[P-EM27] Physics and Chemistry in the Atmosphere and Ionosphere

[PEM27-P19] Analysis of DC electric field in ionosphere by S-520-26 sounding rocket

*Keigo ISHISAKA¹, Mamoru YAMAMOTO², Tatsuhiro YOKOYAMA³, Takumi ABE⁴, Shigeto WATANABE⁵ (1.Toyama Prefectural University, 2.RISH, Kyoto University, 3.NICT, 4.ISAS, 5.Hokkaido Univeristy)

Keywords:DC electric field, ionosphere, rocket experiment

S-520-26 sounding rocket experiment was carried out at Uchinoura Space Center (USC) in Japan at 5:51 JST on 12 January, 2012. The purpose of this experiment is the investigation of the bonding process between the atmospheres and the plasma in the thermosphere. S-520-26 sounding rocket reached to an altitude of 298 km 278 seconds after a launch. The S-520-26 payload was equipped with Electric Field Detector (EFD) with a two set of orthogonal double probes to measure both DC and AC less than 200 Hz electric fields in the spin plane of the payload by using the double probe method. One of the probes is the inflatable tube structure antenna, called the ITA, with a length of 5 m (tip-to-tip). And ITA is very lightweight (12.5g per one boom). The ITA extended and worked without any problems. It was the first successful use of an inflatable structure as a flight antenna. Another one is the ribbon antenna with a length of 2 m (tip-to-tip). The electrodes of two double probe antennas were used to gather the potentials which were detected with high impedance pre-amplifier using the floating (unbiased) double probe technique. The potential differences on the two main orthogonal axes were digitized using 16-bit analog-digital converter, sampled at 800 samples/sec with low pass filter at cut-off frequency of 200 Hz.
Results of measurements of DC electric fields by the EFD have the large sine waves that result from the payload rotation at the spin period. The largest contribution to the electric field measurements by double probes moving through the ionosphere at mid-latitudes is that due to the v X B fields created by their motion across the ambient magnetic field, where v is the rocket velocity in the Earth-fixed reference frame and B is the ambient magnetic field. The sum of the squares of the two components represents the magnitude of the DC electric field in the spin plane of the payload. These data reveal abrupt, large-scale variations which can immediately be attributed to changes in the geophysical electric field since the v X B fields are slowly varying. The sum of the squares data also reveals contributions at the spin frequency and its harmonics. These contributions result primarily from distortions of the waveforms in the raw data. Then we obtained three components of natural DC electric fields by subtracting the v X B fields from raw data. As a result, the magnitude of DC electric field on a rocket orbit during the ascent was about 1mV/m, and the direction was for north-east.