Stars are not inanimate luminous structures in the night sky. Most stars generate winds and move through the interstellar medium that surrounds them. This movement creates a cocoon formed by the deflection of these winds that envelops and protects the stars. We call these ‘cocoons’ astrospheres.
The Sun has its own cocoon, the heliosphere. The heliosphere is an immense shield that protects the solar system from harsh, galactic radiation. When Voyager 1 (V1) crossed the heliopause (HP), it discovered that the heliosphere shields 75% of galactic cosmic rays (GCRs) from Earth. The radiation that enters the heliosphere affects life on Earth as well as human space exploration. GCRs are the dominant source of radiation and principal hazard affecting space missions within our solar system. Current global heliosphere models do not successfully predict the radiation environment at all locations or under different solar conditions. To understand the heliosphere’s shielding properties, we need to understand its structure and large-scale dynamics. Fundamental features remain unknown. Prof. Opher’s main thrust in the last 20 years is to fill in the critical knowledge gaps. She is currently the PI of Solar wind with Hydrogen Ion charge Exchange and Large-Scale Dynamics (SHIELD) DRIVE Center funded by NASA. The vision of SHIELD DRIVE Science Center is to understand the nature and structure of the heliosphere.
To realize our vision and create a new model for the heliosphere, SHIELD will enlist experts on observations, kinetic physics and MHD physics, and high energy particle transport and acceleration physics, and will facilitate their interaction in a Center environment. SHIELD will reach to the broader community for participation. Through four integrated research thrusts leading to the global model, SHIELD will: (1) determine the global nature of the heliosphere; (2) determine how pickup ions evolve from ‘cradle to grave’ and affect heliospheric processes; (3) establish how the heliosphere interacts with and influences the LISM; and (4) establish how cosmic rays are filtered by and transported through the heliosphere.
Review of Prof. Opher on heliosphere processes:
- Solar wind with Hydrogen Ion charge Exchange and Large-Scale Dynamics (SHIELD) DRIVE Science Center, Opher, M. et al. 2022
- M. Opher (2012) The Heliosheath: The Ultimate Solar System Frontier, Astronomical Review, 7:1, 68-78, DOI: 10.1080/21672857.2012.11519697