Normally I present my geomagnetic records using data captured at a cadence of 150s and this is sufficient to capture the ebbs and flows of magnetic declination over the period of interest (days, weeks, or even months). In parallel I also capture data at a cadence of 1s (1Hz).....why? Because at this period of regularity it is possible to resolve some of the much finer detail that resides within the physical interactions between the solar wind (plasma) and our magnetic bubble (magnetosphere). 'Out there' there's a complex set of processes that lead to resonances of various time periods within the electric currents associated with plasma flow that are channelled around our planet. These oscillations can reveal themselves by imprinting their magnetic component onto Earth's magnetic field, which is what's detected on very sensitive magnetometers operating at 'high speed'. Indeed, some magnetometers and related instruments operate at much higher frequencies than 1Hz in order to capture even finer detail.
Anyhow, by way of illustration, here's a magnetograph from January 7th when Earth was inside a fast flowing solar wind stream and there was geomagnetic unrest and the occasional auroral outburst. The main chart shows the changes in magnetic declination (east-west perturbations of a compass) during the day recorded every 150s. The inset shows one of the peaks in hi-res between 19:20 and 19:50 (UT) and as you can see there is much finer detail, but more interestingly there is a series of resonant peaks with intervals of about 60s. I understand that these may be PC4 resonances and that they give some indication as to the speed and density of the solar wind, so they change over time as the solar wind changes.
- 20170107_Hi Res_PC4 Waves.jpg (140.83 KiB) Viewed 1174 times
Thanks for looking
Stu.
so is this the solar wind pulsing at 1 minute intervals? (just trying to understand 
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