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The unique magnetic structure of the terrestrial aurora as a conduit of information between the ionosphere and magnetosphere can be utilized as a laboratory for physical processes at similar magnetic configurations and applied to various evolutionary phases of the solar (stellar) system. The most spectacular heliospheric abundance enhancement involves the 3He isotope and selective heavy elements in impulsive solar flares. In situ observations of electromagnetic waves on active aurora are extrapolated to flaring corona in an analysis of solar acceleration processes of 3He, the only element that may resonate strongly with the waves, as well as heavy ions with specific charge-to-mass ratios, which may resonate weaker via their higher gyroharmonics. These results are applied to two observed anomalous astrophysical abundances: (1) enhanced abundance of 3He and possibly 13C in the late stellar evolutionary stages of planetary nebulae; and (2) enhanced abundance of the observed fossil element 26Mg in meteorites as a decay product of radioactive 26Al isotope due to interaction with the flare-energized 3He in the early solar system.

The analogy between magnetohydrodynamics (MHD) and knot theory is utilized in presenting a new method for an analysis of stability and evolution of complex magnetic heliospheric flux tubes. Planar projection of a three-dimensional magnetic configuration depicts the structure as a two-dimensional diagram with crossings, to which one may assign mathematical operations leading to robust topological invariants. These invariants enrich the topological information of magnetic configurations beyond helicity. It is conjectured that the field which emerges from the solar photosphere is structured as one of the simplest knots—unknot or prime knot—and these flux ropes are then stretched while carried by the solar wind into the interplanetary medium. Preservation of invariants for small diffusivity and large cross section of the emerging magnetic flux makes them impervious to large scale reconnection, allowing us to predict the observed structures at 1 AU as elongated prime knots. Similar structures may be observed in magnetic clouds which got disconnected from their footpoints and in ion drop-out configurations from a compact flare source in solar impulsive solar events. Observation of small scale magnetic features consistent with prime knots may indicate spatial intermittency and non-Gaussian statistics in the turbulent cascade process. For flux tubes with higher resistivity, magnetic energy decay rate should decrease with increased knot complexity as the invariants are then harder to be violated. These observations could be confirmed if adjacent satellites happen to measure distinctly oriented magnetic fields with directionally varying suprathermal particle fluxes.

The existence of non-thermal electrons in the solar atmosphere and along the heliospheric field lines is deduced through emission of electromagnetic waves and via direct in situ measurements at 1 AU. The relation between the in situ electrons, their spectral shapes and the relative timing with respect to imaging and spectrographic observations are important in identifying potential acceleration sites and in understanding of the processes which control the formation of the delayed, (mildly) relativistic electrons which are observed in conjunction with flares or coronal mass ejections (CMEs). In contrast to previously suggested paradigms of acceleration of relativistic electrons around the CME shocks or at the flare site, it is suggested here that the delayed acceleration occurs along the stretched, closed coronal field lines, when an anisotropic seed population of low-energy electrons is injected in conjunction with the high frequency coronal radio bursts behind the large CME, as recorded by radioheliographs. The energization proceeds as a bootstrap process due to interaction with oblique whistler waves. The flare serves mainly as a time reference for the electromagnetic emissions, while the propagating CME subsequently opens an access for the relativistic electrons to the interplanetary medium.

Observations of energetic ions of solar origin in the heliosphere suggest the existence of two main energization sites with different physical mechanisms: (1) impulsive mechanism on the flaring coronal magnetic field – via resonant interaction, presumably with low-frequency electromagnetic waves; (2) gradual mechanism around the propagating, interplanetary shock – by interaction with quasi-static inhomogeneous electromagnetic structure and low-frequency Alfvenic turbulence. While the coronal process enhances a subset of rare elements, the interplanetary interaction energizes most of the elements of coronal/solar wind origin. In the impulsive events, according to recent models, a significant fraction of heavy elements which reside on the active flaring flux rope is energized; the resonant interaction operates mainly on Fe and other heavy elements with high charge states. In the gradual events main energization occurs close to the Sun at low Mach numbers; significant interplanetary enhancement of energetic ion fluxes requires a narrow scale length in the propagating shock. Coupling of both processes results in the final heliospheric distribution function of the heavy elements. The enhanced energetic heavy ion population may have a profound impact on human space exploration in the interplanetary space as well as in the resulting trapped radiation in the magnetosphere.

The variations in the fluxes of the relativistic electrons in the planetary radiation belts are due to a set of different physical processes which violate one or more of the adiabatic invariants. We survey the mechanisms which break down these invariants and investigate the time scales for the processes and the resulting effects on the observed fluxes. The mechanisms include (a) sudden deformation of the magnetic field configuration, (b) radial diffusion due to low-frequency electromagnetic oscillations, (c) transit-time damping due to fast waves and (d) diffusion due to electromagnetic ion-cyclotron (emic) or whistler waves. It is indicated how the waves which interact resonantly with the relativistic electrons are responsible for enhancement in the radiative spectra of the gyrosynchrotron emissions in the GHz frequency range and the X-ray bremsstrahlung emissions at the MeV energy range.

