Optical Flash Research Articles

Protective effects of CY-09 and astaxanthin on NaIO3-induced photoreceptor inflammation via the NLRP3/autophagy pathway.

To study the effect of the NLRP3/autophagy pathway on the photoreceptor inflammatory response and the protective mechanism of CY-09 and astaxanthin (AST). ICR mice were intraperitoneally injected NaIO3, CY-09, AST successively and divided into 5 groups, including the control, NaIO3, NaIO3+CY-09, NaIO3+AST, and NaIO3+CY-09+AST groups. Spectral domain optical coherence tomography and flash electroretinogram were examined and the retina tissues were harvested for immunohistochemistry, enzyme linked immunosorbent assay (ELISA), and Western blotting. Retinal pigment epithelium cell line (ARPE-19 cells) and mouse photoreceptor cells line (661W cells) were also treated with NaIO3, CY-09, and AST successively. Cell proliferation was assessed by cell counting kit-8 (CCK-8) assay. Apoptosis was analyzed by flow cytometry. Changes in autophagosome morphology were observed by transmission electron microscopy. Quantitative polymerase chain reaction (qPCR) was used to detect NLRP3 and caspase-1. NLRP3, caspase-1, cleaved caspase-1, p62, Beclin-1, and LC3 protein levels were measured by Western blotting. IL-1β and IL-18 were measured by ELISA. Compared with the control group, the activity of NaIO3-treated 661W cells decreased within 24 and 48h, apoptosis increased, NLRP3, caspase-1, IL-1β and IL-18 levels increased, and autophagy-related protein levels increased (P<0.05). Compared with NaIO3 group, CY-09 and AST inhibited apoptosis (P<0.05), reduced NLRP3, caspase-1, IL-1β and IL-18 expression (P<0.05), and inhibited autophagy. Compared with the other groups, CY-09 combined with AST significantly decreased NLRP3 expression and inhibited the expression of the autophagy-related proteins p62, Beclin-1, and LC3 in vitro and in vivo (P<0.05). CY-09 and AST inhibit NaIO3-induced inflammatory damage through the NLRP3/autophagy pathway in vitro and in vivo. CY-09 and AST may protect retina from inflammatory injury.

Prospects and limitations of cumate-inducible lentivirus as a tool for investigating VEGF-A-mediated pathology in diabetic retinopathy

Diabetic retinopathy (DR) is a multifactorial disease displaying vascular-associated pathologies, including vascular leakage and neovascularization, ultimately leading to visual impairment. However, animal models accurately reflecting these pathologies are lacking. Vascular endothelial growth factor A (VEGF-A) is an important factor in the development of micro- and macro-vascular pathology in DR. In this study, we evaluated the feasibility of using a cumate-inducible lentivirus (LV) mediated expression of vegf-a to understand DR pathology in vitro and in vivo. Retinal pigment epithelial cells (ARPE-19) were transduced with cumate-inducible LV expressing vegf-a, with subsequent analysis of vegf-a expression and its impact on cell proliferation, viability, motility, and permeability. Cumate tolerability in adult Wistar rat eyes was assessed as an initial step towards a potential DR animal model development, by administering cumate via intravitreal injections (IVT) and evaluating consequent effects by spectral domain optical coherence tomography (SD-OCT), flash electroretinography (fERG), ophthalmic examination (OE), and immunohistochemistry. Transduction of ARPE-19 cells with cumate-inducible LV resulted in ~ 2.5-fold increase in vegf-a mRNA and ~ threefold increase in VEGF-A protein secretion. Transduced cells displayed enhanced cell proliferation, viability, permeability, and migration in tube-like structures. However, IVT cumate injections led to apparent retinal toxicity, manifesting as retinal layer abnormalities, haemorrhage, vitreous opacities, and significant reductions in a- and b-wave amplitudes, along with increased microglial activation and reactive gliosis. In summary, while cumate-inducible LV-mediated vegf-a expression is valuable for in vitro mechanistic studies in cellular drug discovery, its use is not a feasible approach to model DR in in vivo studies due to cumate-induced retinal toxicity.

