleksandra; Ahn, Kwangsu; Chae, Jongchul Bibcode: 2010ApJ...714L..31G Altcode: Highest resolution observations made with the new 1.6 m aperture solar telescope in Big Bear Solar Observatory during this time of historic inactivity on the Sun reveal new insights into the small-scale dynamics of the Sun's photosphere. The telescope's unprecedented resolution enabled us to observe that the smallest scale photospheric magnetic field seems to come in isolated points in the dark intergranular lanes, rather than the predicted continuous sheets confined to the lanes, and the unexpected longevity of the bright points implies a deeper anchoring than predicted. Further, we demonstrated for the first time that the photospheric plasma motion and magnetic fields are in equipartition over a wide dynamic range, and both cascade energy to ever-smaller scales according to classical Kolmogorov turbulence theory. Finally, we discovered tiny jet-like features originating in the dark lanes that surround the ubiquitous granules that characterize the solar surface. Title: New Solar Telescope Observations of Magnetic Reconnection Occurring in the Chromosphere of the Quiet Sun Authors: Chae, Jongchul; Goode, P. R.; Ahn, K.; Yurchysyn, V.; Abramenko, V.; Andic, A.; Cao, W.; Park, Y. D. Bibcode: 2010ApJ...713L...6C Altcode: Magnetic reconnection is a process in which field-line connectivity changes in a magnetized plasma. On the solar surface, it often occurs with the cancellation of two magnetic fragments of opposite polarity. Using the 1.6 m New Solar Telescope, we observed the morphology and dynamics of plasma visible in the Hα line, which is associated with a canceling magnetic feature (CMF) in the quiet Sun. The region can be divided into four magnetic domains: two pre-reconnection and two post-reconnection. In one post-reconnection domain, a small cloud erupted, with a plane-of-sky speed of 10 km s-1, while in the other one, brightening began at points and then tiny bright loops appeared and subsequently shrank. These features support the notion that magnetic reconnection taking place in the chromosphere is responsible for CMFs. Title: Dual-Stage Reconnection During Solar Flares Observed in Hard X-ray Authors: Xu, Yan; Jing, Ju; Cao, Wenda; Wang, Haimin Bibcode: 2010ApJ...709L.142X Altcode: In this Letter, we present hard X-ray (HXR) observation by the Reuven Ramaty High Energy Solar Spectroscopic Imager of the 2003 October 29 X10 flare. Two pairs of HXR conjugate footpoints have been identified during the early impulsive phase. This geometric configuration is very much in the manner predicted by the "tether-cutting" scenario first proposed by Moore & Roumeliotis. The HXR light curves show that the outer pair of footpoints disappeared much faster than the other pair. This temporal behavior further confirms that this event is a good example of the "tether-cutting" model. In addition, we reconstructed a three-dimensional magnetic field based on the nonlinear force-free extrapolation and found that each pair of HXR footpoints were indeed linked by corresponding magnetic field lines. Title: Scientific Instruments of 1.6 m New Solar Telescope in Big Bear Authors: Cao, W. Bibcode: 2009AGUFMSH51A1261C Altcode: The NST (New Solar Telescope) is in its commissioning phase at Big Bear Solar Observatory (BBSO). It will be the most capable, largest aperture solar telescope in the US until the 4 m ATST (Advanced Technology Solar Telescope) comes on-line in the middle of the next decade. The NST will be outfitted with state-of-the-art post-focus instrumentations at the Nasmyth focus on the dome floor and in the Coude Lab beneath the telescope. At the Nasmyth focus, several filter-based systems already in routine operation offer high spatial resolution photometry in TiO 704 nm, Hα 656 nm, G-band 430 nm and near infrared 1.56 μm & 2.2 μm, with the assistance of local correlation tracking and image reconstruction. As well, a Cryogenic InfraRed Spectrograph (CIRS) is being developed to supply high signal-to-noise-ratio spectrometry and polarimetry spanning 1.0 to 5.0 μm. The Coudé-lab instrumentations will include Adaptive Optics system (AO), InfraRed Imaging Magnetograph (IRIM), Visible Imaging Magnetograph (VIM), Real-time Image Reconstruction System (RIRS), and Fast Imaging Solar Spectrograph (FISS) -- most of these instruments operated on the old 0.6 m BBSO telescope. AO is being upgraded to a 308 sub-aperture (349-actuator Deformable Mirror) AO system that will enable diffraction limited observations over the NST's principal operating wavelengths from 0.4 through 1.7 μm. IRIM and VIM are Fabry-Pérot based narrow-band tunable filter, which provide high resolution two-dimensional spectroscopic and polarimetric imaging in the near infrared and visible respectively. Using a 32-node parallel computing system, RIRS is capable of performing real-time image reconstruction with one image every minute. FISS is a collaboration between BBSO and Seoul National University to focus on chromosphere dynamics. Key tasks including optical design, hardware/software integration and subsequent setup/testing on the NST, will be presented here. Some preliminary observation results in the near infrared will be shown. Title: A LATE BRITTLE COMPONENT OF MOTION WITHIN THE DUCTILE EASTERN SIERRA CREST SHEAR ZONE (ESCSZ) ALONG THE EASTERN BOUNDARY OF THE TOLUMNE BATHOLITH IN THE SADDLEBAG LAKE, CA AREA. WHITESIDES, Andrew1, ENRIQUEZ, Marcus2 , HARDY, Jill1 , EHRET, Philip1, IANNONE, Monika1, CULBERT, Kristan1 GROSS, Ben3, LODEWYK, Jessica3, CAO, Wenrong1 , ZHANG, Tao1, MEMETI, Valbone3, PATERSON, Scott1 SCHMIDT, Keegan4. (1) Department of Earth Sciences, University of Southern California, Los Angeles, CA 90089-0740, awhitesi@usc.edu , (2) Department of Geological Sciences, Cal State L.A., 5151 State University Drive, Los Angeles, CA 90032, (3) Department of Earth and Planetary Sciences, Washington University, Campus Box 1169, 1 Brookings Dr, Saint Louis, MO, 63130, (4) Division of Natural Science and Mathematics, Lewis-Clark State College, 500 8th Ave., Lewiston, ID 83501 Authors: Whitesides, A. S.; Enriquez, M.; Hardy, J.; Ehret, P.; Iannone, M.; Culbert, K. N.; Gross, M. B.; Lodewyk, J.; Cao, W.; Zhang, T.; Memeti, V.; Paterson, S. R.; Schmidt, K. L. Bibcode: 2009AGUFM.T21D1862W Altcode: During mapping (by the Undergraduate Team Research program, University of Southern California) in the Saddlebag Lake pendant just along the eastern margin of the Tuolumne batholith we have discovered a brittle slip component in the ESCSZ that juxtaposes largely metasedimentary and metavolcanic rock packages. The metasedimentary package is dominated by bedded sandstones and siltstones and local conglomerates whereas the metavolcanics show a large range of volcanic and volcaniclastic units. All of the units dip steeply and have an average N-NW strike. Dextral oblique ductile shear is distributed in domains in both rock packages with varying width from ~2 km in the South to ~1 km in the North. Shear sense in planes at high angles to a steep to SW plunging mineral lineation include S-C structures, shear bands, asymmetrical folding, sigma and delta clasts, and asymmetrical boudins. Partitioning of shear is common with the metarhyolites and metasediments showing higher non-coaxial strain than in the metaandesite and metadacite units. Map-scale “z-shaped” asymmetrical folds within the shear zone are also consistent with dextral shearing. Folded and sheared dikes of the 88-85 Ma Cathedral Peak phase of the Tuolumne batholith are common in the shear zone. A newly discovered brittle slip surface with breccias, gouge, and local pseudotachylite and large quartz veins was also mapped in the center of the ductile shear zone typically along the contact between the western metasedimentary and eastern metavolcanics (often a metarhyolite at the contact) on the east. Local slickenlines, steps, and offset dikes indicate that the brittle fault also had oblique dextral movement, similar to the ductile shear zone. In the mapped area no dikes originating from the TB cross the brittle fault and some are terminated at the brittle fault surface We interpret these observations to indicate northward displacement of the metasedimentary package by first ductile then brittle faulting during cooling and possibly uplift of this region with the youngest motion post 82 Ma. Title: Behavior of the Spines in a Quiescent Prominence Observed by Hinode/SOT Authors: Ning, Z.; Cao, W.; Goode, P. R. Bibcode: 2009ApJ...707.1124N Altcode: We report the behaviors of the spines in a quiescent prominence from the observations on 2008 January 15 made with Hinode/SOT in Hα +0.076 Å, Hα-0.34 Å, and Ca II H line filters. Two spines (1 and 2) are visible in this event. In the spacetime plots of the Hα and Ca II intensities, the two spines seem to gradually move closer together, and finally merge, then separate again. Their behaviors are separated into two kinds of typical motions. On the Doppler diagrams, the spine 1 has a dominant redshift, and spine 2 favors a blueshift, which reveals that the spines 1 and 2 firstly display the drifting motions in opposite directions. The former is drifting northward, while the latter drifts southward. Second, both spines display large-scale oscillating motions. Their oscillating velocities, amplitudes, and periods have average values of 3 km s-1, ±5 Mm, and 98 minutes, respectively, indicating a small-amplitude oscillation with a long period. After the sinusoidal fitting, both spines almost exhibit an antiphase oscillating motions. The spine 2 oscillates 135° ahead of the spine 1. Such antiphase oscillations would reflect the coupling of the transverse oscillations of the spines in this prominence. Title: Evidence of Chromospheric Evaporation in the 2004 December 1 Solar Flare Authors: Ning, Zongjun; Cao, Wenda; Huang, Jing; Huang, Guangli; Yan, Yihua; Feng, Hengqiang Bibcode: 2009ApJ...699...15N Altcode: In this paper, we present the radio and hard X-ray evidence of chromospheric evaporation during an M1.0 flare which occurred on 2004 December 1. The radio emission was observed by the Solar Broadband Radio Dynamic Spectrometer in China, which yielded dynamic spectra of decimetric emission. The hard X-ray emission was observed by RHESSI. In the radio spectra, the burst is characterized by two groups of parallel-drifting structures, some of which change their drifting rates from positive to negative. Based on the standard flare model, we may explain these decimetric bursts in terms of chromospheric evaporation. On the other hand, RHESSI observations show that the hard X-ray emission in the energy range of 10-15 keV tends to rise from two footpoints to the looptop and eventually merges into a single looptop source, which is accepted as evidence of hard X-ray chromospheric evaporation. Such processes happened twice in this event. The drifting radio structures occurred between them, at the same time as the third hard X-ray peak was observed at 25-50 keV. Title: Spatial and Spectral Behaviors of Solar Flares Observed in Microwaves Authors: Ning, Zongjun; Cao, Wenda Bibcode: 2009SoPh..257..335N Altcode: The spatial and spectral behaviors of two solar flares observed by the Nobeyama Radioheliograph (NoRH) on 24 August 2002 and 22 August 2005 are explored. They were observed with a single loop-top source and double footpoint sources at the beginning, then with looplike structures for the rest of the event. NoRH has high spatial and temporal resolution at the two frequencies of 17 and 34 GHz where a nonthermal radio source is often optically thin. Such capabilities give us an opportunity to study the spatial and spectral behaviors of different microwave sources. The 24 August 2002 flare displayed a soft - hard - soft (SHS) spectral pattern in the rising - peak - decay phases at 34 GHz, which was also observed for the spectral behavior of both loop-top and footpoint sources. In contrast, the 22 August 2005 flare showed a soft - hard - harder (SHH) spectral pattern for its both loop-top and footpoint sources. It is interesting that this event showed a harder spectrum in the early rising phase. We found a positive correlation between the spectral index and microwave flux in both the loop-top source and the footpoint sources in both events. The conclusions drawn from the flux index could apply to the electron index as well, because of their simple linear relationship under the assumption of nonthermal gyrosynchrotron mechanism. Such a property of spatial and spectral behaviors of microwave sources gives an observational constraint on the electron acceleration mechanism and electron propagation. Title: Periodicity of Twisting Motions in Sunspot Penumbral Filaments Authors: Ning, Zongjun; Cao, Wenda; Goode, Philip R. Bibcode: 2009SoPh..257..251N Altcode: We study the periodicity of twisting motions in sunspot penumbral filaments, which were recently discovered from space (Hinode) and ground-based (SST) observations. A sunspot was well observed for 97 minutes by Hinode/SOT in the G-band (4305 Å) on 12 November 2006. By the use of the time - space gradient applied to intensity space - time plots, twisting structures can be identified in the penumbral filaments. Consistent with previous findings, we find that the twisting is oriented from the solar limb to disk center. Some of them show a periodicity. The typical period is about ≈ four minutes, and the twisting velocity is roughly 6 km s−1. However, the penumbral filaments do not always show periodic twisting