linkages between the atmosphere on the Earth and sun Phần 10 potx

Interplanetary Consequences of a Large CME 491 10 1 19 20 21 22 Hours MHz 10 7 30 25 20 15 10 5 0 frequency (Hz) SCET R AU 20:00 6.68 6.68 6.68 6.68 21:00 22:00 23:00 dB above background 10 6 10 5 Fig. 2 Radio spectra from the WAVES and Cassini missions. Cassini was located at 8.7 AU 10 4 1000 proton flux > 1Mev proton flux > 5Mev proton flux > 10Mev proton flux > 30Mev proton flux > 50Mev proton flux > 60Mev proton flux > 100Mev Shock at 1 AU 100 10 0.1 4 d 12 h 5 d 00 h 6 d 00 h 7 d 00 h 12 h Day and Time(UT) Flux (log) 12 h 12 h 1 Fig. 3 Particle profiles in different energy bands 492 M. Lahkar et al. Fig. 4 Ooty IPS images showing the current sheet location (top left), CME deflection by the coronal hole (top right), CME compression of the solar wind (bottom left), and CME propagation (bottom right). The Sun is located at the center of each image. The two images at top right represent solar-wind speed; the others represent density Density DST Bz By Bx Phi Theta B Temperature Speed 8 4 0 0 5 0 0 5 0 0 16 8 6 x 10 5 3 x 10 5 560 480 6.5 7 7.5 8 Date Nov2003 5 –5 –5 –30 –50 –200 6 B Theta Phi Br Bt Bn Density Temperature Speed 4 2 5 0 –5 –5 –2 –4 4 5 –5 2 900 600 12 14 16 Date Nov2003 18 1 1.6 x 10 6 8 x 10 5 0 0 5 2 0 0 Fig. 5 1-AU and Ulysses hourly averages of solar wind parameters As Ulysses was favorably located in the CME propagation direction, it could record the nose part of the CME and its shock, as indicated by a speed value of over 900 km s 1 at 5 AU. At Earth, the shock speed was below 600 km s 1 , suggest- ing that the eastern tail swept the Earth. From these measurements we infer a speed profile V  R 0:4 to Earth. However, the deceleration V  R 0:2 out to 5 AU near Ulysses implies gradual decline in speed along the CME propagation direc- tion, which is in good agreement with the IPS measurements. Interplanetary Consequences of a Large CME 493 3Conclusion Our study shows the characteristics of a fast-moving CME and its interactions with transient and solar-wind structures at different distances from the Sun with good consistency between diverse diagnostics. The enhancement in radio emission and production of high-energy particles suggest that the magnetic field associated with the CME was strong. The gradual decline in CME speed suggests that the inter- nal magnetic energy of the CME supported its propagation, including expansion in overcoming the aerodynamical drag imposed by the ambient solar wind (e.g., Manoharan 2006). Acknowledgment We thank the Cassini, GOES, SOHO, TRACE, Ulysses, Wind, and OMNI- database teams for making their data available on the web. We also thank B. Jackson and the UCSD team for the IPS tomography analysis package. M. Lahkar thanks the National Centre for Radio Astrophysics (TIFR) for financial support. This work is partially supported by the CAWSES–India program sponsored by the Indian Space Research Organisation (ISRO). References Bougeret, J L., Kaiser, M. L., Kellogg, P. J., et al. 1995, Space Sci. Rev., 71, 231 Brueckner, G. E., Howard, R. A., Koomen, M. J., et al. 1995, Solar Phys., 162, 357 Gargate, L., Bingham, R., Fonseca, R. A., Silva, L. O. 2006, AGU Fall Meeting Abstracts, B1518 Gopalswamy, N., Yashiro, S., Kaiser, M. L., Howard, R. A., Bougeret, J L. 2001, ApJ, 548, L91 Kliore, A. J., Anderson, J. D., Armstrong, J. W., et al. 2004, Space Sci. Rev., 115, 1 Manoharan, P. K. 2006, Solar Phys., 235, 345 Manoharan, P. K., Kundu, M. R. 2003, ApJ, 592, 597 Manoharan, P. K., Tokumaru, M., Pick, M., et al. 2001, ApJ, 559, 1180 Solar System Resonances on Light-Travel Time Scales Set Up before Proto-Sun’s Nuclear Ignition M.H. Gokhale Abstract A scenario is presented showing how solar-system resonances on time scales of light travel could have got set up before the onset of nuclear reactions in the proto-Sun. Such resonances may expedite the onset of nuclear ignition in the proto-Sun and the redistribution and loss of the proto-Sun’s angular momentum. 