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2.
Béla Kálmán 《Solar physics》2002,209(1):109-117
Comparison of photographic observations and vector-magnetograph measurements demonstrate that the outer boundary of the sunspot
penumbra – even in complex sunspot groups – closely follows the 0.075 T iso-gauss line of the total value of the magnetic
field, corresponding approximately to the equipartition value in the photosphere. Radio observations also show this feature.
The thick penumbra model with interchange convection (Jahn and Schmidt, 1994) gives the best explanation of the penumbral
structure.
Supplementary material to this paper is available in electronic form at http://dx.doi.org/10.1023/A:1020985530075 相似文献
3.
The large dynamic range provided by the SOHO/EIT CCD (1 : 5000) is needed to observe the large EUV zoom of coronal structures
from coronal homes up to flares. Histograms show that often a wide dynamic range is present in each image. Extracting hidden
structures in the background level requires specific techniques such as the use of the Multiscale Vision Model (MVM, Bijaoui
et al., 1998). This method, based on wavelet transformations optimizes detection of various size objects, however complex they may
be. Bijaoui et al. built the Multiscale Vision Model to extract small dynamical structures from noise, mainly for studying galaxies. In this
paper, we describe requirements for the use of this method with SOHO/EIT images (calibration, size of the image, dynamics
of the subimage, etc.). Two different areas were studied revealing hidden structures: (1) classical coronal mass ejection
(CME) formation and (2) a complex group of active regions with its evolution. The aim of this paper is to define carefully
the constraints for this new method of imaging the solar corona with SOHO/EIT. Physical analysis derived from multi-wavelength
observations will later complete these first results.
Supplementary material to this paper is available in electronic form at http://dx.doi.org/10.1023/A:1017579625208
with J.P. Delaboudinière P.I. 相似文献
4.
Saint-Hilaire Pascal von Praun Christoph Stolte Etzard Alonso Gustavo Benz Arnold O. Gross Thomas 《Solar physics》2002,210(1-2):143-164
The RHESSI Experimental Data Center (HEDC) at ETH Zürich aims to facilitate the use of RHESSI data. It explores new ways to
speed up browsing and selecting events such as solar flares. HEDC provides pre-processed data for on-line use and allows basic
data processing remotely over the Internet. In this article, we describe the functionality and contents of HEDC, as well as
first experiences by users. HEDC can be accessed at http://www.hedc.ethz.ch. Additional graphical material and color versions of most figures are available on the CD-ROM accompanying this volume.
Supplementary material to this paper is available in electronic form at http://dx.doi.org/10.1023/A:1022413302246 相似文献
5.
Emerging coronal loops were studied with extreme ultraviolet observations performed by SOHO/EIT on 5 and 6 August 1997 for
NOAA 8069. Physical parameters (size and twist) were determined by a new stereoscopic method. The flux tubes were measured
twisted when first observed by EIT. After emerging, they de-twisted as they expanded, which corresponds to a minimization
of the energy. Different scenarios which take into account the conservation of the magnetic helicity are discussed in relation
with structure and temperature variations.
Supplementary material to this paper is available in electronic form at http://dx.doi.org/10.1023/A:1013329626327 相似文献
6.
Large impacts not only create giant basins on terrestrial planets but also heat their interior by shock waves. We investigate the impacts that have created the largest basins existing on the planets: Utopia on Mars, Caloris on Mercury, Aitken on Moon, all formed at ∼4 Ga. We determine the impact-induced temperature increases in the interior of a planet using the “foundering” shock heating model of Watters et al. (Watters, W.A., Zuber, M.T., Hager, B.H. [2009]. J. Geophys. Res. 114, E02001. doi:10.1029/2007JE002964). The post-impact thermal evolution of the planet is investigated using 2D axi-symmetric convection in a spherical shell of temperature-dependent viscosity and thermal conductivity, and pressure-dependent thermal expansion. The impact heating creates a superheated giant plume in the upper mantle which ascends rapidly and develops a strong convection in the mantle of the sub-impact hemisphere. The upwelling of the plume rapidly sweeps up the impact-heated base of the mantle away from the core-mantle boundary and replaces it with the colder surrounding material, thus reducing the effects of the impact-heated base of the mantle on the heat flux out of core. However, direct shock heating of the core stratifies the core, suppresses the pre-existing thermal convection, and cripples a pre-existing thermally-driven core dynamo. It takes about 17, 4, and 5 Myr for the stratified cores of Mars, Mercury, and Moon to exhaust impact heat and resume global convection, possibly regenerating core dynamos. 相似文献
7.