motions during the time interval of the observations. Such behavior seems to start and stop randomly with various penumbral filaments displaying periodic twisting during different intervals. The maximum number of periodic twists is 20 in our observations. Studying this periodicity can help us to understand the physical nature of the twisting motions. The present results enable us to determine observational constraints on the twisting mechanism. Title: Post-focus Instrumentation Of The NST Authors: Cao, Wenda; Gorceix, N.; Andic, A.; Ahn, K.; Coulter, R.; Goode, P. Bibcode: 2009SPD....40.1803C Altcode: The NST (New Solar Telescope), 1.6 m clear aperture, off-axis telescope, is in its commissioning phase at Big Bear Solar Observatory (BBSO). It will be the most capable, largest aperture solar telescope in the US until the 4 m ATST (Advanced Technology Solar Telescope) comes on-line in the middle of the next decade. The NST will be outfitted with state-of-the-art post-focus instrumentation, which currently include Adaptive Optics system (AO), InfraRed Imaging Magnetograph (IRIM), Visible Imaging Magnetograph (VIM), Real-time Image Reconstruction System (RIRS), and Fast Imaging Solar Spectrograph (FISS). A 308 sub-aperture (349-actuator Deformable Mirror) AO system will enable diffraction limited observations over the NST's principal operating wavelengths from 0.4 µm through 1.7 µm. IRIM and VIM are Fabry-Perot based narrow-band tunable filter, which provide high resolution two-dimensional spectroscopic and polarimetric imaging in the near infrared and visible respectively. Using a 32-node parallel computing system, RIRS is capable of performing real-time image reconstruction with one image every minute. FISS is a collaboration between NJIT and Seoul National University to focus on chromosphere dynamics. This instruments would be installed this Summer as a part of the NST commissioning and the implementation of Nysmyth focus instrumentation. Key tasks including optical design, hardware/software integration and subsequent setup/testing on the NST, will be presented in this poster. First light images from the NST will be shown. Title: Oscillatory Behavior and its Connection to Granulation Authors: Andic, Aleksandra; Cao, W.; Goode, P. R.; Jess, D. B. Bibcode: 2009SPD....40.0933A Altcode: Results are presented from two distinct sets of the observations to further elucidate origin of, and the role of high frequency oscillations in

atmospheric dynamics. One set was performed using IBIS that Observatorio

Astrofisico di Arcetri developed. This 2D spectrograph utilized the Fe I 709nm spectral line at the Dunn Solar telescope, Sacramento Peak, of National Solar Observatory. This data set was first speckle reconstructed. The second data set was obtained from the same telescope using BBSO's IRIM with its Rockwell Near Infrared Camera measuring the Fe 1565.7nm spectral line.

It was determined that the magnetic field has a significant role in

propagation of the oscillations, and our near infrared observations revealed

new insights into the oscillatory dynamics of the deep photosphere. Detailed results will be presented. Title: Small-scale oscillations in a quiescent prominence observed by HINODE/SOT. Prominence oscillations Authors: Ning, Z.; Cao, W.; Okamoto, T. J.; Ichimoto, K.; Qu, Z. Q. Bibcode: 2009A&A...499..595N Altcode: Context: Investigations of the behavior of small-scale threads can provide an alternative approach to studying prominence dynamics and understanding its origin and nature.
Aims: The behavior of threads are analyzed in a quiescent prominence, including drifting and both the horizontally and vertically oscillating motions. These indicate waves in the solar prominence.
Methods: We used the Hα images at a setting wavelength of +0.076 Å. A quiescent prominence was observed by HINODE/SOT on 2008 January 15 for about 3 h in total.
Results: Consistent with previous findings, prominences show numerous thread-like structures. Some threads clearly exhibit both vertically and horizontally oscillatory motions, while others are only drifting. Complicated cases show both drifting and oscillatory motions simultaneously. In the upper part of the prominence, the threads are oscillating independently of each other. We find that three threads oscillate with the same phase for at least two periods. The oscillations seem to be strongly damped since they disappear after a few periods. The maximum number of observed periods is 8 in our observations. In the lower part of the prominence, however, the different threads have a mixed character with the individual oscillatory motions unstable for one entire period. Most oscillatory motions will disappear after a half period or less, while the new oscillatory motions are excited nearby. A 5-min period is predominant, and the oscillating amplitudes show an average value of ±3.5 km s-1. We find some upflows in the spicule layer, and they appear to transport the mass from photosphere (or spicules themselves) to the prominence. These upflows have an average velocity amplitude of 0.8 km s-1.
Conclusions: The threads exhibit three distinct behaviors. The first is only drifting, the second is typically oscillating, and the third shows both characteristics. There are no substantial differences between the periods of horizontally and vertically oscillating threads in this prominence. Title: Early Abnormal Temperature Structure of X-Ray Loop-Top Source of Solar Flares Authors: Shen, Jinhua; Zhou, Tuanhui; Ji, Haisheng; Wang, Na; Cao, Wenda; Wang, Haimin Bibcode: 2008ApJ...686L..37S Altcode: 2008arXiv0808.4047S This Letter is to investigate the physics of a newly discovered phenomenon—contracting flare loops in the early phase of solar flares. In classical flare models, which were constructed based on the phenomenon of the expansion of flare loops, an energy releasing site is put above flare loops. These models can predict that there is a vertical temperature gradient in the top of flare loops due to heat conduction and cooling effects. Therefore, the centroid of an X-ray loop-top source at higher energy bands will be higher in altitude, which we can define as the normal temperature distribution. With observations made by RHESSI, we analyzed 10 M- or X-class flares (9 limb flares). For all these flares, the movement of loop-top sources shows an obvious U-shaped trajectory, which we take as the signature of contraction-to-expansion of flare loops. We find that, for all these flares, a normal temperature distribution does exist, but only along the path of expansion. The temperature distribution along the path of contraction is abnormal, showing no spatial order at all. The result suggests that magnetic reconnection processes in the contraction and expansion phases of these solar flares are different. Title: Magnetic Reconnection Rate and RHESSI Hard X-Ray Imaging Spectroscopy of Well Resolved X-class Flares Authors: Xu, Y.; Jing, J.; Cao, W.; Wang, H. Bibcode: 2008AGUSMSP51C..06X Altcode: Three X-class white-light flares were captured by BBSO observing team at NSO in 2003 and the Solar Optical Telescope (SOT) on board HINODE in 2006. They were all typical two-ribbon flares and the flare ribbons were resolved to the diffraction limit in G-band observations. We measure the velocities of ribbon-motion Vn for different flaring kernels and the corresponding magnetic flux density Bn. We compare the correlation between Vn and Bn with previous obtained empirical relationship. In addition, we investigate the temporal evolution of shear-angle between conjugate foot-points and magnetic neutral line using both Hard X-ray (HXR) observation obtained by Ramaty High Energy Solar Spectroscopic Imager (RHESSI) and G-band data. The results show clear decrease of shear-angles, indicating motion of flare kernels along the flare ribbons in early stage of flares. The optical observations including G-band show that some isolated HXR flare kernels are actually connected by the optical flare ribbons. Using the high resolution cleaned HXR images, we also present the spectral information obtained for all the HXR kernels and discuss the difference of spectral index in the different magnetic field environment. Title: Multiwavelength Study of Flow Fields in Flaring Super Active Region NOAA 10486 Authors: Deng, N.; Xu, Y.; Yang, G.; Cao, W.; Liu, C.; Rimmele, T. R.; Wang, H.; Denker, C. Bibcode: 2006AGUFMSH31B..06D Altcode: We present high resolution observations of horizontal flow fields measured by Local Correlation Tracking from intensity images in three wavelengths, i.e., G-Band (GB), White-Light (WL), and Near InfraRed (NIR). The observations were obtained on 2003 October~29 within the flaring super active region NOAA~10486, which was the source of several X-class flares, including an X10 flare that occurred near the end of the observing run. The data were obtained at National Solar Observatory/Sacramento Peak (NSO/SP) using the newly developed high-order Adaptive Optics (AO) system. We also use Dopplergrams and magnetograms from MDI on board SOHO to study the line-of-sight flow and magnetic field. We observe persistent and long-lived (at least 5 hours) strong horizontal and vertical shear flows (both in the order of 1 km s-1) along the magnetic Neutral Line (NL) until the X10 flare occurred. From lower photospheric level (NIR), the direction of the flows does not change up to the upper photosphere (GB), while the flow speeds in the shear motion regions decrease and on the contrary those in regions without shear motions increase with increasing altitude. Right after the X10 flare, the magnetic gradient decreased, while both horizontal and vertical shear flows dramatically enhanced near the flaring NL. Our results suggest that photospheric shear flows and local magnetic shear near the NL can increase after the flare, which may be the result of shear release in the overlying large-scale magnetic system or the reflection of a twisted or sheared flux emergence carrying enough energy from subphotosphere. Title: First Light of the Near-Infrared Narrow-Band Tunable Birefringent Filter at Big Bear Solar Observatory Authors: Cao, Wenda; Hartkorn, Klaus; Ma, Jun; Xu, Yan; Spirock, Tom; Wang, Haimin; Goode, Philip R. Bibcode: 2006SoPh..238..207C Altcode: 2006SoPh..tmp...53C We discuss a near-infrared (NIR) narrow-band tunable birefringent filter system newly developed by the Big Bear Solar Observatory (BBSO). This is one of the first narrow-bandpass NIR filter systems working at 1.56 μm which is used for the observation of the deepest solar photosphere. Four stages of calcite were used to obtain a bandpass of 2.5 Å along with a free spectral range (FSR) of 40 Å. Some unique techniques were implemented in the design, including liquid crystal variable retarders (LCVRs) to tune the bandpass in a range of ±100 Å, a wide field configuration to provide up to 2° incident angle, and oil-free structure to make it more compact and handy. After performing calibration and characteristic evaluation at the Evans Facility of the National Solar Observatory at Sacramento Peak (NSO/SP), a series of high-resolution filtergrams and imaging polarimetry observations were carried out with the Dunn Solar Telescope of NSO/SP and the 65-cm telescope of BBSO, in conjunction with the high-order adaptive optics system and the Fabry-Pérot Interferometer (FPI). In this paper, we describe the optical design and discuss the calibration method. Preliminary observations show that it is capable of serving as either a stand-alone narrow-band filter for NIR filtergram observations or an order-sorting filter of a FPI applied to NIR two-dimensional imaging spectro-polarimetry. Title: Progress on the 1.6-meter New Solar Telescope at Big Bear Solar Observatory Authors: Denker, C.; Goode, P. R.; Ren, D.; Saadeghvaziri, M. A.; Verdoni, A. P.; Wang, H.; Yang, G.; Abramenko, V.; Cao, W.; Coulter, R.; Fear, R.; Nenow, J.; Shoumko, S.; Spirock, T. J.; Varsik, J. R.; Chae, J.; Kuhn, J. R.; Moon, Y.; Park, Y. D.; Tritschler, A. Bibcode: 2006SPIE.6267E..0AD Altcode: 2006SPIE.6267E..10D The New Solar Telescope (NST) project at Big Bear Solar Observatory (BBSO) now has all major contracts for design and fabrication in place and construction of components is well underway. NST is a collaboration between BBSO, the Korean Astronomical Observatory (KAO) and Institute for Astronomy (IfA) at the University of Hawaii. The project will install a 1.6-meter, off-axis telescope at BBSO, replacing a number of older solar telescopes. The NST will be located in a recently refurbished dome on the BBSO causeway, which projects 300 meters into the Big Bear Lake. Recent site surveys have confirmed that BBSO is one of the premier solar observing sites in the world. NST will be uniquely equipped to take advantage of the long periods of excellent seeing common at the lake site. An up-to-date progress report will be presented including an overview of the project and details on the current state of the design. The report provides a detailed description of the optical design, the thermal control of the new dome, the optical support structure, the telescope control systems, active and adaptive optics systems, and the post-focus instrumentation for high-resolution spectro-polarimetry. Title: Diffraction-limited Polarimetry from the Infrared Imaging Magnetograph at Big Bear Solar Observatory Authors: Cao, Wenda; Jing, Ju; Ma, Jun; Xu, Yan; Wang, Haimin; Goode, Philip R. Bibcode: 2006PASP..118..838C Altcode: The Infrared Imaging Magnetograph (IRIM) system developed by Big Bear Solar Observatory (BBSO) has been put into preliminary operation. It is one of the first imaging spectropolarimeters working at 1565 nm and is used for the observations of the Sun at its opacity minimum, exposing the deepest photospheric layers. The tandem system, which includes a 4.2 nm interference filter, a unique 0.25 nm birefringent Lyot filter, and a Fabry-Pérot etalon, is capable of providing a bandpass as low as 0.01 nm in a telecentric configuration. A fixed quarter-wave plate and a nematic liquid crystal variable retarder are employed for analyzing the circular polarization of the Zeeman components. The longitudinal magnetic field is measured for the highly Zeeman-sensitive Fe I line at 1564.85 nm (Landé factor g=3). The polarimetric data were taken through a field of view of ~145''×145'' and were recorded by a 1024×1024 pixel, 14 bit HgCdTe CMOS focal plane array camera. Benefiting from the correlation tracking system and a newly developed adaptive optics system, the first imaging polarimetric observations at 1565 nm were made at the diffraction limit on 2005 July 1 using BBSO's 65 cm telescope. After comparing the magnetograms from IRIM with those taken by the Michelson Doppler Imager on board SOHO, it was found that all the magnetic features matched very well in both sets of magnetograms. In addition, Stokes V profiles obtained from the Fabry-Pérot etalon scan data provide access to both the true magnetic field strength and the filling factor of the small-scale magnetic flux elements. In this paper, we present the design, fabrication, and calibration of IRIM, as well as the results of the first scientific observations. Title: High-Resolution Studies of Complex Solar Active Regions Authors: Deng, Na; Wang, H.; Liu, C.; Yang, G.; Xu, Y.; Tritschler, A.; Cao, W.; Rimmele, T. R.; Denker, C. Bibcode: 2006SPD....37.3401D Altcode: 2006BAAS...38..258D Most Flares and CMEs occur or originate in solar active regions, typically in sunspots with complex magnetic fields such as delta-spots. Rapid and substantial changes of the sunspot structure have been discovered to be associated with flares/CMEs. Rapid penumbral decay and umbral enhancements are intensity changes, which are interpreted as signatures of magnetic reconnection during the flare. The magnetic field lines switch from an inclined to a more vertical orientation. Strong and long-lived shear flows near the flaring magnetic inversion line have been detected using Local Correlation Tracking (LCT) techniques based on multi-wavelength high resolution observations. A newly observed and important phenomenon is the increased local shear flow and magnetic shear right after the flare in spite of theoretical models requiring an overall decrease in the magnetic free energy. The emergence of a twisted or pre-sheared flux rope near the neutral line is a possible interpretation. Using high-order adaptive optics combined post-facto speckle masking image reconstruction, we can obtain time-series with highly improved image quality and spatial resolution in the order of 0.14" or about 100 km on the solar surface. We combine the observed longitudinal Dopplergrams obtained with two-dimensional imaging spectrometer and transverse LCT flow maps derived from time-series of speckle reconstructed images to create real local 3D flow maps (view from above). Using these precise 3D flow maps observed in a typical sunspot in the course of its center to limb disc passage, we observe distinct division line between radially inward and outward flow in the penumbra and its evolution during the decaying phase of the sunspot. The inclination angles of penumbral flow channels are also calculated.Acknowledgments: This work is supported by NSF under grant ATM 03-42560, ATM 03-13591, ATM 02-36945, ATM 05-48952, and MRI AST 00-79482 and by NASA under grant NAG 5-13661. Title: Multiwavelength Study of Flow Fields in Flaring Super Active Region NOAA 10486 Authors: Deng, Na; Xu, Yan; Yang, Guo; Cao, Wenda; Liu, Chang; Rimmele, Thomas R.; Wang, Haimin; Denker, Carsten Bibcode: 2006ApJ...644.1278D Altcode: We present high-resolution observations of horizontal flow fields measured by local correlation tracking from intensity images in three wavelengths, i.e., G band (GB), white light (WL), and near-infrared (NIR). The observations were obtained on 2003 October 29 within the flaring super active region NOAA 10486, which was the source of several X-class flares, including an X10 flare that occurred near the end of the observing run. The data were obtained at National Solar Observatory/Sacramento Peak (NSO/SP) using the newly developed high-order adaptive optics (AO) system. We also use Dopplergrams and magnetograms from MDI on board SOHO to study the line-of-sight flow and magnetic field. We observe persistent and long-lived (at least 5 hr) strong horizontal and vertical shear flows (both in the order of 1 km s-1) along the magnetic neutral line (NL) until the X10 flare occurred. From lower photospheric level (NIR), the direction of the flows does not change up to the upper photosphere (GB), while the flow speeds in the shear motion regions decrease and, on the contrary, those in regions without shear motions increase with increasing altitude. Right after the X10 flare, the magnetic gradient decreased, while both horizontal and vertical shear flows dramatically enhanced near the flaring NL. Our results suggest that photospheric shear flows and local magnetic shear near the NL can increase after the flare, which may be the result of shear release in the overlying large-scale magnetic system or the reflection of a twisted or sheared flux emergence carrying enough energy from the subphotosphere. Title: The first light of the Infrared Imaging Magnetographat Big Bear Solar Observatory Authors: Cao, Wenda; Ma, J.; Jing, J.; Xu, Y.; Denker, C.; Wang, H.; Goode, P. Bibcode: 2006SPD....37.0612C Altcode: 2006BAAS...38..227C The InfraRed Imaging Magnetograph (IRIM) system developed by Big Bear Solar Observatory (BBSO) has been put into preliminary operation. It is one of the first imaging spectro-polarimeters working at 1565 nm, and is used for the observations of the Sun at its opacity minimum, exposing the deepest photospheric layers. The tandem system of a 4.2 nm interference filter, an unique 0.25 nm birefringent Lyot filter and a Fabry-Perot etalon is capable of providing a bandpass as low as 0.01 nm in a telecentric configuration. A fixed quarter wave plate and a nematic liquid crystal variable retarder are employed for analyzing the circular polarization of the Zeeman components. The longitudinal magnetic field is measured for highly Zeeman-sensitive Fe I line at 1564.85 nm (Lande factor g = 3). The polarimetric data, with a field of view (FOV) 145" × 145", were recorded by a 1024 × 1024 pixel, 14-bit HgCdTe CMOS focal plane array camera. Benefiting from the Correlation Tracking system (CT) and newly developed Adaptive Optics (AO) system, the first imaging polarimetric observations at 1565 nm were made at the diffraction limit on 1 July 2005 using BBSO's 65 cm telescope. After comparing the magnetograms from IRIM with those taken by the Michelson Doppler Imager (MDI) on board SOHO, it was found that all the magnetic features matched very well in both sets of magnetograms. Also, Stokes V profiles obtained from the Fabry-Perot etalon scanning data provide access to both the true magnetic field strength and filling factor of the small-scale magnetic flux elements. In this paper, we present the design, fabrication, and calibration of IRIM, as well as the results of the first scientific observations. Title: High-Resolution Observations of Multiwavelength Emissions during Two X-Class White-Light Flares Authors: Xu, Yan; Cao, Wenda; Liu, Chang; Yang, Guo; Jing, Ju; Denker, Carsten; Emslie, A. Gordon; Wang, Haimin Bibcode: 2006ApJ...641.1210X Altcode: We observed two X-class white-light flares (WLFs) on 2003 October 29 (~20:40 UT) and November 2 (~17:16 UT) using the Dunn Solar Telescope (DST) and its High-Order Adaptive Optics (HOAO) system in several wavelengths. The spatial resolution was close to the diffraction limit of DST's 76 cm aperture, and the cadence was as high as 2 s. This is the first time that WLFs have been observed in the near-infrared (NIR) wavelength region. We present a detailed study in this paper comparing photospheric continuum observations during the two events with corresponding line-of-sight magnetograms from the Solar and Heliospheric Observatory (SOHO) Michelson Doppler Imager (MDI) and hard X-ray (HXR) data from the Ramaty High-Energy Solar Spectroscopic Imager (RHESSI). We also discuss several models that provide possible mechanisms to explain these continuum enhancements, especially in the NIR. Title: Properties of Small Dark Features Observed in the Pure Near-Infrared and Visible Continua Authors: Xu, Yan; Cao, Wenda; Ma, Jun; Hartkorn, Klaus; Jing, Ju; Denker, Carsten; Wang, Haimin Bibcode: 2005ApJ...628L.167X Altcode: High-resolution images in the visible and near-infrared (NIR) continua at around 1560 nm were obtained of solar active regions NOAA AR 10707 and AR 10486 with the Dunn Solar Telescope (DST) at the National Solar Observatory/Sacramento Peak (NSO/SP) on 2004 December 1 and 2 and 2003 October 29. The images were taken with the high-order adaptive optics (HOAO) system, and the spatial resolution was close to the diffraction limit of the 76 cm aperture DST in both wavelengths. For the 2004 December run, the NIR observations were made with a newly developed Lyot filter system, which was designed at the Center for Solar-Terrestrial Research (CSTR)/New Jersey Institute of Technology (NJIT). The filter has a bandpass of 2.5 Å that allows us to observe the pure NIR continuum at the opacity minimum. Our data show that all dark features in the NIR are also dark in the visible light. There is no evidence showing the existence of so-called dark faculae, i.e., faculae that have negative contrasts in the NIR but positive contrasts in the visible. The negative peak contrasts of these small pores are about 50% in the visible and 25% in the NIR, and their dimensions are in the range of 1"-4". Title: Near-infrared HeI 1083nm Stokes polarimeter based on liquid crystal variable retarders Authors: Zhang, Zhiyong; Deng, Yuanyong; Wong, Dongguang; Sun, Yingzi; Cao, Wenda Bibcode: 2005SPIE.5901..377Z Altcode: The spectral line of HeI 1083nm is important and potential to measure the magnetic field of the solar upper chromosphere. In this paper, we present a newly developed Stokes polarimeter for measuring the polarized signals at this wavelength. In this device, two Liquid Crystal Variable Retarders (LCVRs) were employed as electro-optical modulators and a Wollaston prism as analyzer and polarized beam splitter. Compared to the commonly used linear-polarized analyzer, the Wollaston prism analyzer has main advantage to minimize the seeing-induced contamination of earth's atmosphere, as it produces simultaneous images by the two perpendicular polarization states. A novel optical design which focuses the two beams on different detector areas is described. And the accurate calibration methods are introduced too. Title: 1024 × 1024 HgCdTe CMOS camera for infrared imaging magnetograph of Big Bear Solar Observatory Authors: Cao, W.; Xu, Y.; Denker, C.; Wang, H. Bibcode: 2005SPIE.5881..245C Altcode: The InfraRed Imaging Magnetograph (IRIM)1,2 is a two-dimensional narrow-band solar spectro-polarimeter currently being developed at Big Bear Solar Observatory (BBSO). It works in the near infrared (NIR) from 1.0 μm to 1.7 μm and possesses high temporal resolution, high spatial resolution, high spectral resolving power, high magnetic sensitivity. As the detector of IRIM, the 1024 × 1024 HgCdTe TCM8600 CMOS camera manufactured by the Rockwell Scientific Company plays a very important role in acquiring the high precision solar spectropolarimetry data. In order to make the best use of it for solar observation, the characteristic evaluation was carried out at BBSO and National Solar Observatory (NSO), Sacramento Peak in October 2003. The paper presents a series of measured performance parameters including linearity, readout noise, gain, full well capacity, hot pixels, dark, flat field, frame rate, vacuum, low temperature control, etc., and shows some solar infrared narrow band imaging observation results. Title: Do Dark Faculae Exist? Authors: Xu, Y.; Cao, W.; Ma, J.; Hartkon, K.; Jing, J.; Denker, C.; Wang, H. Bibcode: 2005AGUSMSP31A..01X Altcode: High-resolution images in visible light and the near infrared (NIR) continuum around 1560~nm were obtained in solar active region NOAA~10707 with the Dunn Solar Telescope (DST) at the National Solar Observatory/Sacramento Peak (NSO/SP) on 2004 December~2 and 7. A spatial resolution close to the diffraction limit of the 76~cm DST was achieved with high-order adaptive optics system. The observation were made with a near infrared tunable Lyot filter system newly developed by Big Bear Solar Observatory (BBSO). The filter has a bandpass of 2.5~Å. This allows us to observe the pure NIR continuum that represents the opacity minimum. Our data show that the contrast of faculae has the same sign in the visible and the NIR continua. There is no evidence for the existence of so-called "dark faculae", faculae that have negative contrasts in the NIR and positive contrasts in visible light. We conclude that the previously observed "dark faculae" are unresolved pores.

