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1.
We study the capture and crossing probabilities in the 3:1 mean motion resonance with Jupiter for a small asteroid that migrates from the inner to the middle Main Belt under the action of the Yarkovsky effect. We use an algebraic mapping of the averaged planar restricted three-body problem based on the symplectic mapping of Hadjidemetriou (Celest Mech Dyn Astron 56:563–599, 1993), adding the secular variations of the orbit of Jupiter and non-symplectic terms to simulate the migration. We found that, for fast migration rates, the captures occur at discrete windows of initial eccentricities whose specific locations depend on the initial resonant angles, indicating that the capture phenomenon is not probabilistic. For slow migration rates, these windows become narrower and start to accumulate at low eccentricities, generating a region of mutual overlap where the capture probability tends to 100 %, in agreement with the theoretical predictions for the adiabatic regime. Our simulations allow us to predict the capture probabilities in both the adiabatic and non-adiabatic cases, in good agreement with results of Gomes (Celest Mech Dyn Astron 61:97–113, 1995) and Quillen (Mon Not RAS 365:1367–1382, 2006). We apply our model to the case of the Vesta asteroid family in the same context as Roig et al. (Icarus 194:125–136, 2008), and found results indicating that the high capture probability of Vesta family members into the 3:1 mean motion resonance is basically governed by the eccentricity of Jupiter and its secular variations.  相似文献   

2.
We carry out the adaptive mesh refinement (AMR) implementation of our solar–interplanetary space-time conservation element and solution element (CESE) magnetohydrodynamic model (SIP–CESE MHD model) using a six-component grid system (Feng, Zhou, and Wu, Astrophys. J. 655, 1110, 2007; Feng et al., Astrophys. J. 723, 300, 2010). By transforming the governing MHD equations from the physical space (x,y,z) to the computational space (ξ,η,ζ) while retaining the form of conservation (Jiang et al., Solar Phys. 267, 463, 2010), the SIP–AMR–CESE MHD model is implemented in the reference coordinates with the aid of the parallel AMR package PARAMESH available at http://sourceforge.net/projects/paramesh/ . Meanwhile, the volumetric heating source terms derived from the topology of the magnetic-field expansion factor and the minimum angular separation (at the photosphere) between an open-field foot point and its nearest coronal-hole boundary are also included. We show the preliminary results of applying the SIP–AMR–CESE MHD model for simulating the solar-wind background of different solar-activity phases by comparison with SOHO observations and other spacecraft data from OMNI. Our numerical results show overall good agreements in the solar corona and in interplanetary space with these multiple-spacecraft observations.  相似文献   

3.
The analytical techniques of the Nekhoroshev theorem are used to provide estimates on the coefficient of Arnold diffusion along a particular resonance in the Hamiltonian model of Froeschlé et al. (Science 289:2108–2110, 2000). A resonant normal form is constructed by a computer program and the size of its remainder ||R opt || at the optimal order of normalization is calculated as a function of the small parameter ${\epsilon}$ . We find that the diffusion coefficient scales as ${D \propto ||R_{opt}||^3}$ , while the size of the optimal remainder scales as ${||R_{opt}|| \propto {\rm exp}(1/\epsilon^{0.21})}$ in the range ${10^{-4} \leq \epsilon \leq 10^{-2}}$ . A comparison is made with the numerical results of Lega et al. (Physica D 182:179–187, 2003) in the same model.  相似文献   

