RICE—Radio Ice Cherenkov Experiment. David Besson, University of Kansas. Electromagnetic radiation (such as light, x-rays, and gamma rays) cannot escape from inside the most active regions of the Universe, for instance from the nuclei of galaxies, nor can the highest energy gamma rays propagate through intergalactic space because they will be absorbed by the cosmic background infrared photons. Neutrinos, however, can traverse a considerable amount of material unimpeded. If they can be detected in such a way that their arrival direction and energy can be determined, they can be used to study high-density regions and highest energy events of the cosmos.

When an electron-type neutrino does interact in a dielectric medium (such as the deep glacial ice beneath South Pole), it will produce an electron and positron shower that will rapidly radiate away the energy of the original neutrino as electromagnetic radiation. The probability of such interactions increases with increasing energy, so that a detector's sensitivity increases with energy. Thus, a modest-sized (by neutrino detector standards) instrumented volume of ice—about a 100-meter cube—could have an effective volume of a cubic kilometer, a size deemed necessary to do astronomy. Our project will determine the feasibility of the radio detection of neutrino interactions in ice. (AA-123-O)

AMANDA—Antarctic Muon and Neutrino Detector Array, Robert Morse, University of Wisconsin. The primary objective of AMANDA is to discover sources of very-high-energy neutrinos from galactic and extragalactic sources. These neutrinos could be of diffuse origin, coming from the contributions of many active galactic nuclei (AGNI), or they could be point sources of neutrinos coming from supernova remnants (SNRs), rapidly rotating pulsars, neutron stars, individual blazars, or other extragalactic point sources.

The AMANDA array, which consists of photomultiplier tubes embedded between 1 and 2 kilometers deep in the antarctic ice near the South Pole, uses natural ice as a Cherenkov detector for high-energy neutrinos of astrophysical origin that have passed through Earth. Recently, new sources of high-energy gamma rays have been discovered, such as the source Mrk-421 discovered by the CGRO and Mt. Hopkins Observatory. Believed to be copious emitters of high-energy neutrinos, objects like this are what AMANDA has been designed to study. To date, neutrino astronomy has been limited to the detection of solar neutrinos and one brief burst from the supernova that appeared in the Large Magellanic Cloud in February 1987 (SN-1987a). Only now is it becoming technically feasible to build large neutrino telescopes, and as one of the first-generation detectors, AMANDA promises to be a large contributor to this new branch of neutrino astronomy. (AA-130-O)

Antarctic long-duration balloonborne observations of the anistropy of the cosmic microwave background on angular scales of 0.2 to 4 degrees. Andrew Lange, California Institute of Technology. The angular intensity distribution on the sky of the cosmic microwave background radiation carries a wealth of information about the early Universe because this radiation started on its journey to us just a few hundred thousand years after the Big Bang. The details of the distribution on angular scales from a few degrees to a few minutes can cleanly discriminate between competing models of the dark matter that makes up most of the gravitationally attracting mass of the Universe. This balloonborne microwave telescope—called BOOMERANG—will measure variations on a scale from 12 minutes to 3.6 degrees. BOOMERANG has already been flown for a short flight in the United States and will be flown on a long-duration balloon from McMurdo Station, Antarctica, in December 1998 with an expectation of getting up to 2 weeks of continuous data. (AB-033-O)

Long-Duration Balloon program. Steven Peterzen, National Scientific Balloon Facility. The National Scientific Balloon Facility's (NSBF) effort in Antarctica, known as the Long-Duration Balloon (LDB) program, launches high-altitude balloons carrying scientific payloads into the stratosphere. These large-volume (804,199-cubic-meter), helium-filled balloons circumnavigate the continent for up to 24 days. For each circumpolar flight, NSBF performs the launch operations, designs and manages the telemetry links, and then terminates and recovers the flight system. During the 1998–1999 field season, the LDB program will support research by Andrew Lange of the California Institute of Technology and David Rust of Johns Hopkins University. (AB-145-O)

