Search Publications
Velocity Distributions and Proton Beam Production in the Solar Wind
Voitenko, Yuriy; Pierrard, Viviane
Helios, Ulysses, and Wind spacecraft have observed the velocity distribution functions (VDFs) of solar wind particles deviating significantly from Maxwellians. We review recent models using different approximations and mechanisms that determine various observed characteristics of the VDFs for the electrons, protons and minor ions. A new generation…
Growth of Massive Black Holes at Their Late Stage
Cao, Xinwu; Xu, Ya-Di
It is believed that the growth of local massive black holes was dominated by accretion during quasar phases, while a fraction of the local black hole mass was accumulated through accreting gases at very low rates. We derive the black hole mass density as a function of redshift with the bolometric luminosity function of active galactic nuclei (AGNs…
A large crater as a probe of the internal structure of the E-type asteroid Steins
Benz, W.; Jutzi, M.; Michel, P.
Context. The detection of a large crater (2 km in diameter) on Steins, a diamond-shape asteroid with a diameter of only about 4.6 km, was a large surprise given the size of the asteroid itself. Steins belongs to the rare class of E-type asteroids, which had not been observed by any spacecraft before the Rosetta mission of the European Space Agency…
Modeling Total Solar Irradiance Variations Using Automated Classification Software on Mount Wilson Data
Ulrich, R. K.; Parker, D.; Bertello, L. +1 more
We present the results using the AutoClass analysis application available at NASA/Ames Intelligent Systems Div. (2002) which is a Bayesian, finite mixture model classification system developed by Cheeseman and Stutz (1996). We apply this system to Mount Wilson Solar Observatory (MWO) intensity and magnetogram images and classify individual pixels …
The broad-band X-ray spectrum of the Seyfert 1 galaxy, MCG+8-11-11
de Rosa, A.; Bianchi, S.; Piconcelli, E. +5 more
Aims: Evidence is mounting that the main ingredients of the unification models of active galactic nuclei may behave differently from expectations, and be intimately related to fundamental physical parameters. The availability of high signal-to-noise broad-band X-ray spectra provides us with the opportunity to study in detail all the contribut…
Large and small-scale structures of the local Galactic disc. A maximum entropy approach to the stellar velocity distribution
Cubarsi, R.
An analytical model based on the maximum entropy approach is proposed to describe the eventual asymmetries of the velocity distribution, which are collected through its sample moments. If an extended set of moments is available, the current method provides a linear algorithm, associated with a Gramian system of equations, that leads to a fast and …
Chemical reactions in the Titan’s troposphere during lightning
Kovács, Tamás; Turányi, Tamás
In the lower troposphere of the Titan the temperature is about 90 K, therefore the chemical production of compounds in the CH 4/N 2 atmosphere is extremely slow. However, atmospheric electricity could provide conditions at which chemical reactions are fast. This paper is based on the assumption that there are lightning discha…
Galileo dust data from the jovian system: 2000 to 2003
Krüger, H.; Srama, R.; Hamilton, D. P. +17 more
The Galileo spacecraft was the first man-made satellite of Jupiter, orbiting the planet between December 1995 and September 2003. The spacecraft was equipped with a highly sensitive dust detector that monitored the jovian dust environment between approximately 2 and 370 RJ (jovian radius RJ=71 492 km). The Galileo dust detect…
Deflection of Coronal Rays by Remote CMEs: Shock Wave or Magnetic Pressure?
Srivastava, A. K.; Filippov, Boris
We analyze five events of the interaction of coronal mass ejections (CMEs) with the remote coronal rays located up to 90° away from the CME as observed by the SOHO/LASCO C2 coronagraph. Using sequences of SOHO/LASCO C2 images, we estimate the kink propagation in the coronal rays during their interaction with the corresponding CMEs ranging from 180…
How are the EUV and radio polar limb-brightenings correlated?
Giménez de Castro, C. G.; Varela Saraiva, A. C.; Costa, J. E. R. +1 more
Aims: We correlate the polar limb brightening time evolution observed with pass-band filters centered at the EUV 17.1 nm (Fe ix,x) and 30.4 nm (He ii) lines with radio continuum images obtained at 17 GHz (~1.76 cm) during solar cycle 23.
Methods: We determine the limb brightening in units of the quiet Sun from daily maps at 17.1 and 30.4…