Difference between Kp index forecast and geomagnetic forecast

[Guest]

Hello,

I'm trying to find the best way to read aurora forecasts but I can't understand the difference between NOAA's 3-Day Forecast and NOAA's 3-Day Geomagnetic Forecast.
The former is used in the NOAA Aurora Dashboard whereas the latter is used by SpaceWeatherLive in the "Aurora Forecast" but they show widely different values.

For instance, at the time of writing this, one forecasts Kp 1.00 when the other predicts Kp 6.00 for 00-03 on Feb 18. On the other hand, one shows Kp 4.67 while the second says Kp 1.67 for 18-21 on Feb 19.

Why are they different, what do they represent and which one should I follow/look at to see Auroras?

[Jesterface23]

The 3-Day Geomagnetic Forecast for the Kp index is the same on both. The 3-Day Forecast includes forecasts for other solar events as well.

The new update happened to come out, so it is hard it is hard to tell what is where. The 3-Day Geomagnetic Forecast should match the Predicted Kp-indices here under the default Kp-indices tab, https://www.spaceweatherlive.com/en/auroral-activity/aurora-forecast.html#tab_kp. "+" and "-" are used instead of decimals with a 0.67 being 1-, 1 being 1, and 1.33 being 1+.

Edited February 19 by Jesterface23

[Guest]

8 hours ago, Jesterface23 said:

The 3-Day Geomagnetic Forecast for the Kp index is the same on both.

As I said, the Geomagnetic Forecast and the 3-Day Forecast are different as the NOAA links show. 

8 hours ago, Jesterface23 said:

The 3-Day Geomagnetic Forecast should match the Predicted Kp-indices here under the default Kp-indices tab

It does, but I'm not asking the difference between SpaceWeatherLive Kp forecast and NOAA forecast. 

[Newbie]

14 hours ago, Élie Bouhier said:

Hello,

I'm trying to find the best way to read aurora forecasts but I can't understand the difference between NOAA's 3-Day Forecast and NOAA's 3-Day Geomagnetic Forecast.
The former is used in the NOAA Aurora Dashboard whereas the latter is used by SpaceWeatherLive in the "Aurora Forecast" but they show widely different values.

For instance, at the time of writing this, one forecasts Kp 1.00 when the other predicts Kp 6.00 for 00-03 on Feb 18. On the other hand, one shows Kp 4.67 while the second says Kp 1.67 for 18-21 on Feb 19. 

Why are they different, what do they represent and which one should I follow/look at to see Auroras?

Kp is an index to represent Geomagnetic activity. The values range from 0 - 9.

SWL gives an explanation of what the graphics show on their aurora page.

The numbers shown are 3 hourly periods of time. Eg: 00-03 is 12-3 am and 18-21 is 6-9 pm UTC. It also shows min and max expected values for Kp. These values fluctuate over time as the solar wind is not constant. 

The NOAA dashboard has some good graphics showing the auroral oval. Whenever red appears on it there is good chance for aurorae/s to be observed provided you are in a favorable location. 

Find the Kp predictions from a magnetometer that is close to you, as Kp can vary from location to location. This may indeed be the reason why the values are different.

Kp values begin at Kp 0, no Geomagnetic activity, Kp 1, 2 -> 3, Kp 4 is considered active Geomagnetic conditions, Kp 5 is considered a Geomagnetic Storm G1, Kp 6 - G2, Kp 7 - G3, Kp 8 - G4, Kp 9 - G5 Geomagnetic storm. The further North (or South) you are, the greater the likelihood you will see the aurora at lower Kp levels. The higher the Kp value the greater the chance to see the aurora at lower latitudes.

N.

[RajSim]

16 hours ago, Élie Bouhier said:

Hello,

I'm trying to find the best way to read aurora forecasts but I can't understand the difference between NOAA's 3-Day Forecast and NOAA's 3-Day Geomagnetic Forecast.
The former is used in the NOAA Aurora Dashboard whereas the latter is used by SpaceWeatherLive in the "Aurora Forecast" but they show widely different values.

For instance, at the time of writing this, one forecasts Kp 1.00 when the other predicts Kp 6.00 for 00-03 on Feb 18. On the other hand, one shows Kp 4.67 while the second says Kp 1.67 for 18-21 on Feb 19.

Why are they different, what do they represent and which one should I follow/look at to see Auroras?

When I am looking at it now, I see the date when the forecast issued are different. 3-Day Forecast is the latest. Feb 21st estimates are matching on both of them, while Feb 19 & 20 are off. I look at the 3-Day forecast as it matches what is on the NOAA's dash:- https://www.swpc.noaa.gov/content/space-weather-enthusiasts-dashboard

[Jesterface23]

3 hours ago, RajSim said:

When I am looking at it now, I see the date when the forecast issued are different. 3-Day Forecast is the latest. Feb 21st estimates are matching on both of them, while Feb 19 & 20 are off. I look at the 3-Day forecast as it matches what is on the NOAA's dash:- https://www.swpc.noaa.gov/content/space-weather-enthusiasts-dashboard

Ah, pretty clear to see what you mean now. Learning something new every day. The actual SWPC Kp index values are filled in where the forecast was at the time of the update being issued.

Edited February 19 by Jesterface23

[Guest]

Alright so they're the same thing, the only difference is that the 3-Day Forecast is updated twice a day at 0030/1230 while the 3-Day Geomagnetic Forecast is only updated once a day at 2205 so the first one is the most up-to-date.

Just wondering why SWL uses the Geomagnetic one for the Aurora Forecast if it's not updated as frequently.

[Vancanneyt Sander]

2 uren geleden, Élie Bouhier zei:

Just wondering why SWL uses the Geomagnetic one for the Aurora Forecast if it's not updated as frequently.

Because the other report is manually updated by SWPC and has a higher chance of mistakes during automatic processing. Question should be asked why SWPC maintains two of the same 😉 . But also: is a mid-day update really an added value?