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J. T. Hoeksema - One of the best experts on this subject based on the ideXlab platform.

  • Solar Magnetic Field reversals and the role of dynamo families
    The Astrophysical Journal, 2012
    Co-Authors: Marc L. Derosa, Allan Sacha Brun, J. T. Hoeksema
    Abstract:

    The variable Magnetic Field of the Solar photosphere exhibits periodic reversals as a result of dynamo activity occurring within the Solar interior. We decompose the surface Field as observed by both the Wilcox Solar Observatory and the Michelson Doppler Imager into its harmonic constituents, and present the time evolution of the mode coefficients for the past three sunspot cycles. The interplay between the various modes is then interpreted from the perspective of general dynamo theory, where the coupling between the primary and secondary families of modes is found to correlate with large-scale polarity reversals for many examples of cyclic dynamos. Mean-Field dynamos based on the Solar parameter regime are then used to explore how such couplings may result in the various long-term trends in the surface Magnetic Field observed to occur in the Solar case.

  • On the role of asymmetries in the reversal of the Solar Magnetic Field
    Proceedings of the International Astronomical Union, 2012
    Co-Authors: Allan Sacha Brun, Marc L. Derosa, J. T. Hoeksema
    Abstract:

    AbstractWe study how the Solar Magnetic Field evolves from antisymmetric (dipolar) to symmetric (quadrupolar) state during the course of its 11-yr cycle. We show that based on equatorial symmetries of the induction equation, flux transport Solar mean Field dynamo models excite mostly the antisymmetric (dipolar) family whereas a decomposition of the Solar Magnetic Field data reveals that both families should be excited to similar amplitude levels. We propose an alternative Solar dynamo solution based on North-South asymmetry of the meridional circulation to better reconcile models and observations.

  • The Evolution of the Solar Magnetic Field
    Proceedings of the International Astronomical Union, 2012
    Co-Authors: J. T. Hoeksema
    Abstract:

    AbstractThe almost stately evolution of the global heliospheric Magnetic Field pattern during most of the Solar cycle belies the intense dynamic interplay of photospheric and coronal flux concentrations on scales both large and small. The statistical characteristics of emerging bipoles and active regions lead to development of systematic Magnetic patterns. Diffusion and flows impel features to interact constructively and destructively, and on longer time scales they may help drive the creation of new flux. Peculiar properties of the components in each Solar cycle determine the specific details and provide additional clues about their sources. The interactions of complex developing features with the existing global Magnetic environment drive impulsive events on all scales. Predominantly new-polarity surges originating in active regions at low latitudes can reach the poles in a year or two. Coronal holes and polar caps composed of short-lived, small-scale Magnetic elements can persist for months and years. Advanced models coupled with comprehensive measurements of the visible Solar surface, as well as the interior, corona, and heliosphere promise to revolutionize our understanding of the hierarchy we call the Solar Magnetic Field.

  • Long-term variability of Solar Magnetic Fields
    Advances in Space Research, 2002
    Co-Authors: J. T. Hoeksema, P. H. Scherrer
    Abstract:

    Abstract The Solar Magnetic Field varies on all time scales. Recent analysis of 600 million year-old Australian varves shows terrestrial evidence for not only the familiar 22-year Magnetic cycle, but variations with periods of 300–400 years as well. The Maunder minimum is but one of several long intervals showing atypical levels of Solar activity. Recently a 151-day periodicity in flare activity has been found. Active regions, sunspots, ephemeral regions, and flares cover a broad range of shorter time scale variations in the Solar Magnetic Field. Long-term variations can be interpreted in at least two ways. One outlook regards the large-scale and long-term variations of the photospheric Field as more-or-less direct guides to the organization of the Solar Field as it evolves through a Solar cycle. The slowly varying Field reveals the fundamental interior structure of the Sun. An alternative view interprets the surface manifestation of the Magnetic Field primarily as the result of the convective motions in the Solar atmosphere. The evolving distribution of photospheric flux depends upon the locations of emerging flux and the subsequent motions and interactions of the Fields in the moving plasma. Information about the interior Field comes largely from analysis of emerging flux. We discuss interpretation of the phenomenology of the long-term variability in the context of these contrasting views.

