A Method for Recognition of Sudden Commencements of Geomagnetic Storms Using Digital Differentiating Filters

This article describes a method for recognizing sudden commencement events using digital differentiating filters. This method is applied to INTERMAGNET observatory data. Maximum amplitude derivatives for the magnetic components (X, Y, Z) and the total intensity (F) of the geomagnetic field are introduced, and the decision-making rule is formulated. The authors developed a procedure for selecting optimal digital differentiating filters. Estimates of probabilities of correct and false recognition of sudden commencements were obtained. The calculations of the probabilistic characteristics have confirmed the effectiveness of the method.

Early history of sudden commencement investigation and some newly discovered historical facts

The history of the research on the SC (sudden commencement) of magnetic storms before World War II is studied in this paper. Since geomagnetic research activities before World War II are still not yet fully known, this paper aims to reveal some historical facts related to SC investigation at that time. The first conclusion of this paper is the possible first discoverer of the simultaneity of SC at distant locations. We show that a Portuguese scientist had already pointed it out 16 years earlier than believed. The second conclusion is the role and activities of Aikitu Tanakadate as the reporter of the SC investigation committee of STME (Section of Terrestrial Magnetism and Electricity) and IATME (International Association of Terrestrial Magnetism and Electricity) in the IGGU (International Geodetic and Geophysical Union) or IUGG (International Union of Geodesy and Geophysics). Very little was known about his activities as the reporter of this committee. Our investigation at the Tanakadate Aikitu Memorial Science Museum disclosed how he acted and what he thought of SC, based on his frequent letters to and from other scientists. The third conclusion concerns SC research carried out by Japanese scientists during the period of the Second International Polar Year (1932–1933). Not only Tanakadate but also many other Japanese scientists participated in SC research during this international project. This formed a traditional basis of SC investigation in Japan, prompting a number of Japanese scientists to study SC after World War II.

Pulmonary thromboembolism: A momentous event in a case of polytrauma

Pulmonary thromboembolism (PTE) is one of the momentous events in a case of polytrauma. In majority cases because of sudden commencement, medicolegal autopsy shows insufficient macroscopic confirmation even though thrombo-embolism is the cause of death. During a medicolegal autopsy, the autopsy surgeon, firstly need to differentiate embolus and post mortem clot by gross examination. Histopathological examination (HPE) not only helps to establish emboli but also illuminates associated systemic changes in other organs as well. Most importantly, the correlation of autopsy findings and HPE findings with the clinical events reflected in medical records helps to scientifically explain the series of events during hospitalization. The same data is also useful in better monitoring and management of polytrauma cases in the future.

Penetration of the electric fields of the geomagnetic sudden commencement over the globe as observed with the HF Doppler sounders and magnetometers

Using the HF Doppler sounders at middle and low latitudes (Prague, Czech Republic; Tucuman, Argentina; Zhongli, Republic of China, and Sugadaira, Japan), we observed the electric fields of the geomagnetic sudden commencement (SC) propagating near-instantaneously (within 10 s) over the globe. We found that the electric fields of the preliminary impulse (PI) and main impulse (MI) of the SC are in opposite direction to each other and that the PI and MI electric fields are directed from the dusk to dawn and dawn to dusk, respectively, manifesting the nature of the curl-free potential electric field. We further found that the onset and peak of the PI electric field are simultaneous on the day and nightsides (0545, 1250, 1345 MLT) within the resolution of 10 s. With the magnetometer data, we confirmed the near-instantaneous development of the ionospheric currents from high latitudes to the equator and estimated the location of the field-aligned currents that supply the ionospheric currents. The global simultaneity of the electric and magnetic fields does not require the contribution of the magnetohydrodynamic waves in the magnetosphere nor in the F-region ionosphere. The global simultaneity and day–night asymmetry of the electric fields are explained with the ionospheric electric potentials transmitted at the speed of light by the TM0 mode waves in the Earth-ionosphere waveguide.

СВЯЗЬ НАПРАВЛЕНИЯ ПРИХОДА ФРОНТА МЕЖПЛАНЕТНОЙ УДАРНОЙ ВОЛНЫ СО ВРЕМЕНЕМ SC ПО АНАЛИЗУ ОТДЕЛЬНЫХ КВМ-СОБЫТИЙ

При взаимодействии межпланетных корональных выбросов массы (КВМ), сопровождающиеся ударными волнами, с земной магнитосферой в магнитном поле Земли могут быть зарегистрированы скачки разной интенсивности, которые в некоторых случаях могут инициировать развитие магнитных бурь, представляя собой ее внезапное начало (Storm Sudden Commencement - SSC). В работе представлен первые результаты оценки зависимости времени появления SSC как функции широты/долготы и мирового времени, с целью дальнейшего исследования связи направления прихода фронта ударной волны со временем появления SSC. Для анализа были выбраны два КВМ с источниками формирования в Северном (21.06.2015, 02:36 UT) и Южном (14.07.2017, 01:25 UT) полушарии Солнца. При подходе к Земле они вызвали SSC 22.06.2015 в 18:33 UT и 16.07.2017 в 05:59 UT с последовавшими за ними магнитными бурями. Время старта SSC определялась по секундным данным, доступным в сети INTERMAGNET (около 40 обсерваторий северного и 20 обсерваторий южного полушарий). Для этих событий выполнена оценка появления SSC как функция геомагнитной широты и долготы от всемирного времени. Показано, что с приходом КВМ к Земле старт SSC на наземных магнитных обсерваториях, расположенных на широтах, от высоких до экваториальных, не является одновременным - время старта SSC на разных широтах отличаются на десятки секунд. Кроме этого, в рассмотренных событиях SSC сначала регистрируется на обсерваториях полушария Земли, освященного Солнцем, и, в среднем, появляется раньше в нижних широтах, чем в высоких.