4.
We present a method for fast and accurate azimuth disambiguation of vector magnetogram data regardless of the location of the analyzed region on the solar disk. The direction of the transverse field is determined with the principle of minimum deviation of the field from the reference (potential) field. The new disambiguation (NDA) code is examined on the well-known models of Metcalf et al. (Solar Phys. 237, 267, 2006) and Leka et al. (Solar Phys. 260, 83, 2009), and on an artificial model based on the observed magnetic field of AR 10930 (Rudenko, Myshyakov, and Anfinogentov, Astron. Rep. 57, 622, 2013). We compare Hinode/SOT-SP vector magnetograms of AR 10930 disambiguated with three codes: the NDA code, the nonpotential magnetic-field calculation (NPFC: Georgoulis, Astrophys. J. Lett. 629, L69, 2005), and the spherical minimum-energy method (Rudenko, Myshyakov, and Anfinogentov, Astron. Rep. 57, 622, 2013). We then illustrate the performance of NDA on SDO/HMI full-disk magnetic-field observations. We show that our new algorithm is more than four times faster than the fastest algorithm that provides the disambiguation with a satisfactory accuracy (NPFC). At the same time, its accuracy is similar to that of the minimum-energy method (a very slow algorithm). In contrast to other codes, the NDA code maintains high accuracy when the region to be analyzed is very close to the limb.  相似文献   

5.
Recently, 3D STEREO observations explained the 3D structure of EUV waves. Patsourakos and Vourlidas (Astrophys. J. 700, L182, 2009), Veronig et al. (Astrophys. J. 716, L57, 2010) and Selwa, Poedts, and DeVore (Astrophys. J. 747, L21, 2012) reported on the dome-shaped EUV waves resulting from different events. Here, we model, by means of 3D MHD simulations, the formation of dome-shaped EUV waves in rotating active regions (ARs). The numerical simulations are initialized with idealized (multi-)dipolar coronal (low β) configurations. Next, we apply a sheared rotational motion to the central parts of all the positive and negative flux regions at the photospheric boundary. As a result, the flux tubes connecting the flux sources become twisted. We find that in all the studied configurations of idealized ARs, the rotating motion results in a dome-shaped structure originating from the AR. However, the shape of the dome depends on the initial configuration (topology of the AR). The initial stage of the wave evolution consists of multiple fronts that later merge together forming a single wave. The observed EUV wave propagates nearly isotropically on the disk and also in the upward direction. We remark that the initial stage of the evolution is determined by the driver and not caused by a magnetic reconnection event. At a later stage, however, the wave propagates freely. We study the different wave properties resulting from different driver speeds and find that independent of the initial AR topology the 3D dome-shaped wave is excited in the system. The symmetry of the 3D dome depends on the topology of the AR and on the duration of the driver. The EUV wave triggered is independent of the temporal profile of the driver. However, the properties of the wave (speed, sharpness of the cross-section, etc.) depend on the type of the trigger.  相似文献   

6.
G. J. D. Petrie 《Solar physics》2014,289(10):3663-3680
It is shown that expressions for the global Lorentz force associated with a flaring active region derived by Fisher et al. (Solar Phys. 277, 59, 2012) can be used to estimate the Lorentz-force changes for strong fields in large structures over photospheric subdomains within active regions. Gary’s (Solar Phys. 203, 71, 2001) model for the stratified solar atmosphere is used to demonstrate that in large-scale structures with typical horizontal magnetic length scale ??300 km and with strong magnetic fields (≥?1 kG at the τ=1 opacity layer at 5000 Å), the Lorentz force acting on the photosphere may be approximated by a surface integral based on photospheric boundary data alone. These conditions cover many of the sunspot fields and major neutral lines that have been studied using Fisher et al.’s (2012) expressions over the past few years. The method gives a reasonable estimate of flare-related Lorentz-force changes based on photospheric magnetogram observations provided that the Lorentz-force changes associated with the flare have a lasting effect on the observed fields, and they are not immediately erased by post-flare equilibration processes.  相似文献   

