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Radio emission observed in decimetric waves associated with the onset of CMEs
Fernandes, F. C. R.; Madsen, F. R. H.; Sawant, H. S. +3 more
Since the first observations by Skylab and SMM satellites coronal mass ejections (CME) have been more and more investigated. However, until now their origin and trigger mechanism remain an open question no matter if they are associated to flares or not. Recent observations over a broad spectrum suggest that flare energy is released in regions from…
Observational evidence for velocity convergence toward magnetic neutral lines as a factor in CME initiation
Luhmann, Janet; Li, Yan; Fisher, George +1 more
One of the major challenges of space weather research and modeling is the identification of the mechanism(s) for coronal mass ejections (CMEs). A leading candidate tested in several recent numerical simulations is photospheric magnetic flux cancellation by velocity convergence toward the neutral line of an active region having sheared or twisted m…
The photospheric boundary of Sun-to-Earth coupled models
Linker, J. A.; Mikić, Z.; Fisher, G. H. +3 more
The least understood component of the Sun-to-Earth coupled system is the solar atmosphere—the visible layers of the Sun that encompass the photosphere, chromosphere, transition region and low corona. Coronal mass ejections (CMEs), principal drivers of space weather, are magnetically driven phenomena that are thought to originate in the low solar c…
Excess facular emission from an isolated active region during solar minimum: the example of NOAA AR 7978
Sanahuja, B.; Fröhlich, C.; Ortiz, A. +1 more
The facular contribution to solar irradiance variations on the short time scale is studied by analyzing a simple case of an isolated active region that crossed the solar disk during the 1996 minimum of activity, NOAA AR 7978. Its passage during several Carrington rotations, specifically from rotation 1911 to 1916, allows us to analyze the evolutio…
Past and recent observations of the solar upper atmosphere at vacuum-ultraviolet wavelengths
Wilhelm, Klaus
Our understanding of the high-temperature solar atmosphere is to a large extent based on spectroscopic observations of emission lines and continuum radiation in the vacuum-ultraviolet (VUV) wavelength range of the electromagnetic spectrum. In addition, important contributions stem from soft X-ray measurements. The VUV radiation is produced by tran…
Interplanetary phenomena associated with very intense geomagnetic storms
Schwenn, R.; Tsurutani, B. T.; Lepping, R. P. +1 more
The dominant interplanetary phenomena that are frequently associated with intense magnetic storms are the interplanetary manifestations of fast coronal mass ejections (CMEs). Two such interplanetary structures, involving an intense and long duration Bs component of the IMF are: the sheath region behind a fast forward interplanetary shoc…
Observations of shock acceleration signatures by Ulysses: the 04:08:16, day147, 1991 UT shock
Sarris, E. T.; Anagnostopoulos, G. C.; Marhavilas, P. K.
We analyze the acceleration signatures of energetic ions (E>50keV) and electrons (E>30keV) observed on day 147, 1991 UT in the vicinity of the surface of a fast-mode hydromagnetic shock, using fine time resolution measurements by the HI-SCALE instrument onboard the Ulysses spacecraft. The observations present strong evidence for the accelera…
Polar ionic conductivity profile in fair weather conditions. Terrestrial test of the Huygens/Hasi-PWA instrument aboard the Comas Sola balloon
Rodrigo, R.; López-Moreno, J. J.; Molina-Cuberos, G. J. +2 more
The permittivity wave and altimetry (PWA) instrument is a part of the CASSINI/HUYGENS HASI experiment and was designed to determine the electrical parameters of the atmosphere of Titan in 2004. In December 1995, a balloon campaign was conducted in León, Spain, to test the HASI onboard hardware and software using a HUYGENS probe mock-up in an elect…
The SOLAR2000 empirical solar irradiance model and forecast tool
Floyd, L.; Viereck, R.; Woods, T. +5 more
SOLAR2000 is a collaborative project for accurately characterizing solar irradiance variability across the spectrum. A new image- and full-disk proxy empirical solar irradiance model, SOLAR2000, is being developed that is valid in the spectral range of 1-1,000,000 nm for historical modeling and forecasting throughout the solar system. The overarch…
Early life of coronal mass ejections
Thompson, B. J.; Gopalswamy, N.
Coronal mass ejections (CMEs) are large-scale magnetized plasma structures ejected from closed magnetic field regions of the Sun. White light coronagraphic observations from ground and space have provided extensive information on CMEs in the outer corona. However, our understanding of the solar origin and early life of CMEs is still in an elementa…