Circum-pan Pacific Magnetometer Network Research Articles

The First Solar Flare Effect Observation at UiTM-SID Station during Solar Cycle 23-24

International Heliophysical Year (IHY; 2007-2009) has a remarkable impact on space and earth electromagnetism research and society. For Malaysian perspectives, it acts as a spiral point to the expanding of space weather-related research. The research activities involve installation of real-time Magnetic Data Acquisition System of Circum-pan Pacific Magnetometer Network, i.e. MAGDAS/CPMN for space weather study and application, which was deployed for the IHY; 2007-2009. In addition to MAGDAS system, to understand the characteristics of the lower ionospheric layer (60-150km) during space weather events, a Very Low Frequency (VLF) monitoring system has been developed. The MAGDAS and VLF monitoring system called UiTM-SID are located at Universiti Pendidikan Sultan Idris, UPSI (3.71’, 101.53’), Malaysia. The first observation effects of solar flare during November 2016 to March 2017, for the period of a minimum solar cycle 23-24 have been examined on sub-ionospheric VLF signals from VTX4 (19.2 kHz) and NWC (19.8 kHz) transmitter monitored at UPSI. In general, the level of amplitude reading for VTX4 signals is higher than NWC signals for quite diurnal variations. The effects of the solar flare class C7.5 on 29th November 2016 shows an enhancement of amplitude due to increase in the lower region electron density by the radiation of solar flare. The average daily amplitude reading was compared to the average value of solar flare event, the result shows the percentage difference is 12% increased in VTX4 and NWC signals.

The first solar-powered Magdas-9 installation and possible geomagnetically induced currents study at Johor, Malaysia

The Magnetic Data Acquisition System (MAGDAS-9) was successfully installed at Universiti Teknologi MARA Johor, Pasir Gudang Campus, Malaysia (JOH station), under the joint collaboration between International Center for Space Weather Science and Education (ICSWSE), National Space Agency (ANGKASA) and UiTM Johor. This is the first solar-powered magnetometer under the Magnetic Data Acquisition System of Circum-pan Pacific Magnetometer Network (MAGDAS/CPMN). In this paper, construction process, installation process and analysis of first geomagnetic observations at MAGDAS JOH station are presented. In addition, analysis on time derivative of horizontal component of geomagnetic field (dH/dt) to indicate the possibility of Geomagnetically Induced Currents (GIC) occurrences is also presented in this paper. The obtained geomagnetic components: H, D, Z and Total F are approximately similar to World Magnetic Model 2015 (WMM2015) while the diurnal variation from this geomagnetic observation showing a good variation pattern. The analysis of dH/dt has indicated 2 significant events of GIC.

Remote Data Acquisition and Archival of Magnetic Data Acquisition System (MAGDAS)

The University of Kyushu, Japan, has established partnerships with 30 international organizations to form the Circum-Pan Pacific Magnetometer Network (CPMN). The CPMN establishes a network of magnetometers placed around Earth’s equator for space weather research and applications. Due to its proximity to Earth’s equator, the Magnetic Data Acquisition System (MAGDAS) was installed in the Langkawi National Observatory (LNO) on 4th of September 2006. Due to several issues with manual collection of data for archival purposes, this paper presents a MAGDAS Remote Data Acquisition and Archiving System (MRDAS) developed for the purpose of MAGDAS data acquisition and backup. Design and implementation of the MRDAS development was done using MATLAB r2015a. The data was acquired using File Transfer Protocol (FTP) access, in which the setup is described in this paper. Several important functions of the MRDAS system were implemented in the Graphical User Interface (GUI). Data is stored in the Google Drive cloud storage to ensure ease of access among researchers working in various Malaysian National Space Agency (ANGKASA) offices. The MRDAS system was successfully implemented, and was able to acquire real-time data directly from the MAGDAS device. Application for remote data acquisition is for the space weather research.

