Finite geometry effect on the interaction of a hot beam with a plasma

International Nuclear Information System (INIS)

Shoucri, M.M.; Gagne, R.R.J.

1977-01-01

The effect of finite geometry on the interaction of a hot low-density beam with a uniform plasma filling a circular waveguide is studied. An expression is derived for the growth rate of the instabilities developing at the harmonic of the beam gyrofrequency, taking the finite beam gyroradius into account. The calculations are done in the quasistatic approximation. (author)

Cluster observations and simulations of He+ EMIC triggered emissions

Science.gov (United States)

Grison, B.; Shoji, M.; Santolik, O.; Omura, Y.

2012-12-01

EMIC triggered emissions have been reported in the inner magnetosphere at the edge of the plasmapause nightside [Pickett et al., 2010]. The generation mechanism proposed by Omura et al. [2010] is very similar to the one of the whistler chorus emissions and simulation results agree with observations and theory [Shoji et Omura, 2011]. The main characteristics of these emissions generated in the magnetic equatorial plane region are a frequency with time dispersion and a high level of coherence. The start frequency of previously mentioned observations is above half of the proton gyrofrequency. It means that the emissions are generated on the proton branch. On the He+ branch, generation of triggered emissions, in the same region, requests more energetic protons and the triggering process starts below the He+ gyrofrequency. It makes their identification in Cluster data rather difficult. Recent simulation results confirm the possibility of EMIC triggered emission on the He+ branch. In the present contribution we propose to compare a Cluster event to simulation results in order to investigate the possibility to identify observations to a He+ triggered emission. The impact of the observed waves on particle precipitation is also investigated.

Heliospheric MeV energization due to resonant interaction

International Nuclear Information System (INIS)

Roth, Ilan

2001-01-01

The prompt enhancement of relativistic electron flux during active geomagnetic periods, and the impulsive increase in the flux of the heliospheric energetic heavy ions during active solar periods are of major importance with respect to the proper operation of electronics on space-borne spacecraft and the safety of interplanetary human travel, respectively. Both enhancements may be caused by resonant wave-particle interaction with oblique electromagnetic waves on the terrestrial and coronal field lines. Whistler waves, which are enhanced significantly during substorms and which propagate obliquely to the magnetic field, can interact with energetic electrons through Landau, cyclotron, and higher harmonic resonant interactions when the Doppler-shifted wave frequency equals any (positive or negative) integer multiple of the local relativistic gyrofrequency. This interaction occurs over a broad spatial region when a relativistic electron is bouncing in the terrestrial magnetic field. Coronal ions interact selectively with electromagnetic ion-cyclotron (emic) waves which are correlated with impulsive flares. This interaction occurs over a small spatial region when the Doppler-shifted frequency matches the first or higher harmonic of the ion gyrofrequency. Recent new observations of terrestrial MeV X-rays are interpreted as a resonant loss of the radiation belt electrons

Quasi-linear equation for magnetoplasma oscillations in the weakly relativistic approximation

International Nuclear Information System (INIS)

Rizzato, F.B.

1985-01-01

Some limitations which are present in the dynamical equations for collisionless plasmas are discussed. Some elementary corrections to the linear theories are obtained in a heuristic form, which directly lead to the so-called quasi-linear theories in its non-relativistic and relativistic forms. The effect of the relativistic variation of the gyrofrequency on the diffusion coefficient is examined in a typically perturbative approximation. (author)

Overview of Emic Triggered Chorus Emissions in Cluster Data

Science.gov (United States)

Grison, B.; Pickett, J. S.; Omura, Y.; Santolik, O.; Engebretson, M. J.; Dandouras, I. S.; Masson, A.; Decreau, P. M.; Adrian, M. L.; Cornilleau Wehrlin, N.

2010-12-01

Electromagnetic ion cyclotron (EMIC) triggered emissions have been recently observed onboard the Cluster spacecraft close to the plasmapause in the equatorial region of the magnetosphere (Pickett et al., 2010). The nonlinear mechanism of the wave amplification is the same as for the well known whistler-mode chorus emissions (Omura et al., 2010). The EMIC triggered emissions appear as risers: electromagnetic structures that have a positive frequency drift with time. They can thus be considered as the EMIC analogue of rising frequency whistler-mode chorus emissions. In addition, they propagate away from the magnetic equator. These EMIC risers are not common in Cluster data. We present an overview of the properties of all the identified cases. Risers can be sorted out in two groups: in the first one the starting frequency of EMIC emissions is close to one half of the local proton gyrofrequency and the risers have a clear left-hand polarization. In the second group the risers have an opposite polarization with a starting frequency close to one half of the He+ gyrofrequency. Most of the cases have been detected close to 22 MLT (magnetic local time). This dependence will be investigated to determine if it is linked to the orbit effects or if there is a physical cause.

Coefficients of viscosity for heavy impurity element in tokamak

Energy Technology Data Exchange (ETDEWEB)

El-Sharif, R N; Bekhit, A M [Plasma Physics dept., NRC, Atomic energy Authority, Cairo, (Egypt)

1997-12-31

The transport of heavy impurity element in to tokamak was studied theoretically. The viscosity coefficients of chromium impurities has been calculated in 13 and 21 moment approximation, in the limit of strong fields where is the gyrofrequency of species it was found that the off diagonal coefficient approximately tends to zero. This means that the friction force in the off-diagonal direction is very small, for the perpendicular viscosity coefficient the two approximation coincide to each other. 3 figs.

On low-frequency whistler propagation in ionosphere

International Nuclear Information System (INIS)

Mazur, V.A.

1988-01-01

The propagation along the Earth surface of an electromagnetic wave with frequency below the ion gyrofrequency is theoretically investigated. In Hall layer of the ionosphere this wave is the whistler mode. It is shown that - contrary to previous works - Ohmic dissipation makes impossible the long-distance propagation of low-frequency whistlers. A many-layer model of the medium is used. The geomagnetic field is considered inclined. The eigen modes and evolution of the initial perturbation are considered

Faraday rotation in an electron-positron plasma containing a fraction of ions

International Nuclear Information System (INIS)

Hall, J.O.; Shukla, P.K.

2005-01-01

The Faraday rotation in a magnetized electron-positron plasma containing a fraction of ions is investigated by using a multifluid description. It is shown that the Faraday rotation for circularly polarized electromagnetic waves with frequencies much larger than the electron/positron plasma and electron gyrofrequencies is proportional to the ion number density and the magnitude of the ambient magnetic-field strength. The results are relevant for astrophysical observations and diagnostics of laboratory electron-positron-ion magnetoplasmas

Generation of auroral kilometric and Z mode radiation by the cyclotron maser mechanism

Science.gov (United States)

Omidi, N.; Gurnett, D. A.; Wu, C. S.

1984-01-01

The relativistic Doppler-shifted cyclotron resonance condition for EM wave interactions with a plasma defines an ellipse in velocity space when the product of the index of refraction and cosine of the wave normal angle is less than or equal to unity, and defines a partial ellipse when the product is greater than unity. It is also noted that waves with frequencies greater than the gyrofrequency can only resonate with particles moving in the same direction along the magnetic field, while waves with lower frequencies than these resonate with particles moving in both directions along the magnetic field. It is found, in the case of auroral kilometric radiation, that both the upgoing and the downgoing electrons are unstable and can give rise to this radiation's growth. The magnitudes of the growth rates for both the upgoing and downgoing auroral kilometric radiation are comparable, and indicate that the path lengths needed to account for the observed intensities of this radiation are of the order of a few hundred km, which is probably too large. Growth rate calculations for the Z mode radiation show that, for wave frequencies just below the gyrofrequency and wave normal angles at or near 90 deg, the electron distribution is unstable and the growth rates are large enough to account for the observed intensities.

Fast wave current drive above the slow wave density limit

International Nuclear Information System (INIS)

McWilliams, R.; Sheehan, D.P.; Wolf, N.S.; Edrich, D.

1989-01-01

Fast wave and slow wave current drive near the mean gyrofrequency were compared in the Irvine Torus using distinct phased array antennae of similar principal wavelengths, frequencies, and input powers. The slow wave current drive density limit was measured for 50ω ci ≤ω≤500ω ci and found to agree with trends in tokamaks. Fast wave current drive was observed at densities up to the operating limit of the torus, demonstrably above the slow wave density limit

Electron cyclotron heating of a tokamak reactor at down-shifted frequencies

International Nuclear Information System (INIS)

Fidone, I.; Giruzzi, G.; Mazzucato, E.

1985-01-01

The absorption of electron cyclotron waves in a hot and dense tokamak plasma is investigated for the case of the extraordinary mode for outside launching. It is shown that, for electron temperatures T/sub e/ greater than or equal to 5 keV, strong absorption occurs for oblique propagation at frequencies significantly below the electron gyrofrequency at the plasma center. A new density dependence of the wave absorption is found which is more favorable for plasma heating than the familiar n/sub e/ -1 scaling

A statistical study of ion energization at 1700 km in the auroral region

Directory of Open Access Journals (Sweden)

M. Hamrin

2002-12-01

Full Text Available We present a comprehensive overview of several potentially relevant causes for the oxygen energization in the auroral region. Data from the Freja satellite near 1700 km altitude are used for an unconditional statistical investigation. The data are obtained in the Northern Hemisphere during 21 months in the declining phase of the solar cycle. The importance of various wave types for the ion energization is statistically studied. We also investigate the correlation of ion heating with precipitating protons, accelerated auroral electrons, suprathermal electron bursts, the electron density variations, Kp index and solar illumination of the nearest conjugate ionosphere. We find that sufficiently strong broad-band ELF waves, electromagnetic ion cyclotron waves, and waves around the lower hybrid frequency are foremost associated with the ion heating. However, magnetosonic waves, with a sharp, lower frequency cutoff just below the proton gyrofrequency, are not found to contribute to the ion heating. In the absence of the first three wave emissions, transversely energized ions are rare. These wave types are approximately equally efficient in heating the ions, but we find that the main source for the heating is broadband ELF waves, since they are most common in the auroral region. We have also observed that the conditions for ion heating are more favourable for smaller ratios of the spectral densities SE /SB of the broadband ELF waves at the oxygen gyrofrequency.Key words. Ionosphere (auroral ionosphere; wave propogation Magnetospheric physics (electric fields

Electronic radiation of a plasma in a magnetic field

International Nuclear Information System (INIS)

Canobbio, E.; Consoli, T.; Ichtchenko, G.; Parlance, F.

1965-01-01

The influence on the microwave spectrum of the number of fast electrons, density, pressure and plasma inhomogeneities, has been studied in a hot cathode reflex discharge, operating either in a steady state either in a pulsed regime. Under some conditions a strong emission is observed between the harmonics of the electron gyrofrequency. A theoretical interpretation of the results is advanced by extending a model already proposed by CANOBBIO and CROCI. In particular it is indicated that the transition radiation can be responsible for the emission observed between the harmonics. (authors) [fr

Plasma wave observations during electron and ion gun experiments

International Nuclear Information System (INIS)

Olsen, R.C.; Lowery, D.R.; Weddle, L.E.

1988-01-01

Plasma wave instruments with high temporal and frequency resolution in the 0-6 kHz frequency range have been used to monitor electron gun-employing charge control experiments with the USAF/NASA p78-2 satellite, in order to determine whether plasma wave signatures consistent with the previous inference of electron heating were present. Strong plasma waves were noted near the electron gyrofrequency; these waves can heat ambient low energy electrons, as previously inferred. Attention is given to the two distinct classes of behavior revealed by the ion gun experiments. 16 references

Gyrofluid potential vorticity equation and turbulent equipartion states

DEFF Research Database (Denmark)

Madsen, Jens; Juul Rasmussen, Jens; Naulin, Volker

2015-01-01

. The equation is relevant for transport barriers in magnetically confined plasmas because particle density, ion temperature and the radial electric field are mutually coupled through the potential vorticity. The potential vorticity equation is derived from an energy conserving, four-field, electrostatic, full......An equation governing potential vorticity in a magnetized plasmas is derived. The equation is analogous to Ertel's theorem. In the long wave-length limit the potential vorticity equals the ratio of the gyro-frequency plus the E × B- and diamagnetic polarization densities to the particle density...

Simulation model for studying low frequency microinstabilities

International Nuclear Information System (INIS)

Lee, W.W.; Okuda, H.

1976-03-01

A 2 1 / 2 dimensional, electrostatic particle code in a slab geometry has been developed to study low frequency oscillations such as drift wave and trapped particle instabilities in a nonuniform bounded plasma. A drift approximation for the electron transverse motion is made which eliminates the high frequency oscillations at the electron gyrofrequency and its multiples. It is, therefore, possible to study the nonlinear effects such as the anomalous transport of plasmas within a reasonable computing time using a real mass ratio. Several examples are given to check the validity and usefulness of the model

Radiation condensation instability of compressional electromagnetic modes in magnetoplasmas containing charged dust impurities

International Nuclear Information System (INIS)

Shukla, P K; Eliasson, B; Kopp, A

2006-01-01

We report on an investigation into the radiation condensation (RC) instability of low-frequency (in comparison with the electron gyrofrequency) compressional electromagnetic waves in a magnetized plasma containing charged dust impurities. By using a two-fluid model, supplemented by the Faraday and Ampere laws, we derive a new dispersion relation. The latter is numerically analysed to examine the role of charged dust grains on the growth rate of the RC instability. The relevance of our investigation to density condensation in the next generation tokamak edges and on solar prominences is discussed

Jovian decametric radiation seen from Juno, Cassini, STEREO A, WIND, and Earth-based radio observatories

Science.gov (United States)

Imai, M.; Kurth, W. S.; Hospodarsky, G. B.; Bolton, S. J.; Connerney, J. E. P.; Levin, S. M.; Lecacheux, A.; Lamy, L.; Zarka, P.; Clarke, T. E.; Higgins, C. A.

2017-09-01

Jupiter's decametric (DAM) radiation is generated very close to the local gyrofrequency by the electron cyclotron maser instability (CMI). The first two-point common detections of Jovian DAM radiation were made using the Voyager spacecraft and ground-based radio observatories in early 1979, but, due to geometrical constraints and limited flyby duration, a full understanding of the latitudinal beaming of Jovian DAM radiation remains elusive. The stereoscopic DAM radiation viewed from Juno, Cassini, STEREO A, WIND, and Earth-based radio observatories provides a unique opportunity to analyze the CMI emission mechanism and beaming properties.

The role of magnetic field fluctuations in nonadiabatic acceleration of ions during dipolarization

Science.gov (United States)

Ono, Y.; Nosé, M.; Christon, S. P.; Lui, A. T. Y.

2009-05-01

We statistically examine changes in the composition of two different ion species, proton and oxygen ions, in the near-Earth plasma sheet (X = -16 R E ˜ -6 R E ) during substorm-associated dipolarization. We use 10 years of energetic (9-212 keV/e) ion data obtained by the suprathermal ion composition spectrometer (STICS) sensor of the energetic particles and ion composition (EPIC) instrument on board the Geotail spacecraft. The results are as follows: (1) Although the percentage increase in the energy density of O+ ions before and after a dipolarization exceeds that of H+ ions in the low-energy range (9-36 keV/e), this property is not evident in the high-energy range (56-212 keV/e); (2) the energy spectrum of H+ and that of O+ become harder after dipolarization in almost all events; and (3) in some events the energy spectrum of O+ becomes harder than that of H+ as reported by previous studies, and, importantly, in other events, the spectrum of H+ becomes harder than that of O+. In order to investigate what mechanism causes these observational results, we focus on magnetic field fluctuations during dipolarization. It is found that the increase of the spectrum slope is positively correlated with the power of waves whose frequencies are close to the gyrofrequency of H+ or O+, respectively (the correlation coefficient is 0.48 for H+ and 0.68 for O+). In conclusion, ions are nonadiabatically accelerated by the electric field induced by the magnetic field fluctuations whose frequencies are close to their gyrofrequencies.

Observation of a new type of low-frequency waves at comet 67P/Churyumov-Gerasimenko

Directory of Open Access Journals (Sweden)

I. Richter

2015-08-01

Full Text Available We report on magnetic field measurements made in the innermost coma of 67P/Churyumov-Gerasimenko in its low-activity state. Quasi-coherent, large-amplitude (δ B/B ~ 1, compressional magnetic field oscillations at ~ 40 mHz dominate the immediate plasma environment of the nucleus. This differs from previously studied cometary interaction regions where waves at the cometary ion gyro-frequencies are the main feature. Thus classical pickup-ion-driven instabilities are unable to explain the observations. We propose a cross-field current instability associated with newborn cometary ion currents as a possible source mechanism.

Equatorial noise emissions with a quasiperiodic modulation observed by DEMETER at harmonics of the O+ ion gyrofrequency

Czech Academy of Sciences Publication Activity Database

Parrot, M.; Nĕmec, F.; Santolík, Ondřej; Cornilleau-Wehrlin, N.

2016-01-01

Roč. 121, č. 10 (2016), s. 10289-10302 ISSN 2169-9380 R&D Projects: GA MŠk(CZ) LH15304; GA ČR(CZ) GA14-31899S Grant - others:AV ČR(CZ) AP1401 Program:Akademická prémie - Praemium Academiae Institutional support: RVO:68378289 Keywords : Van Allen Probes * magnetosonic waves * spatiotemporal variability * conjugate observations * cluster spacecraft * staff experiment * propagation * proton * plasmasphere * frequency Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 2.733, year: 2016 http://onlinelibrary.wiley.com/doi/10.1002/2016JA022989/abstract

Nonlinear radiation generation processes in the auroral acceleration region

Directory of Open Access Journals (Sweden)

R. Pottelette

2017-11-01

Full Text Available It is known from laboratory plasma experiments that double layers (DLs radiate in the electromagnetic spectrum; but this is only known qualitatively. In these experiments, it was shown that the electron beam created on the high-potential side of a DL generates nonlinear structures which couple to electromagnetic waves and act as a sender antenna. In the Earth auroral region, observations performed by auroral spacecraft have shown that DLs occur naturally in the source region of intense radio emissions called auroral kilometric radiation (AKR. Very high time-, spatial-, and temporal-resolution measurements are needed in order to characterize waves and particle distributions in the vicinity of DLs, which are moving transient structures. We report observations from the FAST satellite of a localized large-amplitude parallel electric field (∼ 300 mV m−1 recorded at the edges of the auroral density cavity. In agreement with laboratory experiments, on the high-potential side of the DL, elementary radiation events are detected. They occur substantially above the local electron gyrofrequency and are associated with the presence of electron holes. The velocity of these nonlinear structures can be derived from the measurement of the Doppler-shifted AKR frequency spectrum above the electron gyrofrequency. The generated electron holes appear as the nonlinear evolution of electrostatic waves generated by the electron–electron two-stream instability because they propagate at about half the beam velocity. It is pointed out that, in the vicinity of a DL, the shape of the electron distribution gives rise to a significant power recorded in the left-hand polarized ordinary (LO mode.

Closure of multi-fluid and kinetic equations for cyclotron-resonant interactions of solar wind ions with Alfvén waves

Directory of Open Access Journals (Sweden)

E. Marsch

1998-01-01

Full Text Available Based on quasilinear theory, a closure scheme for anisotropic multi-component fluid equations is developed for the wave-particle interactions of ions with electromagnetic Alfvén and ion-cyclotron waves propagating along the mean magnetic field. Acceleration and heating rates are calculated. They may be used in the multi-fluid momentum and energy equations as anomalous transport terms. The corresponding evolution equation for the average wave spectrum is established, and the effective growth/damping rate for the spectrum is calculated. Given a simple power-law spectrum, an anomalous collision frequency can be derived which depends on the slope and average intensity of the spectrum, and on the gyrofrequency and the differential motion (with respect to the wave frame of the actual ion species considered. The wave-particle interaction terms attain simple forms resembling the ones for collisional friction and temperature anisotropy relaxation (due to pitch angle scattering with collision rates that are proportional to the gyrofrequency but diminished substantially by the relative wave energy or the fluctuation level with respect the background field. In addition, a set of quasilinear diffusion equations is derived for the reduced (with respect to the perpendicular velocity component velocity distribution functions (VDFs, as they occur in the wave dispersion equation and the related dielectric function for parallel propagation. These reduced VDFs allow one to describe adequately the most prominent observed features, such as an ion beam and temperature anisotropy, in association with the resonant interactions of the particles with the waves on a kinetic level, yet have the advantage of being only dependent upon the parallel velocity component.

Cross-field dust acoustic instability in a dusty negative ion plasma

International Nuclear Information System (INIS)

Rosenberg, M

2010-01-01

A cross-field dust acoustic instability in a dusty negative ion plasma in a magnetic field is studied using kinetic theory. The instability is driven by the ExB drifts of the ions. It is assumed that the negative ions are much heavier than the positive ions, and that the dust is negatively charged. The case where the positive ions and electrons are magnetized, the negative ions are marginally unmagnetized, and the dust is unmagnetized is considered. The focus is on a situation where Doppler resonances near harmonics of the positive ion gyrofrequency can affect the spectrum of unstable dust acoustic waves. Application to possible laboratory experimental parameters is discussed.

Convective instability of RCP modes for a magnetized chiral plasma

International Nuclear Information System (INIS)

Torres-Silva, Hector; Sakanaka, P.H.; Reggiani, N.

1998-01-01

Using the Maxwell's equations and the proposed constitutive relations for a chiral plasma medium, the dispersion relations for right circularly polarized waves, (RCP), depending on the characteristics of the distribution, a new mode conversion and instabilities are found due to the chiral effect. From the dispersion relations and considering that the chirowave magnetic field may be important when the condition of velocity isotropy is dropped, we find that growing modes (instabilities) can occur at resonance and for frequencies below the electron gyrofrequency. We study, in this paper, the convective instability of RCP waves in a two-component bi-Lorentzian chiroplasma which can model the solar wind particle distributions. (author)

Attenuation bands and cut-off frequencies for ELF electromagnetic waves

International Nuclear Information System (INIS)

Rauch, J.L.; Lefeuvre, F.; Cerisier, J.C.; Berthelier, J.J.; Boud'ko, N.; Michailova, G.; Kapustina, O.

1985-01-01

The propagation characteristic of ELF (10 Hz - 1500 Hz) electromagnetic waves observed on ARCAD 3, in three different zones: low L value (L 6). Unambiguous determinations of the wave normal directions are obtained from the interpretations of the measurements of four (3 magnetic, 1 electric) wave field components. The technique that is used, is based on the Means method in the cases of highly polarized waves and on the Storey and Lefeuvre WDF method in the other cases. A particular emphasis is put on the propagation characteristics of the waves, in a multiple ion plasma, and on the cut-off frequencies which appear at and below the local proton gyrofrequency

Ray tracing of auroral Z mode radiation, AKR and auroral hiss

International Nuclear Information System (INIS)

Horne, R.B.; Jones, D.; Kimura, I.; Sawada, A.