An optical investigation of the genesis of solar activity. David M. Rust, Johns Hopkins University. The Flare Genesis Experiment will use an 80-centimeter telescope to make images and magnetograms of unprecedented resolution (0.2 arcsec) of the solar photosphere and chromosphere while flying from a high-altitude, long-duration balloon around the antarctic continent. The purpose of the experiment is to further understanding on how the energy stored in the Sun's magnetic fields is converted to energetic events such as flares and coronal mass ejections. This experiment can be done only from an antarctic balloon (short of building a large, special-purpose spacecraft) for two reasons. First, continual viewing of the Sun is necessary for periods much exceeding a day, and that can be achieved only at polar sites. Second, to achieve the required resolution, the telescope must be above most of the atmosphere, and LDBs can carry the telescope to that height. This project is jointly sponsored by the National Science Foundation, the National Aeronautics and Space Administration, and the Air Force. (AB-146-O)

Center for Astrophysical Research in Antarctica (CARA)—Administration, Stephan Meyer, University of Chicago. Infrared and submillimeter astronomy has the potential for answering major questions about the formation of the Universe:

• What are the processes by which stars form from interstellar gas?
• How did the planets form?
• What was the nature of primeval galaxies?
• How was matter and energy distributed in the early Universe?

Because of the cold temperatures and the near absence of water vapor in the atmosphere above the polar plateau, the infrared skies are consistently clearer and darker in Antarctica than anywhere else on Earth. These conditions enable researchers to make measurements that would be extremely difficult or impossible from other sites.

To capitalize on these advantages, in 1991 the University of Chicago and several collaborating institutions established the Center for Astrophysical Research in Antarctica (CARA), which is one of 24 Science and Technology Centers funded by the National Science Foundation. To support its scientific mission, CARA is working to establish an observatory at the South Pole and to investigate the conditions for astronomy at the South Pole and other sites on the polar plateau. Currently, CARA supports research using three major telescope facilities.

• The Astronomical Submillimeter Telescope/Remote Observatory (AST/RO) project uses a 1.7-meter-diameter telescope to survey interstellar gas in the galactic plane, the galactic center, and the Magellanic Clouds.
• The South Pole Infrared Explorer (SPIREX) project uses a 0.6-meter-diameter telescope to observe distant galaxies, cool stars, and heavily obscured star-forming regions.
• The Cosmic Background Radiation Anisotropy (COBRA) project helps researchers test current theories of the origin of the Universe.

In addition to projects using these three telescopes, CARA's Advanced Telescopes Project collects data on the quality of polar plateau sites for astronomical observations and to plan for future telescopes and facilities.

Projects and principal investigators included as part of CARA are the following.

• CARA-wide operations and activities (Stephan Meyer, University of Chicago) (AC-132-A).
• The AST/RO project, which will receive new array receivers to permit rapid mapping of chemical species (Antony Stark, Smithsonian Institution) (AC-132-B).
• The SPIREX project, which will be revitalized during the 1998–1999 field season with a state-of-the-art array to make possible wide-field surveys of star formation in our Galaxy and in the Magellanic Clouds at wavelengths between 2 and 5 micrometers (Bob Lowenstein, University of Chicago) (AC-132-C).
• The Advanced Telescopes Project (Bob Lowenstein, University of Chicago) (AC-132-E).
• Activities of the COBRA project related to preparation for deployment of the Viper telescope, a new, 2-meter class telescope that will extend the observations now being made with the 0.75-meter Python telescope to structures in the cosmic microwave background having smaller angular scales (Jeffrey Peterson, Carnegie-Mellon University) (AC-132-F).

Besides making measurements of "seeing" quality using the SPIREX telescope, the Advanced Telescopes Project also supports a number of other efforts including wide-field cameras, a near-infrared sky brightness monitor (in collaboration with the University of New South Wales), and an instrument for monitoring mid-infrared sky brightness and transmission (in collaboration with the National Aeronautics and Space Administration's Goddard Space Flight Center).

