On the umbra-penumbra area ratio of sunspots     

P. N. Brandt  W. Schmidt  M. Steinegger 《Solar physics》1990,129(1):191-194

The area ratio of umbra to penumbra (A_u/A_p) was investigated for a series of 126 sunspots observed around the maximum of solar activity in 1980. Plotting log (A_u) as function of log (A_p) a linear relation is obtained with a slope of 1.10, yielding an average ratio A_u/A_p of 0.24 for small spots and of 0.32 for large spots. This deviates noticeably from the commonly adopted constant value of A_u/A_p = 0.21 (Allen, 1973) used e.g. for modelling the sunspot irradiance deficit (cf. Willson et al., 1981) from the Solar Geophysical Data.Mitteilungen aus dem Kiepenheuer-Institut Nr. 328  相似文献   

The narrow-line quasar NAB 0205 + 024 observed with XMM–Newton     

L. C. Gallo  Th. Boller  W. N. Brandt  A. C. Fabian  S. Vaughan 《Monthly notices of the Royal Astronomical Society》2004,355(2):330-335

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On the centre-to-limb variation and latitude dependence of the asymmetry and wavelength shift of the solar line λ 5576     

P. N. Brandt  E. H. Schröter 《Solar physics》1982,79(1):3-18

Low noise photoelectric measurements of the line profile of the g = 0 Fe line gl 5576.097 combined with determinations of the wavelength shift of its centre calibrated by use of an I ₂ absorption tube are reported. Measurements taken at various limb distances (1.0 cos 0.2) and along 4 different diameters of the Sun are used to investigate the behaviour of the line asymmetry (C-shape) and wavelength shift of the line centre as functions of cos and of latitude and to search for possible pole-equator differences.An accuracy of approx. 0.8 mÅ r.m.s. is achieved for the determination of the centre of the solar line relative to the iodine lines and of 0.3 mÅ to 1 mÅ r.m.s. for the relative variations of the C-shape. The analysis shows a significant difference between the limb-effect curves along polar and equatorial diameters for cos 0.4 and changes of the C-shape for 0.9 cos 0.6 with a rather strong indication of a latitude dependence of the C-shape. This latitude dependence may account for the so-called ears observed by Howard et al. (1980) who used the well-known Doppler compensator method which integrates the line asymmetry from the line wings to the core.Mitteilungen aus dem Kiepenheuer-Institut Nr. 207.  相似文献   

Structures far from the head of comet Kohoutek: II. A discussion of the swan cloud of January 11 and of the general morphology of cometary plasma tails     

Malcolm B. Niedner  John C. Brandt 《Icarus》1980,42(2):257-270

Photographs taken in New Mexico and in Japan during 1974 January 9–11 show that the “Swan Cloud” observed in comet Kohoutek on January 11 (C. L. Hyder, J. C. Brandt, and R. G. Roosen, 1974, Icarus23, 601–610: Paper I) was an advanced stage of a plasma tail disconnection event (DE). The event commenced and evolved with the development of strong tail ray activity, the actual tail disconnection, the merging of the disconnected tail with the new tail to form the Swan, and a new feature not discussed in recent disconnection models—the formation of arcade loops in the space between closing tail rays. An unusual aspect of the event was the deceleration of the rejected tail as it receded from the head.The observed morphological sequence is easily understood in the sector boundary model (M. B. Niedner, Jr., and J. C. Brandt, 1978, Astrophys. J.223, 655–670; 1979, Astrophys. J.234 723–732), in which dayside reconnection of captured interplanetary fields at sector boundary crossings strips away the existing tail, and field capture in the new sector builds a new tail. The associated sector boundary for the event passed Earth of 1974 January 14.The arcade loops are proposed to be reconnected flux tubes between oppositely polarized tail rays in the incipient new tail which followed the disconnection. This interpretation is not only consistent with the magnetic field topology advocated in Alfvén's original model (H. Alfvén, 1957 Tellus9 92–96), but it may also provide a physical model for some of the features known historically as “condensation,” at least some of which appear to have formed in the same manner.  相似文献   

