• Journal of Astronomy and Space Sciences
• /
• 제25권4호
• /
• pp.375-382
• /
• 2008

On August 31, 2001, ${\sim}$ 1705 - 1718 UT, Cluster was located near the midnight magnetotail, GSE (x, y, z) ${\sim}$ (-19, - 2,2) RE, and observed fast earthward flow bursts in the vicinity of the neutral sheet. They occurred while the tail magnetic field suddenly increased. Using simultaneous measurements in the solar wind, at geosynchronous orbit, and on the ground, it is confirmed that tail magnetic field enhancement is due to an increased solar wind pressure. In the neutral sheet region, strongly enhanced earthward flow bursts perpendicular to the local magnetic field $(V_{{\perp}x})$ were observed. Auroral brightenings localized in the pre-midnight sector (${\sim}$ 2200 - 2400 MLT) occurred during the interval of the $V_{{\perp}x}$ enhancements. The $V_{{\perp}x}$ bursts started ${\sim}$ 2 minutes before the onset of auroral brightenings. Our observations suggest that the earthward flow bursts are associated with tail reconnection directly driven by a solar wind pressure impulse and that $V_{{\perp}x}$ caused localized auroral brightenings.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
• /
• 한국우주과학회 2003년도 한국우주과학회보 제12권2호
• /
• pp.33-33
• /
• 2003

A clear bipolar (negative/positive) signature in the Ey component was observed by the Cluster satellite in the magnetotail during a sudden impulse (si) on October 11, 2001 (day 284). During the interval of the negative perturbation in Ey, the magnetic field strength in Bx, a dominant magnetic field component, was nearly constant. However, the amplitude of Bx was strongly enhanced during the positive Ey perturbation. We suggest that the observed E and B field variations are due to outward/inward plasma motions, associated with expanded and then compressed magnetopause variations. We also observed quasi-periodic geomagnetic perturbations in the Pc5 band (∼1-6 mHz) at the low-latitude ground station Kakioka (L = 1.25) following the si event. They were highly correlated with the magnetic field perturbations at Cluster in the magnetotail (Xgse = ∼12 Re). We show that the source of these perturbations is the quasi-periodic solar wind pressure variations moving tailward.