Multipayload Sounding Rocket Observations Of Velocity Shear, Vlf Hiss, And Alfven Waves
The multipayload Cascades2 sounding rocket was launched on March 20th, 2009 at 11:04:00 UT into a pre-midnight poleward boundary intensification. Three papers are presented from two different time periods of the flight. On the upleg the payload array encountered a region of VLF hiss. During this time period the interpayload separation vector between two wireboom subpayloads was nearly aligned to B0 . This configuration was sufficient to directly measure the parallel wavelength of VLF hiss and create upper and lower bound estimates for the perpendicular wavelength. For the ~ 60km preceding entry into the polar cap the payload array encountered a region of intense, Alf´ nic e aurora which was characterized by large, fluctuating DC electric and magnetic fields, field-aligned auroral electron bursts, broadband extremely low frequency plasma wave emissions and elevated ion temperatures. A fully spatial analysis of the DC electric field signals was used to measure velocity shears of +/- 6Hz, a factor of two lower than single payload measurement of the same data would imply, but sufficient to drive electrostatic plasma wave emissions. An interferometric spatio-temporal analysis revealed that kilometer scale electromagentic disturbances were moving at ~ 8km/s across the payloads, which was similar to the velocity of tall aurora rays observed in optical aurora. Analysis of the power spectral density from the DC electric field found two break points in the spectral slope. The first breakpoint occurred near k[lamda]e > 1, where [lamda]e is the electron inertial length. The second breakpoint occurred at k[rho] s = 1 where [rho] s is the acoustic radius at electron temperature. Spectral fits were performed which revealed power laws of k[-]1.77 from DC to the first breakpoint, k[-]5 from the first breakpoint to the second breakpoint, and k[-]2 beyond the second breakpoint. The noisier fluctuating magnetic field spectra also followed a power law. A fit to these data reveals a k[-]2.37 power law. A polarization analysis of the despun DC electric field signals revealed that at scales longer than [rho] s the observed fluctuations were well described as plane waves, and at scales shorter than [rho] s observed BB-ELF were not well described as plane waves indicating they were Doppler shifted spatial structures.
plasma physics; aurora; northern lights; sounding rocket; interferometry; alfven; vlf hiss
Hysell, David Lee
Kelley, Michael Charles; Seyler, Charles Eugene
Ph.D. of Electrical Engineering
Doctor of Philosophy
Dissertation or Thesis