We use MDI magnetic field observations and the theory of reconnection through a separator to constrain a numerical simulation
of an X-ray bright point observed in EUV by TRACE. A gasdynamic model is employed to describe the corona and transition region
in the bright point loop. Nonlocal effects such as opacity and ambipolar diffusion are important to the transition region;
these effects are approximated locally by modification of the radiative loss and thermal conduction. A straightforward comparison
of measured light curves versus those generated by the simulation shows that the reconnection model is unable to account for
the observations.
Supplementary material to this paper is available in electronic form at http://dx.doi.org/10.1023/A:1005205807984 相似文献
8.
This paper is a pedagogical introduction to avalanche models of solar flares, including a comprehensive review of recent modeling
efforts and directions. This class of flare model is built on a recent paradigm in statistical physics, known as self-organized
criticality. The basic idea is that flares are the result of an ‘avalanche’ of small-scale magnetic reconnection events cascading
through a highly stressed coronal magnetic structure, driven to a critical state by random photospheric motions of its magnetic
footpoints. Such models thus provide a natural and convenient computational framework to examine Parker's hypothesis of coronal
heating by nanoflares.
Supplementary material to this paper is available in electronic form at http://dx.doi.org/10.1023/A:1013301521745 相似文献
9.
Peculiar high-speed X-ray jets associated with the 18 June 1999 limb flares have directly been observed with the soft X-ray
Telescope (SXT) aboard Yohkoh. The jets have a much shorter lifetime (within 200 s) and a much larger velocity (∼ 1700 km s−1) than the previously reported jets. Judged from their large velocity, the kinetic energy of the jets is approximately one
order of magnitude larger than the thermal energy content, which is far different from the jets previously reported by other
researchers. Here we present the preliminary results and discuss the particular features of the jets.
Supplementary material to this paper is available in electronic form at http://dx.doi.org/10.1023/A:1013324126229 相似文献
10.
Tungsten isotopes in ferroan anorthosites: Implications for the age of the Moon and lifetime of its magma ocean 总被引：1，自引：0，他引：1
New W isotope data for ferroan anorthosites 60025 and 62255 and low-Ti mare basalt 15555 show that these samples, contrary to previous reports [Lee, D.C., et al., 1997. Science 278, 1098-1103; Lee, D.C., et al., 2002. Earth Planet. Sci. Lett. 198, 267-274], have a W isotope composition that is indistinguishable from KREEP and other mare basalts. This requires crust extraction on the Moon later than ∼60 Myr after CAI formation, consistent with 147Sm-143Nd ages for ferroan anorthosites. The absence of 182Hf-induced 182W variations in the Moon is consistent with formation of the Moon at after CAI formation that has been inferred based on the indistinguishable 182W/184W ratios of the bulk Moon and the bulk silicate Earth. The uncertainties on the age of the Moon and the age of the oldest lunar samples currently hamper a precise determination of the duration of magma ocean solidification and are consistent with both an almost immediate crystallization and a more protracted timescale of ∼100 Myr. 相似文献
11.
Schwartz R.A. Csillaghy A. Tolbert A.K. Hurford G.J. Mc Tiernan J. Zarro D. 《Solar physics》2002,210(1-2):165-191
The Reuven Ramaty High-Energy Solar Spectroscopic Imager (RHESSI) performs imaging spectroscopy of the Sun with high spatial
and spectral resolution from 3 keV to 17 MeV using indirect Fourier-transform techniques. We review the rationale behind the
RHESSI data analysis software, and explain the underlying structure of the software tools. Our goal was to make the large
data set available within weeks after the RHESSI launch, and to make it possible for any member of the scientific community
to analyze it easily. This paper describes the requirements for the software and explores our decisions to use the SolarSoftWare
and Interactive Data Language programming packages, to support both Windows and Unix platforms, and to use object-oriented
programming. We also describe how the data are rapidly disseminated and how ancillary data sets are used to enhance the RHESSI
science. Finally, we give a schematic overview of some of the data flow through the high-level analysis tools. More information
on the data and analysis procedures can be found at the RHESSI Data Center website, http://hesperia.gsfc.nasa.gov/rhessidatacenter.
