Modeling the observed proton aurora and ionospheric convection responses to 
changes in the IMF clock angle: 1. Persistence of cusp proton aurora

K. Throp, M. Lockwood, B.S. Lanchester, S.K. Morley, H.U. Frey


We employ a numerical model of cusp ion precipitation and proton aurora emission
to fit variations of the peak Doppler-shifted Lyman-alpha intensity observed on
26 November 2000 by the SI-12 channel of the FUV instrument on the IMAGE
satellite. The major features of this event appeared in response to two brief
swings of the interplanetary magnetic field (IMF) toward a southward
orientation. We reproduce the observed spatial distributions of this emission on
newly opened field lines by combining the proton emission model with a model of
the response of ionospheric convection. The simulations are based on the
observed variations of the solar wind proton temperature and concentration and
the interplanetary magnetic field clock angle. They also allow for the
efficiency, sampling rate, integration time and spatial resolution of the FUV
instrument. The good match (correlation coefficient 0.91, significant at the 98%
level) between observed and modeled variations confirms the time constant (~4
min) for the rise and decay of the proton emissions predicted by the model for
southward IMF conditions. The implications for the detection of pulsed
magnetopause reconnection using proton aurora are discussed for a range of
interplanetary conditions.

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Journal of Geophysical Research, 110, A12311, doi:10.1029/2003JA010306, 2005