The Thermal Conductivity of Bridgmanite at Lower Mantle Conditions Using a Multi‐Technique Approach

AbstractThe thermal conductivity of bridgmanite, the primary constituent of the Earth's lower mantle, has been investigated using diamond anvil cells at pressures up to 85 GPa and temperatures up to 3,100 K. We report the results of time‐domain optical laser flash heating and X‐ray Free Electron Laser heating experiments from a variety of bridgmanite samples with different Al and Fe contents. The results demonstrate that Fe or Fe,Al incorporation in bridgmanite reduces thermal conductivity by about 50% in comparison to end‐member MgSiO3 at the pressure‐temperature conditions of Earth's lower mantle. The effect of temperature on the thermal conductivity at 28–60 GPa is moderate, well described as , where a is 0.2–0.5. The results yield thermal conductivity of 7.5–15 W/(m × K) in the thermal boundary layer of the lowermost mantle composed of Fe,Al‐bearing bridgmanite.

Detecting the Early Optical Flashes of Gamma-Ray Bursts with Small Telescope Arrays

We present an observational approach for the independent detection of the early optical emission of long gamma-ray bursts (GRBs). For this purpose, we explore the potential of the Large Array Survey Telescope (LAST). This array of small optical telescopes can be used to scan a wide region of the sky, and to focus on a smaller field of view with increased sensitivity, as needed. The modularity of the array facilitates dynamic scanning of multiple fields, by shifting telescope pointing directions with high cadence. This can significantly increase the effective sky-coverage of a blind survey on short timescales. For events associated with gamma-ray counterparts, the valuable early time data can supplement high-energy observations. Regardless of gamma-ray association, detections can potentially be used to explore various phenomena associated with GRBs, such as orphan afterglows; dirty fireballs; and choked jets. We simulate a sample of GRBs and their respective optical signals at early times. After accounting for dynamic cadence, the light curves are given as input to a machine-learning classifier, used to identify astrophysical transients. We find that, by dedicating half of an LAST array to a blind search, one would expect to independently detect 7–11 GRBs yr–1, corresponding to an approximate intrinsic event rate of 0.12 deg–2 yr–1.

Neuroprotective and Anti-Inflammatory Activities of Hybrid Small-Molecule SA-10 in Ischemia/Reperfusion-Induced Retinal Neuronal Injury Models.

To induce I/R injury and inflammation, we subjected R28 and primary microglial cells to oxygen glucose deprivation (OGD) for 6 h in vitro or treated these cells with a cocktail of TNF-α, IL-1β and IFN-γ for 1 h, followed by the addition of SA-10 (10 µM). Inhibition of microglial activation, ROS scavenging, cytoprotective and anti-inflammatory activities were measured. In vivo I/R-injured mouse retinas were treated with either PBS or SA-10 (2%) intravitreally, and pattern electroretinogram (ERG), spectral-domain optical coherence tomography, flash ERG and retinal immunocytochemistry were performed. SA-10 significantly inhibited microglial activation and inflammation in vitro. Compared to the control, the compound SA-10 significantly attenuated cell death in both microglia (43% vs. 13%) and R28 cells (52% vs. 17%), decreased ROS (38% vs. 68%) production in retinal microglia cells, preserved neural retinal function and increased SOD1 in mouse eyes. SA-10 is protective to retinal neurons by decreasing oxidative stress and inflammatory cytokines.

On the defect detection limits of flash thermography in reflection mode: A comprehensive parametric 3D FE study

Optical flash thermography is a promising non-destructive testing technique which offers a fast, full-field and non-contact inspection. This study provides a comprehensive study into the influence of different factors on the physical defect detection limits of hidden defects with flash thermography, which is a missing key piece in the present literature.Therefore, a large-scale parametric 3D finite element study is performed in order to explore the actual defect detection limits for a substantial range of inspection conditions:i.Defect parameters: type, size and depth.ii.Material parameters: anisotropic diffusivity and stacking sequence.iii.Excitation parameters: heating non-uniformity, excitation energy and temporal excitation profile.iv.Acquisition parameters: sampling frequency and measurement noise.The finite element model is carefully designed using the commercial Abaqus software in order to ensure both accuracy and computational efficiency, and its reliability in quantifying defect detectability is experimentally validated. Decisive defect detection thresholds are substantiated, through which the detection limits in several (fiber reinforced) materials are concisely visualized and critically compared for the raw thermographic sequence and well-known processing techniques for flash thermography.