The operation of an extremely-low-frequency/very-low-frequency radiometer at Arrival Heights, Antarctica. A.C. Fraser-Smith, Stanford University. During the 1998–1999 field season, we will continue to operate an extremely-low-frequency and very-low-frequency (ELF/VLF) radiometer at McMurdo Station, Antarctica, to monitor radio noise from natural sources such as thunderstorms. The Arrival Heights site is one of a network of eight such radiometers operated by Stanford University for the Office of Naval Research. Characterizing the possible sources of radio interference is important for operational purposes. Additionally, because the variations in global noise reflect variations in global thunderstorm activity, they can provide information on global climate change. The antarctic site was chosen about 15 years ago because it is unusually free from manmade electromagnetic interference. The ELF/VLF record of data collected by this project now extends unbroken for more than 10 years. (AO-100-O)

Magnetometer data acquisition at McMurdo and Amundsen–Scott South Pole Stations. Louis Lanzerotti, AT&T Bell Laboratories, and Alan Wolfe, New York City Technical College. Magnetometers installed at selected sites in both polar regions continue to measure the magnitude and direction of variations in Earth's magnetic field in the frequency range from 0 to about 0.1 hertz. We will measure these variations using magnetometers installed at conjugate sites in the Northern and Southern Hemispheres, specifically at McMurdo and Amundsen–Scott South Pole Stations, Antarctica, and at Iqaluit, Northwest Territories, Canada. We are also analyzing these data in association with similar data acquired from several automatic geophysical observatories that are part of the polar experiment network for geophysical upper-atmosphere investigations (PENGUIN) program (AO-112-O). Using these systems, we gather data on the coupling of the interplanetary medium into the dayside magnetosphere, including the magnetospheric cusp region, as well as the causes and propagation of low-frequency hydromagnetic waves in the magnetosphere. Because of unique climatic conditions at the South Pole, we are also able to correlate optical measurements with particle-precipitation measurements and with hydromagnetic-wave phenomena recorded by the magnetometer. (AO-101-O)

An investigation of magnetospheric boundaries using ground-based induction magnetometers operated at manned stations as part of an extensive ground array. Roger Arnoldy, University of New Hampshire. We operate an array of induction-coil magnetometers located at high geomagnetic latitudes in the Arctic and Antarctic, and we analyze the data collected. The sites, located at Sondre Stromfjord, Greenland, and Iqaluit, Northwest Territories, Canada, in the Arctic and at Amundsen-Scott South Pole and McMurdo Stations in the Antarctic, complement similar magnetometers in the U.S. and British automatic geophysical observatory (AGO) networks and the MACCS array in Canada. The measurements of magnetic pulsations at these high geomagnetic latitudes are used to study the plasma physics of some of the important boundaries of the magnetosphere, particularly those surrounding the area through which the solar wind enters the magnetosphere and where the magnetosphere transfers the solar wind's energy to the Earth's atmosphere in the form of aurora and similar phenomena. This project is jointly supported by the U.S. Arctic and Antarctic Programs. (AO-102-O)

Antarctic auroral imaging. Stephen Mende, University of California, Berkeley; Space Sciences Laboratory. In the past, space satellites have performed detailed exploration of the magnetosphere, and the average distribution of the energetic particle plasma content of the magnetosphere has been mapped. This form of measurement is unsuitable, however, for observing the dynamic behavior of the magnetosphere. Auroral phenomena are produced when particles from the magnetosphere precipitate into the atmosphere causing the atmosphere to fluoresce. Because particles tend to travel along the magnetic field line, the aurora can be regarded as a two-dimensional projection of the three-dimensional magnetospheric regions. Thus, observing the morphology of the aurora and its dynamics provides an important way to study the dynamics of the three-dimensional magnetosphere. This method requires knowledge of which type of auroras represent which energy of precipitation and their connection to the various regions of the magnetosphere.

