Excited! 9: Space Weather
Let's say that you're on a beach. Not just any beach—Eagle Beach, about 27 miles northwest of downtown Juneau, Alaska.
The sun has gone down behind you, and you're tromping back to camp with your new friends, the trail lit only by your headlamps. When you reach the road, passing under the orange glow of a sodium streetlamp, you hear George up ahead, whooping(!!) with irrepressible glee in her distinctive British accent. Everyone's conversations come to a halt. You look up.
Above the ink-black treeline? ✨The northern lights!✨ Faint, but beautiful. You pull out your phone to capture a picture:
Hrmmm. That's a bit …dark. You take a few more photos…
Wait! Don't worry! Tony snapped a photo on his point-and-shoot.
…but thaaaat's not what you remember seeing. That's spectacular and vibrant! No, it's more like …so:
Still spectacular, yet faint, …and unexpected.
You knew there was a forecast of high auroral activity, but it's only the first night of Alaska Robotics Comics Camp, and already (HOT DIGGETY DAAAANG) you—and the other campers—are excitedly ticking that box off your lower-latitudes bucket list.
In the wee hours later, on the trail between the campfire and the cabins, you crane your neck straight up. The sky looks like a veritable lightswitch rave.
WHAT is going on with this night sky?
What are auroras? How do people forecast them? And what do they have to do with the innards of our earth, the flatulence of a distant star, and …MAGNETS??!?
Are you ready? Let's learn about
💫SPACE WEATHER!💫
…WEATHER! IN SPAAAAAAAAACE!
Auroras are natural phenomena of shimmering lights that occur in the sky near the north pole (aurora borealis) and south pole (aurora australis). To understand what causes them, we need to direct our attention 93 million miiiiiiiiiiiiiiles away, to look at solar activity.
"The sun," as the song goes, "is a mass of incandescent gas is a miasma of incandescent plasma." Plasma is not solid, liquid, or gas, but a fourth state of matter—a gas that has been (often) superheated (in the case of the sun's core, we're talking millions of degrees!) to the point where it's ionized (atoms get so excited, their electrons are set free, splitting the atoms into electrically-charged component particles). So…not only is the sun giving off visible light and invisible radiation (such as x-rays), it's also producing superhot, electrically-charged plasma.
As plasma roils up in magnetic whorls to the surface of the sun, it plumes out steadily into space as "solar wind." Astronomers can predict how much or how little solar wind the earth will receive by watching for coronal mass ejections, or CME. This is what a CME looks like, courtesy NASA:
And while scientists are still working out the exact physics of what causes CME, they find they're often linked with telltale sunspots on the surface of the sun where a magnetic field is particularly strong. Sunspots tend to be adjacent to the sites of plasma-ejecting solar flares and solar prominences (...as you may notice below in the close-up view of a sunspot—look at those spicy magnetic field lines!).
The larger the sunspots (or the more of them) that astronomers see, the more intense the magnetic field activity on the surface, thus the more solar wind we're likely to get. Astronomers' observations give us advance warning of solar wind; while light takes only eight minutes and 17 seconds to get from the sun to the earth, fast solar wind can take anywhere from 18 hours to two days to traverse that same distance.
As you would expect, a SUPERHOT, ELECTRICALLY-CHARGED wind is not exactly something you want to be caught in (which we'll talk about in a moment). Thankfully, our planet has an invisible forcefield—a protective geomagnetic field—which takes the brunt of it.
A part of the geomagnetic field called the magnetosphere deflects the solar wind around Earth, but in the tail end of the deflection, some of the plasma gets trapped. As these charged particles build up in the tail, they draw the magnetic field lines ever closer, until there's an explosive magnetic reconnection, and the plasma snaps back along the magnetic field lines toward the earth's poles.
When this plasma hits the upper atmosphere, it excites the gases found there, and they phosphoresce—they kick off photons of light—, creating the aurora. The colors of the aurora are from the ions in the plasma interacting with different gases (nitrogen and oxygen) in different proportions at different layers of our atmosphere.
