Electroverse by Cap Allon 2/18/2020
No sunspots. No solar flares. No gust of solar wind. In short, there was no reason to expect an outburst of auroras on Feb. 17… then this happened ^^^ [featured image shot by A. Kuznetsov in Kilpisjärvi, Finland on Monday].
Both the Sun and Earth have magnetic fields, though the Sun’s isn’t confined to the immediate vicinity of the star — solar wind carries it throughout the entire solar system.
As the excellent Dr. Tony Phillips over at spaceweather.com explains, out among the planets we call the Sun’s magnetic field the “Interplanetary Magnetic Field†or “IMF.†Because the Sun rotates (once every 27 days), the IMF has a spiral shape, named the “Parker spiral†after the scientist who first described it.
Earth’s magnetic field, on the other-hand, forms a defensive bubble around our planet called the magnetosphere which exists, in part, to deflect the solar wind gusts. Earth’s magnetic field and the IMF come into contact at the magnetopause; a place where the magnetosphere meets the solar wind.
Earth’s magnetic field points north at the magnetopause. If the IMF points south –a condition scientists call “southward Bz“– then the IMF can partially cancel Earth’s magnetic field at the point of contact.
“When Bz is south, that is, opposite Earth’s magnetic field, the two fields link up,†explains Christopher Russell, a Professor of Geophysics and Space Physics at UCLA. “You can then follow a field line from Earth directly into the solar windâ€â€“or from the solar wind to Earth.
South-pointing Bz‘s open a door through which energy from the solar wind can reach Earth’s atmosphere — the event often heralds widespread auroras, triggered by solar wind gusts or coronal mass ejections (CMEs) that are able to inject energy into our planet’s magnetosphere.
More:
https://electroverse.net/a-crack-just-opened-in-earths-magnetic-field/