An RXTE observation of the Seyfert 1 galaxy MCG–6-30-15: X-ray reflection and the iron abundance     

J. C. Lee  A. C. Fabian  C. S. Reynolds  K. Iwasawa  & W. N. Brandt 《Monthly notices of the Royal Astronomical Society》1998,300(2):583-588

We report on a 50-ks observation of the bright Seyfert 1 galaxy MCG–6-30-15 with the Rossi X-ray Timing Explorer . The data clearly show the broad fluorescent iron line (equivalent width ∼ 250 eV) and the Compton reflection continuum at higher energies. A comparison of the iron line and the reflection continuum has enabled us to constrain the reflective fraction and the elemental abundances in the accretion disc. Temporal studies provide evidence that spectral variability is a result of changes in both the amount of reflection seen and the properties of the primary X-ray source itself.  相似文献   

Changes in timber haul emissions in the context of shifting forest management and infrastructure     

Sean P Healey  Jock A Blackard  Todd A Morgan  Dan Loeffler  Greg Jones  Jon Songster  Jason P Brandt  Gretchen G Moisen  Larry T DeBlander 《Carbon balance and management》2009,4(1):1-11

The issues surrounding 'Reduced Emissions from Deforestation and Forest Degradation' (REDD) have become a major component of continuing negotiations under the United Nations Framework Convention on Climate Change (UNFCCC). This paper aims to address two key requirements of any potential REDD mechanism: first, the generation of measurable, reportable and verifiable (MRV) REDD credits; and secondly, the sustainable and efficient provision of emission reductions under a robust financing regime. To ensure the supply of MRV credits, we advocate the establishment of an 'International Emission Reference Scenario Coordination Centre' (IERSCC). The IERSCC would act as a global clearing house for harmonized data to be used in implementing reference level methodologies. It would be tasked with the collection, reporting and subsequent processing of earth observation, deforestation- and degradation driver information in a globally consistent manner. The IERSCC would also assist, coordinate and supervise the computation of national reference scenarios according to rules negotiated under the UNFCCC. To overcome the threats of "market flooding" on the one hand and insufficient economic incentives for REDD on the other hand, we suggest an 'International Investment Reserve' (IIR) as REDD financing framework. In order to distribute the resources of the IIR we propose adopting an auctioning mechanism. Auctioning not only reveals the true emission reduction costs, but might also allow for incentivizing the protection of biodiversity and socio-economic values. The introduced concepts will be vital to ensure robustness, environmental integrity and economic efficiency of the future REDD mechanism.  相似文献   

First ENA observations at Mars: Charge exchange ENAs produced in the magnetosheath     

H. Gunell  K. Brinkfeldt  P. C:son Brandt  E. Kallio  Y. Futaana  H. Andersson  A. Grigoriev  R.A. Frahm  J.R. Scherrer  D.R. Linder  T. Säles  W. Schmidt  J. Kozyra  E. Roelof  S. Livi  K.C. Hsieh  M. Grande  J.-A. Sauvaud  J.-J. Thocaven  S. Orsini  M. Maggi  P. Bochsler  J. Woch  K. Asamura 《Icarus》2006,182(2):431-438

Measurements of energetic neutral atoms (ENA) generated in the magnetosheath at Mars are reported. These ENAs are the result of charge exchange collisions between solar wind protons and neutral oxygen and hydrogen in the exosphere of Mars. The peak of the observed ENA flux is . For the case studied here, i.e., the passage of Mars Express through the martian magnetosheath around 20:15 UT on 3 May 2004, the measurements agree with an analytical model of the ENA production at the planet. It is possible to find parameter values in the model such that the observed peak in the ENA count rate during the spacecraft passage through the magnetosheath is reproduced.  相似文献   

Mantle sources of the Cenozoic volcanic rocks of the Lake Kizi region in the eastern Sikhote Alin     

S. V. Rasskazov  V. S. Prikhod’ko  T. A. Yasnygina  N. N. Fefelov  E. V. Saranina  I. P. Voinova  S. B. Brandt 《Russian Journal of Pacific Geology》2010,4(5):441-459