Supplementary material to this paper is available in electronic form at http://dx.doi.org/10.1023/A:1022444531435 相似文献
12.
A comparison of the photometric properties of Mercury and the Moon is performed, based on their integral phase curves and disk-resolved image data of Mercury obtained with the Swedish Vacuum Solar Telescope. Proper absolute calibration of integral V-band magnitude observations reveals that the near-side of the Moon is 10-15% brighter than average Mercury, and 0-5% brighter for the “bolometric” wavelength range 400-1000 nm. As shown, this is supported by recent estimates of their geometric albedos. Hapke photometric parameters of their surfaces are derived from identical approaches, allowing a contrasting study between their surface properties to be performed. Compared to the average near-side Moon, Mercury has a slightly lower single-scattering albedo, an opposition surge with smaller width and of marginally smaller amplitude, and a somewhat smoother surface with similar porosity. The width of the lobes of the single-particle scattering function are smaller for Mercury, and the backward scattering anisotropy is stronger. In terms of the double Henyey-Greenstein b-c parameter plot, the scattering properties of an average particle on Mercury is closer to the properties of lunar maria than highlands, indicating a higher density of internal scatterers than that of lunar particles. The photometric roughness of Mercury is well constrained by the recent study of Mallama et al. (2002, Icarus 155, 253-264) to a value of about 8°, suggesting that the surfaces sampled by the highest phase angle observations (Borealis, Susei, and Sobkou Planitia) are lunar mare-like in their textural properties. However, Mariner 10 disk brightness profiles obtained at intermediate phase angles indicate a surface roughness of about twice this value. The photometric parameters of the Moon are more difficult to constrain due to limited phase angle coverage, but the best Hapke fits are provided by rather small surface roughnesses. Better-calibrated, multiple-wavelength observations of the integral and disk-resolved brightnesses of both bodies, and obtained at higher phase angle values in the case of the Moon, are urgently needed to arrive at a more consistent picture of the contrasting light scattering properties of their surfaces. 相似文献
13.
X-ray bright points are small dynamic loop structures that are observed all over the solar corona. The high spatial and temporal
resolution of the TRACE instrument allows bright points to be studied in much greater detail than previously possible. This
paper focuses on a specific bright point which occurred for about 20 hours on 13–14 June 1998 and examines its dynamic structure
in detail. This example suggests that the mechanisms that cause bright points to form and evolve are more complex than previously
thought. In this case, reconnection probably plays a major part during the formation and brightening of the loop structure.
However, later on the foot points rotate injecting twist into the bright point which may cause an instability to occur with
dynamic results.
Supplementary material to this paper is available in electronic form at http://dx.doi.org/10.1023/A:1017907406350 相似文献
14.
Izzo Paolo Dell’Elce Lamberto Gurfil Pini Rosengren Aaron J. 《Celestial Mechanics and Dynamical Astronomy》2022,134(2):1-83
We present fully three-dimensional equations to describe the rotations of a body made of a deformable mantle and a fluid core. The model in its essence is similar to that used by INPOP19a (Integration Planétaire de l’Observatoire de Paris) Fienga et al. (INPOP19a planetary ephemerides. Notes Scientifiques et Techniques de l’Institut de Mécanique Céleste, vol 109, 2019), and by JPL (Jet Propulsion Laboratory) (Park et al. The JPL Planetary and Lunar Ephemerides DE440 and DE441. Astron J 161(3):105, 2021. doi:10.3847/1538-3881/abd414), to represent the Moon. The intended advantages of our model are: straightforward use of any linear-viscoelastic model for the rheology of the mantle; easy numerical implementation in time-domain (no time lags are necessary); all parameters, including those related to the “permanent deformation”, have a physical interpretation. The paper also contains: (1) A physical model to explain the usual lack of hydrostaticity of the mantle (permanent deformation). (2) Formulas for free librations of bodies in and out-of spin-orbit resonance that are valid for any linear viscoelastic rheology of the mantle. (3) Formulas for the offset between the mantle and the idealised rigid-body motion (Peale’s Cassini states). (4) Applications to the librations of Moon, Earth, and Mercury that are used for model validation.