K Hakamada - One of the best experts on this subject based on the ideXlab platform.

  • probe of the Solar Magnetic Field using the cosmic ray shadow of the sun
    Physical Review Letters, 2013
    Co-Authors: M. Amenomori, X. J. Bi, Donghong Chen, T. L. Chen, W. Y. Chen, L. K. Ding, C Feng, Zhaoyang Feng, Z Y Feng, K Hakamada
    Abstract:

    We report on a clear Solar-cycle variation of the Sun's shadow in the 10 TeV cosmic-ray flux observed by the Tibet air shower array during a full Solar cycle from 1996 to 2009. In order to clarify the physical implications of the observed Solar cycle variation, we develop numerical simulations of the Sun's shadow, using the potential Field source surface model and the current sheet source surface (CSSS) model for the coronal Magnetic Field. We find that the intensity deficit in the simulated Sun's shadow is very sensitive to the coronal Magnetic Field structure, and the observed variation of the Sun's shadow is better reproduced by the CSSS model. This is the first successful attempt to evaluate the coronal Magnetic Field models by using the Sun's shadow observed in the TeV cosmic-ray flux.

M. Amenomori - One of the best experts on this subject based on the ideXlab platform.

  • Solar Magnetic Field strength and the ``Sun's Shadow''
    Proceedings of 35th International Cosmic Ray Conference — PoS(ICRC2017), 2017
    Co-Authors: Yoshiaki Nakamura, M. Amenomori, X. J. Bi, Donghong Chen, T. L. Chen, W. Y. Chen, Danzengluobu, L. K. Ding, C. F. Feng
    Abstract:

    The angular displacement of the center of the observed Sun's shadow from the center of the optical Solar disc tells us the information of average Solar Magnetic Field strength in the space between the Sun and the Earth. We analyze the displacement of the Sun's shadow observed in 5 ~ 240 TeV cosmic-ray intensity with the Tibet-III air shower array during 10 years between 2000 and 2009, and compare with the MC simulations based on the coronal Magnetic Field model and Parker's spiral interplanetary Magnetic Field model. We find that the observed North-South displacement is significantly larger than the prediction of simulations. This result uniquely suggests the underestimation of the average Field strength between the Sun and the Earth in our model. In this work, we will report the actual Solar Magnetic Field strength evaluated from the observed Sun's shadow.

  • probe of the Solar Magnetic Field using the cosmic ray shadow of the sun
    Physical Review Letters, 2013
    Co-Authors: M. Amenomori, X. J. Bi, Donghong Chen, T. L. Chen, W. Y. Chen, L. K. Ding, C Feng, Zhaoyang Feng, Z Y Feng, K Hakamada
    Abstract:

    We report on a clear Solar-cycle variation of the Sun's shadow in the 10 TeV cosmic-ray flux observed by the Tibet air shower array during a full Solar cycle from 1996 to 2009. In order to clarify the physical implications of the observed Solar cycle variation, we develop numerical simulations of the Sun's shadow, using the potential Field source surface model and the current sheet source surface (CSSS) model for the coronal Magnetic Field. We find that the intensity deficit in the simulated Sun's shadow is very sensitive to the coronal Magnetic Field structure, and the observed variation of the Sun's shadow is better reproduced by the CSSS model. This is the first successful attempt to evaluate the coronal Magnetic Field models by using the Sun's shadow observed in the TeV cosmic-ray flux.