Longitudinal Variation of EEJ Current during Different Phases of Solar Cycle

The equatorial electrojet (EEJ) is an eastward current flow around the dip equator in E-region of the ionosphere within the range of 90 to 120 km altitude. The longitudinal variation of EEJ was studied using the ground-based measurement from six different longitudinal sectors. The ground magnetometer data were provided by magnetometer networks such as those from Magnetic Data Acquisition System (MAGDAS) /Circum-pan Pacific Magnetometer Network (CPMN), Indian Institute of Geomagnetism (IIG) and International Real-time Magnetic Observatory Network (INTERMAGNET). The EUEL index used in this study was calculated from geomagnetic northward H component. The H-component was normalized to the dip equator using the CM4 model. This study present results of the longitudinal variation of EEJ during the three phases of solar cycle 24: solar minimum (2008), inclination phase (2011) and solar maximum (2014). Results show that EEJ current is higher in the American sector and lowest between African and Indian sector in 2008 and 2011. On the other hand, during the year of solar maximum, this current component is comparable in American and Southeast Asian sector.

Effect of SC on frequency content of geomagnetic data using DWT application: SC automatic detection

In this paper, a study is made to determine the effect of sudden commencement (SC) on the power spectrum of geomagnetic data using multiresolution analysis (MRA) of the discrete wavelet transform (DWT). The results of this study provides a guide to develop a new technique to automatically detect the SC because it could be an indicator of the onset of a geomagnetic storm. This new technique divides the original time series into different frequency sub-bands using the MRA of the DWT. Then it detects the change in a certain sub-band which shows a large change due to the SC. The geomagnetic records used in this study were 3-s resolution data collected from the Circum-Pan Pacific Magnetometer Network (CPMN). Using such high-resolution data enables us to minimize the detection error and the processing time to make a decision. The proposed algorithm is tested on one sample every three seconds of data sets collected from the CPMN. The maximum standard deviation of the algorithm detection times is observed to be fifty four seconds of the corresponding arrival times as determined by the National Geophysical Data Center (NGDC).

A Wavelet Spectral Analysis Technique for Automatic Detection of Geomagnetic Sudden Commencements

Maximal overlap discrete wavelet transform is used to perform spectral analysis of geomagnetic storm sudden commencements (SCs) (SSCs). This spectral analysis guided us in the development of an automatic SSC detection algorithm. The SC can be an indicator of the onset of a geomagnetic storm; in this case, it is called an SSC. The geomagnetic records used in this study were 3-s resolution data collected from the Circum-Pan Pacific Magnetometer Network. Using such high-resolution data enabled us to achieve a small detection error and short processing time. In addition to these technical merits, we introduce a new algorithm that automatically detects, for the first time, the SC from high-resolution data (sampled at the rate of 1 sample/3 s), unlike previous studies that focused on determining the SSC times automatically using 1-min data. Ninety-three geomagnetic storms were considered for testing the proposed algorithm; it was found that the average and maximum standard deviation of the errors in the detection times determined by the algorithm were 7 and 18 samples, respectively, of the corresponding manually determined arrival times.

Systematic examination of the geomagnetic storm sudden commencement using multi resolution analysis

Geomagnetic storm sudden commencements (SSC) contain a wealth of information which is useful in many applications. It is important to point out that the SSCs used in this study are sampled at the rate of one sample per second in order get use of such high resolution data. In this paper, two studies are made on the geomagnetic SSC and an SSC onset automatic detection algorithm is introduced. The first study is about finding the relationship between the SSC rise time and its amplitude. Where it is found that there is a positive correlation between the amplitude and the amplitude gradient which is the amplitude divided by rise time. The second study is checking the spectrum of the SSC, starting from its onset until the end of the SSC rise time. This check had proved that the SSC contains both low and high frequency regions. This led us to introduce a new term, namely the SSC variation rate (VR). This VR is defined as the maximum rate of change of the field in the higher-frequency region of the SSC. These two studies were the guide to build an SSC automatic detector of one sample per second data using multi resolution analysis (MRA) of the discrete wavelet transform (DWT). The data set contains 134 SSCs with different VRs that were collected from the Circum-pan Pacific Magnetometer Network (CPMN). It is found that the standard deviation of the detection error is 41s and that the average error is 9s. From the calculated error distribution function, it is found that the detection error is within the range of −1.5 to 3min. The detection process, as will be shown in the article, takes 70s for one station and 3min if the decision is related to the detection(s) of other stations. These results demonstrate the superiority of the proposed algorithm over other algorithms in which the detection error ranges between −8 and 5min and the detection process takes 2–10min. In addition to being faster and more accurate than the other algorithms, the proposed algorithm is the first algorithm that automatically detects the SSC onset times from high-resolution data unlike previous studies that focused on determining the SSC times automatically using one-minute resolution data.

