scholarly journals Interaction of radio frequency waves with cylindrical density filaments: scattering and radiation pressure

2021 ◽  
Vol 87 (6) ◽  
Author(s):  
Spyridon I. Valvis ◽  
Abhay K. Ram ◽  
Kyriakos Hizanidis
Keyword(s):  
Radio Frequency ◽  
Cold Plasma ◽  
Radiation Force ◽  
Edge Plasma ◽  
Lower Hybrid ◽  
Maxwell Stress Tensor ◽  
Ion Cyclotron Waves ◽  
Ion Cyclotron ◽  
Rf Antenna ◽  
The Waves

The propagation of radio-frequency (RF) waves in tokamaks can be affected by filamentary structures, or blobs, that are present in the edge plasma and the scrape-off layer. The difference in the permittivity between the surrounding plasma and interior of a filament leads to reflection, refraction and diffraction of the waves. This, in turn, can affect the power flow into the core of the plasma and reduce the efficiency of heating and/or current generation. The scattering of RF waves, lower hybrid, helicon and ion cyclotron waves, by a single cylindrical filament, embedded in a background plasma, is studied using a full-wave analytical theory developed previously (Ram & Hizanidis, Phys. Plasmas, vol. 23, 2016, 022504). The theory assumes that the plasma in and around a filament is homogeneous and cold. A detailed scattering analysis reveals a variety of common features that exist among the three distinctly different RF waves. These common attributes can be inferred intuitively based on an examination of the cold plasma dispersion relation. The physical intuition is a useful step to understanding experimental observations on scattering, as well as results from simulations that include general forms of edge plasma turbulence. While a filament can affect the propagation of RF waves, the radiation force exerted by the waves can influence the filament. The force on a filament is determined using the Maxwell stress tensor. In 1905, Poynting was the first to evaluate and measure the radiation force on an interface separating two different dielectric media (Poynting, London Edinburgh Dublin Philos. Mag. J. Sci., vol. 9, 1905, pp. 393–406). For ordinary light propagating in vacuum and incident on a glass surface, Poynting noted that the surface is ‘pulled’ towards the vacuum. In a magnetized cold plasma, there are two independent wave modes. Even if only one of these modes is excited by an RF antenna, a filament will couple power to the other mode: a consequence of electromagnetic boundary conditions. This facet of scattering has consequences on the radiation force that go beyond Poynting's seminal contribution. The direction of the force depends on the polarization of the incident wave and on the mode structure of the waves inside and in the vicinity of a filament. It can either pull the filament toward the RF source or push it away. For slow lower hybrid waves, filaments with densities greater than the ambient density are pulled in, while filaments with lower densities are pushed out, thereby enhancing the density in front of the antenna. In the case of fast helicon and ion cyclotron waves, the direction of the force depends on the plasma and wave parameters; in particular, on the ambient density. The radiation force, in all three frequency ranges, is large enough to affect the motion of a filament and could be measured experimentally. This also suggests the possibility of modifying the edge turbulence using RF waves.

scholarly journals Multi-spacecraft determination of wave characteristics near the proton gyrofrequency in high-altitude cusp

2005 ◽  
Vol 23 (3) ◽  
pp. 983-995 ◽  
Author(s):  
D. Sundkvist ◽  
A. Vaivads ◽  
M. André ◽  
J.-E. Wahlund ◽  
Y. Hobara ◽  
...  
Keyword(s):  
Magnetic Field ◽  
High Altitude ◽  
Nonlinear Effects ◽  
Linear Wave ◽  
Wave Growth ◽  
Ion Cyclotron Waves ◽  
Background Magnetic Field ◽  
Ion Cyclotron ◽  
The Waves ◽  
Proton Gyrofrequency

Abstract. We present a detailed study of waves with frequencies near the proton gyrofrequency in the high-altitude cusp for northward IMF as observed by the Cluster spacecraft. Waves in this regime can be important for energization of ions and electrons and for energy transfer between different plasma populations. These waves are present in the entire cusp with the highest amplitudes being associated with localized regions of downward precipitating ions, most probably originating from the reconnection site at the magnetopause. The Poynting flux carried by these waves is downward/upward at frequencies below/above the proton gyrofrequency, which is consistent with the waves being generated near the local proton gyrofrequency in an extended region along the flux tube. We suggest that the waves can be generated by the precipitating ions that show shell-like distributions. There is no clear polarization of the perpendicular wave components with respect to the background magnetic field, while the waves are polarized in a parallel-perpendicular plane. The coherence length is of the order of one ion-gyroradius in the direction perpendicular to the ambient magnetic field and a few times larger or more in the parallel direction. The perpendicular phase velocity was found to be of the order of 100km/s, an order of magnitude lower than the local Alfvén speed. The perpendicular wavelength is of the order of a few proton gyroradius or less. Based on our multi-spacecraft observations we conclude that the waves cannot be ion-whistlers, while we suggest that the waves can belong to the kinetic Alfvén branch below the proton gyrofrequency fcp and be described as non-potential ion-cyclotron waves (electromagnetic ion-Bernstein waves) above. Linear wave growth calculations using kinetic code show considerable wave growth of non-potential ion cyclotron waves at wavelengths agreeing with observations. Inhomogeneities in the plasma on the order of the ion-gyroradius suggests that inhomogeneous (drift) or nonlinear effects or both of these should be taken into account.

scholarly journals Ultrahigh resolution simulations of mode converted ion cyclotron waves and lower hybrid waves

