Consecutive bursts of Pi2-band and long-period pulsations during a northward and low-clock-angle IMF period

On 14 August 2004, four pulsation bursts, in a period up to 200 s from the Pi2 band, consecutively occurred at the SMALL and 210 MM arrays in the post-midnight sector. Meanwhile, the Double Star TC 1 probe in the plasma sheet at ~XGSM -11.0 Re, observed quasi-periodic magnetic fluctuations at each burst onset. The Cluster 4 probe in the north lobe at ~XGSM -14.0 Re, sensed Pi2-band magnetic perturbations at the second burst onset and long-period ones for the third and fourth bursts. No bursty flow activations occurred at the onset of the first and second bursts. Earthward flow bursts first appeared at TC 1 prior to the third burst onset and ~5 min later at Cluster 4. These flows persisted through the end of the last burst and appeared to have a same periodic variation as in the magnetic field at Cluster 4. Except for the second burst, geostationary LANL 97 probe at ~XGSM -2.0 Re also detected wave-like energetic proton fluxes. The mapping of ground pulsations onset timing to the solar wind observation just in front of Earth's magnetopause shows that they appear during a northward IMF period with low clock-angle variations. Spectral analyses show two distinct spectral features in which Pi2-band bursts become two harmonic and long-period ones monochromatic. Waveform comparisons show that Pi2-band bursts can result from a combination of fast magnetospheric and plasmaspheric cavity resonances and long-period ones from a fast magnetospheric cavity resonance. Although they do not have a one-to-one relationship with earthward plasma flows, these pulsations can be fast compressional waves expectedly driven by magnetic reconnection in the distant-Earth magnetotail under northward IMF as in the two-neutral-point model. Fig. 1. (a-b) The IMF By, the IMF Bz, and the IMF clock angle at 1 AU (corresponding to ~XGSM 17 Re) from 1910 UT to 2010 UT on 14 August 2004. (c-d) Three components of the magnetic field and the ion flow velocity at Cluster 4 (~XGSM -14.0Re). (e-f) Same as Figs. 1c-d, except for TC 1 (~XGSM -11.0Re). (g) The energetic proton flux at LANL 97 (~XGSM -2.0Re.) (h) The H component at the SMALL and 210 MM arrays. The vertical dashed lines denote the ground pulsation onsets. Consecutive pulstion onsets are marked with a a serial number for identification.