Lucy Observations of the DART Impact Event

The Lucy LOng Range Reconnaissance Imager (L’LORRI) took 1549 images of the Didymos–Dimorphos binary system, starting 12 hr before the Double Asteroid Redirection Test (DART) impact event on 2022 September 26 and ending 24 hr after it. The Lucy imaging campaign provided pre-impact monitoring of the baseline brightness of the Didymos system, as well as intensive 1 s cadence imaging starting 3 minutes prior to impact and extending until 4 minutes after impact, and then continued monitoring at increasing cadences and image exposure times to measure the Didymos system brightness changes produced by ejecta released during the impact. One of the L’LORRI images encompassed the exact time when the DART spacecraft impacted Dimorphos, but there is no evidence of a thermally generated optical flash in the image. L’LORRI observed a shell of fast-moving ejecta, and we derive a range of projected speeds (∼0.26–3.6 km s−1) for that material. The much slower moving ejecta (≲1 m s−1) stayed within a single L’LORRI pixel for the entire duration of the Lucy-DART program. We find that the slow ejecta were responsible for 57.4% ± 2.2% of the total post-impact brightness increase measured by L’LORRI, while the fast ejecta were responsible for 42.6% ± 2.3% of the post-impact brightness increase. The initial brightness increase relative to the pre-impact Didymos system brightness was significantly smaller for L’LORRI compared to that measured by some ground-based observers, which is plausibly explained by differences in phase angles and different responses to sodium emission depending on the camera spectral bandwidths.

Non‐Lightning‐Generated Whistler Waves in Near‐Venus Space

AbstractThe occurrence of Venusian lighting has been debated for decades. Terrestrial lightning generates whistler waves, and many whistlers have been observed in Venus's ionosphere and induced magnetosphere. Venusian lightning occurrence rates derived from these whistler observations are relatively high. However, optical flashes on Venus are exceedingly rare and Venus encounters by multiple spacecrafts have not detected lightning. These non‐detections and rare optical observations are consistent with low Venusian lightning occurrence rates, which is incompatible with the high whistler‐derived rates. We present observations of whistlers during a Parker Solar Probe Venus gravity assist and eliminate lightning as a possible source. These waves are observed at an altitude of 0.39 Venus radii on Venus' nightside with planetward propagation and are simultaneous with Langmuir waves. This provides a mechanism for whistler generation near Venus that does not require lightning, and suggests that whistler‐based lightning occurrence rates may be overestimated.

Restoration of vision by combined experimental antithymocyte therapy, and orbital radiation with high-dose steroids for severe, acute, steroid-refractory, congestive thyroid orbitopathy

PurposeWe report diagnostic and therapeutic dilemmas in the difficult case of compressive optic neuropathy with severe visual acuity and visual field loss with subsequent visual recovery in both eyes, in a patient with Graves’ orbitopathy (GO) by a combination of experimental antithymocyte therapy, orbital radiotherapy with high-dose steroids.MethodsA 72-year-old man presented with severe vision loss in both eyes. The visual symptoms had appeared over a year before the GO diagnosis. He was initially misdiagnosed with neuroborreliosis and optic neuritis based on brain and orbital magnetic resonance imaging. There was no exophthalmos. The ophthalmological examination included visual acuity, visual field, tonometry in primary and upgaze eye position, optical coherence tomography (OCT), pattern electroretinogram (PERG), pattern, and flash visual evoked potentials (PVEP and FVEP). The patient received experimental therapy with ATG, followed by high-dose of intravenous steroids and orbital radiotherapy.ResultsDelayed VEP peaks became shorter after treatment. After systemic and local therapy lowering of intraocular pressure was achieved. Abnormal PERG has been found three months before ganglion cells atrophy was detected in OCT. Visual acuity and visual field improvement occurred in both eyes after therapy, despite partial left optic nerve atrophy. The patient regained full decimal visual acuity (1.0 right from as poor as 0.3 to 1.0 in the right eye and from hand movements to 0.9 in the left. Severe visual field loss with advanced absolute scotomata has improved to slight relative scotomata. The duration of follow-up time after the treatment was 4 months.ConclusionsIntensive treatment of steroid-resistant Graves’ orbitopathy (GO) may prevent total optic nerve atrophy. Despite severely advanced optic neuropathy, this report emphasizes the necessity of therapy even with nearly complete visual function loss hence there is always a possibility to regain full visual acuity and visual field. Patients with tense orbital septum may not present with significant exophthalmos, thus delaying the correct diagnosis of orbitopathy. A supporting sign of GO was the difference in intraocular pressure in the primary and upgaze eye positions. Electrophysiological examinations are helpful in the diagnosis and monitoring of GO therapy. To our knowledge, this is the first report of this kind presenting visual function restoration and structural recovery in a patient with advanced optic neuropathy in GO.

