Search Publications
First Detection of Ar-K Line Emission from the Cygnus Loop
Katsuda, Satoru; Uchida, Hiroyuki; Tominaga, Nozomu +5 more
We observed the Cygnus Loop with XMM-Newton (9 pointings) and Suzaku (32 pointings) between 2002 and 2008. The total effective exposure time is 670.2 ks. By using all of the available data, we intended to improve a signal-to-noise ratio of the spectrum. Accordingly, the accumulated spectra obtained by the XIS and the EPIC show some line features a…
Dynamics of ion sound waves in the front of the terrestrial bow shock
Walker, S. N.; Balikhin, M. A.; Giagkiozis, I.
Single spacecraft measurements from the Cluster 3 satellite are used to identify nonlinear processes in ion-sound turbulence observed within the front of the quasiperpendicular terrestrial bow shock. Ion sound waves possess spatial scales that are too small for the efficient use of multipoint measurements on inter-satellite separation scales. Howe…
Stochastic Seismic Emission from Acoustic Glories in Solar Active Regions
Donea, Alina; Newington, Marie
Helioseismic images of active regions show enhanced seismic emission in 5 mHz oscillations in a halo surrounding the active region called the "acoustic glory". In this paper we analyse the high-frequency power excess surrounding two active regions that occurred during the "shy" ascending phase of the solar cycle 24, at the beginning of 2010. This …
Sub-THz and Hα Activity during the Preflare and Main Phases of a GOES Class M2 Event
White, Stephen M.; Kaufmann, Pierre; Marcon, Rogério +8 more
Radio and optical observations of the evolution of flare-associated phenomena have shown an initial and rapid burst at 0.4 THz only followed subsequently by a localized chromospheric heating producing an Hα brightening with later heating of the whole active region. A major instability occurred several minutes later producing one impulsive burst at…
Deriving the Physical Parameters of a Solar Ejection with an Isotropic Magnetohydrodynamic Evolutionary Model
Vourlidas, Angelos; Stenborg, Guillermo; Berdichevsky, Daniel B.
The time-space evolution of a ~50° wide coronal mass ejection (CME) on 2007 May 21 is followed remotely with the Solar Terrestrial Relations Observatory heliospheric imager HI-1, and measured in situ near Venus by the MESSENGER and Venus-Express spacecraft. The paper compares the observations of the CME structure with a simple, analytical magnetoh…
Longitudinal Distribution of Solar Flares and Their Association with Coronal Mass Ejections and Forbush Decreases
Shrivastava, Pankaj K.; Jothe, Mukesh K.; Singh, Mahendra
Major Hα solar-flare events of high optical importance have been employed to study their heliographic distribution in longitude around the Sun for the period of 2001 to 2006. A statistical analysis was performed to obtain their relationship with halo/partial-halo CMEs and Forbush decreases (Fds) of cosmic-ray intensity. Our analysis indicates that…
An Analytical Model for the Coronal Component of Major Solar Energetic Particle Events
Valtonen, Eino; Cho, Kyung-Suk; Kocharov, Leon
We formulate an analytical model of the coronal-phase acceleration observed in the beginning of major solar energetic particle (SEP) events, before the main-phase acceleration associated with coronal mass ejections (CMEs) in solar wind. The model is driven and constrained by the broadband observations of SEPs and CMEs, in particular SEP data from …
Evidence for Solar Frequency Dependence on Sunspot Type
Basu, Sarbani; Baldner, Charles S.; Bogart, Richard S.
High-degree solar mode frequencies as measured by ring diagrams are known to change in the presence of the strong magnetic fields found in active regions. We examine these changes in frequency for a large sample of active regions analyzed with data from the Michelson Doppler Imager on board the Solar and Heliospheric Observatory spacecraft, spanni…
Stars and clusters of the coma galaxies NGC 4921 and NGC 4923
Tikhonov, N. A.; Galazutdinova, O. A.
Based on deep Hubble Space Telescope ACS/WFC images, we have performed stellar photometry for the spiral and lenticular galaxies NGC 4921 and NGC 4923 in the Coma cluster. The derived Hertzsprung-Russell diagrams show that, apart from the stellar population, NGC 4921 has several thousand globular clusters. The asymmetry of their apparent distribut…
Co-analysis of Solar Microwave and Hard X-Ray Spectral Evolutions. II. In Three Sources of a Flaring Loop
Huang, Guangli; Li, Jianping
Based on the spatially resolvable data of the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) and Nobeyama Radio Heliograph (NoRH), co-analysis of solar hard X-ray and microwave spectral evolution is performed in three separate sources located in one looptop (LT) and two footpoints (FPs) of a huge flaring loop in the 2003 October 24 …