Amundsen–Scott South Pole Station is uniquely situated for optical observations of polar aurora because during the winter, the aurora can be monitored 24 hours a day unlike most other places, where the sky becomes too bright near local mid-day. An intensified optical, all-sky imager, operating in two parallel wavelength channels—4,278 and 6,300 Ångstroms—will be used to record digital and video images of aurora. These wavelength bands allow us to discriminate between more or less energetic electron auroras and other precipitation. From South Pole Station, we can observe the polar cap and cleft regions by measuring auroral-precipitation patterns and interpreting the results in terms of coordinated observations of magnetic, radio-wave absorption images and high-frequency, coherent-scatter radar measurements. Through this investigation, we hope to learn about the sources and energization mechanisms of auroral particles in the magnetosphere and other forms of energy inputs into the high-latitude atmosphere. (AO-104-O)

A study of very high latitude geomagnetic phenomena. Vladimir Papitashvili, University of Michigan. Our project is a continuation of a joint U.S.–Russian program to operate an array of high-latitude automated magnetometers in Antarctica. We will use these instruments to investigate the polar cap current systems in the Earth's magnetosphere. The antarctic continent is uniquely suited to these investigations because it is the only land mass at very high latitudes and is, therefore, an excellent and stable location for an array of magnetometers. These investigations are particularly important to the understanding of the coupling of energy and momentum from the solar wind to the magnetosphere, ionosphere, and upper atmosphere. The data will also be extremely useful for analyses coordinated with a number of satellite-based experiments that are currently in progress or are planned for the near future. The specific tasks to be undertaken include design improvements in the digital geomagnetic data-acquisition systems at Vostok and Mirnyy and the continued operations and maintenance of autonomous stations along the Russian traverse route to Vostok. One improvement will be to add a satellite data-transmission capability at Vostok so that a polar cap magnetic index will be available in near real-time for space weather and research applications. (AO-105-O)

Study of polar stratospheric clouds by lidar. Guido Di Donfrancesco, Instituto De Fisica Dell'Atmosfere, Rome, Italy. In cooperation with the U.S. Antarctic Program and in collaboration with the University of Wyoming (AO-131-O), we will use lidar to study the polar stratospheric clouds (PSCs), their formation, evolution, and other peculiar characteristics. Continuous lidar observations permit studies of PSCs and stratospheric aerosol and the thermal behavior and dynamics of the atmosphere above McMurdo Station. (AO-107-O)

Extremely-low-frequency/very-low-frequency (ELF/VLF) waves at the South Pole. Umran S. Inan, Stanford University. Advancing our understanding of the electrodynamic coupling of upper atmospheric regions and refining our quantitative understanding of the energy transport between the magnetosphere and the ionosphere are two important objectives of the U.S. Antarctic Program's automatic geophysical observatory program. Particle precipitation driven by extra-low-frequency/very-low-frequency (ELF/VLF) waves has a part in transporting and accelerating magnetospheric and ionospheric plasmas, processes that result from a variety of physically different wave-particle interactions. Because measuring ELF/VLF waves from multiple sites provides a powerful tool for remote observations of magnetosphere processes, we maintain a system at Amundsen–Scott South Pole Station that measures magnetospheric ELF/VLF phenomena; data from this system are correlated with data from the automatic geophysical observatory system. (AO-108-O)

South Pole Air Shower Experiment–2. Thomas Gaisser, University of Delaware. The South Pole Air Shower Experiment–2 (SPASE-2) is a sparsely filled array of 120 scintillation detectors spread over 15,000 square meters at South Pole. It detects energetic charged particles (mostly electrons), which are produced in the upper atmosphere by cosmic rays. The array also includes a subarray, called VULCAN, of nine photodetectors to detect Cherenkov radiation produced by the same showers high in the atmosphere.

Our experiment has several goals, the most important of which is to determine the elemental composition of the primary cosmic rays at energies above approximately 100 teraelectronvolts. To do this, SPASE-2 works in conjunction with the Antarctic Muon and Neutrino Detector Array (AMANDA), which has several hundred optical detectors so deep in the ice sheet that the only products of the cosmic ray interactions that can be seen by AMANDA are muons. The ratio of muons to electrons in a cosmic ray shower depends on the mass of the original primary cosmic ray nucleus. In addition, in showers also detected with VULCAN, two other ratios that also depend on primary mass can be determined. Interpretation of the combined data will lead to a determination of the relative importance of different groups of nuclei in the cosmic radiation in an energy region not accessible to direct measurement. This, in turn, will shed light on the origin and mechanisms of acceleration of this extremely energetic, naturally occurring radiation. This project is cooperative with the University of Leeds in the United Kingdom. (AO-109-O)

