Whitepaper #384 in the Decadal Survey for Solar and Space Physics (Heliophysics) 2024-2033. Main topics: basic research. Additional topics: inner heliosphere; space-based missions/projects; user-need-driven basic space weather research.
The internal structure and evolution of ICMEs in the inner heliosphere remains poorly understood. Similarly, the transport and diffusion of solar energetic particles on their way to 1 AU is surrounded by controversy. This white paper outlines possible next research objectives and a possible multi-spacecraft mission concept (HELIIX) that would provide the measurements to achieve these objectives.