Plasma noise in TianQin time-delay interferometry
Yi-De Jing, Lu Zheng, Shutao Yang, Xuefeng Zhang, Lingfeng Lu, Binbin Tang, Wei Su
Abstract
TianQin is a proposed geocentric space-based gravitational wave observatory mission, which requires time-delay interferometry (TDI) to cancel laser frequency noise. With high demands for precision, the solar-wind plasma environment at $\ensuremath{\sim}{10}^{5}\text{ }\text{ }\mathrm{km}$ above the Earth may constitute a non-negligible noise source to laser interferometric measurements between satellites, as charged particles perturb the refractivity along light paths. In this paper, we first assess the plasma noises along single links from space-weather models and numerical orbits, and analyze the time and frequency domain characteristics. Particularly, to capture the plasma noise in the entire measurement band of ${10}^{\ensuremath{-}4}--1\text{ }\mathrm{Hz}$, we performe additional space-weather magnetohydrodynamic simulations in finer spatial and temporal resolutions and utilize Kolmogorov spectra in high-frequency data generation. Then, we evaluate the residual plasma noises of the first- and second-generation TDI combinations. Both analytical and numerical estimations have shown that under normal solar conditions, the plasma noise after TDI is less than the secondary noise requirement. Moreover, TDI is shown to exhibit moderate suppression on the plasma noise below $\ensuremath{\sim}{10}^{\ensuremath{-}2}\text{ }\text{ }\mathrm{Hz}$ due to noise correlation between different arms, when compared with the secondary noise before and after TDI.