Solar, Space, and Geomagnetic Weather, Part V: Solar Activity and the Activity Indices By Stephanie Osborn

Solar, Space, and Geomagnetic Weather, Part V: Solar Activity and the Activity Indices

By Stephanie Osborn

“Interstellar Woman of Mystery”

Rocket Scientist and Novelist

Okay, back to bar magnets again. Because the Earth has one. But of course it’s three-dimensional, not like our iron filings on paper example. Imagine picking up the bar magnet with the iron filings and paper attached, and rotating it 360º, letting the iron filings remain in the areas they move through. Now you have an image of what a three-dimensional dipolar (2-pole) magnetic field looks like — sort of like a giant pumpkin.



With the solar wind (which is probably the largest influence on the interplanetary magnetic field) pushing on it from the Sun direction, the side of the pumpkin facing the Sun tends to smush in, but the side away from the Sun tends to stretch out and form a long tail. (You can see a really good animation of how this works here: This is all to say that you HAVE to think of the geomagnetic field three-dimensionally. And if it is three-dimensional, then each part of the field has an x-, a y-, and a z-coordinate component.

Let’s simplify for a minute. Let’s say that we’re going to look at the component of the geomagnetic field that is running horizontally to the Earth’s surface at any given point. Now because the Earth is curved, this is a tangent line that is continually changing as you move around the Earth. Now let’s look at the disturbances from normal, caused by solar weather — coronal holes, CMEs, what have you.

So we have these variations that are going to be different for different parts of the Earth for the same event. How do we measure it? It’s a little like a Richter scale for geosolar storms. It runs from zero to nine, and there’s a special formula that enables it to be calculated regardless of the location of the observatory, just like the Richter magnitude of a quake can be determined from seismographs on the opposite side of the globe. This scale for solar-induced geomagnetic activity is called the K-index. Zero is essentially no activity; anything above 5 is considered a storm level of activity. The bigger the number, the greater the effects seen on the ground, and the farther south the auroral oval can be seen. At a K=9, the aurora can be seen…in the TROPICS.


Yes, this is the Aurora Australis observed from space.

 (Just for the sake of more information, the letter K was derived from the German word “kennziffer,” which apparently means “characteristic number.” Us scientists, we love our imaginative names, you know?)

Now if we reference the Kp index, we’re talking about the interplanetary K index, not the geomagnetic K index. This is an average of all the K indices from all of the observatories, weighted as appropriate (remember, you won’t get the same measurements from the various observation sites, so you have to factor that in, as well as the fact that the geomagnetic field is constantly changing). This gives us an indication of what the interplanetary magnetic field (IMF) is doing. BUT — not all of the stations report in at the same time. So then scientists have to calculate something called the “estimated Kp” which is just what it sounds like — an estimate for those stations that haven’t reported in yet. This can sometimes be a very good predictor of what the magnetic field is going to do, and sometimes not so much. We’re still very much learning this particular science.

Most of the time, it looks kinda like this:



Each vertical bar represents a 3-hour period. The bars are color-coded to show you how much effect it will have on Earth. Green means little to no effect. Yellow means the geomagnetic field will be unsettled, and you might see a few minor effects. Red means the geomagnetic field will be “storming,” and you WILL see effects. The taller the red bar, the stronger the effects.

So, occasionally, it looks more like this:



If it ever looks like this, we’re probably in trouble:



It actually DID look like this, though. This is from the big geomagnetic storm that occurred October 28-29, 2003. According to NASA, “During the height of the solar activity, more than half of the deep space and near-Earth space science missions experienced the effects of the Halloween storms of 2003. The Solar and Heliospheric Observatory (SOHO) satellite, a collaboration between NASA and the European Space Agency (ESA), failed temporarily. NASA’s Advanced Composition Explorer (ACE) satellite experienced damage, and instruments aboard many spacecraft had to be shut down temporarily.”

“The effects of these storms were ghoulish enough that [aircraft controllers] had to re-route aircraft, it affected satellite systems and communications, and it also caused a power outage in Sweden for about an hour,” said Dr. Holly Gilbert, a solar scientist at NASA’s Goddard Space Flight Center in Greenbelt, Md. “The aurorae are normally limited to the higher latitudes, and these storms were so powerful they created aurorae that could be seen as far south as Florida.”

And here is an aurora photograph, taken during that huge geomagnetic storm…from just outside HOUSTON, TX, on October 29, 2003.



But we’re not done with indices. There’s also something called the a index. This is based on the amplitudes (yep, there’s the reason for using an a) of the deviations from geomagnetic normal, taken over a three-hour period. Then there’s the A index, which is an AVERAGE (yep, that’s where the A came from) of all the a-indices for a 24-hour period.