The Influence of Gadolinium Oxide Nanoparticles Concentration on the Chemical and Physical Processes Intensity during Laser-Induced Breakdown of Aqueous Solutions

The paper investigates the physicochemical processes that occur during laser-induced breakdown in colloids of gadolinium oxide nanoparticles of different concentrations. A monotonic change in the number of optical breakdowns, the average distance between the nearest breakdowns in the track of a single laser pulse, the average plasma size of a single optical breakdown, the integral luminosity of an optical breakdown plasma flash, the intensity of acoustic signals, and the rate of formation of dissociation products—O2, H2, OH•, and H2O2—is demonstrated. It is shown that the rate of formation of chemical products of the decomposition of H2O molecules under the action of breakdown when using nanoparticles of rare earth metals, in particular, gadolinium oxide, is the highest compared to other materials. Based on one laser pulse, the rates of formation of chemical products formed during the dissociation of water during laser-induced breakdown of a colloid of gadolinium oxide nanoparticles are 13.13 nmol/pulse for H2, 5.41 nmol/pulse for O2, and 6.98 nmol/pulse for hydrogen peroxide.

Investigation and application of key technologies of aggregated flash payment based on marketing blockchain in the context of massive distributed generation grid connection

Abstract Optical flash payment technology is a form of optical flash payment application. Its payment scenario is mainly to directly realize “card free payment” in the consumption process through mobile devices, Bluetooth and other connection methods on mobile terminal devices such as smart phones under the mobile Internet environment. The “flash payment” is a more convenient payment method and a new payment channel without the function of electronic wallet. Compared with the current mainstream payment methods, it is more collaborative and complementary. Aggregated payment is a fourth party payment platform, which is different from Alipay, WeChat and other third payment platforms. Aggregated payment is a combination of technology and a platform that combines multiple payment methods. Based on the background of massive distributed power generation connected to the grid, this paper studied the key technologies of flash payment in combination with marketing blockchain, and discussed the data sharing mechanism of marketing information in multiple scenarios from the perspective of marketing blockchain by studying the data sharing mechanism in different scenarios. In this paper, a distributed optical flash payment system and a blockchain based encryption algorithm were proposed. Based on this research, the experimental results of key technologies of aggregated optical flash payment based on marketing blockchain were analyzed. The experimental results in this paper showed that 38.7 % of the users contacted the aggregation payment through the online platform. 11.7 % of people communicated through chatting with friends, and 9.8 % of enterprises got in touch through preferential policies. 4.5 % of them publicized through the media, and 8.3 % made requests through payment plans. 21 % of them transferred money through remittance, and 6 % of them got it through other ways. When using aggregate payment, the main reasons for users to choose aggregate payment were the network, friends chatting, and the acceptance of other people’s remittances. In the case that users used aggregate payment services, they most often used transfer and remittance, and most of these purchases were paid through mobile payment and credit card. In terms of users’ use of third-party services, it could be seen that transportation services and movie tickets were the most common ways of use. In terms of the aggregation payment strategy, the improvement of the three levels of aggregation payment could improve the risk prevention ability. First, the complaint mechanism was established to detect and correct potential vulnerabilities in the system in a timely manner. Second, consumers’ sense of self-protection should be strengthened. Third, the legal construction of the payment industry should be promoted to increase the strike force against illegal use.

