Predictions of Solar Cycle 24   总被引：1，自引：0，他引：1  

William Dean Pesnell 《Solar physics》2008,252(1):209-220

A summary and analysis of more than 50 predictions of the amplitude of the upcoming Solar Cycle 24 is presented. All of the predictions were published before solar minimum and represent our efforts to anticipate solar maximum at ever-earlier epochs. The consistency of the predictions within their assigned categories is discussed. Estimates of the significance of the predictions, compared to the climatological average, are presented.  相似文献   

Entablature: fracture types and mechanisms     

A. E. S. Forbes  S. Blake  H. Tuffen 《Bulletin of Volcanology》2014,76(5):1-13

Stratigraphic and morphostructural analyses have been carried out in the Mt. Etna volcanic region (eastern Sicily) to investigate in detail the deformation events that have affected the sedimentary successions forming the substratum of the volcano. In the foredeep, Quaternary submarine sedimentation ended 600 ka ago when the whole area emerged in response to homogeneous regional uplift. The irregular distribution of a stratigraphic marker, recognized through the analysis of more than 250 borehole logs, suggests that local dynamics also affected the area. We identify both compressional tectonic dynamics and volcano-related tectonic activity, and discriminate among their associated deformations. In particular, we quantify the vertical deformation component of the compressional structures (thrusts and related folds) and recognize for the first time a vertical component of deformation whose pattern clearly indicates a doming process acting at Mt. Etna. The comparison between long-term and short-term rates suggests that the doming has acted consistently over space and time through the last 600 ka and provides clues to the source of uplift. This component, defined by a specific Quaternary sedimentary horizon, has been compared with vertical deformation obtained by analytical inversion of morphological substratum data, and localizes the source at a depth of ～16 km, at the mantle-crust transition. This uplift may be the consequence of hydration occurring in the altered ocean-like crust.  相似文献   

Seabirds as indicators of aquatic ecosystem conditions: A case for gathering multiple proxies of seabird health     

Mark L. Mallory  Stacey A. Robinson  Mark R. Forbes 《Marine pollution bulletin》2010,60(1):7-12

The use of seabirds as sentinels of the condition of aquatic ecosystems has been well-established. Large environmental perturbations to aquatic food webs (e.g., chemical contamination, overfishing, particulate pollution) have all been detected or monitored by tracking seabirds at colonies. However, seabirds may elicit more subtle, sublethal responses that can also be used to track ecosystem health, or the health of seabird populations. In this article, we advocate for field researchers to plan a priori to collect a broader suite of samples when handling seabirds, and to reach out for collaboration with specialists (e.g., parasitologists, wildlife veterinarians). Collectively, such efforts will greatly improve our ability to establish baseline physiological and chemical levels for seabirds, against which we can detect future changes in aquatic ecosystems.  相似文献   

Global distribution and climatological features of the 5–6-day planetary waves seen in the SABER/TIMED temperatures (2002–2007)     

D. Pancheva  P. Mukhtarov  B. Andonov  J.M. Forbes 《Journal of Atmospheric and Solar》2010,72(1):26-37

The paper is focused on the global spatial structure, seasonal and interannual variability of the ～5-day Rossby (W1) and ～6-day Kelvin (E1) waves derived from the SABER/TIMED temperature measurements for 6 full years (January 2002–December 2007). The latitude structure of the ～5-day W1 wave is related to the gravest symmetric wave number 1 Rossby wave. The vertical structure of the ～5-day Rossby wave amplitude consists of double-peaked maxima centred at ～80–90 km and ～105–110 km. This wave has a vertically propagating phase structure from the stratosphere up to 120 km altitude with a mean vertical wavelength of ～50–60 km. The ～6-day E1 wave is an equatorially trapped wave symmetric about the equator and located between 20°N and 20°S. Its seasonal behaviour indicates some equinoctial and June solstice amplifications, while the vertical phase structure indicates that this is a vertically propagating wave between 20–100 km altitudes with a mean vertical wavelength of ～25 km.  相似文献   

Erratum to: “A collaborative study on temperature diurnal tide in the midlatitude mesopause region (41°N, 105°W) with Na lidar and TIMED/SABER observations” [J. Atmos. Sol.–Terres. Phys. 72 (2010) 541–549]     

Tao Yuan  Chiao-Yao She  David Krueger  Steven C. Reising  Xiaoli Zhang  Jeffrey M. Forbes 《Journal of Atmospheric and Solar》2010,72(14-15):1067

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Towards a theory for type III solar radio bursts     

