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A high-sensitivity temperature sensor based on gold-coated D-shaped photonic crystal fiber is proposed in this paper. To enhance the sensing performances, gold as the surface plasmon resonance material is coated on the polishing surface. The thermosensitive liquid consists of ethanol and chloroform, and it is placed on the outer layer of the photonic crystal fiber. As the phase-matching condition is satisfied, the core mode couples to the surface plasmon polariton mode, and energy transfer occurs. The influences of the structural parameters on the sensing characteristics were studied using the finite element method. The numerical results show the average sensitivity can reach up to 10.61 nm/°C, and the linearity R^2=0.99341 for the temperature sensing ranges of 0–60°C. Moreover, a good spectral shape can be realized by the proposed fiber. Compared with some previously reported temperature sensors, the proposed temperature sensor shows excellent performances in terms of the sensitivity, detection range, and fabrication.

Whistler mode hiss acts as an important loss mechanism contributing to the radiation belt electron dynamics inside the plasmasphere and plasmaspheric plumes. Based on Van Allen Probes observations from September 2012 to December 2015, we conduct a detailed analysis of hiss properties in plasmaspheric plumes and illustrate that corresponding to the highest occurrence probability of plumes at L= 5.0–6.0 and MLT = 18–21, hiss emissions occur concurrently with a rate of >~80%. Plume hiss can efficiently scatter ~10‐ to 100‐keV electrons at rates up to ~10−4s−1near the loss cone, and the resultant electron loss timescales vary largely with energy, that is, from less than an hour for tens of kiloelectron volt electrons to several days for hundreds of kiloelectron volt electrons and to >100 days for >5‐MeV electrons. These newly obtained statistical properties of plume hiss and associated electron scattering effects are useful to future modeling efforts of radiation belt electron dynamics. Plume hiss occurs concurrently with a rate of >~80%, corresponding to the highest occurrence rate of plumes at L= 5.0‐6.0 and MLT = 18‐21Plume hiss is efficient for pitch angle scattering ~10‐ to 100‐keV electrons near the loss conePlume hiss can drive more efficient scattering of >500‐keV electrons at higher L‐shells than normal frequency hiss at lower L‐shells

Scattering by plasmaspheric hiss is responsible for the newly reported reversed energy spectra with abundant high‐energy but fewer low‐energy electrons between hundreds of kiloelectronvolts and ~2 MeV in the inner magnetosphere. To deepen our understanding of the contributions of plasmaspheric hiss to the formation of reversed electron energy spectrum, we conduct a detailed theoretical parametric analysis through numerical simulations to explore the sensitivity of hiss‐induced reversed electron energy spectrum to ambient magnetic field, plasma density, and hiss wave distribution properties. Given L‐shell, variations of ambient plasma density and wave frequency spectrum contribute importantly to the formation of reversed electron energy spectrum, while variations of background magnetic field (which usually shows small changes in the plasmasphere) and wave normal angle distribution play a less effective role. Our study suggests that the reversed electron energy spectrum has important implications for unveiling the sophisticated energy‐dependent nature of wave‐particle interactions and energetic particle dynamics in geospace. Variations of ambient plasma density and wave frequency spectrum contribute importantly to the formation of reversed electron energy spectraVariations of background magnetic field and wave normal angle distribution play a less effective roleReversed energy spectra are more likely to form and evolve more pronouncedly at lower pitch angles

Both magnetosonic (MS) waves and plasmaspheric hiss can resonantly scatter outer radiation belt electrons, leading to various electron pitch angle distribution. Based on electron diffusion coefficients calculations and 2‐D Fokker‐Planck diffusion simulations, we perform a parametric study to quantitatively investigate the net electron scattering effect and the relative contributions of simultaneously occurring hiss and MS waves with groups of different wave amplitude combinations. It is found that the combined scattering effects are dominated by pitch angle scattering due to hiss emissions at L= 4, when their amplitude is comparable to or stronger than that of MS waves, thereby producing the butterfly, top‐hat, flat‐top, and pancake pitch angle distributions, while the butterfly distributions can evolve over a broader energy range when MS waves join the combined scattering effects. Our results demonstrate that the relative intensities of various plasma waves play an essential role in controlling the radiation belt electron dynamics. The Earth's outer radiation belt electrons exhibit high dynamics in terms of both pitch angle and energy distributions. Because MS waves and hiss can frequently occur simultaneously inside the plasmasphere, it is important to understand their combined scattering effects on and relative contributions to the radiation belt electron dynamics. Although a number of case studies have been performed to analyze the consequences of combined scattering by these two concurrently occurring plasma waves, there lack parametric and comprehensive investigations to look into the combined scattering effects corresponding to groups of different intensities of the two wave modes. In this letter, by combining the calculations of wave‐induced electron diffusion coefficients and 2‐D Fokker‐Plank diffusion simulations, we quantitatively analyze electron pitch angle and energy distributions under the impacts of 255 different wave amplitude combinations of these two wave modes, which can lead to top‐hat, pancake, flat‐top, and butterfly PADs. Our results indicate that the relative wave amplitudes of these two waves play an essential role in controlling the dynamic variations of radiation belt electron distribution. A parametric study is performed to investigate the combined electron scattering effect by hiss and MS waves with different wave amplitudesThe combined scattering effect of concurrent hiss and MS waves can lead to top‐hat, flat‐top, pancake, and butterfly PADsThe relative intensities of various plasma waves are important in controlling dynamic variations of radiation belt electron distribution

