Solar-Terrestrial Physics Solar-Terrestrial Physics Солнечно-земная физика / Solnechno-Zemnaya Fizika / Solar-Terrestrial Physics 2712-9640 13899 10.12737/22606 Результаты исследований Results of current research Результаты исследований Features of formation of small-scale wave disturbances during a sudden magnetospheric compression Особенности формирования мелкомасштабных волновых возмущений во время резкого сжатия магнитосферы https://orcid.org/0000-0003-1206-8099 Моисеев Алексей Владимирович Moiseev Aleksey Vladimirovich moiseev@ikfia.ysn.ru

кандидат физико-математических наук;

candidate of physical and mathematical sciences;

 Баишев Дмитрий Гаврильевич Baishev Dmitry Gavrilyevich baishev@ikfia.ysn.ru

кандидат физико-математических наук;

candidate of physical and mathematical sciences;

 Мишин Владимир Виленович Mishin Vladimir Vilenovich vladm@iszf.irk.ru

доктор физико-математических наук;

doctor of physical and mathematical sciences;

 Уозуми Т. Uozumi T. Йошикава Акимаса Yoshikawa Akimasa Ду А. Du A. Институт космофизических исследований и аэрономии им. Ю.Г. Шафера СО РАН – обособленное подразделение Федерального исследовательского центра «Якутский научный центр СО РАН». Россия Институт космофизических исследований и аэрономии им. Ю.Г. Шафера СО РАН – обособленное подразделение Федерального исследовательского центра «Якутский научный центр СО РАН». Russian Federation Институт космофизических исследований и аэрономии им. Ю.Г. Шафера СО РАН Якутск Россия Yu.G. Shafer Institute of Cosmophysical Research and Aeronomy SB RAS Yakutsk Russian Federation Институт солнечно-земной физики СО РАН Иркутск Россия Institute of Solar Terrestrial Physics SB RAS Irkutsk Russian Federation Международный центр по науке и образованию в области космической погоды, Университет Кюсю Фукуока Япония International Center for Space Weather Science and Education, Kyushu University Fukuoka Japan Международный центр по науке и образованию в области космической погоды, Университет Кюсю Фукуока Япония International Center for Space Weather Science and Education, Kyushu University Fukuoka Japan Институт геологии и геофизики КАН Пекин Китайская Республика Institute of Geology and Geophysics CAS Beijing Taiwan 15 11 2016 15 11 2016 3 2 36 44 https://naukaru.ru/en/nauka/article/13899/view

По данным наземных и спутниковых наблюдений рассматриваются квазипериодические изменения геомагнитного поля и параметров плазмы в диапазоне Pc 5 пульсаций, последовавшие сразу после взаимодействия межпланетной ударной волны (МУВ) с земной магнитосферой в событии 24.04.2009 в 00:53 UT. Пульсации были локализованы на широтах 66–74° в полуденном (11 MLT) и вечернем (20 MLT) секторах. Анализ годографов изменений геомагнитного поля как по спутниковым, так и наземным наблюдениям показал наличие вихревых возмущений. В данном событии фронт МУВ в межпланетной среде и фронт волны сжатия в магнитосфере имели наклон в плоскости ZGSM=0, угол наклона составлял 14° в межпланетной среде и 34° в магнитосфере. Положение вихревых возмущений в магнитосфере на разном радиальном расстоянии: X~5.5 Re в полуденном и X~–6.3÷–7.3 Re в вечернем секторе, согласуется с наклоном фронта. По спутниковым наблюдениям максимальная интенсивность волновых возмущений в обоих секторах регистрировалась в тороидальной компоненте, что соответствовало резонансному механизму возбуждения этих возмущений. Анализ распределения скоростей течения плазмы и распространения фронта волны сжатия в магнитосфере показал, что вихревые возмущения наблюдались в областях, где скорости течения плазмы и распространения фронта значительно различались по величине.

Quasi-periodic changes of the geomagnetic field and plasma parameters in the range of Pc 5 pulsations, which occurred immediately after the interaction of interplanetary shock (IPS) with Earth’s magnetosphere in the event of April 24, 2009 at 00:53 UT are examined using ground and satellite observations. The pulsations were localized at latitudes 66–74° in the noon (11 MLT) and evening (20 MLT) sectors. The analysis of hodographs of the geomagnetic field changes both from satellite and ground observations has shown the presence of vortical disturbances. In this event, both the IPS front in the interplanetary medium and the compression wave front in the magnetosphere had a slope in the ZGSM=0 plane; the inclination angle was 14° in the interplanetary medium and 34° in the magnetosphere. The location of the vortical disturbances in the magnetosphere at different radial distances, i.e. X~5.5 Re in the noon sector and X ~–6.3 ÷–7.3 Re in the evening sector, is in agreement with the front inclination. As inferred from satellite observations, the maximum intensity of wave disturbances in both the sectors was registered in the toroidal component of the magnetic field. This suggests the resonant mechanism of excitation of these disturbances. The analysis of distribution of velocities of plasma flow and compression wave front propagation in the magnetosphere’s equatorial plane has revealed that the vortical disturbances occurred in regions where these velocities were noticeably different in magnitude.

 межпланетная ударная волна внезапный геомагнитный импульс геомагнитные пульсации сдвиговое течение interplanetary shock sudden geomagnetic impulse geomagnetic pulsations shear flow

1. INTRODUCTIONSudden geomagnetic impulses (SI) caused by the in-teraction of the solar wind (SW) with Earth’s magneto-sphere, are often accompanied by generation of geomagnetic pulsations in a range 1–1000 mHz, designated as Psi pulsations [Saito and Matsushita, 1967].Among these pulsations are global magnetospheric oscillations observed in wide latitude and longitude ranges [Samsonov, 2013], and pulsations observed locally due to field line resonances [Nishida, 1980]. Ac-cording to the empirical model [Araki, 1994], global current systems appear during SI. They include magnetospheric (field-aligned) and ionospheric currents. Alfvén waves and corresponding field-aligned currents are assumed to be generated at Alfvén velocity gradients.Numerical calculations predict the formation of current systems in the ionosphere and their associated plasma flow vortex disturbances in the magnetosphere. Plasma vortices appear at field line apexes corresponding to the field-aligned currents in the magnetosphere due to the accelerated flows in the equatorial plane in the outer magnetosphere [Slinker et al., 1999].Shi et al. [2014] have studied the generation of Psi pulsations localized in the night plasma sheet. Relying on spatio-temporal characteristics of pulsations and model calculations, the authors suggest that the Psi pulsations occur due to the interaction of a vortex with a resonant field line rather than due to the sharp compres-sion of the magnetosphere by SW.We analyze Psi pulsations in the Pc5 range localized in the pre-noon and evening sectors during the April 24, 2009 event. Using synchronous satellite and ground observations, we study spatial-temporal characteristics of the pulsations to determine causes of their generation.

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