Ion conics and counterstreaming electrons generated by lower hybridwaves in the Earth's magnetosphere

The exotic phenomenon of energetic ion-conic and counterstreaming electron formulation by lower hybrid waves along the discrete auroral field lines in the Earth's magnetosphere is considered. Mean particle calculations, plasma simulations, and analytical treatments of the acceleration processes are described. It is shown that, in the primary auroral electron-beam region, lower hybrid waves could be an efficient mechanism for the transverse heating of ions of ionospheric origin (H ⁺ and O⁺) as well as for the field-aligned heating of the ambient electrons leading to coincident counterstreaming electron distributions. For oxygen ions to be energized by such a wave-particle interaction process, however, some sort of preheating mechanism will be required     

Reformed Solitary Kinetic Alfven Waves due to Dissipations and Auroral Electron Acceleration

The physical nature of the auroral electron acceleration has been an outstanding problem in space physics for decades. Some recent observations from the auroral orbit satellites, FREJA and FAST, showed that large amplitude solitary kinetic Alfvén waves (SKAWs) are a common electromagnetic active phenomenon in the auroral magnetosphere. In a low-β (i.e., β/2<<m_e/m_i<<1) plasma, the drift velocity of electrons relative to ions within SKAWs is much larger than thermal velocities of both electrons and ions. This leads to instabilities and causes dissipations of SKAWs. In the present work, based on the analogy of classical particle motion in a potential well, it is shown that a shock-like structure can be formed from SKAWs if dissipation effects are included. The reformed SKAWs with a shock-like structure have a local density jump and a net field-aligned electric potential drop of order of m_ev_A²/e over a characteristic width of several λ_e. As a consequence, the reformed SKAWs can efficiently accelerate electrons field-aligned to the order of the local Alfvén velocity. In particular, we argue that this electron acceleration mechanism by reformed SKAWs can play an important role in the auroral electron acceleration problem. The result shows that not only the location of acceleration regions predicted by this model is well consistent with the observed auroral electron acceleration region of 1—2 R_E above the auroral ionosphere, but also the accelerated electrons from this region can obtain an energy of several keV and carry a field-aligned current of several μA/m² which are comparable to the observations of auroral electrons.     

Electrodynamics of solar wind-magnetosphere-ionosphere interactions

The authors present a coherent picture of fundamental physical processes in three basic elements of the SW-I (solar wind-magnetosphere-ionosphere) coupling system: (i) the field-aligned potential structure which leads to the formation of auroral arcs; (ii) the magnetosphere coupling which leads to the onset of magnetospheric substorms; and (iii) the solar wind-magnetosphere dynamo which supplies the power for driving various magnetospheric processes. The field-aligned potential structure on auroral lines is forced into existence by the loss-cone constriction effect when the upward field-aligned current density exceeds the loss-cone thermal flux limit. The substorm onset occurs when the ionosphere responds fully to the enhanced magnetospheric convection driven by the solar wind. The energy is transferred from the solar wind to the magnetosphere by a dynamo process primarily on open field lines     

Satellite observations of electric fields in the innermagnetosphere and their effects in the mid-to-low latitude ionosphere

During geomagnetic disturbances, momentum and energy are transferred in significant quantities from interplanetary space to the magnetosphere-ionosphere system through the mediation of charged particles and electric fields. The most dramatic manifestations occur in the plasma sheet and the conjugate auroral ionosphere. However, electric fields observed during magnetic storms also penetrate the inner magnetosphere that maps to subauroral latitudes in the ionosphere. For example, a sudden commencement shock wave initiating the March 1991 magnetic storm created a new radiation belt within minutes. Particle and field measurements by Combined Release and Radiation Effects Satellite (CRRES) near the equatorial plane of the magnetosphere and by Defense Meteorological Satellite Program (DMSP) satellites in the topside ionosphere during the magnetic storm of June 1991 indicate that penetration electric fields energized the stormtime ring current and rapidly transported plasma within subauroral ion drift (SAID) structures at midlatitudes and in upward drafting plasma bubbles at low latitudes. Through enhanced transport or chemical reactions, the SAIDs dug deep plasma troughs at topside altitudes. Equatorial plasma bubbles developed while the ring current was unable to shield the electric field from the innermost magnetosphere     