相似文献15.
An investigation of the activity of Comet C/1995 O1 (Hale-Bopp) with a thermophysical nucleus model that does not rely on the existence of amorphous ice is presented. Our approach incorporates recent observations allowing to constrain important parameters that control cometary activity. The model accounts for heat conduction, heat advection, gas diffusion, sublimation, and condensation in a porous ice-dust matrix with moving boundaries. Erosion due to surface sublimation of water ice leads to a moving boundary. The movement of the boundary is modeled by applying a temperature remapping technique which allows us to account for the loss in the internal energy of the eroded surface material. These kind of problems are commonly referred to as Stefan problems. The model takes into account the diurnal rotation of the nucleus and seasonal effects due to the strong obliquity of Hale-Bopp as reported by Jorda et al. (Jorda, L., Rembor, K., Lecacheux, J., Colom, P., Colas, F., Frappa, E., Lara, L.M. [1997]. Earth Moon Planets 77, 167-180). Only bulk sublimation of water and CO ice are considered without further assumptions such as amorphous ices with certain amount of occluded CO gas. Confined and localized activity patterns are investigated following the reports of Lederer and Campins (Lederer, S.M., Campins, H. [2002]. Earth Moon Planets 90, 381-389) about the chemical heterogeneity of Hale-Bopp and of Bockelée-Morvan et al. (Bockelée-Morvan, D., Henry, F., Biver, N., Boissier, J., Colom, P., Crovisier, J., Despois, D., Moreno, R., Wink, J. [2009]. Astron. Astrophys. 505, 825-843) about a strong CO source at a latitude of 20°. The best fit to the observations of Biver et al. (Biver, N. et al. [2002]. Earth Moon Planets 90, 5-14) is obtained with a low thermal conductivity of 0.01 W m−1 K−1. This is in agreement with recent results of the Deep Impact mission to 9P/Tempel 1 (Groussin, O., A’Hearn, M.F., Li, J.-Y., Thomas, P.C., Sunshine, J.M., Lisse, C.M., Meech, K.J., Farnham, T.L., Feaga, L.M., Delamere, W.A. [2007]. Icarus 187, 16-25) and with previous thermal simulations (Kührt, E. [1999]. Space Sci. Rev. 90, 75-82). The water production curve matches the production rates well from −4 AU pre-perihelion to the outgoing leg while the model does not reproduce so well the water production beyond 4 AU pre-perihelion. The CO production curve is a good fit to the measurements of Biver et al. (2002) over the whole measured heliocentric range from −7 AU pre- to 15 AU post-perihelion. 相似文献
16.
Many papers are devoted to the prediction of radiation conditions on board of a spacecraft (Pichkhadze et al., 2004; Khamidullina et al., 2008; 2012), and a number of software systems for corresponding calculations have been developed: the US information system CREME96 (https://creme.isde.vander-bilt.edu/); European SPENVIS (http://www.spenvis.oma.be/intro.php); Russian SEREIS (Kuznetsov et al., 2001; Model’ kosmosa, 2007) and COSRAD (http://cosrad.sinp.msu.ru/manual.html; Kuznetsov et al., 2011) based on the models of the radiation environment in near-Earth space (Bashkirov et al., 1998; Nymmik, 2004; Model’ kosmosa, 2007; Kuznetsov et al., 2011). In this paper we propose a simple calculation algorithm of short-term (for a few days) forecasting of dynamics of the radiation dose on the International Space Station (ISS) in radiation environment undisturbed by solar proton events. This algorithm does not use radiation environment models and detailed ballistic calculations, while it uses data of the onboard radiation monitoring system (RMS) and empirical relations, obtained for ISS orbital motion. 相似文献
17.
