Analisis Big Data Geomagnetik Dengan Metode Diferensiasi Sebagai Prekursor Gempa Lombok Tahun 2018

Lombok is an area with the highest geomagnetic anomaly in Indonesia (Zubaidah et al., 2014). From the end of July to the end of August 2018, Lombok experienced a series of fairly large earthquakes. Identification of geomagnetic signals, especially in the Ultra Low Frequency (ULF) spectrum, can be used as earthquake precursors (Saroso, 2010). Intermagnet IAGA (International Aeronomy Geomagnetic Association) is a network of international geomagnetic observatory stations that have large world geomagnetic data. Big data analysis is very important because very large information is needed in disaster mitigation. This study uses geomagnetic data per second for 24 hours from 28 August to 30 November 2018 taken from Kakadu (KDU) Australia and Nurul Bayan Station (NRB) Lombok. The analytical method used is Differentiation by calculating the F value (total magnetic field) for KDU and NRB, then look for the difference and analyze the pattern. The results found that there was an anomaly phenomenon of the Earth's magnetic field in Nurul Bayan Lombok which was detected for 17 days during October 2018.

Production of definitive data from Indonesian geomagnetic observatories

Measurement of the geomagnetic field in Indonesia is undertaken by the Meteorological, Climatological, and Geophysical Agency (BMKG). Routine activities at each observatory include the determination of declination, inclination, and total field using absolute and variation measurements. The oldest observatory is Tangerang (TNG), started in 1957, followed by Tuntungan (TUN) in 1980, Tondano (TND) in 1990, Pelabuhan Ratu (PLR) and Kupang (KPG) in 2000, and Jayapura (JAY) in 2012. One of the main obligations of a geomagnetic observatory is to produce final versions of data, released as definitive data, for each year and make them widely available both for scientific and non-scientific purposes, for example to the World Data Centre of Geomagnetism (WDC-G). Unfortunately, some Indonesian geomagnetic observatories do not share their data with the WDC-G and often have difficulty in producing definitive data. In addition, some more basic problems still exist, such as low-quality data due to anthropogenic or instrumental noise, a lack of data-processing knowledge, and limited observer training. In this study, we report on the production of definitive data from Indonesian observatories, and some recommendations are provided about how to improve the data quality. These methods and approaches are applicable to other institutes seeking to enhance their data quality and scientific utility, for example in main field modelling or space weather monitoring. The definitive data from the years 2010 to 2018 are now available in the WDC-G.

Production of Definitive Data from Indonesian Geomagnetic Observatories

Measurement of the geomagnetic field in Indonesia is undertaken by the Meteorology, Climatology and Geophysics Agency (BMKG). Routine activities at each observatory include the determination of declination, inclination and total field using absolute and variation measurements. The oldest observatory is Tangerang (TNG), started in 1964, followed by Tuntungan (TUN) in 1980, Tondano (TND) in 1990, Pelabuhan Ratu (PLR) and Kupang (KPG) in 2000 and Jayapura (JAY) in 2012. One of the main obligations of a geomagnetic observatory is to produce final measurements, released as definitive data, for each year and make them widely available both for scientific and non-scientific purposes, for example to the World Data Centre of Geomagnetism (WDC-G). Unfortunately, some Indonesian geomagnetic observatories do not share their data to the WDC and often have difficulty in producing definitive data. In addition, some more basic problems still exist such as low quality data due to man-made or instrumental noise, a lack of data processing knowledge, and limited observer training. In this study, we report on the production of definitive data from Indonesian observatories and some recommendations are provided about how to improve the data quality. These methods and approaches are applicable to other institutes seeking to enhance their data quality and scientific utility for example in main field modelling or space weather monitoring.

