Indirect Visibility of Gravitational Waves in Magnetohydrodynamic Plasmas

TL;DR

This paper proposes a mechanism where gravitational waves interacting with magnetized plasmas excite MHD waves, which can then produce observable radio signals, potentially allowing indirect detection of GWs.

Contribution

It introduces a novel process linking gravitational wave excitation of MHD modes to radio wave emission, enabling indirect GW visibility in the electromagnetic spectrum.

Findings

MHD waves are excited at the same frequency as GWs in magnetized plasmas.

The proposed radiation process can produce detectable radio signals for neutron star mergers.

Order of magnitude estimates suggest potential observability with LOFAR.

Abstract

We propose a mechanism to make gravitational waves (GWs) visible in the electromagnetic domain. Gravitational waves that propagate through a strongly magnetized plasma interact with the plasma through its anisotropic stress-energy tensor and excite magnetohydrodynamic (MHD) wave modes. In catastrophic events such as the merger of a double neutron star binary, a large fraction of the total binding energy of the system is released in the form of GWs observable by LIGO, and the amount of energy transferred to the MHD waves is substantial. These modes, however, are excited at the same frequency as the GW and are not directly observable. In this paper we investigate radiation processes that operate in the presence of the gravitationally excited MHD waves and radiate in the radio regime accessible to LOFAR. We present order of magnitude estimates for the spectral flux of a merger detectable by a LOFAR.