Ovation Auroral Forecast vs. Hemispheric Power

[Aurora Seeker]

Hi! I'm hoping you might be able to help me understand better the differences between the auroral forecast and hemispheric power. Currently, the auroral forecast map is showing the probability of visible aurora for the northern auroral oval area at perhaps 10-50% depending upon which area of the oval one looks at. But the Hemispheric Power chart is showing globally integrated total energy less than 20GW, which indicates there may be little or no aurora observable. 

 

The two measures don't seem consistent. Can you help me understand the difference? And perhaps also how to best use the information on your website to determine in real time the possibility of seeing an aurora in a certain location (in this case, the location I'm interested in is north of Churchill, Manitoba, at about 59 degrees latitude).

 

Thank you!
 

[Marcel de Bont]

The auroral forecast graphical map and hemispheric power chart come from the same model. There shouldn't be any difference. Remember the green colors on the map mean only a very small chance of visible aurora. Yellow and red colors indicate higher probabilities. Are you at Churchill at the coast of the Hudson Bay? If so aurora should be common there?

[Aurora Seeker]

Thank you so much for the quick reply!

We will be near Churchill August 5-11. I'm sorry to say I'm still kind of confused. 

The key shows that some of the brighter green colors indicate 50% probability of visible auroras, but the hemispheric power chart says below 20GW indicates little of no probability of a visible aurora. So, for example, at 5:45pm UTC (right about now), the hemispheric power charts shows 12GW, which would indicate little or no probability of a visible aurora, but the map shows some fairly bright green in some parts of the auroral oval. Can you help me understand how those two measures square?

By the way, if you have time for a specific question, I would be curious to know whether you think we are likely to see any aurora near Churchill August 5-11. Would auroras be common there even in this time of solar minimum? In your judgment, what sort of indicators on the geographical map and/or on the hemispheric power chart would we need to see in order to make it worthwhile for us to wake up to watch for auroras during the short times of darkness that week?

Thank you very much for your help!

[Marcel de Bont]

Hello. Just thinking about the location of Churchill I suspect the nights there will be very short so the chances of seeing aurora in the few hours it might be dark enough might be slim especially during the quiet solar wind conditions we are in now. https://www.timeanddate.com/sun/canada/churchill?month=8&year=2019

I assume you look at the map made by the NOAA SWPC. It is the map with a top down view over the arctic and not the 2D maps made by us. While the OVATION model is just a computer generated guide it does give you a quick overview of the aurora conditions in the very near future. But like you are saying. With values below 20GW the chance to see aurora is slim to none. Even at arctic latitudes I doubt there is much to see. I do think the color table the NOAA SWPC uses can be a bit deceiving. 12GW is really low.

I advice you to learn to read the solar wind data as well and combine all the information on the website to form your own opinion as to what to expect but you are on the right track already when you say below 20GW gives little or no aurora.

I do think Churchill is a good place to observe aurora if the skies become dark enough, you dont need much for aurora there but a little bit more activity might be needed. Maybe there is a coronal hole coming that could give you some aurora... https://www.spaceweatherlive.com/en/solar-activity/solar-images/stereo

[Aurora Seeker]

Thank you so much for taking time to explain all of this to me! I appreciate your sharing your expertise!