Relation of PC index to the geomagnetic storm Dst variation |
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| Authors: | O Troshichev D Sormakov A Janzhura |
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| Institution: | 1. Dipartimento di Ingegneria Astronautica Elettrica ed Energetica (DIAEE), University of Rome “La Sapienza”, via Salaria 851, 00138 Rome, Italy;2. Dipartimento di Ingegneria Meccanica e Aeronautica (DIMA), University of Rome “La Sapienza”, via Eudossiana 18, 00184 Rome, Italy;1. Department of Electrical and Computer Engineering, University of New Mexico, NM, USA;2. High Altitude Observatory, National Center for Atmospheric Research, Boulder, CO, USA;3. Department of Physics, University of Texas at Arlington, TX, USA;4. Solar Physics Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD, USA;5. Department of Geophysics, Peking University, Beijing, China;1. Division of Space Technology, Department of Computer Science, Electrical and Space Engineering, Luleå University of Technology, Kiruna, Sweden;2. Universidad Alcalá de Henares (UAH), Dpto. Física y Matemáticas, Campus Científico-Tecnológico (Externo), Alcalá de Henares, Madrid, Spain;3. Instituto Andaluz de Ciencias de la Tierra (UGR-CSIC), Avenida de las Palmeras 4, Armilla, Granada, Spain;1. Arctic and Antarctic Research Institute, St. Petersburg, Russia;2. St. Petersburg State University, St. Petersburg, Russia;1. Dipartimento di Fisica, Università di Roma “La Sapienza”, 00185 Rome, Italy;2. Istituto Nazionale di Geofisica e Vulcanologia, 00143 Rome, Italy;3. Universidade do Vale do Paraíba, 12244-000 São José dos Campos, Brazil;4. Laboratorio de Telecomunicaciones, DEEC, FACET, Universidad Nacional de Tucumán, 4000 Tucumán, Argentina;5. Laboratorio de Ionósfera, Departamento de Física, FACET, Universidad Nacional de Tucumán, 4000 Tucumán, Argentina;6. CIASUR, Facultad Regional Tucumán, Universidad Tecnológica Nacional, 4000 Tucumán, Argentina;7. Consejo Nacional de Investigaciones Científicas y Técnicas, 1033 Buenos Aires, Argentina |
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| Abstract: | Relationships between the polar cap magnetic activity index PC and the magnetic storm Dst index have been studied for the magnetic storms with duration more 12 h and peak value Dst<?30 nT and, observed in 1998–2002 and 2004–2005. Along with PC index the geoeffective interplanetary electric field Em was also examined. It has been found that all examined storms, lying in range from ?30 to ?373 nT, started when the PC index and, correspondingly, the Em field firmly exceeded the threshold >2 mV/m. In particular, the “anomalous” magnetic storm on January 21–22, 2005 occurring under conditions of northward IMF BZ (Du et al., 2008) is usual phenomena fitted well with the threshold restriction owing to the large IMF By component input. The maximal storm depression (the peak value of Dst) is linearly related to the quantities Em and PC, averaged for the time interval from the storm beginning to the storm maximum. The correlation between Dst and PC is more steady and larger than correlation between Dst and Em, the latter being dependent on Em value (effect of “Dst saturation”). The moment of the firm descent of the Em and PC quantities below the threshold level ～2 mV/m is indicative of the depression damping and transition to the recovery phase. The results are consistent with the similar peculiarities revealed for substorms development (Troshichev and Janzhura, 2009) and support the conclusion that the PC index is a reliable proxy characterizing the solar wind energy having been entered into the magnetosphere. |
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