End-to-End Overview of Hazardous Radiation Len Fisk University of Michigan

Space radiation from energetic particles comes in three basic types: Galactic cosmic rays Small impulsive solar particle events Large solar energetic particle events

We know a great deal about galactic cosmic rays, e.g., time variations are due to solar activity. Impact of galactic cosmic rays is not a space physics problem but a biological and engineering problem. How much dosage should be allowed? How to shield?

1000 per year during solar maximum. Exciting physics because of unusual composition. Intensity sufficiently low, although events very numerous, to have impact on space operations. Impulsive Solar Energetic Particle Events

10-20 per year occur during solar maximum Can result in relativistic ions for days Particles arrive at Earth within minutes Can provide lethal dose of radiation to an exposed astronaut Large Solar Energetic Particle Events

Design Process 1. Define broad objectives & constraints 2. Estimate quantitative needs & requirements 3. Define alternative mission concepts 4. Define alternative mission architectures 5. Define system drivers for each alternative 6. Characterize mission concepts & architecture 7. Identify critical requirements 8. Evaluate mission utility 9. Define mission baseline concept 10. Define system requirements 11. Allocate (flow down) requirements to system elements

The Design of a CME Broad Objectives : –Convert magnetic energy of Sun into energetic particles. Constraints: –Obey the laws of physics. Need to quantify: –How much magnetic energy is available; how many energetic particles do we want to produce; what is the composition and energy ranges.

The Design of a CME Alternative Mission Concepts: –Models for the behavior of the magnetic field in the Sun; –Models for how active regions form; where do coronal loops come from; what are their properties; how do they evolve; –The role of magnetic reconnection and with what;

The Design of a CME Alternative Mission Concepts: –Models for the conditions through which CMEs evolve in the corona; –Models for the background magnetic field in the corona; –Models for how fast CMEs can propagate; how strong will the shock be;

The Design of a CME Alternative Mission Concepts : –Models for energetic particle acceleration; –Diffusive shock acceleration, which depends on the seed population and the injection mechanism; and on the configuration of the magnetic field; –Statistical acceleration which depends on the turbulence and how it is generated;

The Design of a CME Alternative Mission Concepts : –Models for how energetic particles propagate; –Is the turbulence that scatters the particles self-generated; is it confined to near the shock front? –And there are probably many more concepts that we might want to think about.

The Design of a CME Mission Architectures: –There are various ways in which the elements can be assembled into different architectures for a CME; –If they are good models and concepts they can be quantified; and each possible architecture evaluated for its critical requirements and specific utility.

Design of a CME Define a Baseline Concept and System Requirements: –We can evaluate these architectures and find one that works; satisfies all of the requirements, and choose it for the baseline; –There are system requirements for our baseline CME; which flow down to the requirements of each system element.

Design of a CME If we know the requirements for each system elements, we know what to measure. And from these measurements specific predictions will result as to when a CME will occur and what will be its specific consequences.

What Would Be Different? We do not lack for concepts of how the elements of our CME system work -- the release, evolution, acceleration, propagation. We lack an organized way to evaluate the validity and importance of these concepts in a large solar particle event.

What Would Be Different? In an aerospace design effort teams of people quantitatively consider each element. There is an evaluation process usually iterative by which the best mission elements and best mission architecture are chosen for the baseline. And under time constraints We currently rely on peer review and the formation of community consensus.

We need an organized evaluation process Each concept, each model needs to be evaluated quantitatively. There needs to be a measurable effect, which can be compared to observations, or evaluated based on the impact on the rest of the system. And on a timely basis. Somewhere there needs to be an evaluation team that considers each mission concept and architecture and decides on the baseline. The decision should not be by chance or with the hope of a consensus; but rather by design.