 Greetings and welcome to the Introduction to Astronomy. In this lecture we are going to talk about solar activity, which we've been talking about, and lead into space weather and how things in space can affect the climate here on Earth. So let's go ahead and see and review a little bit what did we look at with solar activity. Well we talked previously about sunspots. Now that's not the only type of activity that we get. We also get other areas, and we're going to look at a few of those here, including the plages, which are brighter and denser regions that we see in the surface, and we can see those in an area around here. They are associated with the sunspots as well, but they're spread out over a much wider area. So they're not confined to just the dark sunspot, but a lot of region around that as well. We also have prominences, now prominences are visible around the edge of the sun. So we can see that as loops of plasma that are lifted off the surface, and we see one here to the left hand side, where material has been ripped off the surface by the solar magnetic field. So as the magnetic field pops through the surface, it lifts up material, and it's very good at lifting ionized material. And since the sun is a ball of gases, ionized gases, called a plasma, it's very good at lifting some of that material up, which will then rain back down on the surface. However, you can also get these in a more violent form, which we call solar flares. And that is when even more material is ripped off the surface, but it's done in a much more violent form. What might have taken days or a week slowly lifting up material and slowly falling back down is here a rapid eruption of material that can happen in minutes. So that material snaps off and throws that material not just up above the sun, but out from the sun altogether. And this is one of the ways that we can get material to Earth to cause the aurora. The other one is a coronal mass ejection, which is ejecting the coronal material at very high speeds. So this will be a rapid ejection of material, particles that are spune out, and these ones can also interact with the Earth's atmosphere, and can significantly impact communications by damaging or interfering with the electronic devices. So how can these affect Earth? Well, certainly sending material towards Earth does have an effect on us. And this is noted, we've actually seen solar storms affect Earth in the past. And in fact, the large one in 1859, where a coronal mass ejection was directed toward Earth and overloaded our magnetic field. What did this do? Well, aurora were seen in Hawaii, and aurora further north were actually bright enough to see by easily at night. So tremendous number of particle striking Earth's atmosphere, deforming Earth's atmosphere, and therefore making it easily visible at much lower latitudes where you would never ordinarily see aurora. It also affected the technology of the time, which would have been the telegraph. And sparks and fires were caused on telegraph equipment from all that electrical energy and the telegraph wires. Now today, a magnetic disturbance could cause significant damage to electrical equipment and damage to the electrical power grid. A strong enough coronal mass ejection coming toward Earth could fry many satellites. And even equipment here on Earth, unless it is sufficiently hardened to protect against such events. So it is very strong and the Sun can put out a lot of energy. So the good thing is that Earth is a very small cross-section. So while solar flares and coronal mass ejections go on all the time, the odds of one coming directly toward Earth are relatively small. But we could still expect one every few hundred years or so, so it's quite possible that another one could come in the near future. And there's no way to predict exactly when it would come, it just happens on how everything is aligned at the time when that material is ejected from the surface. Now you can use the NOAA Weather Prediction Center and the website is listed here that predicts what is going on and changes to the Sun and when solar flares and coronal mass ejections may be coming in Earth's at least general direction. So how does this tie into weather on the Earth? And the question is, is there a connection between solar activity and Earth's climate? Well, there is the Maunder Minimum, which we've mentioned before, between 1650 and 1700 here, and that was when there were cooler temperatures on Earth. And the solar activity was a minimum. You can note there, yeah, there were a few sunspots, but certainly not the regular cycle that we get. So normally we see every 11 years or so we get a nice big peak of sunspots, sometimes a little less, sometimes a little more. And we have seen in this case there was low solar activity, which corresponded with cooler temperatures. Now how does that work in the past? Well we don't really know, we don't have complete models here. So we know that the Sun was warmer before that the Earth was warmer before that we had the medieval warm period. Where things were a little bit warmer, here's the little Ice Age, again a lot of that associated with that region right in here, which was around the Maunder Minimum. So where it was a little bit cooler than average. But of course nothing was perfectly lined up. And we don't have the sunspot values going back here pre-1600 to really be able to say were the sunspots unusually active there. So we have to still, we're still trying to make models, there's difficulty in models trying to show such an impact. Are there other reasons that we're missing? Do we need new models? As is always done in science, that's what our scientific method is all about, trying to find the best way to try to fit and explain the data that we see. So let's go ahead and finish up with our summary. And what we've looked at this time is that solar activity shows in a variety of ways, we talked about prominences, flares, and coronal mass ejections. The solar flares and coronal mass ejections can impact us here on Earth. They could cause damage to electronic devices, to our power grid. If they were directed directly at Earth, if they came straight to Earth, that would be very, very damaging. However, again, Earth is a very small cross-section. So any individual solar flare is much more likely to miss Earth than to hit Earth. There's also a possible connection between solar activity and climate, but that is uncertain. Models still need work really to be able to see and try to better explain what might be happening here. So that concludes this lecture on solar activity and space weather. We'll be back again next time for another topic in astronomy. So until then, have a great day, everyone, and I will see you in class.