Simulation of the March 24, 1991 storm sudden commencement (SSC) has illuminated the rapid formation of new radiation belts on the particle drift time scale. While this event was the most dramatic in terms of radiation belt effects of the last solar maximum, comparable signatures of such events were seen in 1962 by Explorer 15 and in 1986 by DMSP. Several smaller MeV proton events with comparable particle morphology, but less radial transport and energization, were observed during the lifetime of the CRRES satellite (July 1990 – October 1991), which was well instrumented for both particle and field measurements inside geosynchronous orbit. Typically a solar proton event is accompanied by an SSC in the CRRES data set, while the converse is not always true. An SSC accompanied by solar protons produces a trapped population which remains on closed drift orbits until ring current buildup disrupts trapping, either by violation of the adiabatic trapping criterion or generation of waves whose frequency is comparable to periodic particle motion. Thus, new radiation belts formed around L = 4 by SSC injection are short-lived compared to the March 24, 1991 storm, wherein solar protons were transported radially inward to L = 2.5, with greater energization corresponding to first adiabatic invariant conservation than for the weaker events.

The spectacular enrichment of 3He and the smaller enrichments of heavy ions in impulsive flares is discussed in the context of a resonant interaction with the same electromagnetic ion cyclotron waves. The observed abundances are used to delineate the coronal thermodynamic conditions, the scalings of the enhancements with the coronal parameters and the frequency range of the resonant waves.

This paper investigates how the various waves of the whistler resonance cone compete for the free energy available in field-aligned fluxes of precipitating electrons in the auroral ionosphere. A two-dimensional numerical simulation code, based on the coupled pair of quasi-linear equations, is used for the investigation. The description provided by these equations allows us to follow the nonlinear development of the instability and analyze the interplay between the modes as mediated by the changing distribution function. We present results for a parameter regime corresponding to altitudes probed by sounding rockets, around 103 km and Ωe ≳ ωp. The presence of a halo of energetic electrons significantly affects the evolution of the turbulence. The spectrum is shown to shift with time toward increasingly oblique propagation angles including a substantial share of quasi perpendicular, short-wavelength modes close to the lower hybrid frequency.

MHD fields from a global three-dimensional simulation of the great March 24, 1991, storm sudden commencement (SSC) are used to follow the trajectories of particles in a guiding center test particle simulation of radiation belt formation during this event. Modeling of less intense events during the lifetime of the CRRES satellite, with similar morphology but less radial transport and energization, is also presented. In all cases analyzed, a solar proton event was followed by an SSC, leading to the formation of a new proton belt earthward of solar proton penetration. The effect on particle energization of varying solar wind and model pulse parameters is investigated. Both a seed population of solar protons and the SSC shock-induced compression of the magnetosphere are necessary conditions for the formation of a new proton belt. The outer boundary of the inner zone protons can be affected by an SSC and a newly formed belt can be affected by the ensuing or a subsequent storm, which may occur in rapid succession, as was the case in June and July 1991. The acceleration process is effective for both northward and southward IMF, with more energization and inward radial transport for the southward case for otherwise comparable solar wind parameters, because of the initially more compressed magnetopause in the southward case. The inner boundary and stability of the newly formed belt depends on the magnitude of radial transport at the time of formation and subsequent ring current perturbation of adiabatic trapping.

Kinetic localization of beam-driven Langmuir waves is studied for parameters relevant to the electron foreshock environment. Particle-in-cell simulations of the interaction occurring between energetic electrons and Langmuir waves are performed. It is shown that the nonlinearities in the resonant electrons lead to the formation of packets growing out of the noise. The characteristic spatial scale depends upon the beam velocity and has a weak dependence on the wave amplitude. The mechanism takes place within shorter timescales and for smaller amplitudes than the classic nonlinearities due to bulk electrons and ions. As an example, we apply the results to observations made in the Earth and Jovian foreshocks.