Displacement current and the generation of parallel electric fields

We show for the first time the dynamical relationship between the generation of magnetic field-aligned electric field (E||) and the temporal changes and spatial gradients of magnetic and velocity shears, and the plasma density in Earth's magnetosphere. We predict that the signatures of reconnection and auroral particle acceleration should have a correlation with low plasma density, and a localized voltage drop (V||) should often be associated with a localized magnetic stress concentration. Previous interpretations of the E|| generation are mostly based on the generalized Ohm's law, causing serious confusion in understanding the nature of reconnection and auroral acceleration.     

A new model for auroral breakup during substorms

A model for substorm breakup is developed, based on (1) the relaxation of stretched (closed) dipolar field lines, and (2) the formation of an incipient current wedge within a single arc structure. It is argued that the establishment of a coupled current structure within a single arc leads to a quasistable system, i.e. the prebreakup regime. Perturbation of the prebreakup structure leads to an instability criterion. It is found, consistent with observations, that the narrower auroral arcs at lower L shells undergo the most explosive poleward expansion. According to this model, the precise location at which breakup occurs depends on the O⁺ density in the plasma sheet, the level of magnetic activity (K_p), and the intensity of the substorm westward electrojet in the ionosphere. An enhancement of any of these features will cause breakup to occur at lower L shells. Comparison of the proposed model with the Heppner-Maynard polar-cap potential model indicates that breakup is restricted to the west of the Harang discontinuity, consistent with observations from the Viking satellite     

Laboratory experiment on kinetic Alfven waves in connection withphenomena in space plasmas

A laboratory experiment has been performed in connection with interesting phenomena in space plasmas such as geomagnetic pulsations in the magnetosphere or particle acceleration by the kinetic Alfven wave in field-aligned currents of the auroral circuit. Fast waves or MHD surface waves in a cylindrical finite-β plasma have been observed to be mode converted into kinetic Alfven waves at the Alfven resonance layer. The surface waves were excited using small loop antennas located at the edge of the inhomogeneous plasma to simulate those on the magnetosphere or plasmapause     

Electric field and field-aligned currents produced by asymmetric ring current

The formation of the problem concerning calculation of the electric field and field-aligned currents in the magnetosphere and ionosphere produced by asymmetric ring current is considered with the approach and equations developed by [1–3]. These equations were used previously for estimation of the electric field in the ionosphere and magnetosphere appearing in the process of spreading of energetic particles injected into the trapping zone of the magnetosphere as a result of nuclear explosion. According to this theory, energetic particles injected into a ring current produce an asymmetric divergent ring current, field-aligned currents, a global electric field and currents in the ionosphere. Space Research Center, Polish Academy of Sciences, Warsaw, Poland. Published from Izvestiya Vysshikh. Uchebnykh Zavedenii, Radiofizika, Vol. 41, No. 4, pp. 423–431, April, 1998.     

Effect of upward ion on field-aligned currents in the near-earth magnetotail

A 3-dimensional resistive MHD simulation was carried out to study the effect of the upward ions on the field-aligned currents (FACs) in the near-earth magnetotail. The simulation results show that the up-flow ions originating from the nightside auroral oval would drift into the center plasma sheet along the magnetic field lines in the plasma sheet boundary, and have an important effect on the field-aligned currents. The main conclusions include that: 1) the upward-ions mainly affect the field-aligned currents in the near-earth magnetotail (inside 15 Re); 2) the generated FACs in the near-earth region have two types, i.e., Region 1 FAC in the high-latitude and Region 2 FAC in the low-latitude; 3) FACs increase with the enhancement of the upward ion flux; 4) with the same flux of the upward ions, FACs enhance with the increase of the velocity of the up-flow ions; 5) the intensification of FACs is also closely related with the latitude of the upward ions, and the ions from the closed field line region generate larger FACs; 6) the generation of FACs is closely related with B _y created by the upward ions. Supported by the National Natural Science Foundation of China (Grant Nos. CNSF-40474058 and CNSF-40536030)     

