M-1 coupling observed: Concurrent measurements of precipitating and trapped
magnetospheric particle populations from a single vantage point

J.-M. Jahn (1), S. B. Mende (2), T. J. Immel (2), J. D. Perez (3), 
M. G. Henderson (4), C. J. Pollock (1)

(1) Southwest Research Institute, San Antonio, TX, USA, 
(2) University of California Berkeley, Berkeley, CA, USA, 
(3) Auburn University, Auburn, AL, USA,
(4) Los Alamos National Laboratory, Los Alamos, NM,


Simultaneous global measurements of precipitating protons with FUV imaging and of
trapped magnetospheric particles with energetic neutral atom (ENA) imaging from a
single vantage point provide a unique opportunity to directly compare the dynamics
of charged particles at two distant yet magnetically connected regions of space.
This approach provides a better insight in the connection between ionospheric
dynamics (e.g. measured with ground-based radars) and magnetospheric dynamics than
is possible with auroral imaging alone. To illustrate this approach, we are
presenting mainly results from a study of substorm events observed from the IMAGE
spacecraft since the summer of 2000. Events were chosen such that IMAGE was
located well above the equatorial plane, providing both a good view of the trapped
particle population in the inner magnetosphere and of the full auroral oval.
Trapped particles are investigated either through direct observations of measured
energetic neutral atoms, or through inversion of the ENA images into equatorial
ion flux distributions. Precipitating ions are observed either directly with UV
imagery, or through mapping of measured photon fluxes to the equatorial plane for
direct comparison with inverted ion flux distributions. We quantify the
development of substorms from growth phase through substorm expansion and
recovery, continuously comparing trapped and precipitating particle dynamics. A
discussion of other geomagnetic events (periods of enhanced magnetospheric
convection, geomagnetic storms) is also included in this presentation.
Specifically, we will discuss how convection electric fields can be detected and
evaluated using ENA measurements, and what can be expected in the future from
comparing ionospheric and magnetospheric electric potential maps.

_______________ 
Presented at the 35th COSPAR Scientific Assembly, Paris, France, July 18-25, 2004.