New data from a solar-orbiting probe has found the sun's winds are less blustery than they used to be, and may provide new insights into earth's nearest star.

Data from the Ulysses spacecraft show the solar wind, a steady stream of charged sub-atomic particles emitted by the sun and blowing at 1.6 million kilometres per hour, has dwindled to its lowest level in at least 50 years, reducing its strength as a shield against potentially harmful galactic cosmic radiation.

The solar wind inflates a massive protective bubble, called the heliosphere, around the solar system.

Measurements show the wind's pressure has dropped 20% since the mid-1990s. At the same time, the electron temperature of the solar wind has declined 13%.