The aurora borealis is normally seen solely manner up north, however two weeks in the past the evening sky was stuffed with shimmering curtains of pink and inexperienced mild that may very well be seen all the way in which down into the southern US. Individuals in Texas and Hawaii received out of their automobiles to stare and take footage.
The reason for this mild present was an particularly sturdy blast of photo voltaic wind—electrically charged particles shot out from the solar at unimaginable speeds. And there is extra to come back as we strategy the height of the present photo voltaic cycle, a interval of elevated photo voltaic storms that occurs each 11 years.
That is one instance of what scientists name “house climate,” which offers with the interplay between the solar and the Earth. Not all the implications of house climate are fairly, and a few are outright harmful. However the physics behind it are fairly cool. Let’s test it out!
Blowin’ within the Wind
You may consider the solar as a fantastic ball of fireside—nevertheless it’s not. (Hearth is a chemical response between oxygen and carbon.) What the solar is, actually, is a huge nuclear fusion reactor. Within the core, protons are smashed collectively beneath excessive strain. These protons stick collectively to create the nucleus of a helium atom, with two protons and two neutrons. (Two of the protons decay into neutrons).
Illustration: Rhett Allain
However wait! The helium nucleus has much less mass than the 4 protons we began with. That mass is not misplaced—it is changed into vitality, in response to Einstein’s well-known equation E = mc2, the place E is vitality, m is mass, and c is the velocity of sunshine. That final quantity is big—mild travels at 300,000 kilometers per second, and it is hugeness is squared—which signifies that even a tiny lack of mass creates A LOT of vitality. That is why the solar is so sizzling, with a core temperature of 27 million levels Fahrenheit. Yep, that is fairly sizzling.
Below this excessive warmth, the gases within the outer a part of the solar type a plasma during which electrons are ripped away from their atoms, leaving free electrical prices (largely electrons and protons) zooming round. A few of them are transferring quick sufficient to flee the gravitational pull of the solar. These ejected particles are what we name the “photo voltaic wind.”
You possibly can see the impact of the photo voltaic wind when it hits a comet. Comets are mainly massive soiled snowballs that orbit the solar in lengthy ellipses. As one nears the solar, its icy physique sublimates and turns right into a fuel. A few of this fuel beneficial properties sufficient vitality to be ionized (electrons are free of the atoms), leaving an electrically charged fuel. Then, when the photo voltaic wind hits, it pushes this ionized fuel away, making a tail that may be tens of hundreds of thousands of miles lengthy.
Enjoyable truth: You may suppose the tail extends out behind the comet like a jet contrail, nevertheless it does not! It extends away from the solar—so mainly sideways to the course of the comet’s movement.
Why Now?
However what causes the photo voltaic wind to get so labored up each 11 years? Nicely, like Earth, the solar has a magnetic area, nevertheless it’s extraordinarily unstable. As a result of the solar isn’t a strong object, completely different components of it rotate at completely different speeds. This causes its magnetic area to twist and warp, and each 11 years or so it truly flips and reverses polarity. This final occurred in 2013, and right here we’re in 2024.
These transferring magnetic area strains can break by means of the floor, creating solar spots and superior geysers of plasma often known as photo voltaic flares. Why does this occur? When electrical prices are zipping round, they are often pushed and pulled by a magnetic area. You possibly can see this your self with some copper wire and a battery. In case you place the wire close to a stationary magnet after which join the ends so a present flows, the wire will transfer. Test it out:
