Lucie Green on the sun

Episode Summary

Executive Summary: Lucy Green traces her journey from art to astrophysics and explains how her research on the Sun’s magnetic activity helped define space weather as a serious societal risk. The conversation covers coronal mass ejections, satellite and power-grid vulnerabilities, the 2012 near miss, government engagement, and future forecasting missions designed to improve warning times.

Main Topics: From art to astrophysics (Priority: 5/5): Green describes leaving an art-focused path after school to return to physics because she missed its logic, problem-solving, and certainty. Her story frames science as both intellectually rigorous and aesthetically compelling. Why the Sun is a scientific object of fascination (Priority: 4/5): She explains that the Sun is visually beautiful, structurally rich, and scientifically fundamental, combining aesthetics with deep physical processes like nuclear fusion and magnetic activity. Coronal mass ejections and solar magnetism (Priority: 5/5): The discussion explains how the Sun’s charged fluid and frozen-in magnetic field create stressed structures that can erupt as coronal mass ejections, releasing vast energy and mass into space. Space weather as a risk to modern infrastructure (Priority: 5/5): Green outlines how solar eruptions can damage satellites, disrupt GPS and communications, and create geomagnetic currents that threaten electricity networks and national infrastructure. Forecasting and the Carrington Mission concept (Priority: 4/5): She describes efforts to improve prediction of dangerous solar eruptions, including a proposed spacecraft at the fifth Lagrange point to observe the Sun-Earth line and provide earlier warnings. ESA Solar Orbiter and instrument design (Priority: 4/5): Green discusses work on Solar Orbiter, highlighting the engineering challenges of operating close to the Sun, including intense heat, thermal shielding, and instrument placement. Public policy and scientific advocacy (Priority: 4/5): The episode shows how scientific communication, media attention, and government coordination helped turn space weather into a recognized national security and economic issue.

Key Arguments: Green argues that the Sun’s magnetic field, not just gravity or fusion, is central to understanding dangerous eruptions because it stores and releases energy that drives coronal mass ejections. She emphasizes that space weather is not abstract: a Carrington-level event today could seriously disrupt satellites, communications, GPS, banking, and electricity transmission. She argues that forecasting is the holy grail because meaningful resilience depends on days of warning rather than hours, but current science cannot yet predict eruptions before they happen. She notes that government action improved when space weather was framed in terms of national security and economic impact, not only scientific curiosity. She explains that mission design and instrumentation are essential to progress, because better data from strategic vantage points will improve models and forecasts. She suggests that animals, like satellites, can be affected indirectly when geomagnetic disturbances alter the magnetic field they use for navigation.

Data Points: Sun-Earth travel time for light: 8 and a bit minutes - Time for photons to travel from the Sun’s surface to Earth after leaving the Sun Photon travel time inside the Sun: hundreds of thousands of years - Approximate time for photons to random-walk from the core to the surface More precise photon escape estimate: about 170,000 years - Estimate given in the audience Q&A for photon travel from core to surface Gravity at the Sun’s surface: 27 times Earth’s gravity - Explains the challenge of lifting coronal mass ejection material off the Sun Coronal mass ejection speed: a few hundred to a few thousand kilometres a second - Typical speeds discussed for CMEs Carrington event arrival time: about 17 hours - How quickly the 1859 superstorm reached Earth Satellite loss estimate: 10% of satellite fleet - Royal Academy of Engineering estimate for a Carrington-like event today Historical Carrington event year: 1859 - Referenced as the benchmark solar superstorm Likely recurrence interval: one in 80 to one in 100 years - Approximate probability framing for a Carrington-class event 2012 near-miss year: 2012 - Fast, strong CMEs occurred but were not Earth-directed Solar Orbiter closest approach temperature: about 500 degrees Celsius - Heat on the Sun-facing side of the spacecraft near perihelion Solar Orbiter travel time to orbit: about 3 years - Time needed for the mission to reach its solar orbit

Pivotal Quotes: "the sun is basically a nuclear bomb that's contained by the material overlying the core where the fusion process is happening" — Lucy Green: Her description of the Sun’s power and the physics that restrain it "I think that was the holy grail of space weather forecasting for me" — Lucy Green: She explains the goal of predicting coronal mass ejections before they happen "If the lights go out, the cascading failures that would then come from that would be significant" — Lucy Green: She is describing the consequences of a major solar storm hitting modern infrastructure

Implications: Space weather is a real infrastructure and economic risk, not just an astronomical curiosity. Better models, missions, and policy planning could reduce damage to satellites, grids, and navigation systems.