The LISA-Taiji dual detector network improves millihertz stochastic gravitational-wave background (SGWB) sensitivity through cross-correlation measurements. Solar wind plasma, however, can generate plasma noise correlated between detectors and bias SGWB cross-correlation estimates. We use high time resolution electron density data from Wind/SWE, estimate the solar wind electron density fluctuation spectrum with the Lomb-Scargle method, and propagate the resulting plasma noise to the time-delay interferometry A/E channels of the LISA-Taiji network. By including finite arm propagation, Taylor frozen flow spatial correlations, and the network overlap reduction response, we compute the SGWB parameter bias induced by interdetector plasma noise. Although the single detector plasma residual is below the reference noise, the component correlated between detectors can enter the SGWB cross-correlation estimator directly. Under dual detector scale coverage, the plasma-induced parameter bias for a power-law SGWB can reach 12.73% of the corresponding Fisher parameter uncertainty. For M2/M3 cosmic string spectra, the bias in ln $G\mu$ can reach 19.26% of the corresponding Fisher parameter uncertainty for the network configurations, observing times, and frequency bands considered here. These results show that the impact of solar wind plasma noise cannot be assessed from the single-detector residual noise level alone. In LISA-Taiji SGWB searches, the interdetector correlated component of this noise can directly affect parameter estimation.

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• Cosmic strings & domain walls
• Cosmology
• Gravitational wave detection
• Gravitational waves
• Solar wind