Tearing into each other: When the magnetic fields of the Sun and Earth align, Earth's protective bubble can be breached, letting in solar storm particles.
Credit: NASA
SAN FRANCISCO: Scientists have found two holes in Earth's protective magnetic shield, letting in particles from solar storms that could wreak havoc on satellites and electrical equipment.
The holes are a startling discovery that change the way scientists think about Earth's invisible magnetic field, said Jimmy Raeder, a U.S. space physicist from the University of New Hampshire in Durham.
Raeder was part of the team who presented the discovery at yesterday's meeting of the American Geophysical Union in San Francisco, California.
Leaky shield
Scientists have long known the magnetic field surrounding our planet, called the magnetosphere, plays a crucial role in protecting us from particles blasted towards Earth by the Sun's solar wind.
Though most of these energetic particles are deflected by the magnetosphere, some do manage to breach the shield.
Previously it was thought the solar particles could enter more easily when the Sun's magnetic field was pointing in the opposite direction of Earth's field. When the two fields were pointing in the same direction, however, they were believed to reinforce each other, acting as a barrier to lock most of the particles out.
Backwards thinking
But that theory turns out to be backward, said Marit Oieroset, a physicist at the University of California, Berkeley, also part of the research team. In fact, Oieroset said, 20 times more solar particles enter when the fields of the Sun and Earth are aligned.
The discovery was made when a fleet of five NASA satellites, known as THEMIS (Time History of Events and Macroscale Interactions during Substorms), traveled through a thick layer of solar particles inside the magnetosphere, said Oieroset.
The size of the fleet meant measurements could be made spanning the entire layer of particles, almost 6,500 km thick and rapidly growing, revealing the true extent of the magnetosphere's 'leak'.
The origins of the leak have been pinpointed to two holes that frequently develop on the side of the magnetosphere facing the Sun - one over the Northern Hemisphere, one over the Southern.
The locations are such because, while the magnetic fields of the Sun and Earth may be aligned at equator-level, at higher latitudes they end up pointing in opposite directions, resulting in the magnetosphere tearing.
In order to wreak havoc, many solar particles must breach Earth's magnetic shield and become energised by the magnetic solar wind energy - acting like fuel for new solar storms.
High energy havoc
If energy from the solar magnetic field breaches Earth's magnetic defenses before many particles are in the system, the effect of that energy is relatively benign. "One can compare this with a gas stove," Raeder said. "If you light the stove just as you open the gas valve nothing dramatic will happen. But if you open the valve for a while and then light the stove: boom!"
But many particles becoming energised magnify the force of incoming solar storms, and therefore have the potential to play havoc, Raeder added.
Magnetic storms, for example, could overload power lines and cause widespread blackouts, while radiation storms could threaten high-orbit crafts.
Storms on the horizon
The discovery of the magnetosphere leak may help predict the severity of future solar storms and the degree to which Earth will be affected, as we now move into the next 11-year solar cycle (in which solar storm activity waxes and wanes).
"With every new solar cycle, the direction of the solar magnetic field changes," Raeder said. In the last solar cycle, the pattern was like lighting the match before turning on the gas valve. This time, however, the reverse will happen. Thus, the researchers said, we could be in for stronger electromagnetic storms during cycle, which reaches its peak around 2012.
