ABSTRACT With observations from the Interface Region Imaging Spectrograph, we track the complete evolution of ∼11 MK evaporation flows in an M1.1 flare on 2014 September 6 and an X1.6 flare on 2014 ...September 10. These hot flows, as indicated by the blueshifted Fe xxi 1354.08 line, evolve smoothly with a velocity decreasing exponentially from ∼200 km s−1 to almost stationary within a few minutes. We find a good correlation between the flow velocity and energy deposition rate as represented by the hard X-ray flux observed with the Reuven Ramaty High Energy Solar Spectroscopic Imager, or time derivative of the soft X-ray flux observed with the Geostationary Operational Environmental Satellites and the HINODE X-ray Telescope, which is in general agreement with models of nonthermal electron heating. The maximum blueshift of Fe xxi appears approximately at the same time as or slightly after the impulsive enhancement of the ultraviolet continuum and the Mg ii 2798.8 line emission, demonstrating that the evaporation flow is closely related to heating of the lower chromosphere. Finally, while the hot Fe xxi 1354.08 line is entirely blueshifted with no obvious rest component, cool chromospheric and transition region lines like Si iv 1402.77 are often not entirely redshifted but just reveal an obvious red wing enhancement at the ribbons, suggesting that the speed of chromospheric condensation might be larger than previously thought.
Recent IRIS observations have revealed a prevalence of intermittent small-scale jets with apparent speeds of
80
–
250
km
s
−
1
, emanating from small-scale bright regions inside network boundaries of ...coronal holes. We find that these network jets appear not only in coronal holes but also in quiet-sun regions. Using IRIS 1330 Å (C II) slit-jaw images, we extracted several parameters of these network jets,
e.g.
apparent speed, length, lifetime, and increase in foot-point brightness. Using several observations, we find that some properties of the jets are very similar, but others are obviously different between the quiet Sun and coronal holes. For example, our study shows that the coronal-hole jets appear to be faster and longer than those in the quiet Sun. This can be directly attributed to a difference in the magnetic configuration of the two regions, with open magnetic field lines rooted in coronal holes and magnetic loops often present in the quiet Sun. We also detected compact bright loops that are most likely transition region loops and are mostly located in quiet-Sun regions. These small loop-like regions are generally devoid of network jets. In spite of different magnetic structures in the coronal hole and quiet Sun in the transition region, there appears to be no substantial difference for the increase in footpoint brightness of the jets, which suggests that the generation mechanism of these network jets is very likely the same in both regions.
The High-Resolution Coronal Imager (Hi-C) Kobayashi, Ken; Cirtain, Jonathan; Winebarger, Amy R. ...
Solar physics,
11/2014, Letnik:
289, Številka:
11
Journal Article
Recenzirano
The
High-Resolution Coronal Imager
(Hi-C) was flown on a NASA sounding rocket on 11 July 2012. The goal of the Hi-C mission was to obtain high-resolution (≈ 0.3 – 0.4′′), high-cadence (≈ 5 seconds) ...images of a solar active region to investigate the dynamics of solar coronal structures at small spatial scales. The instrument consists of a normal-incidence telescope with the optics coated with multilayers to reflect a narrow wavelength range around 19.3 nm (including the Fe
xii
19.5-nm spectral line) and a 4096×4096 camera with a plate scale of 0.1′′ pixel
−1
. The target of the Hi-C rocket flight was Active Region 11520. Hi-C obtained 37 full-frame images and 86 partial-frame images during the rocket flight. Analysis of the Hi-C data indicates the corona is structured on scales smaller than currently resolved by existing satellite missions.
ABSTRACT The Interface Region Imaging Spectrograph (IRIS) reveals small-scale rapid brightenings in the form of bright grains all over coronal holes and the quiet Sun. These bright grains are seen ...with the IRIS 1330, 1400, and 2796 slit-jaw filters. We combine coordinated observations with IRIS and from the ground with the Swedish 1 m Solar Telescope (SST) which allows us to have chromospheric (Ca ii 8542 , Ca ii H 3968 , H , and Mg ii k 2796 ) and transition region (C ii 1334 , Si iv 1403 ) spectral imaging, and single-wavelength Stokes maps in Fe i 6302 at high spatial ( ), temporal, and spectral resolution. We conclude that the IRIS slit-jaw grains are the counterpart of so-called acoustic grains, i.e., resulting from chromospheric acoustic waves in a non-magnetic environment. We compare slit-jaw images (SJIs) with spectra from the IRIS spectrograph. We conclude that the grain intensity in the 2796 slit-jaw filter comes from both the Mg ii k core and wings. The signal in the C ii and Si iv lines is too weak to explain the presence of grains in the 1300 and 1400 SJIs and we conclude that the grain signal in these passbands comes mostly from the continuum. Although weak, the characteristic shock signatures of acoustic grains can often be detected in IRIS C ii spectra. For some grains, a spectral signature can be found in IRIS Si iv. This suggests that upward propagating acoustic waves sometimes reach all the way up to the transition region.
