Articoli di riviste: "Lower-Hybrid plasma resonance"

1

Kostrov, A. V., A. V. Strikovskiy e A. V. Shashurin. "Plasma Turbulence near the Lower Hybrid Resonance". Plasma Physics Reports 27, n. 2 (febbraio 2001): 137–42. http://dx.doi.org/10.1134/1.1348491.

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Kim, Hwa-Min, e Young-Dae Jung. "Pair Annihilation Effects on Lower Hybrid Oscillation in Semi-Bounded Magnetized Dusty Pair Plasmas". Zeitschrift für Naturforschung A 61, n. 12 (1 dicembre 2006): 667–71. http://dx.doi.org/10.1515/zna-2006-1208.

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The electron-positron pair annihilation effects on the electrostatic hybrid resonance oscillation are investigated in semi-bounded magnetized dusty pair plasmas. The surface wave dispersion relation is obtained by the plasma dielectric function with the specular reflection condition. The result shows the existence lower hybrid resonance oscillation modes in semi-bounded dusty pair plasmas. It is found that the electron-positron annihilation events enhance the lower hybrid resonance oscillation frequency. It is also found that the lower hybrid resonance frequency decreases with increasing the ratio of the positron density to the electron density. In addition, the lower hybrid resonance frequency decreases with increasing the strength of the magnetic field

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BINGHAM, R., R. A. CAIRNS, I. VORGUL e V. D. SHAPIRO. "Lower-hybrid waves generated by anomalous Doppler resonance in auroral plasmas". Journal of Plasma Physics 76, n. 3-4 (21 gennaio 2010): 539–46. http://dx.doi.org/10.1017/s002237780999078x.

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AbstractThis paper describes some aspects of lower-hybrid wave activity in space plasmas. Lower-hybrid waves are particularly important since they can transfer energy efficiently between electrons and ions in a collisionless magnetized plasma. We consider the ‘fan’ or anomalous Doppler resonance instability driven by energetic electron tails and show that it is responsible for the generation of lower-hybrid waves. We also demonstrate that observations of their intensity are sufficient to drive the modulational instability.

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Grabbe, Crockett L. "Resonance cone structure in a warm inhomogeneous bounded plasma with lower-hybrid resonance layers". Journal of Plasma Physics 33, n. 3 (giugno 1985): 321–57. http://dx.doi.org/10.1017/s0022377800002555.

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The problem of the wave fields excited by a gap source at the edge of an inhomogeneous, magnetized plasma with a pair of lower-hybrid resonance layers present and bounded by conducting walls is solved. The approach used is that of a solution as a sum of multiply-reflected extraordinary mode and ion-thermal resonance cones as an alternative to the guided-wave mode approach. This is achieved by dividing up the plasma into cross-sections where WKB solutions are valid, and into lower-hybrid resonance layers where asymptotic methods are employed and connexion coefficients between each region are obtained. A diagrammatic scheme for writing the solution is introduced which can in principle be used to write down the solution for any problem of this general type once the connexion coefficients across a resonance layer have been determined via asymptotic analysis. This allows a determination in great detail of the structure and properties of the resonance cones in our model and the way they transform across the back-to-back hybrid layers. Evanescent resonance cones are found to exist in the high-density region between the hybrid resonance layers and tunnel through to the other side, maintaining their general structure if the layer is relatively thin.

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MJØLHUS, E. "Parametric instabilities of trapped upper-hybrid oscillations". Journal of Plasma Physics 58, n. 4 (dicembre 1997): 747–69. http://dx.doi.org/10.1017/s0022377897005886.

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Parametric instabilities of upper-hybrid oscillations trapped in a plasma density depletion across an ambient magnetic field are investigated. Approximate dispersion relations are derived, which lead to the identification of two parametric instabilities of the localized upper-hybrid bounded wave structure. Both are related to trapped upper-hybrid oscillation resonances. The first is a decay to a frequency of a trapped wave resonance, downshifted from the applied frequency, where the downshift must be slightly larger than the lower-hybrid frequency. The second instability can exist when the applied frequency is slightly below the arithmetic mean of the frequencies of two trapped oscillation resonances; then the antiStokes component of one is in resonance with the Stokes component of the other. Both slab and two-dimensional geometries are considered.

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6

Shklyar, David R., e Haruichi Washimi. "Lower hybrid resonance wave excitation by whistlers in the magnetospheric plasma". Journal of Geophysical Research 99, A12 (1994): 23695. http://dx.doi.org/10.1029/94ja01956.

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7

POPEL, S. I. "Plasma stochasticity and modulational interactions of waves associated with lower-hybrid resonance". Journal of Plasma Physics 57, n. 2 (febbraio 1997): 363–71. http://dx.doi.org/10.1017/s0022377896004734.

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The stochastic properties of a plasma are taken into account in the consideration of the modulational interactions of waves associated with lower-hybrid (LH) resonance. The limits of applicability of the theory of weak plasma turbulence in the description of the modulational processes are found. It is demonstrated that the development of the modulational instability of waves with frequencies at the LH resonance results in a rapid decrease in stochasticity. This effect is associated with the formation of coherent structures due to the modulational interactions. Eventually a state with local minima of entropy in places where the coherent structures are located is formed. The description of the interaction between waves and particles in the coherent structures is discussed.

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Sharma, P. K., D. Raju, S. K. Pathak, R. Srinivasan, K. K. Ambulkar, P. R. Parmar, C. G. Virani et al. "Current drive experiments in SST1 tokamak with lower hybrid waves". Nuclear Fusion 62, n. 5 (28 marzo 2022): 056020. http://dx.doi.org/10.1088/1741-4326/ac4297.

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Abstract The steadystate superconducting tokamak (SST1) is aimed to demonstrate long pulse plasma discharges employing non-inductive current drive by means of lower hybrid current drive (LHCD) system. The major and minor radius of the machine is 1.1 m and 0.2 m, respectively. The LHCD system for SST1 comprises of klystrons, each rated for 0.5 MW-CW rf power at a frequency of 3.7 GHz. The grill antenna comprises of two rows, each row accommodating 32 waveguide elements. Electron cyclotron resonance breakdown assisted Ohmic plasma is formed in SST1 to overcome the issues associated with low loop voltage start-ups. With recent modifications in the poloidal coils configuration, even with narrow EC pulse (∼50 ms), good repeatable and consistent Ohmic plasmas could be produced which helped in carrying out LHCD current drive experiments on SST1. These experiments demonstrated both fully as well as partially driven non-inductive plasma current in SST1 tokamak. Discharges with zero loop voltages were obtained. The interaction of lower hybrid waves with plasma and generation of suprathermal electrons could be established using energy spectra measured by CdTe detectors. Various other signatures like drop in loop voltages, negative loop voltages, spikes in hard x-rays and increase in second harmonic ECE signal, further confirmed the current drive by LHW’s. The beneficial effect of LHW’s in suppressing hard x-rays was also demonstrated in these experiments. The longest discharge of ∼650 ms could be obtained in SST1 with the help of LHW’s. In this paper, the experimental results obtained with LHCD experiments on SST1 is reported and discussed in more details.

