Enhancement of Terrestrial Diffuse X-Ray Emission Associated with Coronal Mass Ejection and Geomagnetic Storm

Ezoe, Yuichiro; Miyoshi, Yoshizumi; Yoshitake, Hiroshi; Mitsuda, Kazuhisa; Terada, Naoki; Oishi, S.; Ohashi, T.

doi:10.1093/pasj/63.sp3.s691

Cited by 32 publications

(48 citation statements)

References 44 publications

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“…Figure 39 shows how contributions from the species-dependent solar wind charge exchange line emissions can be combined with emissions from the nonvariable diffuse sky and contributions from energetic protons to fit a background-subtracted and flare-cleaned XMM-Newton spectrum observed during a coronal mass emission (Carter et al 2010). Ezoe et al (2011) With accurate magnetohydrodynamic models describing the Earth's plasma environment, it should also be possible to infer exospheric neutral densities from soft X-ray observations. Here observations suggest that models underestimate outer exosphere densities.…”

Section: Line Emissions Near Earthmentioning

confidence: 99%

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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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Section: Line Emissions Near Earthmentioning

confidence: 99%

“…Here observations suggest that models underestimate outer exosphere densities. Inspecting case and statistical studies of Suzaku observations, both Ezoe et al (2011) andIshikawa (2013) concluded that observed emissions require greater neutral densities beyond 10 R E than current exospheric models predict.…”

Section: Line Emissions Near Earthmentioning

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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“…1) during our observations, we would have in general expected a large increase in the measured X-ray flux and spectral hardness due to the presence of highly charged ions (as shown by the examples of an ICME interacting with the exosphere of the Earth; Ezoe et al 2011;Carter et al 2010). Approximately 10% of ICMEs appear to exhibit only weak compositional anomalies (Richardson & Cane 2004).…”

Section: X-ray Lightcurvementioning

confidence: 85%

SimultaneousSwiftX-ray and UV views of comet C/2007 N3 (Lulin)

Carter

Bodewits

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et al. 2012

A&A

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Aims. We present an analysis of simultaneous X-Ray and UV observations of comet C/2007 N3 (Lulin) taken on three days between January 2009 and March 2009 using the Swift observatory. Methods. For our X-ray observations, we used basic transforms to account for the movement of the comet to allow the combination of all available data to produce an exposure-corrected image. We fit a simple model to the extracted spectrum and measured an X-ray flux of 4.3 ± 1.3 × 10 −13 erg cm −2 s −1 in the 0.3 to 1 keV band. In the UV, we acquired large-aperture photometry and used a coma model to derive water production rates given assumptions regarding the distribution of water and its dissociation into OH molecules about the comet's nucleus. Results. We compare and discuss the X-ray and UV morphology of the comet. We show that the peak of the cometary X-ray emission is offset sunward of the UV peak emission, assumed to be the nucleus, by approximately 35 000 km. The offset observed, the shape of X-ray emission and the decrease of the X-ray emission comet-side of the peak, suggested that the comet was indeed collisionally thick to charge exchange, as expected from our measurements of the comet's water production rate (6-8 ×10 28 mol s −1 ). The X-ray spectrum is consistent with solar wind charge exchange emission, and the comet most likely interacted with a solar wind depleted of very highly ionised oxygen. We show that the measured X-ray lightcurve can be very well explained by variations in the comet's gas production rates, the observing geometry and variations in the solar wind flux.

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“…Roughly 3% of Suzaku observations have detectable SWCX emission (Ishi et al 2017). Some events, such as those studied by Ezoe et al (2010) or Ezoe et al (2011) occurred in the flanks of the magnetosheath. Analyses generally assumed a magnetospheric origin and, given the observing geometry, special effort was made to demonstrate that the excess emission was indeed charge exchange, due to correlation with and lag from solar wind features, rather than scattered solar X-rays.…”

Section: Suzakumentioning

confidence: 99%

Solar wind charge exchange: an astrophysical nuisance

Küntz

2018

Astron Astrophys Rev

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Solar Wind Charge-Exchange (SWCX) emission is present in every Xray observation of an astrophysical object. The emission is problematic when one cannot remove the foreground by the simultaneous measurement of a nearby field. SWCX emission is a serious impediment to the study of the diffuse hot ISM, including the Galactic halo, as its contribution to diagnostic emission lines is temporally variable. Modeling the SWCX emission, in order to remove it from our observations, has proven to be more difficult than originally anticipated. This work reviews our current understanding of SWCX emission, with special attention to all of the components required for future modeling tools. Since, in the absence of such a tool, observing programs can still be constructed to minimize the effect of SWCX, mitigation strategies are discussed. Although some aspects of SWCX will be very difficult to characterize, progress continues on many fronts.

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Enhancement of Terrestrial Diffuse X-Ray Emission Associated with Coronal Mass Ejection and Geomagnetic Storm

Cited by 32 publications

References 44 publications

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

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

SimultaneousSwiftX-ray and UV views of comet C/2007 N3 (Lulin)

Solar wind charge exchange: an astrophysical nuisance

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