Solar gravitational redshift

Wavelengths of solar spectrum lines should be shifted toward the red by the Sun's gravitational field as predicted by metric theories of gravity according to the principle of equivalence. Photographic wavelengths of 738 solar Fe i lines and their corresponding laboratory wavelengths have been studied. The measured solar wavelength minus the laboratory wavelength (_observed) averaged for the strong lines agrees well with the theoretically predicted shift (_theoretical). Studies show that the departures depend on line strength. No dependence of the departures on wavelength was found within the existing data.By studying strong lines over a wide spectral range, velocity shifts caused by the complex motions in the solar atmosphere seem to affect the results in a minimal fashion.     

Venus mesosphere and thermosphere temperature structure: II. Day-night variations

A two-dimensional nonlinear hydrodynamic model has been developed for studying the global scale winds, temperature, and compositional structure of the mesosphere and thermosphere of Venus. The model is driven by absorption of solar radiation. Ultraviolet radiation produces both heating and photodissociation. Infrared solar heating and thermal cooling are also included with an accurate NLTE treatment. The most crucial uncertainty in determining the solar drive is the efficiency by which $\text{λ < 1080}\text{A}\text{?}$ solar radiation is converted to heat. This question was analyzed in Part I, where it was concluded that essentially all hot atom and O(¹D) energy may be transferred to vibrational-rotational energy of CO₂ molecules. If this is so, the minimum possible euv heating occurs and is determined by the quenching of the resulting excess rotational energy. The hydrodynamic model is integrated with this minimum heating and neglecting any small-scale vertical eddy mixing. The results are compared with predictions of another model with the same physics except that it assumes that 30% of $\text{λ < 1080}\text{A}\text{?}$ radiation goes into heat and that the heating from longer-wavelength radiation includes the O(¹D) energy. For the low-efficiency model, exospheric temperatures are ?300°K on the dayside and drop to < 180°K at the antisolar point. For the higher-efficiency model, the day-to-night temperature variation is from ?600°K to ?250°K. Both versions of the model predict a wind of several hundred meters per second blowing across the terminator and abruptly weakening to small values on the nightside with the mass flow consequently going into a strong tongue of downward motion on the nightside of the terminator. The presence of this circulation could be tested observationally by seeing if its signature can be found in temperature measurements. Both versions of the model indicate that a self-consistent large-scale circulation would maintain oxygen concentrations with ?5% mixing ratios near the dayside F-1 ionospheric peak but ?40% at the antisolar point at the same pressure level.     

Unusual coronal activity following the flare of 6 November 1980

For almost 30 hr after the major (gamma-ray) two-ribbon flare on 6 November 1980, 03:30 UT, the Hard X-Ray Imaging Spectrometer (HXIS) aboard the SMM satellite imaged in > 3.5 keV X-rays a gigantic arch extending above the active region over the limb. Like a similar configuration on 22 May 1980, this arch formed the lowest part of a stationary post-flare radio noise storm recorded at metric wavelengths at Nançay and Culgoora. 6.5 hr after the flare a coronal region below the arch started quasi-periodic pulsations in X-ray brightness, observed by several SMM instruments. These brightness variations had no response in the chromosphere (H), very little in the transition layer (O v), but they clearly correlated with similar variations in brightness at 169 MHz. There were 13 pulses of this kind, with apparent periodicity of about 20 min, until another flare occurred in the active region at 15:00 UT. All the brightenings appeared within a localized area of about 30000 km² in the northern part of the active region, but they definitely did not occur all at the same place.The top of the X-ray arch, at an altitude of 155 000 km, was continuously and smoothly decaying, taking no part in the striking variations below it. Therefore, the area variable in brightness does not seem to be the footpoint of the arch, as we supposed for similar variations on 22 May. More likely, it is a separate region connected directly with the source of the radio storm; particles accelerated in the storm may be dumped into the low corona and cause the X-ray enhancements. The X-ray arch was enhanced by two orders of magnitude in 3.5–5.5 keV X-ray counts and the temperature increased from 7.3 × 10⁶ to 9 × 10⁶ K when the new two-ribbon flare occurred at 15:00 UT. Thus, it is possible that energy is brought into the arch via the upper parts of the reconnecting flare loops - a process that can continue for hours.     

Are the high-latitude torsional oscillations of the sun real?

A numerical test is made to determine if the high-latitude torsional wave is generated from the low-latitude torsional pattern as a result of our reduction procedures. The results indicate that the high-latitude motions are not an artifact of the analysis, but are true solar features. We demonstrate also that the one-wave-per-hemisphere torsional oscillation does not result from the reduction procedure. These results place the observations in conflict with the predictions of - () models of the solar cycle.Now at Institute for Astronomy, University of Hawaii, Honolulu, Hawaii 96822, U.S.A.     