The Middle Cenozoic lava sequence of the Lake Kizi region was studied. It characterizes the activity of sources in the Northern zone of the eastern Sikhote Alin: a Middle Eocene pulse of slab-related magmatism and prolonged injection of magmas from the sublithospheric convecting mantle in the Late Oligocene. Low contents of high field strength elements (Nb and Ta) with low Nb/Ta, Ce/Pb, and Nb/La and high K/Nb ratios and a low (⁸⁷Sr/⁸⁶Sr)₀ of 0.703399 were determined in a Middle Eocene dacite with an age of ∼43.5 Ma. Three phases of Late Oligocene volcanic eruptions were distinguished: (1) basaltic andesites (29–27 Ma), (2) basaltic trachyandesites and trachyandesites (27–24 Ma), and (3) andesites (∼23 Ma). The lavas of the first and third phases showed low Ce/Pb, Nb/La, and Ba/La and high K/Nb ratios, which are also characteristic of supraslab processes. The lavas of the second phase are shifted with respect to these ratios toward ocean island basalt compositions. The entire Late Oligocene volcanic sequence falls within a narrow range of the initial strontium isotope ratios, (⁸⁷Sr/⁸⁶Sr)₀, from 0.703661 to 0.703853. Such ratios are characteristic of volcanic and subvolcanic rocks with ages of ∼37, 31–23, and ∼16 Ma over the whole region of the Tatar Strait coast.  相似文献   

Time-slice diagrams of solar granulation     

Müller  D.A.N.  Steiner  O.  Schlichenmaier  R.  Brandt  P.N. 《Solar physics》2001,203(2):211-232

From a series of 1400 white-light images of solar granulation spanning a time period of 8.2 hours, skeletal plots of time-slice diagrams are derived showing intergranular lane positions as a function of time. The diagrams permit to automatically track, classify, and relate 42 186 granules. Recurrently fragmenting granules are found that survive by means of their descendants for more than 3 hours. Such long-lived active granules tend to have a mean spatial distance along the slice of about 10 Mm. This distance decreases with decreasing minimal required lifetime. Since active granules are expected to generate a steadily divergent flow over a long period of time, it is suggested to identify them as a source of the mesogranular flow. Deficiencies of the time-slice analysis are discussed. The relative frequency of different types of granules and the granule decay time as derived from the time-slice diagrams are compared with corresponding results of previous works. Supplementary material to this paper is available in electronic form at http://dx.doi.org/10.1023/A:1013350505080  相似文献   

Mean meridional currents in the central and eastern equatorial Atlantic     

Renellys C. Perez  Verena Hormann  Rick Lumpkin  Peter Brandt  William E. Johns  Fabrice Hernandez  Claudia Schmid  Bernard Bourlès 《Climate Dynamics》2014,43(11):2943-2962

Ship-based acoustic Doppler current profiler (ADCP) velocity measurements collected by several major field programs in the tropical Atlantic are averaged and combined with estimates of the mean near-surface velocity derived from drifters and Argo float surface drifts (ADCP+D) to describe the mean cross-equatorial and vertical structure of the meridional currents along 23°W and 10°W. Data from moored ADCPs and fixed-depth current meters, a satellite-derived velocity product, and a global ocean reanalysis were additionally used to evaluate the mean ADCP+D meridional velocity. The dominant circulation features in the long-term mean ADCP+D meridional velocity in the upper 100 m are the tropical cells (TCs) located approximately between 5°S and 5°N, with near-surface poleward flow and subsurface equatorward flow that is stronger and shallower in the northern cell compared to the southern cell. The thickness of the surface limb of the TCs decreases and the northern cell is found to shift further south of the equator from the central to eastern tropical Atlantic. Analysis of two-season means estimated from the ship-based ADCP, near-surface drift, and moored velocity data, as well as the simulated fields, indicates that the maximum poleward velocity in the surface limb of the TCs intensifies during December–May along 23°W largely due to seasonal compensation between the geostrophic and ageostrophic (or wind-driven) components of the meridional velocity, whereas the maximum equatorward flow in the subsurface limb of the northern cell intensifies during June–November along both 23°W and 10°W due to the seasonality of the geostrophic meridional velocity.  相似文献