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Changes in River Chemistry Affect Water Supplies

August 26, 2013
Contacts: 

Heather Dewar 301-405-9267

COLLEGE PARK, Md. – Human activities are changing the basic chemistry of many rivers in the Eastern U.S., with potentially major consequences for urban water supplies and aquatic ecosystems, a University of Maryland-led study has found.

In the first survey of its kind, researchers looked at long-term records of alkalinity trends in 97 streams and rivers from Florida to New Hampshire. Over time spans of 25 to 60 years, two-thirds of the rivers had become significantly more alkaline and none had become more acidic.

Caption 1: Appalachian mountain streams like this one in Western Maryland are especially vulnerable to the effects of accelerated chemical weathering because of carbon-rich surface rocks, steep slopes that promote erosion, and extensive impacts from acid rain and acidic mining runoff. Photo: Sujay S. KaushalAlkalinity is a measure of water's ability to neutralize acid. In excess, it can cause ammonia toxicity and algal blooms, altering water quality and harming aquatic life. Increasing alkalinity hardens drinking water, makes wastewater disposal more difficult, and exacerbates the salinization of fresh water.

Paradoxically, higher acid levels in rain, soil and water, caused by human activity, are major triggers for these changes in river chemistry, said associate professor Sujay Kaushal of the University of Maryland. Kaushal, a geologist, is the lead author of a paper about the study, published August 26 in the online edition of the peer-reviewed journal Environmental Science and Technology.

The researchers hypothesize that acid rain, a by-product of fossil fuel burning, acidic mining runoff and agricultural fertilizers speed up the dissolving of surfaces that are naturally high in alkaline minerals. In a process known as chemical weathering, the acid eats away at limestone, other carbonate rocks, and even concrete sidewalks, dissolving alkaline particles that wash off into streams and rivers.

Scientists have studied the effects of increased chemical weathering in small mountain streams tainted by acid runoff, where the process can actually help rebalance streams' pH levels. But researchers have not looked at the accumulating levels of alkalinity in downstream reaches of numerous major rivers and evaluated potential causes until now, Kaushal said.

"It's like rivers on Rolaids," Kaushal said. "We have some natural antacid in  watersheds. In headwater streams, that can be a good thing. But we're also seeing antacid compounds increasing downriver. And those sites are not acidic, and algae and fish can be sensitive to alkalinity changes."  

Caption 2: Alkaline minerals wash down from headwater streams and tributaries of the 14,700-square-mile Potomac River watershed to Washington D.C., where the river provides the nation's capital with drinking water and receives treated sewage before emptying into the Chesapeake Bay. High alkalinity makes drinking water treatment more expensive, adds to regulatory requirements for discharging treated sewage, and compounds the environmental problems of the nation's largest estuary. Photo: Michael PenninoAlkalinity has risen over the past several decades in rivers that provide water for Washington, D.C., Philadelphia, Baltimore, Atlanta, and other major cities, the researchers reported. Also affected are rivers that flow into water bodies already harmed by excess algae growth, such as the Chesapeake Bay.

The extent of the change is "amazing. I did not expect that," said noted ecologist Gene Likens, a co-discoverer of acid rain in 1963, who collaborated with Kaushal on this research.

"This is another example of the widespread impact of human impacts on natural systems which is, I think, increasingly worrisome," said Likens, a Unversity of Connecticut distinguished research professor and founding director of the Cary Institute of Ecosystem Studies. "Policymakers and the public think acid rain has gone away, but it has not."

Beginning in the mid-1990s after Congress amended the Clean Air Act, new federal regulations have reduced the airborne pollutants that cause acid rain. "It may be that these are legacy impacts of acid rain in addition to mining and land use," Kaushal said. "The acid rain problem is decreasing. But meanwhile there are these lagging effects of river alkalinization showing up across a major region of the U.S. How many decades will river alkalinization persist? We really don't know the answer."

