Multi‐Parameter Chorus and Plasmaspheric Hiss Wave Models
Homayon Aryan2020, Journal of Geophysical Research: Space Physics
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Abstract
This is a repository copy of Multi-parameter chorus and plasmaspheric hiss wave models.
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Plasmaspheric Hiss: Coherent and Intense
Journal of Geophysical Research: Space Physics, 2018
Intense~300-Hz to 1.0-kHz plasmaspheric hiss was studied using Polar plasma wave data. It is found that the waves are coherent in all local time sectors with the wave coherency occurring in approximately three-to five-wave cycle packets. The plasmaspheric hiss in the dawn and local noon time sector are found to be substorm (AE*) and storm (SYM-H*) dependent. The local noon sector is also solar wind pressure dependent. It is suggested that coherent chorus monochromatic subelements enter the plasmasphere (as previously suggested by ray tracing models) to explain these plasmaspheric hiss features. The presence of intense, coherent plasmaspheric hiss in the local dusk and local midnight time sectors is surprising and more difficult to explain. For the dusk sector waves, either local in situ plasmaspheric wave generation or propagation from the dayside plasmasphere is possible. There is little evidence to support substorm generation of the midnight sector plasmaspheric hiss found in this study. One possible explanation is propagation from the local noon sector. The combination of high wave intensity and coherency at all local times strengthens the suggestion that the electron slot is formed during substorm intervals instead of during geomagnetic quiet (by incoherent waves). Plasmaspheric hiss is found to propagate at all angles relative to the ambient magnetic field, θ kB. Circular, elliptical, and linear polarized plasmaspheric hiss have been detected. No obvious, strong relationship between the wave polarization and θ kB was found. This information of hiss properties should be useful in modeling wave-particle interactions within the plasmasphere. Plain Language Summary Plasmaspheric hiss is found to be coherent (at all local times). The coherency occurs in packets of~3 to 5 cycles. For the dawn and noon local time sectors, a scenario of substorm and solar wind pressure generation of outer zone chorus with further propagation into the plasmasphere is supported by the data analysis results. The predominant wave polarization of hiss is found to be elliptical, with some minor presence of circular and linear polarizations. This is in general agreement with theoretical expectations.The presence of intense, coherent plasmaspheric hiss strongly supports the new hypothesis that the electron slot is formed during substorms rather than geomagnetic quiet periods. The loss of relativistic E~1MeV electrons for the inner magnetosphere (L > 6) may be due to wave-particle interactions with coherent plasmaspheric hiss.
Observations of the relationship between frequency sweep rates of chorus wave packets and plasma density
Journal of Geophysical Research, 2010
Chorus emissions are generated by a nonlinear mechanism involving wave-particle interactions with energetic electrons. Discrete chorus wave packets are narrowband tones usually rising (sometimes falling) in frequency. We investigate frequency sweep rates of chorus wave packets measured by the Wideband data (WBD) instrument onboard the Cluster spacecraft. In particular, we study the relationship between the sweep rates and the plasma density measured by the WHISPER active sounder. We have observed increasing values of the sweep rate for decreasing plasma densities. We have compared our results with results of simulations of triggered emissions as well as with estimates based on the backward wave oscillator model for chorus emissions. We demonstrate a reasonable agreement of our experimental results with theoretical ones.
The relations between magnetospheric chorus and hiss inside and outside the plasmasphere boundary layer: Cluster observation
Journal of Geophysical Research, 2011
1] Magnetospheric whistler mode emissions (chorus and hiss) can play an important role in acceleration and loss of energetic electrons by wave-particle interaction. Here we present a first report of two events in the simultaneous observations of chorus and hiss by the Cluster constellation. During the event of 30 August 2001, one spacecraft observed chorus in the plasmasphere boundary layer (PBL), and three spacecraft observed hiss in the plasmasphere. In the event of 18 November 2002, one Cluster spacecraft observed hiss inside the plasmasphere, and the other three spacecraft observed chorus outside the plasmasphere. The correlation between chorus and hiss waves in both events are analyzed via intensity comparison and cross-correlation analysis. It is found that chorus and hiss waves have significant correlation in the first event but have no correlation in the second event. Furthermore, we perform a ray-tracing study to investigate the correlation by adopting two typical density models: the MTotal density model associated with the PBL structure and the global core density model. Simulation results demonstrate that chorus waves outside the plasmapause can propagate into the plasmasphere and possibly evolve into hiss waves under the MTotal density model, supporting the previous finding that the plasmaspheric hiss may originate from discrete chorus emission. However, chorus cannot travel into the plasmasphere under the global core density model. This paper presents a first result that chorus has more opportunity to propagate into the plasmasphere through the PBL than through the plasmapause. The results suggest that the gradual density variation of the PBL appears to favor the inward propagation of whistler mode waves. (2011), The relations between magnetospheric chorus and hiss inside and outside the plasmasphere boundary layer: Cluster observation,
Identifying the source region of plasmaspheric hiss
Geophysical Research Letters, 2015
The presence of the plasmaspheric hiss emission around the Earth has been known for more than 50 years, but its origin has remained unknown in terms of source location and mechanism. The hiss, made of whistler mode waves, exists for most of the time in the plasmasphere and is believed to control the radiation belt surrounding the Earth which makes its understanding very important. This paper presents direct observational evidence that the plasmaspheric hiss originates in the equatorial region of the plasmaspheric drainage plumes. It shows that the emissions propagate along the magnetic field lines and away from the equator in the plumes but toward the equator at lower L shells inside the plasmasphere. The observations also suggest that the hiss waves inside the plasmasphere are absorbed as they cross the equator.
