1. Space Weather How fast does solar activity affect Earth?

2. The inner image is the Sun in red light, and the outer portion is normal, white light, but with the Sun blocked. The “bubbles” flying out are Coronal Mass Ejections (CMEs). The Sun’s “atmosphere” Is called the Corona. The Sun, as observed by SOHO.

3. Large flares (sudden releases of huge amounts of energy, akin to explosions) often accompany a CME. The white little streaks that flood the image are from protons and electrons accelerated by the flare to speeds near that of light slamming into the CCD camara.

4. Space weather affects our Earth and the entire solar system. It causes beautiful auroras but damages our spacecraft, satellites (and so, our communication), airline passengers, and astronauts. Above is a sketch of a CME running into our Earth’s atmosphere. Above right is an image of Earth’s aurora. To the right is a picture of the aurora on Jupiter.

5. Today we will measure the velocity of a CME. Since it is an image, we will only be measuring the two-dimensional velocity, a lower limit. By using a ruler in units of Solar diameters, we effectively put a huge ruler out in space. Each image in the sequence has a time. Pick a spot you can find in every picture and measure the distance at each step.

6. Convert your distances to meters with R Sun = 6.98e8 m What speeds do you get? How fast would the CME reach Earth? D Sun-Earth = 1.5e11 m

7. Everything is moving, and therefore has a measurable speed and acceleration. These are two comets that got too close to the Sun and never came back out.