Electromagnetic ion cyclotron waves have long been recognized to play a crucial role in the dynamic loss of ring current protons. While the field‐aligned propagation approximation of electromagnetic ion cyclotron waves was widely used to quantify the scattering loss of ring current protons, in this study, we find that the wave normal distribution strongly affects the pitch angle scattering efficiency of protons. Increase of peak normal angle or angular width can considerably reduce the scattering rates of ≤10 keV protons. For >10 keV protons, the field‐aligned propagation approximation results in a pronounced underestimate of the scattering of intermediate equatorial pitch angle protons and overestimates the scattering of high equatorial pitch angle protons by orders of magnitude. Our results suggest that the wave normal distribution of electromagnetic ion cyclotron waves plays an important role in the pitch angle evolution and scattering loss of ring current protons and should be incorporated in future global modeling of ring current dynamics. Electromagnetic ion cyclotron (EMIC) wave is a class of electromagnetic wave that is frequently observed in the Earths' magnetosphere. EMIC waves can cause the loss of ring current protons by scattering them into the atmosphere. Previous attempts to quantify the loss of ring current protons by EMIC waves are mostly limited to the assumption that the waves are propagating exactly along the direction of geomagnetic field line. In this study, we show that this assumption will seriously break down once the waves are obliquely propagating. The obliquity of EMIC waves not only influences the pitch angle evolution of ring current protons but also affects their loss time scales. Our study confirms the importance of including the obliquity of EMIC waves in the modeling efforts of ring current dynamics. The wave normal angle distribution strongly affects the EMIC wave‐driven scattering loss of ring current protonsQuantitative differences in the diffusion coefficients between field‐aligned and oblique waves are presentedPitch‐angle scattering of higher‐energy ring current protons is more sensitive to the variation of wave normal angle distribution

Wave‐particle interactions triggered by whistler‐mode chorus waves are an important contributor to the Jovian radiation belt electron dynamics. While the sensitivity of chorus‐driven electron scattering to the ambient magnetospheric and wave parameters has been investigated, there is rather limited understanding regarding the extent to which the dynamic evolution of Jovian radiation belt electrons, under the impact of chorus wave scattering, depends on the electron distribution profiles. We adopt a group of reasonable initial conditions based upon the available observations and models for quantitative analyses. We find that inclusion of pitch angle variation in initial conditions can result in increased electron losses at lower pitch angles and substantially modify the pitch angle evolution profiles of > ~500 keV electrons, while variations of electron energy spectrum tend to modify the evolution primarily of 1 MeV and 5 MeV electrons. Our results explicitly demonstrate the importance to the radiation belt electron dynamics in the Jovian magnetosphere of the initial shape of the electron phase space density, and indicate the extent to which variations in electron energy spectrum and pitch angle distribution can contribute to the evolution of Jovian radiation belt electrons caused by chorus wave scattering.