An empirical model of the quiet daily geomagnetic field variation

[1] An empirical model of the quiet daily geomagnetic field variation has been constructed based on geomagnetic data obtained from 21 stations along the 210 Magnetic Meridian of the Circum-pan Pacific Magnetometer Network (CPMN) from 1996 to 2007. Using the least squares fitting method for geomagnetically quiet days (Kp ≤ 2+), the quiet daily geomagnetic field variation at each station was described as a function of solar activity SA, day of year DOY, lunar age LA, and local time LT. After interpolation in latitude, the model can describe solar-activity dependence and seasonal dependence of solar quiet daily variations (S) and lunar quiet daily variations (L). We performed a spherical harmonic analysis (SHA) on these S and L variations to examine average characteristics of the equivalent external current systems. We found three particularly noteworthy results. First, the total current intensity of the S current system is largely controlled by solar activity while its focus position is not significantly affected by solar activity. Second, we found that seasonal variations of the S current intensity exhibit north-south asymmetry; the current intensity of the northern vortex shows a prominent annual variation while the southern vortex shows a clear semi-annual variation as well as annual variation. Thirdly, we found that the total intensity of the L current system changes depending on solar activity and season; seasonal variations of the L current intensity show an enhancement during the December solstice, independent of the level of solar activity.

Possible association between anomalous geomagnetic variations and the Molise Earthquakes at Central Italy during 2002

The Molise region, on 31 October and 1 November 2002, was struck by two earthquakes of moderate magnitudes (Mw = 5.7) at depth between 12 and 24 km. Geomagnetic data from the Circum-pan Pacific Magnetometer Network (CPMN) were analyzed in order to detect any anomalous geomagnetic variations in association with the Molise earthquakes. Our results indicate the presence of long-term anomalous variations in the geomagnetic components at L’Aquila (LAQ) station (near the epicenter), which started about four months before the occurrence of the Molise earthquakes. Moreover, the geomagnetic components recorded at LAQ are found to show no correlation with those at other conjugate stations in the period between June and October 2002. In addition, anomalous ULF signal (Pc 3:10–45 s) started few weeks before the Molise earthquakes and lasted for about one week after the onset of the seismic activity. The observed anomalous variations may be explained as a result of the crustal stress variations and the enhancement of the lithospheric conductivity in the Molise region during the preparation period of the Molise earthquakes.

Reexamination of the Sq‐EEJ relationship based on extended magnetometer networks in the east Asian region

We reexamined the daily Sq‐equatorial electrojet (EEJ) relationship based on these extended magnetometer networks in the east Asian region: (1) the Circum‐pan Pacific Magnetometer Network (CPMN), (2) the International Real‐time Magnetic Observatory Network (INTERMAGNET), and (3) the World Data Center for Geomagnetism, Kyoto (WDC). Daily variations of the geomagnetic field for geomagnetically quiet days (Kp ≤ 2+) from 1996 to 2005 were analyzed. Noontime eastward Sq current intensities were estimated by latitudinally integrating the north‐south component of the Sq field. The corresponding EEJ intensities were estimated from the daily geomagnetic field variations observed at Davao station (dip latitude of −0.84°deg). We discovered that these intensities of daily Sq and EEJ are well correlated on a long‐term basis (r = 0.80). The dependences on the solar activity (as indicated by F10.7) and season (the day number) of Sq and EEJ variations were examined. It was demonstrated that both daily Sq and EEJ intensities are correlated to F10.7 with similar sensitivities. F10.7 is known to show similar variations with solar EUV radiation which causes ionization and heating of the ionosphere. For seasonal dependence, both daily Sq and EEJ intensities show predominant semiannual variations with similar spring‐fall asymmetry. The effect of seasonal changes of the EUV flux into the low‐latitude ionosphere is considered. Our results indicate that the daily values of Sq and EEJ react, in the same manner, to temporal changes of solar ionization and heating of the ionosphere.

