September 21st, 2019 at 5:21 PM
Interesting...
https://science.nasa.gov/science-news/ne...-is-coming
High up in the clear blue noontime sky, the sun appears to be much the same day-in, day-out, year after year.
But astronomers have long known that this is not true. The sun does change. Properly-filtered telescopes reveal a fiery disk often speckled with dark sunspots. Sunspots are strongly magnetized, and they crackle with solar flares—magnetic explosions that illuminate Earth with flashes of X-rays and extreme ultraviolet radiation. The sun is a seething mass of activity.
Until it’s not. Every 11 years or so, sunspots fade away, bringing a period of relative calm.
During solar minimum, the effects of Earth’s upper atmosphere on satellites in low Earth orbit changes too.
Normally Earth’s upper atmosphere is heated and puffed up by ultraviolet radiation from the sun. Satellites in low Earth orbit experience friction as they skim through the outskirts of our atmosphere. This friction creates drag, causing satellites to lose speed over time and eventually fall back to Earth. Drag is a good thing, for space junk; natural and man-made particles floating in orbit around Earth. Drag helps keep low Earth orbit clear of debris.
https://science.nasa.gov/science-news/ne...-is-coming
High up in the clear blue noontime sky, the sun appears to be much the same day-in, day-out, year after year.
But astronomers have long known that this is not true. The sun does change. Properly-filtered telescopes reveal a fiery disk often speckled with dark sunspots. Sunspots are strongly magnetized, and they crackle with solar flares—magnetic explosions that illuminate Earth with flashes of X-rays and extreme ultraviolet radiation. The sun is a seething mass of activity.
Until it’s not. Every 11 years or so, sunspots fade away, bringing a period of relative calm.
During solar minimum, the effects of Earth’s upper atmosphere on satellites in low Earth orbit changes too.
Normally Earth’s upper atmosphere is heated and puffed up by ultraviolet radiation from the sun. Satellites in low Earth orbit experience friction as they skim through the outskirts of our atmosphere. This friction creates drag, causing satellites to lose speed over time and eventually fall back to Earth. Drag is a good thing, for space junk; natural and man-made particles floating in orbit around Earth. Drag helps keep low Earth orbit clear of debris.
![[Image: 5.jpg]](http://www.nodiatis.com/pub/5.jpg)
