10+ Years of GST: Live Collection of Results(Downdload PDF) |
Solar Flares Triggered by Filament Evolution | |
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Original paper titled "Solar Flares Triggered by a Filament Peeling Process Revealed by High-resolution GST H-alpha Observations"
by Mancuso Mia, Jing Ju, Wang Haimin, and Cao Wenda was published in February 2025 issue of Astrophys. J. Lett., 980 L4 | |
How Small-scale Jets Evolve | |
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Original paper titled "Temporal Evolution of a Network Jet's Physical Properties Inferred from FISS/GST and IRIS Observations"
by Lim, Eun-Kyung, Chae, Jongchul, Cho, Kyuhyoun, Yurchyshyn, Vasyl, Yang, Heesu, Cho, Kyung-Suk, Kwak, Hannah, Song, Donguk, Madjarska, Maria S. was published in March 2025 issue of Astrophys. J., 981 185 | |
Death of a Sunspot | |
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Original paper titled "Transport of the magnetic flux away from a decaying sunspot via convective motions
” by Zheng, C., Roudier, T., Schmieder, B., Ruan, G., Malherbe, J.-M., Liu, Y., Chen, Y., Cao, W. was published in June 2023 issue of Astron. Astrophys., 686, id.A75 | |
Combining NIRIs and HMI data to Reveal Fine Details of Sunspots | |
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Original paper titled "Solar Chromospheric Network as a Source for Solar Wind Switchbacks” by Jeongwoo Lee, Vasyl Yurchyshyn, Haimin Wang, Xu Yang, Wenda Cao, and Juan Carlos Martínez Oliveros was published in August 2022 issue of Astrophys. J. Lett., 935, L27 | |
Focusing on the Nature of PSP Switchbacks | |
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Original paper titled "Solar Chromospheric Network as a Source for Solar Wind Switchbacks” by Jeongwoo Lee, Vasyl Yurchyshyn, Haimin Wang, Xu Yang, Wenda Cao, and Juan Carlos Martínez Oliveros was published in August 2022 issue of Astrophys. J. Lett., 935, L27 | |
Detecting 6 kG Strong Fields inside a Sunspot | |
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Original paper titled "Observations of Extremely Strong Magnetic Fields in Active Region NOAA 12673 Using GST Magnetic Field Measurement" by Lozitsky Vsevolod, Yurchyshyn Vasyl, Ahn Kwangsu, and Wang Haimin was published in March 2022 issue of Astrophys. J., 928, 41 | |
Jan 31, 2022: Flare emission/absorption in helium line 10830 at multiple spectral positions | |
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Original paper titled "Multi-passband Observations of a Solar Flare over the He I 10830Å line" by Yan Xu, Xu Yang, Graham S. Kerr, Vanessa Polito, Viacheslav M. Sadykov, Ju Jing, Wenda Cao, and Haimin Wang was published in January 2022 issue of Astrophys. J. Lett., 924/1, L18 (ADS) | |
Jan 30, 2022: Earth is reflecting less light. It's not clear if that's a trend | |
![]() See Press Release in ScienceNews
Original paper titled "Earth's Albedo 1998-2017 as Measured From Earthshine"
Phil R. Goode, Enric Pallé, Alla Shoumko, Sergey Shoumko, Pilar Montañes-Rodriguez, Steve E. Koonin was published in August 2021 issue of Geophys. Res. Lett., 48/71, e2021GL094888 (ADS) | |
Sept 10, 2020: Turbulent Magnetic Fields in Quiet Sun | |
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Original paper titled "Analysis of quiet-sun turbulence on the basis of SDO/HMI and Goode Solar Telescope data" by Valentina Abramenko and Vasyl Yurchyshyn was published in October 2020 issue of Monthly Notices of the Royal Astronomical Society, 497, Issue 4, 5405–5412 (ADS) | |
Apr 21, 2020: Physical Characteristics of Umbral Dots Derived from a High-Resolution Observations | |
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Original paper titled "Physical Characteristics of Umbral Dots Derived from a High-Resolution Observations" by Ali Kilcik, Volkan Sarp, Vasyl Yurchyshyn, Jean-Pierre Rozelot, and Atila Ozguc, was published in April 2020 issue of Solar Physics, 295/4, article id.58 (ADS) | |
Mar 4, 2020: Dynamic Type II Spicules may Result from Component Reconnection | |
