Tuesday 7 February 2023
On this full disc Hydrogen Alpha image of the Sun, note the tiny bright blip on the East (left) side just above centre. This was not realised at the time of taking but that is the start of an eruption and you will see in later images how it grows vastly. At the bottom of this page is an animation of just 4 images with the time (Universal time = GMT) on each frame to show how rapid this event took place.
Rough measurement indicates to me that it was erupting at probably in excess of 100 km per second.
Size of Earth on my screen = 4mm
Diameter of Earth 12 740 km
Distance on screen eruption moved in 33 minutes = 70mm
So Speed of eruption = 70/4 Earth diameters in 33 mins
= (70 X 12740)/(4 x 33 x 60) km/s = 112 km/s
Below is a short animation of this eruption taken from the SDO website at helioviewer.org
That website also indicates that the speed is just over 200km/s so I am pleased with my rough estimate above.