MESSENGER Magnetospheric Boundary Encounters

Description Dataset of MESSENGER magnetopause and bow shock boundary encounter times at Mercury, spanning the entire MESSENGER orbital mission from March 2011 to April 2015. Each entry records the start and end time of a boundary encounter, the type of boundary (magnetopause or bow shock, inbound or outbound), the encounter duration, and the associated orbit number. This list was derived from the Hollman (2026) MESSENGER boundary crossing catalogue (https://zenodo.org/records/21392216), which provides a set of magnetopause and bow shock crossing intervals for the full MESSENGER mission based on magnetometer data collected using machine learning methods. The crossings in that catalogue were programmatically parsed and reformatted into the orbit-indexed structure below, with each crossing assigned to its corresponding orbit number to allow orbit-by-orbit analysis of Mercury's magnetospheric boundary locations. The encounters are grouped by subsequent crossings which are of the same type and 'trajectory direction', which is determined based on the velocity of the spacecraft and the average boundary normal, meant to give a gauge one whether or not the spacecraft is moving inward or outward. The list is then post-processed to deal with 40 bow shock encounter edge cases in which this direction changes during the outbound bow shock encounter. This results in both the outbound and inbound encounters having an even number of crossings, which implies that the encounters start and end on different crossing types, i.e start on a bow shock in crossing and end on a bow shock out. This is rectified by shifting the first crossing on the inbound bow shock encounter back to the last crossing of the outbound encounter.This leaves 14 extra cases where there are an even number of crossings per encounter. Four of these are caused by the last crossing being an unphysical crossing, which is grouped into its own encounter type. The final 10 are all cases of rarefied solar wind events and can be inspected in the even_encounters script on GitHub. For the purposes of this list, these encounters are removed. Data Column Description Column name Description Time Start Timestamp of the start of the boundary crossing interval, in Coordinated Universal Time (UTC), format YYYY-MM-DD Hour:Minute:Second Time End Timestamp of the end of the boundary crossing interval, in Coordinated Universal Time (UTC), format YYYY-MM-DD Hour:Minute:Second. Equal to Time Start where the crossing was resolved as instantaneous. Label Type of boundary crossing. One of: BSI (Bow Shock Inbound), BSO (Bow Shock Outbound), MPI (Magnetopause Inbound), MPO (Magnetopause Outbound), UNI (Unphysical encounter, Inbound i.e solar wind -> magnetosphere ), UNO (Unclassified encounter, Outbound i.e magnetosphere -> solar wind) Number of Crossings The number of times the boundary is crossed during the encounter. Encounter Duration Duration of the crossing interval, in hours (Time End − Time Start). When 0, it means the encounter was instantaneous, and it only contained one crossing. Orbit Number Orbit number of the MESSENGER spacecraft during which the crossing occurred, indexed against the mission's periapsis/apoapsis sequence This data was constructed using the Hollman (2026) MESSENGER boundary crossing list and the hermpy Python package (https://github.com/daraghhollman/hermpy). The code used to generate this list can be found in the code/src/hermpymod/functions/encounters.py file of this GitHub repository (https://github.com/odanny-oc/DIASMercuryMagnetosphere).