QUARTZ MAGNETIC VARIATION STATIONS IZMIRAN AT POLAR OBSERVATORIES AND OBSERVATION POINTS: FROM ANALOG TO DIGITAL INSTRUMENTS

The paper presents a brief overview of magnetometric devices - quartz analog and digital magnetic variation stations, which were created by IZMIRAN employees for almost 50 years of time to conduct scientific geomagnetic research in the Arctic and Antarctica.

Magnetic variation in construction steels under tensile stress. Empirical research with Helmholtz coils

Steel is responsible for providing resistance to flexotraction to reinforced concrete structures. Steel is responsible for providing reinforced concrete structures with a flexural strength. For this reason, it is important to study its behaviour under different tensile states. This study used measuring equipment that was able to determine variations in magnetic properties of B500-SD steel bars during standard tensile tests. The magnetic field generated by a Helmholtz coil was collected through a secondary circuit. This enables the induced electromotive force to relate with the steel deflection stages when subjected to the tests. Moreover, it was possible to determine the variation of magnetic permeability when submitting 12mm and 16mm diameter bars to different tensile states. This method could prove extremely useful in determining the tensile state of ribbed steel bars that are embedded into the concrete structure.

Evaluation of Aurora Activity Obtained from Abisko and Kiruna Ground Based Observation

<p>Available space weather forecasts mainly use data from the Sun and upstream interplanetary monitoring, to provide the early warning. Although the accuracy is improving, it cannot provide onset timing and actual strength of the substorm and its propagations better than 1 hour. A higher-accuracy forecast requires monitoring of the ionosphere (e.g., aurora and geomagnetic field). In this sense, it is also necessary to develop a value-based nowcast based on such monitoring. In EGU 2018, Yamauchi et al. has proposed simple index showing aurora and geomagnetic conditions using 1-minute resolution values from Kiruna. This study improved in the following directions:</p><p>(1) We used 1-sec resolution data and optimized the indices above: By using 1-sec values, the products representing variation (standard deviation and peak-to-peak variation) can be obtained every minute and improved, whereas combination of <em>∑L</em><sup>3</sup> (or ∑<em>L*</em>exp(<em>L</em>)) and area of aurora found to be the best in representing the aurora activity, where <em>L</em> is luminosity of each pixel defined by HLS color code. Using these values, we confirmed that the intensity of the aurora was different for the same magnetic variation between before and after the strongest aurora (substorm onset). Therefore, it is necessary to add a condition of "increasing trend" of both aurora and magnetic variation from the viewpoint of forecasting.</p><p>(2) We compared the results from two different places (Abisko and Kiruna in Sweden) that are 89 km apart in linear distance. Our Abisko camera system (DASC, Digital All Sky Camera) is in operation since March 2014. When the aurora was observed at both sites, the shapes of the aurora at both sites are sometimes quite different at the same time. In addition, the timing of the brightest aurora (<em>∑L</em><sup>3</sup> or <em>∑L*</em>exp(<em>L</em>) is maximum) was different between both sites. These results confirm that the aurora had a three-dimensional structure, which has been known for many years.</p><p>(3) Using superposed epoch analysis, we also took statistics of last 10 minutes before the largest aurora (in the index mentioned above) occurred.</p>

Seasonal dependence of semidiurnal equatorial magnetic variation during quiet and disturbed periods

The analysis of 20-year long-term semidiurnal lunar tidal variations gave the evidence that the semidiurnal variations are completely different between the magnetic quiet and disturbed periods. This is the first time that the seasonal dependence of disturbance-time semidiurnal variation has been provided from the analysis of the EE-index. We found the Kp dependence of semidiurnal variation: For full and new moon phase, counter troughs are amplified during disturbance time, possibly related to disturbance dynamo. For all moon phase, there are positive enhancements in dawn and strong depressions after sunset, resulting from the penetration of polar electric filed. For Seasonal dependence, semidiurnal variations are divided to three seasonal groups, and characterized as deep trough, enhanced crest and weak structure for D-solstice, Equinoxes and J-solstice, respectively. There is no significant longitudinal difference between Ancon and Davao, except for the amplitude of semidiurnal variations. The deep troughs occur during D-solstice and the enhanced crests during Equinoxes, at both Ancon and Davao.

