Kunio Hirao

Is Te equal to Tnm at the heights of 100 to 120 km

Abstract Low and mid-latitude lower E-region electron temperature profiles which were obtained by means of an insitu probe were collected. Profiles which are discussed here cover the heights of 90–120 km and measurement reliability at these heights is discussed mainly in terms of electrode contamination and aerodynamical heating. Although measurement errors might exist in some of the electron temperature profiles, it is conclusively described that daytime electron temperature is very often much higher than the possible neutral temperature and Te ≈ Tn is rarely seen.

Application of a glass‐sealed Langmuir probe to ionosphere study

A glass‐sealed Langmuir probe was developed to get accurate information on the ionospheric plasma. An electrode sealed in a glass tube is first baked in low pressure and tipped off the pumping system to keep the electrode surface clean. An essential advantage of the glass‐sealed Langmuir probe is that it will not require the rapid sweeping of a probe voltage for reliable data acquisition. It is noted that the glass‐sealed Langmuir probe is strongly recommended for the measurement of energy distribution of thermal electrons by the second harmonic method.

INACCURACIES IN ELECTRON DENSITY ESTIMATES DUE TO SURFACE CONTAMINATION OF LANGMUIR PROBES

Abstract Electron density in the ionospheric F region estimated by a Langmuir probe has been found to be much lower than those by other techniques. It is shown that this is due to the effect of surface contamination of Langmuir probe electrodes. This apparent reduction effect in electron density is more pronounced for a larger ambient electron density and for a slow sweep-rate of the probe voltage.

Distortions of the energy distribution of ionospheric thermal electrons near the focus of Sq current vortex

Abstract Energy distributions of the thermal electrons in the ionospheric plasma were measured on 16 January 1974 and 16 September 1976 by two Japanese rockets, K-9M-45 and K-9M-55 respectively near the focus of S q current vortex. The main effort was to investigate the energy state of the thermal electrons in a localized hot electron layer which occurs at a height of around 105 km in winter. The results obtained on 16 January 1974 showed that the thermal electrons in the hot electron layer had not a pure Maxwell distribution. While on 16 September 1976, the energy distribution of the electrons was found to be almost Maxwellian in the dynamo region as well as the F -region.

Structure and time variations of the Jovian ionosphere

Abstract The problem of the ionospheric formation in the Jovian upper atmosphere is examined. By adopting two plausible atmospheric models, we solve coupled time-dependent continuity equations for ions H2+, H5+, H+, H3+ and HeH+ simultaneously. It is shown that both radiative and three body association of H+ to H2 are important for the determination of the structure of the Jovian ionosphere. The maximum electron density in the daytime is found to be about 105 cm−3. It is also shown that diurnal variation with large-amplitude can exist in the Jovian ionosphere.

Rocket observation of conjugate photoelectrons in the predawn ionosphere

Abstract Photoelectron flux in the energy range 6–70 eV coming from the sunlight conjugate ionosphere has been measured directly by the rocket borne low energy electron spectrometer in the altitude region of 210–350 km. Pitch angle distribution of the measured flux is nearly isotropic, the flux decreasing slightly with pitch angle. The photoelectron fluxes measured at 350 km at the energies of 15 and 30 eV are 3 × 10 6 and 1 × 10 6 (cm 2 s str eV) −1 respectively which decrease to 1 × 10 6 and 1 × 10 5 at 250 km at the same energies. These values are consistent with the vertical profile of the 630 nm airglow intensity measured simultaneously. The fluxes obtained near apogee show peaks in the range 20–30 eV which also appear in the daytime photoelectron flux, indicating reduced loss of electrons during the passage from the conjugate ionosphere through the plasmasphere at the low geomagnetic latitude where observation was made. Photoelectron fluxes observed below the apogee height are compared to the calculated fluxes to investigate the interaction of electrons with the atmospheric species during the passage in the ionosphere. Calculated fluxes obtained by using continuous slowing-down approximation and neglecting pitch angle scattering are in good agreement with the observations although there still remain disagreements in detailed comparison which may be ascribed to the assumptions inherent in the calculation and/or to the uncertainties of the input data for the calculation.