Co-Rotating Interaction Region
Space weather zone between fast and slow solar wind streams producing geomagnetic storming without a solar flare.
Last refreshed: 11 April 2026 · Appears in 1 active topic
How much did the co-rotating interaction region on re-entry day affect Artemis II crew radiation?
Latest on co-rotating interaction region
- What is a co-rotating interaction region in space weather?
- A CIR forms at the boundary between fast and slow solar wind streams, creating an enhanced magnetic and particle environment that drives geomagnetic storms without requiring a solar eruption.Source: DB entity background
- Was there a solar storm during Artemis II re-entry?
- Yes. NOAA recorded G1-to-G2 geomagnetic storming from a co-rotating interaction region on 10 April, the day of Orion re-entry. NASA deferred the crew radiation dose to peer review.Source: DB event g1-to-g2-storming-on-orion-re-entry-day
- How does space weather affect astronaut radiation?
- Geomagnetic storms driven by CIRs or CMEs increase the energetic particle environment for spacecraft. For Artemis II, a CIR-driven storm coincided with re-entry day; the crew dose has been deferred to post-mission peer review.Source: DB events 2220 2219
Background
A co-rotating interaction region (CIR) forms at the boundary between a fast-moving and slow-moving stream of solar wind as the Sun rotates. The compressed interface produces an enhanced magnetic field and particle flux that can drive geomagnetic storms. Unlike coronal mass ejections, CIRs do not require a solar eruption: they are a structural feature of the solar wind that rotates with the Sun. NOAA Space weather Prediction Centre recorded G1-to-G2 geomagnetic storming produced by a CIR on 10 April 2026, the day of Orion re-entry and crew splashdown.
CIRs can produce elevated energetic particle environments that persist for hours to days as the interaction region sweeps past Earth. For a spacecraft in translunar space or returning through the inner magnetosphere, a CIR-driven storm increases the galactic cosmic ray and solar energetic particle background. The degree of shielding provided by Earth magnetic field varies with trajectory and re-entry angle. NASA has formally deferred the crew radiation dose to a post-mission research solicitation, meaning the CIR contribution to the Artemis II dose will be quantified through peer review rather than operational disclosure.
CIRs are one of the principal background radiation hazards for long-duration spaceflight. Unlike solar particle events, which can be predicted within hours of an eruption, CIR timing is more predictable because they co-rotate with the solar source. For deep space missions, CIR-driven periods of enhanced flux are a known and modellable risk that mission radiation budgets must account for.
