Search Publications
Kinetic parameters of interstellar neutral helium. Review of results obtained during one solar cycle with the Ulysses/GAS-instrument
Witte, M.
The GAS-instrument onboard the space probe Ulysses is designed to measure the local angular distribution of the flow of interstellar neutral He-atoms within ≈3 AU distance from the sun. It allows to infer the kinetic parameters (velocity vector, temperature and density) of these particles outside the heliosphere (``at infinity''). During three obs…
Discovery of a Transient Magnetar: XTE J1810-197
Safi-Harb, Samar; Hurley, Kevin; Kouveliotou, Chryssa +10 more
We report the discovery of a new X-ray pulsar, XTE J1810-197, that was serendipitously discovered on 2003 July 15 by the Rossi X- Ray Timing Explorer (RXTE) while observing the soft gamma repeater SGR 1806-20. The pulsar has a 5.54 s spin period, a soft X-ray spectrum (with a photon index of ~4), and is detectable in earlier RXTE observations back…
Synopsis of the interstellar He parameters from combined neutral gas, pickup ion and UV scattering observations and related consequences
Möbius, E.; Noda, H.; Bzowski, M. +17 more
A coordinated effort to combine all three methods that are used to determine the physical parameters of interstellar gas in the heliosphere has been undertaken. In order to arrive at a consistent parameter set that agrees with the observations of neutral gas, pickup ions and UV backscattering we have combined data sets from coordinated observation…
Long-Term Cosmic-Ray Modulation in the Heliosphere
Ferreira, S. E. S.; Potgieter, M. S.
A time-dependent model based on a numerical solution of Parker's transport equation is used to model the modulation of cosmic-ray protons, electrons, and helium for full 11 year and 22 year modulation cycles using a compound approach. This approach incorporates the concept of propagating diffusion barriers, increases in the heliospheric magnetic f…
Observations of the helium focusing cone with pickup ions
Geiss, J.; Möbius, E.; Noda, H. +12 more
The helium gravitational focusing cone has been observed using pickup He+, first during the solar minimum in 1984-1985 with the AMPTE/IRM spacecraft, and again in more detail from 1998 to 2002 with ACE and in 2000 with Nozomi. Five traversals of the cone allow us to obtain an accurate determination of the ecliptic longitude of the inter…
High Energy Transient Explorer 2 Observations of the Extremely Soft X-Ray Flash XRF 020903
Sakamoto, T.; Yamauchi, M.; Cline, T. +36 more
We report High Energy Transient Explorer 2 (HETE-2) Wide Field X-Ray Monitor/French Gamma Telescope observations of the X-ray flash XRF 020903. This event was extremely soft: the ratio log(SX/Sγ)=0.7, where SX and Sγ are the fluences in the 2-30 and 30-400 keV energy bands, is the most extreme value obse…
Iron charge state distributions as an indicator of hot ICMEs: Possible sources and temporal and spatial variations during solar maximum
Lepri, S. T.; Zurbuchen, T. H.
It has been shown that Fe charge states greater than and equal to 16 are often observed in the presence of interplanetary coronal mass ejections (ICMEs) at 1 AU. These elevated charge states, representative of hot source regions on the Sun, provide an identifier of ICMEs independent of expansion processes and heliocentric distance. Using this new …
Characteristics of active-region sources of solar wind near solar maximum
Neugebauer, M.; Liewer, Paulett C.; Zurbuchen, Thomas
Previous studies of the source regions of solar wind sampled by ACE and Ulysses showed that some solar wind originates from open magnetic flux rooted in active regions. These solar wind sources were labeled active-region sources when the open flux was from a strong field region with no corresponding coronal hole in the NSO He 10830 Å synoptic coro…
Testing Lorentz Invariance with GRB 021206
Hurley, K.; Wunderer, C. B.; Boggs, Steven E. +1 more
Since the discovery of the cosmological origin of gamma-ray bursts (GRBs), there has been growing interest in using these transient events to probe the quantum gravity energy scale in the range 1016-1019 GeV, up to the Planck mass scale. This energy scale can manifest itself through a measurable modification in the electromag…
Nonlinear guiding center theory of perpendicular diffusion: General properties and comparison with observation
Qin, Gang; Matthaeus, W. H.; Shalchi, Andreas +1 more
A nonlinear guiding center (NLGC) theory for diffusion of charged particles perpendicular to the mean magnetic field was recently proposed. Here, we draw attention to a number of attractive features of this theory: (1) The theory provides a natural mechanism to connect the perpendicular mean free path with the parallel mean free path. In fact, the…