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This manuscript utilizes the global survey of electron precipitation due to chorus and hiss waves based on waves and electron flux measurements made by Van Allen Probes. To analyze the loss‐cone precipitation presented in these papers, we compared electron energy fluxes and their mean energies entering the ionospheric altitudes on the global scale based on UCLA Full Diffusion (UCLA code) and NASA SuperThermal ElecTrons codes and reveal the role of magnetosphere‐ionosphere‐atmosphere (MIA) energy interplay in the formation these values. This information is used for calculation of height‐integrated ionospheric conductance in the presence of both hiss and chorus waves activities involving in electron precipitation of energy fluxes. MIA coupling phenomena increases Pederson and Hall conductance up to factors of 2–2.3 and 1.7–1.9, correspondingly. Plain Language Summary Whistler‐mode chorus and hiss waves are two major modes of electromagnetic plasma waves in the Earth's inner magnetosphere. These waves play the major role in the pitch angle scattering of electrons in Earth's magnetosphere, provide the major precipitating energy input to the ionosphere, lead to diffuse aurora and enhance the energy fluxes into the ionosphere. The contribution of these waves in the calculation of height‐integrated ionospheric conductance is non‐linear and requires specific treatment of their total energy fluxes and their mean energies when considering the MIA energy interplay with participation of two magnetically conjugate northern and southern hemispheres. We combine the simulation techniques of magnetospheric precipitation and MIA coupling codes to quantify the wave‐driven precipitation and impacts on ionospheric conductance. Our study demonstrates the enhanced electron precipitation impacts due to chorus and hiss waves when the MIA coupling processes are considered, compared to the previous modeling results which only consider the energy input from the magnetosphere to the ionosphere. Key Points UCLA and NASA SuperThermal ElecTrons codes in the estimation of loss‐cone electron precipitation The role of MIA energy interplay in the calculation of height‐integrated ionospheric conductance Height‐integrated ionospheric conductance in the presence of both hiss and chorus waves

Plasmaspheric hiss waves play a key role in scattering energetic electrons and are often modeled in the inner magnetosphere using empirical hiss power maps parameterized by L shell. In this study, we compare the dependence of hiss power on both L shell (2 ≤ L ≤ 6) and the ratio of electron plasma frequency to electron gyrofrequency (ωpe/Ωce) using observations from the Van Allen Probes. The statistical comparison spans a wide range of magnetic local times, frequency bands, and substorm activity levels. Hiss power shows a stronger correlation with ωpe/Ωce than with L shell, especially at low frequencies and during periods of enhanced substorm activity. These results indicate that ωpe/Ωce is a more physically meaningful parameter for describing plasmaspheric hiss and should be considered in radiation belt modeling. Plain Language Summary Plasmaspheric hiss waves are a type of electromagnetic wave in the inner magnetosphere, named for the hiss sound when converted to audio. These waves are mainly found in the plasmasphere and play a critical role in regulating the radiation belts. By scattering high‐energy electrons through wave‐particle interactions, plasmaspheric hiss contributes to the loss of electrons to the atmosphere and the formation of the slot region, a low‐radiation zone between the inner and outer belts. In this study, we use observations from NASA's Van Allen Probes to investigate how hiss wave intensity varies with both L shell and local plasma conditions. In particular, we examine the ratio of electron plasma frequency to electron gyrofrequency, which reflects electron density and magnetic field strength. Our analysis shows that hiss wave power is more strongly related to the frequency ratio than to the L shell, especially at lower frequencies and during enhanced substorm activity. These results hold significant implications, challenging the adequacy of current magnetospheric models that primarily consider radial distance as their fundamental organizing parameter. Key Points The first statistical comparison of hiss wave power dependence on L shell and ωpe/Ωce is performed Hiss wave power correlates more strongly with ωpe/Ωce than with L shell or ne The ωpe/Ωce dependence is strongest at low frequencies and during enhanced substorm activity

