Speaker: Dr. Emma Davies (GeoSphere Austria)
Title: Coronal Mass Ejections of Solar Cycle 25 – Insights from In Situ Multi-Spacecraft Measurements
Abstract: The complex processes affecting the propagation of interplanetary coronal mass ejections (ICMEs) make understanding and predicting their physical properties and global structure challenging from both fundamental and practical space weather perspectives. Multi-spacecraft observations of ICMEs across varying longitudinal and radial separations provide valuable insights into their general properties, expansion, and interactions with the solar wind environment during propagation. However, by tracking the properties of individual events, we often find significant variability compared to average trends.
As we enter the declining phase of Solar Cycle 25, we investigate the events of this cycle that follow previously determined relationships and those that deviate to ask whether we could better predict their impact using upstream solar wind monitors. To this end, we use the recently updated HELIO4CAST lineup catalogue (https://helioforecast.space/lineups) which includes ICMEs observed by Parker Solar Probe, Solar Orbiter, BepiColombo, STEREO A, and Wind to assess the local expansion of ICMEs measured at spacecraft in the inner heliosphere and at 1 au, comparing these to global expansion rates. We present examples of CMEs that caused the strongest geomagnetic storms of this solar cycle, using upstream measurements to produce hindcasts of the geomagnetic impact compared to observations, demonstrating both the importance and limitations of such in situ measurements for constraining future space weather forecasts.