One more index we need to look at is the G scale, which is the National Oceanic and Atmospheric Administration’s (NOAA) way of quantifying the strength of the geomagnetic disturbance. For any K index of 4 or less, the scale shows G0. At K=5, we jump to G1 — minor storming. For K=6, we have G2. For K=7, G3. At K=8, we have a storm level of G4, and at the maximum K=9, we have maximum storming of G5. Think of it like the Earth’s solar DefCon level.

Next time we’ll go into those DefCon levels in detail.


~Stephanie Osborn

Comet Tales blog/Osborn Cosmic Weather Report:


65 responses to “Solar, Space, and Geomagnetic Weather, Part V: Solar Activity and the Activity Indices By Stephanie Osborn

  1. Something I came across this week:

    In one of the papers I’m going through, the K and another index (okay, I’m sleepy, have no caffeine, and getting old) turned out not to be a good indicator on impact on the grid. No explanation why.

    • It’s a little too broad, and it’s much more global, whereas the actual grid impacts can be limited to a given hemisphere or region. It’s a loose indicator, and certainly it’s a good indicator of the magnitude of the solar/space event, but yeah, it’s only so-so at predicting grid impacts.

      • I’ve started a GIC folder, but I don’t know if I printed the one with the comment on indices. I’d have to find the URL if I didn’t, because I’m trying to study this. The context was that utilities reacting to the indices would result in considerable false alarms, and while it wasn’t stated, you can get a “crying wolf” effect. And then one day the wolf shows up.

        Some of the effects are straight forward, like magnetic saturation of transformer cores, though some of the effects are implied, though you pick it up if you realize a saturated core “levels off” and this can affect output. Then is the malformed sine waves, which is simply the 60 Hz sine wave with the GIC sine waves, which can also lead to harmonics.

        Some of it isn’t, and here I’m playing catch-up – and my calculus is rusty. Considering brushing up on my math just to get get a handle on it.

        I’m worried I’m missing other implied effects, which they expect the reader to grasp. Like the current on the neutral issue.

        Also have the crazy idea of trying to measure a telluric current Just Because. The simplest is to shove two 16 or 20 penny nails in the ground a meter apart and seeing what kind of voltage and current I can pick up. Maybe use four: two on an orientation in line with the local magnetic declination, and two 90° to that line.

    • Yes, I check them both. Solarham is very good for everything-in-one-place daily checking. If I need more info, I check out SIDC. They can both be very hard for a lay person to read however, if you don’t know the terminology.

  2. We’ve touched on monopolar magnets, now bipolar ones (sometimes attractive, sometimes repulsive) but are there multipolar ones?

    (A very solid entry, Dr. O, as evidenced by the extremes to which I have had to stretch in order to quip-on to the comment’s tail of emailed reactions.)

    • Since a magnet is essentially a solid-state solenoid, probably not. You can have a collection of magnets, but each will have their own north and south pole.

      Think of those flat sheet decal magnets made for refrigerators. These are laid out like wide, thin, strips of magnets. Each strip only has one pole facing the refrigerator, but the other pole buried on the decal side.

      • BobtheRegisterredFool

        Per previous articles, it is different because it is a gas magnet.

        There really are situations where the sun is a quadripole (sp?). Since the stuff is moving, one pole can be inside, so we only see the other on the outside.

        OT: Any websites for history of transformer technologies? Would your original theory hold in the case of a sudden high voltage pulse centered on the earth?

        • There’s probably a history of transformers sites somewhere, but the surprising thing is that GIC doesn’t induce as high of voltage as I thought.This is a Bad Thing in that I don’t think lightning arresters would bleed off over voltage in a Carrington Event. Thus every solar event is the type of low-level event I feared. I thought Carrington class events would induce enough voltage to operate lightning arresters; I was wrong.

          There’s still over current protection, and maybe I’m just too stupid to grasp some of what’s going on with GIC and the grid, but in papers I’ve come across two diagrams that just don’t work in that there’s no complete circuit between two grounding points on transmission, not with three-wire Delta, anyway. And yet there’s measurable current on the transformer neutral.

          I’m wondering if it’s simply a case of unbalanced phase currents from induced currents on the line itself. Unbalanced currents are notorious for putting current on the neutral.

          Anyway, unless GIC is high enough to trip over current protection, or to open things when there’s significant current on the neutral, there’s probably not much out there to protect from it. Fortunately, not all transformer designs are as susceptible to GIC damage, and at least one company is marketing one with GIC damage resistance.

        • Bingo. Well observed. Thank you. I was pretty sure we’d discussed it in a previous installment.

