# How to compute the energy of a time series?

I am analyzing the vertical component of 1Hz sampled geomagnetic data. These data were band-passed filtered around 0.01Hz (100s).

I would like to compute the daily energy contained in these time series. So far, I have tried computing the sum of the squared amplitudes of all samples:

Where zk are the samples of the vertical geomagnetic field time series.

Is this the correct way of computing the daily energy contained in these band-passed filtered time series? Should I take the square root of this sum, or normalize it by the number of samples in the time series?

• You've got the right formula. Dividing it by the number of samples would make it energy per time, i.e. power. Keep it that way. (it's consistent to physics) – Marcus Müller Mar 11 at 8:17
• Thanks for your quick reply, Marcus! I am relieved that I am using the correct formula. – Sheldon Mar 11 at 8:39