Plasmaspheric hiss is known to play an important role in radiation belt electron dynamics in high plasma density regions. We present observations of two crossings of a plasmaspheric plume by the Van Allen Probes on 26 December 2012, which occurred unusually at the post‐midnight‐to‐dawn sector between L ~ 4–6 during a geomagnetically quiet period. This plume exhibited pronounced electron densities higher than those of the average plume level. Moderate hiss emissions accompanied the two plume crossings with the peak power at about 100 Hz. Quantification of quasi‐linear bounce‐averaged electron scattering rates by hiss in the plume demonstrates that the waves are efficient to pitch angle scatter ~10–100 keV electrons at rates up to ~10−4s−1near the loss cone but become gradually insignificant to scatter the higher energy electron population. The resultant timescales of electron loss due to hiss in the nightside plume vary largely with electron kinetic energy over 3 orders of magnitude, that is, from several hours for tens of keV electrons to a few days for hundreds of keV electrons to well above 100 days for >1 MeV electrons. Changing slightly with L‐shell and the multiquartile profile of hiss spectral intensity, these electron loss timescales suggest that hiss emissions in the nightside plume act as a viable candidate for the fast loss of the ≲100 keV electrons and the slow decay of higher energy electrons. It is believed that the loss dynamics of radiation belt electrons are coherent with hiss dynamics on spatial scales comparable to the size of the plasmasphere. However, most previous studies focused on the timescale of electron scattering induced by hiss observed in the right plasmasphere. In present work, we first time estimate the electron scattering effect by plasmaspheric hiss in nightside plumes. Moderately strong hiss emissions can occur to peak at ~100 Hz within the two crossings of a pronounced post‐midnight‐to‐dawn plumePlasmaspheric hiss in the nightside plume is efficient to pitch angle scatter ~10–100 keV electronsWith the resultant electron loss timescales varying over 3 orders of magnitude, hiss emissions in the nightside plume can account for the fast loss of ≲100 keV electrons and for the slow decay of higher energy electrons

Bounce resonant interactions with magnetospheric waves have been proposed as an important contributing mechanism for scattering near‐equatorially mirroring electrons by violating the second adiabatic invariant associated with the electron bounce motion along a geomagnetic field line. This study demonstrates that low‐frequency plasmaspheric hiss with significant wave power below 100 Hz can bounce resonate efficiently with radiation belt electrons. By performing quantitative calculations of pitch angle scattering rates, we show that low‐frequency hiss‐induced bounce resonant scattering of electrons has a strong dependence on equatorial pitch angle αeq. For electrons with αeqclose to 90°, the timescale associated with bounce resonance scattering can be comparable to or even less than 1 h. Cyclotron and Landau resonant interactions between low‐frequency hiss and electrons are also investigated for comparisons. It is found that while the bounce and Landau resonances are responsible for the diffusive transport of near‐equatorially mirroring electrons to lower αeq, pitch angle scattering by cyclotron resonance could take over to further diffuse electrons into the atmosphere. Bounce resonance provides a more efficient pitch angle scattering mechanism of relativistic (≥1 MeV) electrons than Landau resonance due to the stronger scattering rates and broader resonance coverage of αeq, thereby demonstrating that bounce resonance scattering by low‐frequency hiss can contribute importantly to the evolution of the electron pitch angle distribution and the loss of radiation belt electrons. Low‐frequency hiss can bounce‐resonate efficiently with near‐equatorially mirroring electronsBounce resonance has a strong dependence on electron equatorial pitch‐angleQuantitative differences are presented among the bounce, cyclotron and Landau resonant scattering of electrons.

A generalized finite-difference (FD) scheme combined with the measured equation of invariance (MEI) is presented for the analysis of electromagnetic scattering from an inhomogeneous and lossy chiral cylinder with electrically large, arbitrarily shaped cross section. A new FD mesh in both chiral and achiral regions is formed, and the FD equations in a chiral medium are derived; then a large sparse matrix is formulated. The numerical results of bistatic scattering width (two-dimensional radar cross section) are given for the chiral cylinders of rectangular, elliptical, and complex cross section, respectively. Some results are compared with available data.

Abstract: Groove guide is one of the waveguides that have been used at millimeter and submillimeter waveband. This paper analyzes arbitrary groove guides by means of the eigen-weighted boundary integral equation method that uses the eigenfunctions of a fictitious regular boundary as weighting functions. In comparison with the theoretical and experimental results published, the numerical results for rectangular, circular and V-groove guides using this method are exact enough with fast convergence and less calculation.