A substorm dispersionless injection event observed during the storm recovery phase on 11 March 1998 at geosynchronous orbit is carefully studied. The event shows the notable characteristics that for energetic ions the flux enhancement ratio before and after injection increases and remains elevated with increasing energy, while for energetic electrons it tends to decrease with increasing energy. In order to explain the unique injection feature, the authors propose a possible mechanism that velocity space diffusion in common to electric acceleration adjusts the particle injection state. Spectral characteristics of four different phases (pregrowth phase, the growth phase, the substorm expansion phase, and the recovery phase) have been investigated. The differential fluxes of electrons from 50 keV to 1.5 Mev and ions from 50 keV to 1.2 MeV measured by Synchronous Orbit Plasma Analyzer (SOPA) instrument onboard LANL satellite 1991-080 are found to be best fitted with the three-parameter kappa distribution function (f similar to A(0) . E[1 + E / (kappa E-0)](-kappa-1)) by Levenberg-Marquardt and Universal Global Optimization methods. The evolutions of the three parameters in the above kappa distribution in different substorm phases have been depicted for both electrons and ions. In each phase, E-0 and kappa show an approximately linear relationship kappa(E-0) = kappa(0) + eta E-0. This linear relationship can be obtained by solving the velocity space diffusion equation with an initial superthermal kappa distribution. Ion and electron are found to have opposite trend of parameters kappa(0) and eta in each phase, which indicates that the different species of particles exert different velocity space diffusion processes so that their flux enhancement ratios before and after injection are rather different. This implies that not only electric field acceleration, but also velocity space diffusion plays a very important role in the particle injection.

[1] Satellite observations near the X line are required to understand electromagnetic energy conversion and particle acceleration resulting from magnetic field reconnection. More than 900 orbits of Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft across the low-latitude dayside magnetopause, involving more than 4000 magnetopause crossings and 5000 h of data, were searched for examples of magnetic field reconnection within a few electron skin depths of the X line. Evidence that the X line was crossed in the best of these events comes from observations of DC electric and magnetic fields, electrostatic and electromagnetic lower hybrid waves, magnetosheath electrons flowing along the separatricies, and a super-Alfvenic electron jet flowing perpendicular to the magnetic field. A dispersion analysis identifies properties of the wave that are in agreement with the experiment. Neither these waves nor the DC electric field were sufficient to account for acceleration of the electron jet. The anomalous drag was not an important source of the observed DC electric field. The observed pressure gradient is a possible candidate for maintaining the electric field.

Large-amplitude electrostatic whistler waves near the lower hybrid frequency were observed by an auroral sounding rocket during substorm breakup. The measured wavelengths indicate that the emissions were electrostatic and resonant with electrons that had parallel energies of a few hundred electron volts. We propose that the intense emissions drew their energy from dispersive bursts of low-energy, field-aligned electron fluxes. The dispersive bursts are known to cause a brief, but intense instability that results in large-amplitude Langmuir emissions. The high-frequency emissions can rapidly form a plateau in the one-dimensional electron distribution. We show, however, that these distributions remain unstable to electrostatic whistler waves near the lower hybrid frequency. The amplitude and wavelength of the observed emissions were sufficient to accelerate the hydrogen ions with energies between about 50 eV and about 200 eV.

A test particle code is used here to investigate ring current ion interaction with Pc 5 waves, combined with convection and corotation electric fields, with emphasis on the loss of O(+) ions over the dayside magnetosphere. A new loss mechanism for the O(+) ions due to the combined effects of convection and corotation electric fields and interactions with Pc 5 waves via a magnetic drift-bound resonance is presented. For given fields, whether a particle gains or losses energy depends on its initial kinetic energy, pitch angle at the equatorial plane, and the position of its guiding center with respect to the azimuthal phase of the wave. The ring current O(+) ions show a dispersion in energies and L values with decreasing local time across the dayside, and a bulk shift to lower energies and higher L values. Due to interaction with the Pc 5 waves, the particle's kinetic energy can drop below that required to overcome the convection potential and the particle is lost to the dayside magnetopause by a sunward E x B drift.

The flyby missions of Voyagers 1 and 2 at Jupiter, Saturn and Uranus revealed intense waves above the electron gyrofrequency. Observation of waves at the upper hybrid frequency is often accompanied by power at adjacent electron Bernstein harmonics, and the relative power in these modes depends both on the density and temperature ratios of the cold background electron population and the hot magnetospheric electrons which drive the instability. A model of electron distributions which is consistent with observations is used for analysis of the excited waves, their dependence upon plasma parameters, and the time scales of the saturation processes. It is shown that in the presence of two-temperature electron distributions the linear excitation is due to a fluidlike coupling of two eigenmodes for perpendicular propagation and to kinetic destalization of oblique modes. The dependence of linear growth rates on propagation angle is presented, along with results from particle simulations. A quasi-linear diffusion time for relaxing the hot electron loss cone is calculated and compared with simulation results. This time scale is faster than for local saturation by heating the cold population, and also the convective amplification time scale, suggesting that the waves saturate at quasi-linear levels, while being convectively localized to the equatorial regions of the outer planetary magnetospheres.

