884 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
Flare differentially rotates sunspot on Sun's surface
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
Selective gas detection using Mn3O4/WO3 composites as a sensing layer
Pure WO3 sensors and Mn3O4/WO3 composite sensors with different Mn concentrations (1 atom %, 3 atom % and 5 atom %) were successfully prepared through a facile hydrothermal method. As gas sensing materials, their sensing performance at different temperatures was systematically investigated for gas detection. The devices displayed different sensing responses toward different gases at specific temperatures. The gas sensing performance of Mn3O4/WO3 composites (especially at 3 atom % Mn) were far improved compared to sensors based on pure WO3, where the improvement is related to the heterojunction formed between the two metal oxides. The sensor based on the Mn3O4/WO3 composite with 3 atom % Mn showed a high selective response to hydrogen sulfide (H2S), ammonia (NH3) and carbon monoxide (CO) at working temperatures of 90 degrees C, 150 degrees C and 210 degrees C, respectively. The demonstrated superior selectivity opens the door for potential applications in gas recognition and detection
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