1990-01-01

While observed frequency bandwidths of auroral Z mode radiation cannot be directly accounted for in terms of direct cyclotron maser instability generation, ray tracing in a hot plasma indicates that if the radiation near a plasma frequency lower than the gyrofrequency, the observed bandwidths are explainable in terms of upward propagation away from the earth. An auroral Z-mode generation mechanism is proposed involving mode conversion from O-mode auroral kilometric radiation (AKR) at the plasma frequency, as well as mode conversion from upgoing auroral hiss. Ray tracings in the O mode identify a possible AKR source region along L = 8.55. 11 refs

Pick-Up Ion Instabilities at Planetary Magnetospheres

Science.gov (United States)

Strangeway, Robert J.; Sharber, James (Technical Monitor)

2001-01-01

This effort involved the analysis of low frequency waves as observed by the Galileo spacecraft near the Galilean moon, Io. Io is a significant source of material, especially SO2, and various products of dissociation, and further these atoms and molecules are readily ionized. The initial velocity of the ions is essentially that of the neutral species, i.e., the Keplerian velocity. The plasma, on the other hand is co-rotating, and there is a differential flow of the order 57 km/s between the plasma and the neutral particles. Thus pick-up ion instabilities are Rely to occur within the Jovian magnetosphere. Indeed, magnetometer observations from the Galileo spacecraft clearly show ion cyclotron waves that have been identified with a large variety of plasma species, such as O+, S++ (which has the same gyro-frequency as O+), S+, and SO2+. Typically, however, the dominant frequency is near the SO2+ gyro-frequency. The research effort was originally planned to be a team effort between Robert J. Strangeway as the Principal Investigator, and Debbie Huddleston, who was an Assistant Research Geophysicist at UCLA. Unfortunately, Dr. Huddleston took a position within Industry. The effort was therefore descoped, and Dr. Strangeway instead pursued a collaboration with Dr. Xochitl Blanco-Cano, of the Instituto de Geofisica, Universidad Nacional Autonoma de Mexico. This has proved to be a productive collaboration, with several papers and publications arising out of the effort. The magnetic field oscillations near lo generally fall into two types: ion cyclotron waves, with frequencies near an ion gyro-frequency, and lower frequency mirror-mode waves. The ion cyclotron waves are mainly transverse, and frequently propagate along the ambient magnetic field. The mirror-mode waves are compressional waves, and they have essentially zero frequency in the plasma rest frame. One of the purposes of our investigation is to understand what controls the types of wave modes that occur, since both

Spectral properties of electromagnetic turbulence in plasmas

Directory of Open Access Journals (Sweden)

D. Shaikh

2009-03-01

Full Text Available We report on the nonlinear turbulent processes associated with electromagnetic waves in plasmas. We focus on low-frequency (in comparison with the electron gyrofrequency nonlinearly interacting electron whistlers and nonlinearly interacting Hall-magnetohydrodynamic (H-MHD fluctuations in a magnetized plasma. Nonlinear whistler mode turbulence study in a magnetized plasma involves incompressible electrons and immobile ions. Two-dimensional turbulent interactions and subsequent energy cascades are critically influenced by the electron whisters that behave distinctly for scales smaller and larger than the electron skin depth. It is found that in whistler mode turbulence there results a dual cascade primarily due to the forward spectral migration of energy that coexists with a backward spectral transfer of mean squared magnetic potential. Finally, inclusion of the ion dynamics, resulting from a two fluid description of the H-MHD plasma, leads to several interesting results that are typically observed in the solar wind plasma. Particularly in the solar wind, the high-time-resolution databases identify a spectral break at the end of the MHD inertial range spectrum that corresponds to a high-frequency regime. In the latter, turbulent cascades cannot be explained by the usual MHD model and a finite frequency effect (in comparison with the ion gyrofrequency arising from the ion inertia is essentially included to discern the dynamics of the smaller length scales (in comparison with the ion skin depth. This leads to a nonlinear H-MHD model, which is presented in this paper. With the help of our 3-D H-MHD code, we find that the characteristic turbulent interactions in the high-frequency regime evolve typically on kinetic-Alfvén time-scales. The turbulent fluctuation associated with kinetic-Alfvén interactions are compressive and anisotropic and possess equipartition of the kinetic and magnetic energies.

The effect of plasma drift on the electromagnetic cyclotron instability

International Nuclear Information System (INIS)

Kulkarni, V.H.; Rycroft, M.J.

1979-01-01

It is shown that the drift of plasma across a homogeneous magnetic field causes the generation of a wave electric field which, for waves propagating along the magnetic field in the whistler mode, is in the direction of the magnetic field. This leads to Landau damping of the wave field by the background electron distribution, simultaneously with amplification via the electromagnetic cyclotron instability. The drift velocity of the plasma for zero net growth of a whistler mode signal is calculated. It is suggested that such a process occurs in the equatorial region of the magnetosphere during a geomagnetic storm and accounts for the missing band of emissions at half the equatorial gyrofrequency. (Auth.)

The MMS observation of an off-equatorial dipolarization front and associated wave characteristics in the near-Earth magnetotail

Science.gov (United States)

Li, H.; Guo, L.; Zhou, M.; Cheng, Q.; Yu, X.; Huang, S.; Pang, Y.

2017-12-01

In this paper, we report the observation of the off-equatorial depolarization front structures by Magnetospheric Multiscale (MMS) mission at around X -8Re in the Earth's magnetotail. The dipolarization front was located at the flow rebounce region associated with a parallel electron beam. A large lower frequency electromagnetic wave fluctuation at the depolarization front is observed with the frequency near the ion gyrofrequency, left-handed polarization and a parallel propagation. A parallel current attributed to an electron beam coexist with the wave. The wave is believed to be generated by the current-driven ion cyclotron instability. Such instability is important because of its potential contribution to global electromagnetic energy conversion at the dipolarization front.

Analytic properties of the whistler dispersion function

International Nuclear Information System (INIS)

Daniell, G.J.

1986-01-01

The analytic properties of the dispersion function of a whistler are investigated in the complex frequency plane. It possesses a pole and a branch point at a frequency equal to the minimum value of the electron gyrofrequency along the path of propagation. An integral equation relates the dispersion function to the distribution of magnetospheric electrons along the path and the solution of this equation is obtained. It is found that the electron density in the equatorial plane is very simply related to the dispersion function. A discussion of approximate formulae to represent the dispersion shows how particular terms can be related to attributes of the electron density distribution, and a new approximate formula is proposed. (author)

Runaway tails in magnetized plasmas

Science.gov (United States)

Moghaddam-Taaheri, E.; Vlahos, L.; Rowland, H. L.; Papadopoulos, K.

1985-01-01

The evolution of a runaway tail driven by a dc electric field in a magnetized plasma is analyzed. Depending on the strength of the electric field and the ratio of plasma to gyrofrequency, there are three different regimes in the evolution of the tail. The tail can be (1) stable with electrons accelerated to large parallel velocities, (2) unstable to Cerenkov resonance because of the depletion of the bulk and the formation of a positive slope, (3) unstable to the anomalous Doppler resonance instability driven by the large velocity anisotropy in the tail. Once an instability is triggered (Cerenkov or anomalous Doppler resonance) the tail relaxes into an isotropic distribution. The role of a convection type loss term is also discussed.

Adiabatic theory of nonlinear electron cyclotron resonance heating

International Nuclear Information System (INIS)

Kotel'nikov, I.A.; Stupakov, G.V.

1989-01-01

Plasma heating at electron frequency by an ordinary wave propagating at right angle to unidirectional magnetic field is treated. Injected microwave power is assumed to be so large that relativistic change of electron gyrofrequency during one flight thorugh the wave beam is much greater than inverse time of flight. The electron motion in the wave field is described using Hamiltonian formalism in adiabatic approximation. It is shown that energy coupling from the wave to electrons is due to a bifurcation of electron trajectory which results in a jumpm of the adiabatic invariant. The probability of bifurcational transition from one trajectory to another is calculated analytically and is used for the estimation of the beam power absorbed in plasma. 6 refs.; 2 figs

A new purely growing instability in a strongly magnetized nonuniform pair plasma

International Nuclear Information System (INIS)

Shukla, Nitin; Shukla, P.K.

2007-01-01

It is shown that a strongly magnetized nonuniform electron-positron (hereafter referred to as e-p or pair) plasma is unstable against low-frequency (in comparison with the electron gyrofrequency) electrostatic oscillations. For this purpose, a dispersion relation is derived by using the Poisson equation as well as the electron and positron continuity equations with the guiding center drifts for the electron and positron fluids. The dispersion relation admits a purely growing instability in the presence of the equilibrium density and magnetic field inhomogeneities. Physically, instability arises because of the inhomogeneous magnetic field induced differential electron and positron density fluctuations, which do not keep in phase with the electrostatic potential arising from the charge separation in our nonuniform pair plasmas

GEOS-1 observations of electrostatic waves, and their relationship with plasma parameters

International Nuclear Information System (INIS)

Christiansen, P.J.; Gough, M.P.; Martelli, G.; Beghin, C.; Decreau, P.; Jones, D.

1978-01-01

In this paper the authors describe and discuss the occurrence of natural wave emissions detected by GEOS-1 at frequencies above the electron gyrofrequency. The bulk of the data presented comes from the first six months of satellite operation and thus concerns mainly dayside phenomena. A classification of the wave phenomena is developed, and experimental evidence and morphological information relevant to this classification are given. Some preliminary comments on nightside observations are included. The results are discussed, and it is argued that they can be understood as manifestations of electron cyclotron harmonic (Bernstein) wave emission in a plasma parameter range which has only very recently received any theoretical examinations. This theme is further developed in a companion paper (Roennmark et al., 1978). (Auth.)

Dependence of electron beam instability growth rates on the beam-plasma system parameters

International Nuclear Information System (INIS)

Strangeway, R.J.

1982-01-01

Electron beam instabilites are studied by using a simple model for an electron beam streaming through a cold plasma, the beam being of finite width perpendicular to the ambient magnetic field. Through considerations of finite geometry and the coldness of the beam and background plasma, an instability similar to the two stream instability is assumed to be the means for wave growth in the system. Having found the maximum growth rate for one set of beam-plasma system parameters, this maximum growth rate is traced as these parameters are varied. The parameters that describe the system are the beam velocity (v/sub b/), electron gyrofrequency to ambient electron plasma frequency ratio (Ω/sub e//ω/sub p/e), the beam to background number density ratio (n/sub b//n/sub a/), and the beam width (a). When Ω/sub e//ω/sub p/e>1, a mode with Ω/sub e/<ω<ω/sub u/hr is found to be unstable, where Ω is the wave frequency and ω/sub u/hr is the upper hybrid resonance frequency. For low values of n/sub b//n/sub a/ and Ω/sub e/<ω/sub p/e, this mode is still present with ω/sub p/e<ω<ω/sub u/hr. If the beam density is large, n/sub b//n/sub a/approx. =1, the instability occures for frequencies just above the electron gyrofrequency. This mode may well be that observed in laboratory plasma before the system undergoes the beam-plasma discharge. There is another instability present, which occurs for ωapprox. =ω/sub p/e. The growth rates for this mode, which are generally larger than those found for the ωapprox. =ωuhr mode, are only weakly dependent on Ω/sub d//ω/sub p/e. That this mode is not always observed in the laboratory implies that some factors not considered in the present theory suppress this mode, specifically, finite beam length

Ion-cyclotron modes in weakly relatavistic plasmas

International Nuclear Information System (INIS)

Venugopal, C.; Kurian, P.J.; Renuka, G.

1994-01-01

We derive a dispersion relation for the perpendicular propagation of ion-cyclotron waves around the ion gyrofrequency Ω + in a weakly relativistic, anisotropic Maxwellian plasma. Using an ordering parameter ε, we separated out two dispersion relations, one of which is independent of the relativistic terms, while the other depends sensitively on them. The solutions of the former dispersion relation yield two modes: a low-frequency (LF) mode with a frequency ω + and a high-frequency (HF) mode with ω > Ω + . The plasma is stable to the propagation of these modes. The latter dispersion relation yields a new LF mode in addition to the modes supported by the non-relativistic dispersion relation. The two LF modes can coalesce to make the plasma unstable. These results are also verified numerically using a standard root solver. (author)

Dynamics of runaway tails with time-dependent sub-Dreicer dc fields in magnetized plasmas

International Nuclear Information System (INIS)

Moghaddam-Taaheri, E.; Vlahos, L.

1987-01-01

The evolution of runaway tails driven by sub-Dreicer time-dependent dc fields in a magnetized plasma are studied numerically using a quasilinear code based on the Ritz--Galerkin method and finite elements. It is found that the runaway tail maintained a negative slope during the dc field increase. Depending on the values of the dc electric field at t = 0 and the electron gyrofrequency to the plasma frequency ratio the runaway tail became unstable to the anomalous Doppler resonance or remained stable before the saturation of the dc field at some maximum value. The systems that remained stable during this stage became unstable to the anomalous Doppler or the Cerenkov resonances when the dc field was kept at the saturation level or decreased. Once the instability is triggered, the runaway tail is isotropized

Dynamics of runaway tails with time-dependent sub-Dreicer dc fields in magnetized plasmas

Science.gov (United States)

Moghaddam-Taaheri, E.; Vlahos, L.

1987-01-01

The evolution of runaway tails driven by sub-Dreicer time-dependent dc fields in a magnetized plasma are studied numerically using a quasi-linear code based on the Ritz-Galerkin method and finite elements. It is found that the runaway tail maintained a negative slope during the dc field increase. Depending on the values of the dc electric field at t = 0 and the electron gyrofrequency to the plasma frequency ratio the runaway tail became unstable to the anomalous Doppler resonance or remained stable before the saturation of the dc field at some maximum value. The systems that remained stable during this stage became unstable to the anomalous Doppler or the Cerenkov resonances when the dc field was kept at the saturation level or decreased. Once the instability is triggered, the runaway tail is isotropized.

Ray tracing study of rising tone EMIC-triggered emissions

Science.gov (United States)

Hanzelka, Miroslav; Santolík, Ondřej; Grison, Benjamin; Cornilleau-Wehrlin, Nicole

2017-04-01

ElectroMagnetic Ion Cyclotron (EMIC) triggered emissions have been subject of extensive theoretical and experimental research in last years. These emissions are characterized by high coherence values and a frequency range of 0.5 - 2.0 Hz, close to local helium gyrofrequency. We perform ray tracing case studies of rising tone EMIC-triggered emissions observed by the Cluster spacecraft in both nightside and dayside regions off the equatorial plane. By comparison of simulated and measured wave properties, namely wave vector orientation, group velocity, dispersion and ellipticity of polarization, we determine possible source locations. Diffusive equilibrium density model and other, semi-empirical models are used with ion composition inferred from cross-over frequencies. Ray tracing simulations are done in cold plasma approximation with inclusion of Landau and cyclotron damping. Various widths, locations and profiles of plasmapause are tested.

Magnetization dynamics of imprinted non-collinear spin textures

Energy Technology Data Exchange (ETDEWEB)

Streubel, Robert, E-mail: r.streubel@ifw-dresden.de; Kopte, Martin; Makarov, Denys, E-mail: d.makarov@ifw-dresden.de [Institute for Integrative Nanosciences, IFW Dresden, 01069 Dresden (Germany); Fischer, Peter [Center for X-Ray Optics, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Physics Department, UC Santa Cruz, Santa Cruz, California 95064 (United States); Schmidt, Oliver G. [Institute for Integrative Nanosciences, IFW Dresden, 01069 Dresden (Germany); Material Systems for Nanoelectronics, Chemnitz University of Technology, 09107 Chemnitz (Germany)

2015-09-14

We study the magnetization dynamics of non-collinear spin textures realized via imprint of the magnetic vortex state in soft permalloy into magnetically hard out-of-plane magnetized Co/Pd nanopatterned heterostructures. Tuning the interlayer exchange coupling between soft- and hard-magnetic subsystems provides means to tailor the magnetic state in the Co/Pd stack from being vortex- to donut-like with different core sizes. While the imprinted vortex spin texture leads to the dynamics similar to the one observed for vortices in permalloy disks, the donut-like state causes the appearance of two gyrofrequencies characteristic of the early and later stages of the magnetization dynamics. The dynamics are described using the Thiele equation supported by the full scale micromagnetic simulations by taking into account an enlarged core size of the donut states compared to magnetic vortices.

Resonant acceleration of alpha particles by ion cyclotron waves in the solar wind

Science.gov (United States)

Gomberoff, L.; Elgueta, R.

1991-06-01

Preferential acceleration of alpha particles interacting with left-hand polarized ion cyclotron waves is studied. It is shown that a small positive drift velocity between alpha particles and protons can lead to alpha particle velocities well in excess of the proton bulk velocity. During the acceleration process, which is assumed to take place at heliocentric distances less than 0.3 AU, the alpha particle drift velocity should exceed the proton bulk velocity, and then the gap which exists around the alpha particle gyrofrequency should disappear. It is also shown that for proton thermal anisotropies of the order of those observed in fast solar wind, the waves either grow or are not damped excessively, so that the waves can exist and might thus lead to the observed differential speeds. However, the way in which the alpha particles exceed the proton velocity remains unexplained.

Waveform and packet structure of lion roars

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W. Baumjohann

1999-12-01

Full Text Available The Equator-S magnetometer is very sensitive and has a sampling rate of normally 128 Hz. The high sampling rate allows for the first time fluxgate magnetometer measurements of ELF waves between the ion cyclotron and the lower hybrid frequencies in the equatorial dayside magnetosheath. The so-called lion roars, typically seen by the Equator-S magnetometer at the bottom of the magnetic troughs of magnetosheath mirror waves, are near-monochromatic packets of electron whistler waves lasting for a few wave cycles only, typically 0.25 s. They are right-hand circularly polarized waves with typical amplitudes of 0.5–1 nT at around one tenth of the electron gyrofrequency. The cone angle between wave vector and ambient field is usually smaller than 1.5°.Key words. Interplanetary physics (MHD waves and turbulence; plasma waves and turbulence

Electromagnetic ion cyclotron waves in the plasma depletion layer

Science.gov (United States)

Denton, Richard E.; Hudson, Mary K.; Fuselier, Stephen A.; Anderson, Brian J.

1993-01-01

Results of a study of the theoretical properties of electromagnetic ion cyclotron (EMIC) waves which occur in the plasma depletion layer are presented. The analysis assumes a homogeneous plasma with the characteristics which were measured by the AMPTE/CCE satellite at 1450-1501 UT on October 5, 1984. Waves were observed in the Pc 1 frequency range below the hydrogen gyrofrequency, and these waves are identified as EMIC waves. The higher-frequency instability is driven by the temperature anisotropy of the H(+) ions, while the lower-frequency instability is driven by the temperature anisotropy of the He(2+) ions. It is argued that the higher-frequency waves will have k roughly parallel to B(0) and will be left-hand polarized, while the lower frequency wave band will have k oblique to B(0) and will be linearly polarized, in agreement with observations.

Amplification of electromagnetic ion cyclotron waves along a wave path in the Earth's multicomponent magnetosphere

International Nuclear Information System (INIS)

Hu, Y.D.; Fraser, B.J.; Olson, J.V.

1990-01-01

In this report, the authors consider the amplification of electromagnetic ion cyclotron waves along a geomagnetic field line in the multicomponent magnetosphere, assuming that the waves propagate parallel to the background magnetic field. The find it is possible for the ring-current protons (energy ∼ 10-100 keV), which supply the free energy to stimulate the waves, to resonate with the waves not only in the equatorial region but also off the equator. An instability, caused by a thermal anisotropy, may occur in separated regions on and/or off the equator. The positions of the source regions along the wave path depend on the concentration of cold heavy ion species. The significant off-equator source regions may be located at geomagnetic latitudes where the waves, with frequencies greater than the He + gyrofrequency on the equator, are in a local He + pass band

Whistler wave trapping in a density crest

International Nuclear Information System (INIS)

Sugai, H.; Niki, H.; Inutake, M.; Takeda, S.

1979-11-01

The linear trapping process of whistler waves in a field-aligned density crest is investigated theoretically and experimentally below ω = ωsub(c)/2 (half gyrofrequency). The conditions of the crest trapping are derived in terms of the frequency ω/ωsub(c), the incident wave-normal angle theta sub(i), and the density ratio n sub(i)/n sub(o), where n sub(i) and n sub(o) denote the density at the incident point and that at the ridge, respectively. The oscillation length of the trapped ray path is calculated for a parabolic density profile. The experiment on antenna-excited whistler wave has been performed in a large magnetized plasma with the density crest. The phase and amplitude profile of the whistler wave is measured along and across the crest. The measurement has verified characteristic behaviors of the crest trapping. (author)

Waveform and packet structure of lion roars

Directory of Open Access Journals (Sweden)

W. Baumjohann

Full Text Available The Equator-S magnetometer is very sensitive and has a sampling rate of normally 128 Hz. The high sampling rate allows for the first time fluxgate magnetometer measurements of ELF waves between the ion cyclotron and the lower hybrid frequencies in the equatorial dayside magnetosheath. The so-called lion roars, typically seen by the Equator-S magnetometer at the bottom of the magnetic troughs of magnetosheath mirror waves, are near-monochromatic packets of electron whistler waves lasting for a few wave cycles only, typically 0.25 s. They are right-hand circularly polarized waves with typical amplitudes of 0.5–1 nT at around one tenth of the electron gyrofrequency. The cone angle between wave vector and ambient field is usually smaller than 1.5^°.

Key words. Interplanetary physics (MHD waves and turbulence; plasma waves and turbulence

Production of artificial ionospheric layers by frequency sweeping near the 2nd gyroharmonic

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T. Pedersen

2011-01-01

Full Text Available Artificial ionospheric plasmas descending from the background F-region have been observed on multiple occasions at the High Frequency Active Auroral Research Program (HAARP facility since it reached full 3.6 MW power. Proximity of the transmitter frequency to the 2nd harmonic of the electron gyrofrequency (2fce has been noted as a requirement for their occurrence, and their disappearance after only a few minutes has been attributed to the increasing frequency mismatch at lower altitudes. We report new experiments employing frequency sweeps to match 2fce in the artificial plasmas as they descend. In addition to revealing the dependence on the 2fce resonance, this technique reliably produces descending plasmas in multiple transmitter beam positions and appears to increase their stability and lifetime. High-speed ionosonde measurements are used to monitor the altitude and density of the artificial plasmas during both the formation and decay stages.