The team focused on Eastern rivers, which are often important drinking water sources for densely populated areas and have decades' worth of water quality records. Much of the Eastern U.S. is also underlain by porous, alkaline limestone and other carbonate rocks, making the region more prone to the types of water chemistry changes that the researchers found. This is especially true in the Appalachian Mountains where soils are thin, steep slopes cause erosion, and acid rain from smokestack industries have had a major impact on forests and streams.

Water alkalinity has increased the fastest in areas underlain by carbonate rocks, at high elevations, and where acid rainfall or drainage was high. The researchers also found that the chemical weathering of these carbonate rocks adds to the carbon burden in rivers and streams, in a trend that parallels rising carbon dioxide levels in the atmosphere.

The research was funded by NASA Carbon Cycle & Ecosystems, the National Science Foundation's Long Term Ecological Research Program, and the Andrew W. Mellon Foundation.

Creating Next Generation Electric Vehicle Batteries

August 23, 2013
Contacts: 

Ted Knight 301-405-3596

COLLEGE PARK, Md. – Two research teams from the University of Maryland Energy Research Center (UMERC) were awarded research grants from the Advanced Research Projects Agency-Energy (ARPA-E) to develop transformational electric vehicle (EV) energy storage systems using innovative chemistries, architectures and designs.

The two UMD projects were among 22 selected nationwide that received a total of $36 million in research funding from ARPA-E’s new program, Robust Affordable Next Generation Energy Storage Systems (RANGE). ARPA-E’s RANGE program aims to accelerate widespread EV adoption by dramatically improving driving range and reliability, and by providing low-cost, low-carbon alternatives to today’s vehicles.

Multiple-Electron Aqueous Battery
Lithium-ion batteries have not been extensively adopted in electric vehicles due to short driving range, high cost, and low safety and reliability, which can increase the cost and reduce energy density. Researchers at UMD and the Army Research Laboratory (ARL) will develop a new battery—a hybridized ions aqueous battery—by doubling the cell voltage and capacity, which could cut the lithium-ion battery system cost in half and would enable an EV to travel two times as long per charge.

The new battery could significantly reduce the cost of battery management, improve the reliability, and operate in a wide temperature range. If successful, UMD’s battery would make EVs cost/safety-competitive and travel 300 miles on a single charge, contributing to the widespread public acceptance of EVs. Increased use of EVs would decrease U.S. dependence on foreign oil, and reduce CO2 emissions from burning the gasoline, which accounts for 28 percent of the greenhouse gas emissions.

Led by professor of chemical and biomolecular engineering Chunseng Wang, in partnership with Kan Xu at ARL, the “Multiple-Electron Aqueous Battery” project was awarded $405,000.

Solid-State Lithium-Ion Battery with Ceramic Electrolyte
A second group of UMD researchers will develop ceramic materials and processing methods to enable high-power, solid-state, lithium-ion batteries. While most lithium-ion batteries are liquid based, solid-state batteries have a greater abuse tolerance that reduces the need for heavy protective components. UMD will leverage multi-layer ceramics processing methods to produce a solid-state battery pack with lower weight and longer life. The team will develop intrinsically safe, robust, low-cost, high-energy-density all-solid-state lithium-ion batteries.

"Due to their all solid state construction, these lithium-ion batteries are non-flammable and intrinsically safe. Moreover, their novel highly conductivity materials and fabrication methods will exceed current goals for electric vehicle range, acceleration, and cost,” says UMERC director and professor of materials science and engineering Eric Wachsman, the lead on the project, which was awarded $574,275.

In addition to Wachsman, UMD professor Liangbing Hu and University of Calgary professor Venkataraman Thangadurai are team members on the project.

Helping Discover Students' Sustainability Knowledge

August 23, 2013
Contacts: 

Mark Stewart 301-405-4633

Researchers at the University of Maryland, in collaboration with researchers at the Ohio State University—a Big Ten university, have developed an assessment to measure sustainability knowledge across its three domains: environmental, economic, and social.COLLEGE PARK, Md. – Researchers at the University of Maryland, in collaboration with researchers at the Ohio State University—a Big Ten university, have developed an assessment to measure sustainability knowledge across its three domains: environmental, economic, and social. The Assessment of Sustainability Knowledge (ASK) is already helping other colleges and universities discover what their students know, or don’t know, about sustainability.

