Abstract
The SRP-4 rocket was launched at 12:07 LT on 18 March 2002. The objective of this rocket experiment is the investigation of the electron density profile in the high-latitude D-region of the ionosphere at noon. The Low frequency and Medium frequency band radio Receiver (LMR) and the DC Probe System (DPS) were installed on-board the rocket to estimate the D-region electron density. The LMR measured the intensities of radio waves received from ground-based stations operating at 257 kHz, 660 kHz and 820 kHz, respectively. The DPS measured the electron current and the positive ion current using the biased electrodes. The electron density profile at altitudes below 90 km was estimated from the measured absorption of these radio waves. It was found that the electron density began to increase at the altitude of 52 km and was larger than that estimated by the International Reference Ionosphere model at altitudes from 74 km to 89 km.
