Agri Faturahman, Claudia Amelia Lomban, Jiyo, Prayitno Abadi, Rezy Pradipta
Ionospheric irregularity is a fluctuation of plasma density in the upper atmosphere. Spread F (SF) occurs when "irregularities" are found in the ionospheric F layer. Ionospheric irregularities variability still needs to be studied because each region has unique characteristics. We tried to investigate the SF occurrence rate over Kupang station, Indonesia, during 2014 (around the maximum peak of the 24th solar cycle). We manually identify the SF occurrence rate from ionograms recorded by CADI (Canadian Advanced Digital Ionosonde). We grouped SF events into four types (range SF/RSF, frequency SF/FSF, mix SF/MSF, and strong SF/SSF) and then analyzed the occurrence rate. We found for seasonal variation, the SF most occurred in June solstice, with the dominant SF type being FSF. In addition, for all SF types that were identified during 2014, we never found a strong type (SSF). Further, we analyzed the effect of geomagnetic activity on the occurrence rate of each SF type. During the June solstice, the FSF and RSF types arose more on quiet days than disturbed days. On the other hand, MSF is dominant when geomagnetic activity is disturbed. For all seasons, the occurrence rate of RSF is higher when geomagnetic activity is disturbed. © 2023 American Institute of Physics Inc.. All rights reserved.
Research Center for Space, National Research and Innovation Agency (BRIN), Bandung, 40173, Indonesia; Planetary and Atmospheric Sciences Study Program, Institut Teknologi Sumatera (ITERA), South Lampung, 35365, Indonesia; Research Center for Climate and Atmosphere, National Research and Innovation Agency (BRIN), Bandung, 40173, Indonesia; Institute for Scientific Research, Boston College, Newton, 02459, MA, United States