On the instability of a spatially confined electron beam in a magnetized plasma

International Nuclear Information System (INIS)

Strangeway, R.J.

1980-01-01

The instability of a field-aligned electron beam of finite width streaming through a uniform magnetized plasma is investigated. The nature of the normal modes, and the wave field variation within the beam region are studied. It is found that an electrostatic approximation is useful in describing the general form of the dispersion relation, specifically showing how the beam width controls the range of allowed solutions. The electrostatic approximation is shown to be good for most of the range of frequencies considered. When the electron gyrofrequency is greater than the electron plasma frequency, the theory predicts that the cold plasma upper-hybrid resonance (Z mode) is stable to negative Landau damping. A criterion for applying this result to beam-plasma systems other than the ones investigated here is developed, and it is found that the effect should be more readily observable in laboratory experiments than in space plasmas. (author)

Nonlinear interaction of energetic ring current protons with magnetospheric hydromagnetic waves

International Nuclear Information System (INIS)

Chan, A.A.; Chen, L.; White, R.B.

1989-01-01

In order to study nonlinear wave-particle interactions in the Earth's magnetosphere we have derived Hamiltonian equations for the gyrophase-averaged nonrelativistic motion of charged particles in a perturbed dipole magnetic field. We assume low frequency (less than the proton gyrofrequency) fully electromagnetic perturbations, and we retain finite Larmor radius effects. Analytic and numerical results for the stochastic threshold of energetic protons (approx-gt 100 keV) in compressional geomagnetic pulsations in the Pc 5 range of frequencies 150--600 seconds are presented. These protons undergo a drift-bounce resonance with the Pc 5 waves which breaks the second (longitudinal) and third (flux) adiabatic invariants, while the first invariant (the magnetic moment) and the proton energy are approximately conserved. The proton motion in the observed spectrum of waves is found to be strongly diffusive, due to the overlap of neighboring primary resonances. copyright American Geophysical Union 1989

Nonlinear interaction of energetic ring current protons with magnetospheric hydromagnetic waves

International Nuclear Information System (INIS)

Chan, A.A.; Chen, Liu; White, R.B.

1989-09-01

In order to study nonlinear wave-particle interactions in the earth's magnetosphere we have derived Hamiltonian equations for the gyrophase-averaged nonrealistic motion of charged particles in a perturbed dipole magnetic field. We assume low frequency (less than the proton gyrofrequency) fully electromagnetic perturbations, and we retain finite Larmor radius effects. Analytic and numerical results for the stochastic threshold of energetic protons (approx gt 100 keV) in compressional geomagnetic pulsations in the Pc 5 range of frequencies (150--600 seconds) are presented. These protons undergo a drift-bounce resonance with the Pc 5 waves which breaks the second (longitudinal) and third (flux) adiabatic invariants, while the first invariant (the magnetic moment) and the proton energy are approximately conserved. The proton motion in the observed spectrum of waves is found to be strongly diffusive, due to the overlap of neighboring primary resonances. 17 refs., 2 figs

Low-frequency modes with high toroidal mode numbers. A general formulation

International Nuclear Information System (INIS)

Pegoraro, F.; Schep, T.J.

1979-09-01

Low-frequency waves with high toroidal mode numbers in an axisymmetric toroidal configuration are studied. In particular, the relationship between the periodicity constraints imposed by the geometry, magnetic shear and the spatial structure of eigenmodes is investigated. By exploiting the radial translational invariance and the poloidal periodicity of the gyrokinetic and Maxwell equations, the two-dimensional problem can be converted into a one-dimensional one and the mode structure can be expressed in terms of a single extended poloidal variable. This representation is used in the description of electromagnetic modes with phase velocities larger than the ion thermal velocity and with frequencies below the ion gyro-frequency. Trapped particle, curvature and compressional effects are retained. The dispersion equations for drift mode and Alfven-type modes are given in general geometry and simplified solutions are presented in the configuration of a double periodic plane slab. (Auth.)

Magnetosheath excursion and the relevant transport process at the magnetopause

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C. L. Cai

2009-08-01

Full Text Available A large-amplitude excursion of the magnetosheath (MS in quiet solar wind conditions on 17 March 2004 was recorded simultaneously by the Cluster and TC-1 spacecraft. During this period, the IMF Bz was entirely northward. The coherence between the bow shock motion and magnetopause (MP motion is revealed and the excursion velocities of the bow shock motion are analyzed. In addition, the relevant plasma transport phenomenon in the form of flux fluctuations below the ion gyrofrequency at the MP is exposed and is interpreted as manifestation of the drift instability. Correlated observations on charge accumulation and electrostatic potential perturbation are recorded by electron measurements in high energy regime, and also the eventual cross-field vortex motion in the nonlinear stage and the consequential mass exchange are exhibited. The present investigation gives some new insight into the MS plasma transport mechanism across the subsolar MP region in quiet solar wind conditions during a period of northward IMF.

Ion stochastic heating by obliquely propagating magnetosonic waves

International Nuclear Information System (INIS)

Gao Xinliang; Lu Quanming; Wu Mingyu; Wang Shui

2012-01-01

The ion motions in obliquely propagating Alfven waves with sufficiently large amplitudes have already been studied by Chen et al.[Phys. Plasmas 8, 4713 (2001)], and it was found that the ion motions are stochastic when the wave frequency is at a fraction of the ion gyro-frequency. In this paper, with test particle simulations, we investigate the ion motions in obliquely propagating magnetosonic waves and find that the ion motions also become stochastic when the amplitude of the magnetosonic waves is sufficiently large due to the resonance at sub-cyclotron frequencies. Similar to the Alfven wave, the increase of the propagating angle, wave frequency, and the number of the wave modes can lower the stochastic threshold of the ion motions. However, because the magnetosonic waves become more and more compressive with the increase of the propagating angle, the decrease of the stochastic threshold with the increase of the propagating angle is more obvious in the magnetosonic waves than that in the Alfven waves.

Generation of ion-acoustic and magnetoacoustic waves in an RF helicon discharge

International Nuclear Information System (INIS)

Belov, A. S.; Markov, G. A.

2006-01-01

A study is made of the generation of ion-acoustic and magnetoacoustic waves in a discharge excited in an external magnetic field by an electromagnetic wave in the whistler frequency range (ω LH He , where ω LH = √(ω He ω Hi ) and ω He and ω Hi are the electron and ion gyrofrequencies, respectively). The excitation of acoustic waves is attributed to the decay of a high-frequency hybrid mode forming a plasma waveguide into low-frequency acoustic waves and new high-frequency waves that satisfy both the decay conditions and the waveguide dispersion relations. The excitation of acoustic waves is resonant in character because the conditions for the generation of waveguide modes and for the occurrence of the corresponding nonlinear wave processes should be satisfied simultaneously. An unexpected effect is the generation of magnetoacoustic waves by whistlers. A diagnostic technique is proposed that allows one to determine the thermal electron velocity by analyzing decay conditions and dispersion relations for waves in the discharge channel

Magnetospheric plasma physics

International Nuclear Information System (INIS)

Bingham, R.

1989-09-01

The discovery of the earth's radiation belts in 1957 by Van Allen marked the beginning of what is now known as magnetospheric physics. In this study of plasma physics in the magnetosphere, we shall take the magnetosphere to be that part of the earth's ionized atmosphere which is formed by the interaction of the solar wind with the earth's dipole-like magnetic field. It extends from approximately 100km above the earth's surface where the proton-neutral atom collision frequency is equal to the proton gyrofrequency to about ten earth radii (R E ∼ 6380km) in the sunward direction and to several hundred earth radii in the anti-sunward direction. The collision dominated region is called the ionosphere and is sometimes considered separate from the collisionless plasma region. In the ionosphere ion-neutral collisions are dominant and one may think of the ionosphere as a frictional boundary layer ∼ 1000km thick. Other planets are also considered. (author)

Properties of transit-time interactions in magnetized plasmas: Analytic and numerical results

International Nuclear Information System (INIS)

Melatos, A.; Robinson, P.A.

1993-01-01

The recently developed perturbation theory of transit-time interactions between particles and coherent wave packets in magnetized plasmas is applied to particular field structures. Limits of validity are determined by comparison with test-particle simulations, showing that the theory is accurate everywhere except near certain well-determined resonances, for wave fields exceeding a characteristic threshold, and for particles below a particular velocity. The properties of transit-time interactions in magnetized plasmas are investigated in detail to determine their dependence on the fields and parameters of the particle motion. Resonant particle scattering is found to occur at low particle velocities when the frequency of the coherent wave packet is an integer multiple of the gyrofrequency. Two different types of resonant transit-time dissipation are also observed: one arises from transient cyclotron acceleration in the localized wave packet, the other from beating between the gyration of the particles and the oscillation of the wave packet field. Both effects involve an interplay between the field geometry and resonant oscillations

Enhancement of wave growth for warm plasmas with a high-energy tail distribution

Science.gov (United States)

Thorne, Richard M.; Summers, Danny

1991-01-01

The classical linear theory of electromagnetic wave growth in a warm plasma is considered for waves propagating parallel to a uniform ambient magnetic field. Wave-growth rates are calculated for ion-driven right-hand mode waves for Kappa and Maxwellian particle distribution functions and for various values of the spectral index, the temperature anisotropy, and the ratio of plasma pressure to magnetic pressure appropriate to the solar wind. When the anisotropy is low the wave growth is limited to frequencies below the proton gyrofrequency and the growth rate increases dramatically as the spectral index is reduced. The growth rate for any Kappa distribution greatly exceeds that for a Maxwellian with the same bulk properties. For large thermal anisotropy the growth rate from either distribution is greatly enhanced. The growth rates from a Kappa distribution are generally larger than for a Maxwellian distribution, and significant wave growth occurs over a broader range of frequencies.

Characteristics of AKR sources: A statistical description

International Nuclear Information System (INIS)

Hilgers, A.; Roux, A.; Lundin, R.

1991-01-01

A description of plasma properties within the sources of the Auroral Kilometric Radiation (AKR) is given. It is based on data collected during ∼ 50 AKR source crossings in the altitude range between 4,000 and 9,000 km by the Swedish spacecraft Viking. The following results are obtained; (i) the frequency of the lowest frequency peak of the AKR f peak is found to be very close to f ce , the electron gyrofrequency ((f peak -f ce )/f ce ≤ 0.08), on the average, (ii) the lower cutoff frequency f LC is on the average at f ce ((f LC -f ce )/f ce ≅ 0), (iii) in the sources the density is typically less than 1.5 cm -3 , which is of the order of the density of hot electrons and (iv) the source is located within an acceleration region, as evidenced by electrons accelerated above and ions accelerated below

Research in magnetospheric wave phenomena

International Nuclear Information System (INIS)

Barfield, J.N.

1975-01-01

During the last 4 years a number of developments have occurred which have led to an increased understanding of the role of wave phenomena in the physical processes of the magnetosphere. While the studies span the frequency regime from millihertz to the electron gyrofrequency, the developments to be discussed in this paper have in common that they have added substantially to the understanding of the controlling processes, regions, and boundaries in the magnetosphere. The topics discussed are the increased awareness and documentation of the role of the plasmapause in micropulsation generation and propagation; the establishment of the role of ion cyclotron waves in the wave-particle interactions at the plasmapause; the discovery of magnetospheric electrostatic waves with ω = (3/2)Ω/sub -/; the discovery and preliminary identification of the source of plasmaspheric hiss; and the analysis of storm time Pc 5 waves as observed on the satellites ATS 1 and Explorer 45. (auth)

Theory of charged particle heating by low-frequency Alfven waves

International Nuclear Information System (INIS)

Guo Zehua; Crabtree, Chris; Chen, Liu

2008-01-01

The heating of charged particles by a linearly polarized and obliquely propagating shear Alfven wave (SAW) at frequencies a fraction of the charged particle cyclotron frequency is demonstrated both analytically and numerically. Applying Lie perturbation theory, with the wave amplitude as the perturbation parameter, the resonance conditions in the laboratory frame are systematically derived. At the lowest order, one recovers the well-known linear cyclotron resonance condition k parallel v parallel -ω-nΩ=0, where v parallel is the particle velocity parallel to the background magnetic field, k parallel is the parallel wave number, ω is the wave frequency, Ω is the gyrofrequency, and n is any integer. At higher orders, however, one discovers a novel nonlinear cyclotron resonance condition given by k parallel v parallel -ω-nΩ/2=0. Analytical predictions on the locations of fixed points, widths of resonances, and resonance overlapping criteria for global stochasticity are also found to agree with those given by computed Poincare surfaces of section

A Proton-Cyclotron Wave Storm Generated by Unstable Proton Distribution Functions in the Solar Wind

Science.gov (United States)

Wicks, R. T.; Alexander, R. L.; Stevens, M.; Wilson, L. B., III; Moya, P. S.; Vinas, A.; Jian, L. K.; Roberts, D. A.; O’Modhrain, S.; Gilbert, J. A.;

Excitation of plasma waves by unstable photoelectron and thermal electron populations on closed magnetic field lines in the Martian ionosphere

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N. Borisov

2005-06-01

Full Text Available It is argued that anisotropic electron pitch angle distributions in the closed magnetic field regions of the Martian ionosphere gives rise to excitation of plasma instabilities. We discuss two types of instabilities that are excited by two different populations of electrons. First, the generation of Langmuir waves by photoelectrons with energies of the order of 10eV is investigated. It is predicted that the measured anisotropy of their pitch angle distribution at the heights z≈400km causes excitation of waves with frequencies f~30kHz and wavelengths λ~30m. Near the terminators the instability of the electrostatic waves with frequencies of the order of or less than the electron gyrofrequency exited by thermal electrons is predicted. The typical frequencies of these waves depend on the local magnitude of the magnetic field and can achieve values f~3-5kHz above strong crustal magnetic fields.

Noncanonical Hamiltonian methods in plasma dynamics

International Nuclear Information System (INIS)

Kaufman, A.N.

1982-01-01

A Hamiltonian approach to plasma dynamics is described. The Poisson bracket of two observables g 1 and g 2 is given by using an antisymmetric tensor J, and must satisfy the Jacobi condition. The J can be obtained by elementary tensor analysis. The evolution in time of an observable g is given in terms of the Poisson bracket and a Hamiltonian H(Z). The guiding-center description of particle motion was presented by Littlejohn. The ponderomotive drift and force, the wave-induced oscillation-center velocity, and the gyrofrequency shift are obtained. The Lie transform yields the wave-induced increment to the gyromomentum. In the coulomb model for a Vlasov system, the dynamical variable is the Vlasov distribution f(z). The Hamiltonian functional and the Poisson bracket are obtained. The coupling of f(z) to the Maxwell field appears in the Poisson bracket. The evolution equation yields the Vlasov-Maxwell system. (Kato, T.)

An interferometer experiment to explore the aspect angle dependence of stimulated electromagnetic emission spectra

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Isham

2005-01-01

Full Text Available When the Earth's ionosphere is irradiated by a radiofrequency (RF electromagnetic wave of sufficiently high power density and tuned to match a natural E- or F-region plasma frequency, ionospheric magnetoionic wave modes may be excited and may generate RF electromagnetic sideband waves via nonlinear interactions. These secondary emissions, which may then escape from the ionosphere, have been termed stimulated electromagnetic emission or SEE. The frequency spectra of this radiation has been studied extensively, and a number of characteristic spectral features have been identified and in some cases related to particular plasma processes. The separation in frequency between the RF pump and the harmonics of the local electron gyrofrequency is critical in determining the amount of anomalous absorption suffered by the pump wave and the spectral properties of the stimulated sidebands. The pump can excite electrostatic waves which do not propagate away but can in some cases be observed via radio-wave scattering from the electron density fluctuations associated with them. These enhanced density fluctuations are created by processes commonly referred to as upper-hybrid and Langmuir turbulence. Langmuir turbulence has been the subject of 930-MHz scattering observations with antenna scanning through several pre-selected angles between the geographic and geomagnetic zenith directions, and a preference for pointing angles between the Spitze angle and geomagnetic field-aligned was identified. Other phenomena, such as the generation of enhanced electron temperatures and artificial aurora, have more recently been shown to have special behavior at similar angles, near but apparently not quite at field-aligned. In view of this evidence for angular structure in several pump-induced effects, in light of the rich variety of SEE phenomena strongly dependent on the geomagnetic field via the frequency interval between the pump and the gyrofrequency harmonics, and in

An interferometer experiment to explore the aspect angle dependence of stimulated electromagnetic emission spectra

Directory of Open Access Journals (Sweden)

Isham

2005-01-01

Full Text Available When the Earth's ionosphere is irradiated by a radiofrequency (RF electromagnetic wave of sufficiently high power density and tuned to match a natural E- or F-region plasma frequency, ionospheric magnetoionic wave modes may be excited and may generate RF electromagnetic sideband waves via nonlinear interactions. These secondary emissions, which may then escape from the ionosphere, have been termed stimulated electromagnetic emission or SEE. The frequency spectra of this radiation has been studied extensively, and a number of characteristic spectral features have been identified and in some cases related to particular plasma processes. The separation in frequency between the RF pump and the harmonics of the local electron gyrofrequency is critical in determining the amount of anomalous absorption suffered by the pump wave and the spectral properties of the stimulated sidebands. The pump can excite electrostatic waves which do not propagate away but can in some cases be observed via radio-wave scattering from the electron density fluctuations associated with them. These enhanced density fluctuations are created by processes commonly referred to as upper-hybrid and Langmuir turbulence. Langmuir turbulence has been the subject of 930-MHz scattering observations with antenna scanning through several pre-selected angles between the geographic and geomagnetic zenith directions, and a preference for pointing angles between the Spitze angle and geomagnetic field-aligned was identified. Other phenomena, such as the generation of enhanced electron temperatures and artificial aurora, have more recently been shown to have special behavior at similar angles, near but apparently not quite at field-aligned. In view of this evidence for angular structure in several pump-induced effects, in light of the rich variety of SEE phenomena strongly dependent on the geomagnetic field via the frequency interval between the pump and the gyrofrequency harmonics, and in view

Plasma waves produced by an ion beam: observations by the VLF experiment on Porcupine

International Nuclear Information System (INIS)

Jones, D.

1980-01-01

Results are presented from the VLF electric field experiments flown on Porcupine flights F3 and F4, which also had ejectable xenon ion sources. The xenon ion beam was found to produce plasma instabilities whose frequencies could be linked to the local proton gyrofrequency fsub(cH + ). The main energy in the instabilities lies at approximately 3kHz for events when the Xe + source is close to the rocket, and at approximately 7kHz when the source is farther away. Theory predicts that these frequencies should be the lower-hybrid-resonance and this implies that Xe + is the dominant ion in the first case and that it is the ambient plasma that dominates later. There is no discernable antenna spin-modulation during the Xe events which indicates that the wave k-vectors are not unidirectional. A theory is cited based on the 'setting up' of the proton cyclotron harmonic waves by the Xe + or O + cyclotron harmonic waves. The second Xe + event on both flights exhibited an, as yet, unexplained harmonic structure related to fsub(cH + )/2. (Auth.)

Second harmonic electron cyclotron breakdown in stellarators

International Nuclear Information System (INIS)

Carter, M.D.; Batchelor, D.B.; England, A.C.

1987-01-01

In linear wave-particle interaction models, the coupling between cold electrons and microwaves with frequency equal to twice the electron gyrofrequency is so weak that the ionization of a significant number of neutral hydrogen atoms would seem impossible in practical applications. However, the non-linear interaction of a cold electron with the wave is very large if the electron becomes trapped near resonance in a shallow, static magnetic well. A model has been developed to describe the breakdown of a neutral gas when these non-linear interactions are considered, and it is in reasonable agreement with the limited amount of available experimental data. For gas pressures that are too large, electron-neutral collisions inhibit the non-linear interaction and prevent breakdown. For gas pressures that are too low, the growth rate of the free electron population is limited because electrons capable of causing ionization are lost before suffering a collision with a neutral. Quantitative growth rate predictions are presented for stellarators, and formulae for rough estimates are given. (author)

Letter to the Editor: First direct observations of the reduced striations at pump frequencies close to the electron gyroharmonics

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M. T. Rietveld

Full Text Available It is well known that the ionospheric plasma response to high-power HF radio waves changes drastically as the heater frequency approaches harmonics of the electron gyrofrequency. These include changes in the spectrum of the stimulated electromagnetic emission, reduction in the anomalous absorption of low-power diagnostic waves propagating through the heated volume, and reduction in the large scale F-region heating. Theoretical models as well as previous experimental evidence point towards the absence of small-scale field-aligned plasma density irregularities at pump frequencies close to electron gyroharmonics as the main cause of these changes. Results presented in this paper are the first direct observations of the reduced striations at the 3rd gyroharmonic made by the CUTLASS radar. In addition, simultaneous EISCAT observations have revealed that the "enhanced ion-line" usually present in the EISCAT ion-line spectrum during the first few seconds after heater switch on, persisted at varying strengths while the heater was transmitting at frequencies close to the 3rd electron gyroharmonics.Key words. Ionosphere (active experiments; ionospheric irregularities · Radio science (ionospheric physics

Effects of heavy ion temperature on low-frequency kinetic Alfven waves

International Nuclear Information System (INIS)

Yang, L.; Wu, D. J.

2011-01-01

Heavy ion-electron (or proton) temperature ratio varies in a wide range in the solar and space environment. In this paper, proton and heavy ion temperatures are included in a three-fluid plasma model. For the specified parameters, low-frequency (<< heavy ion gyrofrequency) kinetic Alfven waves (KAWs) with sub- and super-Alfvenic speeds are found to coexist in the same plasma environment. Our results show that the temperature ratio of heavy ions to electrons can considerably affect the dispersion, propagation, and electromagnetic polarizations of the KAWs. In particular, the temperature ratio can increase the ratio of parallel to perpendicular electric fields and the normalized electric to magnetic field ratio, the variations of which are greatly different in regions with a high heavy ion temperature and with a low one. The results may help to understand the physical mechanism of some energization processes of heavy ions in the solar and space plasma environment. Effects of the ratio of electron thermal to Alfven speeds and the heavy ion abundance on these parameters are also discussed.

Particle propagation, wave growth and energy dissipation in a flaring flux tube

Science.gov (United States)

White, S. M.; Melrose, D. B.; Dulk, G. A.