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Kato, Y., W. Kubo, S. Harisaki, M. Anan, K. Tsuda, K. Sato, I. Owada e T. Maenaka. "Cutoff limitation of left-hand polarization wave and candidates for further enhanced producing multicharged ions on ECRIS". Journal of Physics: Conference Series 2244, n. 1 (1 aprile 2022): 012001. http://dx.doi.org/10.1088/1742-6596/2244/1/012001.

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Abstract Based on experimentally obtained plasma parameters in an electron cyclotron resonance (ECR) ion source (ECRIS) and theoretical considerations, it is turned out the essential factor that is currently presumed to define the increase in multicharged ion current in ECRIS is not simply the density limit of ordinary wave and right-hand cutoffs, but is also higher density one of left-hand cutoff. There are two response guidelines that can be considered to make it possible to overcome limitations, except for the conventional simply increasing the frequency and the magnetic field strength. One is advanced high-frequency resonance, i.e., upper-hybrid resonance (UHR), which is conversion from electromagnetic to electrostatic wave essentially without cutoff. The others are due to the introduction of lower frequency waves than ECR’s one, which has no density limit in a more essential sense. The latter is the introduction of lower-hybrid resonance (LHR) or ion cyclotron resonance (ICR). We will describe experimentally obtained plasma parameters, and will discuss these candidate applications.

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10

Berro, E. A., e G. J. Morales. "Excitation of the lower-hybrid resonance at the plasma edge by ICRF couplers". IEEE Transactions on Plasma Science 18, n. 1 (1990): 142–48. http://dx.doi.org/10.1109/27.45517.

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Sharma, P. K., S. L. Rao, K. Mishra, R. G. Trivedi e D. Bora. "Characteristics of electron cyclotron resonance plasma formed by lower hybrid current drive grill antenna". Pramana 70, n. 3 (marzo 2008): 503–16. http://dx.doi.org/10.1007/s12043-008-0065-5.

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12

Kato, Y., S. Harisaki, W. Kubo, Y. Fujimura e K. Iwahara. "Initial Experimental Results on Ion Cyclotron Resonance Heating Selectively Mixed Low Z Ions to Enhance Production Efficiency of Multicharged Ions on Electron Cyclotron Resonance Ion Source". Journal of Physics: Conference Series 2743, n. 1 (1 maggio 2024): 012002. http://dx.doi.org/10.1088/1742-6596/2743/1/012002.

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Abstract According to the accessibility conditions of wave propagation in the magnetized plasma of an electron cyclotron resonance (ECR) ion source (ECRIS), it is speculated that the essential factor that determines the limitations in the multiply charged ion currents is the left-hand polarization wave cutoff (L-cutoff). It is necessary to overcome this limitation, we proposed the introduction of ion cyclotron resonance (ICR) or lower hybrid resonance (LHR) by lower frequency waves. We conduct heating low-mass ions selectively in enhanced producing multiply charged ion by mixing low-mass element gas, which has been conventionally performed in ECRIS, or relaxation of the potential well based on the existence of resonant electron particles by ECR. This paper will describe the initial experimental results of ICR application by introducing low-frequency RF electromagnetic waves in the ECRIS.

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13

Legostaeva, Yuliya, Alexei Shindin e Savely Grach. "Response of ionospheric electron density profile to the action of powerful HF radio-wave radiation". Solnechno-Zemnaya Fizika 8, n. 3 (30 settembre 2022): 74–81. http://dx.doi.org/10.12737/szf-83202211.

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Using electron density and temperature equations, we have modeled the dynamics of the electron density profile in the ionosphere due to the expulsion of plasma from localization regions of plasma waves, pumped by high-power HF radio waves, i.e. wave reflection and upper hybrid resonance regions. Causes of the ionospheric plasma expulsion are an increase in the gas-kinetic pressure due to the ohm heating of electrons by plasma waves, and the high-frequency pressure of plasma waves (ponderomotive expulsion). We have established that the ponderomotive expulsion develops more rapidly and is responsible for the formation of local regions of plasma density depletion near plasma resonances, whereas the gas-kinetic pressure increase is responsible for the formation of lower-density region, which is slower in time and more extended and smoother in height. The results obtained qualitatively agree with the data from the experiment conducted at the HAARP facility in 2014.

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Legostaeva, Yuliya, Alexei Shindin e Savely Grach. "Response of ionospheric electron density profile to the action of powerful HF radio-wave radiation". Solar-Terrestrial Physics 8, n. 3 (30 settembre 2022): 69–75. http://dx.doi.org/10.12737/stp-83202211.

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Using electron density and temperature equations, we have modeled the dynamics of the electron density profile in the ionosphere due to the expulsion of plasma from localization regions of plasma waves, pumped by high-power HF radio waves, i.e. wave reflection and upper hybrid resonance regions. Causes of the ionospheric plasma expulsion are an increase in the gas-kinetic pressure due to the ohm heating of electrons by plasma waves, and the high-frequency pressure of plasma waves (ponderomotive expulsion). We have established that the ponderomotive expulsion develops more rapidly and is responsible for the formation of local regions of plasma density depletion near plasma resonances, whereas the gas-kinetic pressure increase is responsible for the formation of lower-density region, which is slower in time and more extended and smoother in height. The results obtained qualitatively agree with the data from the experiment conducted at the HAARP facility in 2014.

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15

Krämer, M., N. Sollich e J. Dietrich. "Anomalous transport and anomalous heating due to lower-hybrid wave fields". Journal of Plasma Physics 39, n. 3 (giugno 1988): 447–74. http://dx.doi.org/10.1017/s0022377800026751.

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The microscopic and macroscopic behaviours of a linear reflex discharge in the presence of low-frequency turbulence are investigated under the action of moderate lower-hybrid wave power. The frequency and wavenumber spectra of both the low-frequency fluctuations and the high-frequency waves are measured using a correlation-analysis technique with two probes. The low-frequency fluctuations may be attributed to drift-wave turbulence. The fluctuation level is raised when RF power is coupled to the plasma, thus leading to considerably enhanced radial transport. The coupling between low-frequency fluctuations and high-frequency waves can be seen clearly from the spectra. The high-frequency wavenumber spectra measured inside the antenna are in reasonable agreement with the lower-hybrid wave dispersion. However, the wavenumbers observed in the lower-hybrid resonance region outside the antenna are – in contrast with expectation – not larger than in the plasma edge region. From the electric-field energy-density spectra and from measurements of the density and the temperatures, a detailed energy balance can be performed. The calculated heating rates are anomalously large for both the electrons and the ions. The absorption processes, relevant for the present experiment, are discussed.

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SHEN LIN-FANG e YU GUO-YANG. "THE EFFECT OF ION CYCLOTRON RESONANCE HEATING ON LOWER HYBRID CURRENT DRIVE IN TOKAMAK PLASMA". Acta Physica Sinica 41, n. 4 (1992): 587. http://dx.doi.org/10.7498/aps.41.587.

