Resonant interaction between gravitational waves, electromagnetic waves, and plasma flows

Abstract

In magnetized plasmas gravitational and electromagnetic waves may interact coherently and exchange energy between themselves and with plasma flows. We derive the wave interaction equations for these processes in the case of waves propagating perpendicular or parallel to the plasma background magnetic field. In the latter case, the electromagnetic waves are taken to be circularly polarized waves of arbitrary amplitude. We allow for a background drift flow of the plasma components which increases the number of possible evolution scenarios. The interaction equations are solved analytically and the characteristic time scales for conversion between gravitational and electromagnetic waves are found. In particular, it is shown that in the presence of a drift flow there are explosive instabilities resulting in the generation of gravitational and electromagnetic waves. Conversely, we show that energetic waves can interact to accelerate particles and thereby produce a drift flow. The relevance of these results for astrophysical and cosmological plasmas is discussed.

The general relativistic magnetohydrodynamic dynamo equation

“…These assumptions will make it possible to describe a two‐component plasma in terms of a one‐fluid description, as the electrons can be considered inertialess (see also e.g. Papadopoulos et al 2001; Papadopoulos, Vlahos & Esposito 2002; Servin & Brodin 2003; Moortgat & Kuijpers 2003, 2004). The one‐fluid description means a tremendous computational simplification, especially for complicated geometries.…”

Accumulative coupling between magnetized tenuous plasma and gravitational waves

“…In such investigations, the presence of the magnetic field is vital for mediating the coupling between the GW and the EMW, and a curved background spacetime can also serve as the catalyst. More interestingly for our present study though, it has been noted that currents enabled by the presence of a plasma can also greatly enhance the coupling [22][23][24][25][26][27][28][29][30], through their being disturbed by the GW. It is therefore interesting to examine the possibility of replacing the vacuum electromagnetic field with a strongly magnetized tenuous plasma as the quiescent configuration (in a stationary solution of the so-called force-free electrodynamics, thus no background radiation).…”

“…In previous studies involving magnetized plasma/fluid, while detailed equations of motion are written down and some estimates on the amplitude of induced plasma waves (PW) are made, analytical solutions relevant for HFGW detection are generally lacking, and a precise evaluation of the coupling strength and a depiction of the characteristics, such as the associated charges and currents, of the induced radiation remain illusive (we note that explicit solutions are given by Ref. [29] for the EMW to GW conversion, but not vice versa, which is noted to be more complicated, and Ref. [30] offers standing but not travelling wave solutions).…”

Gravitational waves: Classification, methods of detection, sensitivities and sources

“…There are four kind of potential GW sources in the very high frequency and ultrahigh frequency bands: 39 (i) Discrete sources; 173 (ii) Cosmological sources; 174 (iii) Brane-world Kaluza-Klein (KK) mode radiation; 175,176 (iv) Plasma instabilities. 177 In general, objects do not radiate efficiently at wavelengths very different from their size. This implies objects radiate at these bands need to be very small and yet have a very large energy concentration to induce significantly large curvature fluctuations.…”