Search Publications
Coronal Structure of a Flaring Region and Associated Coronal Mass Ejection
Kundu, M. R.; Manoharan, P. K.
We report the multiwavelength investigations of an eruptive flare event that occurred on 2001 April 2 at about 11 UT. The manifestations associated with this flare event have been studied from the near-Sun region to about 0.5 AU. The Hα images from the Meudon Spectroheliograph reveal a fast spectacular eruption of plasmoids from the flare site to …
The Evolution of Vector Magnetic Fields in an Emerging Flux Region
Kubo, M.; Lites, B. W.; Shimizu, T.
Collaborative observations of NOAA Active Region 9231 were carried out during 9 days in 2000 November using the Advanced Stokes Polarimeter (ASP), Yohkoh/SXT, TRACE, and SOHO/MDI, in order to record the evolution of the photospheric magnetic field and its related coronal response. During this period an emerging flux region (EFR) appeared in the ph…
Wavelike Properties of Solar Supergranulation Detected in Doppler Shift Data
Schou, J.
Recently, Gizon, Duvall, & Schou suggested that supergranulation has a wavelike component. In this Letter, I show that the same phenomenon can be observed using surface Doppler shift data, thereby confirming their observations, which were made using a helioseismic time-distance technique. In addition to confirming those results, I show that th…
Observational Evidence of a Magnetic Flux Rope Eruption Associated with the X3 Flare on 2002 July 15
Zhang, Hongqi; Liu, Yu; Wang, Haimin +2 more
We present the study of an eruption from the low solar atmosphere (photosphere/chromosphere) as seen in Transition Region and Coronal Explorer 1600 Å images and with the Solar and Heliospheric Observatory Michelson Doppler Imager. The eruption reached its maximum at 20:08 UT on 2002 July 15 in the NOAA Active Region 10030 (N19°, W01°), accompanied…
On the Origin of the Basal Emission from Stellar Atmospheres: Analysis of Solar C II Lines
Judge, Philip G.; Carlsson, Mats; Stein, Robert F.
Combining a variety of data with radiation hydrodynamic simulations, we examine the heating of the Sun's internetwork chromosphere and the hypothesis that the chromospheric ``basal'' emission arises because of acoustic wave dissipation. We focus on the 2s2p22D-2s22p2Po multiplet of C II near 1…
Damped Lyα Gas Metallicities at Redshifts z=0.9-2.0 from Sloan Digital Sky Survey Spectra
Turnshek, David A.; Rao, Sandhya M.; Vanden Berk, Daniel +1 more
Using Sloan Digital Sky Survey early data release spectra, we have identified 370 Mg II absorption systems with Mg II λ2796 rest equivalent widths >=1 Å and redshifts z=0.9-2.2. From our previous and ongoing Hubble Space Telescope UV spectroscopic studies, we estimate that the mean neutral hydrogen column density of a system selected in this ma…
An Extended Burst Tail from SGR 1900+14 with a Thermal X-Ray Spectrum
Hurley, Kevin; Kouveliotou, Chryssa; Göǧüş, Ersin +6 more
The soft gamma repeater SGR 1900+14 entered a new phase of activity in 2001 April initiated by the intermediate flare recorded on April 18. Ten days following this flare, we discovered an abrupt increase in the source flux between consecutive Rossi X-Ray Timing Explorer (RXTE) orbits. This X-ray flux excess decayed over the next several minutes an…
Quasi-periodic Pulsations in a Solar Microwave Burst
Kundu, M. R.; White, S. M.; Grechnev, V. V.
Quasi-periodic pulsations in solar flares can provide important information on physical conditions in flaring regions. In this paper, we study a microwave burst that showed deep quasi-periodic pulsations. The most dramatic feature of this event has been discussed by Asai and coworkers. In the second of four bursts during the flare, strongly modula…
Balmer Lines as Diagnostics of Physical Conditions in Active Galactic Nuclei Broad Emission Line Regions
Popović, L. Č.
Using a well-known method for laboratory plasma diagnostics, the Boltzmann plot, we discuss the physical properties in the broad-line regions (BLRs) of active galactic nuclei (AGNs). We apply the Boltzmann plot method to Balmer lines on a sample of 14 AGNs and find that it may indicate the existence of ``case B'' recombination or partial local the…
Discovery of a Tight Brown Dwarf Companion to theLow-Mass Star LHS 2397a
Close, Laird M.; Siegler, Nick; Freed, Melanie
Using the adaptive optics system, Hokupa`a, at Gemini North, we have directly imaged a companion around the UKIRT faint standard M8 star LHS 2397a (FS 129) at a separation of 2.96 AU. Near-infrared photometry of the companion has shown it to be an L7.5 brown dwarf and confirmed the spectral type of the primary to be M8. We also derive a substellar…