Plasmaspheric hiss waves are important to shape the Earth’s electron radiation belt. These waves are commonly envisioned to have a long lifetime which allows them to permeate the global plasmasphere from a spatially restricted source. However, this hypothesis has not been experimentally confirmed yet, because of the challenging observational requirements in terms of location and timing. With wave and particle measurements from five magnetospheric satellites and detailed modeling, we present the first report of long lifetime (∼42 s) hiss rays in the substorm‐disturbed plasmasphere. The low‐frequency hiss waves are found to originate from the middle piece of the plasmaspheric plume, bounce between two hemispheres, and eventually drift into the plasmaspheric core. These hiss rays can travel through ∼3 hr magnetic local time and ∼4 magnetic shell. Such a long‐time and large‐scale permeation of hiss rays could benefit from the ducting process by plasmaspheric field‐aligned density irregularities. Plain Language Summary Earth’s plasmasphere is populated by a type of whistler‐mode wave named plasmaspheric hiss which is able to shape the electron radiation belt. Hiss waves were commonly envisioned to have a long lifetime which allows them to permeate the global plasmasphere from a spatially restricted source. Although there have been numerous studies on the source of plasmaspheric hiss waves, the hypothesis regarding their long lifetime remains not experimentally confirmed yet because of the challenging observational requirements in terms of location and timing. On the basis of wave and particle measurements from five magnetospheric satellites covering the entire plasmasphere and detailed modeling, we show that the hiss rays can survive at least 42 s in the plasmasphere disturbed by substorms. Within the survival period, these hiss rays migrated from the middle piece of the plasmaspheric plume to the plasmaspheric core, whose path lengths reached 25 Earth radii. Such a long‐time and large‐scale permeation of hiss rays from the plasmaspheric plume to the plasmaspheric core could benefit from the ducting process by plasmaspheric field‐aligned density irregularities. Key Points Low‐frequency hiss waves were excited by energetic electrons inside the dayside plasmaspheric plume following substorms Low‐frequency hiss rays survived at least 42 s, allowing themselves to migrate from the plasmaspheric plume to the plasmaspheric core Plasmaspheric density ducts facilitated the permeation of hiss rays from the plasmaspheric plume to the plasmaspheric core

In this study, we statistically analyze the wave properties of plasmaspheric hiss using data from the Van Allen Probes. The magnetic power spectral densities of hiss waves exhibit dependence on magnetic local time, geomagnetic activity, and the L$L$ ‐shell. Based on variations in wave properties—including normal angle, electromagnetic planarity, and the net Poynting flux direction Rs$\\left({R}_{s}\\right)$ —with L$L$ ‐shell and normalized frequency (the ratio of wave frequency to electron cyclotron frequency), hiss waves are categorized into four distinct regions. Waves with frequencies above 0.1fce$0.1{f}_{ce}$exhibit characteristics of locally generated plasmaspheric hiss. Furthermore, the statistical distribution of suprathermal electron fluxes shows that the upper energy of injected energetic electrons matches well with the minimum resonant energy corresponding to the lower frequency of locally generated hiss. This study identifies locally generated hiss waves, which are well supported by the electron distributions. Plain Language Summary Whistler‐mode plasmaspheric hiss waves occur in near‐Earth space and are named for their distinct hiss‐like sound. These waves primarily exist in dense plasma regions and play a critical role in electron loss of Earth's radiation belts, particularly by scattering high‐energy electrons. Plasmaspheric hiss waves are crucial for understanding Earth's radiation belt dynamics, though their potential generation mechanisms remain under active investigation. In this study, we used data from the Van Allen Probes to analyze how wave properties depend on the L$L$shell and normalized frequency, identifying regions of locally generated plasmaspheric hiss. We also incorporated statistical data on electron distributions to confirm that hiss waves above approximately 0.1 times the electron cyclotron frequency at large L$L$shells are locally generated. This study validates the mechanism of local generation and provides insights to support future research on the origins of plasmaspheric hiss. Key Points The locally generated hiss waves are identified based on the wave properties The suprathermal electron features in the plasmasphere are statistically analyzed The distributions of suprathermal electrons and corresponding growth rates well support the local generation of identified hiss

We present a novel method to quantify the event‐specific spatial evolution of plasmaspheric hiss wave power using a Drift‐Diffusion model. Constrained by Polar Operational Environmental Satellites/Meteorological Operational Satellites data, the model simulates low‐altitude electron distributions, accounting for azimuthal drift, pitch‐angle diffusion, and atmospheric backscatter. Applying to an event on 15 October 2016, the model quantifies the spatial evolution of hiss waves at L = 3.9, which contributes to the steady decay of electron flux observed by Van Allen Probes (VAPs). The model reproduces local‐time dependent features and shows excellent agreement with hiss wave power observed by VAPs. The model shows increased wave power and spatial spread following increased activities in the AL‐index, consistent with previous statistical results. The model also suggests the presence of “low”‐frequency hiss, which was undetected by VAPs, likely masked by instrument noise. This is the first time low‐altitude measurements are used to quantify event‐specific wave distributions which include both diffusion and drift effects. Plain Language Summary We present a novel method to estimate the location and strength of plasmaspheric hiss waves in the Earth's magnetosphere during specific events. These waves play a critical role in shaping the dynamics of Earth's radiation belts by scattering energetic electrons into the atmosphere. However, directly measuring these waves everywhere in the magnetosphere is unfeasible given the inherent limited coverage of satellites. Our approach uses a Drift‐Diffusion model, a physics‐based simulation on how electrons behave in the presence of these waves, and through iteratively best‐fitting model to observations from Polar Operational Environmental Satellites/Meteorological Operational Satellites, we can quantify the free parameters in the model, such as wave power and its location. The model shows remarkable agreement with hiss wave observations from Van Allen Probes (VAPs) during an event on 15 October 2016. It also shows how the waves intensify and spread following increases in AL‐index activity, consistent with past statistical studies. The model also suggests the presence of “low”‐frequency hiss waves, though they were not detected by VAPs, likely due to instrument noise. This method provides a powerful tool to study wave activity in areas where direct measurements are unavailable. Key Points A novel method using a Drift‐Diffusion model constrained by Polar Operational Environmental Satellites/Meteorological Operational Satellites data estimates the event‐specific spatial evolution of wave power The model reveals increase in hiss wave power and spatial spread during high AL activity, consistent with previous statistical results The model suggests the presence of low‐frequency hiss waves during the event, though they were not observed by Van Allen Probes

