Sounding rocket

Abstract: Measurements of the intensities and profiles of UV and EUV spectral lines can provide a powerful tool for probing the physical conditions in the solar corona out to 8R ⊙ and beyond. We discuss here how measurements of spectral line radiation in conjunction with measurements of the white light K-corona can provide information on electron, proton and ion temperatures and velocity distribution functions; densities; chemical abundances and mass flow velocities. Because of the fundamental importance of such information, we provide a comprehensive review of the formation of coronal resonance line radiation, with particular emphasis on the H I Lα line, and discuss observational considerations such as requirements for rejection of stray light and effects of emission from the geocorona and interplanetary dust. Finally, we summarize some results of coronal H I Lα and white light observations acquired on sounding rocket flights.

Abstract: Shear Alfven waves with amplitudes greater than 100 mV/m were observed on two recent sounding rocket flights The largest waveforms are best described as a series of step functions, rather than as broadband noise or as single frequency waves Complete two-dimensional E and B measurements at 4-ms time resolution were made, showing a downward propagation direction and implying insignificant reflection from the ionosphere at frequencies greater than 1 Hz Intense, field-aligned, low-energy electron fluxes accompany the waves Acceleration of these electrons by the Alfven waves is shown to be feasible The waves in at least one case have a sufficently large ponderomotive potential to generate the observed density fluctuations of order one

Abstract: In June 1992 a NASA sponsored sounding rocket was flown through the Arecibo heater beam to study the structure of the heated volume. The rocket carried an instrument payload and traversed the 5.1-MHz reflection height at 268.5 km. Data from the plasma density probe are presented in this paper. The rocket passed through several regions of disturbed plasma both above and below the reflection level. In these regions, over 180 deep filamentary density depletions were detected. Measured perpendicular to the magnetic field, these depletions or filaments have a mean width at half maximum of 7 m which is roughly equal to twice the ion gyroradius (O + ) and a mean depletion depth of 6%. The ratio of parallel to perpendicular scale for these structures exceeds 20,000, and the spacing between the filaments is around 15 m. A power spectrum of the rocket data clearly shows the spectral content of the filaments and also reveals peaks at longer wavelengths which we interpret as the spacing between the bunches and between sets of filaments within a given bunch. We believe that previous scintillation and satellite measurements emphasized these longer wavelengths. The power spectrum measured by the rocket instrumentation falls off as k −4 for wavenumber k larger than 0.4/m and remains above the system noise for structure down to 1 m. It is clear that VHF backscatter from these structures can be explained by our data, as can many features of heater-related, field-aligned irregularities found in the literature.