Search Publications
Are Heating Events in the Quiet Solar Corona Small Flares? Multiwavelength Observations of Individual Events
Krucker, Säm; Benz, Arnold O.
Temporary enhancements of the coronal emission measure in a quiet region have been shown to constitute a significant energy input. Here some relatively large events are studied for simultaneous brightenings in transition region lines and in radio emission. Associated emissions are discussed and tested for characteristics known from full-sized impu…
The coupling of solar convection and rotation - (Invited Review)
Miesch, Mark S.
In recent years, helioseismology has provided an unprecedented look at the dynamics of the solar interior. These new insights have been accompanied by tremendous advances in high-performance computing technology, prompting increasingly sophisticated and realistic numerical models of solar convection. Among the most important helioseismic constrain…
Long-Period Oscillations in Polar Plumes as Observed by cds on Soho
Doyle, J. G.; Banerjee, D.; O'Shea, E.
We examine spectral time series of the transition region line O v 629Å, observed with the Coronal Diagnostic Spectrometer (CDS) on the SOHO spacecraft in July 1997. Both Fourier and wavelet transforms have been applied independently to the analysis of plume oscillations in order to find the most reliable periods. The wavelet analysis allows us to …
Local Fractional Frequency Shifts Used as Tracers of Magnetic Activity
Toomre, Juri; Hindman, Bradley; Haber, Deborah +1 more
Using data from SOI-MDI (Haber et al., 2000), we compute the local frequencies of high-degree p modes and f modes. The frequencies are obtained through ring-diagram mode fitting. The Dense-Pack data set consists of a mosaic of 189 overlapping tiles, each tracked separately at the surface rotation rate over 1664-min time intervals during the Dynami…
Stochastic Seismic Emission from Acoustic Glories and the Quiet Sun
Braun, D. C.; Lindsey, C.; Donea, A. -C.
Helioseismic images of multipolar active regions show enhanced seismic emission in 5-mHz oscillations in a halo surrounding the active region called the `acoustic glory'. The acoustic glories contain elements that sustain an average seismic emission 50% greater than similar elements in the quiet Sun. The most intense seismic emitters tend to form …
Time Variability of Rotation in Solar Convection Zone From soi-mdi
Thompson, M. J.; Howe, R.; Christensen-Dalsgaard, J. +3 more
The variation of rotation in the convection zone over a period of two years from mid-1996 is studied using inversions of SOI-MDI data. We confirm the existence of near-surface banded zonal flows migrating towards the equator from higher latitudes, and reveal that these banded flows extend substantially beneath the surface, possibly to depths as gr…
Observations of sunspot transition region oscillations
Wilhelm, K.; Kjeldseth-Moe, O.; Brynildsen, N. +2 more
Oscillations with a period of 3 minutes are observed in the transition region of six sunspots with the Solar and Heliospheric Observatory - SOHO joint observing programme for velocity fields in sunspot regions. Observations of the transition region lines O v λ629 and N v λλ1238, 1242 with the SUMER instrument show significant differences in the am…
Helioseismic Holography of Active-Region Subphotospheres - (Invited Review)
Braun, D. C.; Lindsey, C.
The development of solar acoustic holography has opened a major new diagnostic avenue in local helioseismology. It has revealed `acoustic moats' surrounding sunspots, `acoustic glories' surrounding complex active regions, and `acoustic condensations' suggesting the existence of significant seismic anomalies up to 20 Mm beneath active-region photos…
Solar Magnetoconvection - (Invited Review)
Hurlburt, N. E.; Matthews, P. C.; Rucklidge, A. M.
In recent years the study of how magnetic fields interact with thermal convection in the Sun has made significant advances. These are largely due to the rapidly increasing computer power and its application to more physically relevant parameters regimes and to more realistic physics and geometry in numerical models. Here we present a survey of rec…
Calculation of the sun's acoustic impulse response by multi-dimensional spectral factorization
Rickett, J. E.; Claerbout, J. F.
Calculation of time-distance curves in helioseismology can be formulated as a blind-deconvolution (or system identification) problem. A classical solution in one-dimensional space is Kolmogorov's Fourier domain spectral-factorization method. The helical coordinate system maps two-dimensions to one. Likewise a three-dimensional volume is representa…