1 Introduction To ensure compatibility between models of solar variability phenomena and the standard model (SSM) of the Sun’s mean structure and evolution, one must construct a hydrodynamic solar model (HDSM) whose mean structure equals the SSM and whose hydrodynamic state keeps producing acoustic waves and toroidal magnetic fields whose dissipation produces solar-like variability phenomena. The differential rotation that is needed to produce toroidal magnetic fields may be maintained by deposition of angular momentum by g-mode waves at loci of absorption. The main- tenance of these waves (and of acoustic waves) needs maintenance of a spectrum of normal-mode oscillations of the HDSM’s mass elements (i.e., oscillations with frequencies of the normal modes of the SSM). I suggest that the power-input needed to maintain this spectrum may originate from gravitational energy–momentum exchanges of the HDSM’s mass elements with the planets through resonances on time scales of planet-to-Sun speed-of-light travel time (e.g., about 43 min between the Sun and Jupiter). This suggestion is based on the facts that the frequencies of many solar acoustic modes lie in the 1=T P range for the inner planets, where T P is the light-travel time per planet, and that the frequencies of many solar g-modes lie in the 360–410Hz range perpetually traversed up and down by 1=T J as Jupiter moves in its elliptic orbit. This sugges- tion leads to the question how such resonances get set up initially. In this paper, I propose a mechanism setting up such resonances in the proto-solar system which M.H. Gokhale (  ) 205 Sairang Aptts, New D. P. Road, Kothrud, Pune 311038, India S.S. Hasan and R.J. Rutten (eds.), Magnetic Coupling between the Interior and Atmosphere of the Sun, Astrophysics and Space Science Proceedings, DOI 10.1007/978-3-642-02859-5 65, c  Springer-Verlag Berlin Heidelberg 2010 494 Solar System Resonances 495 may also expedite the onset of nuclear ignition near the proto-Sun’s center as well as redistribution and loss of the proto-Sun’s angular momentum. 2 Fourier Frequencies in Momentum Transfer Resonances on time scales of solar-system light travel are possible under the working hypothesis that the energy–momentum exchanges between the solar mass elements and the planets can be represented by waves with periodicities equal to the respective light-travel times and with amplitudes consistent with PPN expressions for the accelerations used in the standard ephemeris. The standard theory of the origin of the solar system (cf. Shu et al. 1993; Boss 1998) says that the latter was formed by the break-up of a circum-solar parent disk into the proto-Sun and proto-planetary rings. Consider the turbulent gravitational dynamics of the parent-disk’s earlier evolution that led to this break-up. Let P k , with k D 1;2;:::, represent the disk mass elements that contributed to mass element P of ring P ,andletm i represent a mass element of the proto-Sun. Throughout the evolution, small changes in the energy and momentum of P k at each instant of time t and the associated changes in the energy and momentum of m i must both be spread over an interval of length T D r.P k ;m i ;t/=c around t, with c the velocity of light. Let f.P ! m i ;t/ represent the rate at which m i receives gravitational momentum from any P k during the interval .t T=2;t CT=2/. Along with each r.P k ;m i ;t/, the interval-length T.P k ;m i ;t/ and the light travel time pro- file (LTTP) of the rate f during this interval evolve both on longer time scales. Turbulence in the parent disk couples such LTTPs mutually during their evolution, so that the LTTP of every f during a given light-travel interval will contain ups and downs covering a wide range of frequencies, including 1=T .P k ;m i ;t/and depending on the locations of P 1 ;P 2 ;:::relative to m i . While different mass elements merge to form mass element P in ring P and while all m i converge to form the proto-Sun, the wide range of the Fourier frequencies of the LTTP of each f shrinks towards  p D c=R P ,whereR P is the average radius of the result- ing ring P . Ultimately, the Fourier frequencies of the LTTP of each particular rate f.P ! m i ;t/of momentum supply will lie in a band of small width, say  P , around each respective  P D c=R P . This width will depend on the initial locations of the mass elements but will be much less than  P as the thickness of the resulting ring is much less than R P . Each term in the Fourier expansion of the resulting LTTP of each f over each light-travel interval T will be as if provided by a momentum wave of period T propagating from P to m i . Thus, the energy–momentum exchanges between the Sun’s mass elements and the planetary rings under the resonances on time scales of light-travel. 