2004 ◽  
Vol 164 (1-3) ◽  
pp. 330-335 ◽  
Author(s):  
J.C. Wright ◽  
P.T. Bonoli ◽  
E. D'Azevedo ◽  
M. Brambilla
Keyword(s):  
Lower Hybrid ◽  
Ultrahigh Resolution ◽  
Ion Cyclotron Waves ◽  
Ion Cyclotron ◽  
Hybrid Waves ◽  
Lower Hybrid Waves

scholarly journals Lower hybrid oscillations in multicomponent space plasmas subjected to ion cyclotron waves

1997 ◽  
Vol 102 (A1) ◽  
pp. 175-184 ◽  
Author(s):  
G. V. Khazanov ◽  
E. N. Krivorutsky ◽  
T. E. Moore ◽  
M. W. Liemohn ◽  
J. L. Horwitz
Keyword(s):  
Space Plasmas ◽  
Lower Hybrid ◽  
Ion Cyclotron Waves ◽  
Ion Cyclotron

MMS Observations of Ion Cyclotron Waves in the Solar Wind

2020 ◽  
Author(s):  
Hanying Wei ◽  
Lan Jian ◽  
Daniel Gershman ◽  
Christopher Russell
Keyword(s):  
Solar Wind ◽  
Source Region ◽  
The Sun ◽  
Storm Events ◽  
Ion Temperature ◽  
Ion Cyclotron Waves ◽  
Ion Cyclotron ◽  
Generation Mechanisms ◽  
The Waves ◽  
Wave Properties

<p>Although electromagnetic ion cyclotron waves (ICWs) have been observed in the solar wind by multiple missions at heliocentric distances from 0.3 to 1 AU, there are still open questions on the generation mechanisms for these waves. Detailed analysis of the plasma distribution is needed to examine whether these waves are possibly generated locally.</p><p>In the solar wind, there are mainly three types of ion-driven instabilities responsible for parallel-propagating ICWs: ion cyclotron instabilities driven by ion component with temperature anisotropies greater than 1, parallel firehose instabilities driven by ion temperature anisotropies smaller than 1, and ion/ion magnetosonic instabilities driven by the relative drift between two ion components. In the solar wind frame, the waves due to ion cyclotron instability have left-handed polarization, while the waves due to firehose and ion/ion magnetosonic instabilities have right-handed polarization. Depending on the wave propagation parallel or anti-parallel to the magnetic field, the wave frequencies in the spacecraft frame are Doppler shifted higher or lower even with reversed handness. With the plasma data from Magnetospheric Multiscale (MMS) mission, we can examine the possible unstable mode with dispersion analysis and check if the prediction agrees with the observed wave mode. If the plasma measurements of the local solar wind do not support the wave growth, the waves could be possibly generated remotely close to the Sun and propagate away from the source region and are also carried outward by the solar wind flow. If these waves are generated remotely closer to the Sun, the wave properties at different heliocentric distances would help us better understand their sources.</p><p>The MMS spacecraft spends long periods of its orbit in the “pristine” solar wind starting end of 2017. From the 2017 December data we find over a hundred events and 42 of them last longer than 10 minutes which are called ICW storm events, and the longest event captured lasted over 2 hours. Although only about 17 of them have the plasma data available, we can perform case studies on these events first to investigate the wave properties and possible plasma instabilities, which will help us investigate the wave generation mechanisms due to local or remote sources.</p>

Origin of the zebra structure in the Jovian decameter radio emission

2020 ◽  
Vol 645 ◽  
pp. A31
Author(s):  
V. E. Shaposhnikov ◽  
G. V. Litvinenko ◽  
V. V. Zaitsev ◽  
V. V. Zakharenko ◽  
A. A. Konovalenko
Keyword(s):  
Lower Hybrid ◽  
Height Distribution ◽  
Plasma Parameters ◽  
Extended Source ◽  
Ion Cyclotron Waves ◽  
Proposed Model ◽  
Ion Cyclotron ◽  
Magnetic Field Model ◽  
Decameter Radio ◽  
Upper Ionosphere

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.

scholarly journals Dispersion relation of electromagnetic ion cyclotron waves using Cluster observations

2013 ◽  
Vol 31 (8) ◽  
pp. 1437-1446 ◽  
Author(s):  
I. P. Pakhotin ◽  
S. N. Walker ◽  
Y. Y. Shprits ◽  
M. A. Balikhin
Keyword(s):  
Dispersion Relation ◽  
Wave Vector ◽  
Cold Plasma ◽  
High Plasma ◽  
Minimum Variance ◽  
Ion Cyclotron Waves ◽  
Hot Plasma ◽  
Ion Cyclotron ◽  
Electromagnetic Ion Cyclotron Waves ◽  
Plasma Dispersion

Abstract. Multi-point wave observations on Cluster spacecraft are used to infer the dispersion relation of electromagnetic ion cyclotron (EMIC) waves. In this study we use a phase differencing method and observations from STAFF and WHISPER during a well-studied event of 30 March 2002. The phase differencing method requires the knowledge of the direction of the wave vector, which was obtained using minimum variance analysis. Wave vector amplitudes were calculated for a number of frequencies to infer the dispersion relation experimentally. The obtained dispersion relation is largely consistent with the cold plasma dispersion relation. The presented method allows inferring the dispersion relation experimentally. It can be also used in the future to analyse the hot plasma dispersion relation of waves near the local gyrofrequency that can occur under high plasma beta conditions.

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