Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Voyager 1 Cruising on a ‘Magnetic Highway’

05.12.2012
Johns Hopkins Applied Physics Laboratory Scientists
See Charged Particles Taking ‘Exit Ramp’ to Interstellar Space

NASA’s Voyager 1 spacecraft has encountered a new region on the outskirts of our solar system that appears to be a magnetic highway for charged particles. Scientists believe this is the final region Voyager has to cross before reaching interstellar space, or the space between stars.

Scientists call this region the magnetic highway because our sun's magnetic field lines are connected to interstellar magnetic field lines. The connection has allowed lower-energy charged particles that originate from inside our heliosphere – the bubble of charged particles the sun blows around itself – to zoom out, and higher-energy particles from outside to stream in.

Before entering this region, the charged particles bounced around in all directions, as if trapped on local roads inside the heliosphere. Thinking the particles might be colliding against the gaseous boundary of the solar system, scientists operating Voyager’s low-energy charged particle detector wondered if the spacecraft had reached the last stop before – or even crossed into – interstellar space. Data indicating that the direction of the magnetic field lines has not changed, however, leads the Voyager team to infer that this region is still inside the solar bubble.

The new results will be described today at the American Geophysical Union meeting in San Francisco.

"If we were judging by the charged-particle data alone, I would have thought we were outside the heliosphere," says Stamatios Krimigis, principal investigator of the Low-Energy Charged Particle (LECP) instrument, based at the Johns Hopkins University Applied Physics Laboratory in Laurel, Md. "In fact, our instrument has seen the low-energy particles taking the exit ramp toward interstellar space. But we need to look at what all the instruments are telling us and only time will tell whether our interpretations about this frontier are correct. One thing is certain – none of the theoretical models predicted any of Voyager’s observations over the past 10 years, so there is no guidance on what to expect."

Since December 2004, when Voyager 1 crossed a shockwave known as the Termination Shock, the spacecraft has been exploring the heliosphere's outer layer, called the heliosheath. Here, the stream of charged particles from the sun – known as the solar wind – abruptly slowed down from supersonic speeds and became turbulent. Voyager 1's environment was consistent for about five and a half years, but then the spacecraft detected that the outward speed of the solar wind slowed to zero. The intensity of the magnetic field also began to increase.

“The solar wind measurements speak to the unique abilities of the LECP detector, designed at APL nearly four decades ago," Krimigis says. “Where a device with no moving parts would have been safer – lessening the chance a part would break in space – our team took the risk to include a stepper motor that rotates the instrument 45 degrees every 192 seconds, allowing it to gather data in all directions and pick up something as dynamic as the solar wind. A device designed to work for 500,000 ‘steps’ and four years has been working for 35 years and well past 6 million steps.”

In fact, for the past several months, the entire Voyager spacecraft was commanded to rotate periodically by 70 degrees so the LECP instrument could measure the solar wind flow in the up-down direction, or north-south according to the ecliptic plane on which the planets orbit the sun. In theory, with the flow in the ecliptic plane having dropped to zero, the plasma should have been headed north at Voyager’s position. But the measurements, reported Sept. 6 in the journal Nature, showed that the flow was consistent with zero. “This was a real surprise,” says LECP Co-investigator Rob Decker, of the Applied Physics Laboratory (APL), “because most models were expecting the northward speed to be at least as high as 25 kilometers per second.”

A New Region

Around May 14, LECP also measured a sudden, 5-percent increase in cosmic rays – high-energy particles coming in from the galaxy – followed by a similar increase on July 28. This second increase was accompanied by a decrease (by a factor of 5) in the low-energy particles, but this only lasted for four days. A few days later the same up-and-down exchange occurred, but on Aug. 25 the instrument recorded an even larger increase in cosmic rays – bringing the total increase since the end of March to about 30 percent.

The intensity of particles that have an even lower energy than the cosmic rays dropped by more than a factor of 1,000 below that observed since Voyager 1 first entered the heliosheath. LECP scientists agree with their colleagues that Voyager has entered a new region, but perhaps is not yet out of the heliosphere. Decker says that the distribution of lower-energy particles suggests a magnetic field direction of about 110 degrees to the direction pointing away from the sun, but in the ecliptic plane, not drastically different than the direction of about 90 degrees inside the heliosphere.