This work is supported by NSF under grants ATM-0313591, ATM-0236945, ATM-0233931 and AST-0307676, by NASA under grants NAG5-10910, NAG5-10212 and NAG5-12733, and by Air Force under grant F49620-02-1-0265 and by NSFC-10103004. Title: The New Solar Telescope at Big Bear Solar Observatory - A Progress Report Authors: Denker, C.; Cao, W.; Chae, J.; Coulter, R.; Kuhn, J. R.; Marquette, W. H.; Moon, Y.; Park, Y.; Ren, D.; Tritschler, A.; Varsik, J. R.; Wang, H.; Yang, G.; Shoumko, S.; Goode, P. R. Bibcode: 2005AGUSMSP43A..07D Altcode: The New Solar Telescope (NST) is a new 1.6-meter, off-axis telescope for the Big Bear Solar Observatory (BBSO) in California. The NST is collaboration between BBSO, the Korean Astronomical Observatory (KAO) and Institute for Astronomy (IfA) at the University of Hawaii. BBSO is an ideal site for high-spatial resolution observations, since this mountain-lake site provides consistent seeing conditions with extended periods of excellent seeing from sunrise to sunset. These unique seeing characteristics make BBSO ideally suited for combined high-resolution campaigns and synoptic observations, which are essential for studies of solar activity and space weather. In this progress report, we present the latest information on the optical design, the optical support structure, the telescope control system and the requisite instrumentation for the telescope. Acknowledgements: This work has been supported by NSF under grants ATM-0236945, ATM-0342560, MRI-0320540, and Air Force DURIP F-49620-03-1-0271. Title: Dissertation Talk: High Resolution Observations of Multi-Wavelength Emissions During Two X-Class White-Light Flares Authors: Xu, Y.; Cao, W.; Liu, C.; Yang, G.; Jing, J.; Denker, C.; Wang, H. Bibcode: 2005AGUSMSP51C..01X Altcode: We observed two X-class white-light flares (WLF) on 2003 October~29 (~20:40~UT) and November~2 (~17:16 UT) using the Dunn Solar Telescope (DST) and its High-Order Adaptive Optics (HOAO) system in several wavelengths. The spatial resolution was close to the diffraction limit of DST's 76~cm aperture. The temporal resolution was as high as 2~s. It is the first time that WLFs were observed in the Near Infrared (NIR) wavelength region. We present a detailed study in this presentation by comparing the photospheric continuum observations during these two events with corresponding line-of-sight (LOS) magnetograms of the Michelson Doppler Imager (MDI) and hard X-ray (HXR) data of the Ramaty High Energy Solar Spectroscopic Imager (RHESSI). Our observations show that:

Significant intensity enhancements were observed in the visible and NIR continua and G-band during the impulsive phase of the flares. The maximum intensity enhancements were 37% of white-light and 25% of the NIR continuum during the first event, and 76% of white-light and 66% of the NIR continuum for the second flare. The flares were typical two ribbon flares. All ribbons showed a brighter core surrounded by a halo structure. The ribbon separation speeds were about 28~km/s in the first and 24~km/s in the second event based on NIR observations. The derived electric fields in the reconnection current sheet Ec are about 23~V~ cm-1 and 22~V~cm-1, respectively. The NIR emission and the impulsive HXR emission up to 800~keV were well correlated, not considering a small delay of less than two minutes. The high resolution and high cadence images gave us the first chance to measure the cooling time of flares close to the photosphere. We found that the cooling process could be characterized by two steps. A quick temperature drop, which is related to the cooling process of the bright cores, and a relative slow decay related to the halo structures. The fine scale is in the order of less than 30~s and a few minutes for these two steps, respectively.

Based on these observational results, we discuss several models that provide possible mechanisms to explain these continuum enhancements, especially in the NIR. This work is supported by NSF under grants ATM-0313591, ATM-0236945, ATM-0233931 and AST-0307676, by NASA under grants NAG5-10910, NAG5-10212 and NAG5-12733, and by Air Force under grant F49620-02-1-0265 and by NSFC-10103004. Title: First Light for the Near-Infrared Narrow-Band Tunable Birefringent Filter of the Big Bear Solar Observatory Authors: Cao, W.; Hartkorn, K.; Ma, J.; Wang, J.; Xu, Y.; Spirock, T.; Denker, C.; Wang, H. Bibcode: 2005AGUSMSP43A..08C Altcode: A new near-infrared, narrow-band tunable birefringent filter has been developed by BBSO/NJIT. This filter, one of the first Lyot filters in the near-infrared, has a FWHM of about 2.5 ~Å at the design wavelength of 1.5648 μm and is used to observe the deepest levels of the photosphere. New techniques were employed in the design, including liquid crystal retarders to tune the center wavelength in range of ± 100 ~Å. After finishing the calibration and evaluation of the filter at the Evans Facility of the NSO at Sacramento Peak, high spatial resolution filtergrams and imaging spectroscopy observations were carried out at the Dunn Solar Telescope of NSO in December 2004 with the use of the high-order Adaptive Optics System. For some of these observations, the Lyot filter was combined with a Fabry-Perot Etalon to achieve a much higher spectral resolution. We discuss the calibration methods and present some preliminary observation results. Title: On the Relation Between Flow Fields and Magnetic Field Evolution in Flare Productive NOAA Active Region 10486 Authors: Deng, N.; Xu, Y.; Yang, G.; Cao, W.; Rimmele, T. R.; Wang, H.; Denker, C. Bibcode: 2005AGUSMSP51C..05D Altcode: We present high resolution observations of flow fields within solar NOAA active region 10486 before an X10 flare on October 29, 2003. From 2003 October 28 to November 4, a complex δ-sunspot located in NOAA 10486 produced dramatic flare activities in the descending phase of the solar cycle 23. The flow fields are measured by local correlation tracking (LCT) based on speckle masking white-light images, near-infrared (NIR) continuum images at 1.56 μm, and G-band images obtained with the Dunn Solar Telescope (DST) of the National Solar Observatory/Sacramento Peak (NSO/SP). NSO's newly developed high-order adaptive optics system at the DST was used to achieve diffraction-limited imaging with a high signal-to-noise ratio. The spatial resolution of the images approaches the diffraction limit of the 76 cm aperture DST of about 0.14 ″ at 527 nm. In addtion, we use longitudinal magnetograms from the Michelson Doppler Imager (MDI) on board the Solar and Heliospheric Observatory (SoHO) to study the evolution of photospheric magnetic field and its correlation with flow fields in this flare productive active region. We link strong magnetic shear and fast emergence of magnetic flux to photospheric flows, which might trigger the flares. Our result suggests that the time-series analysis of the photospheric flow fields is a critical observational diagnostic for the evolution of magnetic fields in solar active regions. This work was supported by NSF under grant ATM 03-42560, ATM 03-13591, ATM 02-36945, and MRI AST 00-79482 and by NASA under grant NAG 5-13661. Title: Narrow-band Near Infrared Filtergram Observation of Light Bridges and Umbral Dots Authors: Ma, J.; Cao, W.; Denker, C.; Wang, H. Bibcode: 2005AGUSMSP31A..03M Altcode: We are presenting the observations of the active region NOAA 10709 on December, 2004 using 0.12Å~narrow band filter centered around 1.56μm. The observation run was carried out using Dunn Tower Telescope of NSO (SacPeak) with high-order AO system. The averaged angular resolution of this observation is 0.5" or better. These high resolution data in near infrared offer a new view on the photospheric structures of sunspot near opacity minimum. By using the tunable near infrared narrow band filtergram, we are able to construct magnetic field strength map of sunspot. In particular, we will show the magnetic structure of light bridges and umbral dots. Title: Magnetic Helicity Change Rate Associated with an X10 White-Light Flare Authors: Yang, G.; Xu, Y.; Cao, W.; Carsten, D.; Wang, H. Bibcode: 2005AGUSMSP23B..01Y Altcode: Solar active region NOAA 10486 was very active during the descending phase of solar cycle 23. Eight X-class flares and a multitude of M-class flares were observed in this region from 2003 October 23 to November 6. In our previous study we presented the high resolution observations of the flow fields associated with the X10 white-light flare in this active region on 2003 October 29. We linked the strong photospheric shear flow with the flare. In this paper, we further our study by investigating the magnetic helicity injection rate of the active region NOAA 10486 covering the time period of this X10 white-light flare. The magnetic helicity injection rate due to horizontal photospheric motions is determined by analyzing a set of 1 minute cadence full-disk magnetograms taken by the Michelson Doppler Imager on board the Solar and Heliospheric Observatory, in addition to the flow fields derived previously. The results of this study will aid us to understand the process of energy build-up and release associated with the flare. Title: High-Spatial-Resolution Imaging Combining High-Order Adaptive Optics, Frame Selection, and Speckle Masking Reconstruction Authors: Denker, Carsten; Mascarinas, Dulce; Xu, Yan; Cao, Wenda; Yang, Guo; Wang, Haimin; Goode, Philip R.; Rimmele, Thomas Bibcode: 2005SoPh..227..217D Altcode: We present, for the first time, high-spatial-resolution observations combining high-order adaptive optics (AO), frame selection, and post-facto image correction via speckle masking. The data analysis is based on observations of solar active region NOAA 10486 taken with the Dunn Solar Telescope (DST) at the Sacramento Peak Observatory (SPO) of the