Cluster Observations of ELF/VLF Signals Generated by Modulated Heating of the Lower Ionosphere with the HAARP HF Transmitter

MANUEL PLATINO; UMRAN INAN; TIMOTHY BELL; JOLENE PICKETT

Snowmass, Colorado, Estados Unidos

Workshop; GEM Summer Workshop; 2003

Rice University

Modulated HF transmissions have been a well established method for generation of ELF/VLF signals, using the so-called "electrojet antenna".  Although most observations of the generated ELF/VLF signals have been realized on the ground, several low- and high-altitude satellite observations have also been reported by H. G. James et. al. [1990].  One of the important unknowns in the physics of ELF/VLF wave generation by ionospheric heating is the spatial extent of the radiating source regions.  Multiple spacecraft observations with the CLUSTER/WBD instrument provide an excellent opportunity to determine the extent of the magnetospheric regions illuminated from the lower ionospheric regions heated by the HF transmitter, from which one can (via ray tracing) estimate the spatial extent and distribution of  the ELF/VLF source regions. For this purpose, ground-satellite conjunction experiments have been conducted during the past few months between CLUSTER and the HF High-Frequency Active Auroral Program (HAARP) facility in Gakona, Alaska.  The HAARP facility is a highly agile and modern instrument, which is currently being upgraded to quadruple its radiated power and antenna array size by 2005. Once completed, this facility will be the most powerful HF heater in the world, capable of producing ELF/VLF waves at intensities ten times higher than ever before. Being located on largely closed field lines at L=4.9, HAARP is currently also being used for ground-to-ground type of ELF/VLF wave-injection experiments, and will be increasingly used for this purpose as it is upgraded.  In this poster,we present recent results of the HAARP-CLUSTER experiments.