Higher education institutions are scrambling to develop new sustainability academic programs to prepare students to tackle some of the greatest challenges facing humankind. From 2007 to 2012, the number of sustainability- focused academic programs grew from 27 to 588 according to the Association for the Advancement of Sustainability in Higher Education (AASHE). During the same period, 673 institutions signed the American College and University Presidents’ Climate Commitment and pledged to educate all students about sustainability.

Despite this growth, there is little information on what students know about sustainability when they enter college and what they learn while there. AASHE encourages all 254 institutions participating in the Sustainability, Tracking, Assessment, and Rating System (STARS) to test their students’ sustainability knowledge; however, few institutions have the time or resources to develop valid and reliable assessments.

Research teams at UMD and OSU each started developing their own sustainability knowledge assessments in 2009 and then joined forces in 2012 to merge the best of each of their questions into one assessment. In the spring of 2013, more than 3,000 UMD and OSU undergraduate students completed the combined assessment. Researchers then analyzed how each question performed to create a valid question set for testing sustainability knowledge. They recently published that question set in the Assessment of Sustainability Knowledge (ASK).

The UMD and OSU researchers invite colleges and universities to use some or all of the questions in the ASK to assess the level of sustainability knowledge among students at their own institutions. To date, Colorado State University, University of Mississippi, Clark University, Clarkson University, and the University of Idaho Sustainability Center either have used or intend to use the ASK on their campuses.

UMD Tool Predicts Leadership of Terrorist Networks

August 22, 2013
Contacts: 

Lee Tune 301-405-4679

COLLEGE PARK, Md. – The loss of a terrorist or criminal network's leader—whether through imprisonment, change of allegiance or death—can create a vacuum in which subordinates jockey for position or splinter into factions.

Rather than wait to see how these scenarios play out, U.S. intelligence analysts could soon have a new tool to help predict who might rise to the top of a terrorist or criminal network, and whether the redefined organization has an increased ability to carry out its activities.

A University of Maryland research team developed this analytics tool, known as STONE (Shaping Terrorist Organizational Network Efficacy), "to minimize the impact of these organizations," says V.S. Subrahmanian, a professor of computer science who is leading the UMD effort.

The UMD team has used open-source data to hypothetically test the software platform on four known terrorist organizations: al-Qaeda, Hamas, Hezbollah and Lashkar-e-Taiba, perpetrators of the November 2008 attack on Mumbai, India.

STONE was able to predict with 80 percent accuracy what individual would rise to take on a leadership role when a terrorist leader was removed, Subrahmanian says. The data the Maryland team used was unclassified, and included information such as how long a person was actively involved with an organization, the specific role they had, and the roles of others they were directly associated with.

U.S. government analysts and decision-makers with access to a "more complete" picture of these organizations can input their own data into STONE, increasing the tool's accuracy, Subrahmanian says.

"This is a not a computing tool that tells [analysts] what to do," he says. "It is something that can help them better understand the situation or situations they are dealing with, which can ultimately decrease the efficacy of these organizations."

Law Enforcement and Business Applications
Subrahmanian says STONE could also potentially be used to evaluate leadership changes in criminal networks and in business, for example identifying who will replace a corporate CEO or who will step into a new role in a drug network. However, he and his colleagues have not yet tested it for these applications.

The Maryland researchers—Subrahmanian, Francesca Spezzano and Aaron Mannes, all associated with the University of Maryland Institute for Advanced Computer Studies—will present a paper on their work at an international conference on Aug. 27. The Advances in Social Networks Analysis and Mining conference in Niagara Falls, Canada, is sponsored by the Institute of Electronics and Electronics Engineers and the Association for Computing Machinery.

Premier New Gamma Ray Observatory Begins Operation

August 21, 2013
Contacts: 

Lee Tune 301-405-4679

COLLEGE PARK, Md. – A joint U.S. and Mexican gamma ray observatory being built on the flanks of the Sierra Negra volcano in the Mexican State of Puebla has begun official operations. Led on the U.S. side by the University of Maryland, the observatory is only about one-third complete, but already it is the largest of its type in the world.