1986-01-01

Wave amplification by downgoing particles in a common flare model is investigated. The flare is assumed to occur at the top of a coronal magnetic flux loop, and results in the heating of plasma in the flaring region. The hot electrons propagate down the legs of the flux tube towards increasing magnetic field. It is simple to demonstrate that the velocity distributions which result in this model are unstable to both beam instabilities and cyclotron maser action. An explanation is presented for the propagation effects on the distribution, and the properties of the resulting amplified waves are explored, concentrating on cyclotron maser action, which has properties (emission in the z mode below the local gyrofrequency) quite different from maser action by other distributions considered in the context of solar flares. The z mode waves will be damped in the coronal plasma surrounding the flaring flux tube and lead to heating there. This process may be important in the overall energy budget of the flare. The downgoing maser is compared with the loss cone maser, which is more likely to produce observable bursts.

Letter to the Editor: First direct observations of the reduced striations at pump frequencies close to the electron gyroharmonics

Directory of Open Access Journals (Sweden)

F. Honary

1999-09-01

Full Text Available It is well known that the ionospheric plasma response to high-power HF radio waves changes drastically as the heater frequency approaches harmonics of the electron gyrofrequency. These include changes in the spectrum of the stimulated electromagnetic emission, reduction in the anomalous absorption of low-power diagnostic waves propagating through the heated volume, and reduction in the large scale F-region heating. Theoretical models as well as previous experimental evidence point towards the absence of small-scale field-aligned plasma density irregularities at pump frequencies close to electron gyroharmonics as the main cause of these changes. Results presented in this paper are the first direct observations of the reduced striations at the 3rd gyroharmonic made by the CUTLASS radar. In addition, simultaneous EISCAT observations have revealed that the "enhanced ion-line" usually present in the EISCAT ion-line spectrum during the first few seconds after heater switch on, persisted at varying strengths while the heater was transmitting at frequencies close to the 3rd electron gyroharmonics.Key words. Ionosphere (active experiments; ionospheric irregularities · Radio science (ionospheric physics

Chorus source region localization in the Earth's outer magnetosphere using THEMIS measurements

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O. Agapitov

2010-06-01

Full Text Available Discrete ELF/VLF chorus emissions, the most intense electromagnetic plasma waves observed in the Earth's radiation belts and outer magnetosphere, are thought to propagate roughly along magnetic field lines from a localized source region near the magnetic equator towards the magnetic poles. THEMIS project Electric Field Instrument (EFI and Search Coil Magnetometer (SCM measurements were used to determine the spatial scale of the chorus source localization region on the day side of the Earth's outer magnetosphere. We present simultaneous observations of the same chorus elements registered onboard several THEMIS spacecraft in 2007 when all the spacecraft were in the same orbit. Discrete chorus elements were observed at 0.15–0.25 of the local electron gyrofrequency, which is typical for the outer magnetosphere. We evaluated the Poynting flux and wave vector distribution and obtained chorus wave packet quasi-parallel propagation to the local magnetic field. Amplitude and phase correlation data analysis allowed us to estimate the characteristic spatial correlation scale transverse to the local magnetic field to be in the 2800–3200 km range.

Ion cyclotron waves: Direct compariosn between ground-based measurements and observations in the source region

International Nuclear Information System (INIS)

Perraut, S.; Gendrin, R.; Roux, A.; de Villedary, C.

1984-01-01

Simultaneous measurements of ion cyclotron waves (ICW's) were performed on GEOS spacecraft and in the vicinity of their magnetic footprints with the French Mobile station. The detailed comparison between the two sets of data shown that while ICW's having F + gyrofrequency at the equator, generally propagate to the ground, only 50% of those generated above F/sub He/ can reach the ground station. It is shown that these results are in good agreement with the conclusions that Rauch and Roux [1982] drew on the basis of measurements reported by Young et al 1981]. In an He + -rich plasma, ICW's with F>F/sub He/ suffer a reflection where the frequency locally matches the local bi-ion hybrid frequency. We extend the calculations of Rauch and Roux and calculate, as a function of the He + concentration, the tunneling of ICW's through the stopband induced by the presence of minor He + ions. It is shown that the transmission coefficient strongly depends upon the wave frequency for a given He + abundance ratio. The results obtained are shown to be supported by existing observations

Analytical study of the relativistic dispersion: Application to the generation of the auroral kilometric radiation

International Nuclear Information System (INIS)

Le Queau, D.; Louarn, P.

1989-01-01

The measurements recently performed by the Viking spacecraft have shown that, in addition to being cold plasma depleted, the source regions of the Auroral Kilometric Radiation (A.K.R.) are characterized by a relatively denser, more energetic electron component. In order to properly study the Cyclotron Maser Instability (C.M.I.) which is thought to be responsible for the A.K.R. generation, it is thus necessary to include relativistic corrections in both the hermitian and the antihermitian parts of the dielectric tensor characterizing the linear properties of the plasma. Here one presents an analytical study of the corresponding dispersion equation which aims to describe stable and unstable waves having frequencies lying very close to the electronic gyrofrequency and propagating across the geomagnetic field with a perpendicular refractive index less than a few units (n perpendicular 1 and χ small), the growth rate could maximize at the cut-off frequency of the relativistic X mode. Moreover, for small χ, the relativistic X mode is connected to freely propagating modes which guarantees an easy access of the electromagnetic energy to free space

Geometric Phase of the Gyromotion for Charged Particles in a Time-dependent Magnetic Field

International Nuclear Information System (INIS)

Liu, Jian; Qin, Hong

2011-01-01

We study the dynamics of the gyrophase of a charged particle in a magnetic field which is uniform in space but changes slowly with time. As the magnetic field evolves slowly with time, the changing of the gyrophase is composed of two parts. The rst part is the dynamical phase, which is the time integral of the instantaneous gyrofrequency. The second part, called geometric gyrophase, is more interesting, and it is an example of the geometric phase which has found many important applications in different branches of physics. If the magnetic field returns to the initial value after a loop in the parameter space, then the geometric gyrophase equals the solid angle spanned by the loop in the parameter space. This classical geometric gyrophase is compared with the geometric phase (the Berry phase) of the spin wave function of an electron placed in the same adiabatically changing magnetic field. Even though gyromotion is not the classical counterpart of the quantum spin, the similarities between the geometric phases of the two cases nevertheless reveal the similar geometric nature of the different physics laws governing these two physics phenomena.

Observation of proton chorus waves close to the equatorial plane by Cluster

Science.gov (United States)

Grison, B.; Pickett, J. S.; Santolik, O.; Robert, P.; Cornilleau-Wehrlin, N.; Engebretson, M. J.; Constantinescu, D. O.

2009-12-01

Whistler mode chorus waves are a widely studied phenomena. They are present in numerous regions of the magnetosphere and are presumed to originate in the magnetic equatorial region. In a spectrogram they are characterized by narrowband features with rise (or fall) in frequency over short periods of time. Being whistler mode waves around a few tenths of the electron cyclotron frequency they interact mainly with electrons. In the present study we report observations by the Cluster spacecraft of what we call proton chorus waves. They have spectral features with rising frequency, similar to the electron chorus waves, but they are detected in a frequency range that starts roughly at 0.50fH+ up to fH+ (the local proton gyro-frequency). The lower part of their spectrum seems to originate from monochromatic Pc 1 waves (1.5 Hz). Proton chorus waves are detected close to the magnetic equatorial plane in both hemispheres during the same event. Our interpretation of these waves as proton chorus is supported by polarization analysis with the Roproc procedures and the Prassadco software using both the magnetic (STAFF-SC) and electric (EFW) parts of the fluctuations spectrum.

Ulysses observations of magnetic waves due to newborn interstellar pickup ions. I. New observations and linear analysis

Energy Technology Data Exchange (ETDEWEB)

Cannon, Bradford E. [Physics Department, Florida State University, Tallahassee, FL (United States); Smith, Charles W.; Isenberg, Philip A.; Vasquez, Bernard J. [Physics Department and Space Science Center, Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, NH (United States); Murphy, Neil [Jet Propulsion Laboratory, Mail Stop 180-600, 4800 Oak Grove Drive, Pasadena, CA (United States); Nuno, Raquel G., E-mail: bc13h@my.fsu.edu, E-mail: Charles.Smith@unh.edu, E-mail: Phil.Isenberg@unh.edu, E-mail: Bernie.Vasquez@unh.edu, E-mail: Neil.Murphy@jpl.nasa.gov, E-mail: raquel.nuno@asu.edu [School of Earth and Space Exploration, Arizona State University, Tempe, AZ (United States)

2014-04-01

We have examined Ulysses magnetic field data using dynamic spectrogram techniques that compute wave amplitude, polarization, and direction of propagation over a broad range of frequencies and time. Events were identified that showed a strong polarization signature and an enhancement of power above the local proton gyrofrequency. We perform a statistical study of 502 wave events in an effort to determine when, where, and why they are observed. Most notably, we find that waves arising from newborn interstellar pickup ions are relatively rare and difficult to find. The quantities normally employed in theories of wave growth are neutral atom density and quantities related to their ionization and the subsequent dynamics such as wind speed, solar wind flux, and magnetic field orientation. We find the observations of waves to be largely uncorrelated to these quantities except for mean field direction where quasi-radial magnetic fields are favored and solar wind proton flux where wave observations appear to be favored by low flux conditions which runs contrary to theoretical expectations of wave generation. It would appear that an explanation based on source physics and instability growth rates alone is not adequate to account for the times when these waves are seen.

A combined wave distribution function and stability analysis of Viking particle and low-frequency wave data

International Nuclear Information System (INIS)

Oscarsson, T.E.; Roennmark, K.G.

1990-01-01

In this paper the authors present an investigation of low-frequency waves observed on auroral field lines below the acceleration region by the Swedish satellite Viking. The measured frequency spectra are peaked at half the local proton gyrofrequency, and the waves are observed in close connection with precipitating electrons. In order to obtain information about the distribution of wave energy in wave vector space, they reconstruct the wave distribution function (WDF) from observed spectral densities. They use a new scheme that allows them to reconstruct simultaneously the WDF over a broad frequency band. The method also makes it possible to take into account available particle observations as well as Doppler shifts caused by the relative motion between the plasma and the satellite. The distribution of energy in wave vector space suggested by the reconstructed WDF is found to be consistent with what is expected from a plasma instability driven by the observed precipitating electrons. Furthermore, by using UV images obtained on Viking, they demonstrate that the wave propagation directions indicated by the reconstructed WDFs are consistent with a simple model of the presumed wave source in the electron precipitation region

Magnetosphere VLF observation by satellite ISIS

International Nuclear Information System (INIS)

Ondo, Tadanori; Nakamura, Yoshikatsu; Watanabe, Shigeaki; Murakami, Toshimitsu

1978-01-01

On the basis of the VLF (50 Hz -- 30 kHz) electric field data from the satellite ISIS, the following works carried out in The Radio Research Laboratories are described: deuteron whistler and whistler duct, detection of plasmapause by LHR hiss, and the origin of 5 kHz hiss at low/middle latitudes. The deuteron whistlers are observable distinctly only at low latitude because of gyro-frequency and the frequency resolution of spectral analyzers. Whistler echo occurs when a whistler moves back and forth through a duct along the line of magnetic force, so it is considered that the ISIS satellite crosses the duct. The variation in ion composition around plasmapause obtained through LHR hiss is explainable by the plasamapause position and the magnetic storm effect on the plasamapause. Concerning the narrow band hiss of 5 kHz +- 1.0 kHz frequently observed on the ground at low/middle latitudes, it may occur around plasmapause, propagate through the ionosphere and then to the ground in waveguide mode, or otherwise, it may occur above the ionosphere and then propagate directly to the ground penetrating through the ionosphere. (J.P.N.)

Ion Bernstein wave heating in a multi-component plasma

International Nuclear Information System (INIS)

Puri, S.

1980-10-01

Conditions for the coupling and absorption of Gross-Bernstein ion-cyclotron waves in a multi-component plasma are examined. Two cases are distinguished depending upon whether, the antenna initially launches, (i) the quasi-torsional slow electromagnetic wave with azimuthal magnetic field (TM) polarization, or (ii) the quasi-compressional fast wave with the electric field oriented azimuthally (TE). Analytic expressions for the plasma surface impedance are derived taking into account the pertinent warm plasma modifications near the vacuum-plasma interface. Antenna configurations capable of efficient coupling of the radio frequency energy to these modes are studied. A method for simulating waveguide like launching using transmission lines is pointed out. It is found that impurity concentrations exceeding a few parts in a thousand are capable of competing with the bulk ions in the energy absorption processes; this could lead to energy deposition near the plasma edge. Measures for avoiding edge heating problems by a careful choice of parameters e.g. restricting the heating frequency to the fundamental ion gyrofrequency are outlined. Equal care is to be exercised in limiting the nsub(z) spectrum to low discrete values in order to avoid the potentially dangerous problem of runaway electron heating. (orig.)

First Observation of Lion Roar Emission in Saturn's Magnetosheath

Science.gov (United States)

Píša, D.; Sulaiman, A. H.; Santolík, O.; Hospodarsky, G. B.; Kurth, W. S.; Gurnett, D. A.

2018-01-01

We present an observation of intense emissions in Saturn's magnetosheath as detected by the Cassini spacecraft. The emissions are observed in the dawn sector (magnetic local time ˜06:45) of the magnetosheath over a time period of 11 h before the spacecraft crossed the bow shock and entered the unshocked solar wind. They are found to be narrow-banded with a peak frequency of about 0.16 fce, where fce is the local electron gyrofrequency. Using plane wave propagation analysis, we show that the waves are right hand circularly polarized in the spacecraft frame and propagate at small wave normal angles (lion roars" have been reported by numerous missions in the terrestrial magnetosheath. Here we show the first evidence such emission outside the terrestrial environment. Our observations suggest that lion roars are a solar-system-wide phenomenon and capable of existing in a broad range of parameter space. This also includes 1 order of magnitude difference in frequencies. We anticipate our result to provide new insight into such emissions in a new parameter regime characterized by a higher plasma beta (owing to the substantially higher Mach number bow shock) compared to Earth.

KINETIC PLASMA TURBULENCE IN THE FAST SOLAR WIND MEASURED BY CLUSTER

International Nuclear Information System (INIS)

Roberts, O. W.; Li, X.; Li, B.

2013-01-01

The k-filtering technique and wave polarization analysis are applied to Cluster magnetic field data to study plasma turbulence at the scale of the ion gyroradius in the fast solar wind. Waves are found propagating in directions nearly perpendicular to the background magnetic field at such scales. The frequencies of these waves in the solar wind frame are much smaller than the proton gyrofrequency. After the wavevector k is determined at each spacecraft frequency f sc , wave polarization property is analyzed in the plane perpendicular to k. Magnetic fluctuations have δB > δB ∥ (here the ∥ and refer to the background magnetic field B 0 ). The wave magnetic field has right-handed polarization at propagation angles θ kB 90°. The magnetic field in the plane perpendicular to B 0 , however, has no clear sense of a dominant polarization but local rotations. We discuss the merits and limitations of linear kinetic Alfvén waves (KAWs) and coherent Alfvén vortices in the interpretation of the data. We suggest that the fast solar wind turbulence may be populated with KAWs, small-scale current sheets, and Alfvén vortices at ion kinetic scales.

Analysis and simulation of BGK electron holes

Directory of Open Access Journals (Sweden)

L. Muschietti

1999-01-01

Full Text Available Recent observations from satellites crossing regions of magnetic-field-aligned electron streams reveal solitary potential structures that move at speeds much greater than the ion acoustic/thermal velocity. The structures appear as positive potential pulses rapidly drifting along the magnetic field, and are electrostatic in their rest frame. We interpret them as BGK electron holes supported by a drifting population of trapped electrons. Using Laplace transforms, we analyse the behavior of one phase-space electron hole. The resulting potential shapes and electron distribution functions are self-consistent and compatible with the field and particle data associated with the observed pulses. In particular, the spatial width increases with increasing amplitude. The stability of the analytic solution is tested by means of a two-dimensional particle-in-cell simulation code with open boundaries. We consider a strongly magnetized parameter regime in which the bounce frequency of the trapped electrons is much less than their gyrofrequency. Our investigation includes the influence of the ions, which in the frame of the hole appear as an incident beam, and impinge on the BGK potential with considerable energy. The nonlinear structure is remarkably resilient

Cluster observations of mid-latitude hiss near the plasmapause

Directory of Open Access Journals (Sweden)

A. Masson

2004-07-01

Full Text Available 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 2kHz to 10kHz. We show that below 4kHz, 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 2kHz, and (iv the central frequency of their emission band varies from 2kHz to 10kHz. 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 Kp index. This suggests either that these banded emissions are generated in a given f/fce range, or that there is a Kp dependent Doppler shift between the satellites and a possible moving source of the MLH.

A test of the Hall-MHD model: Application to low-frequency upstream waves at Venus

Science.gov (United States)

Orlowski, D. S.; Russell, C. T.; Krauss-Varban, D.; Omidi, N.

1994-01-01

Early studies suggested that in the range of parameter space where the wave angular frequency is less than the proton gyrofrequency and the plasma beta, the ratio of the thermal to magnetic pressure, is less than 1 magnetohydrodynamics provides an adequate description of the propagating modes in a plasma. However, recently, Lacombe et al. (1992) have reported significant differences between basic wave characteristics of the specific propagation modes derived from linear Vlasov and Hall-magnetohydrodynamic (MHD) theories even when the waves are only weakly damped. In this paper we compare the magnetic polarization and normalization magnetic compression ratio of ultra low frequency (ULF) upstream waves at Venus with magnetic polarization and normalized magnetic compression ratio derived from both theories. We find that while the 'kinetic' approach gives magnetic polarization and normalized magnetic compression ratio consistent with the data in the analyzed range of beta (0.5 less than beta less than 5) for the fast magnetosonic mode, the same wave characteristics derived from the Hall-MHD model strongly depend on beta and are consistent with the data only at low beta for the fast mode and at high beta for the intermediate mode.

On hard X-ray spectra of accreting neutron stars

International Nuclear Information System (INIS)

Zheleznyakov, V.V.

1982-01-01

Formation of the spectra of X-ray pulsars and gamma bursters is investigated. Interpretation of a hard X-ray spectrum of pulsars containing cyclotron lines is feasible on the basis of an isothermal model of a polar spot heated due to acccretion to a neutron star. It has been ascertained that in the regions responsible for the formation of continuum radiation and lines the mode polarization is determined by a magnetized vacuum rather than by a plasma. Bearing this in mind, the influence of the magnetic field of a star on the wide wings of the cyclotron line and on its depth is discussed. The part played by the accreting column in the case of strong accretion (approx. equal to 10 19 el cm -3 ) needed for long sustaining of the high level of X-rays from a neutron star-pulsar is studied. There occur the gaps in spectrum at frequencies close to the electron gyro-frequency and its harmonics due to the screening of the hot spot by the opaque gyro-resonant layer located within the accreting column. These gaps ensure the formation of cyclotron lines in absorption irrespective of the presence of such lines in the X-ray spectrum of a polar hot spot. (orig./WL)

Magnetic fluctuations due to thermally excited Alfven waves

International Nuclear Information System (INIS)

Agim, Y.Z.; Prager, S.C.

1990-01-01

Magnetic fluctuations due to the thermally excited MHD waves are investigated using fluid and kinetic models to describe a stable, uniform, compressible plasma in the range above the drift wave frequency and below the ion cyclotron frequency. It is shown that the fluid model with resistivity yields spectral densities which are roughly Lorentzian, exhibit equipartition with no apparent cutoff in wavenumber space and a Bohm-type diffusion coefficient. Under certain conditions, the ensuing transport may be comparable to classical values. For a phenomenological cutoff imposed on the spectrum, the typical fluctuating-to-equilibrium magnetic field ratio is found to be of the order of 10 -10 . Physical mechanisms to obtain decay profiles of the spectra with increasing wavenumber due to dispersion and/or different forms of damping are investigated analytically in a cold fluid approximation and numerically, with a kinetic model. The mode dispersion due to the finite ion-gyrofrequency is identified as the leading effect determining the spectral profile shapes. It is found that the amplitude of fluctuations may be within a factor of the value suggested by the cold plasma model. The results from both models are presented and compared in low- and high-β regimes. 21 refs., 6 figs

Regimes of the magnetized Rayleigh endash Taylor instability

International Nuclear Information System (INIS)

Winske, D.

1996-01-01

Hybrid simulations with kinetic ions and massless fluid electrons are used to investigate the linear and nonlinear behavior of the magnetized Rayleigh endash Taylor instability in slab geometry with the plasma subject to a constant gravity. Three regimes are found, which are determined by the magnitude of the complex frequency ω=ω r +iγ. For |ω| i (Ω i = ion gyrofrequency), one finds the typical behavior of the usual fluid regime, namely the development of open-quote open-quote mushroom-head close-quote close-quote spikes and bubbles in the density and a strongly convoluted boundary between the plasma and magnetic field, where the initial gradient is not relaxed much. A second regime, where |ω|∼0.1Ω i , is characterized by the importance of the Hall term. Linearly, the developing flute modes are more finger-like and tilted along the interface; nonlinearly, clump-like structures form, leading to a significant broadening of the interface. The third regime is characterized by unmagnetized ion behavior, with |ω|∼Ω i . Density clumps, rather than flutes, form in the linear stage, while nonlinearly, longer-wavelength modes that resemble those in fluid regime dominate. Finite Larmor radius stabilization of short-wavelength modes is observed in each regime. copyright 1996 American Institute of Physics

Testing for lightning as a source of radio bursts observed on the nightside of Venus

International Nuclear Information System (INIS)

Sonwalkar, V.S.; Carpenter, D.L.; Strangeway, R.J.

1990-11-01

In certain previous studies of radio burst events recorded by the Pioneer Venus Orbiting Electric Field Detector (OEFD), data were sorted for statistical purposes according to occurrence at filter band frequencies smaller than or greater than typical values of the ambient electron gyrofrequency. The expectation in making this distinction was that the lowest frequency signals, at 100 Hz, were candidates for propagation through the ionosphere to the spacecraft in the whistler mode, and that the higher frequency signals, if of subionospheric origin, would require some different ionospheric penetration mechanism. On the basis of certain assumptions about the homogeneity and horizontal stratification of the Venusian nightside ionosphere, methods were developed for case-by-case testing of the hypothesis that any particular burst event originated in subionospheric lightning. The tests, which are capable of refinement, allow prediction of the resonance cone angle, refractive index, wave dispersion, and wave polarization. The tests have been applied to data from 11 periods along 7 orbits, and are believed to represent an improved way of categorizing OEFD burst data for purposes of investigating source/propagation mechanisms. Four of the five burst events that were not found consistent with the lightning hypothesis involved receptions at multiple OEFD filter band frequencies

Intense microwave pulses II. SPIE Volume 2154

International Nuclear Information System (INIS)

Brandt, H.E.

