Radio astronomical tools for space weather research – ORME

The ORME project aims at developing radio astronomical tools for the prediction of major solar disturbances in the space environment of the Earth, solar energetic particles (SEPs) and coronal mass ejections (CMEs). These disturbances may lead to major space weather events that affect spaceborne and possibly airborne technology and radio communications depending on wave propagation in the ionosphere.

Electromagnetic emissions can be used for short-term forecasting (about 1 hour for SEPs, a day or more for CMEs), because they are the first signatures of a solar event with potential geo-effectiveness. Using radio data is presently not common, but it would provide a safer element of space-weather services than space borne observations, because much of the radio window is observable from ground. Radio astronomical tools are hence well protected against extreme space weather events.

The ORME project comprises on the one hand systematic scientific studies on the relationship between radio emission, CMEs and SEPs, with the following objectives:
(1) We want to carry out statistical studies of the relationship between microwave bursts (flux density, fluence, spectrum) and SEPs (peak intensity, energy spectrum) taking into account that an SEP event may have contributions from both flares and CMEs. We will use metre wave radio bursts as tracers of particles escaping from the flare, which will allow us to distinguish SEP events with a mixed flare-CME contribution from events where only the CME acceleration contributes. This has not been done in previous studies.
(2) Empirical relationships between the microwave frequency spectrum and the SEP energy spectrum will be searched for events where flare-accelerated particles escape to interplanetary space and can hence contribute to SEPs measured near Earth. We will especially compare the microwave spectra of SEP events extending to very high (relativistic) energies and SEP events that are restricted to lower energies.
(3) We will investigate if the spatial extent of metre wave radio emission, which has been shown in a few case studies to outline the CME extent in the low corona, can be used to predict if the CME will intercept the Earth. To this end we will carry out joint studies of CMEs observed by SoHO and STEREO (EUV and white light) and by the Nançay Radioheliograph in order to compare the radio sources with the 3D structure of the CME. Complementary data, including the heliospheric imager of STEREO, will be used to study the interplanetary propagation of the CME and the question whether it intercepts the Earth and triggers a geomagnetic storm.

The second objective of the project is the development of algorithms for the automated detection and feature identification in dynamic spectra of solar radio bursts at decimetre-to-metre wavelengths. The algorithms will range from the detection of the presence of a radio burst, with an alert message for the observer or space weather forecaster, to the automated feature recognition in order to identify the spectral type of the radio emission. Emphasis will be laid on the space-weather relevant radio emissions, i.e. bursts emitted by electron beams travelling to the interplanetary space (type III bursts), by shock waves (type II bursts) and by trapped non thermal electron populations in CMEs (type IV bursts). Such a feature recognition will provide researchers with a tool to objectively analyse dynamic radio spectra and to extract data on a given event type from large observational databases. It will also provide valuable space weather tools. The simple burst detection will be validated with the presently existing real time data delivery of the ORFEES spectrograph (Nançay) to the FEDOME space weather demonstrator of the French Air Force, and will be available to the FEDOME team. The feature recognition algorithms will be tested in the laboratory using the ORFEES database.