Search Publications
Spatial and Temporal Scales of Coronal Magnetic Restructuring in the Development of Coronal Mass Ejections
Wen, Yayuan; Wang, Jingxiu; Zhao, Hui +3 more
It has been commonly accepted that coronal mass ejections (CMEs) result from the restructuring or reconfiguring of large-scale coronal magnetic fields. In this paper, we analyzed four CME events using Nançay Radioheliograph (NRH) images and the experiments onboard the Solar and Heliospheric Observatory (SOHO) spacecraft to understand the coronal r…
The April 8, 2005, Eclipse White-Light Corona
Pasachoff, Jay M.; Rušin, Vojtech; Druckmüller, Miloslav +2 more
The hybrid solar eclipse of April 8, 2005, provided a good opportunity to observe the white-light solar corona, even though the eclipse lasted just 30 seconds and could be seen only from ships in the Pacific Ocean. During the eclipse, we detected a unique `cloud' of particles in the white-light corona above the west limb ≈260°-270°. We compare thi…
The EUV Unresolved Corona
Martens, P. C. H.; Weber, Mark; Cirtain, Jonathan +1 more
The unresolved corona for three active regions (ARs) above the solar limb is investigated. Intensities measured for ions formed above 1 MK are presented as a function of height above the solar surface. The observed decrease in intensity with altitude is found to be best fit by an exponential. Furthermore, this exponential decrease is approximately…
Possibility of Excitation of Low-ℓ P-Modes by Energetic Solar Transients
Antia, H. M.; Ambastha, Ashok
We examine the temporal variation of power in low-ℓ modes using GONG data for the period of May 1995-October 2005 and compare this with disk-integrated flare and CME indices. A poor correlation between the running means of Flare Index and mode power is found. A similar result is found for CME Index also. Variations in the running mean mode power c…
Optimal Gaussian Phase-Speed Filters in Time-Distance Helioseismology
Birch, A. C.; Couvidat, S.
Gaussian phase-speed filters are widely used in time-distance helioseismology to select specific wave packets whose travel times are then measured at the solar surface. This filtering increases the signal-to-noise (S/N) ratio of the temporal cross-covariances that are fitted to derive the travel times. The central phase speeds of these Gaussian fi…
Electron Acceleration and Transport During the November 5, 1998 Solar Flare At ∼13:34 UT
Aulanier, G.; Yan, Y.; Karlický, M. +3 more
This paper deals with a detailed analysis of spectral and imaging observations of the November 5, 1998 (Hα 1B, GOES M1.5) flare obtained over a large spectral range, i.e., from hard X-rays to radiometric wavelengths. These observations allowed us to probe electron acceleration and transport over a large range of altitudes that is to say within sma…
The Double Structure of the Coronal Streamer Belt
Eselevich, M. V.; Eselevich, V. G.
Increasing the effective spatial resolution when analyzing LASCO-C2/SOHO data helped to reveal the existence of double-ray structure in the streamer belt, both in the absence and presence of belt bends. Streamer-belt rays located in the plane of the sky are demonstrated to deviate poleward (north- and southward, respectively, in the N and S hemisp…
Multiwavelength Analysis of an Active Region
Vial, J. -C.; Gontikakis, C.; Nindos, A. +4 more
We study active region NOAA 8541, observed with instruments on board SOHO, as well as with TRACE. The data set mainly covers the transition region and the low corona. In selected loops studied with SUMER on SOHO, the VIII 770 Å line is systematically redshifted. In order to estimate the plasma velocity, we combine the Doppler shifts with proper mo…
Quiet Sun Contribution to Variations in the Total Solar Irradiance
Withbroe, George L.
An analysis of spatially-resolved measurements of the intensity of the photospheric continuum by the Michelson Doppler Imager (MDI) on the SOHO spacecraft indicates that these data can be used to study variations of the Total Solar Irradiance (TSI). Since the techniques employed depend upon ratios of intensities measured by MDI, they are independe…
On Deriving Plasma Velocity Information from CDS/NIS Observations: Application to the Dynamics of Blinkers
Brooks, David Hamilton; Bewsher, Danielle
Using standard instrument software and two independently developed data reduction and analysis procedures, we re-examine the accuracy of plasma velocity information derived from data obtained by the Solar and Heliospheric Observatory (SOHO)-Coronal Diagnostic Spectrometer (CDS). We discuss only the Ov 629 Å line data obtained by the Normal Inciden…