Abstract
The High-Bandwidth Auroral Rocket (HIBAR) was launched from Poker Flat,
Alaska on January 28, 2003 at 07:50 UT towards an apogee of 382 km in
the night-side aurora. The flight was unique in having three
high-frequency (HF) receivers using multiple antennas parallel and
perpendicular to the ambient magnetic field, as well as very low
frequency (VLF) receivers using antennas perpendicular to the magnetic
field. These receivers observed five short-lived Langmuir wave bursts
lasting from 0.1–0.2 s, consisting of a thin plasma line with
frequencies in the range of 2470–2610 kHz that had an associated
diffuse feature occurring 5–10 kHz above the plasma line. Both of these
waves occurred slightly above the local plasma frequency with amplitudes
between 1–100 μV/m. The ratio of the parallel to perpendicular
components of the plasma line and diffuse feature were used to determine
the angle of propagation of these waves with respect to the background
magnetic field. These angles were compared to the theoretical Z-infinity
angle that these waves would resonate at, and found to be comparable.
The VLF receiver detected auroral hiss at frequencies between 5–10 kHz
throughout the flight from 100–560 s, a frequency matching the
difference between the plasma line and the diffuse feature. A dispersion
solver and associated frequency- and wavevector-matching conditions were
employed to determine if the diffuse features could be generated by a
nonlinear wave-wave interaction of the plasma line with the lower
frequency auroral hiss waves. The results show that this interpretation
is plausible.