  Experimental evidence of intrinsic noise induced coherence resonance in a
glow discharge plasma is being reported. Initially the system is started at a
discharge voltage (DV) where it exhibited fixed point dynamics, and then with
the subsequent increase in the DV spikes were excited which were few in number
and with further increase of DV the number of spikes as well as their
regularity increased. The regularity in the interspike interval of the spikes
is estimated using normalized variance (NV). Coherence resonance was determined
using normalized variance curve and also corroborated by Hurst exponent and
power spectrum plots. We show that the regularity of the excitable spikes in
the floating potential fluctuation increases with the increase in the DV, upto
a particular value of DV. Using a Wiener filter, we separated the noise
component which was observed to increase with DV and hence conjectured that
noise can be playing an important role in the generation of the coherence
resonance. From an anharmonic oscillator equation describing ion acoustic
oscillations, we have been able to obtain a FHN like model which has been used
to understand the excitable dynamics of glow discharge plasma in the presence
of noise. The numerical results agree quite well with the experimental results.
