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Winter 2000

Science Bits


Researchers map global space weather

Researchers at the Johns Hopkins University (JHU) have developed a technique to simultaneously measure the magnetic and electrical fields over large areas of the ionosphere above the earth's polar regions, providing the first continuous monitoring of electric currents between space and the upper atmosphere and generating the first maps of electric power flowing into the polar upper atmosphere. These advances will allow greatly improved understanding and forecasting of global space weather and help prevent disruption of communication and power systems when electromagnetic storms strike.

The work, which was sponsored by NSF, makes use of magnetometers carried on each of the 66 satellites of the Iridium System satellite constellation operating as a global satellite communications network. Circling the globe in polar orbits, they are providing continuous measurements of the magnetic fields above the earth's poles. Scientists at JHU have developed techniques to extract the signatures of electrical currents flowing between the atmosphere and space from the magnetic field readings. Maps of the electric current in space are then constructed in much the same way that normal weather maps are made from weather station readings.

At the same time, SuperDARN—the Super Dual Auroral Radar Network, a multinational network of a dozen radars spread around the poles to study the ionosphere—is bouncing radar signals off the same regions to measure the electric field and its minute-by-minute variations.

"By combining Iridium System and SuperDARN data, we're able for the first time to continuously map the powerful currents flowing between space and the earth's upper atmosphere," says Brian Anderson, who leads the research effort. "This is a major achievement because monitoring this environment is extremely difficult due to its enormous volume, which can vary by a factor of ten in one hour. The Iridium orbits are ideal for monitoring this big system because the current is funneled to the polar regions, where the satellites detect it."

Using their extensive experience working with magnetic field data from satellites, the scientists were able to develop signal-processing techniques for automatically extracting needed signals from Iridium data so they could be combined in a useful way with SuperDARN data. "This was an essential part of the effort," says Anderson. "With so many satellites involved, any hands-on analysis of the data would have been impossible."

The maps of electrical current show dramatic shifts due to changes in the solar wind. These results will allow scientists to test computer models of the earth's space environment far more accurately and exhaustively than ever before.

Preliminary maps of the power flow have revealed "hot spots" of energy flowing into the atmosphere at high altitudes, creating pockets of hot air that rise and create drag on spacecraft flying through them at altitudes below 500 kilometers (300 miles).

"Timely, accurate space weather forecasts will give advance warning of electromagnetic storms that in the past have shown their ability to disrupt communications, degrade GPS accuracy, cripple electrical power grids, and menace astronauts, satellites, and aircraft with dangerous levels of radiation," says Anderson. He presented his findings in December at the fall meeting of the American Geophysical Union. More information is available on the Web.

Johns Hopkins University


Middle school science texts riddled with errors

Educators and parents place a great deal of faith in the accuracy of their children's textbooks. A new examination of some of the most widely used middle school physical science textbooks, however, has found texts that incorrectly state Newton's first law of motion and show the equator passing through the southern United States.

Other egregious errors spotted by the examiners included a textbook that asserts, within the same 12 pages, that "sound travels faster through warm air than cold air" and that "sound travels faster in colder air." Another gives an incorrect formula for the volume of a sphere.

The purpose of the two-and-a-half-year study, sponsored by a grant from the David and Lucile Packard Foundation, was to review and critique a dozen physical science textbooks used by a significant number of middle school students (sixth, seventh, and eighth graders). John Hubisz (North Carolina State University) is co-investigator of the study.

To conduct the study, Hubisz enlisted seven other reviewers already familiar with middle school science textbooks. "We had a good cross- section of teachers and teachers who teach teachers," Hubisz says. All reviewers have physics and teaching backgrounds that vary from middle school to graduate school, and all are involved with middle school teachers and/or curricula. All but one have more than 20 years of experience in the field.