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17

Pasmanik, D. L., A. G. Demekhov, V. Yu Trakhtengerts, E. E. Titova e M. J. Rycroft. "Propagation of lower hybrid resonance waves in depleted-plasma regions in the upper auroral ionosphere". Radiophysics and Quantum Electronics 52, n. 4 (aprile 2009): 252–61. http://dx.doi.org/10.1007/s11141-009-9134-y.

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18

Shevchenko, V. I., e V. L. Galinsky. "Stability of the strahl electron distribution function and its dynamics". Nonlinear Processes in Geophysics 17, n. 5 (26 ottobre 2010): 593–97. http://dx.doi.org/10.5194/npg-17-593-2010.

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Abstract. It is shown that core-strahl electron system in the solar wind plasma is unstable with respect to excitation of the lower hybrid waves at anomalous Doppler resonance due to anisotropy of the strahl electron velocity distribution. Dynamics of the strahl electron distribution due to interaction with excited waves is studied.

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Neubert, T., G. Holmgren, E. Ungstrup e K. Melgård. "Waves with harmonic structure below and above the lower hybrid resonance observed on the CENTAUR 35.001 and 35.002 rockets". Canadian Journal of Physics 64, n. 10 (1 ottobre 1986): 1437–45. http://dx.doi.org/10.1139/p86-254.

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Measurements obtained from the 0- to 10-kHz electric-wave experiment and the 0- to 4.2-kHz electron-density fluctuation experiment on the CENTAUR 35.001 and 35.002 rockets launched in December 1981 are presented. The observations include (i) spectacular narrow-banded signals with harmonic structure related to the proton gyrofrequency. The bands are observed both below and above the lower hybrid frequency, from 2 to 10 kHz, and are modulated in frequency during a rocket spin, typically by 2 kHz. The character of the signals indicate that they are generated by the presence of the payload in the plasma. The source of free energy remains unidentified; we suggest, however, a perpendicular ion beam emitted by or created by the presence of the payload, generating flute-mode ion cyclotron harmonic waves. (ii) Bursts of harmonic waves are received primarily below 2 kHz. The fundamental frequency of these emissions varies over a large range, from 47 to 700 Hz, and is rarely at any of the characteristic frequencies of the plasma. (iii) Waves with a clear lower cutoff at the lower hybrid frequency are also observed. The lower hybrid frequency estimated from magnetic field and density measurements and from the wave measurements agree within 6% (500 Hz).

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Li, Miaohui, Handong Xu, Xiaojie Wang, Mao Wang, Bojiang Ding, Weiye Xu, Dajun Wu et al. "Plasma heating and improvement of lower hybrid current drive efficiency by electron cyclotron waves on EAST". EPJ Web of Conferences 277 (2023): 02003. http://dx.doi.org/10.1051/epjconf/202327702003.

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The electron cyclotron (EC) system on EAST consists of four gyrotrons with a frequency of 140 GHz (second harmonic of the extraordinary mode), each of which is expected to deliver a maximum power of 1.0 MW and be operated at 100-1000 s pulse length. Significant progress in long-pulse operation has been achieved recently, including the pulse duration up to 1056 s with EC power injected into plasma of 0.55 MW and the pulse duration of 310 s with EC power of 1.6 MW (output by 3 gyrotrons). High electron temperature (Te >12 keV) plasma measured by Thomson scattering was produced with the combination of EC and lower hybrid (LH) waves. It is found that the plasma heating effect depends on the EC power location greatly. By adjusting the EC power location, the plasma current profile can be modified. As a consequence of the increment of electron temperature by electron cyclotron resonance heating (ECRH), the lower hybrid current drive (LHCD) efficiency is improved, benefiting for the long-pulse operation. In addition, a synergy effect between EC and LH current drive was observed in steady-state operation on EAST.

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Krafft, C., e A. Volokitin. "Resonant three-wave interaction in the presence of suprathermal electron fluxes". Annales Geophysicae 22, n. 6 (14 giugno 2004): 2171–79. http://dx.doi.org/10.5194/angeo-22-2171-2004.

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Abstract. A theoretical and numerical model is presented which describes the nonlinear interaction of lower hybrid waves with a non-equilibrium electron distribution function in a magnetized plasma. The paper presents some relevant examples of numerical simulations which show the nonlinear evolution of a set of three waves interacting at various resonance velocities with a flux of electrons presenting some anisotropy in the parallel velocity distribution (suprathermal tail); in particular, the case when the interactions between the waves are neglected (for sufficiently small waves' amplitudes) is compared to the case when the three waves follow a resonant decay process. A competition between excitation (due to the fan instability with tail electrons or to the bump-in-tail instability at the Landau resonances) and damping processes (involving bulk electrons at the Landau resonances) takes place for each wave, depending on the strength of the wave-wave coupling, on the linear growth rates of the waves and on the modifications of the particles' distribution resulting from the linear and nonlinear wave-particle interactions. It is shown that the energy carried by the suprathermal electron tail is more effectively transfered to lower energy electrons in the presence of wave-wave interactions.

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Kougblénou, S., G. Lointier, P. M. E. Décréau, J. G. Trotignon, J. L. Rauch, X. Vallières, P. Canu, A. Masson e J. Pickett. "Lower hybrid resonances stimulated by the four CLUSTER relaxation sounders deep inside the plasmasphere: observations and inferred plasma characteristics". Annales Geophysicae 29, n. 11 (9 novembre 2011): 2003–18. http://dx.doi.org/10.5194/angeo-29-2003-2011.

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Abstract. The frequency range of the WHISPER relaxation sounder instrument on board CLUSTER, 4–80 kHz, has been chosen so as to encompass the electron gyro-frequency, Fce, and the electron plasma frequency, Fp, in most regions to be explored. Measurement of those frequencies, which are triggered as resonances by the sounder, provides a direct estimation of in situ fundamental plasma characteristics: electron density and magnetic field intensity. In the late mission phase, CLUSTER penetrated regions deep inside the plasmasphere where Fce and Fp are much higher than the upper frequency of the sounder's range. However, they are of the right order of magnitude as to place the lower hybrid frequency, Flh, in the 4–15 kHz band. This characteristic frequency, placed at a resonance of the medium, is triggered by the sounder's transmitter and shows up as an isolated peak in the received spectrum, not present in spectra of naturally occuring VLF waves. This paper illustrates, from analysis of case events, how measured Flh values give access to a plasma diagnostic novel of its kind. CLUSTER, travelling along its orbit, encounters favourable conditions where Fce is increasing and Fp decreasing, such that Fce/Fp increases from values below unity to values above unity. Measured Flh values thus give access, in turn, to the effective mass, Meff, indicative of plasma ion composition, and to the core plasmasphere electron density value, a parameter difficult to measure. The analysed case events indicate that the estimated quantities (Meff in the 1.0–1.4 range, Ne in the 5 × 102–104 cm−3 range) are varying with external factors (altitude, L value, geomagnetic activity) in a plausible way. Although covering only a restricted region (mid-latitude, low altitude inner plasmasphere), these measurements are available, since late 2009, for all CLUSTER perigee passes not affected by eclipses (on average, roughly a third of a total of ~200 passes per year) and offer multipoint observations previously unavailable in this region.

