158 research outputs found
Solar wind ion charge state distributions and compound cross sections for solar wind charge exchange X-ray emission
Solar Wind Charge eXchange X-ray (SWCX) emission in the heliosphere and Earth's exosphere is a hard to avoid signal in soft X-ray observations of astrophysical targets. On the other hand, the X-ray imaging possibilities offered by the SWCX process has led to an increasing number of future dedicated space missions for investigating the solar wind-terrestrial interactions and magnetospheric interfaces. In both cases, accurate modelling of the SWCX emission is key to correctly interpret its signal, and remove it from observations, when needed. In this paper, we compile solar wind abundance measurements from ACE for different solar wind types, and atomic data from literature, including charge exchange cross-sections and emission probabilities, used for calculating the compound cross-section \begin{document}\end{document} for the SWCX X-ray emission. We calculate \begin{document}\end{document} values for charge-exchange with H and He, relevant to soft X-ray energy bands (0.1−2.0 keV) for various solar wind types and solar cycle conditions
The Solar Wind Charge-eXchange contribution to the Local Soft X-ray Background. Model to data comparison in the 0.1-1.0 keV band
The major sources of the Soft X-ray Background (SXRB), besides distinct
structures as supernovae and superbubbles (e.g. Loop I), are: (i) an absorbed
extragalactic emission following a power law, (ii) an absorbed thermal
component ~2x10^6 K) from the galactic disk and halo, (iii) an unabsorbed
thermal component, supposedly at 10^6 K, attributed to the Local Bubble and
(iv) the very recently identified unabsorbed Solar Wind Charge-eXchange (SWCX)
emission from the heliosphere and the geocorona. We study the SWCX heliospheric
component and its contribution to observed data. In a first part, we apply a
SWCX heliospheric simulation to model the oxygen lines (3/4 keV) local
intensities during shadowing observations of the MBM12 molecular cloud and a
dense filament in the south galactic hemisphere with Chandra, XMM-Newton, and
Suzaku telescopes. In a second part, we present a preliminary comparison of
SWCX model results with ROSAT and Wisconsin surveys data in the 1/4 keV band.
We conclude that, in the 3/4 keV band, the total local intensity is entirely
heliospheric, while in the 1/4 keV band, the heliospheric component seems to
contribute significantly to the local SXRB intensity and has potentially a
strong influence on the interpretation of the ROSAT and Wisconsin surveys data
in terms of Local Bubble hot gas temperature.Comment: 15 pages, 7 figures, 2 tables, 'From the Outer Heliosphere to the
Local Bubble' ISSI workshop, Bern October 200
Solar wind charge exchange X-ray emission from Mars Model and data comparison
Aims. We study the soft X-ray emission induced by charge exchange (CX)
collisions between solar-wind, highly charged ions and neutral atoms of the
Martian exosphere. Methods. A 3D multi species hybrid simulation model with
improved spatial resolution (130 km) is used to describe the interaction
between the solar wind and the Martian neutrals. We calculated velocity and
density distributions of the solar wind plasma in the Martian environment with
realistic planetary ions description, using spherically symmetric exospheric H
and O profiles. Following that, a 3D test-particle model was developed to
compute the X-ray emission produced by CX collisions between neutrals and solar
wind minor ions. The model results are compared to XMM-Newton observations of
Mars. Results. We calculate projected X-ray emission maps for the XMM-Newton
observing conditions and demonstrate how the X-ray emission reflects the
Martian electromagnetic structure in accordance with the observed X-ray images.
Our maps confirm that X-ray images are a powerful tool for the study of solar
wind - planetary interfaces. However, the simulation results reveal several
quantitative discrepancies compared to the observations. Typical solar wind and
neutral coronae conditions corresponding to the 2003 observation period of Mars
cannot reproduce the high luminosity or the corresponding very extended halo
observed with XMM-Newton. Potential explanations of these discrepancies are
discussed.Comment: 10 pages, 5 figures, accepted for publication in Astron. Astrophysic
Interplanetary Lyman line profiles: variations with solar activity cycle
Interplanetary Lyman alpha line profiles are derived from the SWAN H cell
data measurements. The measurements cover a 6-year period from solar minimum
(1996) to after the solar maximum of 2001. This allows us to study the
variations of the line profiles with solar activity. These line profiles were
used to derive line shifts and line widths in the interplanetary medium for
various angles of the LOS with the interstellar flow direction. The SWAN data
results were then compared to an interplanetary background upwind spectrum
obtained by STIS/HST in March 2001. We find that the LOS upwind velocity
associated with the mean line shift of the IP \lya line varies from 25.7 km/s
to 21.4 km/s from solar minimum to solar maximum. Most of this change is linked
with variations in the radiation pressure. LOS kinetic temperatures derived
from IP line widths do not vary monotonically with the upwind angle of the LOS.