So to recap:
The aurora are caused when plasma (superheated, ionized gas) ejected by the sun gets trapped in Earth's magnetic field, then accumulates until it is explosively propelled toward the planet's poles, interacts with the gases of the upper atmosphere, and emits light.
•
•
•
But …uh, WHY do we care about the aurora?
First of all, observations of the aurora give us data about the shape and workings of the earth's magnetic field. For example, increases in sunspots and solar activity often correlate with aurora being seen at lower latitudes, closer to the equator.
While seeing aurora closer to the equator certainly sounds like a wonderful thing, it's generally ...not a good sign. For one thing, the plasma in solar wind has its own magnetic field, and when it slams into the magnetosphere, it can cause geomagnetic storms. A changing magnetic field will induce currents in wires (this is how generators work), so geomagnetic storms can fry circuits in spacecraft or even trip circuit breakers of power grids on Earth. It's similar to the electromagnetic pulse of a nuclear blast, and in fact, Cold War nuclear testing temporarily altered the earth's geomagnetic field and caused auroras.
How bad could it get? In 1859, long before we had a constellation of satellites overhead, a massive geomagnetic storm known as the Carrington event wreaked havoc with telegraph systems and created auroras over the northeastern US that were bright enough to read a newspaper by.
In 1989, at the height of the Cold War, a powerful geomagnetic storm jammed radio signals, interrupted satellite signals, caused blackouts in Quebec, and produced auroras as far south as Texas. In 2012, Earth dodged a solar superstorm when a "Carrington-class" coronal mass ejection missed our orbital trajectory by a matter of days.
Don't worry too much: NOAA has a Space Weather Prediction Center to provide early warnings and forecasts. And, as mentioned in that article linked above, astrophysicists have crunched the numbers and there's only a …ah ...12% chance that we'll experience a Carrington-class geomagnetic storm in the next nine years. (Thaaaaaat's not reassuring.)
YES PLEASE I WANT TO STARE AT THE AURORA AND ALSO POSSIBLY HELP SCIENTISTS
If you live in latitudes closer to the poles and see auroras, you can help with (NASA space plasma physicist) Dr. Liz McDonald's charmingly-named citizen science effort to track aurora sightings:
👉 AURORASAURUS 👈
(There's an interview with her about auroras on a recent Science Friday. Plasma is an invisible "glitter bomb"!)
Okay, I agree, space weather is more than a bit …exciting.
I KNOW, right?? Auroras and coronal mass ejections are only the faintest glimmer of what astrophysicists dig into for space weather studies! SERIOUSLY, Y'ALL: cosmic radiation and cloud chambers! Van Allen's radiation belts and the rockoons that helped understand them! polar wind! magnetohydrodynamics and flux tubes! the origins of the earth's magnetic field! red sprites, blue jets, and upper-atmospheric SPACE LIGHTNING! eleven-year solar cycles! mapping the innards of the sun with sound, through HELIOSEISMOLOGY! appreciating that interstellar plasma is what allows us to see distant stars! marvelling at photos of aurora on other planets! And lest we forget: Steeeeeeve!
(It was so very nice of you to forgive my pun about exciting.)
Unsurprisingly, space weather is complicated. I've cited sources, but if I've misrepresented anything about Earth's magnetic field, or you just want to TELL ME ABOUT MORE SPACE WEATHER, zap me a message on the usual hailing frequencies. ;)
Here's what's happened in the past fortnight in the world of code-named projects:
- [⋯] STRAYLIGHT continues apace. I've been working on implementing a CMS for the website and making lots and lots of budget spreadsheets. We're all going to be in the same city (for the first time in months) this week.
- [⋯] Looks like we'll wrap up version 1.0 of KIMON this week and press ahead to v1.5. Learning a lot about static-site generators!
- [⋯] In initial drafting stages with E for PINAX (a conference workshop).
- [→] ...no progress yet on HATCHEL x ARETHUSA. (Been a little bit busy with the first two projects above.)
- [→] Miiiiight be starting DIASPORA next month, another unofficial side project with C.
- [→] Nothing to report since last time on RIO GRANDE, COLLINS, HAMMERSTEIN, BOMBILATE, or BAYEUX.