Calculating KP Index - How to?

[cditty]

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?

 

[Noël]

Did you have a look at this already?
http://www.swpc.noaa.gov/info/Kindex.html

 

[Meta4]

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.

 

[cditty]

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.

 

[knuckles]

I installed the free k index monitor on my android phone. Right now it's 2. If it's 5 or higher it turns to red status. I look at it before I fly but don't worry about it much.

http://en.m.wikipedia.org/wiki/K-index# ... of_K-index

 

[cditty]

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

 

[CallMeAlan]

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!

 

[Noël]

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

 

[The Editor]

........ but it would be interesting to know how NOAA is calculating the A index

Email them ???

 

[Noël]

Done

 

[Noël]

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.

 

[cditty]

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.