Based on Van Allen Probes observations, in this study we perform a statistical analysis of the spectral intensities of plasmaspheric hiss at L‐shells of 1.8–3.0 in the slot region. Our results show that slot region hiss power intensifies with a strong day‐night asymmetry as the level of substorm activity or L‐shell increases. Using the statistical spectral profiles of plasmaspheric hiss, we calculate the drift‐ and bounce‐averaged electron pitch angle diffusion coefficients and subsequently obtain the resultant electron loss timescales through 1‐D Fokker‐Planck simulations. We find that slot region electron loss timescales vary significantly from <1 day to several years, showing a strong dependence on electron energy, L‐shell and substorm activity. We also construct an empirical model of slot region electron loss timescales due to scattering by plasmaspheric hiss, which agrees well with the 1‐D simulation results and can be readily used in modeling the dynamics of slot region electrons. We perform a statistical analysis of the global distribution of hiss wave spectral intensities in the slot regionThe drift‐ and bounce‐averaged pitch angle diffusion coefficients of slot region electrons are calculatedWe develop an empirical model of slot region electron loss timescales due to plasmaspheric hiss We perform a statistical analysis of the global distribution of hiss wave spectral intensities in the slot region The drift‐ and bounce‐averaged pitch angle diffusion coefficients of slot region electrons are calculated We develop an empirical model of slot region electron loss timescales due to plasmaspheric hiss

Radiation belt electrons have a complicated relationship with geomagnetic activity. We select electron measurements from 7 years of DEMETER and 6 years of Van Allen Probes data during geomagnetic storms to conduct statistical analysis focusing on the correlation between electron flux and Dst index. We report, for the first time, an upper limit of electron fluxes observed by both satellites throughout the inner and outer belts across a wide energy range from ∼100s keV to multi‐MeV. The upper flux limit is determined at different L's and energies, for example, 1.9 × 107/cm2‐s‐sr‐MeV at 470 keV at L= 1.5 and 3.6 × 105/cm2‐s‐sr‐MeV at 3.4 MeV at L= 4 (Van Allen Probes). We present the energy spectra of the electron flux upper limit at different Lshells and find the measured upper flux limit to be at least three times higher than the predicted flux from the AE8/AE9 models, although the spectral shape is remarkably similar. We show that the average flux with an applied time lag is better correlated with the Dst index and that the time lag optimizing the correlation coefficient is larger at lower Land at higher energies. These findings present the underlying challenges to model the dynamic variation of relativistic electrons in the inner magnetosphere and are important information for space weather considerations. Upper limit of electron fluxes during storm times is observed by both DEMETER and the Van Allen ProbesThe upper limit of electron flux is higher than the AE8/AE9 model predictions, though the spectral shape is remarkably similarElectrons at lower Land higher energy take longer time to fully respond to geomagnetic storms Upper limit of electron fluxes during storm times is observed by both DEMETER and the Van Allen Probes The upper limit of electron flux is higher than the AE8/AE9 model predictions, though the spectral shape is remarkably similar Electrons at lower Land higher energy take longer time to fully respond to geomagnetic storms

Strong electrostatic electron cyclotron harmonic (ECH) waves on the dayside magnetosphere have been reported based on observations of the Magnetospheric Multiscale (MMS) spacecraft. In this study, we analyze high‐quality wave data from the four MMS satellites between 1 September 2015 and 30 August 2018 to investigate the statistical properties of dayside ECH emissions. The results show that dayside ECH waves are preferentially observed on the prenoon side in the outer magnetosphere (L= 8–12), with average wave amplitude Ew> 0.1 mV/m. In addition, besides the typical near‐equatorial (|MLAT| ≤ 15°) region, dayside ECH waves exhibit moderate occurrence rate and wave amplitude in higher latitudinal regions (i.e., 15 < |MLAT| ≤ 40°), possibly due to the off‐equatorial geomagnetic field minimum. Our reported double peaks of dayside ECH wave occurrence zone and considerable occurrence rates of prenoonside ECH waves suggest that dayside ECH waves can be a potentially important contributor to the formation of dayside diffuse aurora. We use wave spectral data from the four Magnetospheric Multiscale (MMS) spacecraft to statistically analyze the distributions of wave amplitudes and occurrence rates as a function of Lshell, MLT, geomagnetic activity (AE* and Kp indices), and MLAT for dayside first harmonic band electron cyclotron harmonic (ECH) waves. The conclusions are summarized as follows: (1) Dayside ECH waves preferentially occur on the prenoonside of the outer magnetosphere, with peak occurrence rates around 30%. (2) In higher latitudinal regions (|MLAT| = 15–25°,25–40°), contrary to previous conclusions regarding ECH wave occurrence patterns, dayside ECH waves occur with significant occurrence rates, comparable to that of dayside ECH waves in near‐equatorial areas. (3) Similar to the distribution of occurrence rates, dayside ECH waves have most intense electric field amplitudes over L= 8–12, MLT = 8–11, with an average wave strength >0.1 mV/m.Whistler mode chorus waves are considered as the primary mechanism to explain dayside diffuse aurora, but the role of ECH waves has not been systematically evaluated because of lack of dayside ECH observations. As shown by our results, moderate dayside ECH waves can be observed on the prenoonside of the outer magnetosphere. This observation could be of great importance in understanding the generation of dayside diffuse aurora. Dayside ECH waves are preferentially observed with moderate average wave strength on the prenoonside to noonside in the outer magnetosphereIn higher latitudinal regions, dayside ECH waves have comparable occurrence rates and wave amplitude to that of the near‐equatorial regionsAlthough weak dayside ECH waves occur predominantly, the occurrence rates of moderate and strong dayside ECH waves are not negligible

