Weak CME impact 13th July 2020

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Carbon60
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Weak CME impact 13th July 2020

Post by Carbon60 »

A few days overdue on this one....

Late on the 13th and through the early hours of the 14th Earth's magnetic field felt a blow of plasma waves from a weak and slow moving CME that erupted from the Sun a five days earlier. These caused the usual response on my magnetometer buried in my back garden, as shown below. Usually I record data at a cadence of 150 seconds, but more recently with a new PC I've been recording additionally at a cadence of 1 second for higher resolution. This has paid off since I've been able to resolve what I think might be PC3-4 waves (or ripples since they are superimposed onto the main longer frequency waves). Some background information can be found here: https://agupubs.onlinelibrary.wiley.com ... 17JA025033

These have been known about for over 50 years, so nothing new, but this is the first time I've recognised such 'ripples' in my data. I don't know what they are for certain, but there is definitely some structure there.

Here's the main event:
20200713_CME_Impact.jpg
20200713_CME_Impact.jpg (166.67 KiB) Viewed 1706 times
and the finer details in high resolution 1s cadence recordings (timestamp as shown)...
20200713_00_30_CME_waves.jpg
20200713_00_30_CME_waves.jpg (56.1 KiB) Viewed 1706 times
20200713_05_50_CME_waves.jpg
20200713_05_50_CME_waves.jpg (38.21 KiB) Viewed 1706 times
The Sun might be quiet at the moment, but there are still lots of interesting phenomenon to study.

Thanks for looking.

Stu.


H-alpha, WL and Ca II K imaging kit for various image scales.
Fluxgate Magnetometers (1s and 150s Cadence).
Radio meteor detector.
More images at http://www.flickr.com/photos/solarcarbon60/
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Re: Weak CME impact 13th July 2020

Post by Montana »

Very interesting data Stuart, you will soon be recognized as a professional station :hamster:

Alexandra


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Re: Weak CME impact 13th July 2020

Post by p_zetner »

Stu: You’ve definitely uncovered more interesting behaviour with your high cadence upgrade.
If you would like, send me an ASCII data file of of this run. I could try to do a Fourier analysis and see what the ripple “frequency spectrum” looks like. Seems to be a pretty well-defined frequency.
Cheers.
Peter


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Re: Weak CME impact 13th July 2020

Post by Carbon60 »

Many thanks Alexandra/Peter.

Peter, I can send a CSV file with time stamps and sensor frequency if you can work with that, or an excel file if you prefer.
Thanks for taking the time to take a look at the data.

Stu


H-alpha, WL and Ca II K imaging kit for various image scales.
Fluxgate Magnetometers (1s and 150s Cadence).
Radio meteor detector.
More images at http://www.flickr.com/photos/solarcarbon60/
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Re: Weak CME impact 13th July 2020

Post by marktownley »

Fascinating stuff Stu! It's shame your data isn't streamed live, it would be really interesting to see how the graph responds to real time aurora when in Iceland.


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Re: Weak CME impact 13th July 2020

Post by Carbon60 »

Thanks Mark.
I'll have to look into how to do that, Mark. It would have to be the raw version as captured.

Thanks also Alexandra/Peter.

Stu.


H-alpha, WL and Ca II K imaging kit for various image scales.
Fluxgate Magnetometers (1s and 150s Cadence).
Radio meteor detector.
More images at http://www.flickr.com/photos/solarcarbon60/
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Re: Weak CME impact 13th July 2020

Post by p_zetner »

Hi Stu.

The attached image summarizes my attempt at Fourier analyzing the magnetometer data.
FFT_Montage_v2.png
FFT_Montage_v2.png (602.3 KiB) Viewed 1455 times
Panel (a) shows the raw magnetometer data that you sent me along with a smoothed version (7000 point Savitzky-Golay). The horizontal scale is measured in seconds with t=0 corresponding to date/time 2020-07-13 00:00:00. In panel (b), I used the smoothed data as a rough "baseline" to get rid of the overall slow time variation by subtracting this baseline from the raw data. The result of a fast fourier transform (fft) applied to the entire dataset shown in (b) is given in panel (c). It's pretty choppy! On a smaller horizontal scale, I discerned the rough indications of a peak so I applied some smoothing (100 points SG) to the fft and plot this together with the unsmoothed fft spectrum (plotted as scattered points) in panel (d). The smoothed curve shows some pretty good evidence of peaks at 2.6 mHz and 4.8 mHz (marked by the arrows in the figure). These oscillation frequencies are definitely within the range (1.7–6.7 mHz) expected for Pc5 waves, as quoted in the article you've referenced. It looks like you've observed two rather well defined resonances. There's not much evidence for anything happening at higher frequencies. I haven't read enough to grasp the physics of all this but it definitely makes for an interesting observation!

All the best.
Peter


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Re: Weak CME impact 13th July 2020

Post by marktownley »

Loving the science here guys!


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Re: Weak CME impact 13th July 2020

Post by Montana »

That's fabulous Peter!

Alexandra


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Re: Weak CME impact 13th July 2020

Post by Carbon60 »

Many thanks, Peter, for taking the time and trouble to undertake the analysis.

Good to see your results confirming the effect is real and not just my wishful thinking.

Stu.


H-alpha, WL and Ca II K imaging kit for various image scales.
Fluxgate Magnetometers (1s and 150s Cadence).
Radio meteor detector.
More images at http://www.flickr.com/photos/solarcarbon60/
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