Search Publications
On the Nature of Prominence Absorption and Emission in Highly Ionized Iron and in Neutral Hydrogen
Engvold, Oddbjørn; Jakobsson, Hans; Tandberg-Hanssen, Einar +2 more
We have studied the behavior of the emission in the highly ionized EUV lines Fe ix/x, 171 Å, Fe xii, 195 Å, and Fe xv, 284 Å observed in quiescent prominences. Kucera, Andretta, and Poland (1998) have explained the absorption of other highly ionized metallic EUV lines as due to absorption in the hydrogen continuum. However, since the authors notic…
Photospheric Network as the Energy Source for the quiet-Sun corona
Tarbell, T.; Ryutova, M.; Woo, R. +1 more
We propose a mechanism for the formation of a magnetic energy avalanche based on highly dynamic phenomena within the ubiquitous small-scale network magnetic elements in the quiet photosphere. We suggest that this mechanism may provide constant mass and energy supply for the corona and fast wind. Constantly emerging from sub-surface layers, flux tu…
Sunspot Plumes and Flow Channels
Wilhelm, K.; Fredvik, T.; Kjeldseth-Moe, O. +2 more
It is well known that sunspots are dark. This statement is not correct in the sunspot atmosphere between the chromosphere and the corona, where sunspots often are brighter than their surroundings. The brightest feature in the sunspot transition region is called a sunspot plume. Not all sunspots contain a plume. We find that 20 out of 21 sunspots s…
Electron density variations during ultraviolet transient events
Doyle, J. G.; Madjarska, M. S.; Teriaca, L.
% High-resolution temporal observations performed with the SUMER spectrometer on SOHO provide an opportunity to investigate the electron density variations in the `quiet-Sun' solar transition region due to UV transient events. Two datasets obtained in the density sensitive lines belonging to the O iv 1400 Å multiplet were searched for such events,…
Sharp Decreases of Solar Metric Radio Storm Emission
Kahler, S.; Aurass, H.; Chertok, I. M. +1 more
We discuss a little-known variety of sharp decreases of long-duration meter-wavelength noise storms and type IV bursts. A survey of the IZMIRAN and AIP radio observations shows that a decrease or nearly complete disappearance of the continuum and bursts developing over tens of minutes without a subsequent recovery of the radio flux occasionally oc…
Ion-Sound Model of Microwave Spikes with Fast Shocks in the Reconnection Region
Fu, Q. J.; Chernov, G. P.; Hanaoka, Y. +1 more
A new model for solar spike bursts is considered based on the interaction of Langmuir waves with ion-sound waves: l+s→t. Such a mechanism can operate in shock fronts, propagating from a magnetic reconnection region. New observations of microwave millisecond spikes are discussed. They have been observed in two events: 4 November 1997 between 05:52-…
Mesogranulation and Turbulence in Photospheric Flows
Lawrence, J. K.; Cadavid, A. C.; Ruzmaikin, A.
Below the scale of supergranules we find that cellular flows are present in the solar photosphere at two distinct size scales, approximately 2 Mm and 4 Mm, with distinct characteristic times. Simultaneously present in the flow is a non-cellular component, with turbulent scaling properties and containing 30% of the flow energy. These results are ob…
Global Asymmetry of the Sun Observed in the Extreme Ultraviolet Radiation
Zhukov, A. N.; Hochedez, J. F.; Veselovsky, I. S. +4 more
We report on observations of the solar luminosity variations in the Fe xii line (195 Å) over the period 1996-1999, which corresponds to the minimum and rising phase of the current 23rd solar cycle. The relatively or rather high temporal cadence and spatial resolution of the Extreme-ultraviolet Imaging Telescope (EIT) on board the Solar and Heliosp…
Measurement of coronal magnetic twists during loop emergence of NOAA 8069
Delaboudinière, J. -P.; Démoulin, P.; Portier-Fozzani, F. +3 more
Emerging coronal loops were studied with extreme ultraviolet observations performed by SOHO/EIT on 5 and 6 August 1997 for NOAA 8069. Physical parameters (size and twist) were determined by a new stereoscopic method. The flux tubes were measured twisted when first observed by EIT. After emerging, they de-twisted as they expanded, which corresponds…
X-ray Ejecta, White-Light CMEs and a Coronal Shock Wave
Kaiser, M. L.; Gopalswamy, N.; Yashiro, S. +1 more
We report on a coronal shock wave inferred from the metric type II burst of 13 January 1996. To identify the shock driver, we examined mass motions in the form of X-ray ejecta and white-light coronal mass ejections (CMEs). None of the ejections could be considered fast (> 400 km s−1) events. In white light, two CMEs occurred in quick…