Geomagnetic Disturbance And The Near-earth Space For Non-earthquake Electromagnetic Disturbances Excited By The Magnetic Tail High-speed Stream

This report first uses the plasma data from Cluster and TC-1 and geomagnetic data to study the geomagnetic signatures of the current wedge produced by fast flow braking in the plasma sheet. The three fast flows studied here occurred in a very quiet background and are accompanied by no (or weak) particle injections, thus avoiding the influences from other disturbances. All the geomagnetic signatures of substorm current wedge can be found in the geomagnetic signatures of current system produced by the braking of fast flows, indicating that the fast flows can produce a complete current wedge which contains post-midnight downward and pre-midnight upward field aligned currents, and westward electrojet. The Pi2 precursors exist not only at high latitudes, but also at mid-latitudes. The starting times of mid-latitude Pi2 precursors can be identified more precisely than those of high latitude Pi2 precursors, providing a possible method to determine the starting time of fast flows in their source regions. The AL drop that a BBF produces is proportional to its velocity and duration. In three cases, the AL drops are smaller than 100 nT. Since the AE increase of a typical substorm is larger than 200 nT, whether a substorm can be triggered depends mainly on the conditions of the braking regions prior to fast flows. The observations of solar wind prior to the three fast flows suggest that it is difficult for the fast flows to trigger a substorm when the IMF Bz of solar wind is weakly southward.Then the present report analyzes the non-Earthquake electromagnetic disturbances in the near Earth space. In the near Earth space, satellites often observe electromagnetic waves originated from space, which include electromagnetic ion cyclotron waves, whistler waves, hiss, chorus and geomagnetic pulsations. Among these waves, plasmaspheric hiss and chorus can be observed during geomagnetic quiet times, but can be much enhanced during geomagnetic storms and substorms. Those electromagnetic waves originated from the surface of the Earth can be both natural and artificial electromagnetic waves. The artificial electromagnetic waves mainly refer to the VLF waves emitted by VLF transmitters and the harmonic waves produced by power lines.Besides the above-mentioned electromagnetic waves, satellites themselves in operation can also produce electromagnetic noise in the frequency range of 0-200 Hz.