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Calculating KP Index - How to?

Discussion in 'General Discussion' started by cditty, Dec 1, 2014.

  1. cditty

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    Hi all. I'm a techy type of guy and I'm trying to figure out how to calculate the KP Index. I can get the current K readings and know how to convert them with the A index, but how do I end up with the Kp index?

    For example, the Kp index for today is supposed to be a 4. Here are the planetary K-indexes.
    2 2 2 1 2 2-1-1

    According to the NOAA, the A index is 4.75. Ok. 4.75 isn't that far off from 4. But if I go back historically 2 weeks and use 11/16/2014's data.

    4 4 4 3 4 4 3 3

    I get a A index of 22.5, but the Kp index for that day was 3.

    Even the examples at the NOAA don't say how Kp is calculated. Just the K and A.

    Can anyone offer any insight?
     
  2. Noël

    Noël Guest

  3. Meta4

    Meta4 Moderator
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    Can't help with calculating but I'm still to see any effect on GPS or flying from any of that K index stuff.
    K up or down doesn't seem to make any real difference.
     
  4. cditty

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    I did Noel. But that only tells how to get the A index. How do you go from a A index of 22.5 to a Kp value of 3 like in my example.
     
  5. knuckles

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  6. cditty

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    Thanks for the link knuckles. Unfortunately, that doesn't tell how its calculated. It just says its a weighted avg.
     
  7. CallMeAlan

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    To Meta4, saying you are yet to see any effect of K upon GPS: one time, before I knew anything about K-index, I couldn't get any satellites at all with my Phantom. Zero. Later I learned that the K for that day was around 7 or 8. I stick to 3 or lower nowadays, stay at home if it's 4 or higher, too much cash invested in my F550 to risk it!
     
  8. Noël

    Noël Guest

    I've tried several calculations to get the A index with the given K indices.

    As you noted. The lower the K indices, the closer the NOAA given calculated A index is correct!
    The higher the K indices, the more off the calculated A index is!

    I have no clue how NOAA is calculating the A index in the Geomagnetic Data reports.

    For my K index app it's not a problem as it is using the K indices, but it would be interesting to know how NOAA is calculating the A index
     
  9. The Editor

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    Email them ???
     
  10. Noël

    Noël Guest

  11. Noël

    Noël Guest

    Re-reading your question I'm not sure what you are after!
    The K-indices for day: 11/16/2014 were indeed: 4 4 4 3 4 4 3 3
    Adding this together gives an "a index" of 22.5 ((27+27+27+15+27+27+15+15)/8)
    Looking at day 11/16/2014 it shows that the "a index" was 22
    .5 off is caused because of the + and - K-indices that are not shown in the NOAA's reports.

    So what are you asking for?
    The K-indices are provided by ground-based magnetometers (world wide in this case) with a scale from 0 to 9
    The a-index is a linear scale called the "equivalent three hourly range" (0,3,7,15,27,48,80,140,240,400), and calculated by adding the matching a-index to the K-indices and dividing it by 8.
     
  12. cditty

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    Right. You are reading all that correctly.

    On 11/16, the K indexes were very high (4 4 4 3 4 4 3 3). But the Kp index for that day was a 3. I don't see any correlation between the two. For yest and today, the Kp indexes were/are 4s, but the K indexes are nowhere near as high as 11/16. (2 2 2 1 2 2 2 4 & 3 3 3 2 3-1-1-1)

    That's what has me so confused. How do we go from a high K index to a 1-9 number for the Kp index we all use for flying.