Origin of coronal and interplanetary shocks: A new look with Wind spacecraft data

Abstract

We have investigated type II radio bursts in the solar corona using data from ground‐based radio telescopes (>18 MHz) and from the Radio and Plasma Wave experiment (WAVES) on board the WIND spacecraft (<14 MHz). The wavelength range of the WAVES experiment includes the 2‐ to 14‐MHz band, previously unobserved from space. We found that all 34 coronal type II bursts observed over a period of 18 months (November 1, 1994, to April 30, 1996), decayed within a few solar radii and did not propagate into the interplanetary medium. On the other hand, most of the accompanying type III radio bursts observed by the ground‐based instruments were observed to continue into the interplanetary medium as the electron beams propagated freely along open magnetic field lines. Over the same period of time, other instruments on board the WIND spacecraft detected about 18 interplanetary shock candidates, which seem to be unrelated to the coronal type II bursts. This result confirms the idea that the coronal and interplanetary shocks are two different populations and are of independent origin. We reexamine the data and conclusions of Gosling et al. [1976], Munro et al. [1979], and Sheeley et al. [1984] and find that their data are consistent with our result that the coronal type II bursts are due to flares. We also briefly discuss the implications of our result to the modeling studies of interplanetary shocks based on input from coronal type II radio bursts.