Bias in apparent dispersion measure due to de-magnification of plasma lensing on background radio sources

The effect of ionized gas on the propagation radio signals is known as plasma lensing. Unlike gravitational lensing, lensing causes both magnification and strong de-magnification effects to background sources. We study cross section for two density profiles, Gaussian power-law models. In general, increases with gradient. Radio sources can be used measure free electron along line sight. However, an underestimate density. Such a bias density, up $\sim 15\%$ in high region. There large probability that clumps will missed due this bias. also change luminosity function number low ends overestimated biasing effect.