11:00 AM - 1:00 PM
[PEM10-P16] The characteristics of electron energy distribution observed in the vicinity of the ionospheric Sq current system
Keywords:Ionosphere, Electron heating, Sq corrent system
Many sounding rockets have been launched in the mid-latitude around Japan. The electron temperature and electron density have been measured most frequently in these rockets. As a result of analysis of the electron temperature data, a case of local increase in electron temperature near the lower ionosphere around noon in winter has been reported. This phenomenon is most likely to be observed when a rocket passes near the center of the Sq current system, which occurs in the mid-latitudes of the winter hemisphere. The Sq current is a system of currents generated in the ionosphere by the Sq field (solar quiet variation), which is a component of the temporal variation of the magnetic field measured by ground-based observations. This current system is caused by the electromotive force associated with the tidal motion of the neutral atmosphere, and varies with solar time with a period of one day during periods of quiet geomagnetic activity. From ground-based observations and studies, it has been shown that the Sq current system exists in the daytime hemisphere, counterclockwise in the northern hemisphere and clockwise in the southern hemisphere, in the E region of the ionosphere at altitudes between 100 and 140 km.
The S-310-44 sounding rocket experiment was conducted to elucidate the generation mechanism of the high-temperature plasma layer near the center of the Sq current system in the lower ionosphere.
In our study, we discuss the current-voltage characteristics and electron energy distribution obtained from Fast Langmuir probe (FLP) onboard the rocket. Characteristics of the observational results will be presented.
Unlike ordinary Langmuir probes, a small-amplitude AC voltage was superimposed on the applied triangular wave voltage in the FLP on S-310-44 rocket. By extracting the second harmonic component of the current that changes due to the superposition, the second derivative coefficient of the V-I characteristic of the probe can be estimated and the energy distribution can be derived. In this study, we first discuss the relationship between the second harmonic component of the probe current and the probe voltage. Then, we compare the data that might be influenced the Sq current and the ones without the influence of the Sq current in the low altitude region. For data that is not affected by Sq current, the electron energy distribution likely obeys Maxwellian. In contrast, two peaks were observed to exist in the energy distribution, when Sq current may have influence on the data. This indicates the existence of multiple components of electron energy distributions. In order to examine a cause of the second component, we are focusing on the temporal variation of the current and voltage values of both peaks. In this presentation, the detailed result of our analysis will be described.
The S-310-44 sounding rocket experiment was conducted to elucidate the generation mechanism of the high-temperature plasma layer near the center of the Sq current system in the lower ionosphere.
In our study, we discuss the current-voltage characteristics and electron energy distribution obtained from Fast Langmuir probe (FLP) onboard the rocket. Characteristics of the observational results will be presented.
Unlike ordinary Langmuir probes, a small-amplitude AC voltage was superimposed on the applied triangular wave voltage in the FLP on S-310-44 rocket. By extracting the second harmonic component of the current that changes due to the superposition, the second derivative coefficient of the V-I characteristic of the probe can be estimated and the energy distribution can be derived. In this study, we first discuss the relationship between the second harmonic component of the probe current and the probe voltage. Then, we compare the data that might be influenced the Sq current and the ones without the influence of the Sq current in the low altitude region. For data that is not affected by Sq current, the electron energy distribution likely obeys Maxwellian. In contrast, two peaks were observed to exist in the energy distribution, when Sq current may have influence on the data. This indicates the existence of multiple components of electron energy distributions. In order to examine a cause of the second component, we are focusing on the temporal variation of the current and voltage values of both peaks. In this presentation, the detailed result of our analysis will be described.