Abstract
Abstract. We present a global climatology of Pc1 pulsations as observed by the CHAMP satellite from 2000 to 2010. The Pc1 center frequency and bandwidth are about 1 and 0.5 Hz, respectively. The ellipticity is mostly linear with the major axis almost aligned with the magnetic zonal direction. The diurnal variation of Pc1 occurrences shows a primary maximum early in the morning and a secondary maximum during pre-midnight hours. The annual variations of the occurrence rates exhibit a clear preference for local summer. The solar cycle dependence of the occurrence rate reveals a maximum at the declining phase (2004–2005). Neither magnetic activity nor solar wind velocity controls the Pc1 occurrence rate significantly. Pc1 occurrence rate peaks at subauroral latitudes, but the steep cutoff towards higher latitudes is due to auroral field-aligned currents masking the Pc1 pulsations. The center frequency of Pc1 pulsations does not show a clear dependence on latitude. The global distribution of Pc1 exhibits highest occurrence rates near the longitude sector of the South Atlantic Anomaly. Pc1 events at auroral latitudes, although they are rarely detected, show a clear occurrence peak around local noon. A majority of the auroral Pc1 events are observed during solar minimum years.
Highlights
Model DGeevoeslocipemnteifnictiepwnxlagepv,efetrrhsoieemonpfcotdehliaeafrfsieszoerauertinriecotsenoorrcfeiaggcniihnocasnhn,Msagotneroogs(ted2ihn)(ee1wtgh)lrhedoDeiGurunenpetedtrhovoeotphaeepsesrluutopcliDpuseipaieslesst.rcmiapnoFutosinotosessriinifotnepiisnoxcastmnassmaoya-fPc1 pulsations are geomagnetic fluctuations in the frequency region where the frequency is the same as the cross-over frerange between 0.2 to 5 Hz
Park et al.: Pc1 pulsations pulsations can be ducted across the magnetic field so that they are observed at locations, which are not conjugate to the high-altitude source region (Lysak and Yoshikawa, 2006)
This method helps to prevent contaminations by magnetic fluctuations originating from broad-band pulsations, equatorial plasma bubble (EPB) (e.g. Stolle et al, 2006) or from medium-scale traveling ionospheric disturbance (MSTID) (e.g. Park et al, 2009)
Summary
As a consequence of the features outlined in the previous paragraph, the climatology of Pc1 pulsations is expected to show differences between observations in nearequatorial/high-altitude regions, in the ionosphere, and on the ground. In the outer magnetosphere near the geomagnetic equator, Pc1 pulsations generally occur in the earlyafternoon sector (Anderson et al, 1992a,b; Erlandson and Ukhorskiy, 2001; Halford et al, 2010; Clausen et al, 2011; Keika et al, 2013). The occurrence rate depends in a complex manner on magnetic latitude (MLAT) and magnetic local time (MLT).
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