I was searching for interesting data from space recently, and stumbled onto https://www.swpc.noaa.gov/.

The long and short is that they offer some interesting solar wind data

Of particular interest to me is the 'mag' data they offer here, and the 'plasma' data they offer here

I have some questions on these:

  1. What is the 'mag'/'plasma' data exactly?
  2. How come they are recorded and served to the public in such fast intervals in comparison to other data in the space industry?
  3. What technology is used to record these data?
  • 4
    $\begingroup$ The reason it's given to the public rapidly is because solar storms can have a direct impact on radio communications, the power grid, and obviously satellites. So people need to react to it in real time. $\endgroup$ Apr 14, 2023 at 14:20
  • 1
    $\begingroup$ @GregMiller - and here I was hoping that sailing the solar winds was rapidly becoming common. Sigh... $\endgroup$
    – Jon Custer
    Apr 14, 2023 at 14:51

1 Answer 1


What is the 'mag'/'plasma' data exactly?

The 'mag' part refers to magnetic field data, and that is measured (usually) by a fluxgate magnetometer.

The 'plasma' part refers to in situ particle measurements, usually the thermal plasma of the solar wind. This can be measured by multiple different types of instruments like electrostatic analyzers or Faraday cups (e.g., see short description and references in https://ui.adsabs.harvard.edu/abs/2021RvGeo..5900714W/abstract).

How come they are recorded and served to the public in such fast intervals in comparison to other data in the space industry?

What do you mean by "such fast intervals"? Are you referring to the cadence of the measurements? Or are you referring to how quickly it is posted relative to when it was measured?

If the former, then not that 5 minute cadence is not fast. The Magnetospheric Multiscale Mission can measure electron velocity distribution functions in just ~30 ms and magnetic fields at over 16,000 samples per second (electric fields can go up to over 256,000 samples per second).

If the latter, then what you are seeing is called "near real-time data" and it comes from either DSCOVR or ACE, both located at the first Earth-Sun L1 point. They get the data immediately because both spacecraft immediately send the data to ground after it's measured (some onboard calculations are done but that doesn't take more than a few ms). There are ground stations dedicated to receiving these signals and then immediately transmitting them to NOAA.

What technology is used to record these data?

See my answer to your first question above.

  • $\begingroup$ The electric utility people would like to have more time to prepare for disturbances, but L1 is the farthest upstream it's practical to put a spacecraft for continuous monitoring. $\endgroup$
    – John Doty
    Jan 17 at 16:03
  • $\begingroup$ @JohnDoty - I have been working on a few mission concept studies for the past few years, one involves using solar sails. With those, we can park several hundred Earth radii upstream of L1, thus giving something like double the warning time... $\endgroup$ Jan 17 at 16:45
  • $\begingroup$ And I've heard people talk of million km carbon fibers, dangling sensors from L1. Tech that has not yet worked on any scale is pretty speculative for something people will want to rely on. $\endgroup$
    – John Doty
    Jan 17 at 16:54
  • $\begingroup$ This is an odd reaction to me stating I was working on mission concept studies. The solar sail tech is at TRL 6 and higher, depending on the group developing it, which isn't speculative. $\endgroup$ Jan 17 at 17:59
  • $\begingroup$ I've told many TRL stories. God is in the details, not in some arbitrary score. $\endgroup$
    – John Doty
    Jan 17 at 18:07

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