Proton aurora dynamics in response to the IMF and solar wind variations

S.-W. Chang, S.B. Mende, H.U. Frey, D.L. Gallagher, and R.P. Lepping


On May 23, 2000, proton auroras observed by IMAGE FUV on the dayside were very
dynamic. Auroral pattern at the cusp footpoint is well correlated with IMF and
solar wind parameters. A proton aurora brightened at high latitude poleward from
the dayside oval after solar wind ion temperature increased while solar wind
density and bulk speed were steady. It then vanished after IMF turned southward.
Under this IMF condition, auroral activity occurred only in the dayside oval. As
IMF Bz reverted to northward, cusp proton aurora reappeared at high latitude.
The location of the cusp proton aurora changes with the IMF By polarity,
consistent with previous reports. These results suggest an upstream source for
the observed high-latitude cusp proton aurora. One possible explanation is that
bow shock energetic ions are transported into the cusp via the high-latitude
magnetic merging process to induce optical emissions in the ionosphere. 

_______________
Geophysical Research Letters, 29(13), 1648, doi:10.1029/2002GL015019, 2002