7.
We examine the propagation of Alfvén waves in the solar atmosphere. The principal theoretical virtues of this work are: (i) The full wave equation is solved without recourse to the small-wavelength eikonal approximation (ii) The background solar atmosphere is realistic, consisting of an HSRA/VAL representation of the photosphere and chromosphere, a 200 km thick transition region, a model for the upper transition region below a coronal hole (provided by R. Munro), and the Munro-Jackson model of a polar coronal hole. The principal results are:
  1. If the wave source is taken to be near the top of the convection zone, where n H = 5.2 × 1016 cm?3, and if B ⊙ = 10.5 G, then the wave Poynting flux exhibits a series of strong resonant peaks at periods downwards from 1.6 hr. The resonant frequencies are in the ratios of the zeroes of J 0, but depend on B ⊙, and on the density and scale height at the wave source. The longest period peaks may be the most important, because they are nearest to the supergranular periods and to the observed periods near 1 AU, and because they are the broadest in frequency.
  2. The Poynting flux in the resonant peaks can be large enough, i.e. P ⊙ ≈ 104–105 erg cm?2s?1, to strongly affect the solar wind.
  3. ¦δv¦ and ¦δB¦ also display resonant peaks.
  4. In the chromosphere and low corona, ¦δv ≈ 7–25 kms?1 and ¦δB¦ ≈0.3–1.0 G if P ⊙≈104-105 erg cm?2s?1.
  5. The dependences of ¦δv¦ and ¦δB¦ on height are reduced by finite wavelength effects, except near the wave source where they are enhanced.
  6. Near the base, ¦δB¦ ≈ 350–1200 G if P ⊙ ～- 104–105. This means that nonlinear effects may be important, and that some density and vertical velocity fluctuations may be associated with the Alfvén waves.
  7. Below the low corona most wave energy is kinetic, except near the base where it becomes mostly magnetic at the resonances.
  8. ?0 < δv 2 > v A or < δB 2 > v A/4π are not good estimators of the energy flux.
  9. The Alfvén wave pressure tensor will be important in the transition region only if the magnetic field diverges rapidly. But the Alfvén wave pressure can be important in the coronal hole.
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8.
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9.
The Helioseismic and Magnetic Imager (HMI) instrument onboard the Solar Dynamics Observatory (SDO) satellite is designed to produce high-resolution Doppler-velocity maps of oscillations at the solar surface with high temporal cadence. To take advantage of these high-quality oscillation data, a?time?–?distance helioseismology pipeline (Zhao et al., Solar Phys. submitted, 2010) has been implemented at the Joint Science Operations Center (JSOC) at Stanford University. The aim of this pipeline is to generate maps of acoustic travel times from oscillations on the solar surface, and to infer subsurface 3D flow velocities and sound-speed perturbations. The wave travel times are measured from cross-covariances of the observed solar oscillation signals. For implementation into the pipeline we have investigated three different travel-time definitions developed in time?–?distance helioseismology: a Gabor-wavelet fitting (Kosovichev and Duvall, SCORE’96: Solar Convection and Oscillations and Their Relationship, ASSL, Dordrecht, 241, 1997), a?minimization relative to a reference cross-covariance function (Gizon and Birch, Astrophys. J. 571, 966, 2002), and a linearized version of the minimization method (Gizon and Birch, Astrophys. J. 614, 472, 2004). Using Doppler-velocity data from the Michelson Doppler Imager (MDI) instrument onboard SOHO, we tested and compared these definitions for the mean and difference travel-time perturbations measured from reciprocal signals. Although all three procedures return similar travel times in a quiet-Sun region, the method of Gizon and Birch (Astrophys. J. 614, 472, 2004) gives travel times that are significantly different from the others in a magnetic (active) region. Thus, for the pipeline implementation we chose the procedures of Kosovichev and Duvall (SCORE’96: Solar Convection and Oscillations and Their Relationship, ASSL, Dordrecht, 241, 1997) and Gizon and Birch (Astrophys. J. 571, 966, 2002). We investigated the relationships among these three travel-time definitions, their sensitivities to fitting parameters, and estimated the random errors that they produce.  相似文献   

