SA53B-1581
Rocket Studies of Midlatitude Spread F at Wallops Island
A rocket was launched from Wallops Island, Virginia (37.95° N, 284.53° E, 67.5° dip angle) on October 30, 2007 at 12:12 AM during a midlatitude spread F condition. The spread F was likely associated with geomagnetic activity as indicated by high Kp levels a few hours before the launch. The instruments aboard the rocket measured the neutral wind, electric field and plasma density in the spread F region. These are the first in-situ observations of these fundamental parameters in a midlatitude spread F event. The results show the relationships between neutral winds, plasma drifts, and plasma density. These results will be compared to expectations stemming from various theoretical frameworks for midlatitude spread F.
SA53B-1582
The NASA STORMS Sub-Payload electric field observations
The NASA STORMS sounding rocket, 36.218, was launched at 00:10 LT on October 30, 2007 into a mid- latitude spread-F condition over Wallops Island. The rocket deployed instrumented main and sub-payloads. The sub payload instrument complement included a plasma impedance probe for measuring plasma density, a Langmuir probe for relative plasma density and temperature measurements and the daughter electric field experiment. Unfortunately the sub-payload coned badly upon deployment complicating the data reduction. Within this paper we present a description of our data reduction techniques which are based upon an all magnetic attitude solution for the sub-payload's complex motion. The attitude solution is used to present preliminary density and electric field observations within this mid-latitude spread-F event.
SA53B-1583
Signatures Of Wave Propagation In The Topside Ionosphere
One of the most powerful methods to study the Earth's ionosphere and other mediums and its interactions with the topside ionosphere is the Incoherent scatter (IS) radar. In order to determine the characteristics of the ionosphere the Arecibo Observatory uses 430 MHz radar for this purpose. The Arecibo radar is extremely powerful and sensitive and it is capable of making very accurate measurements of many ionospheric parameters. In this work, data analysis was performed with hydrogen and helium concentrations, electron density, and ion and electron temperatures for the period from March 7 - March 11, 2008. These records display radar data from twenty eight different altitudes (224 to 1248km of altitude with step of 38km) with an acquisition rate of about twenty minutes. Analysis of harmonic dependence by altitude and local time was performed using Fast Fourier Transform, giving dominant frequencies which allowed the reconstruction of the signal with periodicities bigger than 45 minutes. Finally, analysis of the data using Wavelets Transform method was applied in order to determine which the dominant frequencies in the different altitudes and time are. We analyzed periodicities lower than 16 hours. Previews results from the hydrogen and electron density and temperature shows some evidence of waves with periodicity around 7.5 hours propagating in the topside ionosphere that weaken with the decrease of altitude in the range studied. Same behavior was observed in the rest of the profiles.
SA53B-1584
Indices of ionospheric GPS phase fluctuation derived by using Hilbert-Huang Transform
Variations in phase and amplitude of the GPS signal have been used to monitor irregularities of the ionospheric electron density. Based on the Fourier analysis, fluctuations in the total electron content (TEC) recorded by ground-based GPS receivers have been derived the indices of Fp and fp to stand for the hourly and quarterly GPS phase fluctuations. However, it has been well known the ionospheric GPS phase fluctuation to be a non-stationary and nonlinear phenomenon. Therefore, base on the intrinsic and adaptive characters of Hilbert-Huang transform (HHT), we develop a new detrained procedure computing the indices of GPS phase fluctuation. Results confirm that the two indices derived by the HHT yield a better performance.
SA53B-1585
Coordinated observations of a nighttime medium-scale traveling ionospheric disturbance in 630-nm airglow and HF radar echoes
A nighttime medium-scale traveling ionospheric disturbance (MSTID) is studied with the SuperDARN Hokkaido HF radar and the OI 630-nm airglow imager located within the radar field of view at Paratunka, Russia (53N, 158E). On 8 December 2007, the MSTID propagating southwestward with a period of ~1 hour was first identified in optics by considering airglow intensity deviations from 1-hour running averages. Over the optical event, the radar was detecting ionospheric F-region echoes with poleward and equatorward Doppler velocities correlating, both spatially and temporally, with the airglow depletions and enhancements, respectively. The occurrence and velocity polarity of the observed echoes are consistent with the onset of the E x B plasma drifts caused by the MSTID-related electric field. These facts indicate that the MSTIDs are accompanied by oscillating polarization electric field structure in the F-region ionosphere.