Hubisz and his colleagues found numerous errors in scientific accuracy, faulty portrayals of the scientific approach, and inappropriate lessons for particular grade levels. As well, "The books have . . . many irrelevant photographs, complicated illustrations, experiments that could not possibly work, and diagrams and drawings that represented impossible situations," the report asserts. Most of the report's 100 pages list specific errors from several of the books reviewed.

In addition to those problems, the reviewers also had difficulty contacting the "authors" listed on the covers. "Of the several names listed in several of the textbooks, none that we contacted would claim to be an author and some did not even know that their names had been so listed. Instead of authors, we have a collection of people who checked parts or aspects of the textbook. Some of these reviewers actually panned the material and heard nothing further from the publisher," the report states.

"Our goal is to put pressure on publishers to get real authors for textbooks and for those authors to be in the right academic discipline," Hubisz says. Most of the physical science "authors" were biologists.

Without a clear-cut author to contact about errors, the study panel contacted publishers, who for the most part either dismissed the panel's findings or promised corrections in subsequent editions. Reviews of later editions frequently turned up more errors than corrections, the report says. Most publishers of the books reviewed are large, well-known companies that produce many of the science texts in today's classrooms, Hubisz says, and should be more responsive when confronted with errors that need to be corrected.

Hubisz plans to set up a Web site that will list other errors. The site, which should be up and running next fall, will solicit more textbook reviews and will post reviews in an ongoing effort to assist teachers, potential authors, and publishers.

To obtain a copy of the report, contact Hubisz at hubisz@unity.ncsu.edu.

North Carolina State University


Grasslands can act as carbon sinks

Scientists have long known that forests sometimes act as carbon sinks, absorbing more carbon dioxide than they release. Now, a team of researchers has identified a mechanism through which grasslands appear to demonstrate the same property. The research findings were published in the 11 January issue of Nature.

The lead author of the paper is Shuijin Hu (North Carolina State University). The project leaders are F. Stuart Chapin III (Hu's advisor at the Universty of California, Berkeley, during the project, now at the University of Alaska), Christopher Field (Carnegie Institution of Washington), and Harold Mooney (Stanford University). The work was supported by NSF grants.

Other scientists have proposed that grasslands can act as carbon sinks when atmospheric CO2 is elevated. This team's research, however, identified a mechanism through which grassland soils can sequester carbon, and, in fact, found a trend toward increased soil carbon under conditions of elevated CO2.

"Our data indicate that soil microbes quickly respond to changes in carbon and nitrogen availability and may play critical roles in determining the potential of grasslands—and other terrestrial ecosystems, too—to act as a carbon sink," Hu said.

The results are from a five-year study conducted at an annual grassland on Stanford University's Jasper Ridge Biological Preserve in central California. Between 1992 and 1997, the researchers maintained two sets of open-top chambers at the grassland, one in which CO2 was maintained at its current atmospheric level (360 parts per million), and one in which it was doubled to 720 ppm. In 1996 and 1997, the scientists analyzed soil core samples from each of the plots. They found a trend toward higher carbon content in the soil from plots with elevated CO2 levels.

Hu says the implications are that grasslands can be carbon sinks—at least for the short term. The magnitude of carbon sequestration in such a grassland is yet to be determined, he notes.

Hu explains that the increased atmospheric CO2 stimulates the grassland plants to grow more quickly, drawing increased nitrogen from the soil in the process. As a result, less nitrogen is available for use by the microbes in the soil, reducing the microbes' ability to decompose dead plant material. With less plant material decomposed, less carbon is released into the air as carbon dioxide. Additionally, the research indicated that under elevated carbon dioxide levels, fungi become a more dominant part of the microbial community, which is also conducive to protecting soil carbon from decomposition. And finally, the extent of carbon buildup in the grassland soil may be limited, because the lower rate of plant decomposition reduces the supply of nitrogen for additional plant growth.

North Carolina State University; University of California, Berkeley; Carnegie Institution; Stanford University


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Last revised: Wed Feb 7 15:34:33 MST 2001