Search Publications
Quasi-Periodic Releases of Streamer Blobs and Velocity Variability of the Slow Solar Wind near the Sun
Feng, S. W.; Chen, Y.; Song, H. Q. +2 more
We search for persistent and quasi-periodic release events of streamer blobs during 2007 with the Large Angle Spectrometric Coronagraph on the Solar and Heliospheric Observatory and assess the velocity of the slow solar wind along the plasma sheet above the corresponding streamer by measuring the dynamic parameters of blobs. We find ten quasi-peri…
Parameters of the Magnetic Flux inside Coronal Holes
Yurchyshyn, Vasyl; Abramenko, Valentyna; Watanabe, Hiroko
The parameters of the magnetic flux distribution inside low-latitude coronal holes (CHs) were analyzed. A statistical study of 44 CHs based on Solar and Heliospheric Observatory (SOHO)/MDI full disk magnetograms and SOHO/EIT 284 Å images showed that the density of the net magnetic flux, Bnet, does not correlate with the associated solar…
Analysis of Reconstruction Methods for Nonlinear Force-Free Fields
Myshyakov, I. I.; Rudenko, G. V.
We focus on quantitative evaluation of several methods for the reconstruction of force-free magnetic fields in the solar corona. We have studied two topics. The first is to carry out a comparison test of two approaches to implement the optimization method: (1) using a boundary layer with a weighting function and (2) involving an optimization algor…
Comparison of STEREO/EUVI Loops with Potential Magnetic Field Models
Aschwanden, M. J.; Alexander, D.; DeRosa, M. L. +2 more
The Solar Terrestrial Relations Observatory (STEREO) provides the first opportunity to triangulate the three-dimensional coordinates of active region loops simultaneously from two different vantage points in space. Three-dimensional coordinates of the coronal magnetic field have been calculated with theoretical magnetic field models for decades, b…
On the Origin, 3D Structure and Dynamic Evolution of CMEs Near Solar Minimum
St. Cyr, O. C.; Gopalswamy, N.; Yashiro, S. +4 more
We have conducted a statistical study 27 coronal mass ejections (CMEs) from January 2007 - June 2008, using the stereoscopic views of STEREO SECCHI A and B combined with SOHO LASCO observations. A flux-rope model, in conjunction with 3D triangulations, has been used to reconstruct the 3D structures and determine the actual speeds of CMEs. The orig…
3D Evolution of a Filament Disappearance Event Observed by STEREO
Schmieder, B.; Chandra, R.; Venkatakrishnan, P. +2 more
A filament disappearance event was observed on 22 May 2008 during our recent campaign JOP 178. The filament, situated in the Southern Hemisphere, showed sinistral chirality consistent with the hemispheric rule. The event was well observed by several observatories, in particular by THEMIS. One day, before the disappearance, Hα observations showed u…
Multi-Spacecraft Observations: Stream Interactions and Associated Structures
Luhmann, J. G.; Russell, C. T.; Jian, L. K. +2 more
The stream interaction region (SIR), formed when a fast stream overtakes a preceding slow stream, is the predominant large-scale solar wind structure at this early phase of the STEREO mission. Using multi-spacecraft observations from STEREO A and B, ACE, Wind, and Ulysses in 2007, we analyze three stream interaction events in depth in May, August,…
Solar Flare and CME Observations with STEREO/EUVI
Lemen, J. R.; Aschwanden, M. J.; Wuelser, J. P. +1 more
STEREO/EUVI observed 185 flare events (detected above the GOES class C1 level or at > 25 keV with RHESSI) during the first two years of the mission (December 2006 - November 2008), while coronal mass ejections (CMEs) were reported in about a third of these events. We compile a comprehensive catalog of these EUVI-observed events, containing the …
Emerging and Decaying Magnetic Flux and Subsurface Flows
Howe, R.; Komm, R.; Hill, F.
We study the temporal variation of subsurface flows of 788 active regions and 978 quiet regions. The vertical-velocity component used in this study is derived from the divergence of the measured horizontal flows using mass conservation. The horizontal flows cover a range of depths from the surface to about 16 Mm and are determined by analyzing abo…
Imaging Observations of Quasi-Periodic Pulsatory Nonthermal Emission in Two-Ribbon Solar Flares
Zimovets, I. V.; Struminsky, A. B.
Using RHESSI and some auxiliary observations we examine possible connections between the spatial and temporal structure of nonthermal hard X-ray (HXR) emission sources from the two-ribbon flares of 29 May 2003 and 19 January 2005. In each of these events quasi-periodic pulsations (QPP) with time period of 1 - 3 minutes are evident in both hard X r…