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Original paper titled "Rapid Evolution of Type II Spicules Observed in Goode Solar Telescope On-disk Hα Images" by Vasyl Yurchyshyn, Wenda Cao, Valentina Abramenko, Xu Yang, and Kyung-Suk Cho, was published in March 2020 issue of Astrophysical Journal Letters, 891/1 (ADS) | |
Nov 15, 2019: Formation of solar spicules and subsequent coronal heating unveiled | |
![]() Their observations show that the dynamic interaction of magnetic fields with different polarities is responsible for the generation of many spicules. Spicules mostly originate from the boundaries of the so-called magnetic network (a grid-like pattern on the solar surface where the magnetic field is highly concentrated into vertical tubes). Bursts of spicules are often accompanied by the emergence of new magnetic elements near the spicule footpoints, where the newly emerging magnetic elements have a polarity opposite to the dominant polarity of the already existing magnetic network (see figure). Although small-scale magnetic flux emerges ubiquitously in the quiet Sun, only when it is close to the strong existing network fields (often within 3000 km) does it generate spicules (see the results summary movie). Magnetic flux cancellation (the decrease of magnetic flux with time when two opposite-polarity flux elements run into each other), a signature of magnetic field line reconnection, is clearly identified at the footpoints of some spicules.
Original paper titled "Generation of Solar Spicules and Subsequent Atmospheric Heating" by T. Samanta, H. Tian, V. Yurchyshyn, H. Peter, W. Cao, A. Sterling, R. Erdélyi, K. Ahn, S. Feng, D. Utz, D. Banerjee, Y. Chen, was published in November issue of Science, 366, 890 (ADS) | |
Sept 16, 2019: Plasma Vortices in the Sunspot Umbra | |
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Original paper titled "Vortex Formations and Its Associated Surges in a Sunspot Light Bridge" by Heesu Yang, Eun-Kyung Lim, Haruhisa Iijima, Vasyl Yurchyshyn, Kyung-Suk Cho, Jeongwoo Lee, Brigitte Schmieder, Yeon-Han Kim, Sujin Kim, and Su-Chan Bong was published in the Sept 16 2019 issue of the Astrophysical Journal (ADS) | |
Aug 5, 2019: High-resolution Observations of Dynamics of Superpenumbral H-alpha Fibrils | |
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Original paper titled "High-resolution Observations of Dynamics of Superpenumbral H-alpha Fibrils" by Ju Jing, Qin Li, Chang Liu, Jeongwoo Lee, Yan Xu, Wenda Cao, and Haimin Wang was published in the Aug 5 2019 issue of the Astrophysical Journal (ADS) | |
Apr 29, 2019: Ellerman Bomb Flames Fuel Solar Ultraviolet Bursts | |
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Original paper titled "Flame-like Ellerman Bombs and Their Connection to Solar Ultraviolet Bursts" by Yajie Chen, Hui Tian, Hardi Peter, Tanmoy Samanta, Vasyl Yurchyshyn, Haimin Wang, Wenda Cao, Linghua Wang and Jiansen He was published in the April 20 2019 issue of the Astrophysical Journal Letters (IOP ApJ Lett) | |
Mar 1, 2019: Warm Coronal Loops heated by Magnetic Cancellations | |
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Original paper titled "Magnetic Field Dynamics and Varying Plasma Emission in Large-scale Coronal Loops" by Seray Şahin, Vasyl Yurchyshyn, Pankaj Kumar, Ali Kilcik, Kwangsu Ahn, and Xu Yang was published in the March 1 2019 issue of Astrophysical Journal (ADS) | |
Jan 7, 2019: GST Detects Vector Field Changes Associated with Moving Flare Ribbons | |
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Original paper titled "Evolution of Photospheric Vector Magnetic Field Associated with Moving Flare Ribbons as Seen by GST" by Chang Liu, Wenda Cao, Jongchul Chae, Kwangsu Ahn, Debi Prasad Choudhary, Jeongwoo Lee, Rui Liu, Na Deng, Jiasheng Wang, and Haimin Wang was published in the December 7 2018 issue of Astrophysical Journal (IOP ApJ) | |
Sept 19, 2018: GST Sees New Structures in Sunspot Light Bridges | |
