Search Publications
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…
Dynamics of a Quiescent Solar Prominence Observed with the SUMER/SOHO Instrument
Bocchialini, K.; Rovira, M.; Costa, A. +3 more
We present the results obtained from analyzing SUMER/SOHO observational data of a quiescent solar prominence. The studied prominence is made of complex structures. From the 1-hr data set, we derive characteristic frequencies in terms of intensity and velocity oscillations, as measured in 4 transition-region lines. The presence of different types o…
Erupting Magnetic Structures observed with SOHO/LASCO
Simnett, G. M.; Lyons, M. A.
We report observations, from March 1999 to December 1999, of slow-moving, low-mass (≲1014 g) erupting structures. The 20 events seen in this period appear with a double or multiple loop structure. Their speeds range from approximately 10 to 60 km s−1. There are no significant associated flares or radio signatures. Although th…
Common characteristics of CMEs and BLOBs: a new view of their possible origin
Eselevich, M. V.; Eselevich, V. G.
An analysis of the LASCO/SOHO data has shown that blobs are similar, in their basic characteristics, to CMEs, having a relatively small size and relatively low velocities. The formation of blobs and CMEs is usually accompanied by the process where a separate ray (or rays) of the streamer belt becomes occupied by additional anti-sunward traveling p…