Discoveries from the IBEX satellite show we still don't know quite a few things about the heliosphere and solar system

From the University of Chicago

Satellite reveals surprising cosmic ‘weather’ at edge of solar system

		IMAGE: Image from one of the IBEX papers published in the Oct. 16, 2009, issue of Science showing a map of the ribbon of energetic neutral atoms (in green and yellow)…

The first solar system energetic particle maps show an unexpected landmark occurring at the outer edge of the solar wind bubble surrounding the solar system. Scientists published these maps, based mostly on data collected from NASA’s Interstellar Boundary Explorer satellite, in the Oct. 15 issue of Science Express, the advance online version of the journal Science.

“Nature is full of surprises, and IBEX has been lucky to discover one of those surprises,” said Priscilla Frisch, a senior scientist in astronomy & astrophysics at the University of Chicago. “The sky maps are dominated by a giant ribbon of energetic neutral atoms extending throughout the sky in an arc that is 300 degrees long.” Energetic neutral atoms form when hot solar wind ions (charged particles) steal electrons from cool interstellar neutral atoms.

IBEX was launched Oct. 19, 2008, to produce the first all-sky maps of the heliosphere, which reaches far beyond the solar system’s most distant planets. Extending more than 100 times farther than the distance from Earth to the sun, the heliosphere marks the region of outer space subjected to the sun’s particle emissions.

The new maps show how high-speed cosmic particle streams collide and mix at the edge of the heliosphere, said Frisch, who co-authored three of a set of IBEX articles appearing in this week’s Science Express. The outgoing solar wind blows at 900,000 miles an hour, crashing into a 60,000-mile-an-hour “breeze” of incoming interstellar gas.

Revealed in the IBEX data, but not predicted in the theoretical heliosphere simulations of three different research groups, was the ribbon itself, formed where the direction of the interstellar magnetic field draping over the heliosphere is perpendicular to the viewpoint of the sun.

		IMAGE: Priscilla Frisch, Senior Scientist in Astronomy & Astrophysics, and member of the science team, Interstellar Boundary Explorer. Collaborating with former UChicago astronomer Thomas F. Adams, she made the first spectrum…

Energetic protons create forces as they move through the magnetic field, and when the protons are bathed in interstellar neutrals, they produce energetic neutral atoms. “We’re still trying to understand this unexpected structure, and we believe that the interstellar magnetic forces are associated with the enhanced ENA production at the ribbon,” Frisch said.

IBEX shows that energetic neutral atoms are produced toward the north pole of the ecliptic (the plane traced by the orbit of the planets around the sun), as well as toward the heliosphere tail pointed toward the constellations of Taurus and Orion. “The particle energies change between the poles and tail, but surprisingly not in the ribbon compared to adjacent locations,” Frisch said.

IBEX is the latest in NASA’s series of low-cost, rapidly developed Small Explorers space missions. Southwest Research Institute in San Antonio, Texas, leads and developed the mission with a team of national and international partners. NASA’s Goddard Space Flight Center in Greenbelt, Md., manages the Explorers Program for NASA’s Science Mission Directorate in Washington.

Citations: N. A. Schwadron, M. Bzowski, G. B. Crew, M. Gruntman, H. Fahr, H. Fichtner, P. C. Frisch, H. O. Funsten, S. Fuselier, J. Heerikhuisen, V. Izmodenov, H. Kucharek, M. Lee, G. Livadiotis, D. J. McComas, E. Moebius, T. Moore, J. Mukherjee, N.V. Pogorelov, C. Prested, D. Reisenfeld, E. Roelof, G.P. Zank, “Comparison of Interstellar Boundary Explorer Observations with 3-D Global Heliospheric Models,” Science Express, Oct. 15, 2009.

H.O. Funsten, F. Allegrini, G.B. Crew, R. DeMajistre, P.C. Frisch, S.A. Fuselier, M. Gruntman, P. Janzen, D.J. McComas, E. Möbius, B. Randol, D.B. Reisenfeld, E.C. Roelof, N.A. Schwadron, “Structures and Spectral Variations of the Outer Heliosphere in IBEX Energetic Neutral Atom Maps,” Science Express, Oct. 15, 2009.

D.J. McComas, F. Allegrini1, P. Bochsler, M. Bzowski, E.R. Christian, G.B.Crew, R. DeMajistre, H. Fahr, H. Fichtner, P.C. Frisch, H.O. Funsten, S. A. Fuselier, G. Gloeckler, M. Gruntman, J. Heerikhuisen, V. Izmodenov, P.J anzen, P. Knappenberger, S. Krimigis, H. Kucharek, M. Lee, G. Livadiotis, S. Livi, R.J. MacDowall, D. Mitchell, E. Möbius, T. Moore, N.V. Pogorelov, D. Reisenfeld, E. Roelof, L. Saul, N.A. Schwadron, P.W. Valek, R. Vanderspek, P. Wurz, G.P. Zank, “Global Observations of the Interstellar Interaction from the Interstellar Boundary Explorer-IBEX”, Science Express, Oct. 15, 2009.