1994-01-01

The primary purpose of this conference was to present and critically evaluate new and ongoing research on the generation and transmission of intense microwave pulses. Significant progress was reported on high-power, high-current relativistic klystron amplifier research and design. Other work presented at the conference, include research on a high-power relativistic magnetron driven by a high-current linear induction accelerator, derivation of a Pierce-type dispersion relation describing the interaction of an intense relativistic electron beam with a corrugated cylindrical slow-wave structure, experiments on an X-band backward-wave cyclotron maser oscillator, and observation of frequency chirping in a free electron laser amplifier. Other presentations included work on multiwave Cerenkov generator experiments, analysis of resonance characteristics of slow-wave structures in high-power Cerenkov devices, linear analysis and numerical simulation of Doppler-shifted cyclotron harmonics in a cyclotron autoresonance klystron, high-power virtual cathode oscillator theory and experiments, design of a sixth-harmonic gyrofrequency multiplier as a millimeter-wave source, and experiments on dielectric-loaded and multiwave slotted gyro-TWT amplifiers. A review was presented on innovative concepts which employ high-power microwaves in propulsion of space vehicles. Separate abstracts were prepared for 34 papers of this conference

Statistical analysis of the turbulent Reynolds stress and its link to the shear flow generation in a cylindrical laboratory plasma device

International Nuclear Information System (INIS)

Yan, Z.; Yu, J. H.; Holland, C.; Xu, M.; Mueller, S. H.; Tynan, G. R.

2008-01-01

The statistical properties of the turbulent Reynolds stress arising from collisional drift turbulence in a magnetized plasma column are studied and a physical picture of turbulent driven shear flow generation is discussed. The Reynolds stress peaks near the maximal density gradient region, and is governed by the turbulence amplitude and cross-phase between the turbulent radial and azimuthal velocity fields. The amplitude probability distribution function (PDF) of the turbulent Reynolds stress is non-Gaussian and positively skewed at the density gradient maximum. The turbulent ion-saturation (Isat) current PDF shows that the region where the bursty Isat events are born coincides with the positively skewed non-Gaussian Reynolds stress PDF, which suggests that the bursts of particle transport appear to be associated with bursts of momentum transport as well. At the shear layer the density fluctuation radial correlation length has a strong minimum (∼4-6 mm∼0.5C s /Ω ci , where C s is the ion acoustic speed and Ω ci is the ion gyrofrequency), while the azimuthal turbulence correlation length is nearly constant across the shear layer. The results link the behavior of the Reynolds stress, its statistical properties, generation of bursty radially going azimuthal momentum transport events, and the formation of the large-scale shear layer.

Parametric instabilities in an electron beam-plasma system: magnetic field effects

International Nuclear Information System (INIS)

Gell, Y.; Levush, B.; Nakach, R.

1981-09-01

The effects of a magnetic field on the excitation of low-frequency parametric instabilities in a beam-plasma system are considered. The dispersion relation of the three-dimensional beamless configuration, is analytically evaluated for an electrostatic pump wave having a finite wave-vector parallel to the magnetic field. The results of this analysis serve as a guide to the numerical study of the stability of the involved system including the beam. As for the one-dimensional case, one finds that two low-frequency electrostatic instability branches having different growth rates may exist simultaneously. The effects of the magnetic field on these instabilities could be summarized as follows: the small growth rate instability is negligibly small when the electron gyrofrequency is about equal to the pump wave frequency. This instability is magnetic field independent for high enough values of the field. When the plasma electron Debye length is greater than the beam electron Debye length, a large growth rate instability is excited and appears to be weakly dependent on the magnetic field, while the two instability branches are quite sensitive to change of the magnetic field, when the two Debye lengths are equal. Other characteristics of this system are also discussed

Electrostatic lower hybrid waves excited by electromagnetic whistler mode waves scattering from planar magnetic-field-aligned plasma density irregularities

International Nuclear Information System (INIS)

Bell, T.F.; Ngo, H.D.

1990-01-01

Recent satellite observations demonstrate that high amplitude, short wavelength (5 m ≤ λ ≤ 100 m) electrostatic waves are commonly excited by electromagnetic whistler mode waves propagating in regions of the magnetosphere and topside ionosphere where small-scale magnetic-field-aligned plasma density irregularities are thought to exist. A new theoretical model of this phenomenon is presented, based upon passive linear scattering in a cold magnetoplasma. In this model the electrostatic waves are excited by linear mode coupling as the incident electromagnetic whistler mode waves scatter from the magnetic-field-aligned plasma density irregularities. The excited short wavelength waves are quasi-electrostatic whistler mode waves, a type of lower hybrid wave, whose wave normal lies near the whistler mode resonance cone where the wave refractive index becomes very large. The amplitude of the excited electrostatic lower hybrid waves is calculated for a wide range of values of input electromagnetic wave frequency, wave normal direction, electron plasma frequency, gyrofrequency, ion composition, and irregularity scale and density enhancement. Results indicate that high amplitude lower hybrid waves can be excited over a wide range of parameters for irregularity density enhancements as low as 5% whenever the scale of the irregularity is of the same order as the lower hybrid wavelength

Energy transfer between energetic ring current H(+) and O(+) by electromagnetic ion cyclotron waves

Science.gov (United States)

Thorne, Richard M.; Horne, Richard B.

1994-01-01

Electromagnetic ion cyclotron (EMIC) waves in the frequency range below the helium gyrofrequency can be excited in the equatorial region of the outer magnetosphere by cyclotron resonant instability with anisotropic ring current H(+) ions. As the unducted waves propagate to higher latitudes, the wave normal should become highly inclined to the ambient magnetic field. Under such conditions, wave energy can be absorbed by cyclotron resonant interactions with ambient O(+), leading to ion heating perpendicular to the ambient magnetic field. Resonant wave absorption peaks in the vicinity of the bi-ion frequency and the second harmonic of the O(+) gyrofrequrency. This absorption should mainly occur at latitudes between 10 deg and 30 deg along auroral field lines (L is greater than or equal to 7) in the postnoon sector. The concomitant ion heating perpendicular to the ambient magnetic field can contribute to the isotropization and geomagnetic trapping of collapsed O(+) ion conics (or beams) that originate from a low-altitude ionospheric source region. During geomagnetic storms when the O(+) content of the magnetosphere is significantly enhanced, the absorption of EMIC waves should become more efficient, and it may contribute to the observed acceleration of O(+) ions of ionospheric origin up to ring current energies.

Propagation of a TE surface mode in a relativistic electron beam–quantum plasma system

International Nuclear Information System (INIS)

Abdel Aziz, M.

2012-01-01

The dispersion properties of a transverse electric (TE) surface waves propagating along the interface between a magneto-quantum plasma–relativistic beam system and vacuum are studied by using the quantum hydrodynamic model. The general dispersion relations are derived and analyzed in some special cases of interest. Moreover, the effects of density gradients for the beam and plasma on the dispersion properties of surface waves are investigated. The kind of dispersion relations depends strongly on the ambient magnetic field B o via the gyro-frequency ω c , the quantum parameters, and the width of the plasma layer as well as the relativistic factor for the electron beam. It is found that the quantum effects play a crucial role to facilitate the propagation of TE surface waves. -- Highlights: ► Propagation of TE surface waves on bounded magneto-quantum plasma by relativistic beam is studied. ► The quantum plasma consists of transitional layer adjacent to uniform layer. ► Influence of quantum effects on the propagation of TE surface waves are taken into account. ► Effects of homogeneity and inhomogeneity for beam on TE surface waves are considered. ► It is found that quantum effects facilitate the propagation of TE surface modes.

Correlations of auroral kilometric radiation with Birkeland currents

International Nuclear Information System (INIS)

Saflekos, N.A.; Carovillano, R.L.; Sheehan, R.E.

1983-01-01

This chapter examines auroral kilometric radiation (AKR) in relation to the strength of field-aligned currents (FAC), which represent an energy source stored in the form of magnetic field energy density in the neighborhood of the earth. An attempt is made to find a direct relationship between AKR power flux and optical auroral emissions. Topics considered include correlated Hawkeye and Triad satellite observations and correlated AKR and optical emissions. It is indicated that AKR is electromagnetic radiation in the frequency range of 50 to 500 kHz; AKR is generated at frequencies above the electron plasma frequency and below the electron gyrofrequency; AKR propagates in the Right Hand Extraordinary mode; and AKR may show fine structure in frequency. The principal findings include: distributions of AKR intensity with increasing auroral activity show that although quiet and disturbed auroras are generally accompanied by weak and intense AKR, the moderate auroras are associated with a broad range of AKR power; distributions of AKR intensity with increasing auroral electrojet (AE) index during the expansion phase of a polar magnetic substorm show near maximum levels of AKR power emission; and the maximum AKR power increases with increasing auroral activity and with increasing Birkeland current strength

Modelling substorm chorus events in terms of dispersive azimuthal drift

Directory of Open Access Journals (Sweden)

A. B. Collier

2004-12-01

Full Text Available The Substorm Chorus Event (SCE is a radio phenomenon observed on the ground after the onset of the substorm expansion phase. It consists of a band of VLF chorus with rising upper and lower cutoff frequencies. These emissions are thought to result from Doppler-shifted cyclotron resonance between whistler mode waves and energetic electrons which drift into a ground station's field of view from an injection site around midnight. The increasing frequency of the emission envelope has been attributed to the combined effects of energy dispersion due to gradient and curvature drifts, and the modification of resonance conditions and variation of the half-gyrofrequency cutoff resulting from the radial component of the ExB drift. A model is presented which accounts for the observed features of the SCE in terms of the growth rate of whistler mode waves due to anisotropy in the electron distribution. This model provides an explanation for the increasing frequency of the SCE lower cutoff, as well as reproducing the general frequency-time signature of the event. In addition, the results place some restrictions on the injected particle source distribution which might lead to a SCE. Key words. Space plasma physics (Wave-particle interaction – Magnetospheric physics (Plasma waves and instabilities; Storms and substorms

Wave-Particle Interactions Associated with Nongyrotropic Distribution Functions: A Hybrid Simulation Study

Science.gov (United States)

Convery, P. D.; Schriver, D.; Ashour-Abdalla, M.; Richard, R. L.

2002-01-01

Nongyrotropic plasma distribution functions can be formed in regions of space where guiding center motion breaks down as a result of strongly curved and weak ambient magnetic fields. Such are the conditions near the current sheet in the Earth's middle and distant magnetotail, where observations of nongyrotropic ion distributions have been made. Here a systematic parameter study of nongyrotropic proton distributions using electromagnetic hybrid simulations is made. We model the observed nongyrotropic distributions by removing a number of arc length segments from a cold ring distribution and find significant differences with the results of simulations that initially have a gyrotropic ring distribution. Model nongyrotropic distributions with initially small perpendicular thermalization produce growing fluctuations that diffuse the ions into a stable Maxwellian-like distribution within a few proton gyro periods. The growing waves produced by nongyrotropic distributions are similar to the electromagnetic proton cyclotron waves produced by a gyrotropic proton ring distribution in that they propagate parallel to the background magnetic field and occur at frequencies on the order of the proton gyrofrequency, The maximum energy of the fluctuating magnetic field increases as the initial proton distribution is made more nongyrotropic, that is, more highly bunched in perpendicular velocity space. This increase can be as much as twice the energy produced in the gyrotropic case.

Controlling Charge and Current Neutralization of an Ion Beam Pulse in a Background Plasma by Application of a Solenoidal Magnetic Field I: Weak Magnetic Field Limit

Energy Technology Data Exchange (ETDEWEB)

Kaganovich, I. D., Startsev, E. A., Sefkow, A. B., Davidson, R. C.

2008-10-10

Propagation of an intense charged particle beam pulse through a background plasma is a common problem in astrophysics and plasma applications. The plasma can effectively neutralize the charge and current of the beam pulse, and thus provides a convenient medium for beam transport. The application of a small solenoidal magnetic field can drastically change the self-magnetic and self- electric fields of the beam pulse, thus allowing effective control of the beam transport through the background plasma. An analytic model is developed to describe the self-magnetic field of a finite- length ion beam pulse propagating in a cold background plasma in a solenoidal magnetic field. The analytic studies show that the solenoidal magnetic field starts to infuence the self-electric and self-magnetic fields when ωce > ωpeβb, where ωce = eβ/mec is the electron gyrofrequency, ωpe is the electron plasma frequency, and βb = Vb/c is the ion beam velocity relative to the speed of light. This condition typically holds for relatively small magnetic fields (about 100G). Analytical formulas are derived for the effective radial force acting on the beam ions, which can be used to minimize beam pinching. The results of analytic theory have been verified by comparison with the simulation results obtained from two particle-in-cell codes, which show good agreement.

Controlling Charge and Current Neutralization of an Ion Beam Pulse in a Background Plasma by Application of a Solenoidal Magnetic Field I: Weak Magnetic Field Limit

International Nuclear Information System (INIS)

Kaganovich, I. D.; Startsev, E. A.; Sefkow, A. B.; Davidson, R. C.

2008-01-01

Propagation of an intense charged particle beam pulse through a background plasma is a common problem in astrophysics and plasma applications. The plasma can effectively neutralize the charge and current of the beam pulse, and thus provides a convenient medium for beam transport. The application of a small solenoidal magnetic field can drastically change the self-magnetic and self- electric fields of the beam pulse, thus allowing effective control of the beam transport through the background plasma. An analytic model is developed to describe the self-magnetic field of a finite-length ion beam pulse propagating in a cold background plasma in a solenoidal magnetic field. The analytic studies show that the solenoidal magnetic field starts to influence the self-electric and self-magnetic fields when ω ce ∼> ω pe β b , where ω ce = eB/m e c is the electron gyrofrequency, ω pe is the electron plasma frequency, and β b = V b /c is the ion beam velocity relative to the speed of light. This condition typically holds for relatively small magnetic fields (about 100G). Analytical formulas are derived for the effective radial force acting on the beam ions, which can be used to minimize beam pinching. The results of analytic theory have been verified by comparison with the simulation results obtained from two particle-in-cell codes, which show good agreement

Simulation of D and E region high-power microwave heating with HF ionospheric modification experiments

International Nuclear Information System (INIS)

Meltz, G.; Rush, C.M.; Violette, E.J.

1981-01-01

The microwave power beam from a Solar Power Satellite (SPS) is sufficiently intense to cause large changes in the properties of the lower ionosphere by ohmic heating of the plasma. Power is absorbed from the beam at a rate that is proportional to the ratio of the flux s and the square of an effective frequency f/sub e/. Throughout most of the lower ionosphere f/sub e/ = f -+ f/sub L/, where f is the wave frequency and f/sub L is a reduced electron gyrofrequency. It follows that SPS equivalent heating can be simulated at much lower power fluxes with HF radio waves. A detailed examination of the frequency scaling, based on fluid and kinetic theory estimates of the change in electron temperature and density, shows that the high-power HF facility at Platteville, CO, can simulate or exceed the ohmic effects of the SPS beam up to 90 km. This paper describes the results of a series of 5.2 and 9.9 MHz underdense heating experiments undertaken to study the effect of high-power microwaves on the lower ionosphere. A pulsed ionosonde probe, located nearly below the most intense portion of the high-power beam, was used to observe the changes in the D and lower E region. Both phase and amplitude measurements were recorded during CW and intermittent heating

Stability analysis and reconstruction of wave distribution functions in warm plasmas

International Nuclear Information System (INIS)

Oscarsson, T.E.

1989-05-01

The purpose of this thesis is first to describe stability analysis and reconstruction of the wave distribution function (WDF) separately, and then to show how the two approaches can be combined in an investigation of satellite data. To demonstrate the type of stability investigation that is often used in space physics we study instabilities below the local proton gyrofrequency which are caused by anisotropic proton distributions. Arbitrary angles between the wavevector and the background magnetic field are considered, and effects of warm plasma on the wave propagation properties are included. We also comment briefly given on an often-used scheme for classifying instabilities. In our discussion on WDF analysis we develop a completely new and general method for reconstructing the WDF. Our scheme can be used to reconstruct the distribution function of waves in warm as well as cold plasma. Doppler effects introduced by satellite motion are included, and the reconstructions can be performed over a broad frequency range simultaneously. The applicability of our new WDF reconstruction method is studied in model problems and in an application to observations made by the Swedish satellite Viking. In the application to Viking data we combine stability and WDF analyses in a unique way that promises to become an important tool in future studies of wave-particle interactions in space plasmas. (author)

Improved planar radio frequency inductively coupled plasma configuration in plasma immersion ion implantation

International Nuclear Information System (INIS)

Tang, D.L.; Fu, R.K.Y.; Tian, X.B.; Chu, P.K.

2003-01-01

Plasmas with higher density and better uniformity are produced using an improved planar radio frequency (rf) inductively coupled plasma configuration in plasma immersion ion implantation (PIII). An axial magnetic field is produced by external electromagnetic coils outside the discharge chamber. The rf power can be effectively absorbed by the plasma in the vicinity of the electron gyrofrequency due to the enhanced resonant absorption of electromagnetic waves in the whistler wave range, which can propagate nearly along the magnetic field lines thus greatly increases the plasma density. The plasma is confined by a longitudinal multipolar cusp magnetic field made of permanent magnets outside the process chamber. It can improve the plasma uniformity without significantly affecting the ion density. The plasma density can be increased from 3x10 9 to 1x10 10 cm -3 employing an axial magnetic field of several Gauss at 1000 W rf power and 5x10 -4 Torr gas pressure. The nonuniformity of the plasma density is less than 10% and can be achieved in a process chamber with a diameter of 600 mm. Since the plasma generation and process chambers are separate, plasma extinction due to the plasma sheath touching the chamber wall in high-energy PIII can be avoided. Hence, low-pressure, high-energy, and high-uniformity ion implantation can be accomplished using this setup

Modelling substorm chorus events in terms of dispersive azimuthal drift

Directory of Open Access Journals (Sweden)

A. B. Collier

2004-12-01

Full Text Available The Substorm Chorus Event (SCE is a radio phenomenon observed on the ground after the onset of the substorm expansion phase. It consists of a band of VLF chorus with rising upper and lower cutoff frequencies. These emissions are thought to result from Doppler-shifted cyclotron resonance between whistler mode waves and energetic electrons which drift into a ground station's field of view from an injection site around midnight. The increasing frequency of the emission envelope has been attributed to the combined effects of energy dispersion due to gradient and curvature drifts, and the modification of resonance conditions and variation of the half-gyrofrequency cutoff resulting from the radial component of the ExB drift.

A model is presented which accounts for the observed features of the SCE in terms of the growth rate of whistler mode waves due to anisotropy in the electron distribution. This model provides an explanation for the increasing frequency of the SCE lower cutoff, as well as reproducing the general frequency-time signature of the event. In addition, the results place some restrictions on the injected particle source distribution which might lead to a SCE.

Key words. Space plasma physics (Wave-particle interaction – Magnetospheric physics (Plasma waves and instabilities; Storms and substorms

Solenoidal magnetic field influences the beam neutralization by a background plasma

International Nuclear Information System (INIS)

Kaganovich, I.

2004-01-01

An analytical electron fluid model has been developed to describe the plasma response to a propagating ion beam. The model predicts very good charge neutralization during quasi-steady-state propagation, provided the beam pulse duration is much longer than the electron plasma period. In the opposite limit, the beam pulse excites large-amplitude plasma waves. Figure 1 shows the influence of a solenoidal magnetic field on charge and current neutralization. Analytical studies show that the solenoidal magnetic field begins to influence the radial electron motion when ω ce > βω pe . Here, ω ce is the electron gyrofrequency, ω pe is the electron plasma frequency, and β = V b /c is the ion beam velocity. If a solenoidal magnetic field is not applied, plasma waves do not propagate. In contrast, in the presence of a solenoidal magnetic field, whistler waves propagate ahead of the beam and can perturb the plasma ahead of the beam pulse. In the limit ω ce >> βω pe , the electron current completely neutralizes the ion beam current and the beam self magnetic field greatly diminishes. Application of an external solenoidal magnetic field clearly makes the collective processes of ion beam-plasma interactions rich in physics content. Many results of the PIC simulations remain to be explained by analytical theory. Four new papers have been published or submitted describing plasma neutralization of an intense ion beam pulse

Low-noise electromagnetic δf particle-in-cell simulation of electron Bernstein waves

International Nuclear Information System (INIS)

Xiang Nong; Cary, John R.; Barnes, Daniel C.; Carlsson, John

2006-01-01

The conversion of the extraordinary (X) mode to an electron Bernstein wave (EBW) is one way to get rf energy into an overdense plasma. Analysis of this is complex, as the EBW is a fully kinetic wave, and so its linear propagation is described by an intractable integro-differential equation. Nonlinear effects cannot be calculated within this rubric at all. Full particle-in-cell (PIC) simulations cannot be used for these analyses, as the noise levels for reasonable simulation parameters are much greater than the typical rf amplitudes. It is shown that the delta-f computations are effective for this analysis. In particular, the accuracy of those computations has been verified by comparison with full PIC, cold plasma theory, and small gyroradius theory. This computational method is then used to analyze mode conversion in different frequency regimes. In particular, reasonable agreement with the theoretical predictions of Ram and Schultz [Phys. Plasmas 7, 4084 (2000)] in the linear regime is found, where 100% X-B mode conversion has been obtained when the driving frequency is less than twice the electron gyrofrequency. The results show that cold-plasma theory well predicts the mode conversion efficiency, as is consistent with the phase-space picture of mode conversion. From this it can be shown that nearly 100% X-B mode conversion cannot be obtained when the frequency is higher than the electron second harmonic cyclotron frequency

Observations of EMIC Waves in the Exterior Cusp Region and in the Nearby Magnetosheath

Science.gov (United States)

Grison, B.; Escoubet, C. P.; Santolik, O.; Lavraud, B.; Cornilleau-Wehrlin, N.

2014-12-01

In the early years (2000-2004) of the mission, Cluster crossed the most distant part of the polar cusps. On 05/01/2002, Cluster enters the distant cusp region on the duskside of the southern hemisphere (inbound). The spacecraft are successively crossing the magnetopause between 19:50 UT (SC4) and 20:15 UT (SC3). The interplanetary conditions during the crossing were stable with a dominant negative By. The magnetometer (FGM) data indicates that the entry into the cusp takes place in a region where the magnetic field lines in the magnetosheath are anti-parallel with the field lines in the magnetosphere. Despite this clear picture, the global encounter is rather complex: one can notice partial magnetopause crossings, magnetic null points, and intense monochromatic waves on both sides of the magnetopause.We investigate electromagnetic ion cyclotron (EMIC) waves observed in the cusp and in the nearby magnetosheath, just before the magnetopause crossing by the spacecraft. Left-handed monochromatic waves observed in the cusp display different duration and frequency (below and above the local proton gyrofrequency) on each spacecraft. Both the Poynting flux of these emissions and the simultaneously recorded ion flows propagate in the same direction - toward the Earth. The wavenumber are determined in two ways: considering the Doppler shift and from direct measurements of the refractive index. We analyze these wave parameters and the local plasma conditions to explain the wave generation process on each side of the magnetopause.

