hehe i'm no scientist or academic just can read the 'form' as an aurora punter, its really not difficult to read once you are familiar with it, from this webpage
'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 wind" -- 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!
Southward Bz's often herald widespread auroras, triggered by solar wind gusts or coronal mass ejections that are able to inject energy into our planet's magnetosphere.'
from here
http://spaceweather.com/glossary/imf.html