With observations from the Interface Region Imaging Spectrograph (IRIS), we track the complete evolution of \(\sim\)11 MK evaporation flows in an M1.1 flare on 2014 September 6 and an X1.6 flare on ...2014 September 10. These hot flows, as indicated by the blueshifted Fe~{\sc{xxi}}~1354.08\AA{}~line, evolve smoothly with a velocity decreasing exponentially from \(\sim\)200~km~s\(^{-1}\) to almost stationary within a few minutes. We find a good correlation between the flow velocity and energy deposition rate as represented by the hard X-Ray flux observed with the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI), or time derivative of the soft X-Ray flux observed with the Geostationary Operational Environmental Satellites (GOES) and the HINODE X-ray Telescope (XRT), which is in general agreement with models of nonthermal electron heating. The maximum blue shift of Fe~{\sc{xxi}}~appears approximately at the same time as or slightly after the impulsive enhancement of the ultraviolet continuum and the Mg~{\sc{ii}}~2798.8\AA{}~line emission, demonstrating that the evaporation flow is closely related to heating of the lower chromosphere. Finally, while the hot Fe~{\sc{xxi}}~1354.08\AA{} line is entirely blueshifted with no obvious rest component, cool chromospheric and transition region lines like Si~{\sc{iv}}~1402.77\AA{} are often not entirely redshifted but just reveal an obvious red wing enhancement at the ribbons, suggesting that the speed of chromospheric condensation might be larger than previously thought.
Recent IRIS observations have revealed a prevalence of intermittent small-scale jets with apparent speeds of 80 - 250 km s\(^{-1}\), emanating from small-scale bright regions inside network ...boundaries of coronal holes. We find that these network jets appear not only in coronal holes but also in quiet-sun regions. Using IRIS 1330A (C II) slit-jaw images, we extract several parameters of these network jets, e.g. apparent speed, length, lifetime and increase in foot-point brightness. Using several observations, we find that some properties of the jets are very similar but others are obviously different between the quiet sun and coronal holes. For example, our study shows that the coronal-hole jets appear to be faster and longer than those in the quiet sun. This can be directly attributed to a difference in the magnetic configuration of the two regions with open magnetic field lines rooted in coronal holes and magnetic loops often present in quiet sun. We have also detected compact bright loops, likely transition region loops, mostly in quiet sun. These small loop-like regions are generally devoid of network jets. In spite of different magnetic structures in the coronal hole and quiet sun in the transition region, there appears to be no substantial difference for the increase in foot-point brightness of the jets, which suggests that the generation mechanism of these network jets is likely the same in both regions.
We present a statistical study of prominence and filament eruptions observed by the Atmospheric Imaging Assembly (AIA) aboard the Solar Dynamics Observatory (SDO). Several properties are recorded for ...904 events that were culled from the Heliophysics Event Knowledgebase (HEK) and incorporated into an online catalog for general use. These characteristics include the filament and eruption type, eruption symmetry and direction, apparent twisting and writhing motions, and the presence of vertical threads and coronal cavities. Associated flares and white-light coronal mass ejections (CME) are also recorded. Total rates are given for each property along with how they differ among filament types. We also examine the kinematics of 106 limb events to characterize the distinct slow- and fast-rise phases often exhibited by filament eruptions. The average fast-rise onset height, slow-rise duration, slow-rise velocity, maximum field-of-view (FOV) velocity, and maximum FOV acceleration are 83 Mm, 4.4 hours, 2.1 km/s, 106 km/s, and 111 m/s^2, respectively. All parameters exhibit lognormal probability distributions similar to that of CME speeds. A positive correlation between latitude and fast-rise onset height is found, which we attribute to a corresponding negative correlation in the average vertical magnetic field gradient, or decay index, estimated from potential field source surface (PFSS) extrapolations. We also find the decay index at the fast-rise onset point to be 1.1 on average, consistent with the critical instability threshold theorized for straight current channels. Finally, we explore relationships between the derived kinematics properties and apparent twisting motions. We find that events with evident twist have significantly faster CME speeds and significantly lower fast-rise onset heights, suggesting relationships between these values and flux rope helicity.
