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Auroral streamers are important meso‐scale processes that transport plasma and magnetic energy and drive dynamic magnetosphere‐ionosphere (MI) coupling and space weather. Although streamers are typically studied using imagers sensitive to energetic (>${ >} $ 1 keV) electron precipitation, such as all‐sky imagers, some are associated with low‐energy (<${< } $ 1 keV) precipitation better captured by red‐line auroral emissions. This paper reports such streamer‐like red‐line auroras observed poleward of a black aurora and an auroral torch, associated with a magnetospheric electron injection and braking ion flows. Using conjugate space‐ground observations, quasilinear theory, and auroral forward modeling, we establish the first direct linkage between streamer‐like red‐line auroras and plasma sheet electron pitch‐angle scattering by time‐domain structures. These results underscore the importance of wave‐driven diffuse auroral processes in generating low‐energy auroral streamers, distinct from the conventional quasi‐electrostatic coupling paradigm.

Wind‐driven sand transport at the Earth's surface exhibits pronounced spatiotemporal variability, forming elongated sand streamers that critically control sand flux. Despite their importance, the detailed fundamental mechanisms governing streamer formation remain elusive. This study presents results from a novel image‐processing algorithm analyzing high‐resolution video imagery combined with 3D wind measurement in turbulent boundary layer flow over a sandy beach. Streamers are shown to align with high‐momentum pathways modulated by large‐scale turbulence structures, and sand flux inside streamers scales with flow forcing. Streamer width remains invariant and decoupled from flow forcing, whereas streamer spacing increases with wind speed. These results support a top‐down modulation mechanism where the invariant streamer width is likely governed by the height of the turbulent footprint, whereas the increased spacing may relate to spanwise dilation of vortex scales or a near‐surface momentum feedback mediated by the saltating sand.

An auroral streamer—a usually meridionally aligned, arc‐like feature that extend across the auroral oval. We performed a high‐resolution global magnetohydrodynamic simulation to characterize the evolution of streamers and their coupling to magnetotail drivers. The results show that streamers, which are a consequence of magnetotail flow bursts, strengthen as the simulation progresses. We calculated the contributions of different precipitating electron energy fluxes to streamer dynamics based on simple empirical proxies and found that monoenergetic precipitation dominates, followed by broadband, with little from diffuse precipitation. Poleward motion (∼1° magnetic latitude) of one streamer preceded its equatorward motion in the high‐resolution simulation. The simulation indicates that the poleward motion is caused by a sequential energy injection into the ionosphere from multiple bursty bulk flows propagating in succession. Our results provide an explanation for the poleward propagation of streamers and illustrate their global evolution and energetics in magnetotail dynamics.

Electric streamer discharges (streamers) in the air are a very important stage of lightning, taking place before formation of the leader discharge, and with which an electric discharge starts from conducting objects which enhance the background electric field, such as airplanes. Despite years of research, it is still not well understood what mechanism determines the values of a streamer’s parameters, such as its radius and propagation velocity. The novel Streamer Parameter Model (SPM) was made to explain this mechanism, and to provide a way to efficiently calculate streamer parameters. Previously, we demonstrated that SPM results compared well with a limited set of experimental data. In this article, we compare SPM predictions to the published hydrodynamic simulation (HDS) results.

We present the spatially resolved absolute brightness of the Fe x, Fe xi, and Fe xiv visible coronal emission lines from 1.08 to 3.4 R ⊙, observed during the 2019 July 2 total solar eclipse (TSE). The morphology of the corona was typical of solar minimum, with a dipole field dominance showcased by large polar coronal holes and a broad equatorial streamer belt. The Fe xi line is found to be the brightest, followed by Fe x and Fe xiv (in disk B ⊙ units). All lines had brightness variations between streamers and coronal holes, where Fe xiv exhibited the largest variation. However, Fe x remained surprisingly uniform with latitude. The Fe line brightnesses are used to infer the relative ionic abundances and line-of-sight-averaged electron temperature (T e ) throughout the corona, yielding values from 1.25 to 1.4 MK in coronal holes and up to 1.65 MK in the core of streamers. The line brightnesses and inferred T e values are then quantitatively compared to the Predictive Science Inc. magnetohydrodynamic model prediction for this TSE. The MHD model predicted the Fe lines rather well in general, while the forward-modeled line ratios slightly underestimated the observationally inferred T e within 5%–10% averaged over the entire corona. Larger discrepancies in the polar coronal holes may point to insufficient heating and/or other limitations in the approach. These comparisons highlight the importance of TSE observations for constraining models of the corona and solar wind formation.

The flashover along the insulator endangers the reliable operation of the electrical power system. The reasonable curved profiles of the shed could improve the flashover voltage, which would reduce power system outages. The research on the influence of the curved profiles of the shed on the streamer propagation along the insulator made of polymer was presented in the paper. The streamer propagation “stability” field, path, and velocity affected by the curved profiles of the shed, were measured by ultraviolet camera, ICCD camera, and photomultipliers. The “surface” component of the streamer is stopped at the shed with the different curved profiles, while the “air” component could go round the shed and reach the cathode. The streamer propagation “stability” fields are inversely proportional to the curved profiles of the shed. The streamer propagation velocities are proportional to the curved profiles of the shed. The relationship between the streamer propagation and the flashover propagation was discussed in depth. The subsequent flashover propagation is greatly affected by the streamer propagation path and “stability” field. Furthermore, the influence of the material properties on the streamer propagation path was also discussed in depth.

