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Wave‐particle interactions are essential for energy transport in the magnetosphere. In this study, we investigated an event during which electrons interact simultaneously with waves in different scales, using data from the Magnetospheric Multiscale mission. At the macroscale (∼105${\\sim} 1{0}^{5}$km), drift resonance between ultra‐low frequency (ULF) waves and 70–300 keV electrons is observed. At the microscale (∼100−101${\\sim} 1{0}^{0}-1{0}^{1}$km), lower‐band chorus waves and electron cyclotron harmonic (ECH) waves are alternately generated, showing signatures of modulation by ULF waves. We found that compressional ULF waves affect the temperature anisotropy of 1–10 keV electrons, thereby periodically exciting chorus waves. Through linear instability analysis, we propose that ULF waves modulate ECH wave emissions by regulating the gradient of electron phase space density at the edge of the loss cone. Our results enhance the understanding of cross‐scale wave‐particle interactions, highlighting their importance in magnetospheric dynamics.

The morphology and motion of auroras have been widely studied due to their indications on magnetospheric processes. Here, we report a new kind of “auroral curls,” which have wavelengths in the mesoscale (∼100 km) and propagate azimuthally. Utilizing data from the Chinese Antarctic Zhongshan Station (the all‐sky imager and the high‐frequency radar), the Active Magnetosphere and Planetary Electrodynamics Response Experiment and the Defense Meteorological Satellite Program, we analyze an event occurred on 23 April 2019. We find these curls are fine structures in the poleward boundary of multiple arcs. Corresponding field‐aligned currents manifest as a series of longitudinally arranged pairs, while ionospheric flow velocities nearby oscillate with periods in the Pc 5 band. Observational evidence suggests these curls are connected with ultra‐low frequency (ULF) waves, which opens the possibility of using auroras to globally image ULF waves. Plain Language Summary Auroras caused by precipitation of magnetospheric particles contain information about physical processes happened in the magnetosphere. In this letter, we report a new kind of auroral dynamic forms observed in Antarctica. These structures present both spatial and temporal periodic characteristics, which have similar scales with those of magnetospheric ultra‐low frequency (ULF) waves. We propose these auroral forms are connected with ULF waves, which provides a potential method to globally image ULF waves by analyzing properties of these auroras. Key Points Azimuthally propagating “auroral curls” with mesoscale wavelengths were observed in Antarctica These curls are fine structures in the poleward boundary of multiple arcs formed by longitudinal‐arranged field‐aligned current pairs Ionospheric flow velocities nearby oscillate with periods in the Pc 5 band, indicating connections with ultra‐low frequency waves

In this study employing data from the Swarm satellites at an altitude of ≈500 km, we present evidence of field‐line resonances (FLRs) in the Pc2‐3 (0.02–0.2 Hz) frequency band in the undisturbed post‐sunset region of the equatorial ionosphere. We identify 26 events extending to magnetic latitudes as low as 2°, which was previously thought to be too low for FLRs to exist due to ionospheric damping. Identification of FLRs is supported by a narrow‐band fundamental and first harmonics, an oscillating field‐aligned Poynting vector, a relative phase shift between E and δB of ≈90°, and in one case observation of one wave in conjugate hemispheres by two satellites separated by 4 min. We show that, contrary to the non‐uniform trend of ground‐based observations, the fundamental frequencies of these occurrences decline monotonically with increasing field‐line length. Their frequencies differ from those of ground‐based magnetometer observations reported in the literature. Plain Language Summary Ultra‐low‐frequency (ULF) waves play a crucial role in the coupling of the magnetosphere‐ionosphere system. These waves have been reported abundantly in the high latitude ionosphere, where they are driven directly by processes in the magnetosphere and solar wind. ULF waves have also been reported at the equatorial ionosphere, but less frequently. In some cases, low‐latitude waves are thought to be driven by high‐latitude waves ducting through the ionosphere or by compressional waves, which can propagate across geomagnetic field lines from high altitudes in the equatorial region. These waves can then excite interhemispheric field‐line resonances (FLRs), in which Earth's magnetic field lines vibrate like a guitar string, with longer field lines oscillating at lower frequencies. In this work, we use the Swarm satellites to study low‐latitude FLRs at an altitude of ≈500 km in the quiet ionosphere at geomagnetic latitudes below 3°. We demonstrate the existence of FLRs with periods between 5 and 50 s which increase with magnetic latitude, as expected when field line lengths increase. Key Points Field line resonances (FLRs) are identified at the lowest magnetic latitude ever reported The fundamental frequency of our events decreases with increasing magnetic latitude in a uniform trend FLRs detected at conjugate latitudes by two spacecraft at the equatorial ionosphere

