Search Publications
Large-Angle Spectrometric Coronagraph Measurements of the Energetics of Coronal Mass Ejections
Howard, R. A.; Dere, K. P.; Vourlidas, A. +1 more
We examine the energetics of coronal mass ejections (CMEs) with data from the large-angle spectrometric coronagraphs (LASCO) on SOHO. The LASCO observations provide fairly direct measurements of the mass, velocity, and dimensions of CMEs. Using these basic measurements, we determine the potential and kinetic energies and their evolution for severa…
Deeply Penetrating Banded Zonal Flows in the Solar Convection Zone
Thompson, M. J.; Howe, R.; Hill, F. +5 more
Helioseismic observations have detected small temporal variations of the rotation rate below the solar surface that correspond to the so-called ``torsional oscillations'' known from Doppler measurements of the surface. These appear as bands of slower- and faster-than-average rotation moving equatorward. Here we establish, using complementary helio…
EIT Waves and Fast-Mode Propagation in the Solar Corona
Wang, Y. -M.
During the onset of coronal mass ejections, a front of enhanced EUV emission is sometimes seen to propagate away from a flaring active region across the solar disk. We present model simulations to test the hypothesis that these transients (called ``EIT waves'') represent fast-mode MHD waves. The distribution of the magnetosonic velocity vf
Active and Eruptive Prominences and Their Relationship to Coronal Mass Ejections
Gilbert, Holly R.; Holzer, Thomas E.; Burkepile, Joan T. +1 more
In order to understand better the dynamical processes in the solar atmosphere that are associated with coronal mass ejections (CMEs), we have carried out a study of prominence activity using Hα observations obtained at the Mauna Loa Solar Observatory (MLSO). After developing clear definitions of active prominences (APs) and eruptive prominences (E…
Ion Cyclotron Wave Dissipation in the Solar Corona: The Summed Effect of More than 2000 Ion Species
Cranmer, Steven R.
In this paper the dissipation of ion cyclotron resonant Alfvén waves in the extended solar corona is examined in detail. For the first time, the wave damping arising from more than 2000 low-abundance ion species is taken into account. Useful approximations for the computation of coronal ionization equilibria for elements heavier than nickel are pr…
Yohkoh SXT and SOHO EIT Observations of Sigmoid-to-Arcade Evolution of Structures Associated with Halo Coronal Mass Ejections
Sterling, Alphonse C.; Thompson, Barbara J.; Hudson, Hugh S. +1 more
A subset of the solar-disk counterparts to halo coronal mass ejections (CMEs) displays an evolution in soft X-rays (SXR) that is characterized by a preflare S-shaped structure, dubbed a ``sigmoid,'' which evolves into a postflare cusp or arcade. We examine the morphological properties of the evolution of sigmoids into cusps and arcades for four su…
Another View of the EIT Wave Phenomenon
Delannée, C.
This paper investigates three different EIT waves. The events occurred on 1997 November 3 at 10:31 UT, on 1998 January 27 at 22:19 UT, and on 1998 June 13 at 15:23 UT and were observed with EIT on board the Solar and Heliospheric Observatory (SOHO) using the 195 Å filter that contains an Fe XII line. The three events show the following similar str…
How Much Do Helioseismological Inferences Depend on the Assumed Reference Model?
Basu, Sarbani; Pinsonneault, M. H.; Bahcall, John N.
We investigate systematic uncertainties in determining the profiles of the solar sound speed, density, and adiabatic index using helioseismological techniques. We find that rms uncertainties (averaged over the Sun) of ~0.02%-0.04% are contributed to the sound-speed profile by each of three sources: (1) the choice of assumed reference model, (2) th…
Dissipation of Slow Magnetosonic Waves in Coronal Plumes
Nakariakov, V. M.; Ofman, L.; Sehgal, N.
Recently, slow magnetosonic waves were identified in polar plumes, at heights up to about 1.2 Rsolar using the Extreme Ultraviolet Imaging Telescope (EIT) observations of quasi-periodic EUV intensity fluctuations, and higher in the corona using the Ultraviolet Coronagraph Spectrometer (UVCS) white-light channel. First, we derive the lin…
Turbulent Solar Convection and Its Coupling with Rotation: The Effect of Prandtl Number and Thermal Boundary Conditions on the Resulting Differential Rotation
Toomre, J.; Elliott, J. R.; Miesch, M. S.
The dynamics of the vigorous convection in the outer envelope of the Sun must determine the transport of energy, angular momentum, and magnetic fields and must therefore be responsible for the observed surface activity and the angular velocity profile inferred helioseismically from SOI-MDI p-mode frequency splittings. Many different theoretical tr…