Simultaneous generation of large-scale density irregularities and geomagnetic pulsations via filamentation instability
Article first published online: 14 MAY 2009
Copyright 2009 by the American Geophysical Union.
Geophysical Research Letters
Volume 36, Issue 9, May 2009
How to Cite
2009), Simultaneous generation of large-scale density irregularities and geomagnetic pulsations via filamentation instability, Geophys. Res. Lett., 36, L09107, doi:10.1029/2009GL037942., , , , , , and (
- Issue published online: 14 MAY 2009
- Article first published online: 14 MAY 2009
- Manuscript Accepted: 17 APR 2009
- Manuscript Received: 3 MAR 2009
- filamentation instability;
- density irregularities;
- geomagnetic pulsations
 Results of experiment conducted at Gakona, Alaska, using intensity-modulated HF heating waves of 3.2 MHz to generate geomagnetic pulsations and large-scale field-aligned density irregularities (FAI), are reported. The echo traces of o- and x-mode sounding pulses from 3.53 to 4 MHz were recorded during heater on/off periods. The ionograms showed that only x-mode echo traces were significantly affected by the HF heater. The returns from 3.53 to ∼3.8 MHz disappeared during heater on period and reappeared after heater was turned off. Ray tracings are performed to explore the effect of FAI on the backscattering of o- and x-mode sounding pulses. The drastic difference between the FAI effects on o- and x-mode backscattering trajectories provides a theoretical interpretation of the observation. Geomagnetic pulsations as large as 2.5 nT were also recorded by a Fluxgate Magnetometer. Thermal filamentation of the HF heater leads to the simultaneous generation of FAI and geomagnetic pulsations.