Origins of plasmaspheric hiss
Journal of Geophysical Research, 2006
1] We analyze wave and particle data from the CRRES satellite to determine the variability of plasmaspheric hiss (0.1 < f < 2 kHz) with respect to substorm activity as measured by AE*, defined as the maximum value of the AE index in the previous 3 hours. The study is relevant to modeling the acceleration and loss of relativistic electrons during storms and understanding the origin of the waves. The plasmaspheric hiss amplitudes depend on spatial location and susbtorm activity, with the largest waves being observed during high levels of substorm activity. Our survey of the global distribution of hiss indicates a strong day-night asymmetry with two distinct latitudinal zones of peak wave activity primarily on the dayside. Equatorial hiss (jl m j < 15°) is strongest during active conditions (AE* > 500 nT), with an average amplitude of 40 ± 1 pT observed in the region 2 < L < 4 from 0600 to 2100 MLT. Midlatitude (jl m j > 15°) hiss is strongest during active conditions with an average amplitude of 47 ± 2 pT in the region 2 < L < 4 from 0800 to 1800 MLT but extending out beyond L = 6 from 1200 to 1500 MLT. Equatorial hiss at 600 Hz has minimum cyclotron resonant energies ranging from $20 keV at L = 6 to $1 MeV at L = 2, whereas midlatitude hiss at 600 Hz has minimum resonant energies ranging from $50 keV at L = 6 to $2 MeV at L = 2. The enhanced equatorial and midlatitude hiss emissions are associated with electron flux enhancements in the energy range of tens to hundreds of keV, suggesting that these electrons are the most likely source of plasmaspheric hiss. The enhanced levels of plasmaspheric hiss during substorm activity will lead to increased pitch-angle scattering of energetic electrons and may play an important role in relativistic electron dynamics during storms.
Oblique ion-acoustic shock waves in a magnetized, multi-species plasma
Journal of physics, 2017
Ion-Acoustic (IA) shock waves are studied in a magnetized, five component cometary plasma consisting of positively and negatively charged oxygen ions, kappa described hydrogen ions, hot solar electrons and slightly colder cometary electrons. The Korteweg-de Vries-Burgers (KdVB) equation is derived and the variation of the shock profile is studied. It is found that the obliqueness of shock wave propagation significantly varies the basic properties like amplitude and width of the shock.
Cluster observations of mid-latitude hiss near the plasmapause
Annales Geophysicae, 2004
In the vicinity of the plasmapause, around the geomagnetic equator, the four Cluster satellites often observe banded hiss-like electromagnetic emissions (BHE); below the electron gyrofrequency but above the lower hybrid resonance, from 2 kHz to 10 kHz. We show that below 4 kHz, these waves propagate in the whistler mode. Using the first year of scientific operations of WHISPER, STAFF and WBD wave experiments on Cluster, we have identified the following properties of the BHE waves: (i) their location is strongly correlated with the position of the plasmapause, (ii) no MLT dependence has been found, (iii) their spectral width is generally 1 to 2 kHz, and (iv) the central frequency of their emission band varies from 2 kHz to 10 kHz. All these features suggest that BHE are in fact mid-latitude hiss emissions (MLH). Moreover, the central frequency was found to be correlated with the K p index. This suggests either that these banded emissions are generated in a given f/f ce range, or that there is a K p dependent Doppler shift between the satellites and a possible moving source of the MLH.
A model for the bifurcations in plasma drift-waves
Physica D: Nonlinear Phenomena, 1997
Spatiotemporal data from a plasma drift-wave experiment are analyzed by the biorthogonal decomposition (BOD). A description of the route to turbulence is given in terms of modulated monochromatic traveling waves. A low-dimensional dynamical system decribing some of the features of the route to the weak turbulence observed is presented.