Magnetospheric substorms and discrete arcs of the polar aurora

A brief review of the results of the research in physics of the Earth’s magnetosphere leading to a substantial modification of the previously developed approaches is presented. The main emphasis is placed on physics of magnetospheric substorms and the nature of auroral arcs. It is shown that the formation of powerful electron beams that produce multiple arcs can be associated with the penetration of cold electrons of an ionospheric origin into the region of field-aligned acceleration of hot magnetospheric electrons.     

Energy distributions of ions produced by electron-stimulated desorption

We have measured the initial kinetic energy distributions of ions produced by electron bombardment of various oxides and halides. The instrument used allows ions directly ejected from the sample surface to be distinguished from ions formed by electron impact in the gas phase. Singly and multiply charged positive ions of species present in the matrix as anions and cations were desorbed by high energy ( 11 keV) electron impact. Directly desorbed positive halogen ions show a narrow, low energy peak, consistent with conventional models of electron stimulated desorption (ESD). In addition, some of the cation species exhibited similar narrow energy spectra. Charge states up to +6 were observed for the halides; with the exception of F²⁺ and Cl²⁺, multiple charge states were due to electron impact ionization of desorbed neutrals. Charge states up to +4 were seen for silicon from electron-bombarded SiO₂; energy distributions of Si⁺, Si²⁺ and Si³⁺ showed that these species were desorbed directly from the surface. The energy distributions of O⁺ and O²⁺ ions ejected from SiO₂ are relatively wide, compared to the energy distribution of Si⁺ ions. In contrast, O⁺ ions ejected from TiO₂ have a much narrower energy distribution, like those observed for the halogen ions.     

Recent improvements in the numerical scheme of estimatingfield-aligned current systems from ground magnetometer records

The capability of ground-based magnetometer data of estimating field-aligned current system is discussed. Starting with some basic equations governing electrodynamic parameters in the ionosphere, the author describes both the advantages and limitations of the algorithms known as magnetogram-inversion techniques. It is pointed out that the proposed numerical scheme has been considerably improved so that simultaneous measurements of electric fields, conductivities, and field-aligned currents by satellites and radars can be incorporated in a consistent manner. One of the advantages of the magnetogram-inversion technique is that, since the technique deduces the global distribution of various electrodynamic quantities in the ionosphere with a time resolution of several minutes, it is possible to compare their spatial distributions with each other, especially for the auroral region. Results on important characteristics of auroral electrojets are presented     

Modeling of field-aligned currents produced by asymmetric ring current during strong magnetic storms

The modeling of field-aligned currents (FACs) produced by an asymmetric ring current is presented. Our first results of the modeling of FACs in the magnetosphere, which were based on the theory advanced in [1–5], were obtained in [6]. It was shown that FACs develop as spiral structures. Extending this work, we came to the conclusion that FACs, appearing in the magnetosphere and ionosphere as a result of ion or electron injections, generally develop as clockwise (ion injections) or anticlockwise (electron injections) spirals that are independent of the number and energy spectra or space distributions of injected particles. A sharp maximum of FACs or an FAC jet in such spirals can be present at middle latitudes. The value of currents in a midlatitudinal FAC jet during strong magnetic storms and substorms could be of the same order as experimentally observed in the polar region. The model presented describes the dependence of ion FACs as well as FAC jets in the magnetosphere and ionosphere, on the parameters of injected particles. Space Research Center, Polish Academy of Sciences, Warsaw, Poland. Published in Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 41, No. 5, pp. 551–566, May, 1998.     

