Global Ionospheric Response to Intense Solar Wind Forcing and Ionospheric
Coupling to the Magnetosphere and Plasmasphere

A.J. Mannucci (Jet Propulsion Laboratory, California Institute of Technology,
Pasadena, CA 91109), B.T. Tsurutani, B. Iijima, J. Goldstein, J. Kozyra, 
T. Fuller-Rowell, B. Wilson, X. Pi, G. Hajj, A. Komjathy, L. Mandrake, 
W.D. Gonzalez

We present the global ionospheric responses to selected intense southward Bz
interplanetary magnetic field events recorded over the last two years. Using
GPS data obtained from ground and space-borne receivers, ground-based
ionosondes, and ionospheric data from satellite altimeters, we show evidence
for global-scale, dayside ionospheric uplift consistent with eastward daytime
electric fields relatively soon after IMF southward turning. The increases in
integrated electron content observed at several altitudes below and within the
ionosphere appear over broad longitudinal regions (1000s of km), from
equatorial latitudes to greater than 50 degrees, and vary in magnitude from
20% to over 100% depending on latitude and altitude (increases are relative to
neighboring geomagnetically quiet days). Using ground-based observations of
total electron content (TEC), narrower (100s of km) tongue-like TEC features
are also observed at mid-latitudes during periods when the Dst index indicates
geomagnetic storm main or recovery phases. In north American mid-latitudes,
plentiful GPS ground-based observations suggest that late-afternoon/dusk
tongues are formed by plasma that is advecting sunward (westward) and
poleward, possibly due to the sub-auroral polarization stream (SAPS) electric
field. A sharp TEC feature in the central pacific is also captured at 60
degrees south latitude on October 30, 2003 by the ocean altimeter data, but we
do not fully resolve the observed TEC spatial structure. These southern
observations may be consistent with a tongue-like feature as seen in the
north. Further observations are necessary. These significant ionospheric
signatures of interplanetary southward magnetic fields will be discussed in
terms of prompt penetration of interplanetary electric fields, shielding, and
changes in thermospheric composition and winds. Ionosphere-plasmasphere
coupling is investigated using IMAGE EUV data.

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Presentation at the Yosemite Conference of Inner Magnetospheric Interactions,
3 - 6 February 2004, Yosemite, California, USA