Measurement of the difference in the geomagnetic induction between the magnetometer pillars of the geomagnetic observatory of the Ukrainian Antarctic Akademik Vernadsky station

The article describes the features of measurements of spatial inhomogeneities of the geomagnetic field between the pillars of magnetometers in the measuring pavilion, which were carried out at the geomagnetic observatory of the Ukrainian Antarctic Akademik Vernadsky station in 2015. Some preliminary results of these measurements are also given. The concept of the timescaled value of the geomagnetic field induction is introduced, which is convenient for compensating for time changes of the real geomagnetic induction and bringing it to one reference level of induction. The differences in geomagnetic induction between pillars are obtained as the differences in time-scaled values of the geomagnetic induction on the pillars. The technique allows comparing long-term series of measurements of field inhomogeneities at important points in space. The main objectives are to increase the accuracy of measurements of local inhomogeneities of the geomagnetic field in the measuring pavilion of the geomagnetic observatory of the Ukrainian Antarctic Akademik Vernadsky station and to determine the differences in the geomagnetic induction between the pillars on which the magnetometer sensors are installed. Obtaining numerical values of the differences in the geomagnetic induction between the pillars as objective criteria needed to assess the accuracy of the data in the final processing of geomagnetic observatory data. The method of comparison of two series of data is used: one obtained by the scalar magnetometer installed in the observatory as a mandatory stationary device, and the other obtained during measurements with a mobile magnetometer at the desired points in space. Compensation of temporal changes of the geomagnetic field by time-scaling the measurement readings of the mobile magnetometer relative to one reference value and thus, bringing them to one selected and fixed time epoch. Special geometric scheme of mobile measurements in the space around the pillars with magnetometer sensors or at important points in space. A rough estimate of method errors. Based on the analysis of the obtained data, the efficiency of the method and its acceptable potential accuracy were confirmed. We obtained approximate numerical values of the differences in the geomagnetic field induction between the pillars on which the magnetometer sensors are installed. Further increase in the accuracy of determining these differences is possible using modern devices of high accuracy and GPS-synchronization of mobile measurements.

ANALYSIS OF THE MAGNETIC STORMS CATALOG FOR MONITORING RADIO SOURCE FLUXE DATA WITH THE URAN-4 RADIO TELESCOPE IN THE ODESA MAGNETIC ANOMALY ZONE

Purpose: Compilation of a digital catalog of magnetic storms in the Odesa magnetic anomaly zone in order to find the reasons for possible changes in the radiation fluxes of cosmic radio sources, according to observations at the URAN-4 radio telescope. Design/methodology/approach: Since 1987 until now, the radio flux of powerful galactic and extragalactic radio sources has been monitored at the URAN-4 radio telescope of the Odesa Observatory of the Institute of Radio Astronomy of the National Academy of Sciences of Ukraine. The monitoring program includes radio galaxies 3C274, 3C405 and supernova remnants 3C144, 3C461. Changes in the radio source flux level are determined by the ionosphere state due to the changes in space weather. At the “Odesa” geomagnetic observatory of the Institute of Geophysics of the National Academy of Sciences of Ukraine, the geomagnetic field measurements have been made since 1948. Simultaneously, the measurements of three elements of the geomagnetic field: horizontal component (H), vertical component (Z) and inclination (D), have been recorded. Findings: Using the “Odesa” geomagnetic observatory data, the digital catalog of magnetic storms was compiled for the measuring period of the powerful space radio source fluxes obtained with the URAN-4 radio telescope. For the magnetic storms monitored during the periods of 1987–1995 and 2000–2009, the date and time are shown for the beginning and the end of the magnetic storm, the magnetic storm duration, the amplitude of the three magnetic field elements, being H, Z, and D, and the magnetic storm type characteristic.The “Odesa” geomagnetic observatory is located near the magnetic anomaly zone. To find the distinctions in manifestations of the geomagnetic activity arisen owing to the magnetic anomaly existence, the geomagnetic disturbances recorded at the “Odesa” and “Moscow” (IZMIRAN, Russia) observatories were compared. It was shown that the total annual duration of the magnetic storms was longer in Odesa than in Moscow. This demonstrates some special role of the magnetic anomaly in the development of geomagnetic disturbances. Conclusions: The digital catalog of magnetic storms in the Odesa magnetic anomaly zone was compiled for the 1987–1995 and 2000–2009 periods. It is also planned to terminate working over the complete catalog of magnetic storms recorded at the “Odesa” observatory for the entire continuous period of monitoring space radio sources at the URAN-4 radio telescope in order to find the manifestations of geomagnetic disturbances impact upon the ionosphere state and changes of intensity in cosmic radio source fluxes. These studies are supplemented by the comparative analysis of the “Odesa” observatory geomagnetic data and the data from some other geomagnetic observatories. Key words: solar activity; monitoring variability of radio sources; magnetic storms; catalog of magnetic storms; magnetic anomaly