[1] Ion beams streaming upward out of the ionosphere are frequently observed in the auroral acceleration cavity. They mainly consist of H + and O + ions drifting along the magnetic field lines and are believed to have been accelerated upward by the same parallel potential drop at the transition from the topside ionosphere. Due to the mass difference, H + and O+ form two distinct beams drifting at different speeds, whereby two-stream instabilities may develop. Here we present ID and 2D PIC simulations of the interaction between the If and O + beams in the cavity. Our model describes an open system, where a population of hot plasma sheet protons and hot electrons is at rest while H + and O+ are constantly injected at the boundary, emulating thus the ion influx from the bottom of the cavity. The study's results indicate two regimes according to the kinetic energy of the injected beams. For moderate energies the unstable waves are of the acoustic type and propagate parallel to the magnetic field. They can trap H + and O + ions, leading to phase-space vortices and the accompanying signatures of ion solitary waves in the electric field. For larger energies, the parallel acoustic waves are replaced by oblique cyclotron waves. The latter waves crisscross, forming a herringbone pattern that energizes the O + ions perpendicularly and leads to drifting conies. By contrast, the protons are hardly energized perpendicularly. The transition between the two regimes depends upon the electron temperature and the ion composition. In either case energy is transferred from the protons to the oxygens.

[1] Formation of inhomogeneous electromagnetic structures with gradients in magnetic field and intrinsic electric fields is commonly observed in magnetized plasmas. Heliospheric plasmas are susceptible to formation of localized, supersonically propagating electromagnetic inhomogeneities. Coronal relaxation may result in an emergence close to solar surface of a shock wave which traverses significant parts of the heliosphere. Shocks of solar origin may accelerate ions to high energies, and some of these ions can be trapped in quasi-stable orbits of planetary magnetospheres. The observationally deduced ion acceleration close to the Sun, at low Mach numbers and low turbulence levels, poses a dilemma regarding the energization mechanism. When the magnetic ramp of an obliquely propagating electromagnetic substructure narrows to a size of a fraction of ion skin depth, as conjectured during merging of successively propagating shocks, the trajectories of some ions exhibit strongly nonadiabatic characteristics. Subset of ions is energized while surfing along the shock due to the combined forces of magnetic fields and cross-shock electric potential gradient, forming a high-energy tail. This tail may be additionally accelerated after traversing the shock multiple times as a result of scattering and reflection due to Alfvenic wave diffusion. We follow the orbits of seed ions in a presence of a stationary, fluid-based, self-consistent model, and investigate their behavior for a variety of plasma parameters and geometries. The results indicate that (1) the energization of ions for low Mach numbers, as observed for emerging shocks close to the Sun, depends crucially on the narrowness of the electromagnetic structures, (2) the sufficiently narrow heliospheric structure can energize thermal protons and a subset of rare ions which were enriched due to impulsive coronal processes, (3) the energization is sensitive to the pitch angle of the seed population, indicating dependence on the geometry of the shock-plasma flow system, and (4) the preacceleration by surfing mechanism is a prerequisite for an additional energization due to diffusive shock acceleration. We conclude that the best configuration for an effective acceleration due to an emerging shock at small heliocentric distances and low Mach number consists of a narrow electromagnetic substructure which energizes heliospheric thermal protons directly from their thermal level, as well as trace elements which enrich the seed population due to previous coronal processes. The narrowness of the shock or its substructure and the surfing mechanism may help in explaining the observed energization when other mechanisms become inefficient due to an insufficient level of the turbulence. The energetic ion populations may have a direct profound impact on human space exploration.

[1] Measurements from the FAST spacecraft are used to show that ion solitary waves observed at the lower edge of the acceleration region travel at velocities faster than the associated auroral proton beams. The parallel phase velocity is consistent with the acoustic speed in the reference frame of the proton beam, strongly suggesting these waves are an ion acoustic mode. Their high phase velocity places them outside the ion beam population and rules out the ion two-stream instability as their source. These low-altitude structures may arise out of turbulence generated at the lower edge of the acceleration region. Their preferential observation at FAST altitudes may result from their high velocity combined with weak Landau damping that is restricted to the tenuous hot plasma sheet ions near the loss cone. Three different methods for estimating the velocity of these structures are examined. For the FAST antennae configuration it is found that signal delays between Langmuir probes operated in either current mode or voltage mode cannot provide valid estimates of the velocities. Instead, velocities are estimated by measuring the energy shift in the electron distribution within the negative potential well of the solitary wave. Using the measured wave potential and electric field, the scale size and velocity of the structures are calculated. Asymmetric solitary waves, sometime described as weak double layers, are also examined and shown to have no significant net potential. These new velocity estimates contrast sharply with reports based upon Viking observations and differ by about a factor of 2 from recent estimates deduced from Polar observations. These results are discussed in the context of previous estimates along with possible sources of error.

