Self-consistent model of magnetospheric ring current and propagating electromagnetic ion cyclotron waves: 2. Wave-induced ring current precipitation and thermal electron heating (original) (raw)
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Journal of Geophysical Research, 2009
Further development of our self-consistent model of interacting ring current (RC) ions and electromagnetic ion cyclotron (EMIC) waves is presented. This model incorporates large-scale magnetosphere-ionosphere coupling and treats self-consistently not only EMIC waves and RC ions, but also the magnetospheric electric field, RC, and plasmasphere. Initial simulations indicate that the region beyond geostationary orbit should be included in the simulation of the magnetosphere-ionosphere coupling. Additionally, a self-consistent description, based on first principles, of the ionospheric conductance is required. These initial simulations further show that in order to model the EMIC wave distribution and wave spectral properties accurately, the plasmasphere should also be simulated self-consistently, since its fine structure requires as much care as that of the RC. Finally, an effect of the finite time needed to reestablish a new potential pattern throughout the ionosphere and to communicate between the ionosphere and the equatorial magnetosphere cannot be ignored.
Journal of Atmospheric and Solar-Terrestrial Physics, 2015
Behaviors of the integrated wave gain of electromagnetic ion cyclotron (EMIC) waves in the H + -He + plasma of the inner magnetosphere is investigated. The integrated wave gain is obtained by integration of a temporal local growth rate along a geomagnetic field line. The local growth rate is determined by the method of generalized on the case of a bi-ion plasma. The concentration of the cold plasma is obtained on a basis of an empirical model of the plasmasphere and trough by . The energetic proton flux in the equatorial inner magnetosphere is set by the empirical model of , which refers to the conditions of low geomagnetic activity. The coefficients of EMIC wave reflection from the conjugated ionosphere are calculated using the International Reference Ionosphere (IRI) model. It is shown that the integrated wave gain of the EMIC waves increases with L -shell increasing and peaks around 14-20 MLT. In the afternoon sector the integrated wave gain reaches maximum in the cold plasma of higher density. Here the EMIC waves with the frequency below the equatorial He + gyrofrequency will be generated. The main findings of our study are in agreement with the basic experimental results on the EMIC wave occurrence in the equatorial middle magnetosphere known from satellite observations.
Journal of Geophysical Research, 2002
Initial results from a newly developed model of the interacting ring current ions and ion cyclotron waves are presented. The model is based on the system of two kinetic equations: one equation describes the ring current ion dynamics, and another equation describes wave evolution. The system gives a self-consistent description of the ring current ions and ion cyclotron waves in a quasilinear approach. These equations for the ion phase space distribution function and for the wave power spectral density were solved on aglobal magnetospheric scale undernonsteady state conditions during the 2-5 May 1998 storm. The structure and dynamics of the ring current proton precipitating flux regions and the ion cyclotron wave-active zones during extreme geomagnetic disturbances on 4 May 1998 are presented and discussed in detail.
Effect of Ring Current Ions on Electromagnetic Ion Cyclotron Wave Dispersion Relation
2006
RC ROLE IN EMIC WAVE DISPERSION RELATION 27 This "new" wave activity is well organized by outward edges of dense suprathermal ring 28 current spots, and the waves are not observed if the ring current ions are not included in 20 the real part of dispersion relation. Third, the most intense wave-induced ring current 30 precipitation is located in the night MLT sector and caused by modification of the wave 31 dispersion relation. The strongest precipitating fluxes of about 8 • 106 (cm 2-s •st)-1 32 are found near L=5.75, MLT=2 during the early recovery phase on 4 May. Finally, the 33 nightside precipitation is more intense than the dayside fluxes, even if there are less 34 intense waves, because the convection field moves ring current ions into the loss cone on 3s the nightside, but drives them out of the loss cone on the dayside. So convection and 3_ wave scattering reinforce each other in the nightside, but interfere in the dayside sector. 