National Solar Observatory (NSO) on 29 October 2003. The high Strehl ratio encountered in AO corrected short-exposure images provides highly improved signal-to-noise ratios leading to a superior recovery of the object's Fourier phases. This allows reliable detection of small-scale solar features near the diffraction limit of the telescope. Speckle masking imaging provides access to high-order wavefront aberrations, which predominantly originate at high atmospheric layers and are only partially corrected by the AO system. In addition, the observations provided qualitative measures of the image correction away from the lock point of the AO system. We further present a brief inspection of the underlying imaging theory discussing the limitations and prospects of this multi-faceted image reconstruction approach in terms of the recovery of spatial information, photometric accuracy, and spectroscopic applications. Title: Photospheric Shear Flows along the Magnetic Neutral Line of Active Region 10486 prior to an X10 Flare Authors: Yang, Guo; Xu, Yan; Cao, Wenda; Wang, Haimin; Denker, Carsten; Rimmele, Thomas R. Bibcode: 2004ApJ...617L.151Y Altcode: We present high spatial resolution observations of proper motions in the solar NOAA Active Region 10486 using a high-order adaptive optics system, frame selection, and speckle-masking image reconstruction. The data were obtained with the Dunn Solar Telescope of the National Solar Observatory/Sacramento Peak on 2003 October 29. The resolution of the images approaches the diffraction-limited resolution of the Dunn Solar Telescope of about 0.14" at 527 nm. We analyzed a 2 hr time series with a 1 minute cadence prior to an X10 white-light flare. Local correlation tracking was used to measure the photospheric proper motions. We find specific evidence of strong shear flows along the magnetic neutral line; these shear flows are well defined and correlated with white-light flare kernels in the visible and infrared. The speed along the flow channels can reach up to 1.6 km s-1, and the separation of channels with head-on flows can be less than 1". Counterstreaming and complex flow patterns have been distinguishing characteristics of this extraordinarily flare-productive active region. Title: Near infrared (NIR) achromatic phase retarder Authors: Ma, Jun; Wang, Jingshan; Cao, W.; Denker, Carsten; Wang, Haimin Bibcode: 2004SPIE.5523..139M Altcode: The tunable near InfraRed Lyot filter (TNIRLF) is one of the focal plane instruments for Advanced Technology Solar Telescope (ATST) project of the National Solar Observatory (NSO). Achromatic half waveplate and quarter waveplates working from 1000 nm to 1700 nm will be used in this filter. In this paper, we give a description of the design and development for the synthesized achromatic waveplates using quartz plates. The retardance variation is within 1% over the full spectral range and we discuss the variance of optical axis. Title: Near infrared waveplate Authors: Wang, Dongguang; Deng, Yuanyong; Cao, Wenda Bibcode: 2004SPIE.5492.1786W Altcode: The waveplate made of Polyvinyl Alcohol (PVA) plastic film has several advantages compared with that of birefringent crystal in visible region, such as its lower cost and insensitivity to temperature and incidence angle. What are the performances when they are used in the near infrared spectral region? In this paper, we provide some experimental results of infrared PVA waveplates. To do this, we make some samples and measure their polarization characteristics at several aspects. Firstly, we measure the performance of these PVA waveplates by precise instruments in laboratory. Secondly, we put the waveplates into a Stokes polarimeter to observe the solar magnetic field at near infrared line FeI1.56μm. By use of this polarimeter mounted on the vertical spectrograph of 2m McMath telescope at Kitt Peak, the two-dimensional Stokes parameters, I, Q, U, and V, of a sunspot were observed. From the results of laboratory and observation, we get the conclusion that PVA waveplate has the fair polarization performance to be used to observe the solar magnetic fields in the near infrared spectral region. By these experiments, we provide a design of an achromatic waveplate in infrared region, which consists of five-element, to illustrate the PVA waveplate is the best choice to it. Title: Near-Infrared Observations at 1.56 Microns of the 2003 October 29 X10 White-Light Flare Authors: Xu, Yan; Cao, Wenda; Liu, Chang; Yang, Guo; Qiu, Jiong; Jing, Ju; Denker, Carsten; Wang, Haimin Bibcode: 2004ApJ...607L.131X Altcode: We present high-resolution observations of an X10 white-light flare in solar NOAA Active Region 10486 obtained with the Dunn Solar Telescope (DST) at the National Solar Observatory/Sacramento Peak on 2003 October 29. Our investigation focuses on flare dynamics observed in the near-infrared (NIR) continuum at 1.56 μm. This is the first report of a white-light flare observed at the opacity minimum. The spatial resolution was close to the diffraction limit of the 76 cm aperture DST. The data benefited from a newly developed high-order adaptive optics system and a state-of-the-art NIR complex metal oxide semiconductor focal plane array. In addition, we compared hard X-ray (HXR) data of RHESSI and magnetograms of the Michelson Doppler Imager on board SOHO with the NIR continuum images. Although it is still possible that some high-energy electrons penetrate deep to this layer, a more likely explanation of the observed emission is back-warming. During the impulsive phase of the flare, two major flare ribbons moved apart, which were both temporally and spatially correlated with RHESSI HXR ribbons. The maximum intensity enhancement of the two flare ribbons is 18% and 25%, respectively, compared to the quiet-Sun NIR continuum. The separation speed of the ribbons is about 38 km s-1 in regions with weak magnetic fields and decreases to about 19 km s-1, where stronger magnetic fields are encountered. The derived electric field in reconnection current sheet Ec is of the order of 45 V cm-1 during the flare maximum. Title: Near Infrared Obsevations at 1.56 μ m of the 2003 October 29 X10 White-Light Flare Authors: Xu, Y.; Cao, W.; Liu, C.; Yang, G.; Qiu, J.; Jing, J.; Denker, C.; Wang, H. Bibcode: 2004AAS...204.4712X Altcode: 2004BAAS...36..738X We present high resolution observations of an X10 white-light flare in solar active region NOAA 10486 obtained with the Dunn Solar Telescope (DST) at the National Solar Observatory/Sacramento Peak (NSO/SP) on 2003 October 29. Our investigation focusses on flare dynamics observed in the near-infrared (NIR) continuum at 1.56 μ m. This is the first report of a white-light flare observed in the NIR. The spatial resolution was close to the diffraction limit of the 76 cm aperture DST. The data benefited from a newly developed high order adaptive optics (AO) system and a state-of-the-art NIR complex metal oxide semiconductor (CMOS) focal plane array (FPA). In addition, we compared hard X-ray (HXR) data of the Ramaty High Energy Solar Spectroscopic Imager (RHESSI) and magnetograms of the Michelson Doppler Imager (MDI) onboard the Solar and Heliospheric Observatory (SoHO) with the NIR continuum images. Since the NIR data were observed at the opacity minimum, only the most energetic electrons can penetrate to this layer in the deep photosphere. As a consequence, the flare ribbons appear to be very thin (<2 arcseconds) and well defined. During the impulsive phase of the flare, two major flare ribbons moved apart, which were both temporally and spatially correlated with RHESSI HXR ribbons. The two ribbons ranges are 18% to 25% brighter than the quiet sun NIR continuum. The separation speed of the ribbons is about 38 km/s in regions with weak magnetic fields and decreases to about 19 km/s, where stronger magnetic fields are encountered. The derived reconnection electric field Ec is of order 50 Vcm-1 at the flare maximum. Title: The VIsible and InfraRed Imaging Magnetograph (VIM-IRIM) at Big Bear Solar Observatory Authors: Cao, W.; Tritschler, A.; Denker, C.; Wang, H.; Shumko, S.; Ma, J.; Wang, J.; Marquette, B. Bibcode: 2004AAS...204.6907C Altcode: 2004BAAS...36..795C The Visible-light and the InfraRed Imaging Magnetograph (VIM-IRIM) are Fabry-Perot based filtergraphs working in a telecentric configuration, planned to upgrade the capability for measuring solar magnetic fields at BBSO. Both filtergraph instruments are designed to work with the combination of a narrow-band prefilter and a single Fabry-Perot etalon. VIM and IRIM will provide high temporal resolution, high spatial resolution (< 0.2 "/pixel image scale), high spectral resolution (< 0.1 Å) simultaneous observation at 600-700 nm and 1.0-1.6 μ m with a substantial field of view 170", respectively. Modifications in the setup allow also for scanning different spectral lines that cover the height range from the solar photosphere up to the solar chromopshere. Here we describe the optical setup and present first observations to demonstrate the feasibility of the instrument. After the instrument has proven to work as a 2D-spectrometer, the upgrade to a 2D spectropolarimeter is planned. Title: Magnetic Helicity Change Rate Associated With X-Class and M-Class Flares Authors: Hartkorn, K.; Wang, H.; Cao, W.; Denker, C.; Xu, Y. Bibcode: 2004AAS...204.3901H Altcode: 2004BAAS...36..714H We investigate the total helicity change rate of active regions during the time period of five X-class and five M-class flares. The X-class flares include the X17 flare on October 28 2003 and the X11 flare on October 29 2003. For the X11 flare we have high-resolution IR and G-band data available which allows us to compare flow fields derived from this high-resolution data with the flow fields derived from MDI full disc magnetograms.

Four out of five regions with X-class flares show a significant change in the helicity change rate, while none of the five active regions with an associated M-class flare shows this behavior. We determine the location of the helicity change in the active regions and discuss possible causes. We also investigate active regions with no flare activity to determine the fluctuations of the helicity change rate due to instrumental effects. Title: High-Spatial Resolution Observations of Flow Fields in Solar Active Region NOAA 10486 Authors: Yang, G.; Xu, Y.; Cao, W.; Wang, H.; Denker, C.; Rimmele, T. R. Bibcode: 2004AAS...204.0210Y Altcode: 2004BAAS...36..669Y We present high-spatial resolution observations of proper motions in solar active region NOAA 10486 using the newly developed high-order adaptive optics (AO) system at the Dunn Solar Telescope (DST) of the National Solar Observatory/Sacramento Peak (NSO/SP) on 2003 October 29. The images were obtained with high-order AO, frame selection, and speckle masking image reconstruction. We analyze a two hour time series with 1-minute cadence in the context of an X10 white-light flare. Local correlation tracking (LCT) was used to measure the horizontal proper motions in the photosphere and relate them to the strong shear observed in the magnetic field configuration. Title: Characteristic evaluation of a near-infrared Fabry-Perot filter for the InfraRed Imaging Magnetograph (IRIM) Authors: Cao, Wenda; Denker, Carsten J.; Wang, Haimin; Ma, J.; Qu, M.; Wang, Jinshan; Goode, Philip R. Bibcode: 2004SPIE.5171..307C Altcode: The InfraRed Imaging Magnetograph (IRIM) is a high temporal resolution, high spatial resolution, high spectral resolving power, and high magnetic sensitivity solar two-dimensional narrow-band spectro-polarimeter working in the near infrared from 1.0 μm to 1.7 μm at Big Bear Solar Observatory (BBSO). It consists of an interference filter, a polarization analyzer, a birefringent filter, and a Fabry-Perot etalon. As the narrowest filter of IRIM, the infrared Fabry-Perot plays a very important role in achieving the narrow band transmission of ~ 10 pm and high throughput between 85% and 95% for the full wavelength range, maintaining wavelength tuning ability from 1.0 to 1.7 μm, and assuring stability and reliability. As the third of a series of publications describing IRIM, this paper outlines a set of methods to evaluate the near infrared Fabry-Perot etalon. Two-dimensional characteristic maps of the near infrared Fabry-Perot etalon, including the bandpass ▵λ, effective finesse Feff, peak transmission τmax, along with a free spectral range, flatness, roughness, and stability and repeatability were obtained with laboratory equipment. These measured results will benefit the optimization of IRIM design and observational mode of the future. Title: Imaging Spectropolarimetry of Ti I 2231 nm in a Sunspot Authors: Penn, M. J.; Cao, W. D.; Walton, S. R.; Chapman, G. A.; Livingston, W. Bibcode: 2003SoPh..215...87P Altcode: Spectro-polarimetric observations at 2231 nm were made of NOAA 10008 near the west solar limb on 29 June 2002 using the National Solar Observatory McMath-Pierce Telescope at Kitt Peak and the California State University Northridge - National Solar Observatory infrared camera. Scans of spectra in both Stokes I and Stokes V were collected; the intensity spectra were processed to remove strong telluric absorption lines, and the Stokes V umbral spectra were corrected for instrumental polarization. The sunspot temperature is computed using the continuum contrast and umbral temperatures down to about 3700 K are observed. A strong Ti i line at 2231.0 nm is used to probe the magnetic and velocity fields in the spot umbra and penumbra. Measurements of the Ti i equivalent width versus plasma temperature in the sunspot agree with model predictions. Zeeman splitting measurements of the Stokes I and Stokes V profiles show magnetic fields up to 3300 G in the umbra, and a dependence of the magnetic field on the plasma temperature similar to that which was seen using Fe i 1565 nm observations of the same spot two days earlier. The umbral Doppler velocity measurements are averaged in 16 azimuthal bins, and no radial flows are revealed to a limit of ± 200 m s−1. A Stokes V magnetogram shows a reversal of the line-of-sight magnetic component between the limb and disk center sides of the penumbra. Because the Ti i line is weak in the penumbra, individual spectra are averaged in azimuthal bins over the entire penumbral radial extent. The averaged Stokes V spectra show a magnetic reversal as a function of sunspot azimuthal angle. The mean penumbral magnetic field as measured with the Stokes V Zeeman component splitting is 1400 G. Several weak spectral lines are observed in the sunspot and the variation of the equivalent width versus temperature for four lines is examined. If these lines are from molecules, it is possible that lines at 2230.67, 2230.77, and 2231.70 nm originate from OH, while the line at 2232.21 nm may originate from CN. Title: Weak Infrared Molecular Lines Reveal Rapid Outflow in Cool Magnetic Sunspot Penumbral Fibrils Authors: Penn, M. J.; Cao, W. D.; Walton, S. R.; Chapman, G. A.; Livingston, W. Bibcode: 2003ApJ...590L.119P Altcode: New imaging spectropolarimetric observations of the Evershed flow in sunspot penumbrae using weak infrared molecular absorption lines are presented. A plane-polar coordinate system in the sunspot frame is defined, allowing averaging of many raw spectra. Molecular lines show Doppler shifts implying typical horizontal outflow speeds of 6 and up to 9 km s-1. The Ti I polarimetric spectra show the same rapid outflow and suggest an average penumbral magnetic field strength of 1400 G. While these observations show Doppler shifts of the entire line profile, the velocities are in better agreement with previous measurements from spectral line asymmetries. Title: Weak IR Lines Reveal Rapid Outflow in Cool Magnetic Penumbra Authors: Penn, M. J.; Cao, W. D.; Walton, S. R.; Chapman, G. A.; Livingston, W. Bibcode: 2003SPD....34.1106P Altcode: 2003BAAS...35..827P New imaging spectropolarimetric observations of the Evershed flow in sunspot penumbrae using weak infrared molecular absorption lines are presented. A plane-polar coordinate system in the sunspot frame is defined, allowing averaging of many raw spectra. Molecular lines show Doppler shifts implying typical horizontal outflow speeds of 6 to 9 km/sec. The Ti I polarimetric spectra show the same rapid outflow and suggest an average penumbral magnetic field strength of 1400 Gauss. While these observations show Doppler shifts of the entire line profile the velocities are in better agreement with previous measurements from spectral line asymmetries. Title: High-Resolution Infrared Filter System for Solar Spectroscopy and Polarimetry Authors: Cao, W.; Ma, J.; Wang, J.; Goode, P. R.; Wang, H.; Denker, C. Bibcode: 2003SPD....34.2013C Altcode: 2003BAAS...35..846C We report on the design of an imaging filter system working at the near infrared (NIR) of 1.56 μ m to obtain monochromatic images and to probe weak magnetic fields in different layers of the deep photosphere with high temporal resolution and spatial resolution at Big Bear Solar Observatory (BBSO). This filter system consists of an interference filter, a birefringent filter, and a Fabry-Pérot etalon. As the narrowest filter system, the infrared Fabry-Pérot plays an important role in achieving narrow band transmission and high throughput, maintaining wavelength tuning ability, and assuring stability and reliability. In this poster, we outline a set of methods for the evaluation and calibration of the near infrared Fabry-Pérot etalon. Two-dimensional characteristic maps of the near infrared Fabry-Pérot etalon, including full-width-at-half-maximum (FWHM), effective finesse, peak transmission, along with free spectral range, flatness, roughness, stability and repeatability were obtained with lab equipments. Finally, by utilizing these results, a detailed analysis of the filter performance for the Fe I 1.5648 μ m and Fe I 1.5652 μ m Zeeman sensitive lines is presented. These results will benefit the design of NIR spectro-polarimeter of Advanced Technology Solar Telescope (ATST). Title: Design of Achromatic Waveplates for ATST Near IR Filter System Authors: Ma, J.; Wang, J.; Cao, W.; Denker, C.; Wang, H. Bibcode: 2003SPD....34.2024M Altcode: 2003BAAS...35R.848M Achromatic waveplates play one of the central roles in constructing universal birefringent filters (UBF). Although it's been developed very well by several authors in the last decades, the mechanisms and detailed techniques which can realize the achromatism are still not clearly categorized. Such waveplates for Infrared do not exist yet. In the recent development of a InfraRed High Resolution Magnetograph at BBSO, it is realized that a standard approach of designing achromatic waveplate is needed not only for the IRHRM, but more importantly, for the Near IR Tunable Filter for ATST.

There are several theoretical methods which are available to describe the behavior of waveplates and polarization status of field, including algebraic tools (Jones Algebra, Muler Matrix, Stokes Vector), and geometrical approach (Poincere Sphere, which is Complex Analysis in fact). By using these methods, it can be proved that a combination of waveplates could have much better achromatic performance than a single component has.

Since the simulation of the combination of waveplates gets more and more complex, a computer program software package for designing achromatic waveplates is developed. Compared to the most popular commercial software package, such as ZEMAX which uses ray-tracing approach, the recently developed software tools is based on Transfer Functions of Optical Systems, which will be more efficient than ray-tracing approach. Title: Stokes polarimetry at near-infrared 1.56 um for solar observation Authors: Cao, Wenda; Ye, Binxun; Wang, Dongguang; Song, Qian Bibcode: 2002SPIE.4480..176C Altcode: FeI 1.56 micrometers Zeeman-sensitive lines are very important and potential to measure the magnetic field of the deepest layer of the solar photosphere. The new generation polarimeter is designed and manufactured in this wavelength range. By use of the polarimeter mounted on the vertical spectrograph of the 2m solar telescope at Kitt Peak, we can observe the Stokes I, Q, U, Vv parameters simultaneously. The paper presents the introduction of the near infrared polarimeter and the polarmetry of a sunspot group. Title: The Primary Design of A 1-Meter Infrared Solar Telescope Authors: Cao, W. D.; Liu, Z.; Ye, B. X. Bibcode: 2002stma.conf...75C Altcode: No abstract at ADS Title: Design concepts of EUV telescopes and the detectors boarded on the Solar Space Telescope Authors: Song, Qian; Ye, Binxun; Cao, Jianlin; Chen, Bo; Cao, Wenda Bibcode: 2001SPIE.4498..335S Altcode: The Solar Space Telescope (SST) is the largest scientific space project of China up to now. It engages to observe the transient and steady state solar hydrodynamic and magneto-hydrodynamic process over 2-D real time polarizing spectrum, UV, X-ray and H(alpha) image, and continuous time evolution with high spatial and temporal resolution in order to achieve a break through advance in solar physics. The EUV part of SST, the EUV telescope (EUT), consists of four telescopes with their detectors, which are parallel situated in a single telescope tube. Each telescope of the EUT adopts the normal-incidence principle with help of the multilayer technology and the primary mirror diameter is 12cm. The detectors of the EUT are constructed with EUV sensitive phosphors, fiber tapers, image intensifiers, CCDs, camera electronics and cooling blocks. Three telescopes of EUT are designed to achieve a spatial resolution of 0.5 arcsecond with a field of view (FOV) of 8.5'x8.5' in order to get the ever high-resolution image of the fine structure of the high temperature activities in solar corona and the fourth one is 85'x85' to have the full solar disk always in its field of view. In our presentation, the scientific objectives and the configuration of EUT are introduced. Title: The Observation and Study of Two Prominence Events in the Infrared Authors: Cao, W. D.; Ye, B. X.; Livingston, W. Bibcode: 2001IAUS..203..257C Altcode: This paper reports the infrared observation of two prominence events on Jan. 8, 1999 and Feb. 9, 1999 at H Paschen β 12818Å, H Bracket α 40512Å, and H Pfund β 46525Å using the McMath Telescope. We scanned the spectrograph slit across the prominences parallel to the solar limb to obtain three-dimensional data cubes (two spatial dimensions and one spectral dimension). By fitting these observed lines, we can directly determine some important physical parameters such as Doppler width, the optical thickness at line center, and the line displacement. Combined with simultaneous observation of Balmer Hα, Hβ, and K lines, the new results of structure and dynamics of limb prominence are presented. These results imply that these infrared lines can penetrate through the prominence and become the potential probe and tool of them, while Hα and Hβ sense the prominence skin only. Title: Simulation and Observation of Solar FeI 1.56 μm Line using PtSi Array Camera Authors: Cao, W.; Song, Q.; Ye, B. Bibcode: 2001ASPC..236..281C Altcode: 2001aspt.conf..281C No abstract at ADS Title: PtSi IRFPA camera and its application in infrared solar spectrum observation Authors: Cao, Wenda; Ye, Binxun; Song, Qian; He, J.; Zhou, X. D.; Ji, Kaifan Bibcode: 2000SPIE.4008..806C Altcode: Although the interest in PtSi IR focal pane array has waned due to its low quantum efficiency compared with InSb and HgCdTe arrays, it is very potential in observing brighter celestial objects. We explored the possibility of applying it to the observation of IR solar spectrum. In the paper, the methods of the simulation and calibration in our observation are introduced and discussed in detail. Using this kind of camera, a new observational band is added to the 2D Multi-band Solar Spectrograph at Yunnan Observatory. The dispersion for FeI 1.56 micrometers of the new IR solar spectrograph is 0.0722 angstrom per pixel, and each vertical pixel represents 0.51 inch of solar disk. It is specially suitable for 2D spectroscopic observation of the deepest solar photosphere. Some primary observation results are also presented. Title: Simultaneous remote observation from six sites organized at the 1-m telescope of the Yunnan Observatory Authors: Cao, Wenda; Song, Qian; Ji, Kaifan Bibcode: 2000SPIE.4011..117C Altcode: On Mar. 6-7, 1997, a simultaneous remote observation from 6 sites was successfully carried out with the cooperation of astronomers and hobbyists in China, United States, Canada, and Great Britain. In the paper, the process and technical methods in this observation are introduced in detail. The present difficulties and brilliant prospects in the observational method under the current circumstances of Internet in China are shown as well. Title: A research on the detectors for solar spectrographs. Authors: Cao, Wenda; Ji, Kaifan; Song, Qian Bibcode: 2000AcASn..41...93C Altcode: The selection and application of detectors for a solar spectrograph described in this paper are more or less different from those in other works. For use at the solar spectrograph of Yunnan Observatory, the authors have built a model to estimate the spectral fluxes of solar spectrograph with computer and confirmed the result with observations. The spectral fluxes in visible and near infrared bands were calculated for the same spectrograph. Based on these results, the authors have discussed the detectors in details and summed up the processes in observation where some additional comments are needed. Title: Simulation and observation of near infrared solar Fe I 1.56 μm line. Authors: Cao, Wenda; Song, Qian; Ji, Kaifan Bibcode: 1999ArBei..34...60C Altcode: The infrared focal plane array (IRFPA) with large size and high quantum efficiency is very difficult to acquire. On Jan. 29 - 30, 1999, the authors utilized PtSi IRFPA to observe the infrared solar Fe I 1.56 μm line. The simulation and observation for this experiment are introduced in detail. Title: Radiation damage on CCDs in space environment. Authors: Song, Qian; Cao, Wenda; Ji, Kaifan Bibcode: 1999ArBei..34...67S Altcode: The energetic radiation existing in the space natural radiation environment may cause damages to charge-coupled devices (CCDs) working in space and degrade their performance. In this paper, the mechanism of the CCD's radiation damage is reviewed and an interpretation is attempted for the radiation-caused performance defects of the Solar-A SXT CCD with the flat-band shift resulted from the trapped holes within the insulator layer between gates and silicon bulk. Title: Laboratory evaluation of CCD for astronomical application. Authors: Song, Qian; Ji, Kaifan; Cao, Wenda Bibcode: 1999AcApS..19..333S Altcode: The method of evaluating charge-coupled device for astronomical application used in Yunnan Observatory CCD-testing Laboratory is presented. The parameters evaluated include linearity, noise, gain quantum efficiency and transfer efficiency. Title: Silicon CCD optimized for NIR wavelengths. Authors: Song, Qian; Ji, Kaifan; Cao, Wenda Bibcode: 1999PYunO...4...60S Altcode: CCDs processed on typical substrates exhibit low NIR QE. Because the relatively thin epitaxial layer allows a high percentage of long wavelength photons to pass through and the reflection loss of back surface is high. A thick epitaxial layer allows the longer wavelength photons to be absorbed into the epitaxial layer where the resultant electrons generated will be collected in the potential wells. The drawback of processing with this method is a resultant degradation of carrier diffusion MTF. Increasing the depleted region under each gate, which can be realized by using high resistivity substrates, can enhance MTF. A new kind of CCD fabricated on high resisitivity silicon at Lick Observatory has superior red performance beyond 800 nm wavelength. The application of thin film AR coating directly on to the CCD back surface can significantly reduce reflection loss from UV to NIR and greatly decrease interference fringing on back illuminated CCDs. Title: Calculation of spectral fluxes for the solar spectrograph of Yunnan Observatory. Authors: Cao, Wenda; Ji, Kaifan; Song, Qian Bibcode: 1999PYunO...4...53C Altcode: For the solar spectrograph of Yunnan Observatory, a computer model to estimate the spectral fluxes is set up and is verified by the authors' observations. The spectral fluxes are calculated. In view of these results, the plan of the detectors for the Solar Spectrograph is suggested. Title: An Interpretation of a Radiation Damage Phenomenon of the solar-A CCD Authors: Song, Qian; Cao, Wenda Bibcode: 1999oaaf.conf..139S Altcode: : The Yohkoh satellite for the Japanese Solar-A Mission was launched in 1991. There were some unexpected darkened spots on the recent images took by the Soft X-ray Telescope (SXT) boarded on. The images were took by a CCD camera utilized a 1024x1024 virtual phase CCD. CCDs used in space are subjected to natural radiation environments that may cause permanent damages on them and degrade their performance. In this paper, an interpretation by CCD radiation damage theory was attempted and a computer-simulated result was calculated. Title: Model of Spectral Fluxes for Solar Spectrograph Authors: Cao, Wenda; Song, Qian Bibcode: 1999oaaf.conf..400C Altcode: Taking use of the solar spectrograph in Yunnan Observatory, we built a model to estimate the spectral fluxes of solar spectrograph with computer and confirmed the result by observations. The spectral fluxes in visible and near infrared bands were calculated for the solar spectrograph of Yunnan Observatory. Based on the results, we made a suggestion of the detectors for solar spectrograph and summed out the processes in observation where the additional attention should be needed. Title: Methods for blue enhancement of CCDs. Authors: Ji, Kaifan; Song, Qian; Cao, Wenda Bibcode: 1999PYunO...3...50J Altcode: CCDs have become the most important astronomical detector for UV, visible and NIR imaging and spectroscopy at most observatories throughout the world. But the quantum efficiencies (QE) in the blue region of general CCDs are very low. Increasing the sensitivity in this region is desirable when the CCDs are used in astronomy. There are two ways to improve QEs of frontside illuminated CCDs. Deposition of a very thin polysilicon gate allows transmittance of shorter wavelength photons, and frontside coating a completed device with lumogen absorbs lower wavelength photons and re-emits them near the peak sensitivity of the CCD. After optimizing, 100% QE enhancement may be realized at UV band. Title: Easy way to evaluate CCDs for astronomical use Authors: Song, Qian; Ji, Kaifan; Cao, Wenda Bibcode: 1998SPIE.3553..291S Altcode: The methods of evaluating the astronomy-using CCDs in Yunnan Observatory CCD-testing Lab are introduced, concerning the evaluation of linearity, noise, gain, quantum efficiency and transfer efficiency, etc. Title: Near infrared focal plane arrays for astronomy. Authors: Cao, Wenda; Ye, Binxun Bibcode: 1998PABei..16..103C Altcode: Developments in infrared focal plane arrays are summarized. InSb, HgCdTe, and PtSi near-infrared focal plane arrays are introduced and combined with the plan of the infrared solar tower in China, their features are compared in detail. Title: Two remote-presence observations at the 1-m telescope of the Yunnan Observatory in China Authors: Ji, Kaifan; Cao, Wenda; Ye, Binxun; Song, Q.; Chu, Y.; Chen, K.; Sun, J.; Sun, Y. S. Bibcode: 1998SPIE.3351...25J Altcode: Two remote presence observations on Dec. 25, 1995 and Mar. 7, 1997 were achieved at the 1-m telescope of Yunnan Observatory. In this paper, the observations are introduced in detail. The technical methods in the remote presence observation are also discussed under the current circumstances of hardware and software in China. The brilliant prospects of the observational method are shown as well. Title: Evidence for resonant absorption of VLF waves obtained at Zhongshan Station, Antarctica Authors: Tang, K. Y.; Peng, F. L.; Ning, Z. L.; Cao, W. Z.; Meng, Q. F.; Yang, Y. H.; Jiao, C. M. Bibcode: 1998mrat.conf...37T Altcode: Evidence for resonant absorption of VLF waves was obtained at Zhongshan Station, Antarctica. The L value for Zhongshan Station is about 14. Due to such high geomagnetic latitude, no whistlers were received, but a lot of VLF emissions have been recorded since the station was founded in 1990. The VLF emission recorded in Zhongshan Station are usually wide-band emission, from a few hundred Hz to about 15kHz. In February and June of 1993, we recorded two sets of VLF emissions never seen before. The main feature for the emission is a blank curve around 5kHz cut from the wide-band emissions. We explain these observations in term of resonant absorption of VLF waves by ions. Title: The test of the DALSA CA-D7-1024T CCD camera. Authors: Song, Qian; Liu, Weiwei; Ji, Kaifan; Cao, Wenda Bibcode: 1998PYunO...2...72S Altcode: From 2nd to 6th, Sep., 1996, the main detector of the balloon-borne solar telescope of the Beijing Observatory, DALSA CA-D7-1024T camera, was tested in the CCD - Testing Laboratory of Yunnan Observatory. The test revealed that despite some problems on the image-collecting system, the overall behavior of the camera is superb as a non-cooling detector. Title: International astronomical remote present observation on IRC. Authors: Ji, Kaifan; Cao, Wenda; Song, Qian Bibcode: 1998PYunO...2...67J Altcode: On March 6 - 7, 1997, an international astronomical remote present observation (RPO) was made on Internet Relay Chat (IRC) for the first time. Seven groups in four countries, China, United States, Canada and Great Britain, used the 1 meter telescope of Yunnan observatory together by the way of remote present observation. Within minutes, images were "On-line" by FTP, and every one was able to get them by anonymous ftp and discuss them on IRC from different widely separated sites. Title: Computer simulation for the observation of the 1.56 μm Fe I spectral line of solar magnetic field. Authors: Cao, Wenda; Ji, Kaifan; Song, Qian Bibcode: 1998PYunO...4...43C Altcode: It makes an interesting idea and work to use the IRFPA made in China and the solar spectrometer at Yunnan Observatory to probe into the local magnetic field on solar surface by the observation of NIR Fe I line at 1.56 μm. The computer simulation is presented. The influence of the apparatus effects and noises in the observation results are also discussed in detail. Title: RVC and Its Effect of Solar-terrestrial Physics Authors: Ji, S. C.; Wei, F. S.; Cao, W. D. Bibcode: 1998asct.conf..125J Altcode: No abstract at ADS Title: A remote-presenting observation at the 1 m telescope of Yunnan Observatory. Authors: Cao, Wenda; Ji, Kaifan; Song, Qian; Liu, Weiwei Bibcode: 1997PYunO...3...88C Altcode: With the development of techniques of the computer, communication, network, and data compress, the technique of remote-presenting observation is achieved at the 1 m telescope of Yunnan Observatory. Compared with the traditional observation, it has a lot of advantages. In this paper, the remote-presenting observation during Dec 26 - 27, 1995 is introduced in detail. Under the current circumstances of hardware and software in China, the technical methods and difficulties in the remote-presenting observation are discussed. Title: PI 1024 CCD of Yunnan Observatory. Authors: Ji, Kaifan; Song, Qian; Cao, Wenda Bibcode: 1997PYunO...4...63J Altcode: No abstract at ADS Title: WinView software and an application to image processing. Authors: Cao, Wenda; Huan, Zunxiang; Ji, Kaifan; Song, Qian Bibcode: 1997PYunO...2...75C Altcode: WinView is a high performance software package written specifically for the acquisition and analysis of images. Many sophisticated postprocessing options are available. These options are introduced in this paper. Title: Remote Real-Time Astronomical Observations on IRC Authors: Kaifan, Ji; Cao, W.; Song, Q.; Ye, B. Bibcode: 1997IAUJD..20E..11K Altcode: On March 6-7, 1997, remote real-time observations were successfully made by the cooperation of seven groups in China, the United States, Canada and Great Britain. BVy using the medium of FTP and the Internet Relay Chat (IRC) network, we were able to make astronomicaal observations, from widely separated geographical sites, with the 1m telescope of the observatory in China's Yunnan Province. Within minutes, images were on the Internet and everyone was able to view them and to communicate with each other, discussing the objectives, making