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Han, Jiangyue, Zhe Gao e S. K. Hansen. "Kinetic theory of parametric decay instabilities near the upper hybrid resonance in plasmas". Physics of Plasmas 30, n. 2 (febbraio 2023): 022104. http://dx.doi.org/10.1063/5.0115517.

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Parametric decay instabilities (PDIs) near the upper hybrid resonance layer are studied with a 1D framework. In a uniform plasma, the kinetic nonlinear dispersion relation of PDI is numerically calculated for parameters corresponding to electron cyclotron heating experiments at the ASDEX-U tokamak, in which O-mode radiation was converted to X-mode radiation by reflection from the high-field sidewall. The forward scattering processes driven by X-mode and linearly converted electron Bernstein waves (EBWs) are investigated and found to lead to a primary PDI where the pump waves decay into lower hybrid waves and sideband EBWs. A frequency shift of 930 MHz is obtained for the sideband EBWs in the primary PDIs. Subsequently, the sideband EBWs can decay into a low-frequency ion Bernstein quasi-mode (IBQM) and a secondary EBW, where the dominant forward scattering channel is the first-order IBQM with a frequency close to twice the ion cyclotron frequency. The decay channels obtained by numerical calculation can explain the characteristics of the signal observed in ASDEX-U experiments. The threshold of the pump electric field strength required to excite the primary PDI in the presence of plasma inhomogeneity is also estimated.

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Kato, Yushi, Shuhei Harisaki, Wataru Kubo, Kouki Iwahara e Yushi Fujimura. "Initial Experimental Results of Producing Multicharged Ions Efficiently by Lower Hybrid Resonance Heating with Exciting Helicon Waves on Electron Cyclotron Resonance Ion Source". Journal of Physics: Conference Series 2743, n. 1 (1 maggio 2024): 012004. http://dx.doi.org/10.1088/1742-6596/2743/1/012004.

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Abstract Based on experimental results, we considered the accessibility conditions for wave propagation in the magnetized plasma in an electron cyclotron resonance (ECR) ion source (ECRIS), and proposed introducing electromagnetic waves with frequencies lower than those of ECR. We generate the lower hybrid resonance (LHR) in the ECRIS by the electric field of the extra-ordinary mode (X-mode) on the helicon wave which additionally heat the electrons, and then it was conducted to improve the efficiency of multicharged ion generation successfully in over density condition. The electron energy distribution function obtained by the probe measurement shows an increase in the high-energy region in the corresponding LHR region. In this paper, for the first time we describe the initial experimental results on enhanced production of multicharged ions by the LHR of the low-frequency RF electromagnetic waves into the ECRIS.

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TOIDA, Mieko, Hiroe IGAMI, Kenji SAITO, Tsuyoshi AKIYAMA, Shuji KAMIO e Ryosuke SEKI. "Simulation Study of Energetic Ion Driven Instabilities near the Lower Hybrid Resonance Frequency in a Plasma with Increasing Density". Plasma and Fusion Research 14 (19 giugno 2019): 3401112. http://dx.doi.org/10.1585/pfr.14.3401112.

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Liu, Guan-Nan, Xin-Xia LI, Hong-Bo Liu e Ai-Ping Sun. "Synergistic current drive of herical wave and lower hybrid wave current wave in HL-2M Tokamak device". Acta Physica Sinica 72, n. 24 (2023): 245202. http://dx.doi.org/10.7498/aps.72.20231077.

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Non-inductive current drive plays a crucial role in tokamak, especially for its steady state operations. Recently, the helicon wave (HW) has been regarded as a promising tool for driving off-axis plasma current in reactor-grade machine. The lower-hybrid wave (LHW) is the most effective radio-frequency current drive method, however, it has the drawback, which is limited by the conditions of wave accessibility in the high parameter tokamak, making the wave power usually damped at the plasma edge. HW can spiral towards the plasma centre directly under a high electron density. To obtain a long pulse steady state operation of reactor tokamak, the complementarity of HW and LHW in the aspect of driven current distribution in the high parameter tokamak is considered. The synergy current drive of the HW and the LHW is studied numerically in the steady-state scenario of HL-2M. According to the fast wave dispersion relation of plasma, the HW parameters, including its wave frequency and launched parallel refractive index, are obtained firstly. Results of GENRAY code simulation show that a single pass wave power absorption of the HW can be obtained generally through the electron Landau damping and transit time magnetic pumping effects. On the other hand, the LHW parameters are adopted from the equipped system on the machine. Results of single pass wave absorption are also obtained in the case of LHW. And then, the synergy effects of HW and LHW are studied numerically based on the GENRAY/CQL3D models. The cooperation of these two waves results in a broad plasma current distribution along the radial direction (<inline-formula><tex-math id="M2">\begin{document}$\rho = $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20231077_M2.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20231077_M2.png"/></alternatives></inline-formula>0.2—0.9) in the machine. Taking the electron distribution functions of these waves into account, it is clear that the electrons are accelerated by the HW in the parallel magnetic field direction, resulting in more electrons entering the region of LHW resonance area. As the consequence, a net plasma current appears. Furthermore, a fine-grained parametric scan is performed by changing the launched parallel refractive index of HW, and the results indicate that positive synergy effects can be generally observed once the related wave current drive profiles are overlapped. Finally, the synergy factor is shown to be proportional to this overlap and reaches its maximum value of 1.18 in HL-2M.

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Senstius, Mads G., Simon J. Freethy, Joe Allen e Stefan K. Nielsen. "A radiometer to diagnose parametric instabilities during linear excitation of electron Bernstein waves in the Mega Amp Spherical Tokamak (MAST) Upgrade". Review of Scientific Instruments 93, n. 10 (1 ottobre 2022): 103522. http://dx.doi.org/10.1063/5.0101785.

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Highly overdense magnetically confined fusion plasmas, such as the Mega Amp Spherical Tokamak (MAST) Upgrade, cannot easily be heated using conventional electron cyclotron resonance heating because high density cutoffs block microwave access to the plasma core. Instead, electromagnetic waves can be coupled to electron Bernstein waves (EBWs) through the O-X-B mode coupling scheme, and the EBWs can then be absorbed at higher densities. The excitation of EBWs occurs at the upper hybrid (UH) layer where nonlinear wave interactions, called parametric decay instabilities (PDIs), are known to occur at reduced power thresholds. We present a design for a radiometer to detect PDIs during O-X-B in MAST Upgrade. The radiometer will aid in determining at what power levels PDIs become important as well as inferring various parameters about both electrons and ions near the UH layer. We estimate a gyrotron power density threshold for PDI and expected frequency shifts to be produced in them. The design allows for shifts from several decays involving lower hybrid (LH) waves to be observed.

