Search Publications
The Radiometric and Pointing Calibration of SECCHI COR1 on STEREO
Thompson, W. T.; Reginald, N. L.
COR1 is the innermost coronagraph of the Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI) instrument suite aboard the twin Solar Terrestrial Relations Observatory (STEREO) spacecraft. The paired COR1 telescopes observe the white-light K-corona from 1.4 to 4 solar radii in a waveband 22.5 nm wide centered on the Hα line at 656 n…
On the Relationship between Flux Emergence and CME Initiation
Zhang, Hongqi; Zhang, Mei; Zhang, Yin
We present in this paper a statistical study aimed at understanding the possible relationship between surface magnetic field variation and CME initiation. The three samples studied comprise 189 CME-source regions, 46 active regions, and 15 newly emerging active regions. Both large-scale and small-scale variations of longitudinal magnetic fields of…
Total Solar Irradiance Measurement and Modelling during Cycle 23
Mekaoui, S.; Dewitte, S.
During solar cycle 23, which is now close to its end, variations of the total solar irradiance were measured by six different instruments, providing four independent time series of the irradiance variation over the complete solar cycle. A new composite time series constructed using five of these six instruments provides unprecedented instrument st…
Multiscale Analysis of Active Region Evolution
Maguire, K.; Gallagher, P. T.; Young, C. A. +4 more
Flows in the photosphere of solar active regions are turbulent in nature. Because magnetic fields are frozen into the plasma on the solar surface, magnetograms can be used to investigate the processes responsible for structuring active regions. Here, a continuous wavelet technique is developed, analyzed, and used to investigate the multiscale stru…
Mechanics of Seismic Emission from Solar Flares
Lindsey, C.; Donea, A. -C.
Instances of seismic transients emitted into the solar interior in the impulsive phases of some solar flares offer a promising diagnostic tool, both for understanding the physics of solar flares and for the general development of local helioseismology. Among the prospective contributors to flare acoustic emission that have been considered are: i) …
The Recovery of CME-Related Dimmings and the ICME's Enduring Magnetic Connection to the Sun
Zhukov, A. N.; Mandrini, C. H.; van Driel-Gesztelyi, L. +5 more
It is generally accepted that transient coronal holes (TCHs, dimmings) correspond to the magnetic footpoints of CMEs that remain rooted in the Sun as the CME expands out into the interplanetary space. However, the observation that the average intensity of the 12 May 1997 dimmings recover to their pre-eruption intensity in SOHO/EIT data within 48 h…
Probing the Subsurface Structures of Active Regions with Ring-Diagram Analysis
Basu, Sarbani; Antia, H. M.; Bogart, Richard S. +1 more
We analyze the variations in the near-surface profiles of sound speed and adiabatic constant between active regions and neighboring quiet-Sun areas using the technique of ring-diagram analysis and inversions of the frequency differences between the regions. This approach minimizes the systematic observational effects on the fitted spectral model p…
A New Forecasting Index for Solar Wind Velocity Based on EIT 284 Å Observations
Luo, Bingxian; Zhong, Qiuzhen; Liu, Siqing +1 more
Various solar wind forecasting methods have been developed during the past decade, such as the Wang - Sheeley model and the Hakamada - Akasofu - Fry Version 2 (HAFv2) model. Also, considerable correlation has been found between the solar wind speed v and the coronal hole (CH) area AM on the visible side of the Sun, showing quantitative …
Observations of Low-Latitude Coronal Plumes
Wang, Y. -M.; Muglach, K.
Using Fe IX/X 17.1 nm observations from the Extreme-Ultraviolet Imaging Telescope (EIT) on the Solar and Heliospheric Observatory (SOHO), we have identified many coronal plumes inside low-latitude coronal holes as they transited the solar limb during the late declining phase of cycle 23. These diffuse, linear features appear to be completely analo…
Short-Period Fluctuations in Coronal Mass Ejection Activity during Solar Cycle 23
Lara, Alejandro; Borgazzi, Andrea; Mendes, Odim, Jr. +2 more
We have constructed a time series of the number of coronal mass ejections (CMEs) observed by SOHO/LASCO during solar cycle 23. Using spectral analysis techniques (the maximum entropy method and wavelet analysis) we found short-period (< one year) semiperiodic activity. Among others, we found interesting periodicities at 193, 36, 28, and 25 days…