Simulation of Venus Lightning‐I: Characterization of Free Radicals Generated in Venus Major Gas Mixture

AbstractA new Venus‐ESD‐Chamber (VEC) and peripheral systems were designed and built to simulate Venus lightning. It consists of three subsystems (a) electrostatic discharge (ESD) generation, (b) environmental pressure, temperature, gas composition control &amp; monitoring, and (c) optical and non‐optical sensors. We conducted arc discharge experiments in air, in CO2, and in Venus major gas mixture (CO2‐N2, 96.5% ± 1.5%:3.5% ± 1.5%) under 10, 350, 700, and 1,000 mbar pressures, that correspond to the 50–75 km altitude range in the cloud layer of Venus. Plasma and Raman spectra, plus gas sensors, and GC‐MS were used to identify the ESD products and to semi‐quantify CO and O3 generated by ESD. We have found all species of free radicals that have been found in previous simulation studies using different discharge technologies, including some important species in CO2‐N2 system, nitrogen oxides and CN. In addition, we found three species (O3, N2+, and C2) that have not been previously reported. Our results suggest that electron flux and kinetic energy are the determining factors for the type of generated free radical species and gas pressure plays a less important role. We found that the quantity of CO changes with the type of ESD. The detection of O3 in this study suggests that lightning might be one of the sources of O3 observed in the Venusian atmosphere. OI emission line at 777.4 nm is the most prominent line in our plasma spectra of FD, consistent with the intense optical flash observed by the Lightning and Airglow Camera (LAC) on the Akatsuki mission.

The Evryscope Fast Transient Engine: Real-time Detection for Rapidly Evolving Transients

Astrophysical transients with rapid developments on subhour timescales are intrinsically rare. Due to their short durations, events like stellar superflares, optical flashes from gamma-ray bursts, and shock breakouts from young supernovae are difficult to identify on timescales that enable spectroscopic follow-up. This paper presents the Evryscope Fast Transient Engine (EFTE), a new data reduction pipeline that is designed to provide low-latency transient alerts from the Evryscopes—a north–south pair of ultra-wide-field telescopes with an instantaneous footprint covering 38% of the entire sky—and tools for building long-term light curves from Evryscope data. EFTE leverages the optical stability of the Evryscopes by using a simple direct image subtraction routine that is suited to continuously monitoring the transient sky at a cadence of a minute. Candidates are produced within the base Evryscope 2 minute cadence for 98.5% of images, and internally filtered using vetnet, a convolutional neural network real–bogus classifier. EFTE provides an extensible and robust architecture for transient surveys probing similar timescales, and serves as the software test bed for the real-time analysis pipelines and public data distribution systems for the Argus Array, a next-generation all-sky observatory with a data rate 62 times higher than that of Evryscope.

MCS Stratiform and Convective Regions Associated with Sprites Observed from Mt. Fuji

Five sprites produced above the stratiform region and one sprite above the convective region in the mesoscale convective system (MCS) were observed on 22 July 2013 from the summit of Mt. Fuji. Four of the five sprites occurred in the stratiform region after the stratiform region was cut off from the convective region. The five sprite-producing +CGs (SP + CGs) occurred in and close to these cells with low lightning activity, although in-cloud lightning locations extensively spread out in the stratiform region. This suggests that positive charges were sufficient to produce the SP + CGs that accumulated extensively in the stratiform region due to a local (in situ) charge generation mechanism. One sprite occurred above the MCS convective region, and the SP + CG was also located at the MCS convective region. Video images indicated that the optical cloud flash associated with the SP + CG continued at least 150 ms until sprite emission. The optical cloud flash light occurred repeatedly at strong and weak intensities, and this characteristic indicated that the M components in the lightning occurred in the cloud. The SP + CG might have gathered sufficient positive charges to produce the sprite with a continuing current.

