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High Bandwidth Auroral Rocket (HIBAR)

Launch date: 28 January, 2003

Launch time: 7:50 UT

Launch team: Principal Investigator: LaBelle, Samara, Harjes (Dartmouth); Kletzing, Bounds (University of Iowa)

Vehicle apogee: 350km

Location: Poker Flat, AK (65.13° N, 147.48° W)

Instrument list: Langmuir Probe, Particle Detectors, Electric Field, VLF/LF/HF Waves, HF Wave Interferometer

Photos

Main Science

The aurora borealis is caused by beams of electrons accelerated at altitudes 5000--10000 km above the Earth.  When the beam interacts with the atmosphere, it causes light emissions at 100-300 km altitude.  Understanding the interaction of this beam as it travels thousands of kilometers through the Earth's magnetosphere and ionosphere has been a longstanding problem in auroral physics.  Theory says that the beam generates intense waves which affect its own propagation, perhaps even destroying it before it reaches the atmosphere. In nature, this clearly doesn't happen. Why not?

The beam-generated waves are difficult to study in the ionosphere because they occur at frequencies greater than 1 MHz, and in the past spacecraft data telemetry rates have been inadequate to sample such waves. Recently, much enhanced telemetry rates have become available on NASA sounding rockets allowing waves up to 5 MHz to be thoroughly measured. Instruments exploiting this capability are flying on an ongoing series of rockets launched from Alaska into the active aurora borealis. PHAZE-II and Auroral Turbulence II were launched in 1997; RACE and SIERRA were launched in 2002. 

Figure 1 below shows a key discovery from the PHAZE-II rocket.  The data are displayed in the form of a spectrogram which represents the time variations of the radio frequency waves.  Frequency is on the vertical axis, flight time is on the horizontal axis, and dark, gray, or white coloration denotes strong, moderate, or weak radio waves at a particular frequency and time.  The data in the figure come from about 330 km, where the rocket penetrated an auroral electron beam.

Figure 1.

The dark patches show intense waves near the fundamental resonance frequency of the ionosphere, generated by the auroral electron beam. The high resolution allows us to see that the waves are not constant in time or frequency. They consist of many pieces, each one of which lasts only a short time, which tend to come in groups, and which tend to decrease in frequency with time. This first observation of the detailed structure of these beam-generated waves is an exciting development in auroral physics which has stimulated a theory for these structures. This theory will be tested with HIBAR (High Bandwidth Auroral Rocket). According to this theory, the high frequency waves generated by the auroral beam can form standing waves in electron density cavities. These standing waves, analogous to the resonant waves in microwave cavities or the acoustical waves on a drum surface, occur at certain fixed frequencies determined by the geometry of the density cavities. The theory of these standing waves predicts a relationship between the frequencies of each component of the waves and their wavelengths. HIBAR will measure both the frequencies and the wavelengths with sufficient resolution to determine whether or not the theory is correct.

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Photos courtesy of Chuck Johnson and Hank Harjes.