Response of a spaceborne gravitational wave antenna to solar oscillations

TL;DR

This paper explores the potential of the LISA space-based gravitational wave detector to observe low-frequency solar oscillations, which are difficult to detect with traditional helioseismology, by analyzing the gravitational signals generated by these oscillations.

Contribution

It demonstrates that LISA could detect solar oscillations at frequencies below 2×10⁻⁴ Hz with higher signal-to-noise ratio than helioseismic methods, if such oscillations have certain amplitudes.

Findings

LISA can detect solar oscillations with surface velocities of 1-10 mm/sec in the 10⁻⁴ to 5×10⁻⁴ Hz range.

Gravitational signals from solar quadrupole modes dominate below 3×10⁻⁴ Hz.

Detection is feasible if solar oscillation amplitudes are within predicted ranges.

Abstract

We investigate the possibility of observing very small amplitude low frequency solar oscillations with the proposed laser interferometer space antenna (LISA). For frequencies $\nu$ below $3\times 10^{-4} {\rm Hz}$ the dominant contribution is from the near zone time dependent gravitational quadrupole moments associated with the normal modes of oscillation. For frequencies $\nu$ above $ 3\times 10^{-4} {\rm Hz}$ the dominant contribution is from gravitational radiation generated by the quadrupole oscillations which is larger than the Newtonian signal by a factor of the order $(2 \pi r \nu/ c)^4$, where $r$ is the distance to the Sun, and $c$ is the velocity of light. The low order solar quadrupole pressure and gravity oscillation modes have not yet been detected above the solar background by helioseismic velocity and intensity measurements. We show that for frequencies $\nu \lesssim 2\times 10^{-4} {\rm Hz}$, the signal due to solar oscillations will have a higher signal to noise ratio in a LISA type space interferometer than in helioseismology measurements. Our estimates of the amplitudes needed to give a detectable signal on a LISA type space laser interferometer imply surface velocity amplitudes on the sun of the order of 1-10 mm/sec in the frequency range $1\times 10^{-4} -5\times 10^{-4} {\rm Hz}$. If such modes exist with frequencies and amplitudes in this range they could be detected with a LISA type laser interferometer.