South Pole Station In Antarctica Research Articles

Interhemispheric Comparisons of Large Nighttime Magnetic Perturbation Events Relevant to GICs

AbstractNearly all studies of impulsive magnetic perturbation events (MPEs) with large magnetic field variability (dB/dt) that can produce dangerous geomagnetically induced currents (GICs) have used data from the Northern Hemisphere. Here we present details of four large‐amplitude MPE events (|ΔBx| > 900 nT and |dB/dt| > 10 nT/s in at least one component) observed between 2015 and 2018 in conjugate high‐latitude regions (65–80° corrected geomagnetic latitude), using magnetometer data from (1) Pangnirtung and Iqaluit in eastern Arctic Canada and the magnetically conjugate South Pole Station in Antarctica and (2) the Greenland West Coast Chain and two magnetically conjugate chains in Antarctica, AAL‐PIP and BAS LPM. From one to three different isolated MPEs localized in corrected geomagnetic latitude were observed during three premidnight events; many were simultaneous within 3 min in both hemispheres. Their conjugate latitudinal amplitude profiles, however, matched qualitatively at best. During an extended postmidnight interval, which we associate with an interval of omega bands, multiple highly localized MPEs occurred independently in time at each station in both hemispheres. These nighttime MPEs occurred under a wide range of geomagnetic conditions, but common to each was a negative interplanetary magnetic field Bz that exhibited at least a modest increase at or near the time of the event. A comparison of perturbation amplitudes to modeled ionospheric conductances in conjugate hemispheres clearly favored a current generator model over a voltage generator model for three of the four events; neither model provided a good fit for the premidnight event that occurred near vernal equinox.

Data reduction pipeline for MOF-based synoptic telescopes

There are strong scientific cases and practical reasons for building ground-based solar synoptic telescopes. Some issues, like the study of solar dynamics and the forecasting of solar flares, benefit from the 3D reconstruction of the Sun’s atmosphere and magnetic field. Others, like the monitoring and prediction of space weather, require full disk observations, at the proper sampling rate, combining H-alpha images and Doppler velocity and magnetic field. The synoptic telescopes based on Magneto Optical Filters (MOF) using different lines are capable of measuring the line-of-sight Doppler velocity and magnetic field over the full solar disk at different ranges of height in the Sun’s photosphere and low chromosphere. Instruments like the MOTH (Magneto-Optical filters at Two Heights), using a dual-channel based on MOFs operating at 589.0 nm (Na D2line) and 769.9 nm (K D1line), the VAMOS instrument (Velocity And Magnetic Observations of the Sun), operating at 769.9 nm (K D1 line), and the future TSST (Tor Vergata Synoptic Solar Telescope), using a dual-channel telescope operating at 656.28 nm (H-alpha line) and at 769.9 nm (K D1 line), allow to face both aspects, the scientific and the operative related to Space Weather applications. The MOTH, VAMOS and TSST data enable a wide variety of studies of the Sun, from seismic probing of the solar interior (sound speed, rotation, details of the tachocline, sub-surface structure of active regions), to the dynamics and magnetic evolution of the lower part of the solar atmosphere (heating of the solar atmosphere, identification of the signatures of solar eruptive events, atmospheric gravity waves, etc.), to the 3D reconstruction of the solar atmosphere and flare locations. However, the use of MOF filters requires special care in calibrating the data for scientific or operational use. This work presents a systematic pipeline that derives from the decennial use of MOF’s technology. More in detail, the pipeline is based on data reduction procedures tested and validated on MOTH data acquired at Mees Solar Observatory of the University of Hawaii Haleakala Observatories and at South Pole Solar Observatory (SPSO), at the Amundsen-Scott South Pole Station in Antarctica, during Antarctica Summer Campaign 2016/17.