By investigating the resonant energy and latitudinal resonance region of Landau resonance between H+band electromagnetic ion cyclotron (EMIC) waves and radiation belt electrons and performing calculations of quasi‐linear diffusion coefficients, we find that Landau resonance with EMIC waves, characterized by a very broad range of resonant energies from below 1 eV to above 10 MeV and the strikingly small extent of the latitudinal resonance region well below 0.1°, can be a feasible candidate accounting for the pitch angle scattering of near‐equatorially mirroring electrons. Compared to the dominant pitch angle scattering caused by the cyclotron resonance for greater than ~2‐MeV electrons at equatorial pitch angles less than ~80° with the rates well above 10−4s−1, Landau resonance with H+band EMIC waves has the potential to drive more efficient pitch angle scattering of radiation belt electrons from ~10 MeV down to tens of kiloelectron volts at equatorial pitch angles greater than ~ 85°. Electromagnetic ion cyclotron (EMIC) waves are thought to be very important for pitch angle scattering of radiation belt electrons, which may play a crucial role for the rapid dropout of relativistic electrons fluxes in the outer radiation belt during a geomagnetic storm, or for the intense relativistic electron precipitation. Although cyclotron resonance with EMIC waves acts as an important loss process during geomagnetic storms, this mechanism is believed to solely affect trapped electrons with small pitch angles well away from 90°. In the present work, we introduce the Landau resonance between H+band EMIC waves and radiation belt electrons. The crucial role for pitch angle scattering near‐equatorially mirroring electrons by Landau resonance is investigated by Quasilinear diffusion theory (QLT) calculations in our work. H+band EMIC waves drive the Landau resonance with radiation belt electrons over a very broad energy range from >10 MeV to tenths of an eVLandau resonance between H+band EMIC waves and electrons at > ~60 degrees occurs in a very limited rangeEMIC scattering electrons due to the cyclotron resonance and Landau resonance occur at two distinct ranges of equatorial pitch angle

We report a typical event that fast magnetosonic (MS) waves, exohiss, and two‐band chorus waves occurred simultaneously on the dayside observed by Van Allen Probes on 25 December 2013. By combining calculations of electron diffusion coefficients and 2‐D Fokker‐Planck diffusion simulations, we quantitatively analyze the combined scattering effect of multiple waves to demonstrate that the net impact of combined scattering does not simply depend on the wave intensity dominance of various plasma waves. Although the observed MS waves are most intense, the electron butterfly distribution is inhibited by exohiss and chorus, and electrons are considerably accelerated by combined scattering of MS and chorus waves. The simulated electron pitch angle distributions exhibit the variation trend consistent with the observations. Our results strongly suggest that competition and cooperation between resonant interactions with concurrently occurring magnetospheric waves need to be carefully treated in modeling and comprehending the radiation belt electron dynamics. It has been acknowledged that wave‐particle interactions play an important role in energy exchange between plasma waves and radiation belt electrons. Most previous studies focused on the wave‐particle interaction effect of individual wave modes, while only rather limited investigations look into the competition and cooperation between various kinds of plasma waves upon their modulation of the radiation belt electron dynamics. In the present study, we report a typical event that magnetosonic waves, exohiss, and two‐band chorus waves occurred simultaneously on the dayside. By computations of the electron diffusion coefficients and 2‐D Fokker‐Planck diffusion simulations, we have found that the competition and cooperation between these three wave modes are delicate in that the net combined scattering impact does not simply depend on the dominance of wave intensity but requires careful analyses via diffusion simulations. Our results demonstrate the importance of incorporating the combined scattering effect by various simultaneously occurring magnetospheric waves during modeling and comprehending the complex radiation belt electron dynamics. A typical event that MS waves, exohiss, and two‐band chorus waves occurred simultaneously in the dayside plasmatrough is reportedThe combined scattering effect makes a big difference to the radiation belt electron dynamics compared to contributions of individual wavesNumerical simulations can approximately explain the variation trend of observed electron pitch angle distributions