496 M.H. Gokhale 3 Resonance Set-Up During the Approach to and Onset of Steady State Before nuclear ignition, the only power source for the proto-Sun’s luminosity on dynamical time scales would be the dissipation of its hydrodynamic and MHD flows. Hence, for the proto-Sun to approach a steady state with internal momen- tum equilibrium as well as internal power balance, the flows in the proto-Sun will have to be admissible under the approached mean structure (i.e., must be the nor- mal modes of the approached mean structure), and also must be excitable by the momentum-input rates f . Therefore, the proto-Sun must approach a mean structure with normal mode frequencies within the Fourier bands of the f ’s. Thus, planetary- system light-travel resonances would be set up even before the onset of nuclear reactions. Once the proto-Sun reaches steady state, the further evolution of its internal struc- ture would imply slow evolution of its normal modes with coupled evolution of the proto-planetary rings in the presence of these resonances. The resonances will expe- dite the disposal of the proto-solar-system’s gravitational energy through the decay of the normal mode waves at the boundaries of their propagation ranges within the proto-Sun. The resonant decay of the g-mode waves will expedite transport of an- gular momentum between the boundaries of their propagation ranges, leading to steep differential rotation at these boundaries and loss of angular momentum. The g-mode decay will also lead to enhanced heating at the inner boundaries, expediting the onset of nuclear ignition in the central region. 4Conclusion This scenario is qualitative only and is confined to the gravitational dynamics of the proto-solar-system, neglecting effects of rotation, magnetic fields, radiative pro- cesses, etc. The latter are known to be important during the formation of the parent disk (cf. Boss 1998), and also after the formation of the proto-solar-system in the Sun’s outer parts. However, the rotation and magnetic fields will themselves be af- fected by the gravitational interactions between the Sun’s mass elements and the planetary rings under the resonances on time scales of light-travel. Acknowledgment The author thanks R.J. Rutten for much text improvement. The author also thanks LOC and IIA for travel support and hospitality during the meeting. References Boss, A. P. 1998, In: Origins, C. E. Woodward, J. M. Shull, H. A. Thronson (eds.), ASP Conf. Ser., vol. 128, p. 315 Shu, F., Najita, J., Galli, D., Ostriker, E., Lizano, S. 1993, Protostars and Planets III, 3 Part IV Summaries of Presentations Published Elsewhere Cycle Prediction from Dynamo Theory A.R. Choudhuri Abstract Many previous efforts in sunspot cycle prediction were based on various empirical correlations, most of which have limited statistical significance because they were inferred from observations of very few cycles. Perhaps the most success- ful of the empirical methods is to use the strength of the polar field in the previous sunspot minimum as a precursor for the next cycle. As the polar field at the present time is weak, Schatten [2005, Geophys. Res. Lett., 32, L21106] and Svalsgaard et al. [2005, Geophys. Res. Lett., 32, L01104] have predicted that cycle 24 will be a weak cycle. The sunspot cycle is produced by a flux transport dynamo. One would like to make predictions of future cycles from dynamo models. By using the sunspot area data as the source of poloidal field, Dikpati and Gilman [2006, ApJ, 649, 498] pre- dicted that cycle 24 will be very strong. Choudhuri et al. [2007, Phys. Rev. Lett., 98, 131103] pointed out that the Babcock–Leighton mechanism for producing the poloidal field involves randomness so that the sunspot area data cannot be taken as a deterministic source term. By feeding the polar field values occurring at sunspot minima in their code to account for the Babcock–Leighton process, Choudhuri et al. [2007, Phys. Rev. Lett., 98, 131103] found that cycle 24 should be weak. Dynamo models have been found to show good correlation between the