Turbulent Sea of Magnetic Bubbles Found At the Edge of Our Solar System

NASA will host a media teleconference at 1 p.m. EDT on Thursday, June 9, to discuss a new computer model that shows the edge of our solar system is not smooth, but filled with a turbulent sea of magnetic bubbles.

Based on Voyager data, the finding suggests we need to revise our picture of this previously unexplored region so critical for understanding how cosmic rays are created and reach near-Earth space. Galactic cosmic rays are of concern for human space travel, in particular during the quiet periods called the solar minimum.

This still shows the locations of Voyagers 1 and 2. Voyager 1 is traveling a lot and has crossed into the heliosheath, the region where interstellar gas and solar wind start to mix. http://www.nasa.gov/mov/52704main_heliopause.mov

Credit: NASA/Walt Feimer

Starting with a view of our Milky Way galaxy, the orange gas in the animation represents the interstellar medium. The bow shock is created because the heliosphere is moving through like a boat through the water, crashing through the interstellar gases. The bow shock in front of the moving heliosphere is similar to the one observed by the Hubble Space Telescope. Click for animation. 

Credit: NASA/Walt Feimer

We don't know the exact location of the termination shock and changes in the solar wind cause it to expand, contract, and ripple like a plate underwater. Water spreads out over the plate in a relatively smooth flow but has a rough edge where the water slows down abruptly and piles up. The edge is like the termination shock, and as the water flow changes, the shape and size of the rough edge change.

Credit: NASA/ESA

The termination shock is where the solar wind, a thin stream of electrically charged gas blowing continuously outward from the Sun, is slowed by pressure from gas between the stars. At the termination shock, the solar wind slows abruptly from its average speed of 300 to 700 km per second (700,000 - 1,500,000 miles per hour) and becomes denser and hotter.

 The Hubble Space Telescope imaged this view in February 1995. The arcing, graceful structure is actually a bow shock about half a light-year across, created from the wind from the star L.L. Orionis colliding with the Orion Nebula flow. For more information on this image, see HubbleSite. Click on the image for a very large version. 

Credit: NASA, The Hubble Heritage Team (STScI/AURA)

The strongest evidence that Voyager 1 has passed through the termination shock into the slower, denser wind beyond is its measurement of an increase in the strength of the magnetic field carried by the solar wind and the inferred decrease in its speed. Physically, this must happen whenever the solar wind slows down, as it does at the termination shock.

Consider a highway with moderate traffic. If something makes the drivers slow down, say a puddle of water, the cars pile up - their density increases. In the same way, the density (intensity) of the magnetic field carried by the solar wind will increase if the solar wind slows down. In December 2004, Voyager 1 observed the magnetic field strength increasing by a factor of two and a half, as expected when the solar wind slows down. The magnetic field has remained at these high levels from December until now. An increase in the magnetic field intensity of about 1.7 times was seen at the time of the event announced in 2003.

The teleconference panelists are:

-- Arik Posner, Voyager program scientist, Heliophysics Division, Science Mission Directorate, NASA Headquarters, Washington
-- Merav Opher, assistant professor, Astronomy Department, Boston University
-- James F. Drake, professor of physics, University of Maryland, College Park
-- Edward C. Stone, Voyager project scientist, professor of physics, Caltech, Pasadena, Calif.
-- Eugene Parker, professor emeritus, Department of Physics, University of Chicago

* A link to the streaming audio will appear here before the event.