[1] FAST wave and particle observations on the nightside polar cap boundary indicate the operation of the ionospheric Alfven resonator (IAR). Large impulsive electric and magnetic field deviations on the boundary between the auroral oval and the polar cap close to magnetic midnight are correlated with accelerated electrons and excite semi periodic oscillations with a frequency of ∼0.5 Hz. Linear one-dimensional simulations of the Alfven resonator including parallel electric fields due to electron inertial effects, the ionospheric feedback instability and statistically determined altitude dependent density and composition profiles in a dipole geomagnetic field yield waveforms and electron energy spectra qualitatively similar to observations. However, from comparison with a case study example observed above a sunlit ionosphere, the observed electron energies (which exceed 10 keV) suggest that the observed wave carries a parallel electric field larger than possible from electron inertial effects in the linear approximation particularly if this acceleration occurs at altitudes within the ionospheric Alfven resonator.

[1] The stability of the electrostatic, fast, solitary structures that are observed frequently on auroral field lines is analyzed as a three-dimensional dynamic system and investigated numerically with the help of test-particle and particle-in-cell simulations. The recently observed large-amplitude, localized potential structures with a flat-top shape and separated electric field spikes parallel to the external magnetic field are shown to be supported by a particular self-consistent charge distribution function that differs qualitatively from the distribution that supports the previously investigated Gaussian potentials. The evolution of the solitary structures is related to changes in the trajectories of the supporting, trapped electrons. It is shown that ignoring the interaction with the ions, the planar, isolated spikes propagating into a plasma with realistic, open boundary conditions, are stable in three dimensions. The addition of a perturbation to the large-amplitude primary structure due to a smaller, faster secondary propagating spike results in destruction of the perturbing spike by modifying electron orbits of its trapped population, while the main spike gains an average momentum without any noticeable deformation. The analysis indicates robustness of the solitary spikes on the auroral field lines over significantly long times and their ability to propagate over long distances.

[1] Electron holes have been discovered in several key regions of the magnetosphere in the past few years. These small-scale structures seem to play an important role in the global dynamics of the magnetosphere, being most often associated with parallel electron beams and strong ion heating, as shown by the Fast Auroral Snapshot (FAST) spacecraft in the auroral region. Electrostatic whistler waves (EWW) in the VLF frequency range are often associated with these electron holes, suggesting that the generation of whistler waves is related to the holes. We present a model of the interaction between EWW and electron holes. Our analysis is based on the mechanical description of the energy exchange between particles and waves; by the use of the Hamiltonian formalism, action-angle variables, and canonical perturbation theory, we show that trapped electrons, owing to their periodic motion in the potential structure of the electron hole, enter into a resonance with the wave and can destabilize it at large parallel phase velocity relative to the electron thermal velocity. We derive the growth rate of EWW and compare our model with previous ones. Application to FAST observations shows that this linear instability is able to generate EWW with a normalized growth rate γ/ω varying from a few percents at low frequency (above the lower-hybrid frequency) up to ∼10% at higher frequency (below the electron plasma frequency).

[1] During a magnetic storm on 17–18 February 1998, several spacecraft sampled the inner magnetosphere over a wide range of L shells simultaneously and provided a unique opportunity to obtain particle spectra as a function of L shells, latitude, and local time. We present phase space modeling in a dipole magnetic field and with model electric fields during the recovery phase of that storm to explain the ion spectrograms obtained on three spacecraft (POLAR, EQUATOR-S, and FAST). The particle signatures studied are from the late recovery phase of the storm, but the particles are affected by the electric fields along their trajectories also during main phase. Our goal is to test and possibly improve global electric field models, which are crucial to the evolution of the storm-time particle distributions. We backtrace ion distributions from the satellite locations and keep track of charge exchange losses. We use the Volland-Stern, Weimer 96, Weimer 2000, and modifications of Weimer models to best fit instantaneous potential measurements made by the electric field instrument on POLAR and the ion drift meter instrument on the Defense Meteorological Satellite Program fleet of satellites. We incorporate corotation and a simple, global axisymmetric inductive electric field due to the ring current changes. Significant differences with ion spectral observations do exist and cannot be accounted for simply by modification of existing models. Explaining those differences requires addition of local inductive electric fields or nightside injections.

