Observation of GPS Ionospheric Scintillation at UKM, Malaysia Aramesh Seif 1 , Mardina Abdullah 1,2 , Alina Marie Hasbi 1,2 , Yuhua Zou 3 1 Department of Electrical, Electronics and Systems Engineering, Faculty of Engineering and Build Environment, Universiti Kebangsaan Malaysia (UKM), 43600, Selangor, Malaysia 2 Institute of Space Science (ANGKASA), Faculty of Engineering and Build Environment, Universiti Kebangsaan Malaysia (UKM), 43600, Selangor, Malaysia 3 School of Electronic Engineering and Automation, Guilin University of Electronic Technology Guilin, China arameshseif@yahoo.com, mardina@eng.ukm.my, alina@eng.ukm.my, yhzou@guet.edu.cn Abstract— Ionospheric scintillation can cause serious effects on communication systems, therefore the study of ionospheric scintillation is very crucial especially in the equatorial region where scintillation activity is maximum. The paper presents the month-to-month variations of amplitude and phase scintillations over Malaysia for a period of nine months from January to September 2010. The scintillation parameters are measured by the GPS ionospheric scintillation and TEC monitor (GISTM) using a dual-frequency GPS receiver at UKM, Malaysia (2.55°N, 101.46°E). The observations during the solar minimum show daytime amplitude scintillations were observed in the months of January and February with maximum value of S4 index between 0.2 and 0.3, from 10:00-14:00 LT, while phase scintillations were rarely observed. Nighttime amplitude scintillations were observed in March and August with maximum value of S4 index in the range of 0.2 - 0.4 at 22:00-24:00 LT and usually occurred with phase scintillations. It was found that amplitude scintillations rarely occurred at daytime but occurred frequently during nighttime. Keywords-component; Ionospheric scintillation; TEC irregularity; GPS I. INTRODUCTION Ionospheric scintillation is known as rapid fluctuations of amplitude and phase of radio signals when they propagate through the ionosphere [1]. These rapid fluctuations are usually caused by electron density irregularities. Amplitude scintillations in GPS may cause degrading of positioning accuracy, cycle slips and data loss in GPS receiver, while phase scintillation can stress phase lock loops in GPS receivers resulting in the loss of phase lock [2]. The equatorial ionosphere is a region that consists of two ionization belts located approximately (±15 ̊) of the magnetic equator where scintillation has major effects [3]. At post sunset, the equatorial irregularities known as plasma bubbles are formed over the magnetic equator at the bottom of the ionospheric F-layer and then penetrate into the topside ionosphere. A few hours later, these irregularities map down the magnetic field lines towards the equatorial anomaly region, which results in intense scintillation effect [4]. The plasma bubbles include large scale irregularities ranging from tens of centimeters to tens of kilometers [5]. Previous ionospheric scintillation studies in the equatorial region showed that the nighttime ionospheric scintillation is more significant than daytime ionospheric scintillation [6, 7, 8]. On the other hand, small-scale electron density irregularities may occur in the ionospheric E-layer too. The sporadic-E (Es) layer, a very thin layer in the E region located at altitude between 90 and 100 km is another form of irregularity which is capable of producing radio wave scintillation of trans- ionospheric signals [9]. Previous research [7, 8, 10, 11] have unanimously indicated that daytime ionospheric scintillation are related to the E-layer irregularities such as sporadic-E irregularities (Es), while nighttime ionospheric scintillation are normally associated with spread F irregularities. It is known that ionospheric scintillation is a serious threat to the performance of GPS receivers as it degrades the signals [2]. Therefore, it is necessary to study the characteristics of ionospheric scintillation and also to consider the factors that cause it in order to overcome such a problem. Several studies conducted in the equatorial region showed that the occurrence of ionospheric scintillation varies with season, local time, geomagnetic activity and the 11-year solar cycle [12, 13]. This paper aims to study the equatorial ionospheric scintillation and total electron content (TEC) fluctuation using data recorded by the dual-frequency receiver at University Kebangsaan Malaysia (UKM) station, Malaysia (geographic: 2.55 ̊N, 101. 46 ̊E; geomagnetic: 7.39 ̊S, 173.63 ̊E) during the period of January to September 2010. This paper also presents the characteristics of daytime and nighttime GPS ionospheric scintillation. II. DATA AND METHODOLOGY In the analysis, the data recorded by the GISTM a dual- frequency receiver installed at UKM, Malaysia during the period between January and September 2010 is used. The GISTM system is able to track up to 11 GPS satellites at both L1 and L2 frequency bands at once [14]. It is known that amplitude scintillation can be monitored by computing the S4 index, which is defined as the standard deviation of the signal intensity (SI) that is received from satellites and is divided by its mean value [8]. This research is partly funded by the Malaysian Government through Universiti Kebangsaan Malaysia under the UKM-OUP-NBT-30-153/2011. Proceeding of the 2011 IEEE International Conference on Space Science and Communication (IconSpace) 12-13 July 2011, Penang, Malaysia 978-1-4577-0564-9/11/$26.00 ©2011 IEEE 45