Wave number determination of Pc 1-2 mantle waves considering He++ ions: A Cluster study

Science.gov (United States)

Grison, B.; Escoubet, C. P.; Santolík, O.; Cornilleau-Wehrlin, N.; Khotyaintsev, Y.

2014-09-01

The present case study concerns narrowband electromagnetic emission detected in the distant cusp region simultaneously with upgoing plasma flows. The wave properties match the usual properties of the Pc 1-2 mantle waves: small angle between the wave vector and the magnetic field line, left-hand polarization, and propagation toward the ionosphere. We report here the first direct wave vector measurement of these waves (about 1.2 × 10- 2 rad/km) through multi spacecraft analysis using the three magnetic components and, at the same time, through single spacecraft analysis based on the refractive index analysis using the three magnetic components and two electric components. The refractive index analysis offers a simple way to estimate wave numbers in this frequency range. Numerical calculations are performed under the observed plasma conditions. The obtained results show that the ion distribution functions are unstable to ion cyclotron instability at the observed wave vector value, due to the large ion temperature anisotropy. We thus show that these electromagnetic ion cyclotron (EMIC) waves are amplified in the distant cusp region. The Poynting flux of the waves is counterstreaming with respect to the plasma flow. This sense of propagation is consistent with the time necessary to amplify the emissions to the observed level. We point out the role of the wave damping at the He++ gyrofrequency to explain that such waves cannot be observed from the ground at the cusp foot print location.

Creating space plasma from the ground

Science.gov (United States)

Carlson, H. C.; Djuth, F. T.; Zhang, L. D.

2017-01-01

We have performed an experiment to compare as directly as realizable the ionization production rate by HF radio wave energy versus by solar EUV. We take advantage of the commonality that ionization production by both ground-based high-power HF radio waves and by solar EUV is driven by primary and secondary suprathermal electrons near and above 20 eV. Incoherent scatter radar (ISR) plasma-line amplitudes are used as a measure of suprathermal electron fluxes for ISR wavelengths near those for 430 MHz and are indeed a clean measure of such for those fluxes sufficiently weak to have negligible self-damping. We present data from an HF heating experiment on November 2015 at Arecibo, which even more directly confirm the only prior midlatitude estimate, of order 10% efficiency for conversion of HF energy to ionospheric ionization. We note the theoretical maximum possible is 1/3, while 1% or less reduces the question to near practical irrelevance. Our measurements explicitly confirm the prediction that radio-frequency production of artificial ionospheres can be practicable, even at midlatitudes. Furthermore, that this midlatitude efficiency is comparable to efficiencies measured at high latitudes (which include enhancements unique to high latitudes including magnetic zenith effect, gyrofrequency multiples, and double resonances) requires reexamination of current theoretical thinking about soft-electron acceleration processes in weakly magnetized plasmas. The implications are that electron acceleration by any of a variety of processes may be a fundamental underpinning to energy redistribution in space plasmas.

Generation of auroral kilometric radiation

International Nuclear Information System (INIS)

Green, J.L.

1979-01-01

Simultaneous observations between the Hawkeye spacecraft in the AKR emission cone and the low altitude polar orbiting spacecraft Triad and AE-D reveal that auroral kilometric radiation (AKR) is correlated with a variety of auroral particle precipitation in the evening to midnight local time sector. It is found that as the AKR intensity increases so does the integrated current sheet intensity of auroral zone field aligned currents observed by Triad of 257 simultaneous observations. Statistically, the linear correlation coefficient between the log of the AKR power flux and the log of the current sheet intensity is 0.57. Auroral kilometric radiation observations from Hawkeye during low altitude (2.0 to 2.5 R/sub E/) auroral zone passes reveal that intense AKR has a low frequency cutoff near the local electron gyrofrequency (f/sub g/ - ) with maximum electric field strengths as large as 12 mV/m. The large electric fields observed near f/sub g/ - are consistent with high altitude observations of AKR using a simple 1/R 2 scaling indicating that the kilometric radiation in or near the average source region is almost completely electromagnetic. The results presented in this study indicate that kilometric radiation is generated by inverted-V electron distribution functions in a direct coupling mechanism between particle energy and R-X mode electromagnetic waves in the region of the auroral zone where f/sub g/ - >> f/sub p/ -

EMIC triggered chorus emissions in Cluster data

Science.gov (United States)

Grison, B.; SantolíK, O.; Cornilleau-Wehrlin, N.; Masson, A.; Engebretson, M. J.; Pickett, J. S.; Omura, Y.; Robert, P.; Nomura, R.

2013-03-01

Electromagnetic ion cyclotron (EMIC) triggered chorus emissions have recently been a subject of several experimental, theoretical and simulation case studies, noting their similarities with whistler-mode chorus. We perform a survey of 8 years of Cluster data in order to increase the database of EMIC triggered emissions. The results of this is that EMIC triggered emissions have been unambiguously observed for only three different days. These three events are studied in detail. All cases have been observed at the plasmapause between 22 and 24 magnetic local time (MLT) and between - 15° and 15° magnetic latitude (λm). Triggered emissions are also observed for the first time below the local He+ gyrofrequency (fHe+). The number of events is too low to produce statistical results, nevertheless we point out a variety of common properties of those waves. The rising tones have a high level of coherence and the waves propagate away from the equatorial region. The propagation angle and degree of polarization are related to the distance from the equator, whereas the slope and the frequency extent vary from one event to the other. From the various spacecraft separations, we determine that the triggering process is a localized phenomenon in space and time. However, we are unable to determine the occurrence rates of these waves. Small frequency extent rising tones are more common than large ones. The newly reported EMIC triggered events are generally observed during periods of large AE index values and in time periods close to solar maximum.

Observations of EMIC Triggered Emissions off the Magnetic Equatorial Plane

Science.gov (United States)

Grison, B.; Breuillard, H.; Santolik, O.; Cornilleau-Wehrlin, N.

2016-12-01

On 19/08/2005 Cluster spacecraft had their perigee close to the dayside of the Earth magnetic equatorial plane, at about 14 hours Magnetic Local Time. The spacecraft crossed the equator from the southern hemisphere toward the northern hemisphere. In the Southern hemisphere, at about -23° magnetic latitude (MLAT) and at distance of 5.25 Earth Radii from Earth, Cluster 3 observes an EMIC triggered emission between the He+ and the proton local gyrofrequencies. The magnetic waveform (STAFF instrument data) is transformed into the Fourier space for a study based on single value decomposition (SVD) analysis. The emission lasts about 30s. The emission frequency rises from 1Hz up to 1.9Hz. The emission polarization is left-hand, its coherence value is high and the propagation angle is field aligned (lower than 30º). The Poynting flux orientation could not be established. Based on previous study results, these properties are indicative of an observation in vicinity of the source region of the triggered emission. From our knowledge this is the first time that EMIC triggered emission are observed off the magnetic equator. In order to identify the source region we study two possibilities: a source region at higher latitudes than the observations (and particles orbiting in "Shabansky" orbits) and a source region close to the magnetic equatorial plane, as reported in previous studies. We propose to identify the source region from ray tracing analysis and to compare the observed propagation angle in several frequency ranges to the ray tracing results.

Radio-wavelength observations of magnetic fields on active dwarf-M, RS CVN and magnetic stars

Energy Technology Data Exchange (ETDEWEB)

Lang, K.R.

1986-01-01

The dwarf M stars YZ Canis Minoris and AD Leonis exhibit narrow band, slowly varying (hours) microwave emission that cannot be explained by conventional thermal radiation mechanisms. The dwarf M stars AD Leonis and Wolf 424 emit rapid spikes whose high brightness temperatures similarly require a nonthermal radiation process which could result from coherent mechanisms such as an electron-cyclotron maser or coherent-plasma radiation. If the electron-cyclotron maser emits at the second or third harmonic of the gyrofrequency, the coronal magnetic field strength H = 250 or 167 G and constraints on the plasma frequency imply an electron density of 6 x 10/sup 9//cm/sup 3/. Coherent-plasma radiation requires similar values of electron density but much weaker magnetic fields. Radio spikes from AD Leonis and Wolf 424 have rise times tau/sub R/ < 5 ms, indicating a linear size of L < 1.5 x 10/sup 8/ cm, or less than 0.005 of the stellar radius. Although Ap magnetic stars have strong dipole magnetic fields, they exhibit no detectable gyroresonant radiation, suggesting that these stars do not have hot, dense coronae. The binary RS CVn star UX Arietis exhibits variable emission at 6 cm wavelength on time scales ranging from 30 s to more than one hour. The shortest variation implies a linear size much less than that of the halo observed by VLBI techniques, and most probably sizes smaller than those of the component stars. The observed variations might be due to absorption by a thermal plasma located between the stars.

On nonstationarity and rippling of the quasiperpendicular zone of the Earth bow shock: Cluster observations

Directory of Open Access Journals (Sweden)

V. V. Lobzin

2008-09-01

Full Text Available A new method for remote sensing of the quasiperpendicular part of the bow shock surface is presented. The method is based on analysis of high frequency electric field fluctuations corresponding to Langmuir, upshifted, and downshifted oscillations in the electron foreshock. Langmuir waves usually have maximum intensity at the upstream boundary of this region. All these waves are generated by energetic electrons accelerated by quasiperpendicular zone of the shock front. Nonstationary behavior of the shock, in particular due to rippling, should result in modulation of energetic electron fluxes, thereby giving rise to variations of Langmuir waves intensity. For upshifted and downshifted oscillations, the variations of both intensity and central frequency can be observed. For the present study, WHISPER measurements of electric field spectra obtained aboard Cluster spacecraft are used to choose 48 crossings of the electron foreshock boundary with dominating Langmuir waves and to perform for the first time a statistical analysis of nonstationary behavior of quasiperpendicular zone of the Earth's bow shock. Analysis of hidden periodicities in plasma wave energy reveals shock front nonstationarity in the frequency range 0.33 fBigyrofrequency upstream of the shock, and shows that the probability to observe such a nonstationarity increases with Mach number. The profiles observed aboard different spacecraft and the dominating frequencies of the periodicities are usually different. Hence nonstationarity and/or rippling seem to be rather irregular both in space and time rather than resembling a quasiregular wave propagating on the shock surface.

Slide-away distributions and relevant collective modes in high-temperature plasmas

International Nuclear Information System (INIS)

Coppi, B.; Pegoraro, F.; Pozzoli, R.; Rewoldt, G.

1976-01-01

The evolution of the electron distribution function, when an electric field that is not too small in comparison with the critical electron runaway field is applied along the confining magnetic field of a high temperature plasma, is analysed. In the regimes considered, a finite fraction of the electron population has magnetically trapped orbits, and is not appreciably affected by the applied electric field, while the distribution of circulating electrons tends to ''slide away'' as a whole. Then the Spitzer-Haerm model for the current-carrying electron distribution is inadequate, and the role that collective modes, in particular current-driven microinstabilities, and collisions can play in producing a stationary electron distribution is analysed. Modes at the ion plasma frequency, ωsub(pi), that are driven by the positive slope of the current-carrying electron distribution, can be excited, when the average electron drift velocity is a finite fraction of the electron thermal velocity, and transfer transverse energy to the main body of the electron distribution. These features are consistent with the experimental observations performed on the Alcator device. Modes at the ''reduced'' electron plasma frequency (ksub(parallel)/k)ωsub(pe) can also be excited both in connection with the modes at wsub(pi) and independently. Modes at the electron gyrofrequency Ωsub(e) associated with the loss-cone feature that the electron distribution tends to develop are considered, among others, as a factor for the strongly enhanced electron cyclotron emission experimentally observed in regimes where non-thermal electron distributions have been realized. (author)

Off-equatorial current-driven instabilities ahead of approaching dipolarization fronts

Science.gov (United States)

Zhang, Xu; Angelopoulos, V.; Pritchett, P. L.; Liu, Jiang

2017-05-01

Recent kinetic simulations have revealed that electromagnetic instabilities near the ion gyrofrequency and slightly away from the equatorial plane can be driven by a current parallel to the magnetic field prior to the arrival of dipolarization fronts. Such instabilities are important because of their potential contribution to global electromagnetic energy conversion near dipolarization fronts. Of the several instabilities that may be consistent with such waves, the most notable are the current-driven electromagnetic ion cyclotron instability and the current-driven kink-like instability. To confirm the existence and characteristics of these instabilities, we used observations by two Time History of Events and Macroscale Interactions during Substorms satellites, one near the neutral sheet observing dipolarization fronts and the other at the boundary layer observing precursor waves and currents. We found that such instabilities with monochromatic signatures are rare, but one of the few cases was selected for further study. Two different instabilities, one at about 0.3 Hz and the other at a much lower frequency, 0.02 Hz, were seen in the data from the off-equatorial spacecraft. A parallel current attributed to an electron beam coexisted with the waves. Our instability analysis attributes the higher-frequency instability to a current-driven ion cyclotron instability and the lower frequency instability to a kink-like instability. The current-driven kink-like instability we observed is consistent with the instabilities observed in the simulation. We suggest that the currents needed to excite these low-frequency instabilities are so intense that the associated electron beams are easily thermalized and hence difficult to observe.

Generation of auroral kilometric radiation in upper hybrid wave-lower hybrid soliton interaction

International Nuclear Information System (INIS)

Pottelette, R.; Dubouloz, N.; Treumann, R.A.

1992-01-01

Sporadic bursts of auroral kilometric radiation (AKR) associated with strong bursty electrostatic turbulence in the vicinity of the lower hybrid frequency have been frequently recorded in the AKR source region by the Viking satellite. The variation time scale of these emissions is typically 1 s, long enough for lower hybrid waves to grow to amplitudes of several hundred millivolts per meter and to evolve nonlinearly into solitons. On the basis on these observations it is suggested that formation of lower hybrid solitons may play a role in the generation of AKR. A theoretical model is proposed which is based on the direct acceleration of electrons in the combined lower hybrid soliton and upper hybrid wave fields. The solitons act as sporadic, localized antennas allowing for efficient conversions of the electrostatic energy stored in upper hybrid waves into electromagnetic radiation at a frequency above the X mode cutoff. Excitation of lower hybrid waves is due to the presence of energetic electron beams in the auroral zone found to be associated with steep plasma density gradients. Upper hybrid waves can be excited by a population of energetic electrons with loss cone distributions. The power of the electromagnetic radiation obtained is only noticeable in regions where the plasma frequency is less than the electron gyrofrequency. The theory predicts spectral power densities of the order of 10 -11 to 10 -9 W m -2 Hz -1 in the source region, in good agreement with the Viking observations. The sporadic nature of the radiation derives from lower hybrid soliton collapses which occur on ∼1-s time scales

Propagation of EMIC triggered emissions toward the magnetic equatorial plane

Science.gov (United States)

Grison, B.; Santolik, O.; Pickett, J. S.; Omura, Y.; Engebretson, M. J.; Dandouras, I. S.; Masson, A.; Decreau, P.; Cornilleau-Wehrlin, N.

2011-12-01

EMIC triggered emissions are observed close to the equatorial plane of the magnetosphere at locations where EMIC waves are commonly observed: close to the plasmapause region and in the dayside magnetosphere close to the magnetopause. Their overall characteristics (frequency with time dispersion, generation mechanism) make those waves the EMIC analogue of rising frequency whistler-mode chorus emissions. In our observations the Poynting flux of these emissions is usually clearly arriving from the equatorial region direction, especially when observations take place at more than 5 degrees of magnetic latitude. Simulations have also confirmed that the conditions of generation by interaction with energetic ions are at a maximum at the magnetic equator (lowest value of the background magnetic field along the field line). However in the Cluster case study presented here the Poynting flux of EMIC triggered emissions is propagating toward the equatorial region. The large angle between the wave vector and the background magnetic field is also unusual for this kind of emission. The rising tone starts just above half of the He+ gyrofrequency (Fhe+) and it disappears close to Fhe+. At the time of detection, the spacecraft magnetic latitude is larger than 10 degrees and L shell is about 4. The propagation sense of the emissions has been established using two independent methods: 1) sense of the parallel component of the Poynting flux for a single spacecraft and 2) timing of the emission detections at each of the four Cluster spacecraft which were in a relatively close configuration. We propose here to discuss this unexpected result considering a reflection of this emission at higher latitude.

Adiabatic motion of charged dust grains in rotating magnetospheres

International Nuclear Information System (INIS)

Northrop, T.G.; Hill, J.R.

1983-01-01

Dust grains in the ring systems and rapidly rotating magnetospheres of the outer planets such as Jupiter and Saturn may be sufficiently charged that the magnetic and electric forces on them are comparable with the gravitational force. The adiabatic theory of charged particle motion has previously been applied to electrons and atomic size particles. But it is also applicable to these charged dust grains in the micrometer and smaller size range. We derive here the guiding center equation of motion, drift velocity, and parallel equation of motion for these grains in a rotating magnetosphere. The effects of periodic grain charge-discharge have not been treated previously and have been included in this analysis. Grain charge is affected by the surrounding plasma properties and by the grain plasma velocity (among other factors), both of which may vary over the gyrocircle. The resulting charge-discharge process at the gyrofrequency destroys the invariance of the magnetic moment and causes a grain to move radially. The magnetic moment may increase or decrease, depending on the gyrophase of the charge variation. If it decreases, the motion is always toward synchronous radius for an equatorial grain. But the orbit becomes circular before the grain reaches synchronous radius, a conclusion that follows from an exact constant of the motion. This circularization can be viewed as a consequence of the gradual reduction in the magnetic moment. This circularization also suggests that dust grains leaving Io could not reach the region of the Jovian ring, but several effects could change that conclusion. Excellent qualitative and quantitative agreement is obtained between adiabatic theory and detailed numerical orbit integrations

Magnetized Langmuir wave packets excited by a strong beam-plasma interaction

International Nuclear Information System (INIS)

Pelletier, G.; Sol, H.; Asseo, E.

1988-01-01

The physics of beam-plasma interaction, which has been investigated for a long time mostly in relation with solar bursts, is now more widely invoked in various astrophysical contexts such as pulsars, active galactic nuclei, close binaries, cataclysmic variables, γ bursters, and so on. In these situations the interaction is more likely in the spirit of strong Langmuir turbulence rather than in the spirit of quasilinear theory. Many investigations have been done for two opposite extremes, namely, in very weak and in very strong magnetic fields. Very few properties of the strong Langmuir turbulence are known in the most usual astrophysical situation where the magnetic field plays a significant role but is not strong enough to force the electrons into one-dimensional motion. For this case, we analyze the dynamics of Langmuir wave packets and provide new results about the stability of the solitons against transverse perturbations. It turns out that both the averaged Lagrangian method and the adiabatic perturbation method derived from the inverse scattering transform give exactly the same results (which is not obvious in soliton perturbation theory). In particular, they predict the stability of the solitons as long as the electron gyrofrequency is greater than the plasma frequency (strong magnetic field) and their instability against transverse self-modulation in the opposite case (weak magnetic field); moreover, they allow one to deduce the self-similar collapsing oblate cavitons in the latter case. The laws governing the collapse of the wave packets determine the relaxation of the beam in the surrounding medium and we derive a useful formula giving the power loss of the beam. We outline the astrophysical consequences of this investigation

On nonstationarity and rippling of the quasiperpendicular zone of the Earth bow shock: Cluster observations

Directory of Open Access Journals (Sweden)

V. V. Lobzin

2008-09-01

Full Text Available A new method for remote sensing of the quasiperpendicular part of the bow shock surface is presented. The method is based on analysis of high frequency electric field fluctuations corresponding to Langmuir, upshifted, and downshifted oscillations in the electron foreshock. Langmuir waves usually have maximum intensity at the upstream boundary of this region. All these waves are generated by energetic electrons accelerated by quasiperpendicular zone of the shock front. Nonstationary behavior of the shock, in particular due to rippling, should result in modulation of energetic electron fluxes, thereby giving rise to variations of Langmuir waves intensity. For upshifted and downshifted oscillations, the variations of both intensity and central frequency can be observed. For the present study, WHISPER measurements of electric field spectra obtained aboard Cluster spacecraft are used to choose 48 crossings of the electron foreshock boundary with dominating Langmuir waves and to perform for the first time a statistical analysis of nonstationary behavior of quasiperpendicular zone of the Earth's bow shock. Analysis of hidden periodicities in plasma wave energy reveals shock front nonstationarity in the frequency range 0.33 f_BiBi, where f_Bi is the proton gyrofrequency upstream of the shock, and shows that the probability to observe such a nonstationarity increases with Mach number. The profiles observed aboard different spacecraft and the dominating frequencies of the periodicities are usually different. Hence nonstationarity and/or rippling seem to be rather irregular both in space and time rather than resembling a quasiregular wave propagating on the shock surface.

Structure and properties of the subsolar magnetopause for northward IMF: ISEE observations

International Nuclear Information System (INIS)

Song, P.; Russell, C.T.; Elphic, R.C.; Gosling, J.T.; Cattell, C.A.

