If a CME has a strong southward magnetic field it can create havoc with Earth’s magnetic fields, peeling back the outward layers like taking the skin off of an orange. And you probably remember from childhood that opposite magnetic poles attract. But if the red line goes below zero - the magnetic field direction heads south - then the incoming magnetic field is oppositely aligned to Earth’s. No problem there - the incoming magnetic energy simply slides right along with Earth’s own fields. When the red line is above zero, that means that the magnetic field hitting DSCOVR is heading primarily in the northward direction, the same as Earth. The north-south component (red) starts to plunge below zero - not all CME’s have a strong negative north-south component like this one did. The CME hits As the CME hits, DSCOVR’s total magnetic field readings (blue) get stronger.This CME was moving comparatively slowly, so no real shock is apparent.
Some CMEs leave the Sun so fast that they create a shock: a pile-up of solar wind plasma at their front end that creates jagged lines in DSCOVR data, like a Richter scale during an earthquake. (Further to the left you can see traces of a weak CME that passed by DISCOVR on Aug 24). Compared to a CME, the solar wind’s magnetic fields tend to be a little more chaotic - note the squiggly lines to the center-left of the graph. Before CME hits Before the CME hits, DSCOVR is surrounded by the solar wind.(You might be wondering: Why single out the north-south magnetic field strength (red) if it’s included in the total magnetic field strength (blue)? Because Earth’s magnetic field also runs along the north-south direction - and this leads to a very special interaction that can make CMEs especially dangerous. (The units are in nano-Tesla - named after Nikola Tesla, the famous physicist, engineer and inventor). The north-south magnetic field strengthon its own.The total magnetic field strength, a combined measure of the magnetic field strength in the north-south, east-west, and towards-Sun vs.Here’s a plot showing what DSCOVR saw before the CME hit it, while it was passing over, and after it passed. These data, and the unique view of a CME that they provide, are why DSCOVR is such a useful tool for NASA’s space weather forecasters, detecting CMEs between 15 minutes to an hour before they strike Earth. DSCOVR’s measurements track magnetic field strength and direction – two aspects of a CME that determine how much it will affect Earth. NOAA’s DSCOVR satellite (short for Deep Space Climate Observatory) watched it all go down. 26 it had hit - and aurora were visible as far south as Montana and Wisconsin in the United States. 20, 2018, a Coronal Mass Ejection - an explosion of hot, electrically charged plasma erupting from the Sun - made its way towards Earth.