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Original paper titled "Dark Structures in Sunspot Light Bridges" by Jingwen Zhang, Hui Tian, Sami K. Solanki, Haimin Wang, Hardi Peter, Kwangsu Ahn, Yan Xu, Yingjie Zhu, Wenda Cao, Jiansen He, and Linghua Wang was published in the September 20 2018 issue of Astrophysical Journal (IOP ApJ) | |
Feb 15, 2018: Reconnection Jets inside a Sunspots | |
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Original paper titled "Frequently Occurring Reconnection Jets from Sunspot Light Bridges" by Hui Tian, Vasyl Yurchyshyn, Hardi Peter, Sami K. Solanki, Peter R. Young, Lei Ni, Wenda Cao, Kaifan Ji, Yingjie Zhu, Jingwen Zhang, Tanmoy Samanta, Yongliang Song, Jiansen He, Linghua Wang, Yajie Chen was published in the February 20 2018 issue of Astrophysical Journal (ADS/ArXiv) | |
Jan 12, 2018: GST Detects Very Strong Transverse Photospheric Magnetic Fields and Twist in a Light Bridge of Active Region NOAA 12673 | |
![]() Original paper titled "Strong Transverse Photosphere Magnetic Fields and Twist in Light Bridge Dividing Delta Sunspot of Active Region 12673" by Haimin Wang, Vasyl Yurchyshyn, Chang Liu, Kwangsu Ahn, Shin Toriumi, and Wenda Cao was published in the January 12 2018 issue of Research Notes of the AAS |
Jan 10, 2018: Transient Rotation of Photospheric Vector Magnetic Fields Associated with a Solar Flare | |
![]() Original paper titled "Transient rotation of photospheric vector magnetic fields associated with a solar flare" by Yan Xu, Wenda Cao, Kwangsu Ahn, Ju Jing, Chang Liu, Jongchul Chae, Nengyi Huang, Na Deng, Dale E. Gary & Haimin Wang was published in the January 3 2018 issue of Nature Communications. |
May 9, 2016: Mercury Transit Observed by the 1.6 m New Solar Telescope |
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January 15, 2015: NST and IRIS Look on a Pulsing Sunspot |
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Original paper titled "Dynamics in Sunspot Umbra as Seen in New Solar Telescope and Interface Region Imaging Spectrograph Data" by V. Yurchyshyn, A. Abramenko and A. Kilcik was published in January 10 2015 issue of Astrophysical Journal.
( ADS/ArXiv) |
June 2, 2014: Solving Sunspot Mysteries: Photospheric and Chromospheric Dynamics of Sunspots Observed with New Solar Telescope |
The results are presented by Alexander Kosovichev, Vasyl Yurchyshyn and Santiago Vargas Dominguez at the 224th meeting of the American Astronomical Society (AAS), held in Boston, Massachusetts on June 2, 2014. Link to the press-release materials.
Figure caption. Images of sunspot structure on the solar surface (top left) and at different heights above the surface (bottom row) obtained from the New Solar Telescope at Big Bear Solar Observatory (NJIT) on 29 September, 2013. The surface images show a dark central part (umbra) surrounded by filamentary penumbra, and an intrusion of hot plasma in the umbra ("light bridge"). The atmospheric images reveal fast plasma jets (bottom left), material accretion in the form of dense plasma sheets (second from the left) and very dynamic fibrils (two right panels). The sunspot activity is exceptionally strong in the "light bridge" area, above which the IRIS satellite detected sharply enhanced UV radiation (top right image). Image xredit: Santiago Vargas Dominguez & Alexander Kosovichev (BBSO/NJIT).
June 2, 2014: Discovering the Hidden Sources of Solar Surges: Small-Scale Magnetic Flux Emergence and Atmospheric Response Observed with New Solar Telescope, IRIS, SDO and Hinode. |
Figure caption. Cartoon illustrating the action of a six-thousand miles long magnetic flux rope rising up from the solar interior and stretching the granules. The interaction between the emerged and the ambient magnetic fields produces impulsive heating and an ejection of a plasma surge. Image credit: Santiago Vargas Dominguez (BBSO/NJIT)
May 29, 2014: Fine structure of flare ribbons and evolution of electric currents observed with NST and NASA's spacecraft |
Original paper titled "Fine Structure of Flare Ribbons and Evolution of Electric Currents" by I. N. Sharykin and A. G. Kosovichev was published in June 10 2014 issue of Astrophysical Journal Letters.