The influence of amphibole fractionation on the evolution of calc-alkaline andesite and dacite tephra from the central Aleutians,Alaska

Petrologic studies of tephra from Kanaga, Adak, and Great Sitkin Islands indicate that amphibole fractionation and magma mixing are important processes controlling the composition of calc-alkaline andesite and dacite magmas in the central Aleutians. Amphibole is ubiquitous in tephra from Kanaga and Adak Islands, whereas it is present only in a basaltic-andesite pumice from Great Sitkin. Dacitic tephra from Great Sitkin do not contain amphibole. Hornblende dacite tephra contain HB+PLAG+OX±OPX±CPX phenocrysts with simple zoning patterns, suggesting that the dacites evolved in isolated magma chambers. Andesitic tephra from Adak contain two pyroxene and hornbelende populations, and reversely zoned plagioclase, indicating a more complex history involving mixing and fractional crystallization. Mass balance calculations suggest that the andesitic tephra may represent the complements of amphibole-bearing cumulate xenoliths, both formed during the evolution of high-Al basalts. The presence of amphibole in andesitic and dacitic tephra implies that Aleutian cale-alkaline magmas evolve in the mid to lower crust under hydrous (>4 wt.% H₂O) and oxidizing (Ni–NiO) conditions. Amphibole-bearing andesites and pyroxene-bearing dacites from Great Sitkin indicates fractionation at several levels within the arc crust. Despite its absence in many calc-alkaline andesite and dacite lavas, open system behavior involving amphibole fractionation can explain the trace element characteristies of lavas found on Adak Island. Neither open nor closed system fractionation involving a pyroxene-bearing assemblage is capable of explaining the trace element concentrations or ratios found in the Adak suite. We envision a scenario where amphibole was initially a liquidus phase in many calc-alkaline magmas, but was later replaced by pyroxenes as the magmas rose to shallow levels within the crust. The mineral assemblage in these evolved lavas reflects shallow level equilibration of the magma, whereas the trace element chemistry provides evidence for a earlier, amphibole-bearing, mineral assemblage.     

Book reviews

REGIONAL GEOGRAPHY: Current Developments and Future Prospects edited by R. J. Johnston, J Hauer and G. A. Hoekveld. 14 × 22 cm, xiii and 216 pages. Routledge: London 1990 (ISBN 0 415 05247 5) $A89.95 (hard).

THE MAKING OF THE AMERICAN LANDSCAPE edited by M. P. Conzen. 19 × 25 cm, xvi and 433 pages. Unwin Hyman: Boston 1990 (ISBN 0 04 917010 4) $A59.95 (soft).

EASTERN EUROPE: An Historical Geography 1815–1945 by D. Turnock. 14 × 22 cm, ix and 357 pages. Routledge: London 1989 (ISBN 0 415 01269 4) $A115.00 (hard), distributed by the Law Book Co.

THE HUMAN GEOGRAPHY OF EASTERN EUROPE by D. Turnock. 14 × 22 cm, xii and 345 pages. Routledge: London 1989 (ISBN 0 415 00469 1) $A105.00 (hard), distributed by the Law Book Co.

A HISTORY OF THE PACIFIC ISLANDS by I. C. Campbell. 14 × 21 cm, 239 pages. University of Queensland Press: St Lucia 1990 (ISBN 0 7022 2291 7) $A34.95 (soft).

THE CORPORATE FIRM IN A CHANGING WORLD ECONOMY: Case Studies in the Geography of Enterprise edited by M. de Smidt and E. Wev‐er. 14 × 23 cm, xiv and 247 pages. Routledge: London 1990 (ISBN 0 415 03497 3) $A105.00 (hard).

THE CAPITALIST CITY: Global Restructuring and Community Politics by M. P. Smith and J. R. Feagin. 15 × 23 cm, 393 pages. Basil Black‐well: Oxford 1988 (ISBN 0 631 15182 6) £35 (hard).

CONFLICT AND CHANGE IN THE COUNTRYSIDE: Rural Society, Economy and Planning in the Developed World by G. M. Robinson. 15 × 23 cm, xxvi and 482 pages. Belhaven Press: London 1990 (ISBN 1 85293 043 8) £40.00 (hard); (ISBN 1 85293 044 6) £14.95 (soft).

ENVIRONMENTAL SCIENCE (Collins Reference Dictionary) by G. Jones, A. Robertson, J. Forbes and G. Hollier. 13 × 20 cm, vi and 473 pages. Collins: London 1990 (ISBN 0 00 434348 4) £5.95 (soft).

THE HUMAN IMPACT ON THE NATURAL ENVIRONMENT (Third Edition) by A. Goudie. 17 × 24 cm, xi and 388 pages. Blackwell: Oxford 1990 (ISBN 0 631 16164 3) $A39.95 (soft).

PATTERNS OF LIFE: Biogeography of a Changing World by H. W. Mielke. 19 × 24 cm, xiv and 370 pages. Unwin Hyman: London 1989 (ISBN 0 04 574032 1).     

Sunspot group areas and the latitude distance from the average latitude of activity

Digitized Mount Wilson sunspot data from 1917 to 1985 are analyzed to examine group areas as a function of latitude distance () from the central latitude of activity in each hemisphere. On average these group areas are larger for the smallest values of ¦¦. The effect is similar to that seen for the magnetic fields of active regions (Howard, 1991). It is concluded that this is fundamentally a dependence, and not a latitude dependence. The suggestion is made that the cause of this effect is the influence of large-scale convective motions on the rising flux tubes that make up the active regions. The smaller flux tubes (spot groups) are more easily displaced in latitude during their ascent to the surface by this velocity field than are the larger flux tubes.Operated by the Association of Universities for Research in Astronomy, Inc., under Cooperative Agreement with the National Science Foundation.