Deployment of tanks and counting house trailers on the HAWC platform as seen from the slope of the volcano Sierra Negra (April 2013). The volcano Pico de Orizaba is visible in the background. Gamma rays are the most energetic form of light (electro-magnetic radiation) and are produced by the most violent events and hottest regions of the universe: supernova star explosions, active galactic nuclei caused by super massive black holes and gamma ray bursts. Gamma rays also are thought to be correlated with the acceleration sites of charged cosmic rays, whose origins have been a mystery for nearly 100 years.

The HAWC (High-Altitude Water Cherenkov Observatory) facility is designed to observe the highest energy (TeV) gamma rays and cosmic rays with an instantaneous aperture that covers more than 15 percent of the sky. With this large field of view, the detector will be exposed to half of the sky during a 24-hour period.

"HAWC will be the world's premier wide-field TeV gamma ray observatory with between 10 and 15 times the sensitivity of previous generation wide-field gamma ray detectors such as Milagro," says UMD professor of physics Jordan Goodman, who is the Principal Investigator for the National Science Foundation HAWC construction grant that is funded through UMD and covers about half of the approximately $14 million cost of the construction. 

UMD physicist Andrew Smith is the HAWC project manager. UMD scientists Brian Baughman, Jim Braun and Josh Wood also are involved in the construction of HAWC and together with Goodman and Smith will help lead in the analysis of data from the observatory.

Detecting Gamma Rays
The HAWC observatory currently has some 111 detectors and will have a total of 300 when it is completed in 2014.When high-energy gamma rays enter the atmosphere they collide with and split air molecules into more particles and gamma rays. These in turn interact with more particles, losing energy, but creating new particles and gamma rays each time. This chain reaction results in a cascade, or shower, of particles and radiation that multiplies and expands outward all the way to the ground, where it reaches the HAWC's water Cherenkov detectors. The HAWC observatory currently has some 111 detectors and will have a total of 300 when it is completed in 2014.

When the gamma ray-caused cosmic cascade goes through the water-filled Cherenkov detectors, the cascade particles, traveling faster than the light inside the water, create an effect similar to a supersonic airplane producing a shock wave (the so-called sonic "boom"). But in this case, the particles produce a visible light trail instead of sound waves. These flashes are measured by light detectors located at the bottom of each Cherenkov detector. By computationally reconstructing the combined signals from all the detectors, it is possible for scientists to determine the energy, direction, time of arrival and the nature of the responsible gamma ray.

The new HAWC observatory is supported by numerous U.S. and Mexican institutions, including the National Science Foundation, the Los Alamos National Laboratory, the Department of National Energy, the University of Maryland, Consejo Nacional de Ciencia y Tecnología, the Universidad Nacional Autónoma de México, the Instituto Nacional de Astrofísica and the Óptica y Electrónica.

UMD Named a Top 25 LGBT-Friendly Campus

August 20, 2013
Contacts: 

Beth Cavanaugh 301-405-4625

COLLEGE PARK, Md. - The University of Maryland has again been recognized for its diversity and inclusion by being named a Top 25 College for lesbian, gay, bisexual, and transgender (LGBT) people by Campus Pride, a leading national organization that works to help create LGBT-friendly colleges and universities.

UMD is the only Maryland/Washington, D.C.-area university to make the list this year. To qualify for the list, each institution must earn five stars overall in the Campus Pride Index, as well as sexual orientation and gender identity/expression, and score 4.5 stars or above in all eight LGBT-friendly factors.

According to the Huffington Post, which published the listing, "The organization determined the listing by utilizing the data gathered from the Campus Pride Index.  'Campus Pride's Index is the only one of its kind,' said Campus Pride Executive Director Shane Windmeyer. 'Unlike other commercially-driven rankings, our ratings are done for and by LGBT people and set in a foundation of solid research practice.'"

