The collision of a plane parallel shock wave with a plane parallel cloud of uniform density is analysed for the case in which magnetic fields and radiative losses are not considered. General analytic solutions are discussed for the case in which the density of the cloud is greater than that of the surrounding environment. This problem generalises one of the classical problems in gas dynamics: t...

[1] Current estimates of plasma parameters in the local interstellar medium indicate that the speed of the interstellar wind, i.e., the relative speed of the local interstellar cloud with respect to the Sun, is most likely less than both the fast magnetosonic speed (subfast) and the Alfvén speed (sub-Alfvénic) but greater than the slow magnetosonic speed (superslow). In this peculiar parameter ...

Pickup ions measured deep inside the heliosphere open a new way to determine the absolute atomic density of a number of elements and isotopes in the local interstellar cloud (LIC). We derive the atomic abundance of hydrogen and the two isotopes of helium from the velocity and spatial distributions of interstellar pickup protons and ionized helium measured with the Solar Wind Ion Composition Spe...

In Laboratory Astrophysics at Leiden University a laboratory analog for following the chemical evolution of interstellar dust in space shows that the dust contains the bulk of organic material in the universe. We follow the photoprocessing of low temperature (10 K) mixtures of ices subjected to vacuum ultraviolet radiation in simulation of interstellar conditions. The most important, but necess...

Changes in the local interstellar environment of the Sun due to its encounters with interstellar clouds of different densities are an important source of long term cosmic-ray variability as measured in cosmogenic isotope records. We present a systematic study of the dependence of galactic cosmic ray intensity in the solar system on the changing background conditions of the heliosphere. We compa...

We present a stochastic model based on the Monte Carlo technique to study the inhomogeneous chemical evolution of the Galactic halo. In particular, we consider the local enrichment and subsequent mixing of the interstellar gas resulting from bursts of star formation, following explicitly the fragmentation and coalescence of interstellar gas clouds. The model takes into account the mixing of hal...

If comets are assumed to have been created in the cool, dense regions of interstellar clouds, then these macroscopic bodies have to take part in the collapse of a protostar cloud as bodies following the laws of mechanics, in contrast to the gas and microscopic dust, which follow the laws of hydrodynamics. Here we present evidence concerning the solar system comets: if the velocity distribution ...

Abstract We present the first detection of ( Z )-1,2-ethenediol, (CHOH) 2 , enol form glycolaldehyde, in interstellar medium toward G+0.693?0.027 molecular cloud located Galactic Center. have derived a column density (1.8 ± 0.1) × 10 13 cm ?2 which translates into abundance with respect to hydrogen 1.3 ?10 . The ratio between glycolaldehyde and )-1,2-ethenediol is ?5.2. discuss several viable f...