Anomalous occurrence features of the preliminary impulse of geomagnetic sudden commencement in the South Atlantic Anomaly region

Occurrence features of the preliminary impulse (PI) of geomagnetic sudden commencement (SC) both in the Pacific Ocean and South Atlantic Anomaly (SAA) regions were investigated using the long‐term magnetic field data obtained from the Circum‐pan Pacific Magnetometer Network (CPMN) and NICT Space Weather Monitoring (NSWM) magnetometer networks. The low‐latitude preliminary reverse impulse (PRI) at Okinawa (OKI: dip latitude = 37.97°) in the Pacific Ocean region appeared in all the magnetic local time (MLT) sectors with the peak occurrence rate of 40% around noon. On the other hand, the PRI occurrence rate at Santa Maria (SMA: dip latitude = −34.35°) near the center of the SAA region showed a significant enhancement in the daytime sector (0800–1600 h, MLT) with the peak value of 80%, which resembles the occurrence feature of the equatorial PRI. Moreover, the PRI amplitude around noon at SMA was about 3.0 times larger than that at OKI. From the calculation of the ionospheric conductivity derived from the IRI‐2007 and NRLMSISE‐00 models, it is shown that the height‐integrated conductivity was more enhanced in the SAA region (SMA), where the ambient magnetic field intensity is weak, compared with that in the Pacific Ocean region (OKI). Therefore, the anomalous increase of the PRI occurrence and amplitude is caused by the significant enhancement of the ionospheric conductivity due to the weakness of the ambient magnetic field intensity in the SAA region.

Equivalent current systems for the annual and semiannual Sq variations observed along the 210°MM CPMN stations

We analyzed ground magnetometer data for the 10 International Quiet Days during 1996–2007. The data were obtained from 19 stations along 210°magnetic meridian (MM) of the Circum‐pan Pacific Magnetometer Network (CPMN) covering both the Northern Hemisphere and Southern Hemisphere. From the daily variations of the geomagnetic field, we deduced the latitude‐local time (LAT‐LT) diagram of the equivalent Sq current system, which can be regarded as the superposition of the following three current systems: Sq0, Sq1, and Sq2. The Sq0, Sq1, and Sq2 current systems are equivalent current systems for the yearly average, annual variation, and semiannual variation of the Sq field, respectively. We have examined temporal and spatial features of these current systems. The principal features are as follows: (1) The total current intensities of the Sq1 and Sq2 current systems are about 35% and 15% of that of the Sq0 current system, respectively. (2) The Sq0 and Sq2 current systems have a dayside vortex in each hemisphere, while the Sq1 current system has a single vortex centered at the equatorial region in the morning sector (∼1000 LT).

Characteristics of counter‐Sq SFE (SFE*) at the dip equator CPMN stations

The solar flare effect (SFE) at dip equatorial latitudes sometimes shows the counter‐Sq variation around local noon. In this paper, we refer to this type of SFE as SFE*. Observations obtained by the Circum‐pan Pacific Magnetometer Network (CPMN) reveal some previously unknown characteristics of SFE*. Some of these features are the following: (1) the counter‐Sq SFE variation is observed in limited longitude (local time) and latitude sectors (i.e., LT ≈ 1030–1300, ∣DipLat.∣ ≲ 1.5°), (2) outside this limited region, the amplitude of SFE(H) and preflare Sq(H) have a linear relationship, and (3) SFE* is observed during the significant depression of the horizontal magnetic field at dip equatorial latitudes, which indicates the presence of westward electric fields whose origin remains to be understood.

MAGDAS for Geospace Environment Monitoring

MAGnetic Data Acquisition System (MAGDAS) of the Circum-pan Pacific Magnetometer Network (CPMN) is introduced. MAGDAS/CPMN measures the ground magnetic field all around the world and sends the measured data to Space Environment Research Center (SERC), Fukuoka, Japan, via Internet, telephone line or satellite phone line. As examples of the phenomena observed by MAGDAS/CPMN, we present observations of the equatorial electrojet, Pi 2 waves near the dip equator, and SC-associated ionospheric electric field; Pi 2 is a transient ULF wave taking place at the beginning of a phenomenon called substorm, and SC (sudden commencement) is a phenomenon taking place as an interplanetary shock arrives at the Earth. We also compare ground-based estimations of the space plasma density with simultaneous direct observations by spacecraft.