[1] The spatial properties of ionospheric ion outflows associated with perpendicular heating processes in the cusp are studied using a conjunction study from two satellites and ground radar systems. Low-energy outflowing ions are measured in a wide longitudinal range, between 13,000 and 19,000 km in altitude, over the dayside polar cap by the Hyperboloid experiment aboard the Interball Auroral Probe (AP). These observations are related to conjugate convection field measurements by the Saskatoon-Kapuskasing pair of the Super Dual Auroral Radar Network (SuperDARN). Data analysis suggests that outflowing ions originate from a wide magnetic local time range associated with both the dayside cusp region and the dayside cleft region. A direct cusp crossing by the Fast Auroral Snapshot (FAST) satellite at 2000-km altitude shows a correlation between transverse ion heating in a thin latitudinal region (∼1.3°) and the presence of broadband extremely low frequency (BBELF) turbulence, in addition to more intense electrostatic waves near and just above the lower hybrid (LH) frequency. This event is unusual because on the basis of the statistical survey of Freja and FAST data, most of the ion-heating events in the midaltitude auroral zone are correlated with enhanced emissions in the BBELF range. Furthermore, the electron population has energies that are too small to drive LH waves unstable. This event offers the opportunity to analyze the contribution of cusp magnetospheric ion injections to the heating of the ambient H+ and O+ ions. Kinetic instability calculations demonstrate that LH waves are destabilized by the ring distributions, which result from injections of high-energy magnetosheath ions. Calculations show that a preheating mechanism by BBELF turbulence near the ion gyrofrequencies is also required so that LH heating is able to occur. The altitude dependence of the LH perpendicular heating is then analyzed by modeling the transport of the injected magnetospheric ions along magnetic field lines. It is shown that LH heating acts as an additional process from ∼2000 up to 10,000 km in altitude. In addition, trajectory calculations show that the low-energy outflowing H+ and O+ ions observed along Interball AP orbit in the polar cap are heated inside the cusp at altitudes extending up to 15,000 km. These results are then assembled to construct a possible heating scenario inside the cusp for this data set. The contribution of the different energization mechanisms to the ion heating as a function of altitude is then discussed.

The bursts of Langmuir waves observed in the auroral ionosphere are interpreted as localized wave packets of tens to a hundred wavelengths along the geomagnetic field, which interact with streaming, energetic electrons. We investigate the interaction at a kinetic level and show by means of self-consistent, particle-in-cell simulations with open boundary conditions that the interaction itself can lead to wave localization. Ballistic perturbations of the distribution function and nonlinear orbit corrections combine to modulate the perturbed density that drives the waves. The resulting kinetic localization takes place within shorter timescales and for smaller wave amplitudes than the focusing via ponderomotive force.

Test particle calculations are used to compute the effects of gravity and ponderomotive acceleration by shear Alfven wave oscillations on the distribution function of O(+) ions along auroral field lines, assuming an ionospheric Maxwellian source of the ions at 2000 km altitude with approximately 0.5 eV of thermal energy in the parallel component of velocity. The electric field model corresponds to a standing wave oscillation with a frequency approximately 1 Hz in the azimuthal direction superimposed on the background dipole field, in which the wave amplitude is either increasing or decreasing in time. The electric field is taken to be primarily in the perpendicular direction. The time varying wave produces broad distributions with widths of 2 to 10 times the initial 0.5-eV thermal energy of the Maxwellian source, and the density and flux of upward going O(+) ions at one Earth radius are both enhanced in this model. The oxygen ion distribution functions at 1 R(sub E) altitude resulting from interaction with waves whose amplitudes are increasing in time have a more gradual lower energy cutoff than do the distribution functions resulting from decaying waves. The high-energy part of the distribution functions in growing waves reflects the temperature of the Maxwellian source, while the high-energy part of the distributions resulting from decaying waves steepens with time, independent of the source temperature.

The study examines the theoretical properties of linear ion cyclotron waves propagating in the magnetosphere at arbitrary angles to the background magnetic field. It is found that in some cases the linear wave growth of modes with oblique propagation can dominate that of the parallel propagating electromagnetic ion cyclotron (EMIC) wave. The growth rate of the loss-cone-driven mode depends strongly on the depth of the loss cone. A simple analytical theory which explains the scaling of the growth rate of the oblique mode with respect to various parameters is presented. The loss-cone-driven mode is an electromagnetic mode which is preferentially nearly linearly polarized. The wave field which results from the oblique mode in its perferentially nearly linearly polarized form are nearly perpendicular to B0 and are such that they may be difficult to distinguish from those of a linearly polarized parallel propgating EMIC wave.

Quasi-monochromatic waves at about the hydrogen cyclotron frequency were observed as the ISEE 1 satellite traversed auroral field lines at radial distances of about 2.5-4.5 R(E) near midnight on June 19, 1981. Waves and both lower and higher frequencies were observed at higher altitudes, and possible electrostatic helium cyclotron and oxygen cyclotron waves occurred at lower altitudes. Upflowing hydrogen and oxygen beams and field-aligned currents occurred simultaneously. The features of the waves are most consistent with the current-driven mode. In addition, numerical studies of the linear dispersion relation, using parameters based on the observations, show that both the parallel and oblique two-stream modes and the ion-beam-driven modes were stable while oblique current-driven modes were unstable. The O(+) and H(+) distributions provide evidence for interactions with local electrostatic ion cyclotron waves and for the H(+)-O(+) two-stream instability at altitudes below the satellite.

