Search Publications
What is the source of the magnetic helicity shed by CMEs? The long-term helicity budget of AR 7978
Thompson, B. J.; Mandrini, C. H.; van Driel-Gesztelyi, L. +5 more
An isolated active region (AR) was observed on the Sun during seven rotations, starting from its birth in July 1996 to its full dispersion in December 1996. We analyse the long-term budget of the AR relative magnetic helicity. Firstly, we calculate the helicity injected by differential rotation at the photospheric level using MDI/SoHO magnetograms…
X-ray observations of a large-scale solar coronal shock wave
Aurass, H.; Khan, J. I.
We report observations of a propagating disturbance in the solar corona observed in emission in soft X-ray images from the Yohkoh Soft X-ray Telescope (SXT). The disturbance was associated with a flare which began at about 09:04 UT on 1997 November 03. This flare was associated with a type II radio burst observed at decimetric-dekametric wavelengt…
Flare waves observed in Helium I 10 830 Å. A link between Hα Moreton and EIT waves
Vršnak, B.; Hanslmeier, A.; Warmuth, A. +1 more
Three traveling disturbances recorded in the absorption line of Helium I at 10 830 Å, (He I), analogous to Hα Moreton waves, are analyzed. The morphology and kinematics of the wavefronts are described in detail. The He I wave appears as an expanding arc of increased absorption roughly corresponding to the Hα disturbance, although not as sharply de…
On the association between type II radio bursts and CMEs
Aurass, H.; Claßen, H. T.
Ground-based observations of metric (coronal) type II radio bursts are compared with observations of coronal mass ejections (CMEs) obtained by the LASCO coronagraph aboard SOHO and with decametric (interplanetary) type II bursts recorded by the WAVES instrument aboard Wind. The basic data sample comprises 63 metric type II radio bursts observed du…
On the intensity contrast of solar photospheric faculae and network elements
Solanki, S. K.; Sanahuja, B.; Ortiz, A. +2 more
Sunspots, faculae and the magnetic network contribute to solar irradiance variations. The contribution due to faculae and the network is of basic importance, but suffers from considerable uncertainty. We determine the contrasts of active region faculae and the network, both as a function of heliocentric angle and magnetogram signal. To achieve thi…
3D Coronal magnetic field from vector magnetograms: non-constant-alpha force-free configuration of the active region NOAA 8151
Amari, T.; Régnier, S.; Kersalé, E.
The Active Region 8151 (AR 8151) observed in February 1998 is the site of an eruptive event associated with a filament and a S-shaped structure, and producing a slow Coronal Mass Ejection (CME). In order to determine how the CME occurs, we compute the 3D coronal magnetic field and we derive some relevant parameters such as the free magnetic energy…
The magnetic nature of wide EUV filament channels and their role in the mass loading of CMEs
Aulanier, G.; Schmieder, B.
Previous works have shown that dark and wide EUV filament channels observed at lambda < 912 Å, are due to absorption of EUV lines in cool plasma condensations that are not observed in Hα . We extend this interpretation and we address the issue of the possible injection of their mass into CMEs, through the magneto-hydrostatic modeling in 3D of o…
UVCS/SOHO observations of a CME-driven shock: Consequences on ion heating mechanisms behind a coronal shock
Raymond, J. C.; Wu, R.; Kohl, J. +3 more
We report the observation of a 1100 km s-1 CME-driven shock with the UltraViolet Coronagraph Spectrometer (UVCS) telescope operating on board SOHO on March 3, 2000. The shock speed was derived from the type II radio burst drift rate and from UVCS observations that can yield the density profile just before the passage of the shock. A CME…
Shock-excited radio burst from reconnection outflow jet?
Mann, G.; Vršnak, B.; Aurass, H.
Models of dynamic (two-ribbon-, arcade) flares involve the formation of a system of standing slow and possibly also fast mode shock waves associated with the fast reconnection process below the erupting filament. These shocks are anticipated theoretically, but are not unambiguously confirmed by observations. In this paper we identify for the first…
Oscillations above sunspots: Evidence for propagating waves?
O'Shea, E.; Muglach, K.; Fleck, B.
We present results of an analysis of time series data observed in sunspot umbral regions. The data were obtained in the context of the SOHO Joint Observing Program (JOP) 97 in September 2000. This JOP included the Coronal Diagnostic Spectrometer (CDS) and the Michelson Doppler Imaging (MDI) instrument, both part of SOHO, the TRACE satellite and va…