Search Publications
Relationship between CME velocity and active region magnetic energy
Venkatakrishnan, P.; Ravindra, B.
We find an empirical relationship between the initial speed of Coronal Mass Ejection (CME) and the potential magnetic field energy of the associated active region (AR) that closely resembles the Sedov relation between the speed of a blast wave and the blast energy. We conclude that it is the magnetic energy of an AR that drives the CME. The restru…
Emission and Absorption in the M87 LINER
Filippenko, Alexei V.; Ho, Luis C.; Shields, Joseph C. +2 more
The nucleus of M87 displays a LINER spectrum at optical wavelengths, with a nuclear disk of nebulosity that is resolved by the Hubble Space Telescope (HST). We present new results from optical and ultraviolet spectra of the central ~40 pc as measured by HST. In contrast with previous results for the extended disk, the emission-line spectrum of the…
The soft X-ray characteristics of solar flares, both with and without associated CMEs
Culhane, J. L.; Green, L. M.; Harra, L. K. +2 more
The complex relationship between solar flares and coronal mass ejections is investigated using a comparison of flare parameters for a total of 69 ejective and non-ejective flares. In the case of solar flares which do not show mass ejection there seems to be a clear relationship between the peak intensity and duration, with higher intensity events …
A statistical study of compressional waves in the tail current sheet
Balogh, A.; Zhang, T. L.; Klecker, B. +9 more
A statistical study of the Cluster FGM data is performed on compressional waves for 68 selected 12 min intervals when the spacecraft are in or near the neutral sheet. The data are well distributed in local time between 2100 and 0300 LT. The compressional wave power is strongly dependent on the maximum plasma flow velocity (based on the CIS-CODIF d…
The Ringed Spiral Galaxy NGC 4622. I. Photometry, Kinematics, and the Case for Two Strong Leading Outer Spiral Arms
Byrd, Gene G.; Freeman, Tarsh; Buta, Ronald J.
The intriguing nearly face-on southern ringed spiral galaxy NGC 4622, the first galaxy definitively shown to have leading spiral structure, is revisited in this paper with new images from the Hubble Space Telescope's (HST) WFPC2, together with ground-based optical and near-IR imaging, and a Fabry-Perot Hα velocity field. The data provide new infor…
Infrared Spectroscopy of 15 Radio Galaxies at 2<z<2.6
Motohara, Kentaro; Iwamuro, Fumihide; Maihara, Toshinori +7 more
Near-infrared spectra of 15 high-redshift radio galaxies (HzRGs) located at 2<z<2.6 were obtained by the OH Airglow Suppressor spectrograph mounted on the Subaru telescope. The UV-optical line ratio diagnostic diagrams indicate that half of the observed HzRGs have extended emission-line regions with low metal abundance, photoionized by a fla…
Hubble Space Telescope STIS Spectrum of RW Aurigae A: Evidence for an Ionized Beltlike Structure and Mass Ejection in Timescales of a Few Hours
Gómez de Castro, Ana I.; Verdugo, Eva
Profiles of the UV semiforbidden lines of C III]1908 and Si III]1892 of RW Aur have been obtained with the Hubble Space Telescope (HST) STIS. The C III]1908 profile shows two high-velocity components at v=+/-170 km s-1 and a central one. The Si III]1892 profile is very broad (FWHM = 293 km s
Multiple Molecular H2 Outflows in AFGL 618
Bachiller, R.; Forveille, T.; Cox, P. +3 more
We report high spatial (0.5") and high spectral (9 km s-1) resolution spectro-imaging of the 2.12 µm H2 1-->0 S(1) line in the proto-planetary nebula AFGL 618 using BEAR at the Canada-France-Hawaii Telescope. The observations reveal the presence of multiple, high-velocity, molecular outflows that align with the remar…
Galactic archaeology: initial mass function and depletion in the `thin disc'
Schröder, K. -P.; Pagel, B. E. J.
We determine the initial mass function (IMF) of the `thin disc' in the range of, approximately, 1.1 to 4 Msolar by means of a direct comparison between synthetic stellar samples [for different matching choices of IMF, star formation rate (SFR) and depletion] and a complete (volume-limited) sample of single stars near the Galactic plane …
Radial dependence of intermittency in the fast polar solar wind magnetic field using Ulysses
Balogh, A.; Pagel, C.
The Ulysses spacecraft, in a polar orbit of the Sun, spent almost 3 years sampling the pure polar coronal fast wind at solar minimum between 1994 and 1996. Turbulence in coronal fast wind, unaffected by stream shears with slow solar wind, evolves more slowly than fast wind turbulence in the ecliptic and is a more homogenous system. However, it is …