Fifteen years ago, UMD created the LGBT Equity Center to help establish and maintain a fully equitable campus environment for people of all sexual orientations and gender identities or expressions. Today, the LGBT Equity Center has expanded its mission to include empowering innovators and agents of inclusion for LGBT people.

Other university initiatives include:

  • Development of a growing set of policies and practices to protect and support transgender people
  • Housing options and assistance for LGBTQ students
  • Expansion of campus resources that empower leaders and allies to build communities and advocate for LGBT equity
  • Creation of an award-winning first-year experience for new students who identify as LGBT or allies
  • Creation of one of the country's few stand-alone LGBT Studies Programs, offering a certificate and minor in LGBT Studies.

"UMD strives to remain at the forefront of supporting our LGBT student population so that they may reach their full potential," said Luke Jensen, director of UMD's campus LGBT Equity Center.  "We are also committed to preparing all students to become leaders who will create positive change for LGBT diversity and inclusion wherever they go."

UMD Recognized as Top D.C.-Area Employer

August 20, 2013
Contacts: 

Alana Carchedi 301-405-0235

The University of Maryland has been recognized as one of the top 10 highest-rated D.C.-area employers on Glassdoor.com. COLLEGE PARK, Md. – The University of Maryland has been recognized as one of the top 10 highest-rated D.C.-area employers by Glassdoor.com.

Glassdoor, a website where current and former employees can anonymously rate their workplace, looked at D.C.-area companies that have received at least 25 reviews from local employees over the past two years. The reviews are based on employees' rankings in five categories: career opportunities, compensation and benefits, work/life balance, senior management, and culture and values.

An overall rating of 3.9 put UMD at No.9 on the top 10 list—one of only three non-Federal employers recognized.

Employee reviews on Glassdoor tout the university as "a quality school with national recognition, quality staff and proximity to many resources close to the nation's capital," and recognize UMD for having "outstanding staff and administration that is seeking creative solutions and thinking." Several reviews applauded the university's diverse student population that "makes teaching more interesting and challenging."

The full list of top D.C.-area employers is available here.

UMD 38th among World's Top Universities

August 16, 2013
Contacts: 

Alana Carchedi 301-405-0235

The University of Maryland again has placed among the world's top universities in the 2013 Academic Ranking of World Universities (ARWU).COLLEGE PARK, Md. – The University of Maryland again has placed among the world's top universities in the 2013 Academic Ranking of World Universities (ARWU). The ARWU, which is released each year by the Center for World-Class Universities at Shanghai Jiao Tong University, ranks UMD No. 38 overall in the world, No. 29 nationally, and No. 13 among U.S. public research institutions.

In a separate ARWU ranking of broad subject fields, the university placed 16th in the category of engineering/technology and computer science, 19th in the social sciences and 24th in natural sciences and mathematics.

Additionally, in specific subject fields, UMD ranks No. 15 in computer science, No. 19 in physics, and No. 24 in math, economics and business. 

UMD was also recently ranked as a top 100 university globally in Times Higher Education's World Reputation Rankings and World University Rankings.

To see the full ARWU rankings, visit http://www.shanghairanking.com/ARWU2013.html.

UMD Ranks 13th among Nation's Greenest Universities

August 15, 2013
Contacts: 

Andrew Muir 301-405-4723

COLLEGE PARK, Md. – The University of Maryland has been ranked No. 13 by The Sierra Club in their seventh annual ranking of America's greenest universities.

The University of Maryland has been ranked No. 13 by The Sierra Club in their seventh annual ranking of America's greenest universities.The rankings are compiled from scores in all areas of sustainability, including outreach, energy consumption, waste management, transportation, innovations and more. UMD received perfect scores in co-curriculum and planning with high marks in the areas of waste management, innovation and transportation.

"I think the university and the many people involved in the campus sustainability effort should be proud of the Sierra Club ranking and what has been accomplished. Our students, faculty and staff realize we have many challenges ahead, but are collectively seeking strategies that will allow the campus and the surrounding community to rise to the next level of performance," said Scott Lupin, director of the Office of Sustainability and associate director for the Department of Environmental Safety.