High-latitude antarctic neutral mesospheric and thermospheric dynamics and thermodynamics. Gonzalo Hernandez, University of Washington. The temperature and windspeed of the atmosphere can be deduced by measuring the emission spectra of certain trace gases, especially the spectra of those that are confined to fairly narrow altitude regions. We use a Fabry-Perot infrared interferometer located at Amundsen-Scott South Pole Station, Antarctica, to look at the band spectra of several trace species, most importantly the hydroxyl radical (OH), in orthogonal directions. By determining the doppler shift of the lines, researchers can measure the winds. The brightness and line ratios within the bands provide density and temperature information. The OH in the atmosphere is primarily found in a narrow band near 90 kilometers altitude. The fact that the measurements are being made at the axis of rotation of Earth significantly limits the types of planetary waves, thus simplifying the study of the large-scale dynamics of the atmosphere. (AO-110-O)

Riometry in Antarctica and conjugate regions. Theodore J. Rosenberg and Allan T. Weatherwax, University of Maryland at College Park. To continue and expand the study of the upper atmosphere, especially auroral phenomena, using photometry and riometric techniques, we have developed a new imaging riometer (relative ionospheric opacity meter) system called IRIS (imaging riometer for ionospheric studies). The first two IRISs were installed at Amundsen–Scott South Pole Station and Sondre Stromfjord, Greenland. A third IRIS has been installed at Iqiluit, Northwest Territories, Canada, which is the magnetic conjugate to South Pole. Broadbeam riometers also operate at several frequencies at South Pole, McMurdo, and Iqiluit; auroral photometers operate at South Pole and McMurdo. These instruments constitute a unique network with which to study auroral effects in both magnetic hemispheres simultaneously. (AO-111-O)

Polar experiment network for geophysical upper-atmosphere investigations (PENGUIN). Theodore Rosenberg, University of Maryland at College Park. A consortium of U.S. and Japanese scientists will use a network of six automatic geophysical observatories (AGOs), established on the east antarctic polar plateau and equipped with suites of instruments to measure magnetic, auroral, and radiowave phenomena. The AGOs, which are totally autonomous, operate year round and require only annual austral summer service visits. We will use these arrays of instruments, along with measurements made at select manned stations, to study the energetics and dynamics of the high-latitude magnetosphere on both large and small scales. The research will be carried out along with in situ observations of the geospace environment by spacecraft, in close cooperation with other nations working in Antarctica and in cooperation with conjugate studies performed in the Northern Hemisphere.

The data obtained from AGOs help researchers understand the Sun's influence on the structure and dynamics of the Earth's upper atmosphere. The ultimate objective of this research into how the solar wind couples with the Earth's magnetosphere, ionosphere, and thermosphere is to be able to predict solar-terrestrial interactions that can interfere with long-distance phone lines, power grids, and satellite communications. (AO-112-O)

All-sky-camera measurements of the aurora australis from Amundsen–Scott South Pole Station. Masaki Ejiri, National Institute of Polar Research, Japan. Amundsen–Scott South Pole Station, located at the south geographic pole, is a unique platform from which to undertake measurements of the polar ionosphere. Because of the configuration of the geomagnetic field in the Southern Hemisphere, the station is situated in such a way that dayside auroras can be viewed for several hours each day. Research has shown that they are caused by precipitation of low-energy particles, which enter the magnetosphere by means of the solar wind. Since 1965, data have been acquired at the South Pole using a film-based, all-sky-camera system. Using advanced technology, we can now digitize photographic images and process large amounts of information automatically. Besides continuing to acquire 35-millimeter photographic images with the all-sky-camera system, U.S. and Japanese researchers will collaborate and use an all-sky-camera processing system developed at Japan's National Institute of Polar Research to analyze data. This system displays data in a geophysical coordinate framework and analyzes images over short and long intervals not possible with individual photographic images. The data will be used to investigate dayside auroral structure, nightside substorm effects, and polar-cap arcs. These studies can also be used to obtain further insight into the physics of the magnetosphere, the convection of plasma in the polar cap, and solar winds in the thermosphere. (AO-117-O)