The Interface Region Imaging Spectrograph (IRIS) reveals small-scale rapid brightenings in the form of bright grains all over coronal holes and the quiet sun. These bright grains are seen with the ...IRIS 1330 \AA, 1400 \AA\ and 2796 \AA\ slit-jaw filters. We combine coordinated observations with IRIS and from the ground with the Swedish 1-m Solar Telescope (SST) which allows us to have chromospheric (Ca II 8542 \AA, Ca II H 3968 \AA, H\alpha, and Mg II k 2796 \AA), and transition region (C II 1334 \AA, Si IV 1402) spectral imaging, and single-wavelength Stokes maps in Fe I 6302 \AA at high spatial (0.33"), temporal and spectral resolution. We conclude that the IRIS slit-jaw grains are the counterpart of so-called acoustic grains, i.e., resulting from chromospheric acoustic waves in a non-magnetic environment. We compare slit-jaw images with spectra from the IRIS spectrograph. We conclude that the grain intensity in the 2796 \AA\ slit-jaw filter comes from both the Mg II k core and wings. The signal in the C II and Si IV lines is too weak to explain the presence of grains in the 1300 and 1400 \AA\ slit-jaw images and we conclude that the grain signal in these passbands comes mostly from the continuum. Even though weak, the characteristic shock signatures of acoustic grains can often be detected in IRIS C II spectra. For some grains, spectral signature can be found in IRIS Si IV. This suggests that upward propagating acoustic waves sometimes reach all the way up to the transition region.
The physical processes causing energy exchange between the Sun's hot corona and its cool lower atmosphere remain poorly understood. The chromosphere and transition region (TR) form an interface ...region between the surface and the corona that is highly sensitive to the coronal heating mechanism. High resolution observations with the Interface Region Imaging Spectrograph (IRIS) reveal rapid variability (about 20 to 60 seconds) of intensity and velocity on small spatial scales at the footpoints of hot dynamic coronal loops. The observations are consistent with numerical simulations of heating by beams of non-thermal electrons, which are generated in small impulsive heating events called "coronal nanoflares". The accelerated electrons deposit a sizable fraction of their energy in the chromosphere and TR. Our analysis provides tight constraints on the properties of such electron beams and new diagnostics for their presence in the nonflaring corona.
Background
Male patients undergoing bariatric surgery have (historically) been considered higher risk than females. The aim of this study was to examine the disparity between genders undergoing ...laparoscopic sleeve gastrectomy (SG) and laparoscopic Roux-en-Y gastric bypass (RYGB) procedures and assess gender as an independent risk factor.
Methods
The MBSAQIP® Data Registry Participant User Files for 2015–2017 was reviewed for patients having primary SG and RYGB. Patients were divided into groups based on gender and procedure. Variables for major complications were grouped together, including but not limited to PE, stroke, and MI. Univariate and propensity matching analyses were performed.
Results
Of 429,664 cases, 20.58% were male. Univariate analysis demonstrated males were older (46.48 ± 11.96 vs. 43.71 ± 11.89 years,
p
< 0.0001), had higher BMI (46.58 ± 8.46 vs. 45.05 ± 7.75 kg/m
2
,
p
< 0.0001), and had higher incidence of comorbidities. Males had higher rates of major complications (1.72 vs. 1.05%;
p
< 0.0001) and 30-day mortality (0.18 vs. 0.07%,
p
< 0.0001). Significance was maintained after subgroup analysis of SG and RYGB. Propensity matched analysis demonstrated male gender was an independent risk factor for RYGB and SG, major complications 2.21 vs. 1.7%,
p
< 0.0001 (RYGB), 1.12 vs. 0.89%,
p
< 0.0001 (SG), and mortality 0.23 vs. 0.12%,
p
< 0.0001 (RYGB), 0.10 vs. 0.05%;
p
< 0.0001 (SG).
Conclusion
Males continue to represent a disproportionately small percentage of bariatric surgery patients despite having no difference in obesity rates compared to females. Male gender is an independent risk factor for major post-operative complications and 30-day mortality, even after controlling for comorbidities.
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