Ground-based observations atL∼ 6 of multi-band structures in VLF hiss
Geophysical Research Letters, 2007
We present ground-based observations of banded structures (BS) in auroral hiss. This BS hiss was detected at Porojärvi station in Northern Finland, mainly in the local evening from 19 to 23 MLT, during magnetically quiet periods; half of all the events observed corresponded to AE < 50 nT. The structures, which resemble those observed by low-altitude satellites, can be related to the cyclotron resonant interaction of VLF waves at frequencies near the lower-hybrid resonance with suprathermal protons in the upper ionosphere and magnetosphere. The maximum probability distribution of band spacing for the events observed at Porojärvi is reached in the frequency range 200-300 Hz, which corresponds to proton gyrofrequencies at L $ 6 at altitudes of 4000-3000 km. We found that the BS hiss was detected in the region of evening-side downward field-aligned currents and rather intense precipitation of ions with energies 1-30 keV, detected by DMSP spacecraft. We propose that the observed BS hiss can be formed not only due to absorption at the proton gyroharmonics, as is usually assumed for similar structures observed onboard satellites, but also due to generation by energetic protons with an anisotropic velocity distribution.
Hiss emissions during quiet and disturbed periods
Pramana, 2002
The characteristic features of VLF hiss emissions during quiet and disturbed conditions observed at ground stations and on-board satellites are summarized. The increased intensity of the hiss emissions during magnetic storm period is explained by considering the enhanced flux of energetic electrons during magnetic storm period. The generation and propagation mechanism of VLF hiss are also briefly discussed.
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Simultaneous observation of chorus and hiss near the plasmapause
Journal of Geophysical Research: Space Physics, 2012
On 4 August 2010 a moderate geomagnetic storm occurred with minimum Dst of À65 nT and maximum K p of 7À. Shortly after the onset of this storm, VLF chorus was observed at Marion Island (L = 2.6). Over time the spectral structure of the chorus transformed into a hiss band spanning the same frequency range. The observation of overlapping chorus and hiss suggests that Marion Island was close to the plasmapause at the time of this event, and provides ground-based observational confirmation of the generation mechanism of plasmaspheric hiss from chorus waves outside of the plasmasphere. Chorus observations at Marion Island were not common during this period of the solar cycle and so this event was investigated in detail. The geomagnetic conditions are discussed and geosynchronous particle data and broadband data from two other stations are presented. Empirical models are employed to predict the location of the plasmapause, and its location is inferred from a knee whistler recorded at Dunedin, New Zealand. These show that Marion Island is in the vicinity of the plasmapause during the event. The event is also compared to chorus observed at similar L after the Halloween storms of 2003. The rarity of the chorus observation is quantified using DEMETER VLF data. The DEMETER data, along with the various ground based VLF measurements, allows us to infer temporal and spatial variations in the chorus source region.
Generation of hiss beyond plasmapause by magnetosonic waves
Planetary and Space Science, 1977
waves near the harmonics of proton cyclotron frequency can become unstable in the presence of oxygen ions in the ring current. For cos 8 = 0 (6 being the angle between the wave vector and the geomagnetic field) the growth rates are peaked at some optimum value of the oxygen ion density, whereas for cos BZ 0 they are reduced with the increase of oxygen ion density. The presence of hot oxygen ions can generate instability near the harmonics of oxygen cyclotron frequency. The growth rates are enhanced with the increase of cosff. This mechanism can generate discrete spectrum of ELF hiss beyond the plasmapause.
Plasmaspheric hiss observations in the evening and afternoon quadrants
Journal of Geophysical Research, 1975
An instrument to detect the magnetic components of ELF signals propagating in the magnetosphere was carried on Explorer 45. Over 600 hours of observations in the inner magnetosphere near the equatorial plane have been examined. These observations were obtained in late 1971 and the first half of 1972 when the satellite apogee was in the evening and alternoon quadrants. The strongest rfiost persistent signals were plasmaspheric hiss from a few hundred to a few thousand hertz. Broad band signals of 25 m'y were common. Frequently, the hiss terminated abruptly during a satellite pass near and inside the boundary of the plasmasphere. Hiss boundaries were observed usually beyond L = 4 in quiet times, Kp = 0 to 1+, but were frequently beyond apogee near L = 5. During disturbed times, Kp > 4+, hiss boundaries remained near L = 5 from 1600 to 1900 LT but were below L = 4 from 2000 to 2400 LT. The magnetic index best correlated with the hiss boundary near midnight was Dst, the ring current index. The boundary location near midnight ranged from L = 2.5 for Dst =-160 • to L = 5.5 for Dst: 0. The peak intensity of hiss during an orbit occurred most frequently in the alternoon about I RE inside the hiss boundary. The most intense hiss was observed in the recovery phase of magnetic storms at the inner edge of the ring current. The source of the hiss appears to be the outer plasmasphere. Generation of hiss through cyclotron resonance with energetic electrons is the probable source for most of the hiss. Ring current protons, forming a peak in the proton flux between 10 and 100 keV, may be a source for some of the hiss.
