Background for gravitational wave signal at LISA from refractive index of solar wind plasma

TL;DR

This paper discusses how variations in the solar wind's electron density can create a background signal that interferes with gravitational wave detection by LISA, proposing methods to mitigate this noise.

Contribution

It identifies the solar wind plasma's refractive index variations as a significant noise source for LISA and proposes two countermeasures to mitigate this interference.

Findings

Solar wind density fluctuations can produce a false gravitational wave signal.

Deploying solar wind detectors can help monitor and subtract the background.

Using a second laser wavelength can cancel out the solar wind-induced noise.

Abstract

A strong indication is presented that the space-based gravitational antennas, in particular the LISA concept introduced in 2017 in response to the ESA call for L3 mission concepts, are going to be sensitive to a strong background signal interfering with the prospected signal of gravitational waves. The false signal is due to variations in the electron number density of the solar wind, causing variations in the refractive index of plasma flowing through interplanetary space. As countermeasures, two solutions are proposed. The first solution is to deploy enough solar wind detectors to the LISA mission to allow for reliable knowledge of the solar wind background. The second solution is to equip the LISA interferometer with a second laser beam with a distinct wavelength to allow cancelling of the background solar wind signal from the interferometric data.