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Shaposhnikov, V. E., G. V. Litvinenko, V. V. Zaitsev, V. V. Zakharenko e A. A. Konovalenko. "Origin of the zebra structure in the Jovian decameter radio emission". Astronomy & Astrophysics 645 (23 dicembre 2020): A31. http://dx.doi.org/10.1051/0004-6361/202039304.

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Context. We discuss the origin of quasi-harmonic emission bands that have been observed in the dynamic spectra of the Jovian decameter emission. Aims. We aim to show that the interpretation of the observed structure can be based on the effect of double plasma resonance (DPR) at ion cyclotron harmonics. Methods. According to the proposed model, in the extended source in the upper ionosphere of Jupiter, where the DPR condition is satisfied for one of the ion cyclotron frequency harmonics, the ion cyclotron waves are effectively excited at the frequency of the lower hybrid resonance. The observed electromagnetic radiation with a quasi-harmonic structure arises due to scattering of ion cyclotron waves by supra-thermal electrons. Results. Based on the VIP4 magnetic field model, we determine the longitudes at which the source of the considered radiation can be located. The obtained estimates of the plasma density and its height distribution in the source, as well as the energies of emitting ions and scattering electrons provide information about the plasma parameters in the upper ionosphere of Jupiter. Furthermore, these estimates are in good agreement with the observational data.

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29

Lundin, B. V., e C. Krafft. "On the dispersion law of low-frequency electron whistler waves in a multi-ion plasma". Annales Geophysicae 26, n. 6 (11 giugno 2008): 1605–15. http://dx.doi.org/10.5194/angeo-26-1605-2008.

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Abstract. A new and simple dispersion law for extra-low-frequency electron whistler waves in a multi-ion plasma is derived. It is valid in a plasma with finite ratio ωc/ωpe of electron gyro-to-plasma frequency and is suitable for wave frequencies much less than ωpe but well above the gyrofrequencies of most heavy ions. The resultant contribution of the ions to the dispersion law is expressed by means of the lower hybrid resonance frequency, the highest ion cutoff frequency and the relative content of the lightest ion. In a frequency domain well above the ions' gyrofrequencies, this new dispersion law merges with the "modified electron whistler dispersion law" determined in previous works by the authors. It is shown that it fits well to the total cold plasma electron whistler dispersion law, for different orientations of the wave vectors and different ion constituents, including negative ions or negatively charged dust grains.

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30

LUNDIN, B. V., e C. KRAFFT. "Modified electron whistler dispersion law". Journal of Plasma Physics 67, n. 2-3 (aprile 2002): 149–61. http://dx.doi.org/10.1017/s0022377801001301.

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A modified electron whistler dispersion law is derived in the cold-plasma approximation for analytical treatment and simplified numerical calculations of wave propagation in a wide range of ratios ωc/ωp of electron gyro- to plasma frequencies if the wave frequency is much less than ωp. The net contribution of ions to the wave dispersion law is expressed through the value of the lower-hybrid resonance frequency ωlhr only. This approximate dispersion law is valid in a wide frequency domain, that is, from the range of ωlhr until the domain where the contribution of ions can be neglected. A comparison of geometrical-optics ray trajectories calculated by the use of modified and total cold-plasma electron whistler dispersion laws is presented for the case of the Earth's plasma environment. Computer simulations of dynamical spectra of whistler waves excited by lightning discharges and registered in remote regions of the Earth's plasmasphere reveal good numerical stability of the developed ray-tracing code.

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31

Maxworth, Ashanthi, Glenn Hussey e Mark Gołkowski. "Coexistence of Lightning Generated Whistlers, Hiss and Lower Hybrid Noise Observed by e-POP (SWARM-E)–RRI". Atmosphere 11, n. 2 (8 febbraio 2020): 177. http://dx.doi.org/10.3390/atmos11020177.

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Whistler mode waves play a major role in regulating the lifetime of trapped electrons in the Earth’s radiation belts. Specifically, interaction with whistler mode hiss waves is one of the mechanisms that maintains the slot region between the inner and outer radiation belts. The generation mechanism of hiss is a topic still under debate with at least three prominent theories present in the literature. Lightning generated whistlers in their ducted or non-ducted modes are considered to be one of the possible sources of hiss. We present a study of new observations from the Radio Receiver Instrument (RRI) on the Enhanced Polar Outflow Probe (ePOP: also known as SWARM-E). RRI consists of two orthogonal dipole antennas, which enables polarization measurements, when the satellite boresight is parallel to the geomagnetic field. Here we present 105 ePOP - RRI events from 2014–2018, in which lightning whistlers(75) and hiss waves(39) were observed. In more than 50% of those whistler observations, hiss found to co-exist. Moreover, the whistler observations are correlated with observations of wave power at the lower-hybrid resonance. The observations and a whistler mode ray-tracing study suggest that multiple-hop lightning induced whistlers can be a source of hiss and plasma instabilities in the magnetosphere.

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32

Krafft, C., e A. Volokitin. "Interaction of suprathermal solar wind electron fluxes with sheared whistler waves: fan instability". Annales Geophysicae 21, n. 7 (31 luglio 2003): 1393–403. http://dx.doi.org/10.5194/angeo-21-1393-2003.

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Abstract. Several in situ measurements performed in the solar wind evidenced that solar type III radio bursts were some-times associated with locally excited Langmuir waves, high-energy electron fluxes and low-frequency electrostatic and electromagnetic waves; moreover, in some cases, the simultaneous identification of energetic electron fluxes, Langmuir and whistler waves was performed. This paper shows how whistlers can be excited in the disturbed solar wind through the so-called "fan instability" by interacting with energetic electrons at the anomalous Doppler resonance. This instability process, which is driven by the anisotropy in the energetic electron velocity distribution along the ambient magnetic field, does not require any positive slope in the suprathermal electron tail and thus can account for physical situations where plateaued reduced electron velocity distributions were observed in solar wind plasmas in association with Langmuir and whistler waves. Owing to linear calculations of growth rates, we show that for disturbed solar wind conditions (that is, when suprathermal particle fluxes propagate along the ambient magnetic field), the fan instability can excite VLF waves (whistlers and lower hybrid waves) with characteristics close to those observed in space experiments.Key words. Space plasma physics (waves and instabilities) – Radio Science (waves in plasma) – Solar physics, astrophysics and astronomy (radio emissions)

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33

Jiřiček, F., D. R. Shklyar e P. Třiska. "LHR effects in nonducted whistler propagation – new observations and numerical modelling". Annales Geophysicae 19, n. 2 (28 febbraio 2001): 147–57. http://dx.doi.org/10.5194/angeo-19-147-2001.

