Radio signatures of energetic electrons in the inner heliosphere

Energetic electrons are abundant in the solar system. Understanding how these electrons are accelerated and propagate from the Sun to the Earth is a fundamental problem in solar and heliospheric physics and is one of the main scientific objectives of the recently launched NASA Parker Solar Probe (PSP) and ESA Solar Orbiter (SolO) missions. Energetic electrons are abundantly accelerated during solar flares and by Coronal Mass Ejection shocks and are frequently observed as solar radio bursts. The energetic electrons can be diagnosed through X-ray emission in the dense regions of solar atmosphere, and via radio emission, and with in-situ particle detectors in the interplanetary space. Unlike other emission mechanisms, radio emission is the only diagnostic tool allowing continuous observation of these energetic electrons from the Sun to the Earth. As the local plasma density decreases from the Sun into the heliosphere, radio emission, generated by plasma processes near the local plasma frequency, can be detected from hundreds of MHz down to tens of kHz at 1AU. The combination of radio observations from the ground above ionospheric cut-off and from spacecrafts below the cut-off provides the unprecedented coverage of the energetic electrons in the solar corona and heliosphere. Availability of ground-based observations coupled with 4 radio observing spacecrafts (Wind, STEREO, Solar Orbiter (SolO), Parker Solar Probe (PSP)) provides unique opportunities for the studies unavailable before. Combining the observations, kinetic simulations of electron transport and radio wave scattering simulations, the project will provide new insights into the evolution of energetic electrons and the physics of the inner heliosphere/outer corona.