Solar rotation, 1966–1978

Photospheric and chromospheric spectroscopic Doppler rotation rates for the full solar disk are analyzed for the period July, 1966 to July, 1978. An approximately linear secular increase of the equatorial rate of 3.7% for these 12 years is found (in confirmation of Howard, 1976). The high latitude rates above 65 ° appear to vary with a peak-to-peak amplitude of 8%, or more, phased to the sunspot cycle such that the most rapid rotation occurs at, or following, solar maximum. The chromosphere, as indicated by H, has continued to rotate on the average 3% faster than the photosphere agreeing with past observations. Sources of error are discussed and evaluated.Operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation.     

Sunspots with the Strongest Magnetic Fields

The strongest observed solar magnetic fields are found in sunspot umbrae and associated light bridges. We investigate systematic measurements of approximately 32 000 sunspot groups observed from 1917 through 2004 using data from Mt. Wilson, Potsdam, Rome and Crimea observatories. Isolated observations from other observatories are also included. Corrections to Mt. Wilson measurements are required and applied. We found 55 groups (0.2%) with at least one sunspot with one magnetic field measurement of at least 4000 G including five measurements of at least 5000 G and one spot with a record field of 6100 G. Although typical strong-field spots are large and show complex structure in white light, others are simple in form. Sometimes the strongest fields are in light bridges that separate opposite polarity umbras. The distribution of strongest measured fields above 3 kG appears to be continuous, following a steep power law with exponent about −9.5. The observed upper limit of 5 – 6 kG is consistent with the idea that an umbral field has a more or less coherent structure down to some depth and then fragments. We find that odd-numbered sunspot cycles usually contain about 30% more total sunspot groups but 60% fewer >3 kG spots than preceding even-numbered cycles.     

Evidence for downflow following a coronal transient?

On 11 September 1973 a peculiar prominence was observed. The prominence displayed strong ( 50km s^–1) systematic motions toward and away from the observer. The unusual spectrographic appearance of the prominence might have been due to downflowing material lifted into the corona during an earlier coronal transient.The National Center for Atmospheric Research is sponsored by the National Science Foundation.Operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation.     

Condensed water in tropical cyclone “Oliver”, 8 February 1993

On February 8, 1993, the NASA DC-8 aircraft profiled from 10,000 to 37,000 feet (3.1–11.3 km) pressure altitude in a stratified section of tropical cyclone “Oliver” over the Coral Sea northeast of Australia. Size, shape and phase of cloud and precipitation particles were measured with a 2-D Greyscale probe. Cloud/ precipitation particles changed from liquid to ice as soon as the freezing level was reached near 17,000 feet (5.2 km) pressure altitude. The cloud was completely glaciated at −5°C. There was no correlation between ice particle habit and ambient temperature. In the liquid phase, the precipitation-cloud drop concentration was 4.0 × 10³ m⁻³, the geometric mean diameter D_g=0.5−0.7 mm, and the liquid water content 0.7−1.9 g m⁻³. The largest particles anywhere in the cloud, dominated by fused dendrites at concentrations similar to that of raindrops (2.5 × 10³ m⁻³) but a higher condensed water content (5.4 g m⁻³ estimated) were found in the mixed phase; condensed water is removed very effectively from the mixed layer due to high settling velocities of the large mixed particles. The highest number concentration (4.9 × 10⁴ m⁻³), smallest size (D_g=0.3−0.4 mm), largest surface area (up to 2.6 × 10² cm² m⁻³ at 0.4−1.0 g m⁻³ of condensate) existed in the ice phase at the coldest temperature (−40°C) at 35,000 feet (10.7 km). Each cloud contained aerosol (haze particles) in addition to cloud particles. The aerosol total surface area exceeded that of the cirrus particles at the coldest temperature. Thus, aerosols must play a significant role in the upscattering of solar radiation. Light extinction (6.2 km⁻¹) and backscatter (0.8 sr⁻¹ km⁻¹) was highest in the coldest portion of the cirrus cloud at the highest altitude.     