( ADS/ArXiv)
May 6, 2014: NST observations reveal fine structures inside of a dynamic umbra of solar spots |
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Recent observations of sunspot's umbra performed with the NST show that the sunspot's umbra is finely structured at a sub-arcsecond scale representing a mix of hot and cool plasma elements. Images and movies from NST's Visible Imaging Spectrometer reveal cool jet-like structures seen in the chromosphere of an umbra. The spikes are cone-shaped features with a typical height of 0.5-1.0Mm and a width of about 0.1Mm. Their life time ranges from 2 to 3 min and they tend to re-appear at the same location. The spikes are not associated with photospheric umbral dots and they rather tend to occur above darkest parts of the umbra, where magnetic fields are strongest. The spikes exhibit up and down oscillatory motions and their spectral evolution suggests that they might be driven by upward propagating shocks generated by photospheric oscillations. It is worth noting that triggering of the running penumbral waves seems to occur during the interval when the spikes reach their maximum height. |
Original paper titled "High Resolution Observations of Chromospheric Jets in Sunspot Umbra" by V. Yurchyshyn, V. Abramenko, A. Kosovichev, and P. Goode was published in May 20 2014 issue of Astrophysical Journal.
( ADS/ArXiv |
DOI)
Nov 27, 2012: Mini-Granulation on the Sun was observed with the New Solar Telescope at Big Bear |
New observations of the solar granulation with the New Solar Telescope (NST) at the Big Bear Solar Observatory (BBSO) allowed a NJIT-Stanford research team to make the next step in understanding of the solar surface structure. A new complex world of very small granules became visible between normal solar granules. Mini-granules, as small as Maine, form a multi-fractal structure, similar to other systems in nature, such as coast lines, glaciers, earthquakes, stock market, etc. A key property of such systems is their unpredictable, burst-like behavior and jagged, irregular shape. Usually, occurrence of numerous independent random processes lead to the formation of a such system. Studying of such systems is beneficial for understanding both the universe and the social life.
The image shows solar granulation acquired with the NST on August 3, 2010 with overplotted contours of detected mini-granules (structures of equivalent diameter less than 600 km). The image size is 20500x19000 km. A map of USA is overplotted for comparison.
Until now it was thought that solar convection produces convection cells, visible on the solar surface as granules, of characteristic (dominant) spatial scale of about 1000km and a Gaussian (normal) distribution of granule sizes. In this case, the mechanism that produces granules is "programmed" to churn up convection cells of a typical size, without much freedom in size variation. Mini-granules do not display any characteristic ("dominant") scale, their size distribution is continuous and can be described by a decreasing power law (Gaussian distribution does not work any longer here) across all scales ranging from 140 to 2000 km. A majority (about 80%) of mini-granules are smaller than 600 km and about 50% are smaller than 300 km in diameter. This non-Gaussian distribution of sizes implies that a much more sophisticated mechanism, with much more degrees of freedom may be at work, where any very small fluctuation in density, pressure, velocity and magnetic fields may have significant impact and affect the resulting dynamics.
Scientist for long time saw difference in properties of small and large granules. However, low contrast and spatial resolution did not allow scientists to explore the entire range of structures. The NST provides images with contrast twice that of the previous data. It also enables us to see features on the solar surface as small as 80~km. These capabilities allowed us for the first time to accurately detect and measure very small convection cells. Their existence and properties were a subject of debate for long time, and now the NST solves the puzzle of the small (mini) granules.
Original paper titled "Detection of small-scale granular structures in the quiet sun with the New Solar Telescope" by V. I. Abramenko, V.B. Yurchyshyn, P.R. Goode (Big Bear Solar Observatory, NJIT) and I.N. Kitiashvili, A.G. Kosovichev (Stanford University) will be published by Astrophysical Journal Letters at the end of August, 2012
These results were published in Sept 2012 issue of Astrophysical Journal Letters (ADS | Arxiv).
