Space Weather: RBSP - Twin NASA probes around our Earth

Spectacular events on Mars are making most of the space headlines, but NASA is getting ready to launch an upcoming mission to explore the environment of our own planet Earth.

Twin Radiation Belt Storm Probes (RBSP) are due to lift off aboard a United Launch Alliance Atlas V rocket on August 23 from Cape Canaveral, Florida.

They were placed, in their nose cone, atop the rocket on August 10. 

The two satellites will travel in orbits that take them through two extreme and dynamic regions of space surrounding the Earth called the Van Allen Radiation Belt.

They will probe space weather, the direct effects of activity on the Sun, which can in extreme cases damage satellite electronics, GPS services and cause power grids to fail.

Barry Mauk, RBSP project scientist at the Johns Hopkins University, in Maryland, said: "The dramatic dynamics of Earth's radiation belts caused by space weather are highly unpredictable.

"One of the fundamental objectives of the RBSP mission is to use Earth's magnetosphere as a natural laboratory to understand generally how radiation is created and evolves throughout the universe. There are many mysteries that need to be resolved."

The radiation belts, named after their discoverer, James Van Allen, are two concentric, donut-shaped rings filled with high-energy particles that dance about, bounce and drift through the region.

Sometimes these particles shoot down to Earth's atmosphere, sometimes they escape into space.

The radiation belts swell and shrink over time, a change that is part of a much larger space weather system that is driven by solar activity as material from the Sun spreads through space.

NASA says that the RBSP probes, the second mission in NASA's Living With a Star program, will help scientists to understand this radiation zone better and to design spacecraft that can survive such environments better.

The spacecraft carrying out such research may eventually help scientists predict space weather before it hits the Earth's neighbourhood.

Follow the RBSP team on Twitter with #RBSP and on their account @RBstormProbes

The Earth's Magnetic Field Is Wonky

The solution to a long-standing puzzle, why magnetic north sits off the coast of Canada, rather than at the North Pole, may have been found in the strange, lopsided nature of Earth's inner core.

The inner core is a ball of solid iron about 760 miles (1,220 kilometers) wide.

It is surrounded by a liquid outer core (mostly iron and nickel), a rocky, viscous mantle layer and a thin, solid crust.

As the inner core cools, crystallizing iron releases impurities, sending lighter molten material into the liquid outer core.

This upwelling, combined with the Earth's rotation, drives convection, forcing the molten metal into whirling vortices.

These vortices stretch and twist magnetic field lines, creating Earth’s magnetic field. Currently, the center of the field, called an axis, emerges in the Arctic Ocean west of Ellesmere Island, about 300 miles (500 kilometers) from the geographic North Pole.

In the last decade, seismic waves from earthquakes revealed the inner core looks like a navel orange, bulging slightly more on its western half.

Geoscientists recently explainedthe asymmetry by proposing a convective loop: The inner core might be crystallizing on one half and melting on the other.

Peter Olson and Renaud Deguen, geophysicists at Johns Hopkins University, set out to test this theory, called translational instability.

They ran numerical models simulating the forces that generate Earth’s magnetic field, and included a lopsided inner core.

Olson and Deguen found that adding inner-core asymmetry shifted magnetic north away from the center of the Earth, into the cooling hemisphere. Convection was stronger there, as was the magnetic field.

"The lopsided growth of the inner core makes convection in the outer core a little bit lopsided, and that then induces the geomagnetic field to have this lopsided or eccentric character too," Olson stated.

Olson and Deguen's research was detailed online July 1 in the journal Nature Geoscience.

Geophysicist Bruce Buffett said Olson and Deguen’s research is intriguing, but there are still questions about the underlying theory. "It's an interesting result, but we don't know for sure the inner core is translating.

The model does a good job at explaining some but not all of the features of the inner core," said Buffett, a professor at the University of California, Berkeley, who was not involved with the research.

Olson points out that his numerical model offers a real-world proof of the theory. Magnetic particles trapped and aligned in rocks reveal that the magnetic north pole wandered around the Western Hemisphere over the past 10,000 years, and circled the Eastern Hemisphere before that — a result mirrored by the numerical test.

Gathering a longer, more detailed record of the magnetic field's behavior, Olson said, could reveal whether the inner core acts as researchers predict.

"The key question for interesting ideas like translational instability is, 'Can we test it?'" Olson said. "What we're doing is proposing a test, and we think it's a good test because people can go out and look for eccentricity in the rock record and that will either confirm or shoot down this idea."

Electric Moon Jolts the Solar Wind

With the moon as the most prominent object in the night sky and a major source of an invisible pull that creates ocean tides, many ancient cultures thought it could also affect our health or state of mind – the word “lunacy” has its origin in this belief.

Now, a powerful combination of spacecraft and computer simulations is revealing that the moon does indeed have a far-reaching, invisible influence – not on us, but on the Sun, or more specifically, the solar wind.

The solar wind is a thin stream of electrically conducting gas called plasma that’s constantly blown off the surface of the Sun in all directions at around a million miles per hour.

When a particularly fast, dense or turbulent solar wind strikes Earth’s magnetic field, it can generate magnetic and radiation storms that are capable of disrupting satellites, power grids, and communication systems.

The magnetic “bubble” surrounding Earth also pushes back on the solar wind, creating a bow shock tens of thousands of miles across over the day side of Earth where the solar wind slams into the magnetic field and abruptly slows from supersonic to subsonic speed.

Unlike Earth, the moon is not surrounded by a global magnetic field. “It was thought that the solar wind crashes into the lunar surface without any warning or ‘push back’ on the solar wind,” says Dr. Andrew Poppe of the University of California, Berkeley.

Recently, however, an international fleet of lunar-orbiting spacecraft has detected signs of the moon’s presence “upstream” in the solar wind. “We’ve seen electron beams and ion fountains over the moon’s day side,” says Dr. Jasper Halekas, also of the University of California, Berkeley.

These phenomena have been seen as far as 10,000 kilometers (6,214 miles) above the moon and generate a kind of turbulence in the solar wind ahead of the moon, causing subtle changes in the solar wind’s direction and density.

The electron beams were first seen by NASA’s Lunar Prospector mission, while the Japanese Kaguya mission, the Chinese Chang’e mission, and the Indian Chandrayaan mission all saw ion plumes at low altitudes.

NASA’s ARTEMIS mission has now also seen both the electron beams and the ion plumes, plus newly identified electromagnetic and electrostatic waves in the plasma ahead of the moon, at much greater distances from the moon.

“With ARTEMIS, we can see the plasma ring and wiggle a bit, surprisingly far away from the moon,” says Halekas. ARTEMIS stands for “Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon’s Interaction with the Sun”.

“An upstream turbulent region called the ‘foreshock’ has long been known to exist ahead of the Earth’s bow shock, but the discovery of a similar turbulent layer at the moon is a surprise,” said Dr. William Farrell of NASA’s Goddard Space Flight Center in Greenbelt, Md. Farrell is lead of the NASA Lunar Science Institute’s Dynamic Response of the Environment At the Moon (DREAM) lunar science center, which contributed to the research.

Computer simulations help explain these observations by showing that a complex electric field near the lunar surface is generated by sunlight and the flow of the solar wind.

The simulation reveals this electric field can generate electron beams by accelerating electrons blasted from surface material by solar ultraviolet light.

Also, related simulations show that when ions in the solar wind collide with ancient, “fossil” magnetic fields in certain areas on the lunar surface, they are reflected back into space in a diffuse, fountain-shaped pattern.

These ions are mostly the positively charged ions (protons) of hydrogen atoms, the most common element in the solar wind.