1997]. Subsequent transport of the dissipating wave energy into the ionosphere causes ionosphere temperature enhancements [e. g., Gurgiolo et al, 2005]. Cornwall et al. ss [197i I employed the mechanism of resonant energy transfer to electrons to explain stable auroral red arc emissions during the recovery phase of storms. Measurements taken aboard the Prognoz satellites revealed a "hot zone" near the plasmapause where $8 the temperature of coreplasmaionscanreachtensof thousands of degrees [Bezrukikh 69 and Gringauz, 1976; Gringauz, 1983; 1985]. The earliest results regarding the heating 6o of the cold ions were obtained by Galeev [1975] who considered the induced scattering 61 of EMIC waves by plasmaspheric protons as an ion heating mechanism. This nonlinear 62 wave-particle interaction process was used in a plasmasphere-RC interaction model by 63 Gorbachev et al. [1992]. Later, a detailed analysis of thermal ion heating by EMtC 64 waves was presented by Anderson and Fuselier [1994] and Fuselier and Anderson 65 [1996]. Relativistic electrons (> 1 MeV) in the outer radiation belt can also interact 66 with EMIC waves [Thorne and Kennel, 1971; Lyons and Thorne, 1972]. Recently, 67 data from balloon-borne X-ray instruments provided indirect but strong evidence for 68 EMtC wave-induced precipitation of outer-zone relativistic electrons [
Journal of Atmospheric and Solar-terrestrial Physics, 2001
It has generally been assumed in the past that the plasmapause is a preferred region for the generation and propagation of electromagnetic ion cyclotron (EMIC) waves in the Earth's magnetosphere. One assumption invoked the overlap of the expanding cold plasmapause with the inner edge of the hot ring current during storm recovery to provide favourable conditions for EMIC instability. The plasmapause was also expected to provide a convenient gradient for guiding the waves from equatorial sources to higher latitudes. The paper commences from a historic perspective and reviews the development of the ideas from the 1960s that relate the source of EMIC waves to the plasmapause. CRRES spacecraft observations of EMIC wave events over L = 3:5-8 and associated plasmapause locations indicate that the plasmapause is a region of wave generation and propagation, with signiÿcant wave power seen in the plasmatrough, but is not necessarily the preferred region. Other results show that wave occurrence predominates in the afternoon and increases with radial distance and a He + slot is seen in the data. These agree with earlier AMPTE-CCE results from Anderson et al. (J. Geophys. Res. 97 (1992) 3075, 3089). New results from CRRES show all wave polarisations (left-hand, linear, and right-hand) are seen within 8 • of the equator whereas linear predominates over 20-30 • latitude. Waves are observed in background plasma densities of 4-300 cm −3 . Wave frequencies above the He + cyclotron frequency are concentrated outside the plasmapause in lower density regions of 2-30 cm −3 .
Journal of Geophysical Research: Space Physics, 2013
1] Understanding excitation of electromagnetic ion cyclotron (EMIC) waves remains a considerable scientific challenge in the magnetospheric physics. Here we adopt correlated data from the Thermal Emission Imaging System (THEMIS) spacecraft under low (K p = 1 + ) and medium (K p = 4) geomagnetic activities to investigate the favorable conditions for the excitation of EMIC waves. We utilize a sum of bi-Maxwellian components and kappa components to fit the observed ion (6-25 keV) distributions collected by the electrostatic analyzer (ESA) onboard the THEMIS spacecraft. We show that the kappa distribution models better and more smoothly with the observations. Then we evaluate the local growth rate and path-integrated gain of EMIC waves by bi-Maxwellian and kappa distributions, respectively. We demonstrate that the path-integrated wave gain simulated from the kappa distribution is consistent with observations, with intensities 24 dB in H + band and 33 dB in He + band. However, bi-Maxwellian distribution tends to overestimate the wave growth rate and path-integrated gain, with intensities 49 dB in H + band and 48 dB in He + band. Moreover, compared to the He + band, a higher proton anisotropy is needed to excite the H + band waves. The current study presents a further observational support for the understanding of EMIC wave instability under different geomagnetic conditions and suggests that the kappa-type distributions representative of the power law spectra are probably ubiquitous in space plasmas.
