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NGC 6819: testing the asteroseismic mass scale, mass loss and evidence for products of non-standard evolution
Chaplin, W. J.; Handberg, R.; Bossini, D. +5 more
We present an extensive peakbagging effort on Kepler data of ∼50 red giant stars in the open star cluster NGC 6819. By employing sophisticated pre-processing of the time series and Markov chain Monte Carlo techniques we extracted individual frequencies, heights and line widths for hundreds of oscillation modes. We show that the 'average' asterosei…
Comparative analysis of Debrecen sunspot catalogues
Ludmány, A.; Baranyi, T.; Győri, L.
Sunspot area data are important for studying solar activity and its long-term variations. At the Debrecen Heliophysical Observatory, we compiled three sunspot catalogues: the Debrecen Photoheliographic Data (DPD), the SDO/HMI Debrecen Data (HMIDD) and the SOHO/MDI Debrecen Data. For comparison, we also compiled an additional sunspot catalogue, the…
Small electron acceleration episodes in the solar corona
James, Tomin; Subramanian, Prasad; Kontar, Eduard P.
We study the energetics of non-thermal electrons produced in small acceleration episodes in the solar corona. We carried out an extensive survey spanning 2004-2015 and shortlisted six impulsive electron events detected at 1 au that were not associated with large solar flares (GOES soft X-ray class > C1) or with coronal mass ejections. Each of t…
On the east-west longitudinally asymmetric distribution of solar proton events
Wan, W.; He, H. -Q.
A large data set of 78 solar proton events observed near the Earth's orbit during 1996-2011 is investigated. An east-west longitudinal (azimuthal) asymmetry is found to exist in the distribution of flare sources of solar proton events. With the same longitudinal separation between the flare sources and the magnetic field line footpoint of observer…
Two populations of the solar magnetic field
Obridko, V. N.; Sokoloff, D. D.; Livshits, I. M.
Dynamo theory suggests that there are two types of solar dynamo, namely the conventional mean-field dynamo, which produces large- and small-scale magnetic fields involved in the activity cycle, and also the small-scale dynamo, which produces a cycle independent small-scale magnetic field. The relative contribution of the two mechanisms to solar ma…
Carrington cycle 24: the solar chromospheric emission in a historical and stellar perspective
Schmitt, J. H. M. M.; Schröder, K. -P.; Mittag, M. +3 more
We present the solar S-index record of cycle 24, obtained by the Telescopio Internacional de Guanajuato, Robotico Espectroscopico robotic telescope facility and its high-resolution spectrograph HEROS (R ≈ 20 000), which measures the solar chromospheric Ca II H&K line emission by using moonlight. Our calibration process uses the same set of sta…
A study of a coronal hole associated with a large filament eruption
Gutiérrez, Heidy; Taliashvili, Lela; Lazarian, Alexandre +1 more
We report the results of a detailed study of an equatorial coronal hole and a dimming region related to the eruptions of a nearby large filament and subsequent coronal mass ejections (CMEs). The dynamic eruptions of the filament and the associated CMEs are probably related to the magnetic reconnection involving the magnetic field lines at the fila…
On the signatures of flare-induced global waves in the Sun: GOLF and VIRGO observations
García, Rafael A.; Kumar, Brajesh; Mathur, Savita +1 more
Recently, several efforts have been made to identify the seismic signatures of flares and magnetic activity in the Sun and Sun-like stars. In this work, we have analysed the disc-integrated velocity and intensity observations of the Sun obtained from the Global Oscillations at Low Frequencies (GOLF) and Variability of solar IRradiance and Gravity …
High-resolution spectral analysis of unevenly spaced data using a regularization approach
Seghouani, N.
The problem of estimating the power spectrum of unevenly spaced time series is considered. Indeed, this problem is quite common in ground-based astronomy, and the use of classical methods leads to aliased frequency detection. Moreover, the spectral resolution is limited by the observation time (Shannon-Nyquist law). We propose a regularized method…