Characteristics of immersion freezing nuclei at the South Pole station in Antarctica

Abstract. The effectiveness of aerosols as immersion freezing nuclei at the South Pole station was investigated during January and February 2009 using the FRIDGE-TAU. The analysis consisted of testing the freezing temperature of about 100–130 drops per sample containing aerosols collected at ground level and on a balloon lifted to different heights. All the drops froze between −18 °C and −27 °C. The temperature in which 50 % of the drops froze occurred at −24 °C, while nuclei concentration of 1 L−1 at −23 °C was calculated. Meteorological conditions such as wind speed, ice precipitation as well as the trajectories of the air masses affected the ice nuclei concentrations. Higher concentrations were observed on days when the winds were stronger or when the air mass originated from the sea.

The 10 Meter South Pole Telescope

ABSTRACTThe South Pole Telescope (SPT) is a 10 m diameter, wide-field, offset Gregorian telescope with a 966 pixel, multicolor, millimeter-wave, bolometer camera. It is located at the Amundsen-Scott South Pole station in Antarctica. The design of the SPT emphasizes careful control of spillover and scattering, to minimize noise and false signals due to ground pickup. The key initial project is a large-area survey at wavelengths of 3, 2, and 1.3 mm, to detect clusters of galaxies via the Sunyaev-Zel’dovich effect and to measure the small-scale angular power spectrum of the cosmic microwave background (CMB). The data will be used to characterize the primordial matter power spectrum and to place constraints on the equation of state of dark energy. A second-generation camera will measure the polarization of the CMB, potentially leading to constraints on the neutrino mass and the energy scale of inflation.

Research Spotlight: Auroral emissions reach ground level

Earth's auroral electrons radiate some of their energy in radio waves. Theories of the mechanism for emission of this radiation, known as auroral kilometric radiation (AKR), suggest that this radiation propagates away from Earth and cannot be detected at ground level. However, LaBelle and Anderson present the first evidence that AKR does penetrate to ground level. On three occasions in July 2004 the researchers detected radio emissions that appeared to be AKR at the South Pole Station in Antarctica. They compared these emissions with AKR emissions detected simultaneously by the U.S.‐Japanese Geotail satellite and found that they had the same frequency structure, suggesting that the emissions detected at ground level were indeed AKR. (Geophysical Research Letters, doi:10.1029/2010GL046411, 2011)

Twenty-two years of ozonesonde measurements at the South Pole

Since 1986, the Earth System Research Laboratory and its predecessors have been making weekly balloon ozone soundings at the South Pole Station in Antarctica. During the springtime ozone hole period, the sounding frequency is increased to 2–3 per week. The 2007 springtime minimum total column ozone at South Pole was 125 Dobson units, with the layer between 14 and 21 km showing a typical 95% loss of ozone. In contrast, the 2006 minimum total column ozone was 93 Dobson units and showed 99% ozone destruction in the 14–21 km layer. Owing to variations in meteorology and stability of the polar vortex, year to year variations in the severity of the ozone hole of this magnitude are expected. Analysis of the ozone loss rate in September indicates large interannual variability suggesting a dynamic component. Detailed analysis of the 22-year record is used to search for early signs of the beginning of ozone hole recovery. The conclusion is that up to the year 2007, no definitive signs of the beginning of ozone hole recovery have been detected at South Pole Station.

Sea ice surface temperature product from MODIS

Global sea ice products are produced from the Earth Observing System (EOS) Moderate Resolution Imaging Spectroradiometer (MODIS) onboard both the Terra and Aqua satellites. Daily sea ice extent and ice surface temperature (IST) products are available at 1- and 4-km resolution. Validation activities during the "cold period" (when meltwater is generally not present) in the Northern Hemisphere, defined here as October through May, have been undertaken to assess the accuracy of the 1-km resolution MODIS IST algorithm and product. Validation was also done at the South Pole station in Antarctica. In the Arctic Ocean, near-surface air temperatures from the National Oceanic and Atmospheric Administration (NOAA) National Ocean Service (NOS) Center for Operational Oceanographic Products and Services (CO-OPS) Alaska tide stations and from drifting buoys from the North Pole Environmental Observatory (NPEO) buoy program were compared with MODIS-derived ISTs. Using the standard MODIS sea ice product, which utilizes the MODIS cloud mask, results show a bias (mean error) of -2.1 K and a root mean square (RMS) error of 3.7 K. The negative bias means that the satellite retrieval is less than the air temperature. With the bias removed, the RMS error is 3.0 K. When additional visual cloud screening is performed to eliminate MODIS pixels thought to be contaminated by fog, results improved, with a subset of the larger dataset showing a bias of -0.9 K and an RMS error of 1.6 K. Uncertainties would be reduced in the Arctic Ocean dataset if the skin temperature of the sea ice were reported instead of the near-surface air temperatures. With the bias removed, the RMS error for the Arctic Ocean dataset is 1.3 K. Results from the South Pole station in Antarctica show that under clear skies as determined using lidar measurements, the MODIS ISTs are also very close to those of the near-surface air temperatures with a bias of -1.2 K and an RMS error of 1.7 K. With the bias removed, the RMS error for the South Pole dataset is 1.2 K. Thus, the accuracy (RMS error) of the IST measurement is 1.2-1.3 K. It is not possible to obtain an accurate IST from MODIS in the presence of even very thin clouds or fog, and this is the main limitation of the MODIS ice surface temperature product. MODIS sea ice products may be ordered from the National Snow and Ice Data Center in Boulder, CO.

