Search Publications
Interplanetary flux rope ejected from an X-ray bright point. The smallest magnetic cloud source-region ever observed
Mandrini, C. H.; van Driel-Gesztelyi, L.; Démoulin, P. +5 more
Using multi-instrument and multi-wavelength observations (SOHO/MDI and EIT, TRACE and Yohkoh/SXT), as well as computing the coronal magnetic field of a tiny bipole combined with modelling of Wind in situ data, we provide evidences for the smallest event ever observed which links a sigmoid eruption to an interplanetary magnetic cloud (MC). The tiny…
Direction of the interstellar H atom inflow in the heliosphere: Role of the interstellar magnetic field
Izmodenov, V.; Alexashov, D.; Myasnikov, A.
Recently Lallement et al. (2005, Science, 307, 1447) reported that the direction of the flow of interstellar neutral hydrogen in the heliosphere is deflected by ~4° from the direction of the pristine local interstellar gas flow. The most probable physical phenomenon responsible for such a deviation is the interstellar magnetic field inclined to th…
The CME-flare relationship: Are there really two types of CMEs?
Vršnak, B.; Sudar, D.; Ruždjak, D.
We present a statistical analysis of 545 flare-associated CMEs and 104 non-flare CMEs observed in the heliocentric distance range 2-30 solar radii. We found that both data sets show quite similar characteristics, contradicting the concept of two distinct (flare/non-flare) types of CMEs. In both samples there is a significant fraction of CMEs showi…
Global solar Doppler velocity determination with the GOLF/SoHO instrument
Jiménez-Reyes, S. J.; García, R. A.; Pallé, P. L. +10 more
The Global Oscillation at Low Frequencies (GOLF) experiment is a resonant scattering spectrophotometer on board the Solar and Heliospheric Observatory (SoHO) mission, originally designed to measure the disk-integrated solar oscillations of the Sun. This instrument was designed in a relative photometric mode involving both wings of the neutral sodi…
Evolution and rotation of large-scale photospheric magnetic fields of the Sun during cycles 21-23. Periodicities, north-south asymmetries and r-mode signatures
Stenflo, J. O.; Berdyugina, S. V.; Knaack, R.
We present the results of an extensive time series analysis of longitudinally-averaged synoptic maps, recorded at the National Solar Observatory (NSO/Kitt Peak) from 1975 to 2003, and provide evidence for a multitude of quasi-periodic oscillations in the photospheric magnetic field of the Sun. In the low frequency range, we have located the source…
Spatially resolved microwave pulsations of a flare loop
Melnikov, V. F.; Nakariakov, V. M.; Shibasaki, K. +1 more
A microwave burst with quasi-periodic pulsations was studied with high spatial resolution using observations with the Nobeyama Radioheliograph (NoRH). We found that the time profiles of the microwave emission at 17 and 34 GHz exhibit quasi-periodic (with two well defined periods P_1= 14-17 s and P_2= 8-11 s) variations of the intensity at differen…
A model of the Alfvén speed in the solar corona
Mann, G.; Warmuth, A.
We present an analytic model of the Alfvén speed vA in the solar corona. The coronal magnetic field is modeled by a radial component representing the global field and by a dipole representing an active region. The free parameters of the model are constrained by actual observations of solar magnetic fields and coronal electron densities.…
High-speed coronal rain
Peter, H.; Hansteen, V. H.; De Groof, A. +1 more
At high spatial and temporal resolution, coronal loops are observed to have a highly dynamic nature. Recent observations with SOHO and TRACE frequently show localized brightenings "raining" down towards the solar surface. What is the origin of these features? Here we present for the first time a comparison of observed intensity enhancements from a…
Sensitivity of spectral lines to temperature, velocity, and magnetic field
Bellot Rubio, L. R.; del Toro Iniesta, J. C.; Cabrera Solana, D.
We present an analytical and numerical study of the sensitivity of weak solar photospheric lines to temperature, velocity, and magnetic fields. Our investigation is based on the concept of response functions (Landi degl'Innocenti & Landi degl'Innocenti 1977; Ruiz Cobo & del Toro Iniesta 1994). Lines commonly used in solar spectropolarimetr…
The Ne/O abundance ratio in the quiet Sun
Young, P. R.
Context: .
Aims: .To determine the neon-to-oxygen abundance in the quiet Sun, a proxy for the photospheric abundance ratio.
Methods: .An emission measure method applied to extreme ultraviolet emission lines of Ne iv-vi and O iii-v ions observed by the Coronal Diagnostic Spectrometer on the SOHO satellite.
Results: .The average Ne/O abu…