HR: 1400h
AN: SM33C-01    [Abstracts]
TI: Sounding rocket wave electric field measurements with a new all-digital, ultra-low noise receiver
AU: * Colpitts, C
EM: cac@dartmouth.edu
AF: Dartmouth College, Department of Physics and Astronomy, Hanover, NH 03755, United States
AU: LaBelle, J
EM: James.W.LaBelle@Dartmouth.EDU
AF: Dartmouth College, Department of Physics and Astronomy, Hanover, NH 03755, United States
AU: Kletzing, C
EM: craig-kletzing@uiowa.edu
AF: University of Iowa, Department of Physics and Astronomy, Iowa City, IA 52242, United States
AU: Bounds, S
EM: scott-bounds@uiowa.edu
AF: University of Iowa, Department of Physics and Astronomy, Iowa City, IA 52242, United States
AB: In February/March of 2007 the sounding rocket CHARM (Correlations of High-frequencies and Auroral Roar Measurements) will be launched from Poker Flat, Alaska. This rocket will carry the standard Dartmouth High- Frequency wave Electric field receiver (HFE), a wave-particle correlator to correlate the Langmuir waves with the auroral electrons and a new all-digital, ultra-low noise, precise-bandwidth wave electric field receiver (RX-DSP) which will attempt the first modern rocket-borne measurements of auroral roar. The RX-DSP will feature a high speed 66 MHz, 16-bit analog to digital conversion at the input and flexible programmable all-digital processing. For CHARM, two of these receivers will be flown, using mutually perpendicular double probe antennas which are both perpendicular to the rocket's spin axis, which is aligned with the earth's magnetic field. Each receiver will be tuned with an extremely sharp band pass filter to the typical frequency range of auroral roar observed at ground level in northern alaska, 2.6-2.9 MHz. These instruments will measure two components of both the wave electric and magnetic field, allowing estimation of the polarization and direction of arrival of the roar, as well as its amplitude along all points of the rocket's trajectory. Using these measurements, together with electron distribution functions and wave measurements from a ground station, this rocket experiment will serve to answer several outstanding questions about auroral HF emissions. Among these is the question of whether the intermittent nature of auroral roar observed on the ground is due to ionospheric effects or to actual temporal or spatial variations of the auroral roar source. Because ionospheric absorption of these waves is significant, accurate direct measurements with rockets are required to estimate the global power level of these emissions. The direction-finding capability of the CHARM measurements will allow ray tracing to determine the source location, which together with the amplitude data will reveal the source of the intermittency of the ground based observations. Another question CHARM measurements, specifically the direction finding, will allow us to answer concerns the source sizes of the roar emissions and their temporal variation. Furthermore, using the measurements of the electron distribution function in conjunction with the auroral roar measurements, we also hope to determine whether auroral roar is associated with auroral precipitation events such as suprathermal electron bursts or certain segments of inverted-V events or whether the roar is more favorable emitted in the upward current region or downward current region. Lastly, if the rocket penetrates the source region of the roar, the RX-DSP would give us information about the electric fields of the causative upper hybrid waves. Answers to these questions would significantly improve our understanding of auroral roar emissions, as well as highlight the capabilities and possible future uses for the RX-DSP.
DE: 2407 Auroral ionosphere (2704)
DE: 2471 Plasma waves and instabilities (2772)
DE: 2483 Wave/particle interactions (7867)
DE: 7868 Wave/wave interactions
DE: 7894 Instruments and techniques
SC: SPA-Magnetospheric Physics [SM]
MN: 2007 Joint Assembly