Cosmic Microwave Background Anisotropy Measurement from Python V

We analyze observations of the microwave sky made with the Python experiment in its fifth year of operation at the Amundsen-Scott South Pole Station in Antarctica. After modeling the noise and constructing a map, we extract the cosmic signal from the data. We simultaneously estimate the angular power spectrum in eight bands ranging from large (l ~ 40) to small (l ~ 260) angular scales, with power detected in the first six bands. There is a significant rise in the power spectrum from large to smaller (l ~ 200) scales, consistent with that expected from acoustic oscillations in the early universe. We compare this Python V map to a map made from data taken in the third year of Python. Python III observations were made at a frequency of 90 GHz and covered a subset of the region of the sky covered by Python V observations, which were made at 40 GHz. Good agreement is obtained both visually (with a filtered version of the map) and via a likelihood ratio test.

Anisotropy in the Cosmic Microwave Background at Degree Angular Scales: Python V Results

Observations of the microwave sky using the Python telescope in its fifth season of operation at the Amundsen-Scott South Pole Station in Antarctica are presented. The system consists of a 0.75 m off-axis telescope instrumented with a HEMT amplifier-based radiometer having continuum sensitivity from 37-45 GHz in two frequency bands. With a 0.91 deg x 1.02 deg beam the instrument fully sampled 598 deg^2 of sky, including fields measured during the previous four seasons of Python observations. Interpreting the observed fluctuations as anisotropy in the cosmic microwave background, we place constraints on the angular power spectrum of fluctuations in eight multipole bands up to l ~ 260. The observed spectrum is consistent with both the COBE experiment and previous Python results. There is no significant contamination from known foregrounds. The results show a discernible rise in the angular power spectrum from large (l ~ 40) to small (l ~ 200) angular scales. The shape of the observed power spectrum is not a simple linear rise but has a sharply increasing slope starting at l ~ 150.

Polar thermospheric response to solar magneticcloud/coronal mass ejection interactions with themagnetosphere

The Solar Magnetic Cloud (SMC)/Coronal Mass Ejection (CME) event of January1997 triggered auroral displays in all sectors of the auroral oval as well as in the polar cap region.Near infrared emissions from these auroras were recorded simultaneously in the night sector overSondrestromfjord (Sonde), Greenland, in the day sector over Longyearbyen, Svalbard and in thepolar cap region over Eureka, Canada. The spectral distributions of these emissions indicateprecipitation of electrons with average energy ( E AV) of (500±100) eV,dissipating most of their energy around (180±20) km height ( h max) in thethermosphere. These findings are consistent with the concurrent auroral ionization profilesrecorded by the Incoherent Scatter Radar soundings at Sonde. In contrast, most of the nighttimeauroras, not related to SMC/CME events, are excited by electrons with E AV > a few keV and peak in the lower thermosphere with h max around 110 km.Similarly, normal dayside cusp auroras and polar cap drizzle excited emissions emanate from theupper thermosphere above 200 km altitude. SMC/CME related auroras were also observed inOctober 1995 at Sonde, and in May 1996 as well as in May 1997 at the South Pole Station inAntarctica. Spectral characteristics, and hence E AV and h max, of all these other SMC/CME related auroras, are similar to those of the January 1997event. These observations suggest that during a significant part of the period when SMC/CMEplasmas and fields interact with the magnetosphere, relatively low energy electrons precipitate inthe thermosphere. Such SMC/CME triggered auroras interact with the middle thermosphereconstituents in the 160–200 km height region. The latter region is inaccessible for remote sensingits composition and thermodynamics in normal auroras, which generally peak at lower heights; theSMC/CME events provide the opportunity for such investigations.

