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Aims. We study the EUV/soft X-ray emission generated by charge transfer between solar wind heavy ions and interstellar neutral atoms and variations of the X-ray intensities and spectra with the line of sight direction, the observer location, the solar cycle phase and the solar wind anisotropies, and a temporary enhancement of the solar wind similar to the event observed by Snowden et al. (2004) during the XMM-Hubble Deep Field North exposure. Methods. Using recent observations of the neutral atoms combined with updated cross-sections and cascading photon spectra we have computed self-consistent distributions of interstellar hydrogen, helium and highly charged solar wind ions for a stationary solar wind and we have constructed monochromatic emission maps and spectra. We have evaluated separately the contribution of the heliosheath and heliotail, and included X-ray emission of the excited solar wind ions produced in sequential collisions to the signal. Results. In most practicable observations, the low and medium latitude X-ray emission is significantly higher at minimum activity than at maximum, especially around December. This occurs due to a strong depletion of neutrals during the high activity phase, which is not compensated by an increase of the solar wind flux. For high latitudes the emission depends on the ion species in a complex way. Intensity maps are in general significantly different for observations separated by six-month intervals. Secondary ions are found to make a negligible contribution to the X-ray line of sight intensities, because their density becomes significant only at large distances. The contribution of the heliosheath-heliotail is always smaller than 5%. We can reproduce both the intensity range and the temporal variation of the XMM-HDFN emission lines in the 0.52-0.75 keV interval, using a simple enhanced solar wind spiral stream. This suggests a dominant heliospheric origin for these lines, before, during and also after the event.

We study the possible formation of large (mesoscopic) molecular ions in an ultracold degenerate bosonic gas doped with charged particles (ions). We show that the polarization potentials produced by the ionic impurities are capable of capturing hundreds of atoms into loosely bound states. We describe the spontaneous formation of these hollow molecular ions via phonon emission and suggest an optical technique for coherent stimulated transitions of free atoms into a specific bound In this Letter, we explore theoretically the behavior of a dilute atomic Bose-Einstein condensate doped with ionic impurities. We show that the polarization interaction in a condensate can lead to the capture of large numbers of atoms into weakly bound states, resulting in the rapid formation of mesoscopically large molecular ions. We study the spontaneous dynamics of the molecular ion formation and show that the degenerate nature of the condensate, as well as the properties of collective excitations (phonons), play an important role. We further describe a coherent optical technique to prepare molecular ions in specific states. Beside the fundamental interest of studying the formation of such large many-body objects, the effects described here may open up new ways to manipulate cold atoms. In particular, the charged and tightly trapped atomic cloud represents a microtrap that could easily be manipulated and "transported" by external fields. Controlled mechanisms to manipulate tightly confined, strongly interacting atoms may also allow for new approaches for quantum information processing and for studies of other fascinating phenomena such as quantum phase transitions. Before proceeding we note an interesting analogy to early studies involving charged impurities in superfluid helium, where electron bubbles and ion "snowballs" were predicted and observed [10].We consider the situation in which few ions with ultralow kinetic energy are introduced into an atomic BEC. This can be realized, e.g., by rapidly ionizing atoms from the condensate using lasers in a process where the ejected electrons carry essentially all the kinetic energy. This would leave the BEC doped with few ions, and the BECion system in a non-equilibrium state. Alternatively, it could be possible to introduce charged impurities via controlled processes involving either a combination of ion and atom traps, or using surface traps on semiconductor surfaces. As a relaxation process, large numbers of atoms from the condensate can be captured into loosely bound states of the polarization potentials, rapidly forming shells of atoms around ions. Such a process occurs spontaneously through collisions of condensate atoms in which atoms are stimulated down into the molecular ion bound state, and the excess energy is carried away by the condensate collective excitations. We are interested in the limit T → 0, and for simplicity, we consider a homogeneous BEC with the neutral gas being the parent atom of the doping ion [11]. The ion will polarize a nearby atom (separated by a distance r) a...