Aurora Borealis - when can I see it?
I am often asked how I know when the aurora is around & where best to see it , so here is the lowdown on where I find my info.
First take the long view.
I need to know in advance what nights are going to be high on activity & for this I use metcheck.com This forecast gives a broad day to day indication of expected KP levels
What do KP numbers mean? The KP number is a system of measuring geomagnetic activity. It ranges from 0 to 9 (0 - very weak, 9 - major geomagnetic storm with strong auroras likely). So when looking at the aurora forecast page, you want to see high KP numbers.
So although change is likely from day to day, this forecast is a strong indicator of when to get prepared.
2 days before indicated activity
My next checker is NOAA, this dashboard gives 3 day predictions on activity including sunspots which create the solar wind which gives us spectacular aurora activity, with lots of useful info. ( more on this later)
At this point I will also be looking at the weather forecast to see what the cloud levels are going to be like, as the aurora can only be seen in clear skies.
This is where the main body of info comes into play.
As the light goes on the evening of expected activity, I will be checking back in with NOAA to view the ovation prime model
In this model, which displays the Northern hemisphere, with the UK right of centre, the area covered by green shows visible activity, and stronger activity shows yellow or red depending upon strength.
This model is run in real time so if you see yellow or red in the central green mass over Scotland , sightings are highly likely as long as the skies are clear.
(click on the image to go to the NOAA page)
Next is prior to and during the hunt.
There are many good sites out there for on the spot info, but the one I find works best for me is the Glendale Aurora app, which I can access on my phone while out on location
This app gives detailed immediate information about the strength & direction of solar wind (which you want to be as strong as possible & in a southerly direction) This can change within a matter of minutes, meaning the difference between massive activity & nothing at all.
To make it easier, this app can be set to issue alerts to your phone when activity is strongest.
This app gives really user friendly explanations of the data in each section, making understanding the seemingly endless data much easier, in addition to a live map of where users are currently able to see the aurora (or not!)
What I look for on this site are a substorm in the recovery or expansion phase (top right of image)
and the imf/ Bz centre right. Looking for a big difference between the Bz & Bt data
This data can also be seen on the solar wind chart as shown here.
In the top section, a wide gap between the red & white lines is good for activity, in addition to wind speed (yellow line) in the 500km/s or higher.
Select your viewing spot
To have the best chance of seeing the aurora, even on a less than red-alert night, you need to be well away from street lights and have clear skies, which means it will be cold and very very dark. You cannot see the aurora from behind cloud, only through gaps in cloud, so the rule of thumb is, if you cannot see stars, what you are looking at isn't aurora.
Pick a location as high as possible, where you can look to the North with nothing blocking your view and take a torch! On nights with weaker activity, the aurora can be fairly low in the sky, so hills or mountains in front of you may inhibit your view.
Above - The Kilsyth Hills hiding the KP7 activity in November 2017
Below - The unobstructed view from Fintry
Below - View from the top of the Kilsyth Hills early in the activity on the same evening.
As it happened I had completely missed the forecast for this huge event in November, but thankfully the Glendale app alert going like mad meant that I could (quite literally) drop the food shopping & shoot off up into the hills.