PC индекс как показатель энергии солнечного ветра, поступающей в магнитосферу (итоги)

The paper includes a short review of advantages of the PC index which is a characteristic of the magnetic activity in the polar caps in the northern (PCN) and southern (PCS) hemispheres. It is demonstrated that the PC index properly responds to variations of the geoeffective interplanetary electric field E coupling with the magnetosphere, on the one side, and predetermined the development of magnetospheric disturbances (magnetic storms and substorms), on the other side. These experimental results formed the physical backgrounds for concept that the ground-based PC index characterizes the solar wind energy input into the magnetosphere. It is shown that problem of random discordances in behavior and value of the PCN and PCS indices during the summer/winter seasons is easily solved by choosing the PC index in the winter polar cap (PCwinter) as the best characteristic of the polar cap magnetic activity. At present the PC index is successfully applied to validate the utility of SW data presented at OMNI website (i.e. to verify whether or not the solar wind, measured in the Lagrange point, encountered the magnetosphere in reality). A special procedure agreed by the Arctic and Antarctic Research Institute (responsible for production of PCS index) and DTU Space (responsible for production of PCN index) ensures the calculation of the 1-min PC indices in quasi-real time based on data of magnetic observations at the polar cap stations Vostok (Antarctic) and Qaanaaq (Greenland).Дается краткий обзор достижений, полученных при использовании индексов магнитной активности в северной (PCN) и южной (PCS) полярных шапках. Показано, что PC индекс четко отвечает на вариации геоэффективного межпланетного электрического поля E, взаимодействующего с магнитосферой, с одной стороны, и является предвестником магнитосферных возмущений (магнитных бурь и суббурь), с другой стороны. Эти экспериментальные факты послужили основой представления о PC индексе как характеристике энергии солнечного ветра, поступающей в магнитосферу. Показано, что проблема случайных расхождений в поведении и величине PCN и PCS индексов в сезоны зима/лето решается выбором PC индекса в зимней шапке (PCwinter) как наиболее адекватной характеристики магнитной активности. В настоящее время PC индекс успешно применяется при оценке пригодности данных сайта OMNI о параметрах солнечного ветра (т.е. для проверки реальности контакта с магнитосферой солнечного ветра, измеренного в точке либрации). Специальная процедура, согласованная Арктическим и антарктическим НИИ (который ответственен за производство PCS индекса) и Датским техническим университетом (который ответственен за производство PCN индекса), обеспечивает расчет в реальном времени 1-мин PC индекса по данным магнитных наблюдений на полярных станциях Восток (Антарктика) и Туле (Гренландия)

Geosynchronous magnetopause crossings and their relationships with magnetic storms and substorms

The paper investigates the strengthening of magnetospheric activity related to geosynchronous magnetopause crossings (GMCs). We make a list of GMC events using the empirical magnetopause model (Lin et al., 2010) and hourly averaged OMNI data and find which solar wind and magnetospheric conditions accompany and follow the GMCs. The GMCs are mostly caused by the impact of interplanetary coronal mass ejections (ICMEs) and/or interplanetary shocks often with a strong increase in the density and a moderate increase in velocity. The average solar wind density during the first GMC hour is higher than 20 cm−3 in 70 % cases, while the velocity is higher than 500 km/s in 56 % cases. The hourly interplanetary magnetic field (IMF) BZ is negative in 87 % cases. The average over all events SMU (SML), Kp, and PC indices reach maxima (minima) in 1 hour after the GMC beginning, while the delay of the minimum of the Dst index is usually 3–8 hours. These average time delays do not depend on the strength of the storms and substorms. The SML (Dst) minimum is less than -500 nT (-30 nT) in the next 24 hours in 95 % (99 %) cases, i.e. the GMC events are mostly followed by magnetic storms and substorms. We compare solar wind and magnetospheric conditions for GMCs connected with ICMEs and stream interaction regions (SIRs). Our study confirms that the ICME-related events are characterized by stronger ring current and auroral activity than the SIR-related events. The difference might be explained by the different behavior of the solar wind velocity

Remote Detection of Drift Resonance Between Energetic Electrons and Ultralow Frequency Waves: Multisatellite Coordinated Observation by Arase and Van Allen Probes

We report the electron flux modulations without corresponding magnetic fluctuations from unique multipoint satellite observations of the Arase (Exploration of Energization and Radiation in Geospace) and the Van Allen Probe (Radiation Belt Storm Probe [RBSP])‐B satellites. On 30 March 2017, both Arase and RBSP‐B observed periodic fluctuations in the relativistic electron flux with energies ranging from 500 keV to 2 MeV when they were located near the magnetic equator in the morning and dusk local time sectors, respectively. Arase did not observe Pc5 pulsations, while they were observed by RBSP‐B. The clear dispersion signature of the relativistic electron fluctuations observed by Arase indicates that the source region is limited to the postnoon to the dusk sector. This is confirmed by RBSP‐B and ground‐magnetometer observations, where Pc5 pulsations are observed to drift‐resonate with relativistic electrons on the duskside. Thus, Arase observed the drift‐resonance signatures “remotely,” whereas RBSP‐B observed them “locally.