Sir, – Contrary to "Winter solstice marked by sightings of the Northern Lights" (December 21st), the winter solstice was actually on December 22nd at 4:49 GMT.
The spectacular auroral displays observed in Ireland and across the globe on the evening of December 20th and early morning of December 21st therefore occurred more than 24 hours before the 2015 winter solstice. These displays were expected and were associated with a large geomagnetic storm detected early on December 20th by scientific instruments on a number of European Space Agency and Nasa spacecraft and at Trinity College’s observatory at Birr Castle.
Wishing you and your readers an astronomically happy new year! – Yours, etc,
Prof PETER T
GALLAGHER,
Solar Physics
and Space Weather Group,
Trinity College Dublin,
Dublin 2.
Sir, – Ah, there’s a grand stretch in the evenings. – Yours, etc,
KEVIN McDONNELL,
Berrings,
Co Cork.