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Abstract. VLF-ELF broadband measurements onboard the MAGION 4 and 5 satellites at heights above 1 Re in plasmasphere provide new data on various known phenomena related to ducted and nonducted whistler wave propagation. Two examples are discussed: magnetospherically reflected (MR) whistlers and lower hybrid resonance (LHR) noise band. We present examples of rather complicated MR whistler spectrograms not reported previously and argue the conditions for their generation. Analytical consideration, together with numerical modelling, yield understanding of the main features of those spectrograms. LHR noise band, as well as MR whistlers, is a phenomenon whose source is the energy propagating in the nonducted way. At the plasmaspheric heights, where hydrogen (H+) is the prevailing ion, and electron plasma frequency is much larger than gyrofrequency, the LHR frequency is close to its maximumvalue in a given magnetic field. This frequency is well followed by the observed noise bands. The lower cutoff frequency of this band is somewhat below that maximum value. The reason for this, as well as the possibility of using the LHR noise bands for locating the plasma through position, are discussed.Key words. Magnetospheric physics (plasmasphere; wave propagation)

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34

López, Elvis O., Fábio O. Borges, Alexandre M. Rossi, Ricardo M. O. Galvão e Alexandre Mello. "The role of lower hybrid resonance and helicon waves excitations in a magnetized plasma for coating production of complex crystalline structures as hydroxyapatite". Vacuum 146 (dicembre 2017): 233–45. http://dx.doi.org/10.1016/j.vacuum.2017.10.002.

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35

McKENZIE, JAMES F. "Wave dynamics of an electrojet: generalized Farley–Buneman instability". Journal of Plasma Physics 73, n. 5 (ottobre 2007): 701–13. http://dx.doi.org/10.1017/s002237780600612x.

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AbstractIn this paper we generalize the classical Farley–Buneman (FB) instability to include space-charge effects and finite electron inertia. The former effect makes the ion-acoustic wave dispersive with the usual resonance appearing at the ion plasma frequency, but other than that the structure of the FB instability remains intact. However, the inclusion of the latter, finite electron inertia, gives rise to the propagating electron-cyclotron mode, albeit modified by collisions. In the presence of differential electron streaming relative to the ions, the interaction between this mode, attempting to propagate against the stream, but convected forward by the stream, and a forward propagating ion-acoustic mode, gives rise to a new instability distinct from the FB instability. The process may be thought of in terms of the coupling between negative energy waves (electron-cyclotron waves attempting to propagate against the stream) and positive energy waves (forward propagating ion-acoustic waves). In principle, the instability simply requires super-ion acoustic streaming electrons and the corresponding growth rates are of the order of one half of the lower hybrid frequency, which are faster than the corresponding FB growth rates. For conditions appropriate to the middle day-side E-region this instability excites a narrow band of frequencies just below the ion plasma frequency. Its role in the generation of electrojet irregularities may be as important as the classical FB instability.

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36

BINGHAM, R., J. M. DAWSON e V. D. SHAPIRO. "Particle acceleration by lower-hybrid turbulence". Journal of Plasma Physics 68, n. 3 (aprile 2002): 161–72. http://dx.doi.org/10.1017/s0022377802001939.

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We investigate particle acceleration by strong lower-hybrid turbulence produced by the relaxation of an energetic perpendicular ion ring distribution. Ion ring distributions are associated with counterstreaming plasma flows in a magnetic field, and are found at perpendicular shocks as a result of ion reflection from the shock surface. Using a 2½D particle-in-cell (PIC) code that is fully electromagnetic and relativistic, we show that the ion ring is unstable to the generation of strong plasma turbulence at the lower-hybrid resonant frequency. The lower-hybrid wave turbulence collapses in configuration space, producing density cavities. The collapse of the cavities is halted by particle acceleration, producing energetic electron and ion tails. For solar flare plasmas with temperatures of 1 keV and a ratio of the plasma frequency to the electron cyclotron frequency of ½, we demonstrate electron acceleration to energies up to MeV, while the ions are accelerated to energies in the region of several MeV.

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37

Kim, Kyung-Chan. "Empirical Modeling of the Global Distribution of Magnetosonic Waves with Ambient Plasma Environment using Van Allen Probes". Journal of Astronomy and Space Sciences 39, n. 1 (marzo 2022): 11–22. http://dx.doi.org/10.5140/jass.2022.39.1.11.

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It is suggested that magnetosonic waves (also known as equatorial noise) can scatter radiation belt electrons in the Earth’s magnetosphere. Therefore, it is important to understand the global distribution of these waves between the proton cyclotron frequency and the lower hybrid resonance frequency. In this study, we developed an empirical model for estimating the global distribution of magnetosonic wave amplitudes and wave normal angles. The model is based on the entire mission period (approximately 2012–2019) of observations of Van Allen Probes A and B as a function of the distance from the Earth (denoted by L*), magnetic local time (MLT), magnetic latitude (λ), and geomagnetic activity (denoted by the Kp index). In previous studies the wave distribution inside and outside the plasmasphere were separately investigated and modeled. Our model, on the other hand, identifies the wave distribution along with the ambient plasma environment—defined by the ratio of the plasma frequency (fpe) to the electron cyclotron frequency (fce)—without separately determining the wave distribution according to the plasmapause location. The model results show that, as Kp increases, the dayside wave amplitude in the equatorial region intensifies. It thereby propagates the intense region towards the wider MLT and inward to L* < 4. In contrast, the fpe/fce ratio decreases with increasing Kp for all regions. Nevertheless, the decreasing aspect differs between regions above and below L* = 4. This finding implies that the particle energy and pitch angle that magnetosonic waves can effectively scatter vary depending on the locations and geomagnetic activity. Our model agrees with the statistically observed wave distribution and ambient plasma environment with a coefficient of determination of > 0.9. The model is valid in all MLTs, 2 ≤ L* < 6, |λ| < 20°, and Kp ≤ 6.

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38

Tang, Binbin, Wenya Li, Chi Wang, Lei Dai, Yuri Khotyaintsev, Per-Arne Lindqvist, Robert Ergun et al. "Magnetic depression and electron transport in an ion-scale flux rope associated with Kelvin–Helmholtz waves". Annales Geophysicae 36, n. 3 (15 giugno 2018): 879–89. http://dx.doi.org/10.5194/angeo-36-879-2018.