Oct 1, 2011: NST data reveal the regime of strong super-diffusivity on scales below 600 km |
We studied proper motion of bright points (BPs) visible in the quiet sun (QS), in a coronal hole (CH), and in an active region plage (ARP, figure above from left to right). By tracking the BPs we were able to measure their displacements as a function of time. (Examples of BP's tracks are shown in the figure below, left, where the blue dots mark the start point). We then calculated the average (over all BPs) displacement for each time interval to obtain the average squared displacement as a function of time (the displacement spectrum, see the blue spectrum in the figure below, right).
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Using Kolmogorov turbulence theory, we were able to relate the coefficient of turbulent diffusion to the displacement spectrum and its index gamma. We thus found that the coefficient of turbulent diffusion changes in direct proportion to both temporal and spatial scales, which is the textbook definition of super-diffusivity. The coefficient of turbulent diffusion plotted as a function of temporal and spatial scales is shown below (NST data is represented with solid green, blue and red lines). For comparison, data from previous studies are also shown.
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We also applied the same analysis to the 3D MHD model data of solar convection (Stein et al. 2007) and found the super-diffusion with gamma=1.45.
These results were published in Dec 2011 issue of Astrophysical Journal (ADS | Arxiv).
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Aug 12, 2011: Smallest Ever Jets are seen to Occur in the Lanes between Granules |
A small coronal hole (CH) located at N03E12 was observed using the NST with adaptive optics on August 31, 2010 from 17:40 to 18:16 UT. We used this data set to search for sources of small-scale intergranular jet-like events. We thus found that intergranular events are very often associated with rapidly evolving granules, more precisely, with instances in which granule fragments are pushed into the intergranular lane. A more detailed analysis of granular evolution led us to conclude that intergranular events are most often associated with what was identified by Steiner et al. (2010) as a vortex tube. At the same time, not every vortex tube event was accompanied by a chromospheric jet.
The Figure on the left shows a sequence of TiO images showing the development of a bright granular lane (BGL, arrow in 54:01 frame). The arrow in the first panel indicates a BGL, which slowly shifts toward the center of the granule as the lane evolves. The arrow in the 54:42 frame indicates a bright grain that usually accompanies the development of the BGL. The time stamp in each frame shows the minute and second of image acquisition, starting from 17:00:00~UT. Short tick marks separate 0.25~Mm spatial intervals.
At the peak of the BGL development, one or two jet-like darkenings, co-spatial with the BGL, may appear in the blue-shifted H-alpha images. These absorption features seem to originate in the intergranular lane adjacent to the bright grain.
Figure on the right shows a bright granular lane (BGL) associated with chromospheric activity. This is a sequence of composite images made by combining TiO granulation data and dark Ha-0.1~nm absorption features. The arrow in the 45:49 frame points toward the BGL. The onset of chromospheric jet-like activity begins shortly after a bright grain develops (frames 46:09-46:59). The arrow in the 48:17 frame indicates an inverted "Y" jet occurring at approximately the same position as the BGL. The time stamp in each frame shows the minute and second of image acquisition starting from 17:00:00~UT. Short tick marks separate 0.25 Mm spatial intervals.
Sequence of composite images showing the development of an elongated bright granular lane (BGL). The downward pointing arrows in the 59:02 and 00:24 frames indicate the BGL, while the upward pointing arrow marks the elongated bright grain. Two small and short-lived absorption features appear on either side of the grain between 18:03:39 and 18:04:40~UT. The time stamp in each frame shows the minute and second of image acquisition starting from 17:00:00~UT. Short tick marks separate 0.25 Mm spatial intervals, and the contour shapes in frames 03:18 - 03:39 show bright Ha-0.1nm patches.
According to the simulation data, the dark space between the bright grain and the BGL coincides with the axis of the vortex tube. The interpretation is that due to low pressure and temperature, the opacity above the vortex tube is reduced thus allowing us to peer deeper into its relatively cooler interior. As it follows from simulations, the associated magnetic field, is generally wrapped up in such a way, that the field is mainly aligned with the flow, i.e., it is rather perpendicular to the vortex tube axis. The high-speed flow above the vortex tube reaches up to the top of the photosphere with velocities up to 8~km/s and sweeps the magnetic field in the horizontal direction to the intergranular lane. It may be that this field collides with the nearby intergranular field of possibly opposing polarity, which has the potential to cause some chromospheric activity.
