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The focusing of the radiation generated by a polarization current with a superluminally rotating distribution pattern is of a higher order in the plane of rotation than in other directions. Consequently, our previously published asymptotic…

Astrophysics · Physics 2009-11-13 Houshang Ardavan , Arzhang Ardavan , John Singleton , Joseph Fasel , Andrea Schmidt

We use images of high spatial and temporal resolution, obtained using both ground- and space-based instrumentation, to investigate the role magnetic field inclination angles play in the propagation characteristics of running penumbral waves…

Solar and Stellar Astrophysics · Physics 2015-06-17 D. B. Jess , V. E. Reznikova , T. Van Doorsselaere , P. H. Keys , D. H. Mackay

As each solar cycle progresses, remnant magnetic flux from active regions (ARs) migrates poleward to cancel the old-cycle polar field. We describe this polarity reversal process during Cycle 24 using four years (2010.33--2014.33) of…

Solar and Stellar Astrophysics · Physics 2015-06-23 Xudong Sun , J. Todd Hoeksema , Yang Liu , Junwei Zhao

The vector representation of sunspots is used to study the nonaxisymmetric features of the solar activity distribution (sunspot data from Greenwich - USAF/NOAA, 1874 - 2016).The vector of the longitudinal asymmetry is defined for each…

Solar and Stellar Astrophysics · Physics 2019-12-03 Elena Vernova , Marta Tyasto , Dmitrii Baranov , Olga Danilova

Solar irradiance variations over solar rotational time-scales are largely determined by the passage of magnetic structures across the visible solar disk. Variations on solar cycle time scales are thought to be similarly due to changes in…

Solar and Stellar Astrophysics · Physics 2015-08-19 Courtney Peck , Mark Rast

Solar inter-network magnetic field is the weakest component of solar magnetism, but contributes most of the solar surface magnetic flux. The study on its origin has been constrained by the inadequate tempo-spatial resolution and sensitivity…

Solar and Stellar Astrophysics · Physics 2015-05-26 Chunlan Jin , Jingxiu Wang

Solar subsurface zonal and meridional-flow profiles during the rising phase of solar cycle 24 are studied using time-distance helioseismology technique. The faster zonal bands in the torsional-oscillation pattern show strong hemispheric…

Solar and Stellar Astrophysics · Physics 2015-06-19 Junwei Zhao , A. G. Kosovichev , R. S. Bogart

Multiscale topological complexity of solar magnetic field is among the primary factors controlling energy release in the corona, including associated processes in the photospheric and chromospheric boundaries. We present a new approach for…

Solar and Stellar Astrophysics · Physics 2015-06-03 Vadim M. Uritsky , Joseph M. Davila

The hemispheric asymmetry of the sunspot cycle is a real feature of the Sun. However, its origin is still not well understood. Here we perform nonlinear time series analysis of the sunspot area (and number) asymmetry to explore its…

Solar and Stellar Astrophysics · Physics 2022-01-19 Ratul Das , Aparup Ghosh , Bidya Binay Karak

Sunspots and the plethora of other phenomena occuring in the course of the 11-year cycle of solar activity are a consequence of the emergence of magnetic flux at the solar surface. The observed orientations of bipolar sunspot groups imply…

Solar and Stellar Astrophysics · Physics 2015-06-24 Robert Cameron , Manfred Schüssler

The duration of activity growths in solar cycles is on average shorter than the duration of its declines. This asymmetry can result from fluctuations in dynamo parameters. A solar dynamo model with fluctuations in the $\alpha$-effect shows…

Solar and Stellar Astrophysics · Physics 2018-11-07 Leonid Kitchatinov , Alexander Nepomnyashchikh

The distribution of magnetic fields of positive and negative polarities over the surface of the Sun was studied on the basis of synoptic maps presented by the NSO/Kitt Peak (1978-2016). To emphasize the contribution of weak fields the…

Solar and Stellar Astrophysics · Physics 2023-06-07 Elena S. Vernova , Marta I. Tyasto , Dmitrii G. Baranov

The solar surface magnetic field is fundamental for modeling the coronal magnetic field, studying the solar dynamo, and predicting solar cycle strength. We perform a continuous simulation of the surface magnetic field from 2010 to 2024,…

Solar and Stellar Astrophysics · Physics 2025-06-03 Ruihui Wang , Jie Jiang , Yukun Luo

The so-called solar cycle is generally characterized by the quasi-periodic oscillatory evolution of the photospheric spots number. This quasi-periodic pattern has always been an intriguing question. Several physical models were proposed to…

Solar and Stellar Astrophysics · Physics 2015-05-14 Alexis Klutsch , Rubens Freire Ferrero

We have examined the global structure of the solar magnetic field using data from the FeI spectral line at {\lambda}5250.2{\AA} obtained at the 150-foot tower telescope at the Mt. Wilson Observatory (MWO). For each point on the solar…

Solar and Stellar Astrophysics · Physics 2015-06-15 Roger K. Ulrich , Tham Tran

Most models of solar eruptions assume that coronal field lines are anchored in the dense photosphere and thus the photospheric magnetic fields would not have rapid, irreversible changes associated with eruptions resulted from the coronal…

Solar and Stellar Astrophysics · Physics 2015-05-19 Haimin Wang , Chang Liu

The velocity field in the lower solar atmosphere undergoes strong interactions with magnetic fields. Many authors have pointed out that power is reduced by a factor between two and three within magnetic regions, depending on frequency,…

Solar and Stellar Astrophysics · Physics 2015-06-12 F. Giannattasio , M. Stangalini , D. Del Moro , F. Berrilli

During a solar magnetic field reversal the magnetic dipole moment does not vanish, but migrates between poles, in contradiction to the predictions of mean-field dynamo theory. We try to explain this as a consequence of magnetic…

Solar and Stellar Astrophysics · Physics 2015-06-12 David Moss , Leonid L. Kitchatinov , Dmitri Sokoloff

The results of determinations of the azimuthal and meridional velocities by time-distance helioseismology from Helioseismic and Magnetic Imager (HMI) onboard Solar Dynamics Observatory (SDO) from May 2010 to September 2020 at latitudes from…

Solar and Stellar Astrophysics · Physics 2021-02-26 Alexander V. Getling , Alexander G. Kosovichev , Junwei Zhao

Recent studies have established that peaks in solar oscillation power spectra are not Lorentzian in shape, but have a distinct asymmetry. Fitting a symmetric Lorentzian profile to the peaks therefore produces a shift in frequency of the…