During the winter, the cold wave activity over the mid-high latitudes has profound impacts on agriculture, economic and human wellbeing. Such extreme weather events have been connected with the East Asia winter monsoon system and significantly influence the climate over the Eurasian continent. However, the multidecadal variabilities and regional interconnections of the cold wave activity across the Northern Hemisphere are lesser-known. In this study, we investigate the multidecadal variations in the cold wave frequency (CWF) and find an inverse relationship between Greenland and central Eurasia. Observational and modeling evidence suggests that the Atlantic Multidecadal Oscillation (AMO) is likely to be the driving force of the multidecadal seesaw in CWF, while the effects of the Arctic sea ice are very limited. The increased sea surface temperature (SST) in association with the AMO warms the subpolar troposphere and weakens the predominant westerlies over mid-high latitudes, resulting in positive geopotential height anomalies over the subpolar region. This further weakens the Icelandic Low and strengthens the Siberian High, which directly induces the warming (cooling) over Greenland (central Eurasia). There is a strong coherence between the mean state of surface air temperature and temperature extremes. The AMO-induced warming/cooling in Greenland/central Eurasia corresponds well with less/more frequent cold wave activities. Our results provide new insight into the multidecadal variability of cold wave activities and suggest that the CWF in the Northern Hemisphere may be interlinked.

Terahertz (THz) technology holds great promise in biomedical imaging, non‐destructive testing, biosensing, and telecommunications, but its adoption is limited by weak light–matter interactions and strong dissipative losses in conventional metamaterials. To overcome these limitations, a dual strategy is introduced that combines interdigitated electric split‐ring resonators (ID‐eSRRs) with the complex‐frequency wave (CFW) technique. Electrical gating from 0–200 V tunes the graphene Fermi level from 0.3756 to 0.6505 eV, providing a wide and continuous resonance shift for fingerprint‐aligned sensing. The CFW method reconstructs loss‐compensated spectra from real‐frequency data, generating virtual gain and markedly sharpening resonances. Simulations show that the optimized ID‐eSRR achieves a refractive index sensitivity of 196 GHz/RIU for 100 nm analytes, while CFW amplification increases the quality factor from 8.54 to 427.96, a 50.1‐fold enhancement. This improvement enables reliable discrimination of DNA variants with refractive index differences as small as Δn=0.005 $\\Delta n = 0.005$at n≈1.6 $n \\approx 1.6$ . The demonstrated approach provides a generalizable route to simultaneously enhance sensitivity and Q $Q$ ‐factor, thereby overcoming the long‐standing sensitivity–Q $Q$trade‐off and advancing the development of high‐performance THz sensors for ultrasensitive biomedical diagnostics. A dual strategy combining interdigitated graphene resonators and complex‐frequency waves yields a 54‐fold Q $Q$ ‐factor enhancement and superior sensitivity, establishing a high‐FOM platform for ultrasensitive terahertz biosensing.

Blockages are commonly formed in fluid pipelines such as water supply systems, which may greatly affect the internal flow states and conveyance capacities. This paper investigates the transient behavior of a pressured water pipeline with blockage under different transient wave perturbations based on the Computational Fluid Dynamics (CFD) model. To this end, a water pipeline is modeled in a 2D axisymmetric geometry with refined mesh and the blockage is modeled as a small, constricted section. Both the low and high-frequency waves (LFW and HFW), in terms of radial fundamental wave frequency of a pipeline, ∼a/R, with a being acoustic wave speed and R being pipe radius, are injected for the numerical analysis. Through this CFD model, both the axial and radial transient waves have been observed for different frequency wave injections, which are firstly validated by datasets available from former studies. After validations, the local flow characteristics, such as the velocity field, the vorticity field, and its temporal, spatial evolution in the vicinity of blockage during transient wave processes, including before and after transient wavefront passing, are elaborated and analysed in this study. The results indicate the significant influence of blockages on transient behaviors, especially under high-frequency wave conditions.

