This paper presents the analysis of Mirnov coil data from pure electron-cyclotron
resonance heated Wendelstein-7 AS discharges with transient magnetohydrodynamical
( MHD) mode activity in otherwise MHD inactive plasmas. Amplitude modulations were
found on the 100 mu s time scale, expected to originate from transient changes of
the plasma pressure profile by anomalous transport events. The analysis was done using
our custom-developed bandpower correlation method, which combines short-time Fourier
transform for the decomposition of the signal with a correlation analysis to quantitatively
characterize the statistical connection between the modulations in the power of different
MHD modes. The effect of a confinement transition ( near a rational rotational transform)
on the correlation between the power modulations of different frequency modes has
been studied. As high as 50% correlation was found between different frequencies in
'bad confinement' shots with enhanced transient transport, while for 'good confinement'
shots no significant correlation was observed.