Related papers: Solar P-angle Alignment in GONG Dopplergrams
Observations of quiet Sun from the Solar Optical Telescope/Spectro-Polarimeter (SOT/SP) aboard the Hinode spacecraft would reveal the magnetic characters of the solar photosphere. By making use of the deep mode observations of three quiet…
Measuring the stellar position angle provides valuable information on binary stellar formation or stellar spin axis evolution. We aim to develop a method for determining the absolute stellar position angle using spectro-astrometric analysis…
Coronal oscillations offer insight into energy transport and driving in the solar atmosphere. Knowing its polarisation state helps constrain a wave's displacement and velocity amplitude, improving estimates of wave energy flux and…
The solar tachocline, located at the interface between the latitude-dependent rotation of the convection zone and the rigid radiative interior, presents high gradients of angular velocity which are of particular interest for the models of…
Aims. We report the results of a novel determination of the solar oxygen abundance using spatially resolved observations and inversions. We seek to derive the photospheric solar oxygen abundance with a method that is robust against…
Recent analysis of the helioseismic observations indicate that the previously observed surface torsional oscillations extend significantly downwards into the solar convection zone. In an attempt to understand these oscillations, we study…
An accurate solar wind speed model is important for space weather predictions, catastrophic event warnings, and other issues concerning solar wind - magnetosphere interaction. In this work, we construct a model based on convolutional neural…
We have used observations made with the helioseismic instrument LOWL collected over $\sim$ 6 years to carry out an independent study of the variations of the p-mode damping and excitation rates with solar activity. We observe significant…
We study image formation with the solar gravitational lens (SGL). We consider a point source that is positioned at a large but finite distance from the Sun. We assume that an optical telescope is positioned in the image plane, in the focal…
We investigate how helioseismic waves that originate from effective point sources interact with a sunspot. These waves are reconstructed from observed stochastic wavefields on the Sun by cross-correlating photospheric Doppler-velocity…
The solar interior is probed by the properties of the Sun's acoustic oscillations (p-modes) observed on the solar surface. The frequencies of these p-modes measured in the last three decades show long term variation similar to the 11 year…
The ring-diagram technique was developed by Frank Hill 25 years ago and developed quickly during the late 1990s. It is nowadays one of the most commonly used techniques in local helioseismology. The method consists in the power spectral…
Helioseismic holography is an imaging technique used to study heterogeneities and flows in the solar interior from observations of solar oscillations at the surface. Holograms contain noise due to the stochastic nature of solar…
The rotational Doppler shift of a photon with orbital angular momentum $\pm \ell \hbar$ is shown to be an even multiple of the angular frequency $\Omega$ of the reference frame rotation when photon is reflected from the phase-conjugating…
The interplanetary magnetic field near has a characteristic "sector" structure that reflects its polarity relative to the solar direction. Typically we observe large-scale coherence in these directions, with two or four "away" or "towards"…
The observed solar oscillation spectrum is influenced by internal perturbations such as flows and structural asphericities. These features induce splitting of characteristic frequencies and distort the resonant-mode eigenfunctions. Global…
Mode fitting or "peak-bagging" is an important procedure in helioseismology allowing one to determine the various mode parameters of solar oscillations. We have recently developed a new "pseudo-global" fitting algorithm as a way of reducing…
NASA's Solar Dynamics Observatory is delivering vector field observations of the full solar disk with unprecedented temporal and spatial resolution; however, the satellite is in a highly inclined geostationary orbit. The relative…
We present a study on the determination of rotation periods (P) of solar-like stars from the photometric irregular time-sampling of the ESA Gaia mission, currently scheduled for launch in 2013, taking into account its dependence on ecliptic…
We apply the ring-diagram technique to high resolution Dopplergrams in order to estimate the variation in oscillation mode parameters between active and quiet regions. We demonstrate that the difference in mode parameters between two quiet…