MFACE
A high-resolution model of field-aligned currents
... EOF decomposition reveals that EOF1 represents mainly the Bz-controlled large scale R1/R2 current pattern whereas EOF2 represents the By-controlled cusp current signature.
For details cf.
http://dx.doi.org/10.1029/2012GL053168
http://dx.doi.org/10.1002/2014JA019776
http://www.faculty.jacobs-university.de/jvogt/mface/
Aurora current evolution at quiet levels of geomagnetic activity
https://youtu.be/wxuOZqJwjMs