1990-01-01

Detailed magnetopause structure and properties for the magnetic field, electric field and plasma are examined for an ISEE 1 magnetopause crossing which occurred near the subsolar point when the interplanetary magnetic field (IMF) was strongly northward. Because the crossing is slow, the spatial variations in the plasma are clearly resolved. This example illustrates the nature of the steady state interface of two magnetized thermal plasma populations with parallel fields and can serve as a guide to theoretical modeling and simulations. The authors have found that the magnetopause is composed of three layers, a sheath transition layer, an outer boundary layer and an inner boundary layer. In the sheath transition layer, there is a gradual density decrease without a change in temperature. The transition layer occurs totally within the magnetosheath plasma. The outer boundary layer and the inner boundary layer are dominated by magnetosheath and magnetospheric particles, respectively. In each of the boundary layers, the plasma can be interpreted as simple mixtures of the magnetosheath and magnetospheric populations. No significant heating or cooling is seen across the magnetopause during this crossing. The plasma within each of these layers is quite uniform and their boundaries are sharp, suggesting that there is very little diffusion present. The sharp boundaries between the transition layer, the boundary layers and the magnetosphere are all thinner than an ion gyroradius. Transverse waves with right hand or linear polarization near the ion gyrofrequency are observed in the transition layer. These appear to be generated in the transition layer and to be a common feature of this layer when the IMF is northward

Backscattering of gyrotron radiation and short-wavelength turbulence during electron cyclotron resonance plasma heating in the L-2M stellarator

Energy Technology Data Exchange (ETDEWEB)

Batanov, G. M.; Borzosekov, V. D., E-mail: tinborz@gmail.com; Kovrizhnykh, L. M.; Kolik, L. V.; Konchekov, E. M.; Malakhov, D. V.; Petrov, A. E.; Sarksyan, K. A.; Skvortsova, N. N.; Stepakhin, V. D.; Kharchev, N. K. [Russian Academy of Sciences, Prokhorov General Physics Institute (Russian Federation)

2013-06-15

Backscattering of gyrotron radiation ({theta} = {pi}) by short-wavelength density fluctuations (k{sub Up-Tack} = 30 cm{sup -1}) in the plasma of the L-2M stellarator was studied under conditions of electron cyclotron resonance (ECR) plasma heating at the second harmonic of the electron gyrofrequency (75 GHz). The scattering of the O-wave emerging due to the splitting of the linearly polarized gyrotron radiation into the X- and O-waves was analyzed. The signal obtained after homodyne detection of scattered radiation is a result of interference of the reference signal, the quasi-steady component, and the fast oscillating component. The coefficients of reflection of the quasi-steady component, R{sub =}{sup 2}(Y), and fast oscillating component, R{sub {approx}}{sup 2}(Y), of scattered radiation are estimated. The growth of the R{sub {approx}}{sup 2}(Y) coefficient from 3.7 Multiplication-Sign 10{sup -4} to 5.2 Multiplication-Sign 10{sup -4} with increasing ECR heating power from 190 to 430 kW is found to correlate with the decrease in the energy lifetime from 1.9 to 1.46 ms. The relative density of short-wavelength fluctuations is estimated to be Left-Pointing-Angle-Bracket n{sub {approx}}{sup 2} Right-Pointing-Angle-Bracket / Left-Pointing-Angle-Bracket n{sub e}{sup 2} Right-Pointing-Angle-Bracket = 3 Multiplication-Sign 10{sup -7}. It is shown that the frequencies of short-wavelength fluctuations are in the range 10-150 kHz. The recorded short-wavelength fluctuations can be interpreted as structural turbulence, the energy of which comprises {approx}10% of the total fluctuations energy. Simulations of transport processes show that neoclassical heat fluxes are much smaller than anomalous ones. It is suggested that short-wavelength turbulence plays a decisive role in the anomalous heat transport.

ULF waves in the foreshock

Science.gov (United States)

Greenstadt, E. W.; Le, G.; Strangeway, R. J.

1995-01-01

We review our current knowledge of ULF waves in planetary foreshocks. Most of this knowledge comes from observations taken within a few Earth radii of the terrestrial bow shock. Terrestrial foreshock ULF waves can be divided into three types, large amplitude low frequency waves (approximately 30-s period), upstream propagating whistlers (1-Hz waves), and 3-s waves. The 30-s waves are apparently generated by back-streaming ion beams, while the 1-Hz waves are generated at the bow shock. The source of the 3-s waves has yet to be determined. In addition to issues concerning the source of ULF waves in the foreshock, the waves present a number of challenges, both in terms of data acquisition, and comparison with theory. The various waves have different coherence scales, from approximately 100 km to approximately 1 Earth radius. Thus multi-spacecraft separation strategies must be tailored to the phenomenon of interest. From a theoretical point of view, the ULF waves are observed in a plasma in which the thermal pressure is comparable to the magnetic pressure, and the rest-frame wave frequency can be moderate fraction of the proton gyro-frequency. This requires the use of kinetic plasma wave dispersion relations, rather than multi-fluid MHD. Lastly, and perhaps most significantly, ULF waves are used to probe the ambient plasma, with inferences being drawn concerning the types of energetic ion distributions within the foreshock. However, since most of the data were acquired close to the bow shock, the properties of the more distant foreshock have to be deduced mainly through extrapolation of the near-shock results. A general understanding of the wave and plasma populations within the foreshock, their interrelation, and evolution, requires additional data from the more distant foreshock.

Macroscopic electromagnetic properties of the Irvine Field-Reversed Configuration: Equilibrium, power balance and fluctuations

Science.gov (United States)

Trask, Erik Harold

The plasma parameters and characteristics of the Irvine Field-Reversed Configuration (IFRC) are summarized in this thesis. Particular emphasis is placed on the development of the different diagnostics used to make measurements in the experiment, as well as the measurements themselves. Whenever possible, actual measurements are used in lieu of theoretical or analytical fits to data. Analysis of magnetic probes (B-dots) comprises the bulk of what is known about the IFRC. From these B-dot probes, the magnetic field structure in a two dimensional plane at constant toroidal position has been determined, and has been found to be consistent with a field-reversed configuration. Peak reversed fields of approximately 250 Gauss have been observed. Further analyses have been developed to extract information from the magnetic field structure, including components of the electric field, the current density, and plasma pressure in the same two dimensional plane. Electric field magnitudes reach 600 V/m, concurrent with current densities greater than 105 Amps/m2 and thermal pressures over 200 Pa. Spectroscopic analysis of hydrogen lines has been done to make estimates of the electron temperature, while spectroscopic measurements of the Doppler broadening of the Halpha line31 have allowed an estimate of the ion temperature. Particle losses out one axial end plane measured by an array of Faraday cups quantify the how well the configuration traps particles. Spectral information derived from B-dot probes indicates that there is substantial power present at frequencies lying between the hydrogen cyclotron and mean gyrofrequency. These various measurements are used to find the following parameters that characterize the Irvine FRC: (1) Electromagnetic and thermal stored energies as functions of time. (2) Power balance, including input power from the field coils, resistive heating, power lost by particle transport and radiation, and particle and energy confinement times. (3) Strong

Effects of energetic heavy ions on electromagnetic ion cyclotron wave generation in the plasmapause region

International Nuclear Information System (INIS)

Kozyra, J.U.; Cravens, T.E.; Nagy, A.F.; Fontheim, E.G.; Ong, R.S.B.

1984-01-01

An expression for the linear electromagnetic ion cyclotron convective growth rate has been derived, considering multiple ions in the energetic anisotropic component of the plasma (which provides the free energy for the instability) as well as in the cold component of the plasma. This represents a modification of recent treatments investigating electromagnetic ion cyclotron growth rates which have considered only hydrogen ions in the energetic component. Four major effects on the growth and propagation characteristics result from inclusion of heavy ions in the energetic component. Some wave growth occurs at low frequencies below the corresponding marginally unstable wave mode for each heavy ion. Enhanced quasi-monochronomatic peaks in the convective growth rate appear just below the O + and He + gyrofrequency and can be quite pronounced for certain plasma conditions. Stop bands, decreased group velocity and other effects normally attributed to cold heavy ions can be produced or enhanced by heavy ions in the energetic plasma component. Partial or complete suppression of wave growth at frequencies above the marginally unstable wave mode for a particular energetic heavy ion can greatly alter the growth rates that would occur in the absence of this energetic heavy ion. The expression for the linear electromagnetic ion cyclotron convective growth rate along with appropriate plasma parameters was used to investigate the nature of linear wave growth in the plasmapause region. The frequencies of peaks in the convective growth rate given by this model compare favorably with wave measurements in this region. It is conceivable that through wave-particle interactions, electromagnetic ion cyclotron waves could supply the energy source for various plasmapause region phenomena such as the O + torus, the plasma cloak and stable auroral red arcs

Cluster observations of particle acceleration up to supra-thermal energies in the cusp region related to low-frequency wave activity – possible implications for the substorm initiation process

Directory of Open Access Journals (Sweden)

T. A. Fritz

2008-03-01

Full Text Available The purpose of our study is to investigate the way particles are accelerated up to supra-thermal energies in the cusp diamagnetic cavities. For this reason we have examined a number of Cluster cusp crossings, originally identified by Zhang et al. (2005, for the years 2001 and 2002 using data from RAPID, STAFF, EFW, CIS, PEACE, and FGM experiments. In the present study we focus on two particular cusp crossings on 25 March 2002 and on 10 April 2002 which demonstrate in a clear way the general characteristics of the events in our survey. Both events exhibit very sharp spatial boundaries seen both in CNO (primarily single-charged oxygen of ionospheric origin based on CIS observations and H+ flux increases within the RAPID energy range with the magnetic field intensity being anti-correlated. Unlike the first event, the second one shows also a moderate electron flux increase. The fact that the duskward electric field Ey has relatively low values <5 mV/m while the local wave activity is very intense provides a strong indication that particle energization is caused primarily by wave-particle interactions. The wave power spectra and propagation parameters during these cusp events are examined in detail. It is concluded that the high ion fluxes and at the same time the presence or absence of any sign of energization in the electrons clearly shows that the particle acceleration depends on the wave power near the local particle gyrofrequency and on the persistence of the wave-particle interaction process before particles escape from cusp region. Furthermore, the continuous existence of energetic O+ ions suggests that energetic O+ populations are of spatial nature at least for the eight events that we have studied so far.

Pulsed energy storage antennas for ionospheric modification

Directory of Open Access Journals (Sweden)

R. F. Wuerker

2005-01-01

Full Text Available Interesting, "new", very high peak-power pulsed radio frequency (RF antennas have been assembled at the HIPAS Observatory (Alaska, USA and also at the University of California at Los Angeles (UCLA, USA; namely, a pair of quarter wavelength (λ/4 long cylindrical conductors separated by a high voltage spark gap. Such a combination can radiate multi-megawatt RF pulses whenever the spark gap fires. The antenna at HIPAS is 53m long (λ/2 with a central pressurized SF₆ spark gap. It is mounted 5 meters (λ/21 above a ground plane. It radiates at 2.85MHz. The two antenna halves are charged to ± high voltages by a Tesla coil. Spark gap voltages of 0.4 MV (at the instant of spark gap closure give peak RF currents of ~1200A which correspond to ~14 MW peak total radiated power, or ~56 MW of Effective Radiated Power (ERP. The RF pulse train is initially square, decaying exponentially in time with Qs of ~50. Two similar but smaller 80-MHz antennas were assembled at UCLA to demonstrate their synchronization with a pulsed laser which fired the spark gaps in the two antennas simultanoeously. These experiments show that one can anticipate a pulsed array of laser synchronized antennas having a coherent Effective Radiated Power (ERP>10GW. One can even reconsider a pulse array radiating at 1.43MHz which corresponds to the electron gyrofrequency in the Earth's magnetic field at ~200km altitude. These "new" pulsed high power antennas are hauntingly similar to the ones used originally by Hertz (1857-1894 during his (1886-1889 seminal verifications of Maxwell's (1864 theory of electrodynamics.

Pulsed energy storage antennas for ionospheric modification

Directory of Open Access Journals (Sweden)

R. F. Wuerker

2005-01-01

Full Text Available Interesting, "new", very high peak-power pulsed radio frequency (RF antennas have been assembled at the HIPAS Observatory (Alaska, USA and also at the University of California at Los Angeles (UCLA, USA; namely, a pair of quarter wavelength (λ/4 long cylindrical conductors separated by a high voltage spark gap. Such a combination can radiate multi-megawatt RF pulses whenever the spark gap fires. The antenna at HIPAS is 53m long (λ/2 with a central pressurized SF6 spark gap. It is mounted 5 meters (λ/21 above a ground plane. It radiates at 2.85MHz. The two antenna halves are charged to ± high voltages by a Tesla coil. Spark gap voltages of 0.4 MV (at the instant of spark gap closure give peak RF currents of ~1200A which correspond to ~14 MW peak total radiated power, or ~56 MW of Effective Radiated Power (ERP. The RF pulse train is initially square, decaying exponentially in time with Qs of ~50. Two similar but smaller 80-MHz antennas were assembled at UCLA to demonstrate their synchronization with a pulsed laser which fired the spark gaps in the two antennas simultanoeously. These experiments show that one can anticipate a pulsed array of laser synchronized antennas having a coherent Effective Radiated Power (ERP>10GW. One can even reconsider a pulse array radiating at 1.43MHz which corresponds to the electron gyrofrequency in the Earth's magnetic field at ~200km altitude. These "new" pulsed high power antennas are hauntingly similar to the ones used originally by Hertz (1857-1894 during his (1886-1889 seminal verifications of Maxwell's (1864 theory of electrodynamics.

Polarization transfer in relativistic magnetized plasmas

Science.gov (United States)

Heyvaerts, Jean; Pichon, Christophe; Prunet, Simon; Thiébaut, Jérôme

2013-04-01

The polarization transfer coefficients of a relativistic magnetized plasma are derived. These results apply to any momentum distribution function of the particles, isotropic or anisotropic. Particles interact with the radiation either in a non-resonant mode when the frequency of the radiation exceeds their characteristic synchrotron emission frequency or quasi-resonantly otherwise. These two classes of particles contribute differently to the polarization transfer coefficients. For a given frequency, this dichotomy corresponds to a regime change in the dependence of the transfer coefficients on the parameters of the particle's population, since these parameters control the relative weight of the contribution of each class of particles. Our results apply to either regimes as well as the intermediate one. The derivation of the transfer coefficients involves an exact expression of the conductivity tensor of the relativistic magnetized plasma that has not been used hitherto in this context. Suitable expansions valid at frequencies much larger than the cyclotron frequency allow us to analytically perform the summation over all resonances at high harmonics of the relativistic gyrofrequency. The transfer coefficients are represented in the form of two-variable integrals that can be conveniently computed for any set of parameters by using Olver's expansion of high-order Bessel functions. We particularize our results to a number of distribution functions, isotropic, thermal or power law, with different multipolar anisotropies of low order, or strongly beamed. Specifically, earlier exact results for thermal distributions are recovered. For isotropic distributions, the Faraday coefficients are expressed in the form of a one-variable quadrature over energy, for which we provide the kernels in the high-frequency limit and in the asymptotic low-frequency limit. An interpolation formula extending over the full energy range is proposed for these kernels. A similar reduction to a

Cyclotron Acceleration of Relativistic Electrons through Landau Resonance with Obliquely Propagating Whistler Mode Chorus Emissions

Science.gov (United States)

Omura, Y.; Hsieh, Y. K.; Foster, J. C.; Erickson, P. J.; Kletzing, C.; Baker, D. N.

2017-12-01

A recent test particle simulation of obliquely propagating whistler mode wave-particle interaction [Hsieh and Omura, 2017] shows that the perpendicular wave electric field can play a significant role in trapping and accelerating relativistic electrons through Landau resonance. A further theoretical and numerical investigation verifies that there occurs nonlinear wave trapping of relativistic electrons by the nonlinear Lorentz force of the perpendicular wave magnetic field. An electron moving with a parallel velocity equal to the parallel phase velocity of an obliquely propagating wave basically see a stationary wave phase. Since the electron position is displaced from its gyrocenter by a distance ρ*sin(φ), where ρ is the gyroradius and φ is the gyrophase, the wave phase is modulated with the gyromotion, and the stationary wave fields as seen by the electron are expanded as series of Bessel functions Jn with phase variations n*φ. The J1 components of the wave electric and magnetic fields rotate in the right-hand direction with the gyrofrequency, and they can be in resonance with the electron undergoing the gyromotion, resulting in effective electron acceleration and pitch angle scattering. We have performed a subpacket analysis of chorus waveforms observed by the Van Allen Probes [Foster et al., 2017], and calculated the energy gain by the cyclotron acceleration through Landau resonance. We compare the efficiencies of accelerations by cyclotron and Landau resonances in typical events of rapid electron acceleration observed by the Van Allen Probes.References:[1] Hsieh, Y.-K., and Y. Omura (2017), Nonlinear dynamics of electrons interacting with oblique whistler mode chorus in the magnetosphere, J. Geophys. Res. Space Physics, 122, 675-694, doi:10.1002/2016JA023255.[2] Foster, J. C., P. J. Erickson, Y. Omura, D. N. Baker, C. A. Kletzing, and S. G. Claudepierre (2017), Van Allen Probes observations of prompt MeV radiation belt electron acceleration in nonlinear

theoretical and experimental study of plasma acceleration by means of R.F. and static magnetic field gradient

International Nuclear Information System (INIS)

Bardet, Rene; Consoli, Terenzio; Geller, Richard

1964-09-01

In the first part of the paper, the theory of the physical mechanism of ion dragging by accelerated electrons due to the superimposition of the gradient of a electromagnetic field and the gradient of a static magnetic field, is described. The resulting trajectory of the electrons is a helicoid and one shows the variations of the diameter and the path of the spirals along the axis as a function of the difference between the gyrofrequency and the applied R.F. frequency. The ion acceleration is due to an electron space charge effect. The grouping of the equations of the electronic and ionic fluid motions leads to the introduction of a tensor mass: along the x and y direction the transverse motion of the fluid is controlled by the relativistic mass of electrons whereas along the z direction the axial motion is determined by the ionic mass. Then we deduce physical consequences of the theoretical study and give three experimental evidences. The second part of the paper is devoted to the experimental device called Pleiade which allowed us to verify some of the theoretical predictions. Pleiade produces a D.C. operating plasma beam in which the electrons exhibit radially oriented energies whereas the ionic energy is mainly axial. The experimental results indicate that the energy of the particles is in the keV range. In the third part we deal with the reflecting properties of the device. We show that the R.F. static magnetic field gradients are not only capable of accelerating a Plasma beam along the axially decreasing magnetic field, but are also capable of stopping and reflecting such a beam when the latter is moving along an axially increasing magnetic field. We describe finally a plasma accumulation experiment in which two symmetric structures form simultaneously an accelerator and a 'dynamic mirror' for the particles. Evidence of accumulation is given. (authors) [fr

ULF Narrowband Emissions Analysis in the Terrestrial Polar Cusps

Science.gov (United States)

Grison, B.; Pisa, D.

2013-05-01

Polar cusps are known to be a key region for transfer of mass and momentum between the adjacent magnetosheath and the magnetosphere. The 4 spacecraft of the Cluster ESA mission crossed the polar cusps in their most distant part to the Earth in the early years of the mission (2000-2004) because of their highly eccentric orbit. The ULF wave activity in the cusp region has been linked with the magnetosheath plasma penetration since HEOS observations (D'Angelo et al., 1974). Wave and particle interaction play an important role in this colisionless plasma. The observed wave activity certainly results from both distant and local generation mechanisms. From Cluster case studies we propose to focus on one aspect for each of this place of generation. Concerning the distant generation, the possibility of a wave generation at the magnetopause itself is investigated. For this purpose we compare the propagation of the emissions on each side of the magnetopasue, i.e. in the cusp and in the magnetosheath. Concerning the local generation, the presence of locally generated waves above the local proton gyrofrequency that display a left hand polarization has been reported in Polar and Cluster studies (Le et al., 2001; Nykyri et al., 2003 ). The Doppler shift was not large enough to explain the observed frequency. We propose here to combine various techniques (k-filtering analysis, WHAMP simulations) to achieve a precise wave vector estimation and to explain these observations. References: D'Angelo, N., A. Bahnsen, and H. Rosenbauer (1974), Wave and particle measurements at the polar cusp, J. Geophys. Res., 79( 22), 3129-3134, doi:10.1029/JA079i022p03129. Le, G., X. Blanco-Cano, C. T. Russell, X.-W. Zhou, F. Mozer, K. J. Trattner, S. A. Fuselier, and B. J. Anderson (2001), Electromagnetic ion cyclotron waves in the high-altitude cusp: Polar observations, J. Geophys. Res., 106(A9), 19067-19079, doi:10.1029/2000JA900163. Nykyri, K., P. J. Cargill, E. A. Lucek, T. S. Horbury, A. Balogh

Comparative study of ion cyclotron waves at Mars, Venus and Earth

Science.gov (United States)

Wei, H. Y.; Russell, C. T.; Zhang, T. L.; Blanco-Cano, X.

