our astronomy presentation today which covered the sun and its corona was interrupted by a call of “Northern Lights”. We all scurried out of the lecture hall and up to deck 9. It was snowing and blowing and that didn’t matter. However there was nothing to see by the time we arrived on deck. The crowd thinned in a few minutes. We remained on deck for twenty minutes. Conditions change rapidly and you never know when the lights will appear.
We heard John, who was on deck near us say, “Yes, I suppose I’ll continue the presentation in a few minutes.” We went back to the lecture hall.
What was most interesting was John’s description of how the Northern Lights form. According to john the solar wind distorts the earth’s magnetic fields back and away from the earth away from the sun. Sometimes the magnetic fields are forced together which fires the charged particles trapped behind the earth back along the collapsed magnetic fields towards the north and down along the lines of magnetic field. The Northern Lights are caused by particles descending through the atmosphere to earth! The solar magnetic field can point slightly north or south of the earth’s magnetic field. If it points slightly south, it turns on the possibility of northern lights. If the solar magnetic field switches slightly north of the earth’s Northern Lights will go out.
So what drives a big solar wind which can result in dramatic northern lights? First john described the effect of collapsed sun spots as sources of bursts of particles that enhance a solar wind and if directed toward earth can cause dramatic northern lights. It is rare to have solar spot generated northern lights. Sun spots have a periodicity of years. There was a minimum number of solar spots in 2008-2009 and we have entered another period of minimal sun spots.
The largest contributor to a northern lights display is the presence of a coronal hole. A coronal hole is a huge expanse of a hole in the corona from which high energy particles stream. There is now a huge hold in the sun’s corona facing the earth. It is about 1/5 the width of the sun and in the sun’s northern hemisphere. As the sun rotates in 27 days, the coronal hole reaches and maintains peak over a 4 or 5 day period before moving to the back side of the sun. We are now approaching the end of the 4th day the coronal hole faces earth. THIS is why John had his astronomical cruise during this past week and on this particular ship, the Trollfjord. He said he will return in another 27 days to chase the Northern Lights again. There is no guarantee that they coronal hole will return in 27 days, though it is extremely likely.
John is arranging other astronomical cruises around the world for other significant astronomical events! “No, I don’t do social media and I do not have time for a blog”, was John’s answer when I asked how I could contact him in the future. I’ll give him my email address.
There’s a quiz about our cruise starting in a few minutes. I promised Ellen I’d join her there. solvaer, Magic Ice, and last night’s 3AM wait-see will have to wait as will additional photos of our most wonderful Norse trip.