Adventures with instruments: science and seafaring in the precarious career of Christopher Middleton

Christopher Middleton (d. 1770) was a sea captain, first with the Hudson's Bay Company, then in the Royal Navy, who was awarded the Royal Society's Copley Medal in 1742. His early work on magnetic variation in northern latitudes was encouraged by Edmond Halley, as he published a series of tables of variation in the Philosophical Transactions . These tables illustrate Middleton's transition from the priorities characteristic of the seaman's interest in variation to the wider, natural philosophical agenda of the Society. They illustrate also his enthusiasm for novel instrumentation, in particular altitude instruments for use at sea, such as Hadley's quadrant. Middleton was persuaded by Arthur Dobbs to resign from the Hudson's Bay Company and accept a commission in the Royal Navy so as to command an expedition to search for a Northwest Passage to the East Indies from Hudson's Bay. It was his report on this voyage that won him the Copley Medal but which also led to a bitter and, for Middleton, ruinous public dispute with Dobbs. Middleton emerges as an outstanding seaman and a worthy, if relatively unknown, medallist.

ANALISIS KEJADIAN BADAI MAGNETIK BERDASARKAN DATA VARIASI HARIAN MAGNETIK DI KOTA KUPANG

ABSTRAK Telah dilakukan penelitian analisis kejadian badai magnetik di Kota Kupang bulan Oktober 2014 sampai bulan September 2016. Penelitian ini bertujuan untuk menentukan karateristik kejadian badai magnetik serta menentukan periode kemunculan badai magnetik di Kota Kupang. Pengolahan data dengan menggunakan Software Microsoft Excel untuk dibuat grafik data komponen magnet bumi terhadap waktu dan Software Matlab 2011 untuk penentuan periodesitas kejadian badai magnetik menggunakan transformasi fourier cepat (FFT). Berdasarkan hasil pengolahan data, karateristik kejadian badai magnetik yang terdapat di daerah penelitian untuk bulan Oktober 2014 sampai September 2016 adalah untuk tingkat aktivitas gangguan magnetik maksimum ditandai dengan nilai K indeks=8, A indeks=54.875 dan penurunan nilai Dst= -121 nT, sehingga dikategorikan badai menengah dan tingkat aktivitas gangguan magnetik minimum ditandai dengan nilai K indeks=3, A indeks=11.5 serta penurunan nilai Dst = -17 nT, sehingga dikategorikan relatif tenang. Periode kemunculan aktivitas magnetik bulan Oktober 2014-September 2016 adalah berada dalam periode satu harian sampai sepuluh harian. Kata kunci : Variasi harian magnetik, badai magnetik, periodesitas, K indeks, A indeks. ABSTRACT The research about analysis of magnetic storm events in Kupang City from October 2014 to September 2016 has been done. The purpose of this study is to determine the characteristic of storm events and the period of emergence magnetic storm from Kupang City. The data used is the daily magnetic variation data obtained from Meteorogical Climatological and Geophysical Agency in Kupang City. The data processing using by Microsoft Excel software to create graph data of the earth magnetic components against time and Matlab 2011 sofware to determining the periodicity of magnetic storm events using Fast Fourier Transform (FFT). From the results of data processing, the characteristic of magnetic storm events in the study area from October 2014 to September 2016 were for the maximum magnetic interference activity level occurring on june 22th, 2015 due to burst of CME marked by the value of K index = 8, A index = 54.875 and degradation value of DST = -121 nT, so category middle storm and minimum magnetic interference activity level occurred on February 10th, 2015 due to burst of CME and flare marked with value K index = 3, A index =11.5, and decreasing value of DST =-17 nT, thus categorized relatively quietly. The period of occurrence magnetic activity from October 2014 to September 2016 is within a period of one daily to ten daily. Keywords : Daily magnetic variation, magnetic storm, K index, A index.

Compasses and sinking ships: Mrs Janet Taylor’s contribution in the compass adjusting controversy of mid-nineteenth-century England

The mid-nineteenth century was a highpoint of empire building, and reliable navigation across the oceans was crucial. While the effects of magnetic variation and deviation on compasses were well known by 1800, iron ships brought with them an even bigger challenge. The nautical world divided between ‘applied’ and ‘theoretical’ approaches to addressing the ‘compass problem’. This article focuses on the role of Janet Taylor, who lived and worked in the heart of this community, as a writer, teacher, inventor, chart-seller and compass adjuster, as a follower of the system of compass adjustment advocated by the Astronomer Royal, Professor George Airy. Janet Taylor’s achievements in the compass adjusting field and her interactions with the Astronomer Royal are explored, adding another insight into Mrs Taylor’s distinctive story.