Pc5 geomagnetic pulsations, pulsating particle precipitation, and VLF chorus: Case study on 24 November 2006

Abstract

[1] The event (24 November 2006, ∼0400-0500 UT) of the simultaneous observations of Pc5 ULF geomagnetic pulsations, electron precipitation (CNA riometer absorption), and whistler-mode chorus, as well as solar wind (SW) and IMF parameters have been analyzed based on the data from IMAGE magnetometers, Finnish riometer array, and temporal VLF station. The visible correlation between the simultaneous occurrence of several minutes scale patches of chorus and pulsating CNA enhancements was found. The dynamic spectra of the riometer data showed a maximum at ∼3.5 mHz in the first half-hour interval and at ∼2.0 mHz in the second one, while the ULF pulsation spectra exhibit these two maxima in both intervals simultaneously. In the first time interval, the Pc5 pulsations at ∼3.5 mHz demonstrated the typical FLR feature. The SW dynamic pressure fluctuations showed a broad (1.5-3.5 mHz) spectral maximum in the first interval; however, in the second one, the simultaneous oscillations at ∼2.0 mHz were observed in SW pressure and in IMF Bz. The similar ∼2.0 mHz peak has been found in the spectra of Pc5 pulsations from auroral zone to the equator, in riometer absorption, and in VLF chorus power. We suggest that the modulation of particle precipitation and whistler-mode chorus patches was caused by the 2.0 mHz compressional component of Pc5 poloidal geomagnetic pulsations driven in the magnetosphere by SW dynamic pressure and IMF Bz disturbances.

Global observation of 24 November 2006 Pc5 pulsations by single mid-latitude underground [SQUID]<sup>2</sup> system

“…Besides, in the time interval 04:30-05:00 UT (sequence 2), the four wide resonances are in very good agreement with those of the polar stations in Manninen et al (2010). This point will be discussed further.…”

“…The event of 24 November 2006 is reported in the literature and analyzed through simultaneous multi-points Scandinavian stations by comparison with solar wind conditions (Manninen et al, 2010). These results show a relationship between Pc5 ULF pulsations, electron precipitation, whistler-mode chorus, solar wind and IMF parameters.…”

“…2 (top panels). The comparison of our results is made for the NS component, equivalent to the X direction shown in Manninen et al (2010). During the first sequence (04:00-04:30 UT), in the 1-6 mHz range, the domain of the Pc5-type pulsations, discrete emissions are pointed on the components NS, EW and Z.…”

“…The choice of a well studied event (Manninen et al, 2010) (Waysand et al, 2000. Located in the Laboratoire Souterrainà Bas Bruit de Rustrel, France (LSBB, http://lsbb.oca.eu) [SQUID] 2 is currently used to explore the daily geomagnetic field variations, giving information on the magnetic response.…”

Experimental evidence of the simultaneous occurrence of VLF chorus on the ground in the global azimuthal scale – from pre-midnight to the late morning

“…These VLF emissions can be a driver of energetic electron precipitation, which is typically accompanied by the chorus (e.g. Tsurutani and Smith, 1974;Anderson and Maeda, 1977;Bortnik and Thorne, 2007;Gołkowski and Inan, 2008;Manninen et al, 2010).…”