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Unprecedented Fine Structure of a Solar Flare Revealed by the 1.6 m New Solar Telescope.

Jing J, Xu Y, Cao W, Liu C, Gary D, Wang H - Sci Rep (2016)

Bottom Line: 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).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.

View Article: PubMed Central - PubMed

Affiliation: Center For Solar-Terrestrial Research, New Jersey Institute of Technology, University Heights, Newark, NJ 07102-1982, USA.

ABSTRACT
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.

No MeSH data available.


Related in: MedlinePlus

Panel (a) an IRIS slit-jaw image obtained with the 2796 Å (Mg ii k) filter. The black line is the spectrograph slit. The dashed box marks the FOV of NST Hα images, and the solid box marks the FOV of panels (c,d). Panel (b) Doppler shifts and velocity of Mg ii k spectral line. Panels (c,d) the zoomed-in IRIS Mg ii k slit-jaw image and the NST Hα image, both have the same FOV and were taken almost at the same time. The brightenings are indicated with arrows. The Gaussian FWHM and ±3σ are provided.
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f7: Panel (a) an IRIS slit-jaw image obtained with the 2796 Å (Mg ii k) filter. The black line is the spectrograph slit. The dashed box marks the FOV of NST Hα images, and the solid box marks the FOV of panels (c,d). Panel (b) Doppler shifts and velocity of Mg ii k spectral line. Panels (c,d) the zoomed-in IRIS Mg ii k slit-jaw image and the NST Hα image, both have the same FOV and were taken almost at the same time. The brightenings are indicated with arrows. The Gaussian FWHM and ±3σ are provided.

Mentions: We also notice that small-scale bright footpoints (in and around a sunspot’s umbra) of coronal loops were previously detected with Interface Region Imaging Spectrograph (IRIS)44 in UV channels by Kleint et al.45. Those footpoints have a spatial FWHM of 0″.35–0″.7 (corresponding to ~250–500 km), and exhibit intermittent emission and bursts of strong Doppler red shifts with supersonic velocity up to 200 km s−1. There were no flares during that IRIS observation, and Kleint et al. attributed the cause of those bright footpoints to the impact of coronal rain on the transition region (TR). For the event presented here, we also search for such brightenings in IRIS slit-jaw images. However, due to the facts that the pixel scale of IRIS slit-jaw images (0″.17 pixel−1) is about 5 times larger than that of NST/VIS Hα images, and these small brightenings were embedded in the remnants of the flare emission, the search is very difficult. Only a few bright dots are identified in the IRIS image sequence in the near UV passband. These brightenings are of FWHM of ~900–1300 km and virtually coinciding in position, time and duration with those in the NST Hα images. One example is demonstrated in Fig. 7. Unfortunately the IRIS spectrograph slit did not cut though any brightenings. Although without the information on Doppler shifts of spectral lines we cannot fully verify it, it seems reasonable to suppose that the Hα brightenings revealed by this observation are chromospheric counterparts to the UV brightenings in the TR reported by Kleint et al.45. Compared to the previous IRIS observation, our observation captures the finer components in the deeper, cooler and more dense chromosphere during an M-class flare, and clearly demonstrates the cause-and-effect association between falling plasma and brightenings. Moreover, the brightenings following the path of the primary flaring ribbon makes this observation strikingly interesting and unique.


Unprecedented Fine Structure of a Solar Flare Revealed by the 1.6 m New Solar Telescope.

Jing J, Xu Y, Cao W, Liu C, Gary D, Wang H - Sci Rep (2016)

Panel (a) an IRIS slit-jaw image obtained with the 2796 Å (Mg ii k) filter. The black line is the spectrograph slit. The dashed box marks the FOV of NST Hα images, and the solid box marks the FOV of panels (c,d). Panel (b) Doppler shifts and velocity of Mg ii k spectral line. Panels (c,d) the zoomed-in IRIS Mg ii k slit-jaw image and the NST Hα image, both have the same FOV and were taken almost at the same time. The brightenings are indicated with arrows. The Gaussian FWHM and ±3σ are provided.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4829858&req=5

f7: Panel (a) an IRIS slit-jaw image obtained with the 2796 Å (Mg ii k) filter. The black line is the spectrograph slit. The dashed box marks the FOV of NST Hα images, and the solid box marks the FOV of panels (c,d). Panel (b) Doppler shifts and velocity of Mg ii k spectral line. Panels (c,d) the zoomed-in IRIS Mg ii k slit-jaw image and the NST Hα image, both have the same FOV and were taken almost at the same time. The brightenings are indicated with arrows. The Gaussian FWHM and ±3σ are provided.
Mentions: We also notice that small-scale bright footpoints (in and around a sunspot’s umbra) of coronal loops were previously detected with Interface Region Imaging Spectrograph (IRIS)44 in UV channels by Kleint et al.45. Those footpoints have a spatial FWHM of 0″.35–0″.7 (corresponding to ~250–500 km), and exhibit intermittent emission and bursts of strong Doppler red shifts with supersonic velocity up to 200 km s−1. There were no flares during that IRIS observation, and Kleint et al. attributed the cause of those bright footpoints to the impact of coronal rain on the transition region (TR). For the event presented here, we also search for such brightenings in IRIS slit-jaw images. However, due to the facts that the pixel scale of IRIS slit-jaw images (0″.17 pixel−1) is about 5 times larger than that of NST/VIS Hα images, and these small brightenings were embedded in the remnants of the flare emission, the search is very difficult. Only a few bright dots are identified in the IRIS image sequence in the near UV passband. These brightenings are of FWHM of ~900–1300 km and virtually coinciding in position, time and duration with those in the NST Hα images. One example is demonstrated in Fig. 7. Unfortunately the IRIS spectrograph slit did not cut though any brightenings. Although without the information on Doppler shifts of spectral lines we cannot fully verify it, it seems reasonable to suppose that the Hα brightenings revealed by this observation are chromospheric counterparts to the UV brightenings in the TR reported by Kleint et al.45. Compared to the previous IRIS observation, our observation captures the finer components in the deeper, cooler and more dense chromosphere during an M-class flare, and clearly demonstrates the cause-and-effect association between falling plasma and brightenings. Moreover, the brightenings following the path of the primary flaring ribbon makes this observation strikingly interesting and unique.

Bottom Line: 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).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.

View Article: PubMed Central - PubMed

Affiliation: Center For Solar-Terrestrial Research, New Jersey Institute of Technology, University Heights, Newark, NJ 07102-1982, USA.

ABSTRACT
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.

No MeSH data available.


Related in: MedlinePlus