Anisotropy in the Microwave Sky at 90 GH[CLC]z[/CLC]: Results from Python II

We report on additional observations of degree-scale anisotropy at 90 GHz from the Amundsen-Scott South Pole Station in Antarctica. Observations during the first season with the Python instrument yielded a statistically significant sky signal with an amplitude of ΔT/T ~ 3.5 × 10-5 for a Gaussian autocorrelation function model with a coherence angle θc = 1°. In this Letter we report the confirmation of that signal with data taken in the second year, and on results from an interleaving set of fields. Using the entire data set, we find ΔT/T = C1/20 = 2.8+ 1.1−0.7 × 10-5 for the Gaussian autocorrelation model mentioned above, and ΔT/T = [le(le + 1)Cl/(2π)]1/2 = 2.1+ 0.7−0.5 × 10-5 for a band power estimate, where le = 93 is the effective center of our window function. The stated errors represent a 68% confidence interval in the likelihood added in quadrature with a 20% calibration uncertainty.

Six-hour zonally symmetric tidal oscillations of the winter mesopause over the South Pole Station

Four complete cycles of a 6-h quasi-mono-chromatic variation in OH Meinel (3,1) and (4,2) band airglow brightness ( I) and rotational distribution temperature ( T) were observed with a near infrared (1.0–1.7 μ) Michelson Interferometer operating at the South Pole Station in Antarctica. The simultaneous occurrence of a quasi-periodic variation in I and T suggests the presence of a coherent wave phenomenon in the mesopause region. A power spectral density analysis of a continuous 24-h recording of I and T on 24 May 1992, indicates a 6 ± 1-h period oscillation (Sivjee et al., EOS 74 (Suppl.), 48,5A 11A-10 1993a). The propagation of 6-h wave-like disturbances in the high latitude winter mesopause is substantiated by more recent extended-period airglow measurements at ∼81.6°N latitude around Eureka, Canada (Sivjee et al, EOS 74 (Suppl.), 43, 5A 21A-4, 1993b; Sivjee et al, Planet. Space Sci. 42, in press, 1994). The period and coherency of the oscillation point to a tidal origin, while its occurrence at a geographic pole suggests a zonally symmetric tide. Unlike the globally dominant migrating tides, and other zonally propagating tides, for which the quantities that generate airglow fluctuations vanish at the pole, the 6-h zonally symmetric standing tide has its maximum amplitude in these quantities at the poles. To examine whether the observed airglow variations were consistent with a zonally symmetric non-migrating tide, comparisons with airglow theory were made in terms of Krassovsky's ratio ( Ann. Geophys. 28, 739, 1972) (the ratio of the fractional change in brightness to the fractional change in temperature). The observed value was 9 ± 3 for amplitude and 30° ± 15° for phase, with I leading T. The agreement with the predicted amplitudes is good for the modes which are sharply peaked near the pole. The predicted phase of I relative to T is not as large as the observed value, but is in the right sense and a mixture of modes could readily account for the larger observed phase. The latter is consistent with the predicted phase at the 95% confidence level. The magnitude of the predicted Krassovsky's ratio for a 6-h period gravity wave is reasonably close to the observed value. However, we rule out a gravity wave source because the predicted phase indicates that the temperature fluctuation leads the brightness fluctuation, opposite to what is observed, and the absolute difference between the observed and predicted phase is quite large. We conclude that considerations based on tidal theory and a model of wave driven fluctuations in OH airglow strongly favor an interpretation in terms of a zonally symmetric tide over zonally propagating tides and gravity waves.