SA53B-1586
Electron Density Structure in the Mid-Latitude Ionosphere observed from the Impedance Probe on-board the Recent Japanese Sounding Rockets
We will present observations of the ionospheric electron density by the impedance probe on-board two sounding rockets, S-520-23 and S-310-38. The S-520-23 sounding rocket was launched as a part of WIND campaign from Uchinoura Space Center (southern part of Japan) on 2nd September, 2007. The lithium gas was released three times to measure the neutral wind velocity. The lithium release disturbed frequency spectrums of the probe impedance and made it difficult to determine the electron density from the UHR frequency. We therefore attempted to estimate the electron density from the capacitance of an ion sheath surrounding the probe. It should be noted that the variation of the sheath capacitance indicated sharp enhancements of the electron density about 1-2 order of magnitude after the each lithium release. The result indicates that the photoionization of lithium caused a growth of the electron density. We also analyzed the impedance probe data on-board the S-310-38 sounding rocket. This rocket experiment was carried out on 6th February, 2008, in order to clarify the 3-dimensional structure of the E-region ionosphere. A height profile of the electron density along the rocket trajectory was successfully deduced from the UHR frequency in the altitude range of 90-157 km. The sporadic-E layer was observed both in up-leg and down-leg around the 100 km altitude. On the other hand, an unexpected depression of the electron density was found in the altitude range of 110-120 km. In this altitude range, the electron density was less than 1000 /cc, which was lower than the threshold of the observable density of the impedance probe. A neutral wind shear probably played an important role to produce such an unusual low density region.
SA53B-1587
A Miniaturized Plasma Impedance Probe For Ionospheric Absolute Electron Density and Electron-Neutral Collision Frequency Measurements
A fully integrated, low power, miniaturized Plasma Impedance Probe (PIP) is developed for small satellite constellation missions to create a map of electron density in the ionosphere. Two alternative methods for deriving plasma parameters from impedance measurements are discussed. The first method employs a frequency sweep technique, while the second employs a pulse based technique. The pulse based technique is a new method that leads to faster measurements. The two techniques necessitate different specifications for the front end analog circuit design. Unlike previous PIP designs, the integrated PIP performs direct voltage/current sampling at the probe's terminal. The signal processing tasks are performed by an off-chip FPGA to compute the impedance of the probe in the surrounding plasma. The new design includes self- calibration algorithms in order to increase the accuracy and reliability of the probe for small satellite constellation missions. A new feature included in this instrument is that the plasma parameters are derived from impedance measurements directly on the FPGA, significantly reducing the bandwith of telemetered data down to ground.
SA53B-1588
Aerodynamic Influence on Plama Impedance Probe Measurements in Sounding Rocket Missions
Plasma instrument measurements on sounding rockets are affected by the aerodynamics of the spacecraft body. The effects of density gradients and wake effects on the impedance of a dipole antenna for a sounding rocket mission are analyzed. A DSMC/PIC code is used to simulate the aerodynamic conditions encountered during three sounding rocket missions, the Sudden Atom Layers (SAL) mission, the Tropical Storms mission and the Equatorial Ionospheric Study (Equis)-II mission. Impedance data is analyzed using a Plasma Fluid Finite Difference Time Domain (PF-FDTD) simulation, which is a multi-species finite difference computational model of an antenna immersed in a homogeneous plasma. The PF-FDTD code is modified to include the effects of density gradients introduced by the flow structure around a spacecraft. The plasma frequency and upper-hybrid frequencies measured by the impedance probe are seen to be affected by the spacecraft wake. Estimates are obtained for the correction coefficients that are to be applied in order to account for spin- modulation effects on the electron density measurements.