10.
Recent magnetic modeling efforts have shown substantial misalignment between theoretical models and observed coronal loop morphology as observed by STEREO/EUVI, regardless of the type of model used. Both potential field and non-linear force-free field (NLFFF) models yielded overall misalignment angles of 20??C?40 degrees, depending on the complexity of the active region (Sandman et al., Solar Phys. 259, 1, 2009; DeRosa et al., Astrophys. J. 696, 1780, 2009) We demonstrate that with new, alternative forward-fitting techniques, we can achieve a significant reduction in the misalignment angles compared with potential field source surface (PFSS) models and NLFFF models. Fitting a series of submerged dipoles to the field directions of stereoscopically triangulated loops in four active regions (30 April, 9 May, 19 May, and 11 December 2007), we find that 3??C?5 dipoles per active region yield misalignment angles of ???11°??C?18°, a factor of two smaller than those given by previously established extrapolation methods. We investigate the spatial and temporal variation of misalignment angles with subsets of loops for each active region, as well as loops observed prior to and following a flare and filament eruption, and find that the spatial variation of median misalignment angles within an active region (up to 75%) exceeds the temporal variation associated with the flare (up to 40%). We also examine estimates of the stereoscopic error of our analysis. The corrected values yield a residual misalignment of 7°??C?13°, which is attributed to the non-potentiality due to currents in the active regions.  相似文献   

11.
We derive an analytical approximation of nonlinear force-free magnetic field solutions (NLFFF) that can efficiently be used for fast forward-fitting to solar magnetic data, constrained either by observed line-of-sight magnetograms and stereoscopically triangulated coronal loops, or by 3D vector-magnetograph data. The derived NLFFF solutions provide the magnetic field components B x (x), B y (x), B z (x), the force-free parameter α(x), the electric current density j(x), and are accurate to second-order (of the nonlinear force-free α-parameter). The explicit expressions of a force-free field can easily be applied to modeling or forward-fitting of many coronal phenomena.  相似文献   

12.
We present some analytical results about the existence of periodic orbits for the planar restricted three body problem with dissipation considered recently by Celletti et?al. (CMDA 109, 265, 2011) We show that, under fairly general conditions on the dissipation term, the circular orbits cannot be continued to the dissipative framework. Moreover, we give general conditions for the occurrence or not of a Hopf bifurcation around the libration points L 4 and L 5. Our results are consistent with the numerical findings of Celletti et?al.  相似文献   

13.
We investigate multi-spacecraft observations of the 17 January 2010 solar energetic particle event. Energetic electrons and protons have been observed over a remarkable large longitudinal range at the two STEREO spacecraft and SOHO, suggesting a longitudinal spread of nearly 360 degrees at 1?AU. The flaring active region, which was on the backside of the Sun as seen from Earth, was separated by more than 100 degrees in longitude from the magnetic footpoints of each of the three spacecraft. The event is characterized by strongly delayed energetic particle onsets with respect to the flare and only small or no anisotropies in the intensity measurements at all three locations. The presence of a coronal shock is evidenced by the observation of a type II radio burst from the Earth and STEREO-B. In order to describe the observations in terms of particle transport in the interplanetary medium, including perpendicular diffusion, a 1D model describing the propagation along a magnetic field line (model 1) (Dr?ge, Astrophys. J. 589, 1027??C?1039, 2003) and the 3D propagation model (model 2) by Dr?ge et?al. (Astrophys. J. 709, 912??C?919, 2010) including perpendicular diffusion in the interplanetary medium have been applied. While both models are capable of reproducing the observations, model 1 requires injection functions at the Sun of several hours. Model 2, which includes lateral transport in the solar wind, reveals high values for the ratio of perpendicular to parallel diffusion. Because we do not find evidence for unusual long injection functions at the Sun, we favor a scenario with strong perpendicular transport in the interplanetary medium as an explanation for the observations.  相似文献   