"We believe this is the last leg of our journey to interstellar space,” says Edward Stone, Voyager project scientist based at the California Institute of Technology, Pasadena. “Our best guess is that it's likely just a few months up to a couple years away. The new region isn't what we expected, but we've come to expect the unexpected from Voyager."

Voyager 1 and 2 were launched 16 days apart in 1977 and, between them, visited Jupiter, Saturn, Uranus and Neptune. Voyager 1 is the most distant manmade object, about 11 billion miles (18.5 billion kilometers) away from the sun. Voyager 2 is about 9 billion miles (15 billion kilometers) away from the sun. While Voyager 2 has seen some gradual changes in the charged particles, they are very different from those seen by Voyager 1. Scientists do not think Voyager 2 has reached the magnetic freeway.

The Voyager spacecraft were built and are operated by the Jet Propulsion Laboratory, a division of the California Institute of Technology. The LECP instrument was designed and built at the Johns Hopkins University Applied Physics Laboratory with NASA funding. The Voyager missions are a part of the NASA Heliophysics System Observatory, sponsored by the Heliophysics Division of the Science Mission Directorate in Washington. For more information about the Voyager spacecraft, visit: http://www.nasa.gov/voyager. For more on the Low-Energy Charged Particle detector, visit: http://sd-www.jhuapl.edu/VOYAGER/index.html.

The Applied Physics Laboratory, a not-for-profit division of The Johns Hopkins University, meets critical national challenges through the innovative application of science and technology. For more information, visit www.jhuapl.edu.

Michael Buckley | Newswise
Further information:
http://www.nasa.gov/voyager

More articles from Physics and Astronomy:

nachricht Telescopes team up to find distant Uranus-sized planet through microlensing
31.07.2015 | NASA/Goddard Space Flight Center

nachricht California 'rain debt' equal to average full year of precipitation
31.07.2015 | NASA/Goddard Space Flight Center

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Quantum Matter Stuck in Unrest

Using ultracold atoms trapped in light crystals, scientists from the MPQ, LMU, and the Weizmann Institute observe a novel state of matter that never thermalizes.

What happens if one mixes cold and hot water? After some initial dynamics, one is left with lukewarm water—the system has thermalized to a new thermal...

Im Focus: On the crest of the wave: Electronics on a time scale shorter than a cycle of light

Physicists from Regensburg and Marburg, Germany have succeeded in taking a slow-motion movie of speeding electrons in a solid driven by a strong light wave. In the process, they have unraveled a novel quantum phenomenon, which will be reported in the forthcoming edition of Nature.

The advent of ever faster electronics featuring clock rates up to the multiple-gigahertz range has revolutionized our day-to-day life. Researchers and...

Im Focus: Superfast fluorescence sets new speed record

Plasmonic device has speed and efficiency to serve optical computers

Researchers have developed an ultrafast light-emitting device that can flip on and off 90 billion times a second and could form the basis of optical computing.

Im Focus: Unlocking the rice immune system

Joint BioEnergy Institute study identifies bacterial protein that is key to protecting rice against bacterial blight

A bacterial signal that when recognized by rice plants enables the plants to resist a devastating blight disease has been identified by a multi-national team...

Im Focus: Smarter window materials can control light and energy

Researchers in the Cockrell School of Engineering at The University of Texas at Austin are one step closer to delivering smart windows with a new level of energy efficiency, engineering materials that allow windows to reveal light without transferring heat and, conversely, to block light while allowing heat transmission, as described in two new research papers.

By allowing indoor occupants to more precisely control the energy and sunlight passing through a window, the new materials could significantly reduce costs for...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

3rd Euro Bio-inspired - International Conference and Exhibition on Bio-inspired Materials

23.07.2015 | Event News

Clash of Realities – International Conference on the Art, Technology and Theory of Digital Games

10.07.2015 | Event News

World Conference on Regenerative Medicine in Leipzig: Last chance to submit abstracts until 2 July

25.06.2015 | Event News

 
Latest News

Tool making and additive technology exhibition: Fraunhofer IPT at Formnext

31.07.2015 | Trade Fair News

First Siemens-built Thameslink train arrives in London

31.07.2015 | Transportation and Logistics

California 'rain debt' equal to average full year of precipitation

31.07.2015 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>