We present statistical distributions of whistler‐mode chorus and hiss waves at frequencies ranging from the local proton gyrofrequency to the equatorial electron gyrofrequency (fce,eq) in Jupiter's magnetosphere based on Juno measurements. The chorus wave power spectral densities usually follow the fce,eq variation with major wave power concentrated in the 0.05fce,eq–fce,eq frequency range. The hiss wave frequencies are less dependent on fce,eq variation than chorus with major power concentrated below 0.05fce,eq, showing a separation from chorus at M < 10. Our survey indicates that chorus waves are mainly observed at 5.5 < M < 13 from the magnetic equator to 20° latitude, consistent with local wave generation near the equator and damping effects. The hiss wave powers extend to 50° latitude, suggesting longer wave propagation paths without attenuation. Our survey also includes the whistler‐mode waves at high latitudes which may originate from the Io footprint, auroral hiss, or propagating hiss waves reflected to high M shells. Plain Language Summary Whistler‐mode chorus and hiss waves in Jupiter's magnetosphere are major plasma wave modes, characterized by perturbations in electric and magnetic fields at frequencies from the proton gyrofrequency to the electron gyrofrequency. Chorus waves are typically observed at 0.05fce,eq–fce,eq frequencies (fce,eq is the electron gyrofrequency at the equator) with coherent wave structures. Chorus waves, generated by hot electrons, could cause electron precipitation into the atmosphere and acceleration in the radiation belt. In contrast, hiss waves are usually incoherent with wave frequencies less dependent on fce,eq than chorus. Hiss waves have mixed sources and mainly drive energetic electron loss. Using Juno satellite measurements, we analyze the statistical distribution of chorus and hiss waves in Jupiter's magnetosphere. Our survey reveals different latitudinal coverages and statistical properties of chorus and hiss waves, suggesting their different sources and damping effects. Additionally, our survey includes whistler‐mode waves at high latitudes, potentially originating from various sources such as the Io footprint at the ionosphere, auroral hiss, or reflection of hiss waves at high M shells. The whistler‐mode wave distributions from our study provide valuable insights for future modeling of whistler‐mode wave sources and energetic electron dynamics in Jupiter's magnetosphere. Key Points Intense chorus waves at 0.05–1 equatorial electron gyrofrequencies (fce,eq) are observed at 5.5 < M < 13 within 20° magnetic latitudes Hiss waves from 50 Hz to 0.05 fce,eq have extended latitudinal coverage up to 50° and exhibit propagation effects High latitude (>50°) whistler‐mode waves at 0.05–1 fce,eq are observed in two groups due to different sources

Hiss waves play a critical role in shaping Earth's radiation belts and mediating magnetosphere‐ionosphere energy transfer. Intense hiss emissions are frequently generated within dynamic plasmaspheric plumes through linear and nonlinear wave‐particle interactions. However, the contribution of plume hiss to the spatial distribution of hiss throughout the plasmasphere is not yet well quantified. In this study, we perform ray‐tracing simulations to investigate the global propagation of plume hiss under varying plume morphologies, including different widths and levels of density lumpiness. We find that most hiss power is confined near the local time sector of the plume. Narrower plumes with embedded density ducts significantly enhance earthward wave guidance into the plasmaspheric core, compared to wide, smooth plumes. Furthermore, a subset of rays guided azimuthally along the plasmapause can serve as seed waves for intense dayside hiss. Our results highlight the role of plume hiss in shaping the global‐scale distribution of hiss waves.

