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We examine the frequency shifts in low-degree helioseismic modes from the Birmingham Solar-Oscillations Network (BiSON) covering the period from 1985 - 2016, and compare them with a number of global activity proxies well as a…

Solar and Stellar Astrophysics · Physics 2017-07-26 R. Howe , G. R. Davies , W. J. Chaplin , Y. Elsworth , S. Basu , S. J. Hale , W. H. Ball , R. W. Komm

Using data from the Global Oscillation Network Group (GONG) covering the period from 1995 to 1998, we study the change with solar activity in solar f-mode frequencies. The results are compared with similar changes detected from the…

Astrophysics · Physics 2015-06-24 H. M. Antia , Sarbani Basu , J. Pintar , B. Pohl

We have examined polar magnetic fields for the last three solar cycles, {$\it{viz.}$}, cycles 21, 22 and 23 using NSO Kitt Peak synoptic magnetograms. In addition, we have used SoHO/MDI magnetograms to derive the polar fields during cycle…

Space Physics · Physics 2015-05-20 P. Janardhan , Kumar Bisoi Susanta , S. Gosain

In the declining phase of the solar cycle, when the new-polarity fields of the solar poles are strengthened by the transport of same-signed magnetic flux from lower latitudes, the polar coronal holes expand and form non-axisymmetric…

Solar and Stellar Astrophysics · Physics 2015-06-23 Kalevi Mursula , Renata Lukianova , Lauri Holappa

We have used solar oscillation frequencies and frequency splittings obtained over solar cycles 23, 24 and the rising phase of solar cycle 25 to investigate whether the tachocline properties (jump i.e., the change in the rotation rate across…

Solar and Stellar Astrophysics · Physics 2024-10-04 Sarbani Basu , Wesley Antônio Machado Andrade de Aguiar , Sylvain G. Korzennik

Detailed models of the solar cycle require information about the starting time and rise time as well as the shape and amplitude of the cycle. However, none of these models includes a discussion of the variations in the length of the cycle,…

Astrophysics · Physics 2007-05-23 Michael L. Rogers , Mercedes T. Richards , Donald St. P. Richards

Solar cycle is modeled as a forced and damped harmonic oscillator and the amplitudes, frequencies, phases and decay factors of such a harmonic oscillator are estimated by non-linear fitting the equation of sinusoidal and transient parts to…

Solar and Stellar Astrophysics · Physics 2022-04-12 K M Hiremath

To better understand the influence of the activity cycle on the solar atmosphere, we report the time variation of the radius observed at 37 GHz ($\lambda$=8.1 mm) obtained by the Mets\"ahovi Radio Observatory (MRO) through Solar Cycles 22…

Solar and Stellar Astrophysics · Physics 2019-12-17 Caius L. Selhorst , Juha Kallunki , C. G. Giménez de Castro , Adriana Valio , Joaquim E. R. Costa

We study solar modulation of galactic cosmic rays (GCRs) during the deep solar minimum, including the declining phase, of solar cycle 23 and compare the results of this unusual period with the results obtained during similar phases of the…

Solar and Stellar Astrophysics · Physics 2013-12-03 O. P. M. Aslam , Badruddin

The daily sunspot numbers of the whole disk as well as the northern and southern hemispheres from January 1, 1945 to December 31, 2010 are used to investigate the temporal variation of the rotational cycle length through the continuous…

Solar and Stellar Astrophysics · Physics 2015-06-03 J. -L. Xie , X. -J. Shi , J. -C. Xu

In the previous study (Hiremath 2006a), the solar cycle is modeled as a forced and damped harmonic oscillator and from all the 22 cycles (1755-1996), long-term amplitudes, frequencies, phases and decay factor are obtained. Using these…

Astrophysics · Physics 2007-05-23 K. M. Hiremath

We study durations of main and recovery phases of magnetic storms induced by different types of large-scale solar-wind streams (Sheath, magnetic cloud (MC), Ejecta and CIR) on the basis of OMNI data base during 1976-2000. Durations of both…

Space Physics · Physics 2014-11-26 Yu. I. Yermolaev , I. G. Lodkina , N. S. Nikolaeva , M. Yu. Yermolaev

We have studied solar activity and space weather conditions during multiple planetary conjunction periods ( MPC) as observed from Earth during the years 1850-2000 AD. Significant decreases in sunspot activity and solar 10.7 cm radio flux…

General Physics · Physics 2020-09-14 N. G. Nisha , T. E. Girish

The variability of the spectral solar irradiance (SSI) over the course of the 11-year solar cycle is one of the manifestations of solar magnetic activity. There is a strong evidence that the SSI variability has an effect on the Earth's…

Solar and Stellar Astrophysics · Physics 2020-04-29 Anna V. Shapiro , Alexander I. Shapiro , Laurent Gizon , Natalie A. Krivova , Sami K. Solanki

We study the differences in the heavy ion composition of solar energetic particle (SEP) events between solar cycles 23 and 24. We have surveyed the SOHO/ERNE heavy ion data from the beginning of solar cycle 23 until the end of June 2015,…

Solar and Stellar Astrophysics · Physics 2016-04-27 O. Raukunen , E. Valtonen , R. Vainio

The diagram of indices of coronal and chromospheric activity allowed us to reveal stars where solar-type activity appears and regular cycles are forming. Using new consideration of a relation between coronal activity and the rotation rate,…

Solar and Stellar Astrophysics · Physics 2015-08-06 M. M. Katsova , N. I. Bondar' , M. A. Livshits

Using data collected by the Indian Mars Orbiter Mission in October 2021, we investigated coronal regions of the Sun by analyzing the Doppler spectral width of radio signals to estimate solar wind velocity. A simplified equation is…

Solar and Stellar Astrophysics · Physics 2025-04-02 Keshav Aggarwal , R. K. Choudhary , Abhirup Datta , Roopa M. V. , Bijoy K. Dai

Inter-cycle variations in the series of 11-year solar activity cycles have a significant impact on both the space environment and climate. Whether solar cycle variability is dominated by deterministic chaos or stochastic perturbations…

Solar and Stellar Astrophysics · Physics 2025-05-12 Zi-Fan Wang , Jie Jiang , Jing-Xiu Wang

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

Our basic theoretical understanding of the sources of cosmic rays and their propagation through the interstellar medium is hindered by the Sun, that through the solar wind affects the observed cosmic-ray spectra. This effect is known as…

Solar and Stellar Astrophysics · Physics 2022-10-12 Ilias Cholis , Ian McKinnon