14.
Linear wave patterns in Jupiter's clouds with wavelengths strongly clustered around 300 km are commonly observed in the planet's equatorial atmosphere (F. M. Flasar and P. J. Gierasch, 1986, J. Atmos. Sci.43, 2683-2707). We propose that the preferred wavelength is related to the thickness of an unstable shear layer within the clouds (A. P. Ingersoll and D. W. Koerner 1989, Bull. Am. Astron. Soc.21, 943). We numerically analyze the linear stability of wavelike disturbances that have nonzero horizontal phase speeds in Jupiter's atmosphere and find that, if the static stability in the shear layer is very low (but still nonnegative), a deep vertical shear layer like the one measured by the Galileo probe (D. H. Atkinson et al. 1998, J. Geophys. Res.103, 22911-22928) can generate the instabilities. The fastest growing waves grow exponentially within an hour, and their wavelengths match the observations. Close to zero values of static stability that permit the growth of instabilities are within the range of values measured by the Galileo probe in a hot spot (A. Seiff et al. 1998, J. Geophys. Res.103, 22857-22889). Our model probes Jupiter's equatorial atmosphere below the cloud deck and suggests that thick regions of wind shear and low static stability exist outside hot spots.  相似文献   

15.
Multi-wavelength studies of energetic solar flares with seismic emissions have revealed interesting common features between them. We studied the first GOES X-class flare of Solar Cycle 24, as detected by the Solar Dynamics Observatory (SDO). For context, seismic activity from this flare (SOL2011-02-15T01:55-X2.2, in NOAA AR 11158) has been reported by Kosovichev (Astrophys. J. Lett., 734, L15, 2011) and Zharkov et?al. (Astrophys. J. Lett., 741, L35, 2011). Based on Dopplergram data from the Helioseismic and Magnetic Imager (HMI), we applied standard methods of local helioseismology in order to identify the seismic sources in this event. RHESSI hard X-ray data are used to check the correlation between the location of the seismic sources and the particle-precipitation sites in during the flare. Using HMI magnetogram data, the temporal profile of fluctuations in the photospheric line-of-sight magnetic field is used to estimate the magnetic-field change in the region where the seismic signal was observed. This leads to an estimate of the work done by the Lorentz-force transient on the photosphere of the source region. In this instance, this is found to be a significant fraction of the acoustic energy in the attendant seismic emission, suggesting that Lorentz forces can contribute significantly to the generation of sunquakes. However, there are regions in which the signature of the Lorentz force is much stronger, but from which no significant acoustic emission emanates.  相似文献   

16.
A. Brunini  M.D. Melita 《Icarus》2002,160(1):32-43
We study the effects of a Mars-like planetoid with a semimajor axis at about ∼60 AU orbiting embedded in the primordial Edgeworth-Kuiper belt (EKB). The origin of such an object can be explained in the framework of our current understanding of the origin of the outer Solar System, and a scenario for the orbital transport mechanism to its present location is given. The existence of such an object would produce a gap in the EKB distribution with an edge at about 50 AU, which seems to be in agreement with the most recent observations. No object at low eccentricity with semimajor axis beyond 50 AU has been detected so far, even though the present observing capabilities would allow an eventual detection (B. Gladman et al. 1998, Astron. J.116, 2042-2054; D. Jewitt et al. 1998, Astron. J.115, 2125-2135; E. I. Chiang and M. E. Brown 1999, Astron. J.118, 1411-1422; R. L. Allen et al. 2000, Astrophys. J.549, 241-244; C. A. Trujillo et al. 2001, Astron. J.122, 457-473; B. Gladman et al. 2001, Astron. J.122, 1051-1066; C. A. Trujillo and M. E. Brown 2001, Astrophys. J.554, 95-98). Finally, ranges for the magnitude and proper motion of the proposed object are given.  相似文献   