Solar and heliosphere studies with antarctic cosmic-ray observations. John Bieber, University of Delaware. Neutron monitors in Antarctica provide a vital three-dimensional perspective on the anisotropic flux of cosmic rays that continuously bombards Earth. At McMurdo and Amundsen–Scott South Pole Stations, year-round observations will continue for cosmic rays with energies in excess of 1 billion electronvolts. These data will advance our understanding of a variety of fundamental plasma processes occurring on the Sun and in interplanetary space. Neutron-monitor records, which began in 1960 at McMurdo Station and 1964 at South Pole Station, will play a crucial role in efforts to understand the nature and causes of cosmic-ray and solar-terrestrial variations occurring over the 11-year sunspot cycle, the 22-year Hale cycle, and even longer timescales. At the other extreme, we will study high time-resolution (10-second) cosmic-ray data to determine the three-dimensional structure of turbulence in space and to understand the mechanism by which energetic charged particles scatter in this turbulence. (AO-120-O)

Rayleigh and sodium lidar studies of the troposphere, stratosphere, and mesosphere at McMurdo and Amundsen-Scott South Pole Stations. Jim Abshire, National Aeronautics and Space Administration, Goddard Space Flight Center. The automated geophysical observatory (AGO) lidar is an ongoing, National Aeronautics and Space Administration (NASA) funded project to develop and demonstrate a compact, low-power, and autonomous atmospheric lidar for operation in the U.S. Antarctic Program's AGOs deployed to various locations in Antarctica. The primary science mission of AGO lidar is detecting, monitoring, and profiling polar stratospheric clouds (PSCs). These clouds form in the extremely cold polar stratosphere during the austral winter, and a particular type of PSC (type 1) has been implicated in the annual springtime destruction of stratospheric ozone. A secondary science mission is long-term continuous monitoring of atmospheric transmission and backscatter from the surface. These data will be compiled into a database that will provide statistics on atmospheric conditions for the Geoscience Laser Altimeter System (GLAS).

The AGO lidar has redundant laser diode transmitters operating at 670 nanometers, producing 500-milliwatt peak power pulses, at 1- or 4-microsecond pulse lengths, and a pulse-repetition frequency of 4 kilohertz. The backscattered laser light is collected by a 20-centimeter diameter telescope and detected by all-solid-state single-photon counting modules in a cross-polarized detection scheme. Type 1 PSCs will depolarize incident radiation. Because the laser transmitters in AGO lidar produce highly linearly polarized light, it sends back a depolarization signal (up to several percent) in the backscattered light.

The lidar data are archived in the lidar instruments' own flash memory as well as the optical drive provided by the AGO platform. The AGO lidar also contains its own Argos transmitter, which telemeters at least one atmospheric profile per day back to NASA's Goddard Space Flight Center in Greenbelt, Maryland. (AO-126-O)

Rayleigh and sodium lidar studies of the troposphere, stratosphere, and mesosphere at the Amundsen–Scott South Pole Station. George Papen, University of Illinois. During the 1998–1999 field season, we will continue to operate a sodium resonance lidar at the South Pole to study the vertical structure and dynamics of the atmosphere from the lower stratosphere to the mesopause. During this third year of the project, an iron resonance lidar will be added and will extend the measurements of the dynamics and temperature structure to 100 kilometers altitude. Additionally, an airglow imaging camera will be used to study the horizontal structure. When used in conjunction with the normal balloonborne radio sondes, which are flown regularly from South Pole, the final complement of instruments will provide extensive data on

• the temperature structure from the surface to 100 kilometers altitude;
• the nature of the polar stratospheric clouds, which are important to ozone chemistry;
• the variability and frequency of occurrence of metallic layers in the mesosphere, which play a role in communications as well as chemistry;
• atmospheric gravity waves; and
• many other phenomena, some of which are unique to the South Pole. (AO-127-O)

