Search Publications
The Sub-surface Structure of a Large Sample of Active Regions
Bogart, R. S.; Basu, S.; Baldner, C. S.
We employ ring-diagram analysis to study the sub-surface thermal structure of active regions. We present results using a large number of active regions over the course of Solar Cycle 23. We present both traditional inversions of ring-diagram frequency differences, with a total sample size of 264, and a statistical study using Principal Component A…
Using an Ellipsoid Model to Track and Predict the Evolution and Propagation of Coronal Mass Ejections
Cattell, C.; Schreiner, S.; Kersten, K. +1 more
We present a method for tracking and predicting the propagation and evolution of coronal mass ejections (CMEs) using the imagers on the STEREO and SOHO satellites. By empirically modeling the material between the inner core and leading edge of a CME as an expanding, outward propagating ellipsoid, we track its evolution in three-dimensional space. …
Latest Results Found with Ring-Diagram Analysis
Howe, R.; Hill, F.; Rabello-Soares, M. C. +9 more
Ring-diagram analysis is a helioseismic tool useful for studying the near-surface layers of the Sun. It has been employed to study near-surface shear, meridional circulation, flows around sunspots, and thermal structure beneath active regions. We review recent results obtained using ring-diagram analysis, state some of the more important outstandi…
Photospheric Stratification of a Central Umbral Dot Using Stokes Profiles Recorded by Hinode: A Different Single-Case Study
Hamedivafa, H.
We aim to study the physical nature of a central umbral dot (UD) close to disk center by analyzing full-Stokes spectra of the two Fe I lines at 630 nm recorded by the spectropolarimeter on Hinode. Thermal and magnetic properties of the UD were directly inferred from Stokes profiles. Then, we applied the inversion code SIR to retrieve a single-comp…
Equatorwards Expansion of Unperturbed, High-Latitude Fast Solar Wind
Breen, A. R.; Bisi, M. M.; Fallows, R. A. +1 more
We use dual-site radio observations of interplanetary scintillation (IPS) with extremely long baselines (ELB) to examine meridional flow characteristics of the ambient fast solar wind at plane-of-sky heliocentric distances of 24 - 85 solar radii (R⊙). Our results demonstrate an equatorwards deviation of 3 - 4∘ in the bulk fas…
Instrumental and Observational Artifacts in Quiet Sun Magnetic Flux Cancellation Functions
Pietarila, A.; Pietarila Graham, J.
Under the assumption that the photospheric quiet Sun magnetic field is turbulent, the cancellation function has previously been used to estimate the true, resolution-independent mean, unsigned vertical flux «|Bz|»true. We show that the presence of network elements, noise, and seeing complicate the measurement of accurate canc…