Search Publications
The Mars express MARSIS sounder instrument
Gurnett, D.; Orosei, R.; Picardi, G. +16 more
The Mars advanced radar for subsurface and ionospheric sounding (MARSIS) on Mars Express is the first high-frequency sounding radar operating from orbital altitudes since the Apollo 17 Lunar Sounder flown in 1972. The radar operates from a highly elliptical orbit but acquires data only from altitudes lower than 1200 km. The periapsis altitude is 2…
Discovery of Strong Radiative Recombination Continua from the Supernova Remnant IC 443 with Suzaku
Yamaguchi, H.; Ozawa, M.; Koyama, K. +4 more
We present the Suzaku spectroscopic study of the Galactic middle-aged supernova remnant (SNR) IC 443. The X-ray spectrum in the 1.75-6.0 keV band is described by an optically thin thermal plasma with the electron temperature of ~0.6 keV and several additional Lyman lines. We robustly detect, for the first time, strong radiative recombination conti…
Short-wavelength turbulence in the solar wind: Linear theory of whistler and kinetic Alfvén fluctuations
Gary, S. Peter; Smith, Charles W.
There is a debate as to the identity of the fluctuations which constitute the relatively high-frequency plasma turbulence observed in the solar wind. One school holds that these modes are kinetic Alfvén waves, whereas another opinion is that they are whistler modes. Here linear kinetic theory for electromagnetic fluctuations in homogeneous, collis…
A technique for short-term warning of solar energetic particle events based on flare location, flare size, and evidence of particle escape
Kaiser, M. L.; Ling, A. G.; Laurenza, M. +4 more
We have developed a technique to provide short-term warnings of solar energetic proton (SEP) events that meet or exceed the Space Weather Prediction Center threshold of J (>10 MeV) = 10 pr cm-2 s-1 sr-1. The method is based on flare location, flare size, and evidence of particle acceleration/escape as parameteri…
Magnetic Reconnection along Quasi-separatrix Layers as a Driver of Ubiquitous Active Region Outflows
Mandrini, C. H.; van Driel-Gesztelyi, L.; Démoulin, P. +2 more
Hinode's EUV Imaging Spectrometer (EIS) has discovered ubiquitous outflows of a few to 50 km s-1 from active regions (ARs). These outflows are most prominent at the AR boundary and appear over monopolar magnetic areas. They are linked to strong non-thermal line broadening and are stronger in hotter EUV lines. The outflows persist for at…
A Large Reservoir of Ionized Gas in the Galactic Halo: Ionized Silicon in High-Velocity and Intermediate-Velocity Clouds
Shull, J. Michael; Danforth, Charles W.; Collins, Joseph A. +1 more
The low Galactic halo is enveloped by a sheath of ionized, low-metallicity gas, which can provide a substantial (1 M ⊙ yr-1) cooling inflow to replenish star formation in the disk. Using absorption spectra from the Hubble Space Telescope and Far Ultraviolet Spectroscopic Explorer toward 37 active galactic nuclei at high latit…
Suzaku Discovery of the Strong Radiative Recombination Continuum of Iron from the Supernova Remnant W49B
Yamaguchi, H.; Ozawa, M.; Koyama, K. +2 more
We present a hard X-ray spectrum of unprecedented quality of the Galactic supernova remnant (SNR) W49B obtained with the Suzaku satellite. The spectrum exhibits an unusual structure consisting of a saw-edged bump above 8 keV. This bump cannot be explained by any combination of high-temperature plasmas in ionization equilibrium. We firmly conclude …
Globular cluster systems in nearby dwarf galaxies - II. Nuclear star clusters and their relation to massive Galactic globular clusters
Georgiev, Iskren Y.; Goudfrooij, Paul; Puzia, Thomas H. +2 more
We compare nuclear globular clusters (nGCs) in dwarf galaxies and Galactic GCs with extended (hot) horizontal branches (EHB-GCs) in order to test the suggested external origin of the latter and the conditions at which GC self-enrichment can operate. Using luminosities and structural parameters of nGCs in low-mass (mainly late-type) dwarf galaxies …
X-ray observations of the galaxy cluster PKS0745-191: to the virial radius, and beyond
Young, A. J.; Fabian, A. C.; Russell, H. R. +2 more
We measure X-ray emission from the outskirts of the cluster of galaxies PKS0745-191 with Suzaku, determining radial profiles of density, temperature, entropy, gas fraction and mass. These measurements extend beyond the virial radius for the first time, providing new information about cluster assembly and the diffuse intracluster medium out to ~1.5…
Flux Rope Formation Preceding Coronal Mass Ejection Onset
Green, L. M.; Kliem, B.
We analyze the evolution of a sigmoidal (S-shaped) active region toward eruption, which includes a coronal mass ejection (CME) but leaves part of the filament in place. The X-ray sigmoid is found to trace out three different magnetic topologies in succession: a highly sheared arcade of coronal loops in its long-lived phase, a bald-patch separatrix…