Washington DC (SPX) May 11, 2012 For the last few decades, spacescientists have generally accepted that the bubble of gas andmagnetic fields generated by the sun - known as the heliosphere -moves through space, creating three distinct boundary layers thatculminate in an outermost bow shock. This shock is similar to the sonic boom created ahead of asupersonic jet. Earth itself certainly has one of these bow shockson the sunward side of its magnetic environment, as do most otherplanets and many stars. A collection of new data from NASA'sInterstellar Boundary Explorer (IBEX), however, now indicate thatthe sun does not have a bow shock. In a paper appearing online in Science Express on May 10, 2012,scientists compile data from IBEX, NASA's twin Voyager spacecraft,and computer models to show that the heliosphere just isn't movingfast enough to create a bow shock in the tenuous and highlymagnetized region in our local part of the galaxy.
"IBEX gives a global view. It shows the whole of this region," saysEric Christian who is the mission scientist for IBEX at NASA'sGoddard Space Flight Center in Greenbelt, Md. and who was formerlythe program scientist for Voyager. "At the same time the Voyager spacecraft are actually there, insitu, measuring its environment at two locations.
The combinationof IBEX and Voyager gives you great science and now the new IBEXresults strongly indicate that there is no bow shock." Since the 1980s, the boundaries of the heliosphere have largelybeen assumed to be a series of three. The first is a fairlyspherical boundary called the termination shock - the point wherethe solar wind streaming from the sun slows down below supersonicspeeds. From there the wind continues more slowly until it collides withthe material in the rest of the galaxy and is pushed back,deflecting around the outskirts of the heliosphere, streaming backtoward the tail of the moving bubble. This second boundary iscalled the heliopause. The third boundary was thought to be the bowshock, formed as the heliosphere plowed its way through the localgalactic cloud the same way a supersonic jet pushes aside the airas it moves. Industrial Ultrasonic Humidifier
The two Voyager spacecraft have confirmed the existence of thefirst boundary, and have seen evidence for the second as they movetoward it. However, each Voyager spacecraft has seen differentthings on their respective trips - one moving in a more northerlydirection, one moving more to the south. They've encountereddifferent regions at different distances from the sun, suggestingthe very shape of the heliosphere is squashed and asymmetrical. Scientists believe this asymmetry is caused by the force anddirection of magnetic fields ramming into the heliosphere fromoutside, the same way a hand pushing on a balloon will force it outof shape. Wet Film Humidifier
This was the first clue that there's a strong magneticfield exerting pressure on the outskirts of the solar system. Independently, IBEX has seen a well-defined band, or ribbon, at theedge of the heliosphere, believed to be defined by this externalmagnetic field. Other studies from IBEX have helped quantify themagnitude of the magnetic field, showing that it is on the strongend of what was previously thought possible. "We've seen one after another signature of a very strong magneticfield in the galactic environment," says Nathan Schwadron, a spacescientist at the University of New Hampshire in Durham who is oneof the authors on the paper. "That magnetic field influences thestructure of the heliosphere and the boundaries themselves. China Desiccant Dehumidifier
Thatleads to a whole new paradigm." Along with increased evidence for a strong external magnetic field,IBEX has also provided a new measurement for the speed of theheliosphere itself with respect to the local cloud. "We recently analyzed two years worth of IBEX data, and they showedthat the speed of the heliosphere - with respect to the local cloudof material - is only 52,000 miles per hour, instead of thepreviously believed 59,000," says David McComas at the SouthwestResearch Institute in San Antonio, Texas, who is first author onthis paper and also the principal investigator for IBEX. "That might not seem like a huge difference, but it translates to aquarter less pressure exerted on the boundaries of the heliosphere.This means there's a very different interaction, a much weakerinteraction, than previously thought." In essence, it means that, like an airplane going too slowly toproduce a sonic boom, the heliosphere isn't moving fast enough tocreate a bow shock, given the density and pressures of the materialits moving through. The heliosphere's boundaries lie roughly 10 billion miles away fromEarth, but are nonetheless crucial for understanding our place inthe universe.