This study provides a systematic analysis of the spatiotemporal distribution and trends in the frequency of significant wave height (SWH) exceeding level 5 (SWH > 2.5 m) and level 7 (SWH > 6 m) in the Northwest Pacific (NWP) for 1993–2024, which are defined as f5 and f7, respectively, as well as their correlations with major climate indexes. Our results indicate that (1) the high-value zones for the annual mean f5 and f7 are both located in the south waters of the Aleutian Islands, with maximum values of 58.0% and 6.4%, respectively. Winter’s contribution is greatest (maximum values of 96.9% and 16.8% per year), while summer’s is the smallest. (2) f5 exhibits a significant decline trend across the entire NWP basin (of −0.15 to −0.30%/yr), with the steepest decline occurring in autumn (−0.69%/yr) and the shallowest in summer. f7 exhibits a significant linear decrease in the open ocean east of Japan (−0.08%/yr) while showing a significant linear increase in the waters east of the Kamchatka Peninsula (0.08%/yr). Both variations peak in winter (maximum values of −0.27% and 0.30% per year) and are smallest in summer. (3) Seasonal and regional variations in climate index–f5 and f7 relationships reflect large-scale atmospheric modulation of waves. For example, the Oceanic Niño Index shows a predominantly negative correlation with f5 in winter (maximum correlation coefficient rm = −0.70) around the Luzon Strait, shifting to a significant positive correlation in summer (rm = 0.70) across the extensive region east of Taiwan Island and the Philippines. The Pacific Decadal Oscillation index shows a significant positive correlation with f7 in summer and autumn (rm = 0.69) east of Taiwan Island and a strong negative correlation in winter (rm = −0.77) to the east of Kamchatka Peninsula.

Background When the skin is damaged and its barrier function is disrupted, the proliferation and migration of epidermal keratinocytes are vital for repairing the damaged area. The Schumann resonance at 7.8 Hz has been reported to protect rat cardiomyocytes against oxidative stress and inhibit the proliferation of B16 mouse melanoma cells. However, its effect on the skin is unknown. Aims In this study, we applied 7.8‐Hz electromagnetic waves to normal human epidermal keratinocytes (NHEKs) and investigated its effects on cell proliferation and migration, β‐defensin (DEFB1) and sirtuin 1 (SIRT1) expression. Methods We performed cell proliferation assay, cell migrationassay and gene expression analysis of DEFB1 and SIRT1. Results We found that the application of 7.8‐Hz electromagnetic waves caused a 2.8‐fold increase in NHEK proliferation, enhanced cell migration, and increased the expression of DEFB1 and SIRT1 by 2.4‐fold and 4.9‐fold, respectively. Conclusions These results suggest that the application of 7.8‐Hz electromagnetic waves may contribute to improving the skin barrier function and skin ulcer.

The generation of broadband wave energy frequency spectra from narrowband wave forcing in geophysical flows remains a conundrum. In contrast to the long-standing view that nonlinear wave–wave interactions drive the spreading of wave energy in frequency space, recent work suggests that Doppler-shifting by geostrophic flows may be the primary agent. We investigate this possibility by ray tracing a large number of inertia–gravity wave packets through three-dimensional, geostrophically turbulent flows generated either by a quasigeostrophic (QG) simulation or by synthetic random processes. We find that, in all cases investigated, a broadband quasi-stationary inertia–gravity wave frequency spectrum forms, irrespective of the initial frequencies and wave vectors of the packets. The frequency spectrum is well represented by a power law. A possible theoretical explanation relies on the analogy between the kinematic stretching of passive tracer gradients and the refraction of wave vectors. Consistent with this hypothesis, the spectrum of eigenvalues of the background flow velocity gradients predicts a frequency spectrum that is nearly identical to that found by integration of the ray tracing equations.