In the era of the Internet of Things (IoT), the provision of sustainable power to distributed, mobile, and low-power-consumption electronic devices is a critical challenge. To overcome this ...challenge, the triboelectric nanogenerator (TENG), a highly efficient high-entropy mechanical energy harvesting device, was developed in 2012. This device enables the direct conversion of irregular and low-frequency mechanical energy into pulsed alternating current (AC) signals. However, the incompatibility of most electronic devices with AC signals necessitates rectifier circuits or generators that deliver direct current (DC) signals. In recent years, DC-TENGs have undergone extensive development, achieving significant milestones in various application fields while also facing crucial challenges that require solutions. In this review, three categories of DC-TENG devices with distinct operating mechanisms are comprehensively explored: multiphase coupling, mechanical rectification, and air breakdown. Their typical structures and working mechanisms are thoroughly discussed, and specific output performance limitations, along with corresponding optimization strategies, are identified. Furthermore, the applications of DC-TENGs in various scenarios are summarized. Finally, the challenges faced by DC-TENGs and potential solutions are analyzed to guide further advancements in this technology.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Dietary habits are essential in the mean age at menarche (AAM). However, the causal relationship between these factors remains unclear. Therefore, this study aimed to elucidate the genetic ...relationship between dietary habits and AAM. Genetic summary statistics for dietary habits were obtained from the UK Biobank. GWAS summary data for AAM was obtained from the ReproGen Consortium. Linkage disequilibrium score regression was used to test genetic correlations between dietary habits and AAM. The Mendelian randomization (MR) analyses used the inverse-variance weighted method. Genetic correlations with AAM were identified for 29 candi-date dietary habits, such as milk type (skimmed, semi-skimmed, full cream; coefficient = 0.2704, P
= 1.13 × 10
). MR evaluations revealed that 19 dietary habits were associated with AAM, including bread type (white vs. any other; OR 1.71, 95% CI 1.28-2.29, P
= 3.20 × 10
), tablespoons of cooked vegetables (OR 0.437, 95% CI 0.29-0.67; P
= 1.30 × 10
), and cups of coffee per day (OR 0.72, 95% CI 0.57-0.92, P
= 8.31 × 10
). These results were observed to be stable under the sensitivity analysis. Our study provides potential insights into the genetic mechanisms underlying AAM and evidence that dietary habits are associated with AAM.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Abstract
The whistler-mode wave is an electromagnetic wave that commonly occurs in space plasma and has been extensively studied, especially within the Earth's magnetosphere. They have also been ...reported in the near-Mars space, such as Martian upstream solar wind, crustal magnetic field, ionopause, and the magnetic reconnection ion diffusion region. However, the generation of whistler-mode waves in the Martian magnetotail current sheet is still unclear. Based on observations made by Mars Atmosphere and Volatile Evolution spacecraft, we report whistler-mode waves observed within a train of proton-scale magnetic dips during a Martian magnetotail current sheet crossing. The linear growth rate analyses demonstrate that the whistler-mode waves are locally generated within the magnetic dips. Unlike in Earth's plasma environment, the train of magnetic dips in the Martian plasma sheet is attributed to electron mirror-mode instability. Our finding suggests that the mirror-mode structure in the Martian magnetotail can be an important source region for generating whistler-mode waves. This provides a new insight into how whistler-mode waves are generated in unmagnetized planets.
Using the high‐time‐resolution data from the Magnetospheric Multiscale mission, precursor waves upstream of foreshock transient (FT) shocks are statistically investigated using the four‐spacecraft ...timing method. The wave frequencies and wave vectors determined in the plasma rest frame (PRF) are shown to follow the cold plasma dispersion relation for whistler waves. Combining with the feature of the right‐hand polarization in the PRF, the precursors are identified as whistler‐mode waves around the lower hybrid frequency. The occurrence of whistler precursors is independent of the Alfvén Mach number and the FT shock normal angle. More importantly, all the whistler precursors have group velocities pointing upstream in the shock frame, suggesting the dispersive radiation to be a possible generation mechanism. The study improves the understanding of not only the whistler precursors but also the overall FT shock dynamics.
Plain Language Summary
The characteristics of the precursor waves upstream of foreshock transient (FT) shocks are determined in the plasma rest frame using the multi‐point measurements from the Magnetospheric Multiscale mission with appropriate separation scales. The statistical results demonstrate for the first time that the precursors upstream of FT shocks are lower hybrid frequency whistler‐mode waves. The presence or absence of large amplitude whistler precursors does not depend on the FT shock normal angle and the Alfvén Mach number. These results have important implications on the nature of the whistler precursors and the dynamics of the FT shocks.
Key Points
Precursor waves upstream of foreshock transient shocks are found to follow the whistler wave dispersion relation in the plasma rest frame
The occurrence of whistler precursors is independent of the Alfvén Mach numbers and normal angles of the foreshock transient shocks
The observed wave characteristics are consistent with that the precursors are generated through the dispersive radiation mechanism
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
The stunning tails of comets are interesting astronomical phenomena to human beings and have been noticed for thousands of years. The bright tails also emit substantial materials into interplanetary ...space, including dusts and charged particles. The charged particles are picked up by solar wind magnetic fields, and thus could propagate together with solar wind to influence planetary space environments. Simultaneous measurements of comet materials, planetary space, and ground environments are crucial for understanding cometary impacts to planets, while such observations are quite rare. In this article, we present a full chain from the comet tail, to the solar wind cometary particles, and the impacts on the ground. Intense auroral events are observed when the cometary materials are observed in the Earthʼs upstream solar wind. Our results provide direct evidence that cometary ions could contribute substantial dynamic pressure in driving geomagnetic activities and the associated auroral intensifications.
