Currents of quasi-trapped particles and their interaction with the geomagnetic field /symmetrical approximation/

Currents of quasitrapped particles and their interaction with geomagnetic fiel

Invariability of relationship between the polar cap magnetic activity and geoeffective interplanetary electric field

The PC (polar cap) index characterizing the solar wind energy input into the magnetosphere is calculated with use of parameters α, β, and &phi;, determining the relationship between the interplanetary electric field (<i>E</i>_KL) and the value of magnetic activity &delta;<i>F</i> in the polar caps. These parameters were noted as valid for large and small <i>E</i>_KL values, and as a result the suggestion was made (Troshichev et al., 2006) that the parameters should remain invariant irrespective of solar activity. To verify this suggestion, the independent sets of calibration parameters α, β, and &phi; were derived separately for the solar maximum (1998–2001) and solar minimum (1997, 2007–2009) epochs, with a proper choice of a quiet daily variation (QDC) as a level of reference for the polar cap magnetic activity value. The results presented in this paper demonstrate that parameters α, β, and &phi;, derived under conditions of solar maximum and solar minimum, are indeed in general conformity and provide consistent (within 10 % uncertainty) estimations of the PC index. It means that relationship between the geoeffective solar wind variations and the polar cap magnetic activity responding to these variations remains invariant irrespective of solar activity. The conclusion is made that parameters α, β, and &phi; derived in AARI#3 version for complete cycle of solar activity (1995–2005) can be regarded as forever valid

Solar Transients disturbing the Terrestrial Magnetic Environment at Higher Latitudes

Geomagnetic field variations during five major Solar Energetic Particle (SEP) events of solar cycle 23 have been investigated in the present study. The SEP events of 01 oct 2001, 04 Nov 2001, 21 Apr 2002 and 14 May 2005 have been selected to study the geomagnetic field variations at two high-latitude stations, Thule and Resolute Bay of the northern polar cap. We have used the GOES protn flux in seven different energy channels. All the proton events were associated with geoeffective or Earth directed CMEs that caused intense geomagnetic storms in response to geospace. We have taken high-latitude indices, AE and PC, under consideration and found fairly good correlation of thees with the ground magnetic field records during the five proton events. The departure of H component during the events were calculated from the quietest day of the month for each event. The correspondence of spectral index, inferred from event integrated spectra, with ground magnetic signatures along with Dst and PC indices have been brought out. From the correlation analysis we found very strong correlation to exist between the geomagnetic field variations and high latitude indices AE and PC. To find the association of geomagnetic storm intensity with proton and geomagnetic field variations along with the Dst and AE index. We found a strong correlation (0.88) to exist between the spectral indices and magnetic field deviations and also between spectral indices and AE and PC.Comment: Accepted for publication in Astrophys Space Sci (2013) (19 pages, 6 figures, 2 tables

Effective area for the northern polar cap magnetic activity index

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/94783/1/grl12045.pd

Magnetic local time dependence of geomagnetic disturbances contributing to the AU and AL indices

The Auroral Electrojet (AE) indices, which are composed of four indices (AU, AL, AE, and AO), are calculated from the geomagnetic field data obtained at 12 geomagnetic observatories that are located in geomagnetic latitude (GMLAT) of 61.7°-70°. The indices have been widely used to study magnetic activity in the auroral zone. In the present study, we examine magnetic local time (MLT) dependence of geomagnetic field variations contributing to the AU and AL indices. We use 1-min geomagnetic field data obtained in 2003. It is found that both AU and AL indices have two ranges of MLT (AU: 15:00-22:00MLT, ~06:00 MLT; and AL: ~02:00 MLT, 09:00-12:00 MLT) contributing to the index during quiet periods and one MLT range (AU: 15:00-20:00MLT, and AL: 00:00-06:00 MLT) during disturbed periods. These results are interpreted in terms of various ionospheric current systems, such as, Sqp, Sq, and DP2

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)

Polar cap index (PC) as a proxy for ionospheric electric field in the near‐pole region

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95640/1/grl13514.pd

On the usage of geomagnetic indices for data selection in internal field modelling

We present a review on geomagnetic indices describing global geomagnetic storm activity (Kp, am, Dst and dDst/dt) and on indices designed to characterize high latitude currents and substorms (PC and AE-indices and their variants). The focus in our discussion is in main field modelling, where indices are primarily used in data selection criteria for weak magnetic activity. The publicly available extensive data bases of index values are used to derive joint conditional Probability Distribution Functions (PDFs) for different pairs of indices in order to investigate their mutual consistency in describing quiet conditions. This exercise reveals that Dst and its time derivative yield a similar picture as Kp on quiet conditions as determined with the conditions typically used in internal field modelling. Magnetic quiescence at high latitudes is typically searched with the help of Merging Electric Field (MEF) as derived from solar wind observations. We use in our PDF analysis the PC-index as a proxy for MEF and estimate the magnetic activity level at auroral latitudes with the AL-index. With these boundary conditions we conclude that the quiet time conditions that are typically used in main field modelling (, and ) correspond to weak auroral electrojet activity quite well: Standard size substorms are unlikely to happen, but other types of activations (e.g. pseudo breakups ) can take place, when these criteria prevail. Although AE-indices have been designed to probe electrojet activity only in average conditions and thus their performance is not optimal during weak activity, we note that careful data selection with advanced AE-variants may appear to be the most practical way to lower the elevated RMS-values which still exist in the residuals between modeled and observed values at high latitudes. Recent initiatives to upgrade the AE-indices, either with a better coverage of observing stations and improved baseline corrections (the SuperMAG concept) or with higher accuracy in pinpointing substorm activity (the Midlatitude Positive Bay-index) will most likely be helpful in these efforts.</p