polar field at the minimum and the strength of the next sunspot cycle when the turbulent diffusiv- ity inside the convection zone is sufficiently high [Jiang et al. 2007, MNRAS, 381, 1527; Yeates et al. 2008, ApJ, 673, 544]. Goel and Choudhuri [2009, Res. Astron. Astrophys., 9, 115] analyze the historical faculae data to show that there is a good correlation between the hemispheric asymmetry of polar field at a minimum and the hemispheric asymmetry of the next cycle – again suggesting high diffusivity. A.R. Choudhuri (  ) Department of Physics, Indian Institute of Science, Bangalore, India S.S. Hasan and R.J. Rutten (eds.), Magnetic Coupling between the Interior and Atmosphere of the Sun, Astrophysics and Space Science Proceedings, DOI 10.1007/978-3-642-02859-5 66, c  Springer-Verlag Berlin Heidelberg 2010 498 Cycle Prediction from Dynamo Theory 499 References Choudhuri, A.R., Chatterjee, P., Jiang, J. 2007, Phys. Rev. Lett., 98, 131103 Dikpati, M., Gilman, P.A. 2006, ApJ, 649, 498 Goel, A., Choudhuri, A.R. 2009, Res. Astron. Astrophys., 9, 115 Jiang, J., Chatterjee, P., Choudhuri, A.R. 2007, MNRAS, 381, 1527 Schatten, K. 2005, Geophys. Res. Lett., 32, L21106 Svalgaard, L., Cliver, E.W., Kamide, Y. 2005, Geophys. Res. Lett., 32, L01104 Yeates, A.R., Nandy, D., Mackay, D.H. 2008, ApJ, 673, 544 Why Does the Torsional Oscillation Precede the Sunspot Cycle? P. Chatterjee, S. Chakraborty, and A.R. Choudhuri Abstract The Sun’s rotation shows a periodic variation with the sunspot cycle, called torsional oscillations, the nature of which inside the solar convection zone has been determined from helioseismology. Several authors developed theoretical models of torsional oscillations by assuming that they are driven by the Lorentz force of the Sun’s cyclically varying magnetic field. If this is true, then one would expect the torsional oscillations to follow the sunspot cycles. However, the torsional oscillations of a cycle begin a couple of years before the sunspots of that cycle ap- pear and at a latitude higher than where the first sunspots are subsequently seen. Our aim in this paper is to provide an explanation for this seemingly causality defying phenomenon. The sunspot cycle is produced by a flux transport dynamo (see Chatterjee, Nandy, Choudhuri 2004, A&A, 427, 1019). As the differential rotation is stronger at higher latitudes in the tachocline than at lower latitudes, the inclusion of solar-like rotation tends to produce a strong toroidal field at high latitudes rather than the latitudes where sunspots are seen. According to the Nandy and Choudhuri hypothesis (2002, Science, 296, 1671), the meridional circulation penetrates slightly below the bottom of the convection zone and the strong toroidal field produced at the high-latitude tachocline is pushed by this meridional circulation into stable layers below the con- vection zone, where magnetic buoyancy is suppressed and sunspots are not formed at high latitudes. Presumably, the torsional oscillation gets initiated in the lower footpoints of in- termittant vertical flux tubes inside the convection zone (Fig. 1 of Choudhuri 2003, Solar Phys., 215, 31), where the Lorentz force builds up due to the production of the azimuthal magnetic field. This perturbation then propagates upward along the vertical flux tubes at the Alfven speed. P. Chatterjee (  ) Department of Astronomy and Astrophysics, Tata Institute of Fundamental Research, Mumbai-400005, India S. Chakraborty Department of Theoretical Sciences, S. N. Bose Centre for Basic Sciences, Kolkata-700098, India A.R. Choudhuri Department of Physics, Indian Institute of Science, Bangalore-560012, India S.S. Hasan and R.J. Rutten (eds.), Magnetic Coupling between the Interior and Atmosphere of the Sun, Astrophysics and Space Science Proceedings, DOI 10.1007/978-3-642-02859-5 67, c  Springer-Verlag Berlin Heidelberg 2010 500 [...]... Does the Torsional Oscillation Precede the Sunspot Cycle? 