This is not compatible with calculations of IP line profiles based on hot model
distributions of interplanetary hydrogen. We also find that the line profiles
get narrower during solar maximum. The results obtained on the line widths (LOS
temperature) show that the IP line is composed of two components scattered by
two hydrogen populations with different bulk velocities and temperature. This
is a clear signature of the heliospheric interface on the line profiles seen at
1 AU from the sun.Comment: 9 pages, 9 figure
The Solar-Cycle Temporal Variation of the Solar Wind Charge Exchange X-ray Lines
Solar wind charge exchange (SWCX) is the primary contamination to soft X-ray
emission lines from the Milky Way (MW) hot gas. We report a solar-cycle
( yr) temporal variation of observed \ion{O}{7} and \ion{O}{8}
emission line measurements in the {\it XMM-Newton} archive, which is tightly
correlated with the solar cycle traced by the sunspot number (SSN). This
temporal variation is expected to be associated with the heliospheric SWCX.
Another observed correlation is that higher solar wind (SW) fluxes lead to
higher O VII or O VIII fluxes, which is due to the magnetospheric SWCX. We
construct an empirical model to reproduce the observed correlation between the
line measurements and the solar activity (i.e., the SW flux and the SSN). With
this model we discovered a lag of yr between the O VII
flux and the SSN. This time lag is a combination of the SW transit time within
the heliosphere, the lag of the neutral gas distribution responding to solar
activity, and the intrinsic lag between the SSN and the launch of a high-energy
SW (i.e., and ). MW O VII and O VIII fluxes have mean
values of 5.4 L.U. and 1.7 L.U., which are reduced by and ,
compared to studies where the SWCX contamination is not removed. This
correction also changes the determination of the density distribution and the
temperature profile of the MW hot gas.Comment: 10 pages, 5 figures. ApJ accepte
XMM-Newton Observations of MBM 12: More Constraints on the Solar Wind Charge Exchange and Local Bubble Emissions
We present the first analysis of an XMM-Newton observation of the nearby molecular cloud MBM 12. We find that in the direction of MBM 12 the total O VII (0.57 keV) triplet emission is 1.8(+0.5/-0.6) photons/sq cm/s/sr (or Line Units - LU) while for the O VIII (0.65 keV) line emission we find a 3(sigma) upper limit of <1 LU. We also use a heliospheric model to calculate the O VII and O VIII emission generated by Solar Wind Charge-eXchange (SWCX) which we compare to the XMM-Newton observations. This comparison provides new constraints on the relative heliospheric and Local Bubble contributions to the local diffuse X-ray background. The heliospheric SWCX model predicts 0.82 LU for O VII, which accounts for approx. 46+/-15% of the observed value, and 0.33 LU for the O VIII line emission consistent with the XMM-Newton observed value. We discuss our results in combination with previous observations of the MBM 12 with CHANDRA and Suzaku
Invited Article: First Flight in Space of a Wide-Field-of-View Soft X-Ray Imager Using Lobster-Eye Optics: Instrument Description and Initial Flight Results
We describe the development, launch into space, and initial results from a prototype wide eld-of-view (FOV) soft X-ray imager that employs Lobster-eye optics and targets heliophysics, planetary, and astrophysics science. The Sheath Transport Observer for the Redistribution of Mass (STORM) is the rst instrument using this type of optics launched into space and provides proof-of-concept for future ight instruments capable of imaging structures such as the terrestrial cusp, the entire dayside magnetosheath from outside the magnetosphere, comets, the moon, and the solar wind interaction with planetary bodies like Venus and Mars
LEM All-Sky Survey: Soft X-ray Sky at Microcalorimeter Resolution
The Line Emission Mapper (LEM) is an X-ray Probe with with spectral
resolution ~2 eV FWHM from 0.2 to 2.5 keV and effective area >2,500 cm at 1
keV, covering a 33 arcmin diameter Field of View with 15 arcsec angular
resolution, capable of performing efficient scanning observations of very large
sky areas and enabling the first high spectral resolution survey of the full
sky. The LEM-All-Sky Survey (LASS) is expected to follow the success of
previous all sky surveys such as ROSAT and eROSITA, adding a third dimension
provided by the high resolution microcalorimeter spectrometer, with each 15
arcsec pixel of the survey including a full 1-2 eV resolution energy spectrum
that can be integrated over any area of the sky to provide statistical
accuracy. Like its predecessors, LASS will provide both a long-lasting legacy
and open the door to the unknown, enabling new discoveries and delivering the
baseline for unique GO studies. No other current or planned mission has the
combination of microcalorimeter energy resolution and large grasp to cover the
whole sky while maintaining good angular resolution and imaging capabilities.
LASS will be able to probe the physical conditions of the hot phases of the
Milky Way at multiple scales, from emission in the Solar system due to Solar
Wind Charge eXchange, to the interstellar and circumgalactic media, including
the North Polar Spur and the Fermi/eROSITA bubbles. It will measure velocities
of gas in the inner part of the Galaxy and extract the emissivity of the Local
Hot Bubble. By maintaining the original angular resolution, LASS will also be
able to study classes of point sources through stacking. For classes with
~ objects, it will provide the equivalent of 1 Ms of high spectral
resolution data. We describe the technical specifications of LASS and highlight
the main scientific objectives that will be addressed. (Abridged)Comment: White Paper in support of a mission concept to be submitted for the
2023 NASA Astrophysics Probes opportunity. This White Paper will be updated
when required. 30 pages, 25 figure
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