2011-08-01

Ion cyclotron waves are generated in the solar wind when it picks up freshly ionized planetary exospheric ions. These waves grow from the free energy of the highly anisotropic distribution of fresh pickup ions, and are observed in the spacecraft frame with left-handed polarization and a wave frequency near the ion's gyrofrequency. At Mars and Venus and in the Earth's polar cusp, the solar wind directly interacts with the planetary exospheres. Ion cyclotron waves with many similar properties are observed in these diverse plasma environments. The ion cyclotron waves at Mars indicate its hydrogen exosphere to be extensive and asymmetric in the direction of the interplanetary electric field. The production of fast neutrals plays an important role in forming an extended exosphere in the shape and size observed. At Venus, the region of exospheric proton cyclotron wave production may be restricted to the magnetosheath. The waves observed in the solar wind at Venus appear to be largely produced by the solar-wind-Venus interaction, with some waves at higher frequencies formed near the Sun and carried outward by the solar wind to Venus. These waves have some similarity to the expected properties of exospherically produced proton pickup waves but are characterized by magnetic connection to the bow shock or by a lack of correlation with local solar wind properties respectively. Any confusion of solar derived waves with exospherically derived ion pickup waves is not an issue at Mars because the solar-produced waves are generally at much higher frequencies than the local pickup waves and the solar waves should be mostly absorbed when convected to Mars distance as the proton cyclotron frequency in the plasma frame approaches the frequency of the solar-produced waves. In the Earth's polar cusp, the wave properties of ion cyclotron waves are quite variable. Spatial gradients in the magnetic field may cause this variation as the background field changes between the regions in which

Stability of a Magnetically Confined 20-KeV Steady-State Plasma; Stabilite d'un Plasma Stationnaire de 20 KeV Confine par un Champ Magnetique; Ustojchivost' 20 KehV-statsionarnoj plazmy, uderzhivaemoj magnitnym polem; Estabilidad en Regimen Estacionario de un Plasma de 20 KeV Confinado Magneticamente

Energy Technology Data Exchange (ETDEWEB)

Futch, Jr., A. H.; Damm, C. C.; Foote, J. H.; Freis, R.; Gordon, F. J.; Hunt, A. L.; Killeen, J.; Moses, K. G.; Post, R. F.; Steinhaus, J. F. [Lawrence Radiation Laboratory, Livermore, CA (United States)

1966-04-15

oscillations at the ion gyrofrequency and with pulsed emission of electrons through the mirror region accompanied by increases in the plasma potential suggests the presence of an electrostatic resonance instability. Differences in gyrofrequency activity among simple mirror, dodecapole and octopole cases are described but specific mode identification is not yet possible. (author) [French] Les auteurs ont etudie la stabilite d'un plasma d'hydrogene stationnaire de 20 keV dans l'appareil a injection d'atomes neutres 'Alice ' de Livermore, dans differents champs magnetiques de confinement. Dans un champ simple a miroirs, l'observation d'oscillations a basse frequence et d'une limite de la densite des ions pieges fait l'objet d'une interpretation en fonction de l'instabilite de derive a basse frequence. Les auteurs ont effectue un traitement theorique de cette instabilite qui porte sur les effets de la dimension finie des orbites des ions, les effets d'un champ electrique d'ordre zero et les effets de la difference entre la densite des ions et celle des electrons. Le champ electrique et le champ magnetique peuvent etre des fonctions arbitraires de la coordonnee spatiale r. Comme il n'est pas possible en general de resoudre analytiquement les equations differentielles ainsi calculees, les auteurs ont resolu numeriquement les equations fondamentales par la methode des differences finies. Ces resultats, qui concordent avec les solutions analytiques obtenues dans le cas limite d'un champ electrique qui n'est pas d'ordre zero, permettent d'expliquer les variations de la densite et de la frequence de la derive observees experimentalement en presence d'un champ electrique fini d'ordre zero. Comme ce traitement theorique part de l'hypothese que le champ magnetique est une fonction arbitraire de r, il est possible d'obtenir des resultats pour des champs ayant un gradient d'abord negatif qui devient ensuite positif lorsque r augmente. Les auteurs comparent les resultats de ces calculs aux

Non-stationarity of the quasi-perpendicular bow shock: comparison between Cluster observations and simulations

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H. Comişel

2011-02-01

Full Text Available We have performed full particle electromagnetic simulations of a quasi-perpendicular shock. The shock parameters have been chosen to be appropriate for the quasi-perpendicular Earth's bow shock observed by Cluster on 24 January 2001 (Lobzin et al., 2007. We have performed two simulations with different ion to electron mass ratio: run 1 with mi/me=1840 and run 2 with mi/me=100. In run 1 the growth rate of the modified two-stream instability (MTSI is large enough to get excited during the reflection and upstream gyration of part of the incident solar wind ions. The waves due to the MTSI are on the whistler mode branch and have downstream directed phase velocities in the shock frame. The Poynting flux (and wave group velocity far upstream in the foot is also directed in the downstream direction. However, in the density and magnetic field compression region of the overshoot the waves are refracted and the Poynting flux in the shock frame is directed upstream. The MTSI is suppressed in the low mass ratio run 2. The low mass ratio run shows more clearly the non-stationarity of the shock with a larger time scale of the order of an inverse ion gyrofrequency (Ωci: the magnetic field profile flattens and steepens with a period of ~1.5Ωci−1. This non-stationarity is different from reformation seen in previous simulations of perpendicular or quasi-perpendicular shocks. Beginning with a sharp shock ramp the large electric field in the normal direction leads to high reflection rate of solar wind protons. As they propagate upstream, the ion bulk velocity decreases and the magnetic field increases in the foot, which results in a flattening of the magnetic field profile and in a decrease of the normal electric field. Subsequently the reflection rate decreases and the whole shock profile steepens again. Superimposed on this 'breathing' behavior are in the realistic mass ratio case the waves due to the MTSI. The simulations lead us to a re-interpretation of

Modeling transverse heating and outflow of ionospheric ions from the dayside cusp/cleft. 1 A parametric study

Directory of Open Access Journals (Sweden)

M. Bouhram

2003-08-01

Full Text Available The transport patterns of non-thermal H + and O + field-aligned flows from the dayside cusp/cleft, associated with transverse heating by means of wave-particle interactions and in combination with the poleward motion due to the magnetospheric convection are investigated. This has been accomplished by developing a steady-state, two-dimensional, trajectory-based code. The ion heating is modelled by means of a Monte Carlo technique, via the process of ion cyclotron resonance (ICR, with the electromagnetic left-hand circular polarized component of a broad-band, extremely low-frequency (BBELF turbulence. The altitude dependence of ICR heating from 1000 km to 3 Earth radii (RE is modelled by a power law spectrum, with an index a, and a parameter w0 that is proportional to the spectral density at a referenced gyrofrequency. Because of the finite latitudinal extent of the cusp/cleft, the incorporation of the horizontal convection drift leads to a maximum residence time tD of the ions when being energized. A large set of simulations has been computed so as to study the transport patterns of the H + and O + bulk parameters as a function of tD , a, and w0. Residence time effects are significant in O + density patterns while negligible for H +. When comparing the results with analytical one-dimensional theories (Chang et al., 1986; Crew et al., 1990, we find that mean ion energies and pitch angles at the poleward edge of the heating region are slightly influenced by tD and may be used as a probe of ICR parameters ( a, w0. Conversely, poleward of the heating region, upward velocity and mean energy dispersive patterns depend mainly on tD (e.g. the magnitude of the convection drift with latitudinal profiles varying versus tD . In short, the main conclusion of the paper is that any triplet (tD , a, w0 leads to a unique transport-pattern feature of ion flows associated with a cusp/cleft ionospheric source. In a companion paper, by using high-altitude (1.5–3 RE

The first full-resolution measurements of Auroral Medium Frequency Burst Emissions

Science.gov (United States)

Bunch, N. L.; Labelle, J.; Weatherwax, A.; Hughes, J.

2008-12-01

Auroral MF burst is a naturally occurring auroral radio emission which appears unstructured on resolution of previous measurements, is observed in the frequency range of 0.8-4.5 MHz, and has typical amplitudes of around 10-14 V2/m2Hz, and durations of a few minutes. The emission occurs at substorm onset. Since Sept 2006, Dartmouth has operated a broadband (0-5 MHz) interferometer at Toolik Lake, Alaska (68° 38' N, 149° 36' W, 68.51 deg. magnetic latitude), designed for the study of auroral MF burst emissions. Normal operation involves taking snapshots of waveforms from four spaced antennas from which wave spectral and directional information is obtained. However, the experiment can also be run in "continuous mode" whereby the signal from a selected antenna is sampled continuously at 10 M samples/second. A "continuous mode" campaign was run 0800-1200 UT (~2200-0200 MLT) daily from March 21 to April 19, 2008. During this campaign more than twenty auroral MF burst emissions were observed, including three extraordinarily intense examples lasting approximately two minutes each. These observations represent the highest time and frequency resolution data ever collected of MF burst emissions. These data allow us to better characterize the null near twice the electron gyrofrequency identified in previous experiments, since examples of this feature observed during this campaign display a strong null ~50 kHz in bandwidth, with sharp boundaries and occasionally coincident with 2 fce auroral roar. These data also allow us to search for frequency-time structures embedded in MF-burst. One prominent feature appears to be a strong single frequency emission which broadens down to lower frequencies over time, spreading to approximately 500 kHz in bandwidth over ~10 ms. Among other features observed are a diffuse and unstructured emission, as well as what could potentially be several separate emission sources, with multiple emissions occurring simultaneously, appearing as weaker

Substorms in the Inner Plasma Sheet

Science.gov (United States)

Le Contel, O.; Perraut, S.; Roux, A.; Pellat, R.; Korth, A.

Thin Current Sheets (TCS) are regularly formed prior to substorm breakup, even in the near-Earth plasma sheet, as close as the geostationary orbit. A self-consistent kinetic theory describing the response of the plasma sheet to an electromagnetic perturbation is given. This perturbation corresponds to an external forcing, for instance caused by the solar wind (not an internal instability). The equilibrium of the configuration of this TCS in the presence of a time varying perturbation is shown to produce a strong parallel thermal anisotropy (T∥ > T⊺) of energetic electrons and ions (E>50keV) as well as an enhanced diamagnetic current carried by low energy ions (Ecurrents tend to enhance the confinement of this current sheet near the magnetic equator. These results are compared with data gathered by GEOS-2 at the geostationary orbit, where the magnetic signatures of TCS, and parallel anisotropies are regularly observed prior to breakup. By ensuring quasi-neutrality everywhere we find, when low frequency electromagnetic perturbations are applied, that although the magnetic field line remains an equipotential to the lowest order in Te/Ti, a field-aligned potential drop exists to the next order in (Te/Ti). Thus the development of a TCS implies the formation of a field-aligned potential drop (~= few hundred volts) to ensure the quasi-neutrality everywhere. For an earthward directed pressure gradient, a field-aligned electric field, directed towards the ionosphere, is obtained, on the western edge of the perturbation (i.e. western edge of the current sheet). Thus field aligned beams of electrons are expected to flow towards the equatorial region on the western edge of the current sheet. We study the stability of these electron beams and show that they are unstable to ``High Frequency'' (HF) waves. These ``HF'' waves are regularly observed at frequencies of the order of the proton gyrofrequency (fH+) just before, or at breakup. The amplitude of these HF waves is so

Modeling transverse heating and outflow of ionospheric ions from the dayside cusp/cleft. 1 A parametric study

Directory of Open Access Journals (Sweden)

M. Bouhram

Full Text Available The transport patterns of non-thermal H + and O + field-aligned flows from the dayside cusp/cleft, associated with transverse heating by means of wave-particle interactions and in combination with the poleward motion due to the magnetospheric convection are investigated. This has been accomplished by developing a steady-state, two-dimensional, trajectory-based code. The ion heating is modelled by means of a Monte Carlo technique, via the process of ion cyclotron resonance (ICR, with the electromagnetic left-hand circular polarized component of a broad-band, extremely low-frequency (BBELF turbulence. The altitude dependence of ICR heating from 1000 km to 3 Earth radii (R_E is modelled by a power law spectrum, with an index a, and a parameter w₀ that is proportional to the spectral density at a referenced gyrofrequency. Because of the finite latitudinal extent of the cusp/cleft, the incorporation of the horizontal convection drift leads to a maximum residence time t_D of the ions when being energized. A large set of simulations has been computed so as to study the transport patterns of the H + and O + bulk parameters as a function of t_D , a, and w₀. Residence time effects are significant in O + density patterns while negligible for H +. When comparing the results with analytical one-dimensional theories (Chang et al., 1986; Crew et al., 1990, we find that mean ion energies and pitch angles at the poleward edge of the heating region are slightly influenced by t_D and may be used as a probe of ICR parameters ( a, w₀. Conversely, poleward of the heating region, upward velocity and mean energy dispersive patterns depend mainly on t_D (e.g. the magnitude of the convection drift with latitudinal profiles varying versus

Wide-banded NTC radiation: local to remote observations by the four Cluster satellites

Directory of Open Access Journals (Sweden)

P. M. E. Décréau

2015-10-01

Full Text Available The Cluster multi-point mission offers a unique collection of non-thermal continuum (NTC radio waves observed in the 2–80 kHz frequency range over almost 15 years, from various view points over the radiating plasmasphere. Here we present rather infrequent case events, such as when primary electrostatic sources of such waves are embedded within the plasmapause boundary far from the magnetic equatorial plane. The spectral signature of the emitted electromagnetic waves is structured as a series of wide harmonic bands within the range covered by the step in plasma frequency encountered at the boundary. Developing the concept that the frequency distance df between harmonic bands measures the magnetic field magnitude B at the source (df = Fce, electron gyrofrequency, we analyse three selected events. The first one (studied in Grimald et al., 2008 presents electric field signatures observed by a Cluster constellation of small size (~ 200 to 1000 km spacecraft separation placed in the vicinity of sources. The electric field frequency spectra display frequency peaks placed at frequencies fs = n df (n being an integer, with df of the order of Fce values encountered at the plasmapause by the spacecraft. The second event, taken from the Cluster tilt campaign, leads to a 3-D view of NTC waves ray path orientations and to a localization of a global source region at several Earth radii (RE from Cluster (Décréau et al., 2013. The measured spectra present successive peaks placed at fs ~ (n+ 1/2 df. Next, considering if both situations might be two facets of the same phenomenon, we analyze a third event. The Cluster fleet, configured into a constellation of large size (~ 8000 to 25 000 km spacecraft separation, allows us to observe wide-banded NTC waves at different distances from their sources. Two new findings can be derived from our analysis. First, we point out that a large portion of the plasmasphere boundary layer, covering a large range of magnetic

Magnetic spectral signatures in the Earth's magnetosheath and plasma depletion layer

Science.gov (United States)

Anderson, Brian J.; Fuselier, Stephen A.; Gary, S. Peter; Denton, Richard E.

1994-01-01

Correlations between plasma properties and magnetic fluctuations in the sub-solar magnetosheath downstream of a quasi-perpendicular shock have been found and indicate that mirror and ion cyclotronlike fluctuations correlate with the magnetosheath proper and plasma depletion layer, respectively (Anderson and Fueselier, 1993). We explore the entire range of magnetic spectral signatures observed from the Active Magnetospheric Particle Tracer Explorers/Charge Composition Explorer (AMPTE/CCE)spacecraft in the magnetosheath downstream of a quasi-perpendicular shock. The magnetic spectral signatures typically progress from predominantly compressional fluctuations,delta B(sub parallel)/delta B perpendicular to approximately 3, with F/F (sub p) less than 0.2 (F and F (sub p) are the wave frequency and proton gyrofrequency, respectively) to predominantly transverse fluctuations, delta B(sub parallel)/delta B perpendicular to approximately 0.3, extending up to F(sub p). The compressional fluctuations are characterized by anticorrelation between the field magnitude and electron density, n(sub e), and by a small compressibility, C(sub e) identically equal to (delta n(sub e)/n(sub e)) (exp 2) (B/delta B(sub parallel)) (exp 2) approximately 0.13, indicative of mirror waves. The spectral characteristics of the transverse fluctuations are in agreement with predictions of linear Vlasov theory for the H(+) and He(2+) cyclotron modes. The power spectra and local plasma parameters are found to vary in concert: mirror waves occur for beta(s ub parallel p) (beta (sub parallel p) identically = 2 mu(sub zero) n(sub p) kT (sub parallel p) / B(exp 2) approximately = 2, A(sub p) indentically = T(sub perpendicular to p)/T(sub parallel p) - 1 approximately = 0.4, whereas cyclotron waves occur for beta (sub parallel p) approximately = 0.2 and A(sub p) approximately = 2. The transition from mirror to cyclotron modes is predicted by linear theory. The spectral characteristics overlap for

Gyrokinetic Electron and Fully Kinetic Ion Particle Simulation of Collisionless Plasma Dynamics

Energy Technology Data Exchange (ETDEWEB)

Yu Lin; Xueyi Wang; Liu Chen; Zhihong Lin

2009-08-11

Fully kinetic-particle simulations and hybrid simulations have been utilized for decades to investigate various fundamental plasma processes, such as magnetic reconnection, fast compressional waves, and wave-particle interaction. Nevertheless, due to disparate temporal and spatial scales between electrons and ions, existing fully kinetic-particle codes have to employ either unrealistically high electron-to-ion mass ratio, me/mi, or simulation domain limited to a few or a few ten's of the ion Larmor radii, or/and time much less than the global Alfven time scale in order to accommodate available computing resources. On the other hand, in the hybrid simulation, the ions are treated as fully kinetic particles but the electrons are treated as a massless fluid. The electron kinetic effects, e.g., wave-particle resonances and finite electron Larmor radius effects, are completely missing. Important physics, such as the electron transit time damping of fast compressional waves or the triggering mechanism of magnetic reconnection in collisionless plasmas is absent in the hybrid codes. Motivated by these considerations and noting that dynamics of interest to us has frequencies lower than the electron gyrofrequency, we planned to develop an innovative particle simulation model, gyrokinetic (GK) electrons and fully kinetic (FK) ions. In the GK-electron and FK-ion (GKe/FKi) particle simulation model, the rapid electron cyclotron motion is removed, while keeping finite electron Larmor radii, realistic me/mi ratio, wave-particle interactions, and off-diagonal components of electron pressure tensor. The computation power can thus be significantly improved over that of the full-particle codes. As planned in the project DE-FG02-05ER54826, we have finished the development of the new GK-electron and FK-ion scheme, finished its benchmark for a uniform plasma in 1-D, 2-D, and 3-D systems against linear waves obtained from analytical theories, and carried out a further convergence

Gyrokinetic Electron and Fully Kinetic Ion Particle Simulation of Collisionless Plasma Dynamics

International Nuclear Information System (INIS)

Lin, Yu; Wang, Xueyi; Chen, Liu; Lin, Zhihong

2009-01-01

Fully kinetic-particle simulations and hybrid simulations have been utilized for decades to investigate various fundamental plasma processes, such as magnetic reconnection, fast compressional waves, and wave-particle interaction. Nevertheless, due to disparate temporal and spatial scales between electrons and ions, existing fully kinetic-particle codes have to employ either unrealistically high electron-to-ion mass ratio, me/mi, or simulation domain limited to a few or a few ten's of the ion Larmor radii, or/and time much less than the global Alfven time scale in order to accommodate available computing resources. On the other hand, in the hybrid simulation, the ions are treated as fully kinetic particles but the electrons are treated as a massless fluid. The electron kinetic effects, e.g., wave-particle resonances and finite electron Larmor radius effects, are completely missing. Important physics, such as the electron transit time damping of fast compressional waves or the triggering mechanism of magnetic reconnection in collisionless plasmas is absent in the hybrid codes. Motivated by these considerations and noting that dynamics of interest to us has frequencies lower than the electron gyrofrequency, we planned to develop an innovative particle simulation model, gyrokinetic (GK) electrons and fully kinetic (FK) ions. In the GK-electron and FK-ion (GKe/FKi) particle simulation model, the rapid electron cyclotron motion is removed, while keeping finite electron Larmor radii, realistic me/mi ratio, wave-particle interactions, and off-diagonal components of electron pressure tensor. The computation power can thus be significantly improved over that of the full-particle codes. As planned in the project DE-FG02-05ER54826, we have finished the development of the new GK-electron and FK-ion scheme, finished its benchmark for a uniform plasma in 1-D, 2-D, and 3-D systems against linear waves obtained from analytical theories, and carried out a further convergence test

Drift Instabilities and Electron Cyclotron Oscillations for Arbitrary Plasma Pressure; Instabilites de Derive et Oscillations Cyclotroniques des Electrons pour des Pressions de Plasma Arbitraires; Drejfovaya neustojchivost' i ehlektronno-tsiklotronnye kolebaniya pri proizvol'nom davlenii plazmy; Inestabilidades de Deriva y Oscilaciones Ciclotronicas de los Electrones en un Plasma de Presion Arbitraria

Energy Technology Data Exchange (ETDEWEB)

Krall, N. A.; Pearlstein, L. D. [General Atomic Division, General Dynamics Corporation, San Diego, CA (United States)

1966-04-15

Most of the familiar drift instabilities (flute, universal, etc.) were, calculated in the limit {beta} = (plasma pressure)/(magnetic pressure) = 0. In this limit the perturbed electric field is electrostatic, and the Vlasov equation is remarkably simplified. The {beta} limit for validity of the electrostatic approximation depends on the particular mode considered and many present experiments fall outside the range. Two well-known low frequency drift instabilities are examined at arbitrary {beta}; the zero-{beta} regime is determined and stability criteria for larger values of {beta} are derived. In addition, the influence of finite {beta} on radiation at the electron cyclotron harmonics is examined. The finite Larmor radius (R) flute instability driven by mirror type curvature of the magnetic field is considered first. The lowest order's ominously large contribution, inversely proportional to R{sup 2}, cancels to all orders of {beta}. The leading terms are then independent of R, and are. included in the eigenvalue problem; stability criteria are obtained for various ranges of B. Next the universal instability, E = Perturbed = E (exp ik{sub Up-Tack }r{sub Up-Tack })(exp ik{sub II}r{sub II}), in a uniform magnetic field B = B{sub 0}i{sub II} is considered, with field curvature simulated by a fictitious gravity. Here the zero-{beta} limit is dependent upon wavelengths. If {beta} < (electron mass)/(ion mass), or if {beta} <(k{sub II}r{sub p}){sup 2} where r{sub p} = plasma radius and 1/k{sub II} {>=} plasma length, the zero-{beta} limit obtains. Since the instability only exists for (k{sub II}r{sub p}){sup 2} < 0.01, a modest plasma pressure violates the zero-{beta} limit. The eigenvalue for {beta} >(k{sub ll}r{sub p}){sup 2} is calculated and conditions for cusp stabilization as well as mirror destabilization are obtained. The dominant high frequency non-relativistic modes of the stable zero-{beta} plasma are longitudinal waves at electron gyrofrequency harmonics. If

Anomalous Plasma Diffusion in Magnetic Wells; Diffusion Anormale de Plasma dans des Puits Magnetique; Anomal'naya diffuziya plazmy v magnitnykh yamakh; Difusion Anomala de Plasma en Pozos Magneticos

Energy Technology Data Exchange (ETDEWEB)

Fowler, T. K.; Guest, G. E. [Oak Ridge National Laboratory, Oak Ridge, TN (United States)

1966-04-15

We discuss radial plasma transport in magnetic wells (magnetic gradient dB/dr > 0) with particular attention to low frequency instabilities not stabilized by the positive gradient ({omega} ' {omega}{sub ci}, k{rho} ' 1). We take {beta} small. The unperturbed plasma departs from thermal equilibrium only in the azimuthal current-and radial pressure profile inherent in confinement. If dB/dr > 0 and {Delta}B = R(dB/dr) > B(T{sub e}/T{sub i}), the ExB ''diffusion'' coefficient is (1) D{sub Up-Tack} {<=} (cT{sub /}eB )({rho}{sub i}/R) (T{sub e}/T{sub i} + m{sub e}/m{sub i}) Vulgar-Fraction-One-Half where {rho}{sub i} is the ion gyroradius and R is the plasma radius. If dB/dr is only positive on the average, there is an additional requirement that L/R < (T{sub i}/T{sub e}) Vulgar-Fraction-One-Half , where L is the length along B over which dB/dr is negative. Applications to various thermonuclear magnetic confinement geometries are discussed. Results in some cases are encouraging and complement our previous conclusion that stochastic diffusion is also tolerable for fusion. Open questions are the {beta} limit and the non-linear behavior of certain velocity-space instabilities at {omega} {>=} {omega}{sub ci}. the ion gyrofrequency. In deriving eq. 1, we take D{sub Up-Tack} = {lambda}(cE{sub Up-Tack }/B), where {lambda} is a radial ''mixing length''. We estimate E{sub Up-Tack} from the available free energy composed of two terms, {delta}W = {delta}W{sub 0} + {delta}W{sub 1}, the first term, {delta}W{sub 0}, is the usual stabilizing term in a magnetic well, or an ''average'' well, if the magnetic moment {mu} and the longitudinal invariant J are conserved. The term {delta}W, accounts for violations of adiabatic invariance. We estimate it from nonlinear thermodynamics. There can be a large positive contribution to {delta}W from the relaese of thermal energy in a manner analogous to expansion cooling of a gas, which accounts for anomalous diffusion in several experiments where d