Excitation of electrostatic waves around and above the lower hybrid frequency at the inner edge of the ring current is investigated. The model consists of cold plasmaspheric ions; hot, dilute, inhomogeneous ring current ions; and cold charge neutralizing electrons. It is shown that in the presence of a sufficiently large density gradient the coupling of the lower hybrid with the drift cyclotron harmonic mode destabilizes the plasma. Unstable interactions also occur at higher cyclotron harmonics when the lower hybrid is replaced by an ion Bernstein mode. Additional power at frequencies above the lower hybrid frequency is attributed to the thermal enhancement by the hot ring current ions, which increases with their density gradient. Particle simulations are conducted, and comparison to AMPTE data is discussed.

Heating of heavy ions has been observed in the equatorial magnetosphere in GEOS 1 and 2 and ATS 6 data due to ion cyclotron waves generated by anisotropic hot ring current ions. A one-dimensional hybrid-Darwin code has been developed to study ion heating in the ring current. Here, a strong instability and heating of thermal ions is investigated in a plasma with a los cone distribution of hot ions. The linear growth rate calculation and particle simulations are conducted for cases with different loss cones and relative ion densities. The linear instability of the waves, the quasi-linear heating of cold ions and dependence on the thermal H(+)/He(+) density ratio are analyzed, as well as nonlinear parallel heating of thermal ions. Effects of thermal oxygen and hot oxygen are also studied.

Electron distribution functions (EDFs) with a peak oblique to the magnetic field, adjacent to but distinct from loss-cone features, have been observed by the DE 1, Viking, and S3-3 spacecraft in passes through the nightside auroral zone, polar cap, dayside cusp, and extended dayside auroral oval. Using particle simulations, two types of wave excitation and particle acceleration mechanisms which may contribute to producing these electron conic distributions are investigated. The first involves excitation of upper-hybrid waves by the electron loss cone, and the subsequent perpendicular heating of the background and thermal electrons. The second involves excitation of downward propagating parallel modes by an auroral electron beam which frequently accompanies the upflowing electron conics. These modes provide parallel acceleration, which modifies the GDF. Those electrons which are not lost to the atmosphere and mirror back up the magnetic field line give rise to enhancements in the GDF at the edge of the loss cone.

We describe the scientific motivation, basic principles, and feasibility of a relatively new measurement technique, radio tomography, and show how it can be used to investigate the Earth's magnetosphere. We demonstrate that a multisatellite radio tomography experiment can produce two-dimensional images of plasma density in the Earth's magnetosphere at sufficient spatial (1/2 RE) and temporal (∼10 s) resolution to address key problems of magnetospheric physics. The imaging technique incorporates well-established radio science methods and computed tomography. Several coplanar satellites are required in orbits that encompass the imaged area. We suggest that the large-scale images are more valuable when combined with in situ observations, supporting an unambiguous interpretation of the in situ data and an investigation of the interdependence of small- and large-scale plasma processes.

Time stationary solutions to the Vlasov-Poisson equations for ion holes and double layers are examined along with particle simulations that pertain to recent observations of small amplitude electric field structures on auroral field lines. Both the time stationary analysis and the simulations suggest that the observed double layers evolve from holes in ion phase space. Multiple small amplitude double layers, as seen in long simulation systems, are observed to propagate past the spacecraft and may account for the acceleration of plasma sheet electrons to produce inverted-V precipitation.

The linear instability and nonlinear saturation of electrostatic emission near the lower hybrid frequency is examined for model cold and warm ion ring distributions and auroral zone parameters. In the cold ring case, a single coherent mode near omega (LH) evolves, and saturates by ion trapping. In the warm ring case, a discrete spectrum of unstable modes separated by the ion gyrofrequency is generated near and above omega (LH). The latter instability saturates by quasilinear diffusion.

Excitation of waves by electron distributions consisting of hot, beam, and cold populations is investigated theoretically and with the help of particle simulations. The main modes excited include the upper hybrid oscillation for nearly perpendicular propagation; the whistler mode at oblique angles, which becomes the plasma two-stream oscillation for parallel propagation; and the electron acoustic mode for nearly parallel propagation. The whistler mode, excited by thermal fluctuation enhancement, has a broad range of wave numbers and quasi-linearly decreases the beam slope, while the electron acoustic mode, which is linearly unstable, has a narrow spread in phase velocities and traps the beam and the warm electrons forming a double humped distribution. Both modes contribute to forming a tail in the cold electron distribution. The resulting wave spectrum is discussed in the context of DE 1 observations.

