Physical interpretation of measured EUV-wave speeds

Determine which physical response, if any, a published EUV-wave speed traces, accounting for the selected image feature, passband, cadence, propagation sector, fitting interval, and projection geometry.

Background

Published EUV-wave speeds vary widely because different studies use different observational passbands, cadences, sectors, front definitions, and fitting intervals. The paper emphasizes that a reported image speed is an output of an observation operator rather than a primitive physical quantity.

The unresolved issue is whether a particular measured front corresponds to a fast or slow MHD response, a shock, a CME-related front, a dimming or rarefaction, or another evolving structure. Resolving this requires matching the tracked feature and measurement procedure before assigning a physical interpretation.

References

A narrower problem remains unresolved in practice: what exactly does a published EUV-wave speed measure?

— Untangling EIT Waves: What a Measured Speed Actually Traces  (2609.10167 - Podladchikova, 9 Sep 2026) in Section 1, “Why another synthesis after nearly three decades?”