WASHINGTON (AFP) - Four identical satellites which will study the interactions between solar winds and the Earth's magnetic fields blasted off into space on Thursday to begin a two-year study of the phenomenon, US space agency Nasa said.

The Delta V rocket of the United Launch Alliance lifted off from its launchpad from Cape Canaveral in Florida at 10.44pm local time as planned at the beginning a 30-minute window of opportunity.

The quartet of spacecraft weighing 1.2 tonnes known as "Magnetospheric Multiscale" or MMS, will fly in a pyramid formation.

They will obtain three-dimensional images and collect data as they monitor collisions from the Earth's magnetosphere and solar particles arriving at high speed and forming their own magnetic field about 96,560km from Earth.

Scientists hope to gain a greater understanding of the phenomenon, known as magnetic reconnection.

"Magnetic reconnection is one of the most important drivers of space weather events," said Jeff Newmark, interim director of the Heliophysics Division at Nasa Headquarters in Washington.

"Space weather events can affect modern technological systems such as communications networks, GPS navigation, and electrical power grids."

The US$1.1 billion (S$1.5 billion) mission is expected to last last two years.