Simulations of argon beam experiments flown on two sounding rocket flights (ARCS 1, 2) reveal two bands of electrostatic wave emissions, one at high frequencies around the upper hybrid mode, the other at low frequencies around the lower hybrid mode. The latter is significantly enhanced by the argon beam in the simulations, and the enhancement was clearly observed on ARCS 2. This enhancement at phase velocities greater than the beam velocity is suggested to be due to an increase in the thermal fluctuation level of the plasma when the argon beam is present. Inclusion of electron dynamics and oblique angles of wave propagation with respect to B allows investigation of electron heating. Electron tail heating is observed parallel to B for k-parallel/k-perpendicular proportional to the square root of m(e)/m(0), while background ions are heated perpendicular to B.

The ion two-stream instability develops between upflowing H(+) and O(+) in the auroral acceleration region, if the two species are accelerated to different velocities in a semistationary electrostatic potential. Parallel propagating modes are unstable only for small relative drifts, while oblique modes remain unstable at larger drifts and, consequently, higher altitudes. The effects of oblique modes on ion heating are investigated, and it is found that O(+) heats primarily by trapping in the direction of wave propagation during the early, coherent phase of wave growth in the temporal evolution problem. After undergoing trapping along the magnetic field direction, H(+) heats primarily by quasi-linear diffusion when the spectrum broadens nonlinearly. The parallel ion distributions evolve by formation of a high-energy (low-energy) tail on oxygen (hydrogen) along with bulk slowing of hydrogen, which results in more energetic oxygen than hydrogen. Total heating is greatest in the direction of wave propagation, and this effect is greater for hydrogen than for oxygen.

The ARCS 3 sounding rocket experiment used two argon guns oriented parallel and perpendicular to the geomagnetic field. The parameters of this experiment have been used in a series of particle simulations in order to interpret ion beam interaction with the multispecies ionospheric plasma. Along with the lower hybrid mode between the electron and the hydrogen gyrofrequencies, ion-ion hybrid modes between the hydrogen and helium gyrofrequencies and between the helium and oxygen gyrofrequencies are identified in the simulations. Besides these cold plasma modes, warm Bernstein modes of the respective ion species are identified. The parallel argon beam injections excite lower hybrid waves perpendicular to the magnetic field because of the finite thermal spread of the parallel beam. Perpendicular ion heating of background hydrogen, helium, and oxygen is comparable in the simulations. Comparisons are made with the wave and particle data from the ARCS 3 rocket experiment.

The Bergman and Lotko (1986) analysis of the linear stability of the H(+) - O(+) two-stream interactions for parallel propagating wave modes is extended to an analysis of the stability of wave modes that propagate at an angle to the terrestrial magnetic field. The analaysis provides an insight into the manner in which the oblique modes linearly couple and become unstable; the conditions under which the particular couplings are important; the qualitative behavior of the frequency, wave vector, and growth rate of the most unstable mode; and the changes to these introduced by finite ion temperatures. Consideration is also given to the relative importance of obliquely propagating and parallel propagating waves for the condition when the velocity difference between two ion beams is below the upper limit.

The stability of H(+) and H(++) ring distributions which have been observed downflowing into the cusp on the DE and S3-3 satellites is examined in the context of the feedback of those instabilities on plasma of ionospheric origin consisting of (H(+) and O(+). Lower hybrid waves are excited by the ring distributions in three distinct phases of wave-particle interaction: linear growth, trapping, and quasi-linear diffusion.The latter phase accounts for most particle heating. Including background O(+) and/or a He(++) ring introduces new modes not present in a pure H(+) plasma which play an important role in heating heavier ions. O(+) is heated significantly more by a He(++) ring than a H(+) ring of comparable energy density. It is suggested that lower hybrid waves generated by downflowing ion ring distributions play a role in energizing ion conics in the cusp.

An active experiment for the study of wave particle interaction in the presence of a perpendicular beam type distribution is considered. The experiment involves the injection of a beam perpendicular to the magnetic field. Beam parameters can then be varied while local plasma parameters and associated wave phenomena are measured. Such an experiment was conducted as part of the Porcupine project. The present investigation has the objective to explain theoretically and by means of plasma particle simulations, some of the wave observations obtained. In the experiment, a main rocket payload and four subpayloads were employed. The subpayloads were ejected radially in different directions at an altitude of 240 km. One of the spinning subpayloads contained a plasma gun which emitted a beam of 200 eV xenon ions toward the main payload. The data recorded on the main payload revealed the existence of electrostatic waves with peaks at hydrogen gyroharmonics. A series of computer simulations approximating the xenon experiment was performed. The interpretation of the data is discussed.