Daytime Aurora. Jøran Moen. (Newell ann Meng, 1992). Dayside Magnetospheric Boundary Layers. (Siscoe. 1991).
(Newell ann Meng, 1992)
Dayside magnetospheric boundary layers form adjacent to the magnetopause at the inner side. The dayside boyndaries are named Low-latitude boundary layer (largest surface against the solar wind), the cusp (most direct entry for shocked solar wind plasma, and plasma mantle (also called the high latitude boundary layer)
The above figure shows a statistical survey of plasma precipitation regions observed by DMSPsatellites at 850 km altitude. The classification scheme is based electron and ion energy spectra and fluxes in the 32 eV-32 keV energy range.
The MSP observations from Longyearbyen ion the rights, shows a transition from green-dominated aurora (577.7 nm) to red-dominated (630.0 nm). The red-dominted is identified as of BPS source (several keV electrons on closed field lines) and the red-dominated as of cusp source (~100 eV electrons on open field lines.
Lorentzen and Moen, JGR, 2000
Oksavik et al., accepted by Ann. Geophys., 2003
Notice the staircase stepped ion cuso, low energy electrons, field aligned currents signatures (magnetic field deflections) andE-field irregularities in the cusp.
Magnetic flux opened by magentopause reconnection convects across the polar cap, followed by tail reconnection and sunward return flow.
IMF Bz south
5-10 min recurrence time
The thick arrows indicate the magnetic tension for j x B which act to unbend the curved magnetic field lines
Notice the IMF By controlled east-west shift in the cusp inflow region during IMF Bz south conditions in favour of magnetopause reconnection.
Reiff and Burch, JGR, 1985
IMF-By controlled CUSP reconfiguration
The image sequence demonstrates the auroral response to an an IMF By polarity change from negative to positive. The polarity change was associated with a transition from westward moving to eastward moving auroral events, consistent with magnetopause reconnection and the magetic tension force. The time lag from IMF to the ionospheric response was around 15-20 minutes.
Moen et al., GRL, 1999
Moving auroral form
30 keV electron trapping boundary
X-line expansion into the 17 MLT sector