Analysis of Whistler Mode Wave Injection Experiments with RPI 
on IMAGE Spacecraft

V. S. Sonwalkar and J. Harikumar
Electrical Engineering Department, University of Alaska Fairbanks, AK 99775, USA
Phone: 907-474-7276, Fax: 907-474-5135
email: ffvss@uaf.edu, harikuma@arsc.edu  HYPERLINK mailto:harikuma@arsc.edu    

D.L. Carpenter and T.F. Bell
STAR Laboratory, Department of Electrical Engineering
Stanford University, Stanford CA~94305-4055, USA
Phone: +1-415-723-3585, Fax: +1-415-723-9251
email:  dlc@nova.stanford.edu, bell@nova.stanford.edu

Whistler-mode experiments with RPI [1] offer an opportunity to greatly extend the 
observing power of IMAGE.  They would complement the already planned use of RPI as a 
sounder operating in the free space mode.  The objectives of this paper are: (1) to introduce 
the concept of whistler-mode probing experiments by RPI on IMAGE, discussing issues 
related to feasibility; (2) to discuss determination of wave normal direction of the returned 
signal (echo); (3) to discuss a number of outstanding science problems that can be 
addressed with these experiments; (4) to propose specific whistler-mode experiments.

The feasibility issues include radiation and reception of whistler mode waves by RPI 
antennas, accessibility of waves on the IMAGE (returned echo) and on the ground, 
detection of RPI signals in the presence of natural ELF/VLF activity (signal to noise ratio), 
and certain inherent limitations imposed by the instrument capabilities (e.g. power, pulse 
width, number of antennas).  The accessibility of transmitted waves on the ground and of 
the returning echo on the satellite are investigated using raytracing simulations.  

With certain reasonable assumptions about whistler mode propagation, the signal reception 
by three mutually perpendicular antennas of RPI allows determination of wave normal 
angles of the returned signals.  The wave normal information is important in determining 
the signal path, which in turn provides information on plasma boundaries and irregularities.

The outstanding science problems that can be addressed with these experiments include  
probing of plasmaspheric and ionospheric density structures and irregularities via wave 
propagation through these structures, excitation of lower hybrid waves by meter-scale 
irregularities, better understanding of wave-particle interactions through excitation of VLF 
emissions and the potential of these experiments for hot plasma diagnostics.
 
Finally we discuss specific experiments that can be conducted to investigate the science 
problems. 

References
[1] R. F. Benson, Radio Science Bulletin No. 285, pp.9-20, June 1998.