Transcription
Hey folks, we're going to do a bit of space weather awareness this evening. We'll have a basic lesson and an advanced lesson, with one leading right into the other.
We are starting with the basics, and there has been some confusion among newer viewers about sunspots versus coronal holes, so let's begin there. Sunspots are the surface magnetic areas that appear dark in visible wavelengths. You can see them with solar telescopes, but when we look in the ultraviolet wavelengths, they appear very bright. Whereas the coronal holes then reveal themselves as the dark patches you can see here. The coronal holes and sunspots have opposite returns in the UV spectrum. This is because sunspot fields are closed, containing electrified plasma emitting ultraviolet, while coronal holes are dark in UV due to a lack of particles. But in visible wavelengths, they appear as nothing. You still see all the white light emission from those areas. Coronal holes spew enhanced solar wind. Wind constantly, it is always flowing outward from them due to the open, outward-streaming magnetic fields.
But this is not how we describe the space weather impact of sunspots. They can be calm as can be, or they can release a solar flare and coronal mass ejection. So, in addition to the polar opposite appearances in both visible and UV light, the sunspots release acute shockwave blasts, while the coronal holes deliver more of a stream of enhanced particles in the solar wind.
Now let's look at those outward-streaming fields of coronal holes a bit more in our advanced lesson. They not only allow more significant streams of solar wind to emanate, but those coronal hole magnetic fields reach out across the entire solar system. The black and white hashed lines you see on the enless spiral are those fields connecting to objects like the Earth and the other planets, and back at the sun, they're connected at coronal holes. These fields are also what get juiced up during big flares and deliver high-energy protons to Earth, sometimes even when the flare is not facing the Earth, due to the curvature of the fields in the Parker spiral. This is also why the coronal hole earthquake watches begin before the solar wind arrives. That solar wind usually takes about three days after the coronal hole is directly facing Earth, but the magnetic fields connect instantly, and along with them, Alfvén wave emission. These are moving at about the speed of light, so it takes them only about eight minutes to arrive. And while we are awaiting the solar wind from the coronal holes, we're already taking the Alfvén waves and the magnetic field influence. This makes coronal holes a less flashy, but equally important geophysical actor from the sun compared to sunspots. It's why we offer them as much coverage as we do to sunspots, especially since those sunspots are often quiescent and not flaring. Again, in the ultraviolet view, coronal holes are dark, but the sunspots are very bright. Both can make geomagnetic storms, however, and impact geophysical conditions.
I'll see you in the morning for The Daily Show. Be safe, everyone.