Gravitational waves in neutrino plasma and NANOGrav signal

The recent finding of the gravitational wave (GW) signal by NANOGrav collaboration in nHZ frequency range has opened up door for existence stochastic GWs. In present work, we have argued that a hot dense neutrino asymmetric plasma, GWs could be generated due to instability caused finite difference number densities different species neutrinos. amplitude and sensitivity observation. We shown this mechanism one possible explanations observed signal. also discussed generation an inhomogeneous cosmological where are when neutrinos enter free streaming regime. show plasma cannot explain calculated lower bound on magnetic fields' strength using found signal, should atleast value $\sim 10^{-12}$ G at Mpc length scale.