A new database of all astrometric observations of moons of asteroids is offered. It has a simple structure and is accessible through the Internet. Regular database updating is provided when new observational results occur in publications. The database is located at the sites of the Natural Satellites Data Center created as a result of collaboration between the Sternberg Astronomical Institute of Moscow State University and the Institut de Mécanique Céleste et de Calcul des Ephémérides (IMCCE). The database addresses in the Internet are https://doi.org/www.sai.msu.ru/neb/nss/indexr.htm and https://doi.org/nsdb.imcce.fr/obsposrespectively. On entering these sites, we need to select one of three languages, the Observation item, and the Astrometric positions of asteroids with moons item. The observational data are provided here with explanations and hyperlinks to the publications in the bibliographic database SAO/NASA Astrophysics Data System (ADS) Abstract Service. 相似文献
18.
The solar activity can be quantified by solar modulation parameter Φ that affects the heliospheric magnetic field. This activity influences the intensity of the galactic cosmic ray (GCR) particle flux within the solar system, and consequently, the differential primary particle spectra depend on the solar modulation parameter Φ (MeV). The modulation parameter Φ shows spatial and temporal variations (Leya and Masarik 2009). Some of the solar activity variations are cyclic and result in measurable effects as for example the 11‐year solar cycle. Variations in solar activity only induce small effects on the production of long‐lived cosmogenic radionuclides. This is due to the fact that activities measured in meteorites usually correspond to saturation values and represent long‐term average values. Long‐lived radionuclides often require millions of years of irradiation by GCR to reach saturation and therefore activity cycles average out. In contrast, one can expect strongly pronounced variations for saturation values caused by primary flux intensity variations, if short‐lived radionuclides with half‐lives ranging from days to a few years are investigated. Short‐lived cosmogenic nuclides were the subject of many experimental and theoretical investigations (e.g., Evans et al. 1982; Spergel et al. 1986; Neumann et al. 1997; Komura et al. 2002; Laubenstein et al. 2012). The aim of this work is to develop formulae for calculating production rates of radionuclides with short half‐life, taking into account temporal variations in the primary cosmic ray intensity. The developed formulae were applied to the Kosice and Chelyabinsk meteorites. The results for the Ko?ice meteorite were already published (Povinec et al. 2015). Here, we give a full explanation of underlying model. 相似文献
19.
S. Biswas N. Durgaprasad R. K. Singh M. N. Vahia J. S. Yadav A. Dutta J. N. Goswami 《Journal of Astrophysics and Astronomy》1994,15(1):85-94
The Anuradha cosmic ray experiment in Spacelab-3, flown in the orbit at 350 km with an inclination of 57° for about six days, was used to measure the low energy galactic cosmic ray (GCR) heavy ions using a specially designed CR-39 detector module incorporating the arrival time information of the particles. The abundances of sub-iron (Sc-Cr) and iron particles in the low energy interval of 30–300 MeV/N were determined from the measurements made in four different depths of the CR-39 detector module of 150 layers. From these studies we obtained sub-iron (Sc-Cr) to iron abundance ratios of 0.8 to 1.2 in 30–300 MeV/N energy range. It is found that these ratios are enhanced by a factor of two as compared to interplanetary ratios of about 0.5. It is shown that the enhancement of the ratio inside the earth’s magnetosphere is probably due to the degree of ionization of low energy Sc to Cr and Fe ions in the galactic cosmic rays and to the rigidity filtering effects of the geomagnetic field. Further studies are needed to understand fully the phenomena and their implications. 相似文献
20.
A broadband radio spectrometer has been put into operation at Bleien, Switzerland, to register the flare emission of the full
Sun. In the frequency range of operation, 0.1 to 4.0 GHz, both modes of circular polarization are recorded continuously. The
new system, Phoenix-2, has been developed from the experience with the previous Phoenix spectrometer. Improved, computer-controlled
focal hardware allows now a complete daily calibration, a more sophisticated calibration procedure, and monitoring of all
essential instrumental and environmental parameters. Calibrated data are now usually available the day after observation and
are accessible through the Internet. The scientific improvements include a larger frequency range of observation, a larger
number of completely recorded events due to full-day registration, more accurate measurements, particularly in circular polarization,
and more reliable operation. First observations are presented and quantitative results comparing the calibration with single
frequency instruments are reported.
Supplementary material to this paper is available in electronic form at http://dx.doi.org/10.1023/A:1005194314845 相似文献