T. L. Chen - One of the best experts on this subject based on the ideXlab platform.

  • Solar Magnetic Field strength and the ``Sun's Shadow''
    Proceedings of 35th International Cosmic Ray Conference — PoS(ICRC2017), 2017
    Co-Authors: Yoshiaki Nakamura, M. Amenomori, X. J. Bi, Donghong Chen, T. L. Chen, W. Y. Chen, Danzengluobu, L. K. Ding, C. F. Feng
    Abstract:

    The angular displacement of the center of the observed Sun's shadow from the center of the optical Solar disc tells us the information of average Solar Magnetic Field strength in the space between the Sun and the Earth. We analyze the displacement of the Sun's shadow observed in 5 ~ 240 TeV cosmic-ray intensity with the Tibet-III air shower array during 10 years between 2000 and 2009, and compare with the MC simulations based on the coronal Magnetic Field model and Parker's spiral interplanetary Magnetic Field model. We find that the observed North-South displacement is significantly larger than the prediction of simulations. This result uniquely suggests the underestimation of the average Field strength between the Sun and the Earth in our model. In this work, we will report the actual Solar Magnetic Field strength evaluated from the observed Sun's shadow.

  • probe of the Solar Magnetic Field using the cosmic ray shadow of the sun
    Physical Review Letters, 2013
    Co-Authors: M. Amenomori, X. J. Bi, Donghong Chen, T. L. Chen, W. Y. Chen, L. K. Ding, C Feng, Zhaoyang Feng, Z Y Feng, K Hakamada
    Abstract:

    We report on a clear Solar-cycle variation of the Sun's shadow in the 10 TeV cosmic-ray flux observed by the Tibet air shower array during a full Solar cycle from 1996 to 2009. In order to clarify the physical implications of the observed Solar cycle variation, we develop numerical simulations of the Sun's shadow, using the potential Field source surface model and the current sheet source surface (CSSS) model for the coronal Magnetic Field. We find that the intensity deficit in the simulated Sun's shadow is very sensitive to the coronal Magnetic Field structure, and the observed variation of the Sun's shadow is better reproduced by the CSSS model. This is the first successful attempt to evaluate the coronal Magnetic Field models by using the Sun's shadow observed in the TeV cosmic-ray flux.

L. K. Ding - One of the best experts on this subject based on the ideXlab platform.

  • Solar Magnetic Field strength and the ``Sun's Shadow''
    Proceedings of 35th International Cosmic Ray Conference — PoS(ICRC2017), 2017
    Co-Authors: Yoshiaki Nakamura, M. Amenomori, X. J. Bi, Donghong Chen, T. L. Chen, W. Y. Chen, Danzengluobu, L. K. Ding, C. F. Feng
    Abstract:

    The angular displacement of the center of the observed Sun's shadow from the center of the optical Solar disc tells us the information of average Solar Magnetic Field strength in the space between the Sun and the Earth. We analyze the displacement of the Sun's shadow observed in 5 ~ 240 TeV cosmic-ray intensity with the Tibet-III air shower array during 10 years between 2000 and 2009, and compare with the MC simulations based on the coronal Magnetic Field model and Parker's spiral interplanetary Magnetic Field model. We find that the observed North-South displacement is significantly larger than the prediction of simulations. This result uniquely suggests the underestimation of the average Field strength between the Sun and the Earth in our model. In this work, we will report the actual Solar Magnetic Field strength evaluated from the observed Sun's shadow.

  • probe of the Solar Magnetic Field using the cosmic ray shadow of the sun
    Physical Review Letters, 2013
    Co-Authors: M. Amenomori, X. J. Bi, Donghong Chen, T. L. Chen, W. Y. Chen, L. K. Ding, C Feng, Zhaoyang Feng, Z Y Feng, K Hakamada
    Abstract:

    We report on a clear Solar-cycle variation of the Sun's shadow in the 10 TeV cosmic-ray flux observed by the Tibet air shower array during a full Solar cycle from 1996 to 2009. In order to clarify the physical implications of the observed Solar cycle variation, we develop numerical simulations of the Sun's shadow, using the potential Field source surface model and the current sheet source surface (CSSS) model for the coronal Magnetic Field. We find that the intensity deficit in the simulated Sun's shadow is very sensitive to the coronal Magnetic Field structure, and the observed variation of the Sun's shadow is better reproduced by the CSSS model. This is the first successful attempt to evaluate the coronal Magnetic Field models by using the Sun's shadow observed in the TeV cosmic-ray flux.