Impulsive Solar Energetic Particle Events at High Heliolatitude

We present observations of impulsive solar energetic particle events on 2025 March 20 observed at high heliolatitude by Solar Orbiter and compare them with near-ecliptic observations by the Wind spacecraft. Solar Orbiter, located at 0.38 au, a Carrington longitude of 139.7◦ and a latitude of −16.6◦, detected two ion events at ∼0.1-6 MeV and two electron events at ∼40-200 keV. These events exhibit clear velocity dispersion and strong field-aligned anisotropy. Velocity dispersion analysis of both ion and electron events yields path lengths consistent with the nominal Parker spiral length. Furthermore, the first electron event exhibits a double-power-law spectrum with an index of 2.3 ± 0.3 below a break energy of 58 ± 4 keV and an index of 4.0±0.2 at energies above, while the second electron event exhibits a single-power-law spectrum with an index of 4.6 ± 0.2. In contrast, the Wind spacecraft, located at 1 au, a Carrington longitude of 120.0◦, and a latitude of −7.1◦, observed only one electron event, which shows insignificant velocity dispersion and arrives ∼20 min later than expected. The Parker spiral footpoints of the two spacecraft were separated by ∼15◦ in longitude and ∼10◦ in latitude, providing a lower limit on the angular extent of impulsive electron events. The delayed arrival at Wind may be attributed to the electron diffusion in the solar source region.