    • More complex sunspot groups can in fact have multipoles. It isn’t unusual at all. And during the pole flip we just had at Solar Max, for about 6 months, the Sun had something like four South poles and no North poles.

      It’s all about the fact that it’s not a solid object. If we didn’t already talk about that in a previous installment (which I think we did), it’ll be in one of the next ones.

    • Oh, and thanks, RES, and I’m glad you’re enjoying the series of articles!

    • Okay I went back and looked, and the very first entry for this series talks about the magnetic configuration of sunspots:
      It also has a very cool image that shows the solar magnetic field lines in green, so you can see that, not only is it extremely complex, it actually does have multiple poles.

  3. Thank you, thank you, and thank you again.

  4. The Richter scale is a base 10 logarithmic scale. I google Kp index, and get the quasi-logarithmic local index ( Googling quasi-logarithmic is not very illuminating. Is there a simple explanation?

  5. So what is the effect on Astronauts of a max geomagnetic disturbance? I would believe that the ship’s systems have to be hardened.

    • I know that the Space Shuttle’s control systems ran off 386sx processors because they were the most resistance to radiation upsets.
      And as of five years ago anyone wanting to fly a laptop on ISS had to conform to the standard station architecture for laptops as they all had to serve as backup in case the station control laptops experienced a catastrophic failure caused by increased space radiation.
      Back then they had to be a certain version of IBM Thinkpad. Don’t have any idea what the standard is these days.

    • Oh, and there are certain areas on ISS that are designated as refuge in case of a severe solar radiation storm.

      • And yet in some of the larger storms, the astronauts have been sitting in their saferooms and STILL seeing the flares of light with their eyes closed, caused by the various hi-E photons/particles striking the retina…

        • BobtheRegisterredFool

          These saferooms are opaque to visible light? Do these energy events that interact with the retinas produce anything visible when interacting with walls, controls, fixtures and so forth?

          • They are opaque, yes. They are kind of like the astronaut equivalent of a tornado room: “Go into the most interior room of your house, preferably without windows, and take shelter…”

            Keep in mind that even x-rays and gamma rays have been known to be “seen.” If the flux is high enough, even a low percentage of interactions will result in observable phenomenae.

            Have you ever been in a pitch-dark room, and suddenly seen a single brilliant pinpoint of light in your vision? It may be that you just saw a gamma ray.

            The interaction with a solid object such as a wall is apt to produce either a particle cascade or a microscopic electric current, depending on just what it was that interacted.

      • There is also starting to be evidence of increased cardiovascular disease among astronauts who have either been in LEO for extended periods or outside LEO (Apollo/Moon). Turns out that’s actually the leading cause of death among the Apollo astronauts; someone pointed that out to me a while back and I went and researched it and sure enough. And it is believed that this is caused by radiation damage to the cardiovascular system. I expected it to be cancer…which is apparently the SECOND-most-frequent cause of death.

        • Back about six years ago I participated in a study team that took a hard look at our best estimates for a manned Mars mission. We identified two technical and one philosophical problem using current technology.
          1) maintaining cryo fuel temps over many months of deep space travel.
          2) combined impact of long exposure to both zero gravity and deep space radiation levels.
          3) lack of popular support to justify the expenditure of funds and resources necessary to accomplish the mission. We estimated a minimum of seven heavy lift launches per single Mars round trip mission for at least a billion each, plus the transfer and landing vehicles.

          • 1) *sigh* But there are workarounds.
            2) *sigh* These also have workarounds.
            3) *SIGH* This is the killer.

            • Why I said 1 and 2 were technical, solvable by a good solid engineering team and a bit of time and effort. As for #3, ain’t it the Ghod’s honest truth.
              There are vast sums to be made out there, fortunes beyond anything dreamed of on Earth, but the high startup cost, fear of failure, and greater fear that any success would be stolen by the UN keep anyone from a serious attempt. At least so far.

  6. There’s something wrong with this thread.

    Where’s the corn fritter recipe?

    • Heat oil to 325 degrees F.

      In a medium bowl, combine cornmeal mix, flour, sugar, and salt. In a small bowl, combine milk and eggs. Add milk mixture to cornmeal mixture, stirring well. Stir in butter and corn.

      Pour oil to a depth of 2 inches in a Dutch oven, or use a deep-fryer. Drop by tablespoons into hot oil. Cook 2 to 4 minutes, or until golden, turning once. Drain on paper towels.

  7. *obligatory comment just to see if my girlfriend is reading the comments*

    • Wait, someone finally got smart in your case? Yay! Hope it works out.

      (Seriously, it seems like 90% of the folks here either are happily married or folks just won’t even try a relationship with them.)

  8. Kind of like that “Dungeons and Dragons is demonic LARPing that kills people” movie?