First G1 of 2024

[Drax Spacex]

Preliminary data indicates we had our first geomagnetic storm of 2024, barely!

https://ibb.co/rpr3wKT

:Product: Forecast Discussion

:Issued: 2024 Feb 27 1230 UTC
# Prepared by the U.S. Dept. of Commerce, NOAA, Space Weather Prediction Center
...

The geomagnetic field was at quiet to G1 (Minor) storm levels, likely
due to combined CME and HSS activity.

[AndrewB]

Hello. I have some questions about this. Sorry for my english, I used a translator for support🫡

I'm little confused about this formal scale. As everybody know we can't talking about G5 storm when global Kp index reaching for example 8,67 but when Kp is 4,67 some sources talks that we've reached level of G1-storm. If minimum Kp for G5 is Kp=9, for G4 - Kp=8 etc. so for G1 = Kp5, not 4,67?

Second question. Why is it always x,33 or x,67 when these are partial values? F.e. 4.67; 5.67; 6.67, 2,33; 5,33...etc? Why not, for example, 4.62 or 4.71 or some other value from 1 to 99? Is there an algorithm to calculate global Kp? Why is it always 33 or 67 after the decimal point when averaging? Where does this value come from?🤔

I noticed that for some time SWPC has been marking Kp 4-4.67 indices in yellow as if it was a G1 storm. In the past, a storm at SWPC page always was from Kp=5 in red and Kp=4 in yellow as an intermediate state between calm (green) and storm (red). The old system of showing official Kp was more fair and logic in my opinion. 🙂

Regards

Andrew

[Sam Warfel]

4 hours ago, AndrewB said:

Hello. I have some questions about this. Sorry for my english, I used a translator for support🫡

I'm little confused about this formal scale. As everybody know we can't talking about G5 storm when global Kp index reaching for example 8,67 but when Kp is 4,67 some sources talks that we've reached level of G1-storm. If minimum Kp for G5 is Kp=9, for G4 - Kp=8 etc. so for G1 = Kp5, not 4,67?

Second question. Why is it always x,33 or x,67 when these are partial values? F.e. 4.67; 5.67; 6.67, 2,33; 5,33...etc? Why not, for example, 4.62 or 4.71 or some other value from 1 to 99? Is there an algorithm to calculate global Kp? Why is it always 33 or 67 after the decimal point when averaging? Where does this value come from?🤔

I noticed that for some time SWPC has been marking Kp 4-4.67 indices in yellow as if it was a G1 storm. In the past, a storm at SWPC page always was from Kp=5 in red and Kp=4 in yellow as an intermediate state between calm (green) and storm (red). The old system of showing official Kp was more fair and logic in my opinion. 🙂

Regards

Andrew

It’s in decimals because it’s in thirds. 5.33 is 5 and 1/3rd, or 5+ if you prefer. 5- is 4.67 or 4 and 2/3rds. 

And the storm values are rounded up. So 4.67 is the same as 5-, which is a G1 storm. So yes, 8.67 would be 9- which would be a G5 storm. 

https://www.spaceweatherlive.com/en/help/the-kp-index.html

[tniickck]

46 minutes ago, Sam Warfel said:

It’s in decimals because it’s in thirds. 5.33 is 5 and 1/3rd, or 5+ if you prefer. 5- is 4.67 or 4 and 2/3rds. 

And the storm values are rounded up. So 4.67 is the same as 5-, which is a G1 storm. So yes, 8.67 would be 9- which would be a G5 storm. 

https://www.spaceweatherlive.com/en/help/the-kp-index.html

Kp9- is a G4. i don’t know why, but NOAA says so

[Vancanneyt Sander]

6 uren geleden, AndrewB zei:

Hello. I have some questions about this. Sorry for my english, I used a translator for support🫡

I'm little confused about this formal scale. As everybody know we can't talking about G5 storm when global Kp index reaching for example 8,67 but when Kp is 4,67 some sources talks that we've reached level of G1-storm. If minimum Kp for G5 is Kp=9, for G4 - Kp=8 etc. so for G1 = Kp5, not 4,67?

Second question. Why is it always x,33 or x,67 when these are partial values? F.e. 4.67; 5.67; 6.67, 2,33; 5,33...etc? Why not, for example, 4.62 or 4.71 or some other value from 1 to 99? Is there an algorithm to calculate global Kp? Why is it always 33 or 67 after the decimal point when averaging? Where does this value come from?🤔

I noticed that for some time SWPC has been marking Kp 4-4.67 indices in yellow as if it was a G1 storm. In the past, a storm at SWPC page always was from Kp=5 in red and Kp=4 in yellow as an intermediate state between calm (green) and storm (red). The old system of showing official Kp was more fair and logic in my opinion. 🙂

Regards

Andrew

As a Dutch user, check out the dutch help section 😉 100% translated in Dutch to get you up and running with all Space Weather Basics 😉 

[AndrewB]

Thank you all 

17 hours ago, Sam Warfel said:

It’s in decimals because it’s in thirds. 5.33 is 5 and 1/3rd, or 5+ if you prefer. 5- is 4.67 or 4 and 2/3rds. 

https://www.spaceweatherlive.com/en/help/the-kp-index.html

Ok, now I'm unterstand how is calculate. But...

16 hours ago, tniickck said:

Kp9- is a G4. i don’t know why, but NOAA says so

Exactly! And I even thought that it was also mentioned in the discussions on this forum when people showed how much need has to happen to be able to talk about a "full-fledged" G5 storm and that it still didn't happen when Kp<9 - so 8.67 also, which if I remember correctly was simply called the solid G4 or G4+, but not the G5. I can't find this thread now, but there someone argued (rightly in my opinion) that some of the old G4 storms (with a Kp index of 8.67) was just a little short of being classified as G5, but it still was G4. Solid, but still G4.

Precisely for this reason, which tniickck wrote about and which also I noticed at NOAA, it seems illogical to me to round up and talk about reaching the G1 level when the Kp was 4.67 and... at the same time talking about a G4 storm if it is 8.67 if we use the official NOAA/SWPC nomenclature.

Until NOAA presented the global Kp indicator as in the graphic from Sam Warfel's link (thanks!) without decimal values, all situations with Kp<5 were marked in yellow as an intermediate state, and not as a storm, and now - I don't know why - it is considered for the G1 storm.

In the previous cycle we had a lot of situations with Kp below 5 (so also with 4.67) and never, as I remember, was it called a G1 storm. And I thought it was very logical. Sites such as SWPC or spaceweather.com or institutes, in situations such as last tuesday have always written about active or unsettled conditions, not a minor storm. Even on Feb.27th on the mentioned website (screenshot) it wasn't mentioned as a G1 storm, only unsettled, which in my opinion is right and consistent.

Maybe it's trivial things but in my opinion introduces an inconsistency in relation to historical data, which is very important from a statistical perspective. As if some sources currently wanted, I don't why, to "boost" the statistics of the number of geomagnetic storms.

Regards