These results have been presented in August 2011 issue of ApJ Lett. 736/2, article id. L35 (2011), ( DOI: 10.1088/2041-8205/736/2/L35), (Bibliographic Code: 2011ApJ...736L..35Y)
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Dec 22, 2010: New NST data push the minimal size of the magnetic flux tubes down to 80km |
New high resolution data from NST established that these BPs could be much smaller then previously thought: the distribution function of their size extents down to the diffraction limit of NST, i.e., photospheric bright points can be even smaller than 80 km. The image on the left is an example of NST data and it shows solar granules with chains of small bright points between them. BPs usually cluster together at special locations on the solar surface where horizontal flows converge and sink, very much reminding the flow pattern at a street water drain.
Studies of BPs size and lifetime distributions are rather scanty. Earlier studies based on data from the Hinode space observatory reported a nearly Gaussian distribution of BP's size, with the peak located near 157 km.
Observations of solar granulation were performed with the NST's 1.6 meter clear aperture using a broadband TiO filter centered at a wavelength of 705.7 nm. The observations were made with tip-tilt and adaptive optics corrections and the data were speckle reconstructed.
To detect and track BPs, scientist created a tool that allowed them to automatically detect and track BPs in the NST images.
Two panels on the right show the same NST TiO image used to detect BPs with the image on the right overplotted with boundaries of detected BPs. This tool allowed scientists to measure size, lifetime, speed and the trajectory of each of BPs.
The six panel figure shows the probability distribution functions (PDFs) for
the diameter, D, lifetime, LT, and maximum intensity, Imax, of BPs.
In the left panels, results for two runs are shown: the black lines correspond
to the detection threshold of 85DN and the red lines to threshold of 120DN
(DN - Data Numbers). The right panels show PDFs only from the threshold of 85 DN.
The difference between the two runs is small: for higher threshold the relative number of large-size events slightly decreases, and the relative number of brighter events slightly increases. The lifetime distribution does not appear to be affected by the threshold at all.
The PDF of diameters displays a nearly linear behavior in the linear-logarithmic plot (upper left). The monotonous increase is present down to the diffraction limit of NST. The saturation and the turnover of the observed PDF at scales smaller than 77km (to the left from the dashed vertical line) might be caused either by the fact than the NST does not purely resolve elements smaller than 77 km, or that elements much smaller than 77 km do not exist. For comparison, in the same panel we show the BP size distribution as derived from Hinode/SOT G-band images by Utz et al. (2009). In spite of a drastic difference in the shape of the PDFs derived from the two instruments, physically, they are consistent. The Hinode PDFs also saturate at scales corresponding to the diffraction limit of the Hinode/SOT telescope, which is 157 km for SOT observations in the G-band.
We thus conclude that the real minimal size of magnetic BPs (or magnetic flux tubes) has not yet been detected in observations with modern high resolution telescopes. As to the maximum size of BPs, the upper boundary for it seems to exist: as soon as BPs defined as those located inside intergranular lanes, the diameter of BPs cannot be larger than characteristic width of the intergranular lanes, which varies in a range of 150-400 km.
We also find that BP size distribution function has a log-normal shape. Unlike the power law, the log-normal distribution is not scale-free, therefore, there is a limit on a minimal size of an elementary flux tube, which may not have been achieved yet. The log-normal nature of the size distribution implies that the fragmentation and merging processes are important mechanisms contributing into evolution and dynamics of BPs. Frequent fragmentation and coalescence are clearly visible in the data set movie4. About 98.6% of all BPs live less than 120 s (12 time steps). This remarkable fact was not obvious from previous studies because an extremely high time cadence was required. The most important point here is that these small and short living BPs significantly increase dynamics (flux emergence, collapse into BPs, and magnetic flux recycling) of unipolar network areas. The magnetic field is thus fragmented into flux concentrations with well defined interfaces between them known as current sheets. Random motions of BPs, as well as often appearance/disappearance of new flux concentrations, will change the spatial distribution of the current sheets thus leading to release of energy.
These results have been presented in December 2010 issue of ApJ Lett., 725, L101-L105