Indeed, the heliopause provides some protection forour solar system from the harsh, radiation environment surroundingit. By knowing the nature of these boundaries, scientists can startto better understand the propagation of particles that do haveenough energy and speed to make it into our environment. As scientists incorporate this substantive new understanding intotheir physical models, they will also be waiting for more evidencefrom both IBEX and the Voyagers, which they hope will continue tosend back observations for many years to come. "Imagine the point at which Voyager crosses the threshold of theheliopause and either does or does not see what IBEX ispredicting," says Schwadron. "There will be enormous opportunitiesfor scientific advancement.".
"IBEX gives a global view. It shows the whole of this region," saysEric Christian who is the mission scientist for IBEX at NASA'sGoddard Space Flight Center in Greenbelt, Md. and who was formerlythe program scientist for Voyager. "At the same time the Voyager spacecraft are actually there, insitu, measuring its environment at two locations.
The combinationof IBEX and Voyager gives you great science and now the new IBEXresults strongly indicate that there is no bow shock." Since the 1980s, the boundaries of the heliosphere have largelybeen assumed to be a series of three. The first is a fairlyspherical boundary called the termination shock - the point wherethe solar wind streaming from the sun slows down below supersonicspeeds. From there the wind continues more slowly until it collides withthe material in the rest of the galaxy and is pushed back,deflecting around the outskirts of the heliosphere, streaming backtoward the tail of the moving bubble. This second boundary iscalled the heliopause. The third boundary was thought to be the bowshock, formed as the heliosphere plowed its way through the localgalactic cloud the same way a supersonic jet pushes aside the airas it moves. Industrial Ultrasonic Humidifier
The two Voyager spacecraft have confirmed the existence of thefirst boundary, and have seen evidence for the second as they movetoward it. However, each Voyager spacecraft has seen differentthings on their respective trips - one moving in a more northerlydirection, one moving more to the south. They've encountereddifferent regions at different distances from the sun, suggestingthe very shape of the heliosphere is squashed and asymmetrical. Scientists believe this asymmetry is caused by the force anddirection of magnetic fields ramming into the heliosphere fromoutside, the same way a hand pushing on a balloon will force it outof shape. Wet Film Humidifier
This was the first clue that there's a strong magneticfield exerting pressure on the outskirts of the solar system. Independently, IBEX has seen a well-defined band, or ribbon, at theedge of the heliosphere, believed to be defined by this externalmagnetic field. Other studies from IBEX have helped quantify themagnitude of the magnetic field, showing that it is on the strongend of what was previously thought possible. "We've seen one after another signature of a very strong magneticfield in the galactic environment," says Nathan Schwadron, a spacescientist at the University of New Hampshire in Durham who is oneof the authors on the paper. "That magnetic field influences thestructure of the heliosphere and the boundaries themselves. China Desiccant Dehumidifier
Thatleads to a whole new paradigm." Along with increased evidence for a strong external magnetic field,IBEX has also provided a new measurement for the speed of theheliosphere itself with respect to the local cloud. "We recently analyzed two years worth of IBEX data, and they showedthat the speed of the heliosphere - with respect to the local cloudof material - is only 52,000 miles per hour, instead of thepreviously believed 59,000," says David McComas at the SouthwestResearch Institute in San Antonio, Texas, who is first author onthis paper and also the principal investigator for IBEX. "That might not seem like a huge difference, but it translates to aquarter less pressure exerted on the boundaries of the heliosphere.This means there's a very different interaction, a much weakerinteraction, than previously thought." In essence, it means that, like an airplane going too slowly toproduce a sonic boom, the heliosphere isn't moving fast enough tocreate a bow shock, given the density and pressures of the materialits moving through. The heliosphere's boundaries lie roughly 10 billion miles away fromEarth, but are nonetheless crucial for understanding our place inthe universe.
Indeed, the heliopause provides some protection forour solar system from the harsh, radiation environment surroundingit. By knowing the nature of these boundaries, scientists can startto better understand the propagation of particles that do haveenough energy and speed to make it into our environment. As scientists incorporate this substantive new understanding intotheir physical models, they will also be waiting for more evidencefrom both IBEX and the Voyagers, which they hope will continue tosend back observations for many years to come. "Imagine the point at which Voyager crosses the threshold of theheliopause and either does or does not see what IBEX ispredicting," says Schwadron. "There will be enormous opportunitiesfor scientific advancement.".