High-latitude electromagnetic wave studies using antarctic automatic geophysical observatories. James LaBelle, Dartmouth College. At radio frequencies between 0.05 and 5.0 megahertz (MHz), three types of radio phenomena related to auroral origin can be detected: narrowband near 2.8 and 4.2 MHz, broadband noise bursts in the frequency range of 1.4–4.0 MHz, and broadband noise at frequencies below 1 MHz. An accepted physical theory explains the third type, called auroral hiss, but the origins of the other two types are unknown. Although these radio emissions constitute a small fraction of the total energy of the aurora, they may provide important clues to the more energetic processes, analogous to the way in which solar radio emissions are used to infer the processes taking place in the solar corona. Using low-frequency/middle frequency/high frequency receivers, we hope to collect further clues about these emissions from antarctic auroral zone and polar cap sites, taking advantage of radio-quiet antarctic conditions. The receivers will be installed at Amundsen–Scott South Pole Station, in three U.S. automatic geophysical observatories, and in two British automatic geophysical observatories. (AO-128-O)

In situ measurements of polar stratospheric clouds (PSCs) spanning the austral winter and of ozone from late winter to early spring. Terry Deshler, University of Wyoming. The annual stratospheric ozone hole above Antarctica is driven by chlorine compounds that interact on the surfaces of polar stratospheric clouds, which form during the polar winter. Thus, the ozone hole appears in the austral spring, and ozone depletion is much more severe in polar regions than elsewhere. By using balloonborne instruments, we provide detailed information on the actual cloud particles and the distribution of the clouds and the ozone. Our measurements will provide vertical profiles of both the PSCs and ozone, size distributions of the PSC particles, and some information on their composition and physical state (liquid or solid). Our project is enhanced by cooperation with an Italian investigator who operates a lidar system at McMurdo Station. The project contributes to the World Meteorological Organization/UNEP Network for the Detection of Stratospheric Change and the Global Change Initiative. (AO-131-O)

Measurement of stratospheric chlorine monoxide and other trace gases over McMurdo Station in the austral spring. Robert L. de Zafra, University of New York at Stony Brook. Chlorine monoxide (ClO) is a product of the destruction of stratospheric ozone by chlorine, which enters the stratosphere as a result of the breakdown of chlorofluorocarbons (CFCs). ClO, as well as other trace stratospheric gases that contribute to the development of the antarctic ozone hole, can be measured from the ground by millimeter-wave receivers, similar to those used for molecular radio astronomy.

We will continue a decade-long series of such measurements made at McMurdo Station to further understand climate dynamics and phenomena but, more important, to provide a cross calibration of the new Network for the Detection of Stratospheric Change (NDSC) ClO microwave instrument, which has recently been installed nearby at New Zealand's Scott Base. Because the NDSC instruments are being installed at a number of sites worldwide, it is important to provide as much correlative information as possible so that the NDSC can be relied upon in the future to monitor the health of the stratosphere. Our goal is to provide as much continuity as possible between measurements made from 1986 to 1998 with the Stony Brook spectrometer at McMurdo Station and the current and future measurements made by the new NDSC instrument at Scott Base. During the 1998–1999 field season, we will also test a second newly rebuilt and improved spectrometer at McMurdo before final installation at Amundsen–Scott South Pole Station in early 1999. This spectrometer will be used concurrently to measure other species photochemically or dynamically linked to chlorine chemistry in the stratosphere. (AO-137-O)

Trace gas measurements over the South Pole using millimeter-wave spectroscopy. Robert L. de Zafra, State University of New York at Stony Brook. Many atmospheric gases radiate energy in the millimeter-wavelength region of the radio spectrum, and each species has its own unique spectrum. The shape of each individual species' spectrum provides information on the temperature and pressure of the gas; thus, one can use the millimeter-wave spectrum of the atmosphere to determine the relative abundances and height distribution of a number of trace species. In our investigation, we will use a millimeter spectroscope to monitor ozone, carbon monoxide, nitrous oxide, nitric acid, water vapor, and nitrogen dioxide above South Pole, Antarctica, over the period of a year. Several of these gases have important roles in the formation of the annual antarctic ozone hole, and others, particularly water vapor and carbon monoxide, can provide information about the dynamics, particularly the vertical transport, of the upper stratosphere and mesosphere. (AO-138-O)