Journal of Geophysical Research, 1984
Emissions that appear to have been electrostatic ion cyclotron (EIC) waves have been observed at low altitude in the diffuse aurora by a sounding rocket payload. The rocket was launched from Poker Flat, Alaska, at •2030 MLT. The flight successively traversed •70 km of the diffuse aurora, a dark region, and a quiet 40 kR auroral arc. In the diffuse aurora, peaks were observed in the power spectrum of the electric field at frequencies near the hydrogen and oxygen ion cyclotron frequencies. Doppler shift and polarization analyses have been performed using EIC wave spectrum parameters derived from linear theory. Both analyses indicated that these emissions had properties consistent with those VLF covering a frequency range from 2.5 Hz to 8 kHz. Emphasis in the analysis and discussion will be placed on emission features that had properties similar to those expected for electrostatic hydrogen and oxygen cyclotron waves [Bering, 1983b]. Electrostatic ion cyclotron (EIC) waves are considered to be one of the more important plasma wave modes present in and near auroral arcs. First discussed in detail by Drummond and Rosenblurb [1962], the EIC wave mode has the lowest threshold for instability among the various possible current driven instabilities to which auroral Birkeland currents might be subject [Kindel and Kennel, 1971]. Among other effects, expected for H + and O + EIC waves. Taken together, EIC waves have been suggested as the mechanism the two analyses indicated that both emission bands were due to waves propagating both up and down the field line and eastward parallel to the poleward boundary of the diffuse aurora. The large local cold plasma density and resulting large Landau damping require that the source be responsible for the selective perpendicular ion heating which produces "ion conics." Ion conic is the term used to describe ions flowing up into the magnetosphere with a minimum in their distribution function at 180 ø pitch angle and broad maximum between 90 ø and 130 ø pitch angle local. Free energy for the waves was apparently [Sharp et al., 1977, 197q; Ghielmetti et al., available in the 5 BA/m 2 downward parallel current 1978; Croley et al., 1978; Whalen et al., 1978; density which was inferred from the magnetometer data. The presence of the waves indicates that this current was being carried by less than 2% of the plasma, presumably in the form of a field aligned beam of electrons with energies of a few eV. Introduct ion This paper is the first in a series of three papers about an extensive set of electric field Klumpar,
Theory and observation of electromagnetic ion cyclotron triggered emissions in the magnetosphere
Journal of Geophysical Research, 2010
1] We develop a nonlinear wave growth theory of electromagnetic ion cyclotron (EMIC) triggered emissions observed in the inner magnetosphere. We first derive the basic wave equations from Maxwell's equations and the momentum equations for the electrons and ions. We then obtain equations that describe the nonlinear dynamics of resonant protons interacting with an EMIC wave. The frequency sweep rate of the wave plays an important role in forming the resonant current that controls the wave growth. Assuming an optimum condition for the maximum growth rate as an absolute instability at the magnetic equator and a self-sustaining growth condition for the wave propagating from the magnetic equator, we obtain a set of ordinary differential equations that describe the nonlinear evolution of a rising tone emission generated at the magnetic equator. Using the physical parameters inferred from the wave, particle, and magnetic field data measured by the Cluster spacecraft, we determine the dispersion relation for the EMIC waves. Integrating the differential equations numerically, we obtain a solution for the time variation of the amplitude and frequency of a rising tone emission at the equator. Assuming saturation of the wave amplitude, as is found in the observations, we find good agreement between the numerical solutions and the wave spectrum of the EMIC triggered emissions.
Journal of Geophysical Research: Space Physics, 2013
1] A cold electron heating event associated with electromagnetic ion cyclotron (EMIC) waves is observed and modeled. The observational data of particles and waves are collected by the Thermal Emission Imaging System spacecraft at magnetic local time 17.0-17.2. During this event, intense He + band EMIC waves with the peak frequency 0.25 Hz are excited, corresponding to the observed phase space density (PSD) of distinct anisotropic ions. Meanwhile, substantial enhancements in energy flux of cold (1-10 eV) electrons are observed in the same period. The energy flux of electrons below 10 eV is increased by several to tens of times. We use a sum of kappa distribution components to fit the observed ion PSD and then calculate the wave growth rate driven by the anisotropic hot protons. The calculated result is in good agreement with the in situ observation. Then, we investigate whether the excited EMIC waves can transfer energy to cold electrons by Landau resonant absorption and yield electron heating. Using the typical Maxwellian distribution for cold electrons, we evaluate the wave damping rates resulted from the cold electrons in gyroresonance with EMIC waves. The simulating results show that the strong wave growth region in the He + band induced by anisotropic ions corresponds to the strong wave damping region driven by cold electrons. Moreover, cold electrons can be heated efficiently at large wave normal angles. The current results provide a direct observational evidence for EMIC-driven cold electron heating-a potential mechanism responsible for stable auroral red arc.