A theoretical verification of intensity of plasmaspheric ELF hiss emissions: theory versus GEOS1 observations
1997
An attempt is made to con®rm the generation mechanism of plasmaspheric ELF hiss emissions observed aboard GEOS-1 satellite in the equatorial region both at small and large wave normal angles by calculating their magnetic ®eld intensities in terms of incoherent Cerenkov radiation mechanism and cyclotron resonance instability mechanism, using appropriate and suitable plasma parameters. The ELF intensities calculated by Cerenkov radiation mechanism, being 4 to 5 orders of magnitude lower than the observed intensities, rule out the possibility of their generation by this mechanism. On the other hand, the intensities calculated under electron cyclotron resonance instability mechanism are found to be large enough to account for both the observed intensity and propagation losses and hence to con®rm that plasmaspheric ELF hiss emissions observed aboard GEOS-1 satellite both at small and large wave normal angles were originally generated in the equatorial region by this mechanism just near the inner edge of the plasmapause. The dierence in the observed intensities of two types of the emissions has been attributed to the propagation eect rather than the generation efect.
Ducted propagation of chorus waves: Cluster observations
Annales Geophysicae, 2011
Ducted propagation of whistler waves in the terrestrial magnetosphere-ionosphere system was discussed and studied long before the first in-situ spacecraft measurements. While a number of implicit examples of the existence of ducted propagation have been found, direct observation of ducts has been hampered by the low sampling rates of measurements of the plasma density. The present paper is based on Cluster observations of chorus waves. The ability to use measurements of the spacecraft potential as a proxy for high time resolution electron density measurements is exploited to identify a number of cases when increased chorus wave power, observed within the radiation belts, is observed simultaneously with density enchantments. It is argued that the observation of ducted propagation of chorus implies modification of numerical models for plasma-wave interactions within the radiation belts.
Analytical and Theoretical Studies of Low Frequency Non-linear Waves in Multi-Component Plasmas
2006
It is certified that work contained in this dissertation is based on theoretical investigation carried out by Mushtaq Ahmad under my supervision. He has fulfilled all the requirements and is eligible to submit the associated thesis for the degree of Doctor of Philosophy in Physics.
Laboratory simulation of magnetospheric chorus wave generation
Plasma Physics and Controlled Fusion
Whistler mode chorus emissions with a characteristic frequency chirp are important magnetospheric waves, responsible for the acceleration of outer radiation belt electrons to relativistic energies and also for the scattering loss of these electrons into the atmosphere. A laboratory experiment (Van Compernolle et al 2015 Phys. Rev. Lett. 114 245002, An et al 2016 Geophys. Res. Lett.) in the large plasma device at UCLA was designed to closely mimic the scaled plasma parameters observed in the inner magnetosphere, and shed light on the excitation of discrete frequency whistler waves. It was observed that a rich variety of whistler wave emissions is excited by a gyrating electron beam. The properties of the whistler emissions depend strongly on plasma density, beam density and magnetic field profiles.
Timescales of electrons wave-particle interactions with chorus and hiss in the outer radiation belts
2020
Path-integrated gain of whistler-mode chorus in the magnetosphere by a kappa distribution
Plasma Physics and Controlled Fusion, 2011
The path-integrated gain of whistler-mode chorus is evaluated by the incorporation of a kappa distribution of energetic electrons and a realistic fieldaligned density model of background electrons. Variations of temperature anisotropy and number density of energetic electrons along the magnetic latitude are derived based on the conservation of the first adiabatic invariant. Numerical simulation shows that a lower-band chorus has a much higher pathintegrated gain than an upper-band chorus under the same conditions. During propagation towards higher latitudes, chorus waves grow to large amplitudes in the early stage but ultimately attenuate due to wave damping. The pathintegrated gain is higher with the initial wave vector pointing toward lower L shells than toward higher L shells. Moreover, the energetic electron population has a significant influence on the path-integrated gain, and the wave gain is larger as the temperature anisotropy or the density of energetic electrons is enhanced. This result provides further understanding of the chorus wave propagation characteristics in space plasmas.
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