Related links:

Animation shows how energetic neutral atoms are made in the heliosheath when hot solar wind protons grab an electron from a cold interstellar gas atom. The ENAs can then easily travel back into the solar system, where some are collected by IBEX. Credit: NASA/GSFC http://www.swri.org/temp/ibexscience/DM/SP_draft1.mov

Solar Journey: The Significant of Our Galactic Environment for the Heliosphere and Earth, Priscilla C. Frisch, editor. http://www.springer.com/astronomy/practical+astronomy/book/978-1-4020-4397-0

IBEX Web page at Southwest Research Institute http://ibex.swri.edu/

NASA’s Interstellar Boundary Explorer mission http://www.nasa.gov/mission_pages/ibex/index.html

To view a video related to this research, please visit http://astro.uchicago.edu/%7Efrisch/soljourn/Hanson/AstroBioScene7Sound.mov

Here is another press release on IBEX from Boston University:

IBEX discovers that galactic magnetic fields may control the boundaries of our solar system

NASA mission reveals impact of galaxy’s magnetic fields

(Boston) – The first all-sky maps developed by NASA’s Interstellar Boundary Explorer (IBEX) spacecraft, the initial mission to examine the global interactions occurring at the edge of the solar system, suggest that the galactic magnetic fields had a far greater impact on Earth’s history than previously conceived, and the future of our planet and others may depend, in part, on how the galactic magnetic fields change with time.

“The IBEX results are truly remarkable, with emissions not resembling any of the current theories or models of this never-before-seen region,” says Dr. David J. McComas, IBEX principal investigator and assistant vice president of the Space Science and Engineering Division at Southwest Research Institute. “We expected to see small, gradual spatial variations at the interstellar boundary, some 10 billion miles away. However, IBEX is showing us a very narrow ribbon that is two to three times brighter than anything else in the sky.”

A “solar wind” of charged particles continuously travels at supersonic speeds away from the Sun in all directions. This solar wind inflates a giant bubble in interstellar space called the heliosphere — the region of space dominated by the Sun’s influence in which the Earth and other planets reside. As the solar wind travels outward, it sweeps up newly formed “pickup ions,” which arise from the ionization of neutral particles drifting in from interstellar space. IBEX measures energetic neutral atoms (ENAs) traveling at speeds of roughly half a million to two and a half million miles per hour. These ENAs are produced from the solar wind and pick-up ions in the boundary region between the heliosphere and the local interstellar medium.

The IBEX mission just completed the first global maps of these protective layers called the heliosphere through a new technique that uses neutral atoms like light to image the interactions between electrically charged and neutral atoms at the distant reaches of our Sun’s influence, far beyond the most distant planets. It is here that the solar wind, which continually emanates from the Sun at millions of miles per hour, slams into the magnetized medium of charged particles, atoms and dust that pervades the galaxy and is diverted around the system. The interaction between the solar wind and the medium of our galaxy creates a complex host of interactions, which has long fascinated scientists, and is thought to shield the majority of harmful galactic radiation that reaches Earth and fills the solar system.

“The magnetic fields of our galaxy may change the protective layers of our solar system that regulate the entry of galactic radiation, which affects Earth and poses hazards to astronauts,” says Nathan Schwadron of Boston University’s Center for Space Physics and the lead for the IBEX Science Operations Center at BU.

Each six months, the IBEX mission, which was launched on October 18, 2008, completes its global maps of the heliosphere. The first IBEX maps are strikingly different than any of the predictions, which are now forcing scientists to reconsider their basic assumptions of how the heliosphere is created.

“The most striking feature is the ribbon that appears to be controlled by the magnetic field of our galaxy,” says Schwadron.

Although scientists knew that their models would be tested by the IBEX measurements, the existence of the ribbon is “remarkable” says Geoffrey Crew, a Research Scientist at MIT and the Software Design Lead for IBEX. “It suggests that the galactic magnetic fields are much stronger and exert far greater stresses on the heliosphere than we previously believed.”

The discovery has scientists thinking carefully about how different the heliosphere could be than they expected.

“It was really surprising that the models did not generate features at all like the ribbon we observed,” says Christina Prested, a BU graduate student working on IBEX. “Understanding the ribbon in detail will require new insights into the inner workings of the interactions at the edge of our Sun’s influence in the galaxy.”

Adds Schwadron,”Any changes to our understanding of the heliosphere will also affect how we understand the astrospheres that surround other stars. The harmful radiation that leaks into the solar system from the heliosphere is present throughout the galaxy and the existence of astrospheres may be important for understanding the habitability of planets surrounding other stars.”

IBEX is the latest in NASA’s series of low-cost, rapidly developed Small Explorers space missions. Southwest Research Institute in San Antonio, Texas, leads and developed the mission with a team of national and international partners. NASA’s Goddard Space Flight Center in Greenbelt, Md., manages the Explorers Program for NASA’s Science Mission Directorate in Washington.

The Center for Space Physics at Boston University carries out a wide variety of research in space physics including: space plasma physics, magnetospheric physics, ionospheric physics, atmospheric physics, and planetary and cometary atmospheric studies.