Search Publications
Global-Scale Turbulent Convection and Magnetic Dynamo Action in the Solar Envelope
Toomre, Juri; Brun, Allan Sacha; Miesch, Mark S.
The operation of the solar global dynamo appears to involve many dynamical elements, including the generation of fields by the intense turbulence of the deep convection zone, the transport of these fields into the tachocline region near the base of the convection zone, the storage and amplification of toroidal fields in the tachocline by different…
Torsional Oscillation, Meridional Flows, and Vorticity Inferred in the Upper Convection Zone of the Sun by Time-Distance Helioseismology
Zhao, Junwei; Kosovichev, Alexander G.
By applying time-distance helioseismology measurements and inversions to Solar and Heliospheric Observatory (SOHO) Michelson Doppler Imager (MDI) dynamics campaign data, we obtain synoptic maps of subsurface plasma-flow fields at a depth of 0-12 Mm for seven solar Carrington rotations, covering the years 1996-2002, from solar-activity minimum to m…
Coronal Magnetic Field Measurements
Lin, H.; Kuhn, J. R.; Coulter, R.
A long-standing solar problem has been to measure the coronal magnetic field. We believe it determines the coronal structure and dynamics from the upper chromosphere out into the heliospheric environment. It is only recently that Zeeman splitting observations of infrared coronal emission lines have been successfully used to deduce the coronal magn…
A Study of the Kinematic Evolution of Coronal Mass Ejections
Zhang, J.; Howard, R. A.; Dere, K. P. +1 more
We report the kinematic properties of a set of three coronal mass ejections (CMEs) observed with the LASCO (Large Angle and Spectrometric Coronagraph) on the Solar and Heliospheric Observatory (SOHO) spacecraft, which showed characteristics of impulsive, intermediate, and gradual acceleration, respectively. The first CME had a 30 minute long fast …
Constraining Solar Abundances Using Helioseismology
Basu, Sarbani; Antia, H. M.
Recent analyses of solar photospheric abundances suggest that the oxygen abundance in the solar atmosphere needs to be revised downward. In this study, we investigate the consequence of this revision on helioseismic analyses of the depth of the solar convection zone and the helium abundance in the solar envelope and find no significant effect. We …
Observations and Modeling of a Filament on the Sun
van Ballegooijen, A. A.
Hα observations of a filament were obtained at the Swedish Vacuum Solar Telescope in 1998 June. The U-shaped filament has a prominent barb that exhibits interesting fine structure and internal motions. A three-dimensional magnetic model of the filament is presented. The model is based on a National Solar Observatory (Kitt Peak) magnetogram and is …
Resistive Emergence of Undulatory Flux Tubes
Aulanier, G.; Schmieder, B.; Pariat, E. +3 more
During its 2000 January flight, the Flare Genesis Experiment observed the gradual emergence of a bipolar active region, by recording a series of high-resolution photospheric vector magnetograms and images in the blue wing of the Hα line. Previous analyses of these data revealed the occurrence of many small-scale, transient Hα brightenings identifi…
Magnetic Reconnection and Mass Acceleration in Flare-Coronal Mass Ejection Events
Qiu, Jiong; Wang, Haimin; Gary, Dale E. +1 more
An observational relationship has been well established among magnetic reconnection, high-energy flare emissions and the rising motion of erupting flux ropes. In this paper, we verify that the rate of magnetic reconnection in the low corona is temporally correlated with the evolution of flare nonthermal emissions in hard X-rays and microwaves, all…
ILCT: Recovering Photospheric Velocities from Magnetograms by Combining the Induction Equation with Local Correlation Tracking
Welsch, B. T.; Fisher, G. H.; Abbett, W. P. +1 more
We present three methods for deriving the velocity field in magnetized regions of the Sun's photosphere. As a preliminary step, we introduce a Fourier-based local correlation tracking (LCT) routine that we term ``FLCT.'' By explicitly employing the observation made by Démoulin & Berger, that results determined by LCT applied to magnetograms in…
The Role of Magnetic Reconnection in the Observable Features of Solar Eruptions
Raymond, J. C.; van Ballegooijen, A. A.; Lin, J.
There are two competing classes of models for coronal mass ejections (CMEs): those that assume a preexisting magnetic flux rope and those that can make a flux rope during the eruption by magnetic reconnection. The present work is based on the model with a preexisting flux rope. We investigate the evolution of morphological features of the magnetic…