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NASA announced Monday that after 35 years of exploration, its Voyager 1 spacecraft has entered a new, unanticipated region of space near the edge of the solar system--a "magnetic highway" where charged particles take the "exit ramp" to interstellar space.
The region connects the sun's magnetic field lines to interstellar magnetic field lines, allowing "lower-energy charged particles that originate from inside our heliosphere... to zoom out, and higher-energy particles from outside to stream in," according to a written statement issued by NASA partner Johns Hopkins Applied Physics Lab.
The heliosphere is the "immense magnetic bubble containing our solar system, solar wind, and the entire solar magnetic field," according to NASA.
Scientists say they believe this is the final region Voyager 1 has to cross before reaching interstellar space.
Voyager 1's instruments showed a five-fold increase in high-energy charged particles, accompanied by a 1,000-fold drop in low-energy particles, NASA officials said.
These data would be consistent with Voyager 1's exit from the heliosphere, but Voyager 1's magnetic-field reading instrument indicates otherwise.
It shows an East-West magnetic field orientation, indicative of the sun's influence. The magnetic field in interstellar space, influenced by winds from explosions of supernovae, is thought to have a roughly North-South orientation, according to NASA astrophysicist Leonard Burlaga.
Voyager 1 may remain within the heliopause for another two to three years, but it's hard to anticipate how long it will be until the probe leaves the solar system, NASA scientists said. The heliopause is where the interstellar medium and solar wind pressures balance, the outer boundary of the solar system.
Launched in 1977 to explore the outer solar system, Voyager 1 and and its twin, Voyager 2, are the longest-serving spacecraft. Voyager 1 is currently 122 AU from Earth, and Voyager 2 is about 100 AU away. One AU, or astronomical unit, is equivalent to the distance from Earth to the sun.
http://www.huffingtonpost.com/2012/12/03/voyager-1-new-region-space-magnetic-highway-nasa_n_2231827.html?ncid=edlinkusaolp00000003
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Plasma Flow Near Voyager 1
This artist's concept shows plasma flows around NASA's Voyager 1 spacecraft as it approaches interstellar space. Voyager 1's low-energy charged particle instrument detects the speed of the wind of plasma, or hot ionized gas, streaming off the sun. It detected the slowing of this wind, also known as the solar wind, to zero outward velocity in a region called the stagnation region. Scientists had expected that the solar wind would turn the corner as it felt the pressure of the interstellar magnetic field and the interstellar wind flow. But that has not happened so far, so it is not clear what should be expected once the spacecraft reaches interstellar space.
Voyager 1 crossed a shockwave known as the termination shock in 2004. At the termination shock, the solar wind slows down abruptly from supersonic speeds. The heliopause is the boundary between the bubble of charged particles around our sun - known as the heliosphere - and interstellar space. Its location is still a mystery
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The Sun's Southern Wind Flows Northward
This artist's concept shows how NASA's Voyager 1 spacecraft is bathed in solar wind from the southern hemisphere flowing northward. This phenomenon creates a layer just inside the outer boundary of the heliosphere, the giant bubble of solar ions surrounding the sun. If the outside pressure were symmetrical, the streams from the sun's northern hemisphere above the plane of the planets would all turn northward and the streams from the southern hemisphere would all turn southward.
However, the interstellar magnetic field presses more strongly on the boundary in the southern hemisphere, forcing some of the solar wind from the south that otherwise would have gone southward to be deflected northward to where Voyager 1 is. On July 21, 2012, the magnetometer instrument indicated that Voyager 1 had entered a region where the wind is from the southern hemisphere. Scientists interpret this to mean that the spacecraft is in the final region before reaching interstellar space because the southern wind streams have to flow out and around all of the northern wind to reach Voyager 1's location.
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Charged Particle Data from Voyager 1's Low-Energy Charged Particle Instrument
This graphic from NASA's Voyager mission shows measurements of different populations of charged particles by Voyager 1's low-energy charged particle instrument (LECP). The upper panel shows the instrument's detections of cosmic rays from interstellar space for the past several months in blue. (These cosmic ray particles are at somewhat higher energies than the cosmic ray subsystem instrument.) The top graphic illustrates how this population of cosmic ray particles reached a new high level starting on Aug. 25, 2012.
The lower panel shows two populations of protons in the heliosheath, which is the outer layer of the bubble of charged particles surrounding the sun. Protons of these energies mostly originate from our sun and are shown in pink and magenta. These low speed protons (moving between about 7,000 miles per second and 2,800 miles per second) have virtually disappeared. The LECP instrument hasn't detected them for several weeks, meaning they have dropped by at least a factor of 1,000. Anomalous cosmic rays (gray), which are somewhat higher energy particles from inside the heliosphere, have also decreased.
The dashed lines indicate when Voyager 1 was in a new region scientists are calling the "magnetic highway." This new region lapped and receded from Voyager 1 like an ocean wave several times between July and August. The dashed vertical lines indicate when Voyager 1 moved into this new region. Voyager 1 entered the region permanently on Aug. 25, 2012.
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