Study on Langmuir Wave Activities Within the Magnetic Cloud Boundary Layers

Two particular types of Langmuir wave activities are found within the Magnetic Cloud Boundary Layers (MCBL): Langmuir wave enhancements in entire region of MCBL compared with the adjacent magnetic cloud body and sheath region for majority MCBL and the rapid Langmuir wave burst phenomena associated with broad-band Doppler shifted ion-coustic wave activities for a few MCBL. On 3 Oct., 2000, WIND detected a typical MCBL inside which rapid Langmuir waves burst was observed. The Langmuir waves burst was right corresponded to the magnetic field minimum within the MCBL. The analysis based on high resolution electron distribution function data indicates that the bump-on-tail instability, resulting from the electron beam with beam velocity vb about7×10^3 km/s, is responsible for the rapid Langmuir waves burst.