501 The two completely novel aspects of our model are (1) the Nandy–Choudhuri hypothesis, which allows the formation of strong toroidal field in the high-latitude tachocline before the beginning of the sunspot cycle; and (2) the assumption that the perturbations propagate upward along flux tubes at the Alfv´ n speed With these e two assumptions... quiet -Sun regions This means that the intensity contrast of the network to the cell interiors is less in coronal holes than in the quiet Sun In the present study, the variation of intensity contrast of the network in the solar atmosphere has been examined Intensities of 14 EUV emission lines in a coronal hole and in neighboring quiet -Sun areas have been obtained from observations with the Solar and Heliospheric... the spectral position of the Fe I 630.15 nm line with the position of the line core of an average quiet Sun profile We evaluated the bisector of the line wing to investigate the flow pattern in the deep photosphere Because of the nonzero heliocentric angle (Â D 8ı ) of our data, not only the vertical but also the horizontal component of the Evershed flow contributes to the observed Dopplershifts For the. .. Nakariakov and Roberts (1995) when considering wave propagation only along the background magnetic field (2) The steady flows in the loops may be either antiparallel or parallel to the direction of the longitudinal phase propagation of the waves The antiparallel flows increase the wave period, while parallel ones decrease it These results are consistent with the earlier findings of Nakariakov and Roberts... region above 0.985 Rˇ and that the strengths of magnetic-field effects at the surface and in the deeper (r < 0:98 Rˇ ) layers are inversely related, that is, the stronger the surface magnetic field, the smaller the magnetic effects in the deeper layers, and vice versa We also found that the magnetic effects in the deeper layers are the strongest in the quiet regions, consistent with the fact that these... (SOHO)/Coronal Diagnostic Spectrometer (CDS) The formation temperatures of the observed lines vary from 0.08 to 1.1 MK and hence represent increasing heights in the solar atmosphere, from the upper chromosphere and transition region to the low corona The intensity contrast of the network with respect to the cell interior has been estimated for each line Differences in the quiet -Sun areas and the coronal... coronal hole have also been noted The network points and cell interiors were separated on the basis of the mean of the in˚ tensity distribution of the O V 629.73 A line It is found that the contrast in lower transition-region lines is higher for quiet Sun than for a coronal hole However, the contrasts become equal when one approaches the corona For both regions, the contrast reaches a maximum at about... triggered by coronal reconnection below the twisted flux tube of positive helicity It is the first time that such a consistency between the signature of the emerging flux observed in the photosphere (“tongues”) and flare ribbons in the chromosphere (‘J’ shape ribbons) is found At the periphery of the active region, the enhanced brightening of network is interpreted as the stationary EIT wave component discussed... Sun, Astrophysics and Space Science Proceedings, DOI 10. 1007/978-3-642-02859-5 84, c Springer-Verlag Berlin Heidelberg 2 010 525 Does Coronal Rotation Period Depend on the Sunspot Number? H.O Vats, S Chandra, and K.N Iyer Abstract The coronal rotation has been estimated using radio emissions at 2.8 GHz for the period 1947 to 2005 These measurements show a long term variability of the coronal rotation... Magnetic Coupling between the Interior and Atmosphere of the Sun, Astrophysics and Space Science Proceedings, DOI 10. 1007/978-3-642-02859-5 79, c Springer-Verlag Berlin Heidelberg 2 010 518 A Numerical Investigation of Unsheared Flux Cancelation 519 importance of considering the effects of submergence, as well as the full 3D configuration of the magnetic field and atmosphere, in determining the physical processes . up before the onset of nuclear reactions in the proto -Sun. Such resonances may expedite the onset of nuclear ignition in the proto -Sun and the redistribution and loss of the proto -Sun s angular. the Sun s outer parts. However, the rotation and magnetic fields will themselves be af- fected by the gravitational interactions between the Sun s mass elements and the planetary rings under the. below the bottom of the convection zone and the strong toroidal field produced at the high-latitude tachocline is pushed by this meridional circulation into stable layers below the con- vection zone,