Energy input to the Earth

We review the physical origin, spectral nature, energetics and known variability of all solar emanations: photons, particles and magnetic fields. Compared to a decade ago, our knowledge has greatly improved concerning variability in the total irradiance, as well as its EUV and UV components. It is noted that synoptic EUV-UV irradiance data from space will cease in 1990 owing to space-craft orbital failures and the present launch hiatus. The case for variability in the past few centuries and predictions for the near term are given.     

Magnetograph measurements with temperature-sensitive lines

Certain discrepancies between theoretical and empirical calibrations of magnetograph response are resolved by recognizing the existence of line profile changes in magnetic regions. Many of the photospheric lines commonly used for magnetic field measurements weaken greatly in magnetic regions outside of sunspots. Unless due account is made of the line profile change, the magnetograph measurements underestimate magnetic flux and field strengths.The 5250.2 Å line is especially sensitive to weakening in magnetic regions. Measurements made with this line underestimate the true field by a factor ranging from about two on the linear portion of the profile to five near the line core.Kitt Peak National Observatory Contribution No. 500.Operated by the Association of Universities for Research in Astronomy Inc., under contract with the National Science Foundation.     

Pu and137Cs in coastal sediments

Analyses are presented of¹³⁷Cs,²³⁸Pu, and^239,240Pu, in relation to depth in sediment, in 21 gravity cores. These cores span the ranges of times 1964–1975, and of water depths 12–2000 m; they come from three distinct sedimentation areas off the northeast coast of the United States. Although the ranges of total sediment inventories of^239,240Pu and of¹³⁷Cs from the various areas hardly overlap, the range of ratios of the inventories of these two nuclides is probably the same in all the areas. In the shallow-water cores the^239,240Pu/¹³⁷Cs ratio regularly diminishes with depth in the core, and a tendency is seen for curves of this function to have similar slopes in each area; ratios of²³⁸Pu/^239,240Pu show no change with depth in these shallow-water cores. In the deeper-water cores, the^239,240Pu/¹³⁷Cs ratio shows no systematic change with depth, but sometimes the²³⁸Pu/^239,240Pu ratio shows a minimum at the sediment surface, and is much higher deeper in the cores. We believe that these phenomena can be explained in terms of a complicated bioturbational process moving the nuclides, together, down into the sediments, of chemical resolubilization, at depth, of plutonium only, and of its subsequent upward translocation in the interstitial solution. Some re-immobilization of plutonium near the sediment surface is implied, and a mechanism is suggested for this, based on displacement of plutonium from organic complexes by the increasing concentrations, in upper layers of the sediment, of re-oxidized dissolved iron.     

Field sampling in estuaries: The relationship of scale to variability

The spatial/temporal scaling problem (i.e., fitting a given research question to the dimensions of variability of the study area) is particularly pronounced in highly variable systems such as estuaries. Long-term, multidisciplinary studies in the Apalachicola Bay system were used to evaluate variation of different physical, chemical, and biological factors. Specific limitations of weekly, monthly, and quarterly sampling intervals were directly related to the efficiency of the sampling gear, the range of variation in the study parameters, and specific biological features (motility, recruitment, natural history) of infaunal macroinvertebrates and epibenthic organisms. There are families of spatial and temporal scaling phenomena that should be considered when establishing a given field sampling program. The dimensions of variation change along spatial/temporal gradients of salinity, habitat complexity, and productivity and among different levels of biological organization. The limits of variation define the needed sampling effort for a given level of estimation. Without an adequate evaluation of such variation, representative samples cannot be taken; the resulting inadequate sampling effort often precludes reliable comparisons and robust generalization. There is a continuum of scaling dimensions (and sampling problems) that ranges from small-scale experimental approaches to system-wide analyses. Misapplication of such scaling estimates has led to overgeneralization of experimental results. Currently, there is widespread misapplication of combinations of unrelated, limited sampling efforts to broad-scale resource problems. The loss of valuable estuarine resources is favored by the lack of adequate scientific databases that are consistent with the dimensions of the individual study areas. Unless experimental studies and field sampling programs are scaled to the dimensions of the research problem and the study area in question there will be a continued proliferation of trivial studies at one end of the continuum and the progressive deterioration of estuarine resources at the other.