Search Publications
Strong and Weak Damping of Slow MHD Standing Waves in Hot Coronal Loops
Dwivedi, B. N.; Pandey, V. S.
Slow magnetohydrodynamic (MHD) standing wave oscillations in hot coronal loops for both strong (i.e. τd/P∼ 1) and weak (i.e. τd/P≥ 2) damping are investigated taking account of viscosity, thermal conductivity and optically thin radiation. The individual effect of the dissipative terms is not sufficient to explain the observed…
Fast Segmentation of Solar Extreme Ultraviolet Images
De Wit, T. Dudok
A segmentation scheme for identifying large-scale structures (coronal holes, active regions, etc.) in solar extreme ultraviolet images, is presented. Unlike standard approaches, both the image intensity and the relative contribution of different wavelengths are used. Spectral information is important for compensating luminosity changes. The approa…
A Statistical Study of Transequatorial Loops
Zhang, Hongqi; Chen, Jie; Bao, Shudong
We identify 356 transequatorial loops (TLs) from the data set of Yohkoh Soft X-Ray Telescope (SXT) in the period of solar cycles 22 and 23. The classification of the TLs can be made on two bases. One is according to the magnetic polarities of the footpoints of TLs, and the other is according to the number of TLs in the same region. Based on the fi…
Comparison of the Variations of CMEs and ICMEs with those of other Solar and Interplanetary Parameters During Solar Cycle 23
Kane, R. P.
This paper examines the variations of coronal mass ejections (CMEs) and interplanetary CMEs (ICMEs) during solar cycle 23 and compares these with those of several other indices. During cycle 23, solar and interplanetary parameters had an increase from 1996 (sunspot minimum) to ∼2000, but the interval 1998-2002 had short-term fluctuations. Sunspot …
Automated Detection of EUV Prominences
Foullon, C.; Verwichte, E.
We present methods to detect automatically off-limb prominences in the extreme ultraviolet (EUV), using synoptic images taken by the extreme-ultraviolet imaging telescope (EIT) on board SOHO. The 304 Å line is essential for the detection of EUV prominences, but the optimal detection is achieved through a combined image processing of the four synop…
Solar and Heliospheric Observatory/Large Angle Spectrometric Coronagraph Polarimetric Calibration
Davila, Joseph M.; Wang, Dennis; Moran, Thomas G. +2 more
We present a polarimetric characterization and correction for the Solar and Heliospheric Observatory/Large Angle Spectrometric Coronagraph (SOHO/LASCO) C2 and C3 white light coronagraphs. By measuring the uncorrected polarization angles in solar minimum C2 coronal images, we have determined that the coronagraph acts as an optical phase retarder wh…
Origin of Coronal Shocks without Mass Ejections
Cho, K. -S.; Moon, Y. -J.; Shanmugaraju, A. +2 more
We present an analysis of all the events (around 400) of coronal shocks for which the shock-associated metric type IIs were observed by many spectrographs during the period April 1997- December 2000. The main objective of this analysis is to give evidence for the type IIs related to only flare-blast waves, and thus to find out whether there are an…
Periodicities in Irradiance and in other Solar Activity Indices During Cycle 23
Özgüç, A.; Ataç, T.; Rybak, J.
Magnetic fields give rise to distinctive features in different solar atmospheric regimes. To study this, time variations of the flare index, sunspot number and sunspot area, each index arising from different physical conditions, were compared with the solar composite irradiance throughout cycle 23. Rieger-type periodicities in these time series we…
Energetics and Dynamics of an Impulsive Flare on March 10, 2001
Sakao, Taro; Uddin, Wahab; Chandra, Ramesh +5 more
We present Hα observations from ARIES (Nainital) of a compact and impulsive solar flare that occurred on March 10, 2001 and which was associated with a CME. We have also analyzed HXT, SXT/Yohkoh observations as well as radio observations from the Nobeyama Radio Observatory to derive the energetics and dynamics of this impulsive flare. We coalign t…
The Evaporation Regime in a Confined Flare
Maltagliati, L.; Teriaca, L.; Falchi, A.
We studied the evolution of a small eruptive flare (GOES class C1) from its onset phase using multi-wavelength observations that sample the flare atmosphere from the chromosphere to the corona. The main instruments involved were the Coronal Diagnostic Spectrometer (CDS) aboard SOHO and facilities at the Dunn Solar Tower of the National Solar Obser…