Equatorial ionization anomaly of the total electron content and equatorial electrojet of ground-based geomagnetic field strength

Measurements from ground-based receiver chains of the global positioning system (GPS) and magnetometers of the Circum-pan Pacific Magnetometer Network (CPMN) in the west Pacific region during 1999–2003 are examined. The ionospheric total electron content (TEC) derived from the GPS receivers is used to observe the strength, location, and occurrence time of the equatorial ionization anomaly (EIA) crests, which resulted from the equatorial plasma E× B drift fountain. The magnetic field strength of CPMN is employed to monitor the equatorial electrojet (EEJ), and to further estimate the effectiveness of the E× B drift to the EIA crests. Results show that the strength and location of the EIA crests are proportional to the EEJ strength.

Simultaneous observations of the plasma density on the same field line by the CPMN ground magnetometers and the Cluster satellites

By applying the cross-phase method and the amplitude-ratio method to magnetic field data obtained from two ground stations located close to each other, we can determine the frequency of the field line resonance (FLR), or the field line eigenfrequency, for the field line running through the midpoint of the two stations. From thus identified FLR frequency we can estimate the equatorial plasma mass density ( ρ ) by using the T05s magnetospheric field model [Tsyganenko, N.A., Sitnov, M.I. Modeling the dynamics of the inner magnetosphere during strong geomagnetic storms, J. Geophys. Res. 110, A03208, 2005] and the equation of Singer et al. [Singer, H.J., Southwood, D.J., Walker, R.J., Kivelson, M.G. Alfven wave resonances in a realistic magnetospheric magnetic field geometry, J. Geophys. Res. 86 (A6) 4589–4596, 1981]. In this study we compare ρ estimated from magnetometer data at two stations in the CPMN (Circum-pan Pacific Magnetometer Network) chain, Tixie (TIK, geographic coordinates: 71.59°N, 128.78°E, L = 6.05 ) and Chokurdakh (CHD, geographic coordinates: 70.62°N, 147.89°E, L = 5.61 ), with the plasma electron number density ( Ne) observed by the WHISPER (Waves of HIgh frequency Sounder for Probing the Electron density by Relaxation) instrument onboard the Cluster satellites. For the interval of January 1, 2001–December 31, 2005, we have identified 19 events in which the Cluster spacecraft were located on the field line running through the midpoint of TIK and CHD when they observed FLR, and statistically compared the simultaneously observed ρ and Ne, although the number of events are limited (19). In 15 out of the 19 events the ratio of ρ to Ne falls into a realistic range. It is also suggested that the contribution of heavy ions tends to increase when the magnetosphere is disturbed.

A new ULF wave analysis for Seismo-Electromagnetics using CPMN/MAGDAS data

The Space Environment Research Center of Kyushu University has obtained geomagnetic data in the Circum-pan Pacific Magnetometer Network (CPMN) region for over 10 years, and has recently deployed a new real-time Magnetic Data Acquisition System (MAGDAS) in the CPMN region and an FM-CW radar network along the 210° magnetic meridian (MM) for space weather research and applications. This project intends to get the MAGDAS network fully operational and provide data for studies on space and lithosphere weather. In connection with this project, we propose a new ultra-low frequency (ULF) wave analysis method to study ULF anomalies associated with large earthquakes using magnetic data. From a case study of the 1999/05/12 Kushiro earthquake with magnitude M = 6.4, we found a peculiar increase of H-component power ratio A R/ A M of Pc 3 magnetic pulsations a few weeks before the earthquake, where A R is the power obtained at Rikubetsu station ( r = 61 km) near the epicenter and A M is the power obtained at a remote reference station, Moshiri ( r = 205 km). It is also found that the H-component power ratio A D/ A Y of Pc 3 increased three times just a few weeks before the earthquake and after one week decreased to the normal level, where A D is one-day power at Rikubetsu station and A Y is the one-year-average power.

Horizontal amplitude and phase structure of low-latitude Pc 3 pulsations around the dawn terminator

[1] The horizontal spatial structure of Pc 3 pulsations observed at low geomagnetic latitude (22–46°) around dawn is studied statistically using data acquired by the Circum-pan Pacific Magnetometer Network (CPMN). It is found that while the phase of the H component of low-latitude Pc 3 pulsations remains largely unchanged with the passing of dawn, the D component undergoes a phase shift of ca. 180°. This phase variation across dawn is related to the abrupt change in the major axis orientation of polarization ellipses observed in previous studies. Both the H and D components have higher amplitude after dawn than before dawn. This horizontal amplitude and phase structure is well explained by the response of a nonuniform ionosphere around dawn to incident Alfven waves, where the secondary electric field caused by charge accumulation at the dawn terminator plays an important role in deformation of the current system. Enhancement of the D/H ratio is also observed just after dawn at very low latitudes (22°). As Alfven waves are not excited efficiently at very low geomagnetic latitudes, including the magnetic equator, the observed horizontal structure in such regions may be due to a large-scale current system originating at higher latitudes.

