Maybe because only specialists even took note of this. The article itself states that it's more like "hearing a pin drop".
If you look at the scales on the included diagrams, you might note that these "ripples" are on the order of a few nT.
The natural variation of the magnetic field can be 2 orders of magnitude higher, so the real story here is that they were even able to pick this up in the first place...
If you look at the scales on the included diagrams, you might note that these "ripples" are on the order of a few nT.
The natural variation of the magnetic field can be 2 orders of magnitude higher, so the real story here is that they were even able to pick this up in the first place...