Related papers: Possible solar cycle variations in the convection …
Large-scale plasma flows in the Sun's convection zone likely play a major role in solar dynamics on decadal timescales. In particular, quantifying meridional motions is a critical ingredient for understanding the solar cycle and the…
Using the Solar Optical Observing Network (SOON) sunspot-group data for the period 1985-2010, the variations in the annual mean equatorial-rotation rates of the sunspot groups are determined and compared with the known variations in the…
Variations of frequency separations of low-degree p-modes are studied over the solar activity cycle. The separations studied are obtained from the frequencies of low-degree p-modes of the Global Oscillation Network Group (GONG). 10.7 cm…
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…
We investigate the parameters of global solar p-mode oscillations, namely damping width $\Gamma$, amplitude $A$, mean squared velocity $\langle v^2\rangle$, energy $E$, and energy supply rate $\mathrm{d}E/\mathrm{d} t$, derived from two…
We use subsurface-flow velocity maps inferred by time--distance helioseismology from Doppler measurements with the Helioseismic and Magnetic Imager (HMI) of the Solar Dynamics Observatory (SDO) to investigate variations of large-scale…
We investigate the behavior of the intermediate-degree mode frequencies of the sun during the current extended minimum phase to explore the time-varying conditions in the solar interior. Using contemporaneous helioseismic data from GONG and…
The latitudinal sound-speed structure of the Sun's convection zone gives insight into the physical processes occurring there, specifically the cellular convection and possibly the presence of magnetic fields. Using helioseismic data from…
We study temporal variations in the amplitudes and widths of high-degree acoustic modes in the quiet and active Sun by applying ring-diagram technique to the GONG+ and MDI Dopplergrams during the declining phase of cycle 23. The increase in…
We review recent insights into the dynamics of the solar convection zone obtained from global numerical simulations, focusing on two recent developments in particular. The first is quasi-cyclic magnetic activity in a long-duration dynamo…
Solar activity is studied using a cluster analysis of the time-fluctuations of the sunspot number. It is shown that in an Historic period the high activity components of the solar cycles exhibit strong clustering, whereas in a Modern period…
The evolution of the solar activity comprises, apart from the well-known 11-year cycle, various temporal scales ranging from months up to the secondary cycles known as mid-term oscillations. Its nature deserves a physical explanation. In…
We examine the evolution of the zonal flow pattern in the upper solar convection zone during the current extended solar minimum, and compare it with that during the previous minimum. The results suggest that a configuration matching that at…
We investigate the variation in the mode parameters obtained from time series of length 9, 36, 72 and 108 days to understand the changes occurring on different time-scales. The regression analysis between frequency shifts and activity…
Meridional flow is thought to play a very important role in the dynamics of the solar convection zone; however, because of its relatively small amplitude, precisely measuring it poses a significant challenge. Here we present a complete…
We use helioseismic data from ground and space-based instruments to analyze how solar rotation has changed since the beginning of solar Cycle 23 with emphasis on studying the differences between Cycles 23 and 24. We find that the nature of…
It has been shown over and over again that the parameters of solar p modes vary through the solar activity cycle: frequencies, amplitudes, lifetimes, energies. However, so far, the rates at which energy is supplied to the p modes have not…
Differences between observed and theoretical eigenfrequencies of the Sun have characteristics which identify them as arising predominantly from properties of the oscillations in the vicinity of the solar surface: in the super-adiabatic,…
The availability of continuous helioseismic data for two consecutive solar minima has provided a unique opportunity to study the changes in the solar interior that might have led to this unusual minimum. We present preliminary analysis of…
We study the variation of the frequency splitting coefficients describing the solar asphericity in both GONG and MDI data, and use these data to investigate temporal sound-speed variations as a function of both depth and latitude during the…