Thomson scattering was used to monitor the temporal behavior of the electron gas during the power interruption and power modulation of respectively an inductively coupled plasma (ICP) in argon and a capacitively coupled plasma (CCP) in He both operating under atmospheric conditions. In both cases we studied the electron gas during the decay and re-ignition phase. It is found that experimental results can only be understood if we accept that molecular ions play a dominant role during the plasma decay phase. This is remarkable since plasmas in noble gases are known as atomic plasmas. Interesting features are the anomalous heating of the electron gas during the decay of the Ar-ICP and the heating of the higher energy part of the electron energy distribution function (EEDF) in He-CCP. The EEDF of the He-CCP was found to be far from Maxwellian.