Global and Seasonal Scintillation Morphology in the Equatorial Region Derived from ROCSAT-1 In-situ Data

Abstract

The global/seasonal distributions of the scintillation occurrence rate are obtained from the in-situ density measurement of the ROCSAT-1 using a modified procedure reported by Wernik et al. (2007). A least-squares curve fitting in the optimal trust region is used to obtain the spectral slope for the density irregularity structure and the outer scale of the scintillation. The distribution of the S₄ index for the weak scintillation (S₄ < 0.3) is almost identical to that of the equatorial irregularity distribution reported in the literature. However, as the scintillation becomes stronger (0.3 < S₄ < 0.6), the latitudinal distribution moves to the equatorial ionization anomaly (EIA) region. In addition, the distributions of the outer scale values that are useful for the study of the physical evolution of the irregularity structure are also obtained. The occurrence distribution of scintillation activity with several parameters such as dip-latitude, longitude, local time, solar activity, and geomagnetic activity during different seasons are presented and discussed in this paper.