Some of the key factors that contributed to the university's high ranking include:

  • The university decreased its carbon footprint 14.4% from 2005 to 2011
  • Facilities Management, Dining Services, and the Stamp Student Union partnered to expand compost collection
  • Students contributed more than $500,000 to fund 40 sustainability projects led by students, faculty and staff
  • More than 200 students declared the Sustainability Studies Minor within the first year of the program
  • More than 100 professors in all 13 colleges/schools revised their courses to include sustainability lessons
  • More than 120 campus offices participated in the Green Office program
  • Shuttle-UM ridership increased from 1.5 million riders in 2005 to 3.4 million riders in 2012

The co-curriculum achievement was earned by "providing students with sustainability learning experiences outside the formal curriculum."  In this area, UMD shined as it nurtures a campus culture immersed in sustainability.  A perfect score was also achieved in planning due, in part, to the strength and vision of the university's  Strategic Plan, Facilities Master Plan and the Climate Action Plan which were developed with broad campus input and participation.

Along with co-curriculum and planning, transportation added to a successful ranking.  "A robust, fare- free shuttle system, over 4,000 bicycle parking spaces and transportation demand management strategies tailored to decrease the number of parking permits issued to single occupancy vehicles all combine to support increases in transit use and cycling and decreases in parking registrations. Our campus sustainable transportation is more than a buzzword, it is becoming commonplace," said Beverly Malone, assistant director for The Department of Transportation Services.
 
UMD's score was further bolstered by a strong waste management strategy. "The recycling program at The University of Maryland is well established and growing every year. Our campus community has enthusiastically embraced the program, which is demonstrated by our increasing diversion rate.  It is a pleasure to be a part of such an environmentally conscious community," said Bill Guididas, coordinator of recycling and solid waste for Facilities Management.

The university continues to take pride in the campus-wide engagement of staff, students and faculty in developing a culture of sustainability.  The upcoming Sustainability Progress Report, set for release at the end of September, will highlight the array of campus achievements and goals it has set out to accomplish.

Voyager 1 Has Left the Solar System, Says New Study

August 15, 2013
Contacts: 

Lee Tune, UMD Communications 301-405-4679
Marc Swisdak, UMD research scientist, 301-405-1495

COLLEGE PARK, Md. – Voyager 1 appears to have at long last left our solar system and entered interstellar space, says a University of Maryland-led team of researchers.

Voyager 1 appears to have at long last left our solar system and entered interstellar space, says a University of Maryland-led team of researchers. Photo source: NASA.gov Carrying Earthly greetings on a gold plated phonograph record and still-operational scientific instruments – including the Low Energy Charged Particle detector designed, built and overseen, in part, by UMD's Space Physics Group – NASA's Voyager 1 has traveled farther from Earth than any other human-made object. And now, these researchers say, it has begun the first exploration of our galaxy beyond the Sun's influence.

"It's a somewhat controversial view, but we think Voyager has finally left the Solar System, and is truly beginning its travels through the Milky Way," says UMD research scientist Marc Swisdak, lead author of a new paper published online this week in The Astrophysical Journal Letters. Swisdak and fellow plasma physicists James F. Drake, also of the University of Maryland, and Merav Opher of Boston University have constructed a model of the outer edge of the Solar System that fits recent observations, both expected and unexpected.

Their model indicates Voyager 1 actually entered interstellar space a little more than a year ago, a finding directly counter to recent papers by NASA and other scientists suggesting the spacecraft was still in a fuzzily-defined transition zone between the Sun's sphere of influence and the rest of the galaxy.

But why the controversy? 
At issue is what the boundary-crossing should look like to Earth-bound observers 11 billion miles (18 billion kilometers) away.  The Sun's envelope, known as the heliosphere, is relatively well-understood as the region of space dominated by the magnetic field and charged particles emanating from our star.  The heliopause transition zone is both of unknown structure and location.  According to conventional wisdom, we'll know we've passed through this mysterious boundary when we stop seeing solar particles and start seeing galactic particles, and we also detect a change in the prevailing direction of the local magnetic field. 

