High resolution studies of intermediate drift bursts

Abstract

We report high resolution observations of the Intermediate Drift (IMD) bursts in decimetric band (ν = 950 2650 MHz). With a time resolution of 20 - 50 ms and a frequency resolution of 4 - 10 MHz, we are able to estimate the characteristics of IMD bursts such as the bandwidth and duration of the emission. Frequency drift rate and its dependence on the frequency are derived for individual IMD structures. All IMD bursts analyzed show negative drift rate. The values are of the order of ‑28 ‑274 MHz s‑1. The drift rates normalized by the mean frequency are ranged between ‑0.20 s‑1 and ‑0.02 s‑1. Both the frequency drift rate and its frequency dependence provide important clues to the emission mechanisms of IMD. A comparison and a critique of the existing models based on the plasma and the maser emissions with modulation by Alfvén solitons as well as the whistler wave model are presented