Inverse velocity dispersion events in multi-spacecraft analyses

It is well established that solar energetic particles events typically show normal velocity dispersion (VD), where the release of particles is independent of energy, producing anpattern with an earlier onset at higher energies. Recent measurements by NASA’s Parker Solar Probe (PSP) and ESA’s Solar Orbiter(SolO), however, reveal events with a mixed dispersion behaviour: VD at lower energies, but an inverse velocity dispersion (IVD) at higher energies, in which higher-energy particles arrive later than lower-energy ones. Building on our earlier SolOsurvey of 10 IVD proton events and its interpretation in terms of time-dependent shock diffusive acceleration, we extend the method to multi-point IVD observations by SolO, STEREO-A (STA), and PSP. For events observed at multiple longitudes, we apply consistent VDA/IVD fitting to infer release heights and radial mean free paths at each spacecraft and quantify their variability with magnetic connection. Observers with larger connection angles systematically show delayed VDA release times; we compare these delays with EUV-wave arrival at the magnetic footpoint or with fitted CME connection times. We further investigate inter-spacecraft SEP properties, such as time-integrated spectra, spectral breaks, and pitch-angle anisotropies.