Detection of an Extremely Large Impact Flash on Jupiter by High-cadence Multiwavelength Observations

We report the detection of an optical impact flash on Jupiter on 2021 October 15 by a dedicated telescope, Planetary ObservatioN Camera for Optical Transient Surveys, for the first time. Our temporally resolved three-band observations of the flash allowed investigations of its optical energy without the need for approximations on the impact brightness temperature. The kinetic energy of the impactor was equivalent to approximately two megatons of TNT, an order of magnitude greater than that of previously detected flashes on Jupiter and comparable with the Tunguska impact on Earth in 1908. This detection indicates that Tunguska-like impact events on Jupiter occur approximately once per year, two to three orders of magnitude more frequently than terrestrial impacts. The observed flash displayed a single-temperature blackbody spectrum with an effective temperature of approximately 8300 K without clear temporal variation, possibly representing common radiative features of terrestrial Tunguska-class superbolides.

Electrophysiological and psychophysical studies in assessment of visual functions in patients with hereditary optic neuropathy

To study the capabilities of electrophysiological and psychophysical examination methods for assessment of the functional state of ganglion cells, retina and optic nerve in patients with hereditary optic neuropathy (HON). The study included 60 patients (118 eyes) with a genetically confirmed diagnosis of HON. All study patients underwent visual field test (VFT), spectral optical coherence tomography (OCT), flash and pattern visual evoked potentials (VEP) (Flash-VEP, FVEP; Pattern-VEP, PVEP), photopic electroretinography with photonegative response (PhNR) registration and the color vision test. In 24 patients (46 eyes), these parameters were assessed before the start of treatment and one year later. The treatment involved the mitochondria-targeted antioxidant SkQ1 - plastoquinonyl-decyl-triphenylphosphonium bromide (PDTP) in the form of eye drops. The main PVEP components for 1.0° and 0.3° were registered in 20% and in 14% of patient eyes with HON and high visual functions, respectively. After one year of PDTP use, a significant decrease in P100 peak latency was found only in the group with disease duration of ≤1.5 years as of the time of treatment start (p<0.05). Significant differences were observed in the PhNR amplitude (p<0.004) between patients of the main and the control groups, as well as in the PhNR amplitude between patients with visual acuity of ≤0.1 and ≥0.13 (p<0.01). Patients with high visual functions were found to have a correlation between the PhNR amplitude, GCC thickness and the global loss index (GLV). Along with VFT, OCT and color vision tests, electrophysiological studies are one of the main methods of examining patients with HON. After one year of PDTP use, there was a significant decrease in the FVEP P2 peak latency in the group with a disease duration of ≤1.5 years as of the time of treatment start. The PhNR amplitude in patients with high visual functions was found to correlate with structural changes in the ganglion cell layer and the retinal nerve fiber layer.

Ocular Characteristics of Patients with Leber Congenital Amaurosis 6 Caused by Pathogenic RPGRIP1 Gene Variation in a Chinese Cohort.

Purpose To delineate the clinical and genetic characteristics of Chinese patients with RPGRIP1-associated Leber congenital amaurosis 6 (LCA6). Methods After screening 352 unrelated families with clinically diagnosed RP, five LCA6 patients with RPGRIP1 variations from unrelated Chinese families were identified. Full ophthalmology examinations, including decimal best-corrected visual acuity (BCVA), fundus photography, fundus autofluorescence imaging, spectral-domain optical coherence tomography (SD-OCT), full-field electroretinography (ffERG), multifocal electroretinography (mfERG), perimetry, and flash visual evoked potential (FVEP), were performed. Target next-generation sequencing (NGS) and Sanger sequencing were performed for the five patients to identify and to validate candidate disease-causing variants. Results Five patients were molecularly diagnosed as the LCA6 associated with RPGRIP1 variation, with typical clinical characteristics including congenital night blindness, nystagmus, and visual defect, at an early age. Interestingly, LCA6 exhibited extensive clinical heterogeneity and the changes in the morphology and function were not completely consistent in the five LCA6 patients. Case 1 showed extensive inferior-nasal retinal atrophy with a corresponding area of hypofluorescence in fundus autofluorescence, and the fundus photograph was nearly normal in cases 2 and 3. The ERG results displayed a moderately reduced rod-system response in cases 1 and 2 and a significant reduced rod-system response in case 3. Both case 4 and case 5 showed mottled pigmentation in fundi and an unrecordable rod and cone-system response in ERG. Moreover, we identified eight compound variants and one homozygous variant in the five patients with RPGRIP1. Conclusions This is the largest report focused on the clinical electrophysiological features of patients with associated LCA6 caused by the variation in the RPGRIP1 gene in the Chinese population with an enriched phenotypic and genotypic background of LCA6 to improve future gene therapies.

