A tool to improve space weather forecasts: Kilometric radio emissions from Wind/WAVES

For decades, space environment forecasters have used the appearance of metric Type II radio emission as a proxy for eruptions in the solar corona. The drift rate of these near-Sun emissions is often turned into a speed, commonly assumed to be that of an MHD shock. However, their utility to forecast shock arrival times has not proved to be conclusive. Metric emissions can be detected by ground-based antennae, while lower-frequency components of these slowly drifting emissions can also be tracked by spacecraft in interplanetary space, as far down in frequency as that of the local plasma frequency. For a spacecraft at L1, this corresponds to about 25 kHz, or an electron density of about 7 cm(-3) in the ambient solar wind. Here we report a recent study that aims to improve the predictions of shock arrival time at L1 by means of the low-frequency emissions detected by WIND/WAVES. This technique, implemented on an extensive sample of hectometric and kilometric type II radio bursts, has yielded promising results.