Spatial-temporal ion structures in the earth’s magnetotail: Beamlets as a result of nonadiabatic impulse acceleration of the plasma

The properties of high-energy ion beams (beamlets) observed in the boundary layer of the plasma sheet of the Earth’s magnetotail during short time intervals (1–2 min) have been considered. Beamlets are induced by nonlinear impulse accelerating processes occurring in the current sheet of the far regions of the geomagnetic tail. Then, moving toward the Earth along the magnetic field lines, they are detected in the magnetotail (in the plasma sheet boundary layer) and in the high-latitude part of the auroral zone in the form of short bursts of high-energy ions (with energies of several tens of keVs). The size of the localization region of the beamlets in the magnetotail and auroral zone has been determined by the epoch-superposition method, and it has been shown that beamlets are concentrated in a narrow region near the plasma sheet boundary, whose latitude size is no more than 0.8δ. This conclusion corroborates the theoretical prediction that the nonadiabatic resonant acceleration of ions occurs in a spatially localized region near the separatrix separating the open magnetic field lines and closed field lines, which contain the hot and isotropic plasmas of the plasma sheet. Based on the CLUSTER multisatellite measurements, the spatial structure of beamlets is analyzed and it has been found that the Alfvén wave arises due to the excitation of fire-hose instability at the instant of the exit of the ion beam from the current sheet to the high-latitude region of the far tail of the Earth’s magnetosphere. The longitudinal (along the magnetic field) and transverse sizes of a beamlet are estimated. It has been found that the beamlet is a dynamic plasma structure whose longitudinal size is several hundred times larger than its transverse size.     

Transmission of low-energy (< 10 eV) O ions through Au films on TiO2(110)

In an attempt to identify the fundamental processes that influence ion transport through metallic surface layers, we have studied the transmission of O⁺ ions through discontinuous Au films adsorbed on TiO₂(110). A low energy (< 10 eV) O⁺ ion beam is generated via electron stimulated desorption when an Au-dosed TiO₂(110) substrate is bombarded with a focused 250 eV electron beam. Low energy ion scattering data indicate that Au evaporated under ultrahigh vacuum conditions at 300 K forms three-dimensional clusters on TiO₂(110). As the Au coverage increases, the formation of Au clusters on TiO₂(110) blocks a fraction of the TiO₂ surface and the O⁺ yield is attenuated. However, for high coverages (≥30% Au covered substrate) the O⁺ signal decreases at a faster rate than the TiO₂ open area fraction. We attribute the attenuation of the O⁺ yield for high Au coverages mainly to blocking of O⁺ by Au clusters, to deflection of trajectories by the image force between ions and Au clusters, and to charge transfer between desorbing O⁺ and neighboring Au clusters.     

Study of the electron damage of the MgO(100)-D2O system by ESD

An electron-stimulated desorption (ESD) study of electron damage of a D₂O layer adsorbed on the MgO(100) surface at room temperature is presented. After exposing the surface to D₂O, the surface spectrum shows the main ESD component to be D⁺ ions, with lower intensity signals corresponding to O⁺ and OD⁺ ions. When the surface is simultaneously exposed to heavy water and electron bombardment, there is a rapid initial increase of the D⁺ intensity accompanied by a decrease of the intensity of the O⁺ ions. Electron damage of the surface after exposing to D₂O produces a significant decrease of the D⁺ intensity, while the O⁺ and OD⁺ intensities decrease more slowly. Heavy water adsorption does not change the form of the ion kinetic energy distribution of the O⁺ ions with electron dose, except for a decrease in intensity. Electron damage increases the intensity of the ion kinetic energy distribution of D⁺ again without changing its shape. These experiments show that heavy water adsorption under electron bombardment does not induce any chemistry of the adsorbed species, but enhances the fragmentation rate of the OD species which, in turn, increases the yield of D⁺ ions. Values of total desorption cross-sections for the three ions species are reported.     

