Spectra of the X‐Ray Emission Induced in the Interaction between the Solar Wind and the Heliospheric Gas

Pepino, R.; Kharchenko, V.; Dalgarno, A.; Lallement, R.

doi:10.1086/425682

Cited by 51 publications

(58 citation statements)

References 34 publications

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“…In this case, G is predicted to be in excess of three (Kharchenko et al 2003). The value of the G ratio for the O 6+ emission induced in the interaction between the solar wind ions and heliospheric hydrogen gas has been evaluated as 6.7 (Pepino et al 2004), and for the cometary X-rays as 5.8 (Kharchenko 2005). The value which we derive from the Mars spectra is G ∼ 6 for |y| ≤ 50 and G ∼ 5 for 15 < |y| ≤ 50 .…”

Section: The He-like O 6 + Multipletmentioning

confidence: 88%

First observation of Mars with XMM-Newton

Dennerl

Lisse

Bhardwaj

et al. 2006

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In the first observation of Mars with XMM-Newton, on 20−21 November 2003, this planet is clearly detected as an X-ray source. High resolution X-ray spectroscopy with the Reflection Grating Spectrometer (RGS) confirms that the X-ray radiation from Mars is composed of two different components: one due to fluorescent scattering of solar X-rays in its upper atmosphere and the other one due to solar wind charge exchange in its exosphere. Close to Mars, the RGS spectrum is dominated by two pronounced CO 2 fluorescence lines at 23.5 Å and 23.7 Å. Fluorescence from N 2 at 31.5 Å is also observed. With increasing distance from Mars, these lines fade, while numerous (∼12) emission lines become prominent at the positions expected for de-excitation of highly ionized C, N, O, and Ne atoms, strongly resembling a cometary X-ray spectrum. The He-like O 6+ multiplet is resolved and is dominated by the spin-forbidden magnetic dipole transition 2 3 S 1 → 1 1 S 0 , confirming charge exchange as the origin of the emission, while the resonance line 2 1 P 1 → 1 1 S 0 increases in intensity closer to Mars, where the density of the exosphere is higher. The high spectral dispersion and throughput of XMM-Newton / RGS make it possible to produce X-ray images of the Martian exosphere in individual emission lines, free from fluorescent radiation. They show extended emission out to ∼8 Mars radii, with morphological differences between individual ions and ionization states. This is the first definite detection of charge exchange induced X-ray emission from the exosphere of another planet, providing a direct link to cometary X-ray emission.

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Section: The He-like O 6 + Multipletmentioning

confidence: 88%

First observation of Mars with XMM-Newton

Dennerl

Lisse

Bhardwaj

et al. 2006

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“…For example, Greenwood et al (2001) measured the X-ray spectrum emitted during the charge exchange process using a crossed-beam experiment in addition to determining the initial and final charge states of the recipient ions. (Pepino et al 2004). Summarizing, the charge exchange cross sections for many interactions that generate emissions in the 0.1-0.284 keV band remain both poorly understood and poorly determined.…”

Section: Experimental Measurements Of Charge-exchange Cross Sectionsmentioning

confidence: 99%

“…Several authors have undertaken this exercise both for detailed spectra and for broad-band X-ray emission bands with and without instrumental response functions included for specific observations such as those made by ROSAT (cf., Kharchenko and Dalgarno 2001;Pepino et al 2004;Krasnopolsky et al 2004;Robertson et al 2009b). Figure 19 shows a cometary SWCX spectrum calculated by Kharchenko and Dalgarno (2000).…”

Section: The Branching Ratio and Spectramentioning

confidence: 99%

Imaging Plasma Density Structures in the Soft X-Rays Generated by Solar Wind Charge Exchange with Neutrals

et al. 2018

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Both heliophysics and planetary physics seek to understand the complex nature of the solar wind's interaction with solar system obstacles like Earth's magnetosphere, the ionospheres of Venus and Mars, and comets. Studies with this objective are frequently conducted with the help of single or multipoint in situ electromagnetic field and particle observations, guided by the predictions of both local and global numerical simulations, and placed in con- text by observations from far and extreme ultraviolet (FUV, EUV), hard X-ray, and energetic neutral atom imagers (ENA). Each proposed interaction mechanism (e.g., steady or transient magnetic reconnection, local or global magnetic reconnection, ion pick-up, or the KelvinHelmholtz instability) generates diagnostic plasma density structures. The significance of each mechanism to the overall interaction (as measured in terms of atmospheric/ionospheric loss at comets, Venus, and Mars or global magnetospheric/ionospheric convection at Earth) remains to be determined but can be evaluated on the basis of how often the density signatures that it generates are observed as a function of solar wind conditions. This paper reviews efforts to image the diagnostic plasma density structures in the soft (low energy, 0.1-2.0 keV) X-rays produced when high charge state solar wind ions exchange electrons with the exospheric neutrals surrounding solar system obstacles. The introduction notes that theory, local, and global simulations predict the characteristics of plasma boundaries such the bow shock and magnetopause (including location, density gradient, and motion) and regions such as the magnetosheath (including density and width) as a function of location, solar wind conditions, and the particular mechanism operating. In situ measurements confirm the existence of time-and spatial-dependent plasma density structures like the bow shock, magnetosheath, and magnetopause/ionopause at Venus, Mars, comets, and the Earth. However, in situ measurements rarely suffice to determine the global extent of these density structures or their global variation as a function of solar wind conditions, except in the form of empirical studies based on observations from many different times and solar wind conditions. Remote sensing observations provide global information about auroral ovals (FUV and hard X-ray), the terrestrial plasmasphere (EUV), and the terrestrial ring current (ENA). ENA instruments with low energy thresholds (∼ 1 keV) have recently been used to obtain important information concerning the magnetosheaths of Venus, Mars, and the Earth. Recent technological developments make these magnetosheaths valuable potential targets for high-cadence wide-field-of-view soft X-ray imagers.Section 2 describes proposed dayside interaction mechanisms, including reconnection, the Kelvin-Helmholtz instability, and other processes in greater detail with an emphasis on the plasma density structures that they generate. It focuses upon the questions that remain as yet unanswered, such as the significanc...

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“…Robertson & Cravens (2003a,b) constructed sky maps of the heliospheric and geocoronal CX intensity, using global efficiency factors representing all ions at once. Pepino et al (2004) carried out similar calculations of the spectra emitted by the individual ions and of the corresponding power densities taking separate account of collisions of hydrogen and helium and distinguishing between the fast and slow solar winds.…”

Section: Introductionmentioning

confidence: 99%

Charge-transfer induced EUV and soft X-ray emissions in the heliosphere

Koutroumpa¹,

Lallement²,

Kharchenko

et al. 2006

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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.

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Spectra of the X‐Ray Emission Induced in the Interaction between the Solar Wind and the Heliospheric Gas

Cited by 51 publications

References 34 publications

First observation of Mars with XMM-Newton

First observation of Mars with XMM-Newton

Imaging Plasma Density Structures in the Soft X-Rays Generated by Solar Wind Charge Exchange with Neutrals

Charge-transfer induced EUV and soft X-ray emissions in the heliosphere

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