84 citations · 304 across the 16 of their papers we have counts for
16 papers
Stellar Activity Cycles
Sandra V. Jeffers, Rene Kiefer, Travis S. Metcalfe
The magnetic field of the Sun is generated by internal dynamo process with a cyclic period of 11 years or a 22 year magnetic cycle. The signatures of the Sun's magnetic cycle are o…
Cycle dependency of a quasi-biennial variability in the solar interior
T. Mehta, K. Jain, S. C. Tripathy +3
We investigated the solar cycle dependency on the presence and periodicity of the Quasi-Biennial Oscillation (QBO). Using helioseismic techniques, we used solar oscillation frequen…
A Multi-Instrument Investigation of the Frequency Stability of Oscillations Above the Acoustic Cut-Off Frequency with Solar Activity
K. Kosak, R. Kiefer, A. M. Broomhall
Below the acoustic cut-off frequency, oscillations are trapped within the solar interior and become resonant. However, signatures of oscillations persist above the acoustic cut-off…
They Do Change After All: 25 Years of GONG Data Reveal Variation of p-Mode Energy Supply Rates
René Kiefer, Anne-Marie Broomhall
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…
Empirical Relations for the Sensitivities of Solar-like Oscillations to Magnetic Perturbations
René Kiefer, Anne-Marie Broomhall
Oscillation mode frequencies of stars are typically treated as static for a given stellar model. However, in reality they can be perturbed by time varying sources such as magnetic…
Age dating of an early Milky Way merger via asteroseismology of the naked-eye star Indi
William J. Chaplin, Aldo M. Serenelli, Andrea Miglio +81
Over the course of its history, the Milky Way has ingested multiple smaller satellite galaxies. While these accreted stellar populations can be forensically identified as kinematic…
Signatures of magnetic activity: On the relation between stellar properties and p-mode frequency variations
A. R. G. Santos, T. L. Campante, W. J. Chaplin +12
In the Sun, the properties of acoustic modes are sensitive to changes in the magnetic activity. In particular, mode frequencies are observed to increase with increasing activity le…
Seismic Signatures of Stellar Magnetic Activity -- What Can We Expect from TESS?
René Kiefer, Anne-Marie Broomhall, Warrick H. Ball
Asteroseismic methods offer a means to investigate stellar activity and activity cycles as well as to identify those properties of stars which are crucial for the operation of stel…
GONG p-mode parameters through two solar cycles
René Kiefer, Rudi Komm, Frank Hill +2
We investigate the parameters of global solar p-mode oscillations, namely damping width , amplitude , mean squared velocity , energy , and energy suppl…
Seismic signatures of magnetic activity in solar-type stars observed by Kepler
A. R. G. Santos, T. L. Campante, W. J. Chaplin +8
The properties of the acoustic modes are sensitive to magnetic activity. The unprecedented long-term Kepler photometry, thus, allows stellar magnetic cycles to be studied through a…
Signatures of magnetic activity in the seismic data of solar-type stars observed by Kepler
A. R. G. Santos, T. L. Campante, W. J. Chaplin +8
In the Sun, the frequencies of the acoustic modes are observed to vary in phase with the magnetic activity level. These frequency variations are expected to be common in solar-type…
The Effect of Toroidal Magnetic Fields on Solar Oscillation Frequencies
René Kiefer, Markus Roth
Solar oscillation frequencies change with the level of magnetic activity. Localizing subsurface magnetic field concentrations in the Sun with helioseismology will help us to unders…
The Direct Effect of Toroidal Magnetic Fields on Stellar Oscillations: An Analytical Expression for the General Matrix Element
René Kiefer, Ariane Schad, Markus Roth
Where is the solar dynamo located and what is its modus operandi? These are still open questions in solar physics. Helio- and asteroseismology can help answer them by enabling us t…
Stellar magnetic activity and variability of oscillation parameters - An investigation of 24 solar-like stars observed by Kepler
René Kiefer, Ariane Schad, Guy Davies +1
Context. The Sun and solar-like stars undergo activity cycles for which the underlying mechanisms are not well understood. The oscillations of the Sun are known to vary with its ac…
Determination of fundamental asteroseismic parameters using the Hilbert transform
René Kiefer, Ariane Schad, Wiebke Herzberg +1
Context. Solar-like oscillations exhibit a regular pattern of frequencies. This pattern is dominated by the small and large frequency separations between modes. The accurate determ…
The PAC2MAN mission: a new tool to understand and predict solar energetic events
Jorge Amaya, Sophie Musset, Viktor Andersson +12
An accurate forecast of flare and CME initiation requires precise measurements of the magnetic energy build up and release in the active regions of the solar atmosphere. We designe…