polar cap patches

Zhang, Q., Lockwood, M., Foster, J., Zhang, S., Zhang, B., McCrea, I., et al. (2015). Direct observations of the full Dungey convection cycle in the polar ionosphere for southward interplanetary magnetic field conditions. Journal Of Geophysical Research: Space Physics. http://doi.org/10.1002/2015JA021172 (Original work published May 2015)