With more than $1 million in NASA funding, Zhang is researching cosmic and energetic solar radiation, seeking how the two space weather components affect human beings, both as space travelers and as the end-user of satellite technology.
"America wants to send humans to Mars and to colonize the moon," said Zhang. "But the natural radiation that exists in space is a big concern since it will prove toxic over time and can reach lethal amounts a few times a decade."
In the vacuum of space, energetic particle radiation from the galaxy and from our sun varies in intensity and energy. This variation is in concert with the 11-year solar cycle. Zhang's research is determining how and why the solar cycle changes the energetic particle fluxes in our geospace environment and throughout the solar system. For Zhang and his fellow space physicists, this research provides clues into the structure of our galaxy, the origin of all galaxies, as well as the structure and dynamics of our sun. For our astronauts, this knowledge may one day prove life saving.
"We know that the sun has an 11-year cycle from active to dormant; these are the solar seasons" Zhang said. "When the sun is most active, a burst of solar radiation could kill an unprotected astronaut very quickly or cripple a spacecraft. In a radiation burst, the effect on the body would be much like the radiation from a nearby nuclear explosion."
NASA's interplanetary travel itineraries, however, cannot be limited to the only periods when the sun is dormant. "Cosmic rays coming from outside the solar system are high-energy charged particles, many times more damaging than an X-ray. These particles are most likely produced by supernovae in the galaxy," Zhang said. "These rays can penetrate the human body easily and mutate or kill DNA in the cells along their paths. The mutated DNA can lead to cancer and other alteration of the cellular structures."
The catch-22 is that an active sun produces a more chaotic solar wind, reducing the intensity of cosmic rays and thus protecting astronauts. When the sun is dormant, cosmic radiation is much higher. "For the astronaut, it really is a case of picking your poison," Zhang said. "There is either a period of higher intensity cosmic rays around solar minimum or a high probability of large radiation burst during solar maximum.
NASA was aware of the radiation dangers when it first planned the original missions to the moon. At the time, however, they were less concerned about cosmic radiation because the missions were short. Scientists are just now learning how dangerous cosmic rays are to people and satellites.
Zhang's research is also helping scientists understand how to predict space weather, particularly when and where to expect large solar bursts.
"By forecasting space weather, we can protect newer satellites, which have smaller electronics that are more susceptible to high-energy radiation. We cam also protect people on Earth by advising airlines to divert flights away from the polar caps," Zhang said. While Earth's magnetic field protects us from both cosmic and solar radiation, penetration is easiest at the polar caps.
As Zhang continues his space weather research, he and his fellow space physicists at Florida Tech's Geospace Physics Laboratory (GPL), Drs. Hamid Rassoul, Joseph Dwyer, Brian Ball, and Gang Qin, are unlocking secrets to the universe that were beyond the scope of speculation a few decades ago.
"We know that solar activity modulates cosmic rays, even to the far boundary of the solar system," Rassoul said. "Indeed, using recent observations from NASA's old work horses, the Voyager 1 and 2 spacecraft, Zhang and Ball found that the intensity of cosmic rays at ~90 AU is still strongly modulated by solar activity. What we are trying to understand is how these changes occur, and what they mean for us and our space investments."