Effects of solar activity on ionospheric current system in the Southeast Asia region
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ORIGINAL PAPER
Effects of solar activity on ionospheric current system in the Southeast Asia region N S A Hamid1,2*
, N I M Rosli1, W N I Ismail1 and A Yoshikawa3
1
Department of Applied Physics, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor, Malaysia 2
Space Science Centre, Institute of Climate Change (IPI), Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor, Malaysia
3
International Center for Space Weather Science and Education (ICSWSE), Kyushu University, 53, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 8128581, Japan Received: 03 February 2019 / Accepted: 28 November 2019
Abstract: The equatorial ionospheric current system is composed of equatorial electrojet (EEJ) and solar quiet (Sq) that flow in the eastward direction. That being mentioned, this study looked into the changes in ionospheric currents stemming from geomagnetic storm disturbances at different levels of solar activity during solar cycle 24. This analysis was performed by employing an EEJ index known as EUEL, which is calculated from northward geomagnetic component data measured using ground-based magnetometer at five different latitudes across the Southeast Asia region. Based on the outcomes, the impacts of geomagnetic storm on EEJ currents were observed at 1200 LT and 1100 LT, respectively, during high and low solar activity levels. Time delay was associated with changes in EEJ peak time at varied activity levels. This case study reveals that EEJ value at peak time of high solar activity decreased significantly during the main phase of geomagnetic storm. Keywords: EEJ; Solar quiet; CME; Ionosphere; Solar activity level PACS Nos.: 94.20.Vv
1. Introduction Coronal mass ejection (CME) refers to a solar event that erupts a group of plasma and magnetic field from the Sun’s corona into the interplanetary space. CMEs arise most often during high solar activity, in comparison to low solar activity, mainly because the Sun is very active due to higher sunspot numbers. The erupted plasma and magnetic fields travel through the interplanetary space as solar wind, and it takes approximately 3 days before this wind could interact with the Earth’s magnetosphere, which depends on the strength of both eruption and solar wind speed. The interplanetary magnetic field, which is in direction opposite to the northward direction of Earth’s geomagnetic field, generates geomagnetic storm. The occurrence of this event stems from the reconnection process that happens in front of the Earth’s magnetosphere [1, 2]. The reconnection process allows high energy particles to penetrate into
Earth’s atmosphere and interact with air particles to form an aurora at regions with high latitude. Figure 1 illustrates an instance of the CME event captured by the satellite obtained from Solar and Heliospheric Observatory (SOHO) catalogue. The geomagnetic storm that is caused by CME has the potential to disrupt the current system at equatorial ionosphere region. The current system in E layer of equatorial ionosphere comprises of two main curre
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