Terrestrial auroras are highly structured that visualize the perturbations of energetic particles and electromagnetic fields in Earth’s space environments. However, the identification of auroral ...morphologies is often subjective, which results in confusion in the community. Automated tools are highly valuable in the classification of auroral structures. Both CNNs (convolutional neural networks) and transformer models based on the self-attention mechanism in deep learning are capable of extracting features from images. In this study, we applied multiple algorithms in the classification of auroral structures and performed a comparison on their performances. Trans-former and ConvNeXt models were firstly used in the analysis of auroras in this study. The results show that the ConvNeXt model can have the highest accuracy of 98.5% among all of the applied algorithms. This study provides a direct comparison of deep learning tools on the application of classifying auroral structures and shows promising capability, clearly demonstrating that auto-mated tools can help to minimize the bias in future auroral studies.
Foreshock cavitons are transient phenomena observed in the terrestrial foreshock region. They are characterized by a simultaneous depression of magnetic field magnitude and plasma density, which are ...bounded with enhancements of these two parameters and surrounded by ultralow frequency (ULF) waves. Previous studies focused on the interplanetary magnetic field (IMF) conditions, solar wind (SW) conditions, and the growth of the foreshock waves related to the generation of foreshock cavitons. Previously, a multipoint spacecraft analysis method using Cluster data was applied to analyze only two foreshock cavitons, and this method did not consider uncertainties. In this study, multipoint spacecraft analysis methods, including the timing method, the minimum directional derivative (MDD) method, and the spatiotemporal difference (STD) method are applied to determine the velocity in both spacecraft and solar wind frames. The propagation properties show good agreement with previous results from simulations and observations that most cavitons move sunward in the solar wind frame, with the velocities larger than the Alfvén speed. The propagation properties of foreshock cavitons support the formation mechanism of cavitons in previous simulations, which suggested that cavitons are formed due to the nonlinear evolution of compressive ULF waves. We find that there is clear decreasing trend between the size of cavitons and their velocity in the solar wind frame. In addition, the timing method considering errors has been applied to study the evolution properties by comparing the velocities with errors of the leading and trailing edges, and we identify three stable cavitons and one contracting caviton, which has not been studied before. Most cavitons should remain stable when they travel toward the Earth’s bow shock. The relationship between the size of foreshock cavitons and their distance from the bow shock is also discussed.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Ultra-low-frequency (ULF) waves are ubiquitous in the magnetosphere. Previous
studies mostly focused on ULF waves in the dayside or near-Earth region (with
radial distance R<12 RE). In this study, ...using the
data of the Time History of Events and Macroscale Interactions during
Substorms (THEMIS) mission during the period from 2008 to 2015, the Pc5–6
ULF waves in the tail region with
XGSM∗<0, 8 RE<R<32 RE (mostly on the stretched magnetic field lines) are
studied statistically. A total of 1089 azimuthal oscillating events and
566 radial oscillating events were found. The statistical results show that
both the azimuthal and radial oscillating events in the magnetotail region
(12 RE<R<32 RE) are more
frequently observed in the post-midnight region. The frequency decreases with
increasing radial distance from Earth
for both azimuthal oscillating events (8 RE<R<16 RE) and radial oscillating events (8 RE<R<14 RE), which is consistent with the
field line resonances theory. About 52 % of events (including the
azimuthal and radial oscillating events) are standing waves in the region of
8–16 RE, while only 2 % are standing waves in the region of
16–32 RE. There is no obvious dawn–dusk asymmetry of ULF wave
frequency for events in 8 RE<R<32 RE, which contrasts with the obvious dawn–dusk asymmetry
found by previous studies in the inner magnetosphere (4 RE<R<9 RE). An examination for possible
statistical relationships between the ULF wave parameters and substorm
occurrences is carried out. We find that the wave frequency is higher after
the substorm onset than before it, and the frequency differences are more
obvious in the midnight region than in the flank region.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Jupiter’s unique x-ray aurora is driven by the same processes as Earth’s: Heavy ion scattering by electromagnetic waves.
Jupiter’s rapidly rotating, strong magnetic field provides a natural ...laboratory that is key to understanding the dynamics of high-energy plasmas. Spectacular auroral x-ray flares are diagnostic of the most energetic processes governing magnetospheres but seemingly unique to Jupiter. Since their discovery 40 years ago, the processes that produce Jupiter’s x-ray flares have remained unknown. Here, we report simultaneous in situ satellite and space-based telescope observations that reveal the processes that produce Jupiter’s x-ray flares, showing surprising similarities to terrestrial ion aurora. Planetary-scale electromagnetic waves are observed to modulate electromagnetic ion cyclotron waves, periodically causing heavy ions to precipitate and produce Jupiter’s x-ray pulses. Our findings show that ion aurorae share common mechanisms across planetary systems, despite temporal, spatial, and energetic scales varying by orders of magnitude.
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