Sprite possibly produced by two distinct positive cloud-to-ground lightning flashes

Transient luminous event (TLEs) observations have been conducted in mainland China since 2007, with a number of TLEs documented. This study analyzed a very unusual and unique positive sprite event, that may be produced jointly by two distinct positive cloud-to-ground lightning flashes (+CGs) occurring within a short time difference but with different locations separated by about 27 km. This observation is different from previous studies reporting that most of the sprites were triggered by a single +CG flash and its possible following continuous current. Detailed analysis on extremely low frequency (ELF) magnetic field shows that combined charge moment change (CMC) due to the two +CGs is smaller (~1478 C km) than those of the parent CGs for the other two sprites (1582 and 2134 C km, respectively) recorded over the same thunderstorm. The vertical extension and brightness of the sprites correspond well with the CMC of their parent CGs, namely, the larger the CMC value the brighter the sprite, and the larger the CMC value the larger the vertical extension. Negative lightning flashes dominated during the thunderstorm life cycle. The three sprites occurred during a time window in which both negative and positive flashes were active. The three sprites occurred over the thunderstorm stratiform region

Optical emissions associated with narrow bipolar events from thunderstorm clouds penetrating into the stratosphere

Narrow bipolar events (NBEs) are signatures in radio signals from thunderstorms observed by ground-based receivers. NBEs may occur at the onset of lightning, but the discharge process is not well understood. Here, we present spectral measurements by the Atmosphere‐Space Interactions Monitor (ASIM) on the International Space Station that are associated with nine negative and three positive NBEs observed by a ground‐based array of receivers. We found that both polarities NBEs are associated with emissions at 337 nm with weak or no detectable emissions at 777.4 nm, suggesting that NBEs are associated with streamer breakdown. The rise times of the emissions for negative NBEs are about 10 μs, consistent with source locations at cloud tops where photons undergo little scattering by cloud particles, and for positive NBEs are ~1 ms, consistent with locations deeper in the clouds. For negative NBEs, the emission strength is almost linearly correlated with the peak current of the associated NBEs. Our findings suggest that ground-based observations of radio signals provide a new means to measure the occurrences and strength of cloud-top discharges near the tropopause.publishedVersio

JIB-04 has broad-spectrum antiviral activity and inhibits SARS-CoV-2 replication and coronavirus pathogenesis

Pathogenic coronaviruses are a major threat to global public health. Here, using a recombinant reporter virus-based compound screening approach, we identified small-molecule inhibitors that potently block the replication of severe acute respiratory syndrome virus 2 (SARS-CoV-2). Among them, JIB-04 inhibited SARS-CoV-2 replication in Vero E6 cells with a 50% effective concentration of 695 nM, with a specificity index of greater than 1,000. JIB-04 showe