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Abstract. We report an ion-scale magnetic flux rope (the size of the flux rope is ∼ 8.5 ion inertial lengths) at the trailing edge of Kelvin–Helmholtz (KH) waves observed by the Magnetospheric Multiscale (MMS) mission on 27 September 2016, which is likely generated by multiple X-line reconnection. The currents of this flux rope are highly filamentary: in the central flux rope, the current flows are mainly parallel to the magnetic field, supporting a local magnetic field increase at about 7 nT, while at the edges the current filaments are predominantly along the antiparallel direction, which induce an opposing field that causes a significant magnetic depression along the axis direction (> 20 nT), meaning the overall magnetic field of this flux rope is depressed compared to the ambient magnetic field. Thus, this flux rope, accompanied by the plasma thermal pressure enhancement in the center, is referred to as a crater type. Intense lower hybrid drift waves (LHDWs) are found at the magnetospheric edge of the flux rope, and the wave potential is estimated to be ∼ 17 % of the electron temperature. Though LHDWs may be stabilized by the mechanism of electron resonance broadening, these waves could still effectively enable diffusive electron transports in the cross-field direction, corresponding to a local density dip. This indicates LHDWs could play important roles in the evolution of crater flux ropes. Keywords. Magnetospheric physics (magnetopause, cusp, and boundary layers; solar wind–magnetosphere interactions)

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39

Cho, Suwon. "The role of the lower hybrid resonance in helicon plasmas". Physics of Plasmas 7, n. 1 (gennaio 2000): 417–23. http://dx.doi.org/10.1063/1.873813.

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40

Parrot, M., O. Santolík, N. Cornilleau-Wehrlin, M. Maksimovic e C. Harvey. "Magnetospherically reflected chorus waves revealed by ray tracing with CLUSTER data". Annales Geophysicae 21, n. 5 (31 maggio 2003): 1111–20. http://dx.doi.org/10.5194/angeo-21-1111-2003.

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Abstract. This paper is related to the propagation characteristics of a chorus emission recorded simultaneously by the 4 satellites of the CLUSTER mission on 29 October 2001 between 01:00 and 05:00 UT. During this day, the spacecraft (SC) 1, 2, and 4 are relatively close to each other but SC3 has been delayed by half an hour. We use the data recorded aboard CLUSTER by the STAFF spectrum analyser. This instrument provides the cross spectral matrix of three magnetic and two electric field components. Dedicated software processes this spectral matrix in order to determine the wave normal directions relative to the Earth’s magnetic field. This calculation is done for the 4 satellites at different times and different frequencies and allows us to check the directions of these waves. Measurements around the magnetic equator show that the parallel component of the Poynting vector changes its sign when the satellites cross the equator region. It indicates that the chorus waves propagate away from this region which is considered as the source area of these emissions. This is valid for the most intense waves observed on the magnetic and electric power spectrograms. But it is also observed on SC1, SC2, and SC4 that lower intensity waves propagate toward the equator simultaneously with the SC3 intense chorus waves propagating away from the equator. Both waves are at the same frequency. Using the wave normal directions of these waves, a ray tracing study shows that the waves observed by SC1, SC2, and SC4 cross the equatorial plane at the same location as the waves observed by SC3. SC3 which is 30 minutes late observes the waves that originate first from the equator; meanwhile, SC1, SC2, and SC4 observe the same waves that have suffered a Lower Hybrid Resonance (LHR) reflection at low altitudes (based on the ray tracing analysis) and now return to the equator at a different location with a lower intensity. Similar phenomenon is observed when all SC are on the other side of the equator. The intensity ratio between magnetic waves coming directly from the equator and waves returning to the equator is between 0.005 and 0.01, which is in agreement with previously published theoretical calculation of the growth rates with the particle distribution seen by GEOS.Key words. Magnetospheric physics (plasma waves and instabilities) – Ionosphere (wave propagation) – Radio science (magnetospheric physics)

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41

Yun, Seok-Min, Jung-Hyung Kim e Hong-Young Chang. "Frequency dependence of helicon wave plasmas near lower hybrid resonance frequency". Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films 15, n. 3 (maggio 1997): 673–77. http://dx.doi.org/10.1116/1.580704.

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42

Bouhram, M., M. Malingre, J. R. Jasperse, N. Dubouloz e J. A. Sauvaud. "Modeling transverse heating and outflow of ionospheric ions from the dayside cusp/cleft. 2 Applications". Annales Geophysicae 21, n. 8 (31 agosto 2003): 1773–91. http://dx.doi.org/10.5194/angeo-21-1773-2003.

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Abstract. In this paper, we consider major ion energization mechanisms in the dayside cusp/cleft region. This includes transverse ion heating by ion cyclotron resonance (ICR), ion energization through structures of field-aligned electric potential drops, and transverse heating by lower hybrid (LH) waves. First, we present and discuss three typical cusp/cleft crossings associated with one of the first two mechanisms mentioned above. Then, we develop a procedure for finding the altitude dependence of ICR heating for any data set in the high-altitude cusp/cleft under the absence of field-aligned potential drops. This has been accomplished using a large set of numerical simulations from a two-dimensional, steady-state, Monte Carlo, trajectory-based code, as discussed in detail in the first companion paper (Bouhram et al., 2003). The procedure is applied and tested successfully for the first two events, by using patterns of ion moments along the satellite track as constraints. Then, we present a statistical study that uses 25 cusp/cleft crossings associated with steady IMF conditions, where ICR heating is expected to occur alone. It is pointed out that the ICR heating increases gradually versus geocentric distance as s 3.3 ± 1.8 . The inferred values of the wave power and the spectral index associated with the component responsible for ICR heating are lower than those characterizing the broad-band, extremely low-frequency (BBELF) turbulence usually observed in the cusp/cleft. This strengthens the idea that more than one wave-mode is contained in the BBELF turbulence, and only a small fraction of the observed turbulence is responsible for ICR heating. Then, we study the occurrence versus magnetic local time (MLT) of field-aligned potential drops. According to previous statistical studies, such structures are not common in the cusp and tend to be associated with the cleft region. We also discuss the effects of LH heating in the cusp on the observed ion distributions. However, this mechanism turns out to be of less importance than ICR heating.Key words. Magnetospheric physics (Auroral phenomena) – Space plasma physics (charged particle motion and acceleration; wave-particle interactions)

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43

Yun, Seokmin, Suwon Cho, George Tynan e Hongyoung Chang. "Density enhancement near lower hybrid resonance layer in m=0 helicon wave plasmas". Physics of Plasmas 8, n. 1 (gennaio 2001): 358–63. http://dx.doi.org/10.1063/1.1332987.

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44

Zhou, Taotao, Nong Xiang, Chunyun Gan, Xueyi Wang, Guozhang Jia, Jiale Chen, Xuemei Zhai e Yueheng Huang. "Particle-in-cell simulations on parametric instability of the lower hybrid wave". Physics of Plasmas 29, n. 10 (ottobre 2022): 102302. http://dx.doi.org/10.1063/5.0104505.

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Lower hybrid (LH) wave is an effective tool for current drive (CD) on tokamak devices. Parametric instability (PI) has always been a troubling phenomenon decreasing the lower hybrid current drive efficiency. In this work, the PI behavior of the LH waves for plasma parameters on the Experimental Advanced Superconducting Tokamak is investigated via first-principle simulation with a two-dimensional full-particle-in-cell method. The PI processes where an LH pump wave decays into another LH sideband and a low-frequency mode [ion sound quasi-mode (ISQM) or ion cyclotron quasi-mode (ICQM)] are observed in simulations. The ICQM-type and ISQM-type decay channels dominate, respectively, in the high- and low-plasma regimes while appearing simultaneously in the intermediate regime, which agrees well with the theoretical prediction by solving the parametric dispersion relation. In addition, for both the decay channels, their LH sidebands are excited with a wide range of parallel refractive index [Formula: see text] up to 30.0, which can resonantly interact with thermal electrons. The resulting electron heating can be enhanced due to overlap of resonances between the electrons and sidebands. Such electron heating not only dissipates the wave energy in the edge plasma but produces a significant portion of fast electrons, which may seriously affect tokamak discharges. The ion cyclotron heating due to the ICQMs is also observed in simulations.