Four upward propagating streamers in two carrot sprites over northwest Texas were recorded at 100,000 frames per second at 07:46:35 UT, 2 June 2019, from the Langmuir Laboratory near Socorro, New Mexico. The streamers reached velocities of 50–80 × 106 m/s with accelerations up to 25 × 1010 m/s/s. The upward motion ended with the top of the streamers near 90 km altitude. At this time, the streamers reached maximum brightness. The streamer head then dissolved and the brightness decayed exponentially with time constants between 0.078 and 0.097 ms. We interpret the dissolution and decay to be the result of interaction with the bottom of the ionosphere. Assuming the decay to be dictated by electric field relaxation, the ambient D region electron density would be 107 to 108 m−3. The analysis suggests that sprite observations can provide multipoint measurements of the D region ionosphere impacted by powerful lightning capable of triggering sprites. Plain Language Summary Sprites have been recorded at 100,000 frames per second. Analysis of the decay of upward propagating streamer brightness indicates that the observations may be used to infer the ambient electron densities in the D region ionosphere impacted by powerful lightning capable of triggering sprites. Key Points Upward propagating streamers in sprites were recorded at 100,000 frames per second The streamer head brightness decay is exponential; assuming it is due to electric field relaxation the ambient D region electron density can be derived Analysis suggests that sprites can provide multipoint measurements of D region impact by powerful lightning capable of triggering sprites

In a fluid environment, biofilms usually form and grow into streamers attached to solid surfaces. Existing research on single streamers studied their formation and failure modes. In the experiment on biofilm growth in a microfluidic channel, we found that rings composed of bacteria and an extracellular matrix are important elements on a mesoscopic scale. In the fluid environment, the failure of these ring elements causes damage to streamers. We simulated the growth and deformation of the ring structure in the micro-channel using multi-agent simulation and fluid–structure coupling of a porous elastic body. Based on this, we simulated the biofilm evolution involving multi-ring deformation, which provides a new length scale to study the biofilm streamer dynamics in fluid environments.

Inertial particles in wall-bounded turbulence are known to form streaks, but experimental evidence and predictive understanding of this phenomenon is lacking, especially in regimes relevant to atmospheric flows. We carry out wind tunnel measurements to investigate this process, characterizing the transport of microscopic particles suspended in turbulent boundary layers. The friction Reynolds number $Re_\\tau = {O}(10^4)$ allows for significant scale separation and the emergence of large-scale motions, while the range of viscous Stokes number $St^+=18$–870 is relevant to the transport of dust and fine sand in the atmospheric surface layer. We perform simultaneous imaging of both carrier and dispersed phases along wall-parallel planes in the logarithmic layer, demonstrating that streamwise particle streaks largely overlap with large-scale low-speed flow regions. The fluid–particle slip velocity indicates that with increasing inertia, the particle streaks outlive the low-speed fluid streaks. Moreover, two-point statistics show that the width of the particle streaks increases linearly with Stokes number, bounded by the size of the coherent flow structures. Finally, the particle-sampled flow topology suggests that particle streaks reside between the legs of hairpin packets. From these observations, we infer a conceptual view of the formation of particle streaks in the frame of the attached eddy model. A scaling for the particle streaks’ width is derived as a function of $Re_\\tau$ and $St^+$, which reproduces the measured trends and predicts widths ${O}(0.1)$ m in the atmospheric surface layer, comparable to aeolian streamers observed in the field.

PurposeDigitally driven virtual streamers are increasingly utilized in live-streaming commerce, possessing distinct advantages compared to human streamers. However, the applicable scenarios of virtual streamers are still unclear. Focusing on product attribute variances, this paper compares the livestreaming effects of virtual and human streamers to clarify the applicable scenarios for each and assist companies in strategically choosing suitable streamers.Design/methodology/approachWe conducted four experiments utilizing both images and video as stimulus materials, and each experiment employed different products. To test the proposed model, a total of 1,068 valid participants were recruited, encompassing a diverse group of individuals, including undergraduates and employed workers.FindingsThe results indicate no significant difference between virtual and human streamers in increasing consumers’ purchase intention for utilitarian products. In contrast, human streamers are more effective in enhancing consumer purchase intention for hedonic products, with a mediating role of mental imagery quality. Consumers’ implicit personality variances also influence their willingness to accept virtual streamers.Originality/valueThis paper is the first to compare the effects of virtual and human streamers in promoting different products to enhance our comprehension of virtual streamers. Given the potential risks associated with human streamers, a comprehensive understanding of the role of virtual streamers is imperative for brands when deploying live-streaming commerce activities.