NASA scientists recently reported that last summer, after eight years of travel through the outermost layer of the heliosphere, Voyager 1 recorded "multiple crossings of a boundary unlike anything previously observed."  Successive dips in, and subsequent recovery of, solar particle counts caught researchers' attention.  The dips in solar particle counts corresponded with abrupt increases in galactic electrons and protons.  Within a month, solar particle counts disappeared, and only galactic particle counts remained.  Yet Voyager 1 observed no change in the direction of the magnetic field. 

To explain this unexpected observation, many scientists theorize that Voyager 1 has entered a "heliosheath depletion region," but that the probe is still within the confines of the heliosphere. Swisdak and colleagues, who are not part of the Voyager 1 mission science teams, say there is another explanation.

In previous work, Swisdak and Drake have focused on magnetic reconnection, or the breaking and reconfiguring of close and oppositely-directed magnetic field lines.  It's the phenomenon suspected to lurk at the heart of solar flares, coronal mass ejections and many of the sun's other dramatic, high-energy events.  The UMD researchers argue that magnetic reconnection is also key to understanding NASA's surprising data. 

Though often depicted as a bubble encasing the heliosphere and its contents, the heliopause is not a surface neatly separating "outside" and "inside."  In fact, Swisdak, Drake and Opher assert that the heliopause is both porous to certain particles and layered with complex magnetic structure.  Here, magnetic reconnection produces a complex set of nested magnetic "islands," self-contained loops which spontaneously arise in a magnetic field due to a fundamental instability.  Interstellar plasma can penetrate into the heliosphere along reconnected field lines, and galactic cosmic rays and solar particles mix vigorously. 

Most interestingly, drops in solar particle counts and surges in galactic particle counts can occur across "slopes" in the magnetic field, which emanate from reconnection sites, while the magnetic field direction itself remains unchanged.  This model explains observed phenomena from last summer, and Swisdak and his colleagues suggest that Voyager 1 actually crossed the heliopause on July 27, 2012.

In a NASA statement, Ed Stone, Voyager project scientist and a professor of physics of the California Institute of Technology, says, in part, "Other models envision the interstellar magnetic field draped around our solar bubble and predict that the direction of the interstellar magnetic field is different from the solar magnetic field inside. By that interpretation, Voyager 1 would still be inside our solar bubble. The fine-scale magnetic connection model [of Swisdak and colleagues] will become part of the discussion among scientists as they try to reconcile what may be happening on a fine scale with what happens on a larger scale."  Read the full NASA Voyager statement here: http://www.nasa.gov/mission_pages/voyager/voyager20130815.html.

Voyager Interstellar Mission
In the 36th year after their 1977 launches, the twin Voyager 1 and 2 spacecraft continue exploring where nothing from Earth has flown before. Their primary mission was the exploration of Jupiter and Saturn. After making a string of discoveries there -- such as active volcanoes on Jupiter's moon Io and intricacies of Saturn's rings -- the mission was extended. Voyager 2 went on to explore Uranus and Neptune, and is still the only spacecraft to have visited those outer planets. The current mission for both spacecraft, the Voyager Interstellar Mission, is to explore the outermost edge of the Sun's domain and beyond. Both Voyagers are capable of returning scientific data from a full range of instruments, with adequate electrical power and attitude control propellant to keep operating until 2020. Voyager 2 is expected to enter interstellar space a few years after its twin. The Voyager spacecraft were built and continue to be operated by NASA's Jet Propulsion Laboratory, in Pasadena, Calif.

University of Maryland scientists lead the Deep Impact spacecraft science team and are part of the science teams of many of the other spacecraft exploring our Solar System, including both Voyagers and Cassini.

This work by Swisdak, Drake and Opher was supported by National Science Foundation (NSF) grant AGS-1202330 to the University of Maryland, and NSF grant ATM-0747654 and NASA grant NNX07AH20G to Boston University.

 

Written by Barbara Brawn-Cinani and edited by Lee Tune.

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