physics

Posted by Ellen

The night owls who officially discovered–and named–Steve are the members of a Facebook group called Alberta Aurora Chasers. They are folks who like to stay up late and drive out to remote pastures and mountain valleys, even when the winter nights are insanely cold, which they often are in the prairies and Rockies of western Canada–all in hopes of a chance to enjoy big, unpolluted views of shimmery aurora borealis lights in the northern sky.

Steve is the name the aurora chasers borrowed from the children's movie Over the Hedge and applied to a particular, somewhat unusual aurora-like phenomenon, streaks of purple light that ripple vertically from the horizon instead of dancing horizontally along it like a normal, well-behaved, aurora. Normal auroras are produced when electrons thrown off by the sun approach earth, where they are pulled by our magnetic field toward the north and south poles. As they collide with gas molecules in the upper atmosphere, they can put on a bright light show.

Steve, scientists thought at first, could be generated by protons instead of electrons crashing into our atmosphere. But a professor of physics and astronomy at the University of Calgary, Eric Donovan, suspected otherwise; proton collisions, he thought, wouldn't give off much visible light for aurora chasers to photograph and enjoy.

In 2016, Donovan was able to track down something he thought might be an instance of Steve that was picked up by a satellite flying right overhead in Alberta. So he went on Facebook and asked the Alberta Aurora Chasers if they'd seen anything that night, at that location.

They had noticed it and photographed it. Donovan correlated their photos with the satellite data and concluded that Steve wasn't technically an aurora at all; it was a ribbon of extremely hot gas flying through space, more than 3,000 degrees Fahrenheit hotter than its surroundings.

Donovan believes the Steve discovery demonstrates the potential of "citizen scientists" to leverage data from satellites and other instruments in our brave new world. Of course, it also demonstrates what happens, à la Boaty McBoatface, when digital anybodies are charged with coming up with names for stuff.

Posted by Ellen

Gravitational waves–the warping of spacetime predicted by Einstein and confirmed the other day by a bunch of astrophysicists–may account for this awesome icicle hanging from a porch roof near Winthrop, Washington.

The way we understand it, which is undoubtedly not correct, the physicists measured data regarding a collision between two black holes and detected gravitational waves propagating outward from the event, kinda like sound waves rippling out from the ringing of the cosmic spacetime bell.

So. Obviously, this here icicle got caught up in some serious gravitational ripples. That, or the snow on the roof was seriously sliding and slumping and refreezing as the icicle was drippily trying to grow (see below). Hope the astrophysicists have ruled out that possible source of noise in their data.

Posted by Ellen

This image is from a computer model of a sunspot. Notice the scale bar at the bottom--that's not millimeters but Megameters: 1 Megameter = 1,000 kilometers.

Sunspots are occasionally visible to the naked eye near sunrise or sunset, if they are particularly large and if there's haze or thin clouds to partially dim the sunlight. Since the middle of the nineteenth century, it's been known that they have something to do with the sun's magnetic field, and that they may have consequences for electrical activity here on earth. We know that sunspots come and go in cycles lasting about eleven years and that years of high sunspot activity are often characterized by relatively cold weather. But even today, people who know a whole lot about sunspots say they don't understand them all that well.

The complex interaction of magnetic forces, superheated gases, the sun's huge gravitational field, and the nuclear reactions that keep stars glowing can't all be modeled in detail on a Macbook. In fact, supercomputing power has only recently become available in support of such a project, and this simulation of sunspot activity--published last June by researchers from the National Center for Atmospheric Research in Boulder, Colorado, and the Max Planck Institute in Germany--is said to be the first comprehensive model. The sunspot itself is represented by the dark spot in the middle; it's a sort of blob of solar gas that no longer glows white-hot like the rest of the sun because it's been ejected from the main solar body by a fierce magnetic storm. Once it's ejected, the gas is not part of the ongoing nuclear reaction heating the sun.The blob cools down a bit and shows up dark compared to the glowing disk of the sun, though it's still plenty hot. It doesn't  fly off into space because the sun's gravity keeps it trapped, but it can't reconsolidate into the main solar body because of magnetic forces. All these processes and more are computer-modeled to produce a sort of movie in which a sunspot is born, grows, and eventually dies. The colors of the imagery reflect the relative heat of the gases.

The authors of this model admit it is flawed; the gas flares near the edges of the penumbra are sized incorrectly. They say they know how to fix this issue but do not yet have the super-supercomputing power they would need to do the job right.

Sunspot activity is correlated with cold weather on earth because the blobs of dark, relatively cool gases block a bit of the sun's heat from radiating out to the earth. The years 2009 and 2010 are fairly high sunspot years in the eleven-year cycle, so we shouldn't be surprised if this winter winds up relatively cold--not abnormally crazy cold, but perhaps on the cold side of average. The sunspot effect may become less noticeable, however, as global warming progresses;  even if we collect a little less heat than average from the sun this year, relatively more of that heat will be trapped in our atmosphere by greenhouse gases, and relatively more of this year's heat will still be trapped in our atmosphere next year and the year after that. Each year, the trapped heat is becoming relatively more important in controlling our weather, and small fluctuations in heat input caused by sunspots are becoming relatively less important.

The magnetic storms associated with sunspot activity, however, remain extremely important. Disruptions in the sun's magnetic field can wreak havoc with sensitive electrical equipment here on earth, even causing major blackouts in the electrical grid. It has been suggested that if we understood sunspots better we might eventually learn to predict them.