Aurora borealis: Northern Lights could be visible tonight in the UK
Tonight you could be in with a chance of seeing the Northern Lights - weather permitting.
It is just a month since the last sighting of the aurora borealis in the UK but the return of a large coronal hole to the Earth facing side of the Sun means our chances of seeing the Lights have again increased.
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The Met Office has said particularly the northern half of the UK are in with a chance of seeing the lights tonight.
But unfortunately heavy fog which is expected could mar the chances of seeing the spectacle.
How does this happen?
Firstly, the Sun goes through an 11 year solar cycle, from solar minimum, through solar maximum and back to solar minimum. We are now in the declining phase of the solar cycle following the solar max which occurred in early 2014. During the current phase of the solar cycle coronal holes that begin the cycle in the Sun’s ‘polar’ regions have now migrated towards the Sun’s equator, meaning they are on a similar line of latitude to the Earth (i.e. facing the planet rather than directed north and south out of the solar system). These coronal holes give rise to high speed solar wind streams that buffet the Earth, disturbing the Earth’s magnetic field.
In other parts of the solar cycle these disturbances are largely as a result of coronal mass ejections, which can give larger magnitude disturbances than these high speed streams.
Secondly the season of the year has an influence. The science behind this is not fully understood, but the two equinoctial periods in spring and autumn tend to produce an increase in aurora compared with winter and summer.
What does this mean for the UK?
We are now in a period, lasting a few weeks, where these two factors are working together to increase the chances of geomagnetic disturbances, which in turn bring with them the aurora. The strength of the disturbance directly relates to how far south the aurora is visible (or how far north if you are in the southern hemisphere), and of course you need clear skies to see it.
Northern Lights - a good chance of seeing them tonight where the sky clears. Best in dark spots further north. pic.twitter.com/Fu2JpedHAS— Barra Best (@barrabest) November 2, 2015
If it's cloudy tonight you won't see the Northern Lights. The easiest way to tell if it's cloudy is by sticking your head out the window.— Barra Best (@barrabest) November 2, 2015