Simultaneous identification of a plasmaspheric plume by a ground magnetometer pair and IMAGE Extreme Ultraviolet Imager

We have compared two quantities which were simultaneously observed by two different instruments at the same point of the plasmaspheric plume. One quantity is the field‐line eigenfrequency, which was obtained by applying the dual‐station H‐component power ratio method to geomagnetic data obtained from two ground magnetometers (at Tixie and Chokurdakh) of the Circum‐pan Pacific Magnetometer Network (CPMN). The other is the He+ column abundance obtained by the IMAGE satellite Extreme Ultraviolet Imager (IMAGE/EUV). We used the EUV He+ column abundance data mapped to the equatorial footpoint of the field‐line whose eigenfrequency we obtained from the ground data. The mapped EUV He+ column abundance is roughly proportional to the equatorial density of He+. The result of the IMAGE/EUV analysis showed an increase‐then‐decrease pattern of the He+ column abundance. On the other hand, as a result of analyzing the simultaneously observed ground magnetometer data, we found that the eigenfrequency showed a coherent decrease‐then‐increase pattern. Since this pattern takes place if the equatorial plasma density along the field line increased and then decreased, these two results are qualitatively consistent. In addition, the H‐power ratio showed an offset when either Tixie or Chokurdakh (these stations are longitudinally separated) stayed inside the plume. This feature can be explained if the overall ULF wave power was weaker in the plume than in the surrounding trough. With the above findings, this paper is the first to identify a plume from both the spacecraft image and the ground magnetometer ULF waves.

On the nature of response of dayside equatorial geomagnetic H-field to sudden magnetospheric compressions

A step-like increase in the solar wind ram pressure causes a sudden compression of the magnetosphere which manifests as a sudden commencement (SC) in the geomagnetic field. SC manifests in two basic forms in the geomagnetic H-field of the dayside dip equatorial region, namely, as a positive impulse termed SC(+), and as a positive impulse preceded by a sharp negative impulse termed, SC(−, +) or SC *. Unlike at high latitudes, the factor(s) that determine this bi-modal response of the equatorial geomagnetic H-field to sudden magnetospheric compressions are not known. As an exploratory step in identifying the causative factor(s), we have performed a statistical study of the characteristics of the daytime (06-18 IST) SCs recorded at the equatorial station, Kodaikanal (10.25N, 77.5E, dipole latitude 0.6N) and the low latitude station, Alibag (18.6N, 72.9E, dipole latitude 9.5N) over the period 1957–2002. A total of 304 SCs have been analyzed out of which 99 (32.6 per cent) were of SC * type. We find that the average value of the amplitude of the positive main impulse (MI) in H-component of SC * is higher than that of the conventional SC(+). This difference in the MI amplitude is statistically significant and persists even when the analysis is restricted to the interval of SC * occurrence, namely, 0730–1730 IST. Such a behavior is not seen in the amplitude of the MI at Alibag, away from the influence of the equatorial electrojet. It is found for the first time that a linear relationship exists between the amplitudes of the preliminary reverse impulse (PRI) and MI in SC * events. Our study of the H-field response at dayside dip equatorial stations of the Circum-pan Pacific Magnetometer Network (CPMN) to sudden magnetospheric compressions under different IMF orientation (northward and southward), showed that the impact of an impulse in solar wind dynamic pressure under southward IMF is associated with SC * in both the events considered. On the other hand, under northward IMF the dynamic pressure increase consistently led to SC(+) in the two events studied. The statistical and case study results imply that, when compared to SC(+), the contribution of ionospheric currents of polar origin gain prominence when SC * is excited at dayside dip equator, and the orientation of IMF Bz may be one of the (if not the only one) deterministic factors underlying the bi-modal response of the dayside equatorial H-field to a sudden increase in solar wind dynamic pressure.