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In a time domain study, fields do not have to exhibit a sinusoidal dependence on time. Frequency domain studies are a special case in which the time dependence is known to be sinusoidal, so a simpler approach becomes possible. Phase information is managed by treating E as complex. In the frequency domain, emw.normE is the local value of the (phase independent) magnitude of the E vector. If you want phase information, you can examine the real and imaginary parts of individual field components, or you can apply the arg function to them. In time-domain, temw.normE is the local value of the time-dependent magnitude of the E-vector. Since there is no a priori' reason for the software to assume that E will oscillate sinusoidally in a generic time domain model, no default time-averaging is performed for you (although you could set up your own operations to do something like that, if you wanted). Note: Since your specific problem has a sinusoidal dependence in time, you are better off using the frequency-domain model, which is more efficient for that purpose.

Hi Robert, thank you for the detailed response. Just to follow up, if I want to find the average value of the electric field magnitude (at a point or surface) over one or more cycles in a frequency domain study, how should I proceed? I was under the assumption that it would be just equal to the phase-independant emw.normE. Thank you.

Again, in frequency domain, there is no averaging over cycles of the direct field quantities. You can average over space if you want to. Any temporal sinusoidally-varying scalar quantity (such any particular vector component of a sinusoidally varying field quantity) has a peak value. It also has a root mean square (rms) value, which is (for a sinusoid) 1/sqrt(2) of the peak value. Is that, perhaps, the "average" of interest to you? The true average over a cycle of any particular vector component of any sinusoidally varying field quantity is zero. After all, the average of a sine (or cosine) function over a cycle is zero. Hence, there is no need to compute it (since it is zero). You can form spatial averages of anything that you enter into operators (like Comsol's probes and post-processing integration operators) that can compute spatial averages.