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Observations of Chromospheric Flare Re-brightenings

Veronig, A. M.; Vršnak, B.; Bárta, M. +1 more

We investigate an active region that produced three C-class flares and one M-class flare within 2.5 hr. The morphology and location of the C-flares indicate that these events constitute a set of homologous flares. Radio observations indicate the occurrence of a downward-moving plasmoid during the impulsive phase of the M flare. We use TRACE 1700 Å…

The 15 July 2007 Ulysses ICME Event and its Track Back to the Sun

Dumitrache, Cristiana

Electron Density Estimation in the Magnetotail: a Multi-Instrument Approach

Escoubet, C. P.; Fazakerley, A. N.; Santolík, O. +7 more

Electron density is a key physical quantity to characterize any plasma medium. Its measurement is thus essential to understand the physical processes occurring in the environment of a magnetized planet, both macroscopic and microscopic. Since 2000, the four satellites of the European Space Agency (ESA) Cluster mission have been orbiting the Earth …

On high-altitude electric fields in the auroral downward current region and their coupling to ionospheric electric fields

Marklund, G. T.

The downward field-aligned current region plays an active role in magnetosphere-ionosphere coupling processes associated with aurora. A quasi-static electric field structure with a downward parallel electric field forms at altitudes between 800 km and 5000 km, accelerating ionospheric electrons upward, away from the auroral ionosphere. Other pheno…

The radio-loud active nucleus in the ``dark lens'' galaxy J1218+2953

Moór, A.; Frey, S.; Paragi, Z. +1 more

Context. There is a possibility that the optically unidentified radio source J1218+2953 may act as a gravitational lens, producing an optical arc ~4” away from the radio position. Until now, the nature of the lensing object has been uncertain since it is not detected in any waveband other than the radio. The estimated high mass-to-light ratio coul…

Winds, turbulence and waves in the clouds of Venus

Peralta, J.

The Ph.D. Thesis summarized in this abstract was accepted on 20 March 2009 at the University of the Basque Country (Spain) and awarded with the highest qualification. This work was advised by Drs. Agustín Sánchez-Lavega and Ricardo Hueso.

High resolution measurements of magnetic field fluctuations associated with transitions in solar wind parameters

Perri, S.; Balogh, A.

Fluctuations in the solar wind parameters and in the heliospheric magnetic field have been studied extensively. The nature of fluctuations has been shown to depend on the origin of the solar wind. However, the regions of transition between the high-speed and the slow speed streams have not been investigated with high resolution. In this work we us…

Observation of non-Gaussianity and phase synchronization in intermittent magnetic field turbulence in the solar-terrestrial environment

Miranda, Rodrigo A.; Chian, Abraham C. -L.; Muñoz, Pablo R. +5 more

We apply two nonlinear techniques, kurtosis and phase coherence index, to analyze magnetic field measurements from SOHO MDI solar images, ACE and Cluster data in the solar wind, and ground magnetometers in Brazil. We focus on two events: a non-ICME event in February 2002 and an ICME event in January 2005. Finite degree of non-Gaussianity and phase…

Spectral analysis of two solar twins and the colors of the Sun

Zhao, Gang; Zhao, ZhengShi; Chen, YuQin +1 more

High resolution (R∼40,000) and high signal-to-noise ratio (>150) spectra of two solar twins, HD146233 and HD195034, are obtained with the Coude Echelle Spectrograph at the 2.16 m telescope of the National Astronomical Observatories of Chinese Academy of Sciences (Xinglong, China). Based on the detailed spectrum match, comparisons of chemical co…

GEOPHYSICS, ASTRONOMY, AND ASTROPHYSICS: Is the Near-Earth Current Sheet Prior to Reconnection Unstable to Tearing Mode?

Cao, Jin-Bin; Fu, Hui-Shan; Wei, Xin-Hua +1 more

The tearing mode instability plays a key role in the triggering process of reconnection. The triggering collisionless tearing mode instability has been theoretically and numerically analyzed by many researchers. However, due to the difficulty in obtaining the observational wave number, it is still unknown whether the tearing mode instability can b…