How to predict the Aurora
The following is a rough guide to get you going quickly, if you would like to understand further please see (What causes Aurora).
One of my favourite, and simplest, websites to understand at the moment is a fairly new Iceland one that collates all the required information and produces three very simple to understand gauges to predict Aurora, along with a 24-48 hour Kp outlook
NOAA Aurora – 30-minute forecast is also an excellent tool, translated alongside other information from the organisation throughout many apps and websites.
One of the most commonly known, and easily recognisable readings predicting the possibility of photographing the Aurora is the Kp index/outlook; it is predicted in advance, so you can prepare for the possibility of Aurora.
The Kp index is basically a grading scale for Auroral activity at different latitudes, ranging from 0-9, with the higher end of the scale predicting Aurora at much lower latitudes, such as Southern England and Northern France. Auroral activity can be detected within the magnetic field above as disturbance (measuring the maximum variation of the horizontal element of the magnetic field at its location); with magnetometers (see What Causes Aurora).
However, Kp is not actually a method of Aurora prediction as such, it’s an estimate of the approximate latitudes where it may cause disturbance; the Kp is a predicted outlook based on solar flare activity and predicted solar storms. Scientists use the Kp index to plot the probability of the latitudes Northern Lights may be visible at in relation to the Kp reading. An actual Kp reading is given after the disturbance within the magnetic field has been detected.
Through personal experience, I would take this with a pinch of salt, Kp5, which is effectively a G1 storm (lowest graded Geomagnetic Storm) is plotted to be visible in Northern Scotland; I would state it would be visible in Northern Ireland, Northern Wales, and Northern England, most likely with the glow, and flares visible to the naked eye, and picked up nicely on camera, with green glows possible on the horizon further south, such as some of the English Coast (Norfolk/Yorkshire), and Southern Welsh mountains.
A G1 storm will produce a decent display in more Northerly parts of Scotland, possibly visible almost overhead on the far north coast.
Solar wind is the stream of charged particles ejected from the sun, stronger speeds affect the Earth’s Magnetic Field leading to Auroral displays, the higher the reading on the gauge, the more chance of Aurora (solar wind speed fluctuates and solar wind predicted to hit Earth, often misses the planet).
Interplanetary Magnetic Field (IMF)
A little more complex to understand overall, but an easy enough gauge to understand, and undoubtedly, the most important when trying to see the Aurora as the interplanetary magnetic field needs to orientate to the southward for Aurora to occur; measured in Bz, and indicated southward by a -Bz numerical value, so, this gauge needs to read differently from the Solar wind, and Kp, leaning the other way into the minus values (the Bz fluctuates).