17.
The first near-side X-class flare of Solar Cycle 24 occurred in February 2011 (SOL2011-02-05T01:55) and produced a very strong seismic response in the photosphere. One sunquake was reported by Kosovichev (Astrophys. J. Lett. 734, L15, 2011), followed by the discovery of a second sunquake by Zharkov, Green, Matthews et al. (Astrophys. J. Lett. 741, L35, 2011). The flare had a two-ribbon structure and was associated with a flux-rope eruption and a halo coronal mass ejection (CME) as reported in the CACTus catalogue. Following the discovery of the second sunquake and the spatial association of both sources with the locations of the feet of the erupting flux rope (Zharkov, Green, Matthews et al., Astrophys. J. Lett. 741, L35, 2011), we present here a more detailed analysis of the observed photospheric changes in and around the seismic sources. These sunquakes are quite unusual, taking place early in the impulsive stage of the flare, with the seismic sources showing little hard X-ray (HXR) emission, and strongest X-ray emission sources located in the flare ribbons. We present a directional time–distance diagram computed for the second source, which clearly shows a ridge corresponding to the travelling acoustic-wave packet and find that the sunquake at the second source happened about 45 seconds to one minute earlier than the first source. Using acoustic holography we report different frequency responses of the two sources. We find strong downflows at both seismic locations and a supersonic horizontal motion at the second site of acoustic-wave excitation.  相似文献   

18.
Long-term variations of solar differential rotation and sunspot activity are investigated through re-analyzing the data on parameters of the differential-rotation law obtained by Makarov, Tlatov, and Callebaut (Solar Phys. 170, 373, 1997), Javaraiah, Bertello, and Ulrich (Astrophys. J. 626, 579, 2005a; Solar Phys. 232, 25, 2005b), and Javaraiah et al. (Solar Phys. 257, 61, 2009). Our results indicate that the solar-surface-rotation rate at the Equator (indicated by the A-parameter of the standard solar-rotation law) shows a secular decrease since Cycle 12 onwards, given by about 1?–?1.5×10?3 (deg?day?1?year?1). The B-parameter of the standard differential-rotation law seems to also show a secular decrease since Cycle 12 onwards, but of weak statistical significance. The rotation rate averaged over latitudes 0°?–?40° does not show a secular trend of statistical significance. Moreover, the average sunspot area shows a secular increase of statistical significance since Cycle 12 onwards, while a negative correlation is found between the level of sunspot activity (indicated by the average sunspot area) and the solar equatorial rotation on long-term scales.  相似文献   

19.
We identify 565 coronal mass ejections (CMEs) between January 2007 and December 2010 in observations from the twin STEREO/SECCHI/COR2 coronagraphs aboard the STEREO mission. Our list is in full agreement with the corresponding SOHO/LASCO CME Catalog ( http://cdaw.gsfc.nasa.gov/CME_list/ ) for events with angular widths of 45° and up. The monthly event rates behave similarly to sunspot rates showing a three- to fourfold rise between September 2009 and March 2010. We select 51 events with well-defined white-light structure and model them as three-dimensional (3D) flux ropes using a forward-modeling technique developed by Thernisien, Howard and Vourlidas (Astrophys. J. 652, 763??C?773, 2006). We derive their 3D properties and identify their source regions. We find that the majority of the CME flux ropes (82?%) lie within 30° of the solar equator. Also, 82?% of the events are displaced from their source region, to a lower latitude, by 25° or less. These findings provide strong support for the deflection of CMEs towards the solar equator reported in earlier observations, e.g. by Cremades and Bothmer (Astron. Astrophys. 422, 307??C?322, 2004).  相似文献   

20.
The original coronal index of the solar activity (CI) has been constructed on the basis of ground-based measurements of the intensities of the coronal line of 530.3 nm (Rybanský in Bull. Astron. Inst. Czechoslov., 28, 367, 1975; Rybanský et al. in J. Geophys. Res., 110, A08106, 2005). In this paper, CI is compared with the EUV measurements on the CELIAS/SEM equipment based on the same idea as the original idea of the coronal index. The correlation is very good for the period 1996?–?2005 (r=0.94 for daily values). The principal result of this paper is the introduction of the modified coronal index (MCI) which in all uses and contexts can replace the existing CI index. Daily MCI values extend over a time period of six solar activity cycles. Future MCI measurements will be derived from more reliable measurements made by space-based observatories that are not influenced by the weather. MCI measurements are and will continue to be archived at the web site of the Slovak Central Observatory in Hurbanovo ( http://www.suh.sk/obs/vysl/MCI.htm ).  相似文献   

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