Search Publications
Active region EUV transient brightenings - First Results by EIT of SOHO JOP 80
Berghmans, D.; Clette, F.
On 13 May 1998, the Extreme-Ultraviolet Imaging Telescope (EIT, on board SOHO) has produced a unique image sequence operating in 'shutterless mode' (SOHO JOP 80). In JOP 80, EIT is the lead instrument, followed by several space-born instruments (SXT, TRACE, MDI, CDS, SUMER), as well as two observatories on the ground (in La Palma and Sac Peak). Th…
Cme Associated with Transequatorial Loops and a Bald Patch Flare
Aulanier, G.; Delannée, C.
We study a flare which occurred on 3 November 1997 at 10:31 UT in the vicinity of a parasitic polarity of AR 8100. Using SOHO/EIT 195 Å observations, we identify the brightening of thin transequatorial loops connecting AR 8100 and AR 8102, and dimmings located between the two active regions. Difference images highlight the presence of a loop-like …
On the origin of solar metric type II bursts
Howard, Russell A.; Webb, David F.; Cliver, Edward W.
The vast majority of solar flares are not associated with metric Type II radio bursts. For example, for the period February 1980-July 1982, corresponding to the first two and one-half years of the Solar Maximum Mission, 95% of the ∼2500 flares with peak >25 keV count rates >100 c s−1lacked associated Type II emission. Even the ∼36…
Observations of a Propagating Disturbance in TRACE
Thompson, B. J.; Wills-Davey, M. J.
TRACE observations from 13 June 1998 in 171 and 195 Å wavelengths show a propagating disturbance, initiated near the origin of a C-class flare. The wave moves through and disrupts diffuse, overarching coronal loops. Only these overlying structures are affected by the wave; lower-lying coronal structures are unperturbed. The front does not appear i…
What is Moss?
Fletcher, L.; Schrijver, C. J.; De Pontieu, B. +3 more
TRACE observations of active regions show a peculiar extreme ultraviolet (EUV) emission over certain plage areas. Termed `moss' for its spongy, low-lying, appearance, observations and modeling imply that the phenomenon is caused by thermal conduction from 3-5 MKcoronal loops overlying the plage: moss is the upper transition region emission of hot …
Does Magnetic Flux Submerge at Flux Cancelation Sites?
Schrijver, Carolus J.; Harvey, Karen L.; Jones, Harrison P. +1 more
Simultaneous measurements of the magnetic fields in the photosphere and chromosphere were used to investigate if magnetic flux is submerging at sites between adjacent opposite polarity magnetic network elements in which the flux is observed to decrease or `cancel'. These data were compared with chromospheric and coronal intensity images to establi…
Variations of Photospheric Magnetic Field Associated with Flares and CMEs
Kosovichev, A. G.; Zharkova, V. V.
Using high-cadence magnetograms from the SOHO/MDI we have investigated variations of the photospheric magnetic field during solar flares and CMEs. In the case of a strong X-class flare of May 2, 1998, we have detected variations of magnetic field in a form of a rapidly propagating magnetic wave. During the impulsive phase of the flare we have obse…
Simulations of small-scale explosive events on the Sun
Innes, D. E.; Tóth, G.
Small-scale explosive events or microflares occur throughout the chromospheric network of the Sun. They are seen as sudden bursts of highly Doppler-shifted spectral lines of ions formed at temperatures in the range 2×104−5×105 K. They tend to occur near regions of cancelling photospheric magnetic fields and are thought to be directly associated wi…
Observation of a 3d Magnetic Null Point in the Solar Corona
Filippov, Boris
A saddle-like structure is clearly discerned in SOHO EIT images in the Fe wavebands in the active region NOAA 8113, from 6 to 10 December 1997, when the active region reached the solar limb. It appears after the emergence of a small patch of parasitic polarity near the footpoints of the loops forming the outer boundary of an arcade. There is a 3D …
On the sunspot transition region
Wilhelm, K.; Fredvik, T.; Kjeldseth-Moe, O. +2 more
The EUV line emission and relative line-of-sight velocity in the transition region between the chromosphere and corona of 36 sunspot regions are investigated, based on observations with the Coronal Diagnostic Spectrometer - CDS and the Solar Ultraviolet Measurements of Emitted Radiation - SUMER on the Solar and Heliospheric Observatory - SOHO. The…