Abstract
This paper presents direct observation of the impact of the lithium releases on the ionospheric electron density during the WIND (wind measurement for ionized and neutral atmospheric dynamics study) campaign conducted on 2 September 2007 in Japan. The direct observation is unique in that the electron density enhancement was observed by using the NEI (number density of electrons by impedance probe) which can measure accurately the absolute value of the electron density, and the distance between the NEI and the LES (lithium ejection system) was very close (several tens of meters). Data analyses of the NEI on-board the sounding rocket S-520-23, which was launched from Uchinoura (31.3°N, 131.1°E) at 19:20 JST (JST = UT + 9 h), clarifies that lithium releases performed in the descending phase increased the electron density up to approximately 7 × 105 cm−3. A simple model calculation performed under the assumption that the increased electron density equals the photoionized lithium ion density indicates that the observed electron density enhancements cannot be explained by considering each lithium release as an instantaneous one, but rather by considering a convolution of very short-time intermittent releases. The model calculation is verified by comparison with the observation of the lithium resonance scattering light from the ground.
Highlights
It is important to investigate expansion processes of released materials and its impact on the background physical quantities in space, since chemical releases enable us to observe physical values such as the thermospheric neutral wind and the electric field which are difficult to be observed
To evaluate quantitatively the lithium release impact on the ionospheric density enhancement during the WIND campaign, we analyzed the c( f ) data obtained from the NEI which can measure accurately the absolute value of the electron density
It was clarified that the lithium releases performed in the descending phase increased the electron density up to approximately 7 × 105 cm−3
Summary
It is important to investigate expansion processes of released materials and its impact on the background physical quantities in space, since chemical releases enable us to observe physical values such as the thermospheric neutral wind and the electric field which are difficult to be observed. Szuszczewicz et al (1996) reported the in-situ observation of the artificial multi ions during the El Coqui rocket campaign in which the distance from the canisters to the onboard instruments was approximately several hundred meters They found that the observations generally agreed with a simple spherical free expansion model except for multipeak characteristics due to the ion gyro-motion. The distance from a release point to a sensor is one of the important parameters of the chemical release experiment because the distance concerns what time stage of the expansion process we can observe
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