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45

BINGHAM, R., R. BAMFORD, B. J. KELLETT e V. D. SHAPIRO. "Electron energization in lunar magnetospheres". Journal of Plasma Physics 76, n. 6 (20 agosto 2010): 915–18. http://dx.doi.org/10.1017/s0022377810000462.

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AbstractThe interaction of the solar wind with lunar surface magnetic fields produces a bow shock and a magnetosphere-like structure. In front of the shock wave energetic electrons up to keV energies are produced. This paper describes how resonant interactions between plasma turbulence in the form of lower-hybrid waves and electrons can result in field aligned electron acceleration. The turbulent wave fields close to the lower-hybrid resonant frequency are excited most probably by the modified two-stream instability, driven by the solar wind ions that are reflected and deflected by the low shock.

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46

Lesch, H., S. Appl e M. Camenzind. "The Shock Structure in Current-Carrying Jets". Symposium - International Astronomical Union 140 (1990): 438. http://dx.doi.org/10.1017/s0074180900190758.

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We exploite the detailed calculations and observations of the earth bow-shock and suggest that similar collective plasma processes can account for the dissipation in hot spots of extragalactic radiosources. On the base of magnetohydrodynamic models for the origin and propagation of current carrying jets we show that in the terminal shock in hot spots lower hybrid-turbulence is excited. This turbulence driven by drifting electrons in the shock provides the anomalous conductivity required for current closure. Lower-hybrid turbulence is also generated by ion reflection in the upstream plasma. The kinetic energy of these ion beams is partially transformed into lower hybrid wave energy. These waves also determine the ratio of energies taken for plasma heating and particle acceleration. This is due to the fact that lower hybrid waves propagate almost perpendicular to the magnetic fields (large (small) wavenumbers perpendicular (parallel) to the magnetic field), their phase velocity parallel to the B-field are much larger than perpendicular to the field. Therefore electrons and ions are differently coupled to these waves. The resonant interactions of the upstream plasma with these waves leads to strong ion heating and electron acceleration. The ions reach a temperature (Ti ≃ 51011K). The electrons are accelerated up to relativistic energies (γ ≃ 1300).

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47

Sharma, Jyotsna, e Suresh C. Sharma. "Neutral beam driven ion cyclotron instability of lower hybrid wave in a tokamak plasma". AIP Advances 12, n. 8 (1 agosto 2022): 085321. http://dx.doi.org/10.1063/5.0102140.

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The effect of dust grains on the parametric coupling of neutral beam driven ion–cyclotron wave instability with a lower hybrid pump wave is studied. A high amplitude lower hybrid pump, which is launched into a tokamak for heating purposes in the presence of neutral beam driven ion-cyclotron waves, can excite the parametric coupling involving two lower hybrid sidebands. In a tokamak, the lower hybrid waves result in parametric excitation of the ion-cyclotron mode and quasi-modes near the edge when the electron oscillatory velocity is greater than the sound velocity. This parametric coupling increases the growth rate of instability when the lower sideband wave is resonant. Moreover, the presence of dust grains in the tokamak plasma, their radius, and the number density significantly affect the growth rate of the instability, which in turn can affect the advanced stage operations of a tokamak. The growth rate of parametric instability scales with the amplitude of the pump wave. The growth rate is found to be linearly increased with the dust grain density, but it decreased with increasing size of dust grains, which means large sized dust grains stabilize the instability. The theoretical results explained in the present paper are very helpful in explaining the complexity in the plasma properties of a tokamak due to the dust–plasma interactions, which can diminish the performance of the International Thermonuclear Experimental Reactor due to potential safety issues.

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48

Mundhra, Raksha, e P. N. Deka. "Instability of Ion Cyclotron Waves (ICWS) at the Expense of Lower Hybrid Drift Waves (LHDWS) Turbulence Energy". East European Journal of Physics, n. 4 (2 dicembre 2023): 54–65. http://dx.doi.org/10.26565/2312-4334-2023-4-06.

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Instability of ion cyclotron waves(ICWs) is investigated in presence of lower hybrid drift waves(LHDWs) turbulence. Plasma inhomogeneity in the Earth’s magnetopause region supports a range of low frequency drift wave turbulent fields due to gradients in density in different regions of the media. One of these drift phenomena is identified as lower hybrid drift waves (LHDWs) which satisfies resonant conditions ω − k · v = 0. We have considered a nonlinear wave-particle interaction model where the resonant wave that accelerates the particle in magnetopause may transfer its energy to ion cyclotron waves through a modulated field. In spite of the frequency gaps between the two waves, energy can be transferred nonlinearly to generate unstable ion cyclotron waves which always do not satisfy the resonant condition Ω−K · v ≠ 0 and the nonlinear scattering condition Ω − ω − (K − k) · v ̸= 0. Here, ω and Ω are frequencies of the resonant and the nonresonant waves respectively and k and K are the corresponding wave numbers. We have obtained a nonlinear dispersion relation for ion cyclotron waves(ICWs) in presence of lower hybrid drift waves(LHDWs)turbulence. The growth rate of the ion cyclotron waves using space observational data in the magnetopause region has been estimated.

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49

Cho, Suwon. "Propagation and Absorption of Electromagnetic Waves in Inhomogeneous Helicon Plasmas with a Lower Hybrid Resonance Layer". Journal of the Korean Physical Society 58, n. 3 (15 marzo 2011): 461–66. http://dx.doi.org/10.3938/jkps.58.461.

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50

Galeev, A. A., M. A. Malkov e H. J. Völk. "Macroscopic electric fields driven by lower-hybrid turbulence and acceleration of thermal electrons in the foot of quasi-perpendicular shocks". Journal of Plasma Physics 54, n. 1 (agosto 1995): 59–76. http://dx.doi.org/10.1017/s0022377800018341.

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A new mechanism is suggested that draws non-resonant thermal electrons into a higher-velocity range, where they can be effectively accelerated by waves. We argue that the acceleration of a small number of pre-existing resonant particles influences the dynamics of the bulk plasma and results in a macroscopic electric field. The solution for the spatial dependence of this electric field is obtained, and it appears to be a new type of electrostatic shock, which forms only in the presence of background turbulence. This field enriches the region of resonant particles with thermal electrons, which leads to a build-up of an excess of accelerated particles. The number of accelerated particles is calculated. This mechanism appears as a good candidate to explain electron acceleration in the foot of quasi-perpendicular shocks.

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