Cosmology from Dome-C in Antarctica. Lucio Piccirillo, Bartol Research Institute, University of Delaware. The thermal cosmic microwave background radiation (CMBR) left over from the Big Bang carries the only information available on the distribution of matter in the very early Universe. As part of an international collaboration (the United States, Italy, and France), we will measure the anisotropy of the CMBR from Concordia Station, the new French/Italian station on Dome C in Antarctica. Concordia is one of the highest and coldest sites presently occupied in Antarctica. Because of the extreme cold, the atmosphere contains very little water vapor, making Concordia a potentially superb place from which to make CMBR anisotropy measurements. Evaluation of the site for future use is also a major goal of this project. (AO-140-O)

Ground-based infrared measurements in the Antarctic. Frank J. Murcray and Ronald Blatherwick, University of Denver. For this project, we will use an infrared (IR) interferometer to monitor selected trace constituents in the atmosphere above Amundsen–Scott South Pole and McMurdo Stations. The measurements will be made in two modes: absorption and emission. The absorption mode uses the Sun, shining through the atmosphere, as a source of IR radiation and allows us to measure a number of trace constituents, especially during the local springtime when the antarctic ozone hole is forming. The emission mode, using radiation emitted by the atmospheric gases themselves, is less sensitive than the absorption mode but does allow critical measurements during the long, dark polar night, when the chemistry that sets the stage for the springtime ozone depletion is taking place. The compounds we will measure include hydrogen chloride, nitric acid, chlorofluorocarbon-11 and -12, nitrous oxide, methane, ozone, and chlorine nitrate. Each of these gases has a role in ozone depletion, and several are also important greenhouse gases. This project is jointly funded by the National Science Foundation's Office of Polar Programs and Division of Atmospheric Sciences and also by the National Aeronautic and Space Administration's Office of Earth Sciences and Applications. (AO-148-O)

Antarctic halos and ice crystals. Walter Tape, University of Alaska Fairbanks. Our project is an experimental and theoretical study of ice crystals in the antarctic atmosphere and the halos that they produce. For reasons that are not currently known, the antarctic interior experiences more frequent and better developed halos than any other location on Earth. Our objectives are to observe natural halos at Amundsen–Scott South Pole Station and to sample ice crystals to validate computer models of light refraction and reflection in ice crystals. Such models have the potential for the remote sensing of atmospheric conditions. Controlled experiments, such as seeding the atmosphere with dry ice, will produce artificially generated but simple and well-formed single-species crystals. Our research provides a unique mechanism for examining the crystal growth and evolution process in the natural atmosphere. By observing halos through polarizing filters, we will also be able to examine the atmospheric ice-crystal orientation, shape, and size. The results of our project will advance our understanding of why well-formed ice crystals grow in the antarctic atmosphere but are not generally observed elsewhere. (AO-208-O)

Continued study of the Earth's ultra-low-frequency wave environment using induction antennas on the British Antarctic Survey's automatic geophysical observatories in Antarctica. Mark J. Engebretson, Augsburg College. Earth's magnetic field undergoes variations on many timescales. The low-amplitude fluctuations that have periods of a few tenths of a second to a few seconds, called micropulsations, are the result of motion in the magnetosphere such as waves on the magnetopause or other surfaces. Because most of the magnetosphere is connected to the surface by magnetic field lines that have their footprints at high geomagnetic latitude, the large-scale dynamics of the space environment can best be studied from the polar regions.

Now, an extensive antarctic array of magnetometers supports research in this area. In particular, our team has installed magnetometers in the British Antarctic Survey automatic geophysical observatories and has access to data from other similar instruments. The data gathered will provide additional insight into how solar activity affects Earth's environment as well as humanity's technical systems and will increase the worldwide space data pool. (AO-273-O)