Observation of the Large‐Amplitude andFast‐Damped Plasma Sheet FlappingTriggered by Reconnection‐InducedBallooning Instability

<p>&#160;<span class="fontstyle0">In this study, we reported the large&#8208;amplitude and fast&#8208;damped flapping of the plasma sheet,<br />which co&#8208;occurred with magnetic reconnection. Data from the Double Star TC&#8208;1 and Cluster satellites<br />were used to analyze the features of the plasma sheet flapping 1.4 R</span><span class="fontstyle0">E </span><span class="fontstyle0">earthward of an ongoing magnetic<br />reconnection event. The flapping was rapidly damped, and its amplitude decreased from the<br />magnetohydrodynamics scale to the subion scale in 5 min. The variation in the flapping period (from 224 to<br />20 s) indicated that the source of the flapping had highly dynamic temporal characteristics. The plasma sheet<br />flapping propagated duskward through a kink&#8208;like wave with a velocity of 100 km/s, which was in<br />agreement with the group velocity of the ballooning perturbation. A correlation analysis between the<br />magnetic reconnection and plasma sheet flapping indicated that the magnetic reconnection likely facilitated<br />the occurrence of ballooning instability by altering the state of plasma in the downstream plasma sheet. In<br />this regard, the reconnection&#8208;induced ballooning instability could be a potential mechanism to generate<br />the flapping motion of the plasma sheet.</span>&#160;</p>