Dean F. Smith 《Solar physics》1974,34(2):393-411

The mechanisms for the transformation of plasma waves into radiation near the fundamental and second harmonic of the plasma frequency are reviewed and equations are given for both the emission and absorption coefficients for these mechanisms. Near the fundamental the process is the scattering of plasma waves on the polarization clouds of ions and the absorption coefficient can be negative, i.e. the radiation can be amplified. Near the second harmonic the process is the combination of two excited plasma waves for which the absorption coefficient can only be positive. These results are applied to construct models of the radiation source for type III solar radio bursts both at high frequencies where the fundamental is dominant and at low frequencies where the second harmonic is dominant using two model plasma wave spectra, one being one-dimensional, the other isotropic. At high frequencies second harmonic radiation is used to determine the source area for a given energy density in plasma waves W _p . The source size and W _p are detrmined uniquely for a given plasma wave spectrum by tracing rays in a model source taking into account amplification of the fundamental. The results for a strong source at the 80 MHz plasma level with a ratio of emissivities of the fundamental to second harmonic P(ω _p )/P(2ω _p ) ≈ 10 are that the source with a one-dimensional plasma wave spectrum is about 14000 km in diameter and W _p = 10^?6.52 erg cm^?3, and the source with an isotropic distribution of plasma waves is about 200 km in diameter and W _p = 10^?6.3 erg cm^?3. It is shown that at low frequencies, where amplification of the fundamental is no longer possible, second harmonic radiation must be dominant and thus very little information about the source can obtained from the radiation.  相似文献   

Towards a better dynamic theory for type III radio bursts     

Dean F. Smith 《Solar physics》1973,33(1):213-223

An approximate numerical solution is given to the quasilinear equations governing the interaction of the electron streams exciting type III solar radio bursts and the background plasma. The density and temperature variations are taken into account and the stream is studied from r =1 to 20 R . The method used is to level any positive slopes in the distribution function as they develop and record the energy released. None of the energy released is allowed to return to the stream and since no other damping mechanisms are taken into account, the solution is only applicable to the initial rise of the burst. Even then, the solution gives more decleration of the leading edge of the burst than observed which indicates that letting some of the energy released return to the stream is necessary. At the same time the solution does show that depletion of high velocity electrons is an important process and calls into question any analysis which neglects this process by, for example, integrating over the spectrum of plasma waves such as Zaitsev et al. (1972). It is shown that the case considered here is an opposite limiting case to the one considered by Zaitsev et al. and what needs to be done to find the more realistic solution in between these two limiting cases is indicated.The National Center for Atmospheric Research is sponsored by the National Science Foundation.  相似文献   

Mass upflows in ‘post’-flare loops     

T. G. Forbes  E. R. Priest 《Solar physics》1983,88(1-2):211-218

A self-consistent numerical model of a reconnecting magnetic field configuration similar to that occurring during the main-phase of two-ribbon flares is used to estimate the upflow caused by the fast-mode expansion of the magnetic field moving into the reconnection region. Such an expansion creates a field-aligned pressure gradient which accelerates plasma upward from the chromospheric base of magnetic field lines in the region external to the loops. The numerical results imply that the amount of mass sucked up in this way is even smaller than was previously estimated by Kopp and Pneuman who used a kinematic model. Therefore, some indirect mechanism (such as evaporation), which would probably derive its motive power from the thermal energy generated by the reconnection, is required to explain the large mass upflows inferred from observations.  相似文献   

First phase acceleration mechanisms and implications for hard X-ray burst models in solar flares     

Dean F. Smith 《Solar physics》1980,66(1):135-148

Requirements for the number of nonthermal electrons which must be accelerated in the impulsive phase of a flare are reviewed. These are uncertain by two orders of magnitude depending on whether hard X-rays above 25 keV are produced primarily by hot thermal electrons which contain a small fraction of the flare energy or by nonthermal streaming electrons which contain > 50% of the flare energy. Possible acceleration mechanisms are considered to see to what extent either X-ray production scenario can be considered viable. Direct electric field acceleration is shown to involve significant heating. In addition, candidate primary energy release mechanisms to convert stored magnetic energy into flare energy, steady reconnection and the tearing mode instability, transfer at least half of the stored energy into heat and most of the remaining energy to ions. Acceleration by electron plasma waves requires that the waves be driven to large amplitude by electrons with large streaming velocities or by anisotropic ion-acoustic waves which also require streaming electrons for their production. These in turn can only come from direct electric field acceleration since it is shown that ion-acoustic waves excited by the primary current cannot amplify electron plasma waves. Thus, wave acceleration is subject to the same limitations as direct electric field acceleration. It is concluded that at most 0.1% of the flare energy can be deposited into nonthermal streaming electrons with the energy conversion mechanisms as they have been proposed and known acceleration mechanisms. Thus, hard X-ray production above 10 keV primarily by hot thermal electrons is the only choice compatible with models for the primary energy release as they presently exist.  相似文献   

The fundamental plane of isolated early-type galaxies   总被引：1，自引：0，他引：1  

Fatma M. Reda  Duncan A. Forbes  George K. T. Hau 《Monthly notices of the Royal Astronomical Society》2005,360(2):693-702

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