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We report observations of a steady 20 year decline of solar photospheric fields at latitudes $\geq$45${^{o}}$ starting from $\sim$1995. This prolonged and continuing decline, combined with the fact that Cycle 24 is already past its peak,…

Solar and Stellar Astrophysics · Physics 2015-09-16 P. Janardhan , Susanta Kumar Bisoi , S. Ananthakrishnan , M. Tokumaru , K. Fujiki , L. Jose , R. Sridharan

We present a study of the solar wind over different periods of the solar cycle, specifically focussing on the minimum between solar cycles 24 and 25, and the active, ascending phase of solar cycle 25. With the use of interplanetary…

Solar and Stellar Astrophysics · Physics 2025-06-18 A. Waszewski , J. S. Morgan , R. Ekers , M. Johnston-Hollitt , M. C. M. Cheung , N. D. R. Bhat , R. Chhetri , S. C. Fu

We study the evolution of the observed photospheric magnetic field and the modeled global coronal magnetic field during the past 3 1/2 solar activity cycles observed since the mid-1970s. We use synoptic magnetograms and extrapolated…

Solar and Stellar Astrophysics · Physics 2015-06-15 G. J. D. Petrie

Using both wavelet and Fourier analysis, a study has been undertaken of the changes in the quasi-periodic variations in solar photospheric fields in the build-up to one of the deepest solar minima experienced in the past 100 years. This…

Solar and Stellar Astrophysics · Physics 2015-06-15 Susanta Kumar Bisoi , P. Janardhan , D. Chakrabarty , S. Ananthakrishnan , Ankur Divekar

This paper presents the analysis of 3D evolution of solar wind density turbulence and speed at various levels of solar activity between solar cycles 22 and 24. The solar wind data has been obtained from interplanetary scintillation (IPS)…

Solar and Stellar Astrophysics · Physics 2015-06-04 P. K. Manoharan

In this paper, I review the results of 3-D evolution of the inner heliosphere over the solar cycle #23, based on observations of interplanetary scintillation (IPS) made at 327 MHz using the Ooty Radio Telescope. The large-scale features of…

Solar and Stellar Astrophysics · Physics 2011-04-04 P. K. Manoharan

The work is devoted to the study of periodic structures in the magnetic field of the photosphere. The polarity of the Sun's magnetic fields shows cyclicity with periods of 1-3 years, which is possibly due to quasi-biennial variations that…

Solar and Stellar Astrophysics · Physics 2025-07-08 Elena Vernova , Marta Tyasto , Dmitrii Baranov

The evolution of the photospheric magnetic field during the declining phase and minimum of Cycle 23 and the recent rise of Cycle 24 are compared with the behavior during previous cycles. We used longitudinal full-disk magnetograms from the…

Solar and Stellar Astrophysics · Physics 2012-08-28 Gordon Petrie

A new model has been proposed for magnetic field determination at different distances from the Sun during different solar cycle phases. The model depends on the observed large-scale non-polar photospheric magnetic fields and that measured…

Solar and Stellar Astrophysics · Physics 2018-08-08 Irina A. Bilenko

We present an analysis of interplanetary scintillation (IPS) observations conducted with the Arecibo 305-m radio telescope during the minimum phase at the end of solar cycle 24 and the onset of solar cycle 25. These observations span a…

Solar and Stellar Astrophysics · Physics 2025-02-25 P. K. Manoharan , C. J. Salter

Extensive interplanetary scintillation (IPS) observations at 327 MHz obtained between 1983 and 2009 clearly show a steady and significant drop in the turbulence levels in the entire inner heliosphere starting from around ~1995. We believe…

Solar and Stellar Astrophysics · Physics 2011-10-05 P. Janardhan , Susanta Kumar Bisoi , S. Ananthakrishnan , M. Tokumaru , K. Fujiki

Thirty-four years of WSO (Wilcox Solar Observatory) and thirteen years of SOHO/MDI (Michelson Doppler Imager on the Solar and Heliospheric Observatory) magnetograms have been studied to measure the east-west inclination angle, indicating…

Solar and Stellar Astrophysics · Physics 2010-03-23 Leyan Lo , Todd Hoeksema , Phil Scherrer

Aims: To investigate solar polar fields during cycle 24, using measurements of solar magnetic fields in the latitude range 55 - 90 degree and 78 - 90 degree, to report a prolonged and unusual hemispheric asymmetry in the polar field…

Solar and Stellar Astrophysics · Physics 2018-10-24 P. Janardhan , K. Fujiki , M. Ingale , Susanta Kumar Bisoi , Diptiranjan Rout

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

We examine the temporal changes in both solar polar magnetic field (PMF) at latitudes $\ge$ $45^{\circ}$ and heliospheric magnetic field (HMF) at 1 AU during solar cycles 21--24 with emphasis on the recent activity changes after July 2015,…

Solar and Stellar Astrophysics · Physics 2020-08-05 Susanta Kumar Bisoi , P. Janardhan , S. Ananthakrishnan

Variations of the weak magnetic fields of the photosphere with periods of the order of the solar magnetic cycle were investigated. Synoptic maps of the photospheric magnetic field produced by NSO Kitt Peak for the period from 1978 to 2016…

Solar and Stellar Astrophysics · Physics 2023-07-18 E. S. Vernova , M. I. Tyasto , D. G. Baranov

The present study examines the response of the terrestrial magnetosphere to the long-term steady declining trends observed in solar magnetic fields and solar wind micro-turbulence levels since mid-1990's that has been continuing beyond the…

Solar and Stellar Astrophysics · Physics 2019-08-08 M. Ingale , P. Janardhan , S. K. Bisoi

The last solar minimum was, by recent standards, unusually deep and long. We are now close to the maximum of the subsequent solar cycle, which is relatively weak. In this article we make comparisons between different global (unresolved)…

Solar and Stellar Astrophysics · Physics 2015-07-13 A. -M. Broomhall , V. M. Nakariakov

Photospheric magnetic fields are studied using synoptic maps from 1976 to 2003 produced at the National Solar Observatory, Kitt Peak (NSO/KP). Synoptic maps were averaged over the time interval of nearly three solar cycles (Solar Cycles…

Solar and Stellar Astrophysics · Physics 2016-04-08 E. S. Vernova , M. I. Tyasto , D. G. Baranov

Polarity imbalance of the photospheric magnetic field was studied using synoptic maps of NSO Kitt Peak (1976-2016). Imbalance of positive and negative fluxes was considered for the fields with strength B>50 G in the sunspot zone (5 deg - 40…

Solar and Stellar Astrophysics · Physics 2018-12-12 E. S. Vernova , M. I. Tyasto , D. G. Baranov , O. A. Danilova
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