In the power spectrum, why is the peak frequency at the first harmonic

[dave gannon]

TL;DR

I have being doing time series analyse of the crab nebula pulsar and cannot come up with a good answer for this question. any help would be greatly appreciated.

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[sophiecentaur]

Could you be a bit more verbose with your question please?
For instance, does First Harmonic mean Fundamental or does it mean First Overtone - or Second Harmonic? Are you referring to the variation with time? Show a graph perhaps?

 

[davenn]

For instance, does First Harmonic mean Fundamental or does it mean First Overtone - or Second Harmonic?

my thoughts exactly

if @dave gannon is referring to the fundamental freq. then this is where the most energy is being "emitted"D

 

[berkeman]

Summary: I have being doing time series analyse of the crab nebula pulsar and cannot come up with a good answer for this question. any help would be greatly appreciated.

Welcome to the PF.

The "first harmonic" is more commonly referred to as the "fundamental" frequency. The harmonics are at 2x and 3x and ...x (integer multiples of) the fundamental frequency.

There are some cases where the harmonics are stronger than the fundamental. I'm not that familiar with such cases, but a simple Google search turned up a number of links to such cases. Here is one such link:

https://www.soundonsound.com/sound-...ocal-parts-harmonics-louder-fundamental-pitch

 

[atyy]

Summary: I have being doing time series analyse of the crab nebula pulsar and cannot come up with a good answer for this question. any help would be greatly appreciated.

What physical quantity are you measuring?

To add to @berkeman's example, Kristin Holz gives clarinet examples where some of the higher harmonics are stronger than the fundamental https://courses.physics.illinois.ed...rts/2013_REU/Kristin_Holz_Final_REU_Paper.pdf

 

[sophiecentaur]

If the source is sending out radiation from each end as it rotates there will be two peaks every rotation. If the two output levels are not exactly the same then there will be a small amount of fundamental and a lot of second harmonic.