Constraints on Optical Emission of FAST-detected FRB 20181130B with GWAC Synchronized Observations

Abstract Multiwavelength simultaneous observations are essential to the constraints on the origin of fast radio bursts (FRBs). However, it is a significant observational challenge due to the nature of FRBs as transients with a radio millisecond duration, which occur randomly in the sky regardless of time and position. Here, we report the search for short-time fast optical bursts in the Ground-based Wide Angle Camera (GWAC) archived data associated with FRB 20181130B, which were detected by the Five-hundred-meter Aperture Spherical radio Telescope and recently reported. No new credible sources were detected in all single GWAC images with an exposure time of 10 s, including images with coverage of the expected arrival time in optical wavelength by taking the high dispersion measurements into account. Our results provide a limiting magnitude of 15.43 ± 0.04 mag in the R band, corresponding to a flux density of 1.66 Jy or 8.35 mag in AB system by assuming that the duration of the optical band is similar to that of the radio band of about 10 ms. This limiting magnitude makes the spectral index of α &lt; 0.367 from optical to radio wavelength. The possible existence of longer-duration optical emission was also investigated with upper limits of 0.33 Jy (10.10 mag), 1.74 mJy (15.80 mag), and 0.16 mJy (18.39 mag) for the durations of 50 ms, 10 s, and 6060 s, respectively. This undetected scenario could be partially attributed to the shallow detection capability, as well as the high inferred distance of FRB 20181130B and the low fluence in radio wavelength. The future detectability of optical flashes associated with nearby and bright FRBs are also discussed in this paper.

Blue Flashes as Counterparts to Narrow Bipolar Events: The Optical Signal of Shallow In‐Cloud Discharges

AbstractNarrow Bipolar Events (NBEs) are powerful radio emissions from thunderstorms, which have been recently associated with blue optical flashes on cloud tops and attributed to extensive streamer electrical discharges named fast breakdown. Combining data obtained from a thunderstorm over South China by the space‐based Atmosphere Space Interactions Monitor, the Vaisala GLD360 global lightning network and very low frequency/low frequency radio detectors, here we report and analyze for the first time the optical emissions of blue luminous events associated with negative NBEs and located at the top edge of a thundercloud. These emissions are weakly affected by scattering from cloud droplets, allowing us to estimate the source extension and optical energy involved in the process. The optical energy in the 337‐nm band emitted by fast breakdown is about 104 J, which involves around 109 streamer initiation events.

Observations of Lightning NOx Production From Tropospheric Monitoring Instrument Case Studies Over the United States

AbstractNitrogen oxides produced by lightning (LNOx) play an important role in determining mid‐ and upper‐tropospheric concentrations of the hydroxyl radical (OH), methane (CH4), and ozone (O3). The moles of NOx produced per flash was examined using nitrogen dioxide (NO2) columns and cloud properties from the Tropospheric Monitoring Instrument (TROPOMI) and flash counts from the Geostationary Lightning Mapper (GLM) aboard the Geostationary Operational Environmental Satellite‐16 (GOES‐16) and Earth Networks Total Lightning Network (ENTLN) for 29 convective systems over the United States that occurred during 2018 and 2019. For each of the case studies, the LNOx production efficiency (PE) was estimated using TROPOMI pixels over deep convection. First, the NOx columns associated with the TROPOMI NO2 columns were estimated using a specially derived air mass factor (AMF). The tropospheric column due to recent lightning was then determined by subtracting from the median NOx column a background representative of the NOx column due to sources other than recent lightning. Then, the PE was calculated by multiplying the LNOx column by the storm area and dividing by the number of flashes contributing to the column. For a three‐hour chemical lifetime, the mean PE was found to be 175 ± 100 mol per flash for optical flashes from GLM and 120 ± 65 mol per flash for radio‐wave‐detected flashes from ENTLN. The uncertainty associated with these values is mostly due to uncertainties in tropospheric background, AMF, and detection efficiency. GLM PE for individual systems was found to be positively correlated with optical energy.