Structure of the magnetic field of the Jovian magnetosphere

We exactly solved the problem of the interaction between the rotating magnetic field of Jupiter and the equatorial plasma disk formed by the gases flowing from the Jovian satellite Io. The disk is shown to expel the Jovian magnetic field in both directions, inward, toward Jupiter, compressing its dipole magnetic field, and outward. Jupiter spins up the disk up to velocities that correspond to nearly constant angular rotation, but with an angular frequency lower than the angular frequency of Jupiter itself. The radial velocity of the plasma in the disk approaches its azimuthal velocity. We determined the power of Jupiter’s rotational energy losses. Part of this energy is transferred to the disk, and the other part goes into heating the Jovian ionosphere. We show that the Pedersen surface conductivity of the Jovian ionosphere must have a lower limit to maintain the electric current that arises in the disk-rotating magnetic field system. This current in the Jovian magnetosphere flows only along the preferential magnetic surfaces that connect the inner and outer edges of the disk to the ionosphere.     

Simulation of the electric field in Earth’s ionosphere during a geomagnetic storm

Previously, a global self-consistent model of the thermosphere, ionosphere, and protonosphere (GSM TIP) was used to study the ionospheric effects of geomagnetic storms in 2005, 2006, 2010, and 2011. In these studies, the input parameters of the model were specified using different dependences of variations of the potential difference across the polar caps and of the spatial distribution of Region 2 field-aligned currents during geomagnetic storms on the geomagnetic activity indices, solar wind parameters, and interplanetary magnetic field parameters. In the present work, we have tried to examine how correct was the choice of these relationships and how faithful are the obtained global distributions of the electric field in the ionosphere. For this, we present the results of a comparative analysis of the electric field in the ionosphere during geomagnetic storms of May 2–3, 2010, obtained using two models (GSM TIP and LC06) based on different approaches to solving this problem.     

Characteristics of Polar Wind Flows at Altitudes of about 20000 km

The problem of the outflow of ionospheric plasma into the magnetosphere is considered. In particular, the phenomenon of the polar wind observed in the polar cap is studied. The study of this phenomenon is complicated by the fact that the field-alined velocities of individual ions are small, and therefore, the electric field of the positively charged satellite prevents their measurement. This paper examines the measurements carried out on the Interball-2 satellite at altitudes of ~20000 km and compares them with the results of simulations within the framework of the GSM TIP model. It has been demonstrated the GSM TIP model well describes the outflow of H⁺ ions from the ionosphere to the magnetosphere in the polar cap.     

Influence of Ion Nonlinear Polarization Drift and Warm Ions on Solitary Kinetic Alfven Wave

Considering the effects of ion nonlinear polarization drift and warm ions, we adopt two-fluid model to investigate the character of low-frequency Solitary Kinetic Alfvén Wave (SKAW hereafter) in a magnetic plasma. The results derived in this paper indicate that dip SKAW and hump SKAW both exist in a wide range in magnetosphere (for the pressure parameter β～10^-5～0.01, where β is the ratio of thermal pressure to magnetic pressure, i.e. β=2μ₀nT/B₀²). These two kinds of SKAWs propagate at either Super-Alfvénic velocity or Sub-Alfvénic velocity. In the inertial region β＜＜m_e/m_i, the Sub-Alfvénic velocity dip SKAWs and hump SKAWs both exist; in the transmittal region β～ 2m_e/m_i, dip SKAWs and hump SKAWs propagate at Super-Alfvénic velocity or Sub-Alfvénic velocity; Super-Alfvénic velocity hump SKAWs and Super-Alfvénic and Sub-Alfvénic velocity dip SKAWs are in the kinetic region 1＞＞β＞＞ m_e/m_i. These results are different from previous ones. That indicates that the effects of ion nonlinear polarization drift and warm ions are important and they cannot be neglected. The SKAW has an electric field parallel to the ambient magnetic field, which makes the SKAW take an important role in the acceleration and energization of field-aligned charged particles in magnetic plasmas. And the SKAW is also important for the heating of a local plasma. So it makes a novel physical mechanism of energy transmission possible.