decisions and having the team member at the observatory operate the controls to obtain the images we needed for later study and analysis. The important adavntage of this event is that all Internet connections were made through a local phone line connection. The long-distance connections were then routed through the free Internet communications, thus avoiding the extremely high cost of transcontinental long-distance telephone connections. Title: Laboratory Evaluations of a CCD System For the Balloon-borne Solar Telescope Authors: Song, Q.; Liu, W.; Ji, K.; Cao, W.; Huan, Z. Bibcode: 1997IAUJD..19E..49S Altcode: The CCD camera, DALSA/CA-D7-1024, which is a commercial CCD system, is selected as the main detector for the BAO's Balloon-borne Solar Telescope. The principal parameters were tested by the YNAO, CCD-Testing Laboratory in the early September, 1996. The equipment of the lab and the method of the evaluations are described in the Poster. Evaluations show that the overall behavior of the camera is superb among the non-cooling commercial CCD systems. Nevertheless, there are some flaws in the image-collecting system which must be solved before launch. Title: Some infared focal panel arrays applying in near infrared solar observation. Authors: Cao, Wenda; Song, Qian; Ji, Kaifan Bibcode: 1997PYunO...4...73C Altcode: The development course and structure of infrared focal plane arrays are summarized. Near-infrared focal plane arrays are introduced emphatically, and combined with the infrared solar tower plan at present, their features are compared in detail. Title: The computer network and software system for 1 meter telescope. Authors: Ji, Kaifan; Song, Qian; Cao, Wenda Bibcode: 1997PYunO...4...68J Altcode: No abstract at ADS Title: WinView and its usage on the 1 m telescope at Yunnan Observatory. Authors: Cao, Wenda; Ji, Kaifan; Song, Qian; Huan, Zunxiang Bibcode: 1997PYunO...1...76C Altcode: The WinView is a highly-efficient software package for image collecting and processing in astronomy. The essential functions and the usage of this package in astronomy are described in detail. Title: FITS BMP and SCR image formats and the transformations. Authors: Ji, Kaifan; Cao, Wenda; Song, Qian Bibcode: 1996PYunO...2...60J Altcode: The image formats - FITS, BMP and SCR - are introduced in detail. The FITS format has become a universal format in astronomy and can be supported by almost all the software packages in astronomical uses. Meanwhile the BMP format is widely used on personal computers and is supported by a large amount of PC softwares in displaying, progressing and printing. The SCR format is used in the Yunnan Observatory to implement CCD image collection on PCs. Therefore, it is important to realize the transformation among the three formats so that CCD images head and image data, and the critical part is to transform the high and low bits of the data. Title: The one-dimension centering algorithms of CCD image. Authors: Kaifan, J.; Song, Qian; Cao, Wenda Bibcode: 1996PYunO...4...69K Altcode: The digital centering algorithms with high resolution becomes more and more important in astrometry. The marginal distribution method is used to transform the two-dimensional stellar image to one-dimensional. From comparisons among four kinds of one-dimensional centering algorithms (Gaussian fit, modified moment, median and derivative search) it is shown that Gaussian fit ranks highest in resolution, then the modified moment, and derivative the lowest. But the Gaussian fit is too slow in the view of calculating speed. Therefore, modified moment is the best choise as a centering method which can meet both the high resolution and high efficiency demands. Title: Development and test of an operation gain amplifier with the solar radio telescope at 15 cm wavelengths. Authors: Ghen, Guoqiang; Cao, Wenda; Yang, Kaiping Bibcode: 1995PYunO...1...47G Altcode: The construction principle of the operation gain amplifier with the solar radio telescope at 15 cm wavelengths is introduced. The adjustment and the test for measurement results have been obtained. Title: Approaching to Internet. Authors: Ji, Kaifan; Song, Qian; Cao, Wenda Bibcode: 1995PYunO...3...62J Altcode: With help from Computer Network Center of Chinese Academy of Sciences (CNC) and Telecommunication Office of Kunming, the authors have built their e-mail system. The node computer named ROSE belonging to CNC is linked to Internet. Title: Carbon dioxide interactions with irradiance and temperature in potatoes Authors: Cao, W.; Tibbitts, T. W.; Wheeler, R. M. Bibcode: 1994AdSpR..14k.243C Altcode: 1994AdSpR..14..243C Separate controlled environment studies were conducted to determine the interaction of CO2 with irradiance and interaction of CO2 with temperature on growth of three potato cultivars. In the first study, an elevated CO2 concentration of 1000 μmol mol-1 and an ambient CO2 of 350 μmol mol-1 were maintained at the photosynthetic photon fluxes (PPF) of 17 and 34 mol m-2 d-1 with 12 h photoperiod, and at the PPF of 34 and 68 mol m-2 d-1 with 24 h photoperiod (400 and 800 μmol m-2 s-1 PPF at each photoperiod). Tuber and total dry weights of 90-day old potatoes were significantly increased with CO2 enrichment, but the CO2 stimulation was less with higher PPF and longer photoperiod. Shoot dry weight was affected more by photoperiod than by PPF and CO2 concentrations. The elevated CO2 concentration increased leaf CO2 assimilation rates and decreased stomatal conductance with 12 h photoperiod, but had only a marginal effect with 24 h photoperiod. In the second study, four CO2 concentrations of 500, 1000, 1500 and 2000 μmol mol-1 were combined with two air temperature regimes of 16 and 20°C under a 12 h photoperiod. At harvest, 35 days after transplanting, tuber and total dry weights of potatoes reached a maximum with 1000 μmol mol-1 CO2 at 16°C, but continued to increase up to 2000 μmol mol-1 CO2 at 20°C. Plant growth was greater at 20°C than at 16°C under all CO2 concentrations. At 16°C specific leaf weight increased substantially with increasing CO2 concentrations as compared to 500 μmol mol-1 CO2, but increased only slightly at 20°C. This suggests a carbohydrate build-up in the leaves at 16°C temperature that reduces plant response to increased CO2 concentrations. The data in the two studies indicate that a PPF of 34 mol m-2 d-1, 20°C temperature, and 1000-2000 μmol mol-1 CO2 produces optimal tuber yield in potatoes.

Current address: MD-RES, Kennedy Space Center, FL 32899. Title: Solid matrix and liquid culture procedures for growth of potatoes Authors: Tibbitts, T. W.; Cao, W. Bibcode: 1994AdSpR..14k.427T Altcode: 1994AdSpR..14..427T This report discusses the advantages and limitations of several different procedures for growth of potatoes for CELSS. Solution culture, in which roots and stolons are submerged, and aeroponic culture were not found useful for potatoes because stolons did not produce tubers unless a severe stress was applied to the plants. In detailed comparison studies, three selected culture systems were compared, nutrient film technique (NFT), NFT with shallow media, and pot culture with deep media. For the NFT and NFT plus shallow media, plants were grown in 0.3 m2 trays and for the deep medium culture, in 20 liter pots. A 1 cm depth of arcillite, a baked montmorillonite clay, was used as shallow media (NFT-arc). Peatvermiculite mixture was used to fill the pots for the deep media. Nutrient solution, modified half-strength Hoagland's was recirculated among the tray culture plants with pH automatically controlled at 5.5, and conductivity maintained ~ 1100 μS cm-1 by adding stock nutrients or renewing the solution. A separate nutrient solution was used to water the pot plants four times daily to excess and the excess was discarded. Plants of Norland cv. were utilized and transplanted from sterile-propagated stem cutting plantlets. The plants were grown for 66 days under 12 h photoperiod in a first study and grown for 54 days under 24 h photoperiod in a second study. Under both photoperiods, total plant growth was greater in NFT-arc than in either NFT or pot culture. Under 12 h photoperiod, tuber dry weight was 30% higher with NFT-arc, but 50% lower with NFT, than with pot culture. Under 24 h photoperiod, however, tuber dry weight in both NFT and NFT-arc was only 20% of that in pot culture. The NFT and NFT-arc produced a greater shoot growth and larger number of small tubers than pot culture, especially with 24 h photoperiod. It is concluded that there are serious limitations to the use of NFT alone for growth of potatoes in a CELSS system. These limitations can be minimized by using a modified NFT with a shallow layer of media, such as arcillite, yet additional work is needed to ensure high tuber production with this system under long photoperiods. Title: Some common characteristics of the basic components of the solar radio emission and confirmation of a fourth basic component. Authors: Ji, S. C.; Cao, W. D.; Chen, G. Q.; Yang, K. P. Bibcode: 1994A&A...286..588J Altcode: Our high time-resolution data observed with fast sampling radio telescopes in three periods were processed. It is found that there is a rapidly varying component (RVC) in the radio emission source on the Sun. After investigating some common characteristics of the basic components of the solar radio emission, we discover that RVC is different in nature from the known three basic components: the quiet Sun, the slowly varying component (SVC), and the radio burst. It has a character superimposed on the radio burst: short duration, high brightness temperature and small dimension. For this reason, it is presented as a fourth basic component. Up to now, we have observed five types of RVC. Among them four types can be confirmed, another is yet in dispute. Finally, the five categories of observational characteristics of RVC are given. Title: Solar radio type II burst in the corona and interplanetary medium. Authors: Cao, Wenda; Yang, Kaiping; Ghen, Guoqiang Bibcode: 1994PYunO...1...49C Altcode: No abstract at ADS Title: The frequency splitting phenomenon in type II solar radio bursts. Authors: Cao, Wenda; Chen, Guoqing; Yang, Kaiping Bibcode: 1994PYunO...2...11C Altcode: The frequency splitting phenomenon in type II solar radio bursts is introduced and its observational features and theoretical explanation are summarized. The numerous existing models on frequency splitting are discussed in detail. Title: Test of the intermediate frequency amplifier of the solar radio telescope at 2130 MHz. Authors: Chen, Guoqing; Cao, Wenda; Yang, Kaiping Bibcode: 1994PYunO...2...19C Altcode: The construction principle and the technical parameters of the intermediate frequency amplifier of the solar radio telescope at 2130 MHz at Yunnan Observatory are introduced. Some measurement results are presented. Title: Radio and soft X-ray investigation of the solar flares of February 4, 1986 Authors: Ji, Shuchen; Ding, Youji; Chen, Guoqiang; Cao, Wenda Bibcode: 1993Ap&SS.203..241J Altcode: In this paper, the 3B flare of February 4, 1986 is studied comprehensively. The escape electrons accelerated to 10 100 keV at the top of coronal loop are confirmed by III type bursts. The energetic electron beams moved downward trigger the eruptions in the low layer of solar atmosphere. The radio and soft X-ray bursts are interpreted, respectively, by the maser mechanism and evaporation effect. Finally, the important role of energetic electron beams in solar flares is pointed out. Title: Duration of the solar radio spike radiation at decimetric waves and milliseconds. Authors: Cao, Wenda; Ghen, Guoqiang; Yang, Kaiping Bibcode: 1993PYunO...3...24C Altcode: The duration of the solar radio milliseconds spike radiation is shortened with increasing frequency, which has been a puzzling problem for a long time. In this paper, according to the electron cyclotron maser excited by the electron beams of the hollow beam distribution associated with the type III bursts, the relation between the duration of the spike radiation and the characteristic frequency ratio with the wave growth rate is discussed in detail. It is concluded that at the different wavelength of the decimetric wave, the spike radiations are the different frequency harmonic waves and the correlative decrease of the duration appears with increasing frequency. Title: Improvement and test of a microwave noise generator. Authors: Ghen, Guoqiang; Yang, Kaiping; Cao, Wenda Bibcode: 1993PYunO...3...29G Altcode: The improvement and test of the calibration source (or the noise generator) of the solar radio telescope are briefly described. The construction principle and measured results are also presented. It is known through the operation that the improvement is a success and the desired results are achieved. Title: Solar radio decimetric spike radiation and metric radio bursts. Authors: Cao, Wenda Bibcode: 1992PYunO...3....8C Altcode: The millisecond spike events from Jan 1990 to Mar 1991 observed and recorded with the fast sampling radio telescopes at four frequencies at the Yunnan Observatory are analysed. With the data combined with those of the radio outbursts at the metric wave-band published by the Solar-Geophysical Data during this time, the various features of the millisecond spikes are given. The relation between the millisecond spikes and the solar radio bursts of types III, II and IV is also summarized.