Search Publications
Time Variability of Active Region Loops Observed with the Coronal Diagnostic Spectrometer (Cds) on SOHO
Kjeldseth-Moe, O.; Brekke, P.
Monochromatic images from the Coronal Diagnostic Spectrometer (CDS) of loops above active regions show clear evidence of rapid time variability. The rapidly changing conditions that we observe give a new conception of loop systems that has never before been seriously considered. Loop systems, particularly in emission lines formed at temperatures i…
Adiabatic Deceleration of Solar Energetic Particles as Deduced from Monte Carlo Simulations of Interplanetary Transport
Vainio, R.; Torsti, J.; Kocharov, L. +1 more
Monte Carlo simulations of interplanetary transport are employed to study adiabatic energy losses of solar protons during propagation in the interplanetary medium. We consider four models. The first model is based on the diffusion-convection equation. Three other models employ the focused transport approach. In the focused transport models, we sim…
Neutral Hydrogen Column Depths in Prominences Using EUV Absorption Features
Andretta, V.; Kucera, T. A.; Poland, A. I.
Observations of prominence regions in hot coronal lines (≳106 K) at wavelengths below the hydrogen Lyman absorption limit show what appear to be absorption features. Other authors have suggested that these observed features may be due to H and He continuum absorption. But there has, as yet, been no conclusive evidence that this is indeed the case.…
Coronal line-width variations
Doyle, J. G.; Banerjee, D.; Perez, M. E.
Line-width measurements of the coronal ion Siviii confirm earlier observations which show an increase in the non-thermal velocity above the solar limb. The present data, taken at the equatorial limb, show an increase from 24 km s-1 at the limb to 28 km s-1 some 25000 km above the limb. The electron density as measured from th…
Solar Wind Velocity and Anisotropic Coronal Kinetic Temperature Measured with the O VI Doublet Ratio
Giordano, S.; Antonucci, E.; Martin, R. +1 more
Doppler dimming of the O vi resonance lines (λ1032 Å, λ1037 Å) in an expanding corona is calculated including the pumping effect on the O vi λ1037.61 Å of both C ii lines at λ1036.34 Å and λ1037.02 Å, and the effect of the width of the absorption profiles of the coronal oxygen ions along the incident radiation. The pumping effect of the C ii line …
Observations of Coronal Structures Above an Active Region by EIT and Implications for Coronal Energy Deposition
Michels, D. J.; Thompson, B. J.; Gurman, J. B. +19 more
Solar EUV images recorded by the EUV Imaging Telescope (EIT) on SOHO have been used to evaluate temperature and density as a function of position in two largescale features in the corona observed in the temperature range of 1.0-2.0 MK. Such observations permit estimates of longitudinal temperature gradients (if present) in the corona and, conseque…
Heating Events in the Quiet Solar Corona
Krucker, Säm; Benz, Arnold O.
Sensitive observations of the quiet Sun observed by EIT on the SOHO satellite in high-temperature iron-line emission originating in the corona are presented. The thermal radiation of the quiet corona is found to fluctutate significantly, even on the shortest time scale of 2 min and in the faintest pixels. The power spectrum of the emission measure…
Waves in the solar transition region
Doyle, J. G.; Banerjee, D.; O'Shea, E. +1 more
The power spectra for line intensities of several lines formed in the upper transition region around 100000 to 250000 K are presented. A period of ∼5 min is clearly present in lines due to Oiii, Oiv, and Ov. In one dataset a period approaching 10 min is present for ∼40 min. The size of the emitting features is limited to ∼7 arc sec squared. In all…
Comparison of Prominences in Hα and He II 304 Å
Wang, Haimin; Chae, Jongchul; Gurman, Joseph B. +1 more
In this letter, we bring attention to prominences which show different morphology in Hα and He ii 304 Å, as observed simultaneously by BBSO and EIT on board SOHO. Those two lines have been thought to represent similar chromospheric structures although they are formed at significantly different temperatures. We give two examples representing two ki…
Joint Nancay Radioheliograph and LASCO Observations of Coronal Mass Ejections - II. The 9 July 1996 Event
Llebaria, A.; Michels, D. J.; Schwenn, R. +10 more
The development of a coronal mass ejection on 9 July 1996 has been analyzed by comparing the observations of the LASCO/SOHO coronagraphs with those of the Nancay radioheliograph. The spatial and temporal evolution of the associated radioburst is complex and involves a long-duration continuum. The analysis of the time sequence of the radio continuu…