Enhanced radiation in the Earth's atmosphere can pose serious hazards to pilots, aircraft passengers, and commercial space travelers. Recent results have shown, statistically, that there is a strong correlation between dose rates observed by Automated Radiation Measurements for Aerospace Safety (ARMAS) instruments at aviation altitudes (>9 km) and plasmaspheric hiss wave power measured by NASA's Van Allen Probes within the inner magnetosphere. Plasmaspheric hiss waves play a very important role in removing energetic electrons from the Earth's radiation belts by precipitating them into the upper atmosphere. These relativistic electrons generally drift eastwards along closed magnetic drift shells. In this study, we use magnetic conjunction events between ARMAS and the Van Allen Probes to analyze the causality between plasmaspheric hiss waves and enhanced radiation observed at aviation altitude. We specifically study how the size of the conjunction window and a shift in L and MLT of the conjunction window affect the correlation between dose rates and plasmaspheric hiss wave power. This is to determine if the observed enhanced radiation at aviation altitude is indeed caused by the plasmaspheric hiss waves in the inner magnetosphere. The results show that the enhanced radiation levels are only correlated with plasmaspheric hiss waves within conjunction windows of −1 ≤${\\le} $L ≤${\\le} $1 and 0 ≤${\\le} $MLT ≤${\\le} $2. The correlation between dose rate and hiss wave power increases slightly if ARMAS is shifted approximately 1 hr in MLT to the east of the Van Allen Probes, consistent with the drift trajectory of the electrons precipitating into the atmosphere.

The plasmapause is the outer boundary of the plasmasphere and plays a crucial role in the propagation of plasma waves. We statistically investigate the relationship between the distribution of banded hiss and plasmapause locations. Wave power distributions of banded hiss are analyzed in terms of two ways: (a) the distance away from the plasmapause (ΔL) and (b) the equatorial distance away from the Earth. Statistical results show both bands of banded hiss have larger wave powers and occurrence rates near the plasmapause. The frequencies of two banded hiss waves both decrease discernably with increasing L‐shell at most magnetic local time sectors and geomagnetic activities, but remain nearly constant with increasing ΔL. The highly consistent distribution suggests both bands may be generated in the plume region. The correlation between banded hiss waves and plasmapause locations sheds new light on the generation mechanisms of banded hiss waves. Plain Language Summary Plasmaspheric hiss is a whistler‐mode emission with a broad frequency range from ∼20 Hz to several kHz. The wave is generally observed inside the dayside plasmasphere and plumes. Hiss wave powers are modulated by the combining effect of many parameters such as L (the distance of observation away from the Earth), MLT (magnetic local time), geomagnetic activities, and plasmapause locations. Owing to the difference in electron density inside and outside the plasmapause, the chorus may be damped when propagating into the plasmasphere, and hiss waves in the plasmasphere can be reflected when they propagate near the plasmapause. Recently, A new banded structure of hiss has been reported with a lower band below ∼100 Hz and an upper band above ∼200 Hz. Using ∼7 years measurements of Van Allen Probes, we statistically investigate the distribution of banded hiss wave power with respect to the plasmapause location. The L, MLT, and geomagnetic activities are also considered. Our results suggest that banded hiss wave power shows a strong correlation with the location of plasmapause. Banded hiss waves closer to the plasmapause show larger powers. Plasmapause‐sorted banded hiss wave power can be used to better understand the generation and propagation mechanisms of banded hiss. Key Points The intensity distributions of banded hiss with plasmapause locations at different MLTs under various geomagnetic levels are investigated In statistics, the frequencies of two banded hiss waves decrease discernably with increasing L, but remain nearly constant with ΔL Banded hiss waves with larger amplitudes usually occur close to the plasmapause, implying both bands may be generated in the plume

Plasmaspheric plume hiss plays a crucial role in shaping Earth's electron radiation belts and influencing magnetosphere–ionosphere energy coupling. However, its generation mechanism remains contested between cyclic‐linear and localized‐nonlinear models. By analyzing over 64,000 high‐resolution plume hiss wave segments from the Van Allen Probes (1 January 2013–31 July 2019), we identify a distinct frequency dependence in their latitudinal distributions of directionality and amplitude. For high‐frequency hiss, bidirectional propagation is sharply confined near the magnetic equator, beyond which poleward‐propagating waves overwhelmingly dominate, and the wave amplitude increases obviously with latitude. These signatures are consistent with a rapid, single‐pass, equatorially confined, nonlinear amplification process. In contrast, low‐frequency hiss exhibits a high prevalence and wide latitudinal extension of bidirectional propagation, with relatively smooth amplitude variations. This pattern supports a generation scenario involving slower growth, potentially linear or nonlinear, that is coupled with wave bounce motion along magnetic field lines.