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©2020. The Authors. This is an open access article under the terms of the Creative Commons Attribution‐NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.https://creativecommons.org/licenses/by-nc/4.0/ ; Narrow bipolar events (NBEs) (also called narrow bipolar pulses [NBPs] or compact intracloud discharges [CIDs]) are energetic intracloud discharges characterized by narrow bipolar electromagnetic waveforms identified from ground-based very low frequency (VLF)/low-frequency (LF) observations. The simplified ray-theory method proposed by Smith et al. (1999, https://doi.org/10.1029/1998JD200045; 2004, https://doi.org/10.1029/2002RS002790) is widely used to infer the altitude of intracloud lightning and the effective (or virtual) reflection height of the ionosphere from VLF/LF signals. However, due to the large amount of high-frequency components in NBEs, the propagation effect of the electromagnetic fields for NBEs at large distance depends nontrivially on the geometry and the effective conductivity of the Earth-ionosphere waveguide (EIWG). In this study, we investigate the propagation of NBEs by using a full-wave Finite-Difference Time-Domain (FDTD) approach. The simulated results are compared with ground-based measurements at different distances in Southern China, and we assess the accuracy of the simplified ray-theory method in estimating the altitude of the NBE source and the effective reflection height of the ionosphere. It is noted that the evaluated NBE altitudes have a slight difference of about ±1 km when compared with the full-wave FDTD results, while the evaluated ionospheric reflection heights are found to be bigger than those obtained from FDTD model by about 5 km. ©2020. The Authors. ; This work was supported by the European Research Council (ERC) under the European Union H2020 Programme/ERC Grant 681257. The ground-based VLF/LF measurements related to this article can be obtained from CAS Key Laboratory of Geo-space Environment in the School of Earth and Space Sciences at University of Science and Technology of China in Hefei, China (http://222.195.83.28/) ; Peer reviewed

This is the final version. Available on open access from the American Association for the Advancement of Science via the DOI in this record ; Data and materials availability: All satellite data used in this work is publicly available through NASA Goddard Earth Sciences Data and Information Services Center (https://disc.gsfc.nasa.gov/) and ESA Sentinel-5P Pre-Operations Data Hub (https://s5phub.copernicus.eu/). GMI model output and policy response data are available upon request from the authors as is code to process all data sets. All data needed to evaluate the conclusions in the paper are present in the paper and/or the Supplementary Materials. Additional data available from authors upon request. ; China's policy interventions to reduce the spread of the coronavirus disease 2019 have environmental and economic impacts. Tropospheric nitrogen dioxide indicates economic activities, as nitrogen dioxide is primarily emitted from fossil fuel consumption. Satellite measurements show a 48% drop in tropospheric nitrogen dioxide vertical column densities from the 20 days averaged before the 2020 Lunar New Year to the 20 days averaged after. This is 21% ± 5% larger than that from 2015–2019. We relate this reduction to two of the government's actions: the announcement of the first report in each province and the date of a province's lockdown. Both actions are associated with nearly the same magnitude of reductions. Our analysis offers insights into the unintended environmental and economic consequences through reduced economic activities. ; NASA

Using the data sets taken at center-of-mass energies above 4 GeV by the BESIII detector at the BEPCII storage ring, we search for the reaction e(+)e(-) -> gamma(ISR) X(3872) -> gamma(ISR)pi(+)pi(-) J/psi via the Initial State Radiation technique. The production of a resonance with quantum numbers J(PC) = 1(++) such as the X(3872) via single photon e(+)e(-) annihilation is forbidden, but is allowed by a next-to-leading order box diagram. We do not observe a significant signal of X(3872), and therefore give an upper limit for the electronic width times the branching fraction Gamma B-X(3872)(ee)(X(3872) -> pi(+)pi(-) J/psi) < 0.13 eVat the 90% confidence level. This measurement improves upon existing limits by a factor of 46. Using the same final state, we also measure the electronic width of the psi(3686) to be Gamma(psi)(ee)(3686) ee = 2213 +/- 18(stat) +/- 99(sys) eV. ; Funding: The BESIII collaboration thanks the staff of BEPCII and the IHEP computing center for their strong support. This work is supported in part by the National Key Basic Research Program of China under Contract No. 2015CB856700; National Natural Science Foundation of China (NSFC) under Contract Nos. 11125525, 11235011, 11322544, 11335008, 11425524; the Chinese Academy of Sciences (CAS) Large-Scale Scientific Facility Program; Joint Large-Scale Scientific Facility Funds of the NSFC and CAS under Contract Nos. 11179007, U1232201, U1332201; CAS under Contract Nos. KJCX2-YW-N29, KJCX2-YW-N45; 100 Talents Program of CAS; INPAC and Shanghai Key Laboratory for Particle Physics and Cosmology; German Research Foundation DFG under Contract No. CRC-1044; Seventh Framework Programme of the European Union under Marie Curie International Incoming Fellowship Grant Agreement No. 627240; Istituto Nazionale di Fisica Nucleare, Italy; Ministry of Development of Turkey under Contract No. DPT2006K-120470; Russian Foundation for Basic Research under Contract No. 14-07-91152; U.S. Department of Energy under Contract Nos. DE-FG02-04ER41291, DE-FG02-05ER41374, DE-FG02-94ER40823, DESC0010118; U.S. National Science Foundation; University of Groningen (RuG) and the Helmholtzzentrum fur Schwerionenforschung (GSI), Darmstadt; WCU Program of National Research Foundation of Korea under Contract No. R32-2008-000-10155-0.