In a report published today, new research suggests the enigmatic “ribbon” of energetic particles discovered at the edge of our solar system by NASA’s Interstellar Boundary Explorer (IBEX) may be only a small sign of the vast influence of the galactic magnetic field.
IBEX researchers have sought answers about the ribbon since its discovery in 2009. Comprising primarily space physicists, the IBEX team realized that the galactic magnetic field wrapped around our heliosphere — the giant “bubble” that envelops and protects our solar system — appears to determine the orientation of the ribbon and the placement of energetic particles measured in it.
An unlikely teaming of IBEX researchers with ultra-high-energy cosmic ray physicists, however, has produced complementary insights that dovetail with IBEX’s studies to produce a more complete picture of the interactions at the solar system boundary and how they reach much farther out into the space between the stars.
Data from NASA’s Interstellar Boundary Explorer (IBEX) spacecraft reveal that neutral interstellar atoms are flowing into the solar system from a different direction than previously observed.
Interstellar atoms flow past the Earth as the solar system passes through the surrounding interstellar cloud at 23 kilometers per second (50,000 miles per hour). The latest IBEX measurements of the interstellar wind direction were discovered to differ from those made by the Ulysses spacecraft in the 1990s. That difference led the IBEX team to compare the IBEX measurements to data gathered by 11 spacecraft between 1972 and 2011. Statistical testing of the Earth-orbiting and interplanetary spacecraft data showed that, over the past 40 years, the longitude of the interstellar helium wind has changed by 6.8 ± 2.4 degrees.
“We concluded it’s highly likely that the direction of the interstellar wind has changed over the past 40 years. It’s also highly unlikely that the direction of the interstellar helium wind has remained constant,” says Dr. Priscilla Frisch, lead author of the study and a senior scientist in the Department of Astronomy and Astrophysics at the University of Chicago.
Full Story: http://www.swri.org/9what/releases/2013/ibex-wind.htm#.UilbyiywUV0
NASA’s Interstellar Boundary Explorer (IBEX) spacecraft recently provided the first complete pictures of the solar system’s downwind region, revealing a unique and unexpected structure.
Researchers have long theorized that, like a comet, a “tail” trails the heliosphere, the giant bubble in which our solar system resides, as the heliosphere moves through interstellar space. The first IBEX images released in 2009 showed an unexpected ribbon of surprisingly high energetic neutral atom (ENA) emissions circling the upwind side of the solar system. With the collection of additional ENAs over the first year of observations, a structure dominated by lower energy ENAs emerged, which was preliminarily identified as the heliotail. However, it was quite small and appeared to be offset from the downwind direction, possibly because of interactions from the galaxy’s external magnetic field.
As the next two years of IBEX data filled in the observational hole in the downwind direction, researchers found a second tail region to the side of the previously identified one. The IBEX team reoriented the IBEX maps and two similar, low-energy ENA structures became clearly visible straddling the downwind direction of the heliosphere, indicating structures that better resemble “lobes” than a single unified tail.
Since its October 2008 launch, NASA’s Interstellar Boundary Explorer (IBEX) has provided images of the invisible interactions between our home in the galaxy and interstellar space. Particles emanating from this boundary produce a striking, narrow ribbon, which had yet to be explained despite more than a dozen possible theories. In a new “retention model,” researchers from the University of New Hampshire and Southwest Research Institute suggest that charged particles trapped in this region create the ribbon as they escape as neutral atoms.
The Sun continually sends out a solar wind of charged particles or ions traveling in all directions at supersonic speeds. IBEX cameras measure energetic neutral atoms (ENAs) that form when charged particles become neutralized.
As solar wind ENAs leave the solar system, the majority move out in various directions, never to re-enter. However, some ENAs leave the solar system and impact other neutral atoms, becoming charges particles again. These newly formed pickup ions begin to gyrate around the local interstellar magnetic field just outside the solar system. In the regions where the magnetic field is perpendicular to their initial motion, they scatter rapidly and pile up. From those regions, some of those particles return to the solar system as secondary ENAs — ENAs that leave the solar system and become charged and then re-neutralized, only to travel back into the solar system as ENAs a second time.
“The syrup you pour on a pancake piles up before slowly oozing out to the sides,” says Dr. David McComas, IBEX principal investigator and assistant vice president of the SwRI Space Science and Engineering Division. “The secondary ENAs coming into the solar system after having been temporarily trapped in a region just outside the solar system do the same thing. As they pile up and get trapped or retained, they produce higher fluxes of ENAs from this region and form the bright ribbon seen by IBEX.”
Using data from NASA’s Interstellar Boundary Explorer (IBEX) spacecraft, an international team of researchers has measured neutral “alien” particles entering our solar system from interstellar space. A suite of studies published in theAstrophysical Journal provide a first look at the constituents of the interstellar medium, the matter between star systems, and how they interact with our heliosphere.
The heliosphere, the “bubble” in which our Sun and planets reside, is formed by the interaction between the solar wind, flowing outward from the Sun, and the interstellar medium, which presses up against it. Electrically charged, or ionized, particles cannot penetrate the boundary between these two bodies. However, neutral particles, which make up about half the material outside the heliosphere, flow freely in through the boundary.
The only other spacecraft to directly detect these inflowing neutral particles was Ulysses, which more than a decade ago measured interstellar neutral helium. Although IBEX is designed primarily to map the interactions between the solar wind and ionized interstellar material, its low-energy energetic neutral atom camera has now also measured interstellar neutral particles not detected by Ulysses. From its location within Earth’s orbit, IBEX has sampled interstellar hydrogen, oxygen, and neon in addition to neutral helium.
NASA will host a Science Update at 1 p.m. EST, Tuesday, Jan. 31, 2012, to discuss new analysis from NASA’s Interstellar Boundary Explorer (IBEX) spacecraft of material from outside our solar system and the interstellar boundary region that surrounds our home in space.
The interstellar boundary region shields our solar system from most of the dangerous galactic cosmic radiation that otherwise would enter the solar system from interstellar space.
The briefing will take place at NASA Headquarters in the James E. Webb Auditorium, located at 300 E St. SW, Washington, and will air live on NASA Television and the agency’s website.
OBSERVATIONS IMPROVE UNDERSTANDING OF THE HELIOSPHERE
The outer regions of the heliosphere, a giant bubble around the solar system created by solar wind, are difficult to study directly. The Interstellar Boundary Explorer (IBEX) mission, which maps emission of energetic neutral atoms from the boundary between the heliosphere and the interstellar medium, has greatly contributed to understanding of the heliosphere and even discovered some unexpected features. In particular, IBEX maps show a strange “ribbon” of enhanced energetic neutral atom emission that was not predicted by any theory. The origins of this ribbon, which stretches more than 300 degrees across the sky, remain unknown. McComas et al. review IBEX observations, current understanding of the heliosphere, hypotheses that have been proposed to explain the ribbon, and directions for future research.
NEW DETAIL ON AURORAS
High-resolution imaging from spacecraft is revealing new detail on structures in bright, dynamic auroras. In the auroral regions where particles are accelerated to high energies, dynamic structures evolve on time scales of seconds or less, though the processes that drive particle acceleration and transfer of energy to small scales are not fully understood. Chaston et al. show how new spaceborne auroral imagery combined with simultaneous particle measurements can help improve understanding of the physical processes involved in the aurora. In particular, they show how magnetic reconnection (in which magnetic field lines break and reconnect, releasing energy), tearing, and sheared flows can transfer energy from larger to smaller scales and help form the auroral structures observed.