Journal topic
Ann. Geophys., 17, 674–681, 1999
https://doi.org/10.1007/s00585-999-0674-4

Special issue: Solar System Plasmas

Ann. Geophys., 17, 674–681, 1999
https://doi.org/10.1007/s00585-999-0674-4

31 May 1999

31 May 1999

# A slow mode wave as a possible source of Pi 2 and associated particle precipitation: a case study

O. Saka2,1, O. Watanabe2, K. Okada2, and D. N. Baker3 O. Saka et al.
• 1Department of Physics, Kurume National College of Technology, Kurume , Japan
• E-mail: saka@ges.kurume-nct.ac.jp
• 2Department of Earth and Planetary Sciences, Kyushu University, Fukuoka, Japan
• 3Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, USA

Abstract. An intensification of auroral luminosity referred to as an auroral break-up often accompanies the onset of geomagnetic pulsation (Pi 2) at the dip-equator. One such auroral break-up occurred at 2239 UT on 16 June, 1986, being accompanied by weak substorm activity (AE~50 nT) which was recorded in all-sky image of Syowa Station, Antarctica (66.2°S, 71.8°E in geomagnetic coordinates). The associated Pi 2 magnetic pulsation was detected by a fluxgate magnetometer in the afternoon sector at the dip-equator (Huancayo, Peru; 1.44°N, 355.9° in geomagnetic coordinates; 12.1°S, 75.2°W in geographic coordinates; L=1.00). In spite of the large separation of the two stations in longitude and latitude, the auroral break-up and subsequent luminosity modulation were seen to be correlated with the wave form of the ground Pi 2 pulsation. This occurred in such a way that the luminosity maximum was seen to occur at the phase of maximum amplitudes of Pi 2 wave form. We argue that the observed correlation could be interpreted as indicating a Pi 2-modulation of a field-aligned acceleration of the low energy electrons that may occur near the equator of the midnight magnetosphere.

Key words. Magnetospheric physics (auroral phenomena; energetic particles · precipitating; MHD waves and instabilities)