58 research outputs found
Flame-like Ellerman Bombs and Their Connection to Solar UV Bursts
Ellerman bombs (EBs) are small-scale intense brightenings in H wing
images, which are generally believed to be signatures of magnetic reconnection
events 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 events, termed UV bursts, in the lower atmosphere.
Though previous observations have shown a clear coincidence of some UV bursts
and EBs, the exact relationship between these two phenomena is still under
debate. We investigate the spatial and temporal relationship between flame-like
EBs and UV bursts using joint near-limb observations between the 1.6--meter
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 these UV bursts and EBs are likely formed at different
heights during a common reconnection process.Comment: 5 figures; accepted by ApJ
Dark structures in sunspot light bridges
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 80200~km, 30\%50\%, and 0.31.2~km~s,
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 blue shift surrounded by narrow lanes of red
shift. 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.Comment: 6 figure
Microwave-Assisted Oxidation of Electrospun Turbostratic Carbon Nanofibers for Tailoring Energy Storage Capabilities
We report the systematic structural manipulation of turbostratic electrospun carbon nanofibers (ECNFs) using a microwave-assisted oxidation process, which is extremely rapid and highly controllable and affords controlled variation of the capacitive energy storage capabilities of ECNFs. We find a nonmonotonic relationship between the oxidation degree of ECNFs and their electrocapacitive performance and present a detailed study on the electronic and crystalline structures of ECNFs to elucidate the origin of this nonmonotonic relation. The ECNFs with an optimized oxidation level show ultrahigh capacitances at high operation rates, exceptional cycling performance, and an excellent energy–power combination. We have identified three key factors required for optimal energy storage performance for turbostratic carbon systems: (i) an abundance of surface oxides, (ii) microstructural integrity, and (iii) an appropriate interlayer spacing
Message-passing selection: Towards interpretable GNNs for graph classification
In this paper, we strive to develop an interpretable GNNs' inference
paradigm, termed MSInterpreter, which can serve as a plug-and-play scheme
readily applicable to various GNNs' baselines. Unlike the most existing
explanation methods, MSInterpreter provides a Message-passing Selection
scheme(MSScheme) to select the critical paths for GNNs' message aggregations,
which aims at reaching the self-explaination instead of post-hoc explanations.
In detail, the elaborate MSScheme is designed to calculate weight factors of
message aggregation paths by considering the vanilla structure and node
embedding components, where the structure base aims at weight factors among
node-induced substructures; on the other hand, the node embedding base focuses
on weight factors via node embeddings obtained by one-layer GNN.Finally, we
demonstrate the effectiveness of our approach on graph classification
benchmarks.Comment: 6 pages, 1 figure
Frequently Occurring Reconnection Jets from Sunspot Light Bridges
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-meter Goode Solar Telescope, we detect prevalent reconnection through
frequently occurring fine-scale jets in the H 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, 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 H 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.Comment: ApJ, 8 figure
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