X‐ray imaging of Kelvin‐Helmholtz waves at the magnetopause

Sun, Tianran; Wang, C.; Wei, Fei; Sembay, S.

doi:10.1002/2014ja020497

Cited by 31 publications

(35 citation statements)

References 39 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The model we use to calculate the X‐ray intensity along a given direction ( I X ) is similar to that described by Sun et al (), which is the line integration of the X‐ray emissivity P X :

I_{X} = \frac{1}{4 π} \int P_{X} normald r = \frac{1}{4 π} \int α_{X} n_{H} n_{s w} ⟨ g ⟩ normald r false(keV \cdot {cm}^{- 2} \cdot s^{- 1} \cdot {sr}^{- 1} false),

…”

Section: Model Descriptionmentioning

confidence: 99%

“…Connor and Carter () selected a case of an XMM‐Newton observation and compared the simulation result with observation in order to estimate the exospheric neutral density. Transient structures on the magnetopause such as flux transfer events and Kelvin‐Helmholtz waves were also investigated numerically (Collier et al, ; Sun et al, ). Despite these studies, there are still some basic issues not sufficiently analyzed.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Soft X‐ray Imaging of the Magnetosheath and Cusps Under Different Solar Wind Conditions: MHD Simulations

et al. 2019

Self Cite

View full text Add to dashboard Cite

The soft X-ray emissions from the Earth's magnetosheath and cusp regions are simulated under different solar wind conditions, based on the PPMLR-MHD code. The X-ray images observed by a hypothetical telescope are presented, and the basic responses of the magnetopause and cusp regions are discernable in these images. From certain viewing geometries, the magnetopause position in the equatorial plane, as well as the latitudinal scales and azimuthal extent of cusp can be directly extracted from the X-ray images. With these reconstructed positions, the issues we are able to analyze include but are not limited to the compression of magnetopause and widening of the cusp after an enhancement of solar wind flux, as well as the erosion of the magnetopause and equatorward motion of cusp after the southward turning of the interplanetary magnetic field. Hence, the X-ray imaging is an appropriate technique to study the large-scale motion of magnetopause and cusps in response to solar wind variations.Recently, a novel approach was proposed to remotely detect the large-scale magnetopause: soft X-ray imaging (Branduardi-Raymont et al., 2012Collier et al., 2012;Sibeck et al., 2018;Walsh et al., 2016). The basic mechanism for soft X-ray emissions in the magnetosheath and cusp regions is the solar wind charge exchange (SWCX) process. On the one hand, heavy ions in high charge states, such as O 7+ , exist in the ambient solar wind. On the other hand, neutral atoms and molecules, such as the hydrogen, are ubiquitous in the geospace environment due to the Earth's exosphere. When they encounter and interact with each other, an electron can be transferred from the neutral to the ion. As a result of capturing the electron, the solar wind ion is in an electronically excited state, and then emits one or more photons in the extreme ultraviolet or soft X-ray bands while decaying to the lower-energy state. In the magnetosheath, the density of the highly charged ions is enhanced as the solar wind slows down after the bow shock. The solar wind cannot directly penetrate the magnetopause, and thus, the plasma with solar wind origin is quite tenuous inside the magnetosphere. This leads to a sharp boundary at the magnetopause in terms of the soft X-ray emissivity. The cusps are special regions on the magnetopause. The solar wind plasma can enter directly, and thus, the X-ray emissivity is expected to be higher inside of the cusps. With different solar wind fluxes and/or interplanetary magnetic fields (IMF), the X-ray emissivity in the magnetosheath and cusps can be

show abstract

“…The model we use to calculate the X‐ray intensity along a given direction ( I X ) is similar to that described by Sun et al (), which is the line integration of the X‐ray emissivity P X :

I_{X} = \frac{1}{4 π} \int P_{X} normald r = \frac{1}{4 π} \int α_{X} n_{H} n_{s w} ⟨ g ⟩ normald r false(keV \cdot {cm}^{- 2} \cdot s^{- 1} \cdot {sr}^{- 1} false),

…”

Section: Model Descriptionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Soft X‐ray Imaging of the Magnetosheath and Cusps Under Different Solar Wind Conditions: MHD Simulations

et al. 2019

Self Cite

View full text Add to dashboard Cite

show abstract

“…Although they concluded that integrated line-of-sight charge exchange soft X-ray intensities are less than those of the soft X-ray background during quiet times, they can rise to values far greater than those of the soft X-ray background during intervals of enhanced solar wind plasma fluxes. Sun et al (2015) employed the 3-D PPMLR global MHD plasma model (Hu et al 2007) and a simple exospheric neutral model to define the soft X-ray signatures that would be observed by an outward-looking low-altitude spacecraft when Kelvin-Helmholtz waves move antisunward on the flanks of the magnetosphere. They showed how the amplitude, speed, distribution, and temporal evolution of the vortices can be derived from the simulated soft Based on values reported for ROSAT observations through the flank magnetosheath .…”

Section: Relative Emission Strengthsmentioning

confidence: 99%

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

et al. 2018

Self Cite

View full text Add to dashboard Cite

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...

show abstract

“…This tool could be used to study a variety of processes. Other modeling efforts have suggested transient phenomena such as flux transfer events, and Kelvin-Helmholtz waves may also be observable through soft X-ray imaging [Sun et al, 2015].…”

Section: 1002/2016ja022348mentioning

confidence: 99%

Wide field‐of‐view soft X‐ray imaging for solar wind‐magnetosphere interactions

et al. 2016

Self Cite

View full text Add to dashboard Cite

Soft X‐ray imagers can be used to study the mesoscale and macroscale density structures that occur whenever and wherever the solar wind encounters neutral atoms at comets, the Moon, and both magnetized and unmagnetized planets. Charge exchange between high charge state solar wind ions and exospheric neutrals results in the isotropic emission of soft X‐ray photons with energies from 0.1 to 2.0 keV. At Earth, this process occurs primarily within the magnetosheath and cusps. Through providing a global view, wide field‐of‐view imaging can determine the significance of the various proposed solar wind‐magnetosphere interaction mechanisms by evaluating their global extent and occurrence patterns. A summary of wide field‐of‐view (several to tens of degrees) soft X‐ray imaging is provided including slumped micropore microchannel reflectors, simulated images, and recent flight results.

show abstract

X‐ray imaging of Kelvin‐Helmholtz waves at the magnetopause

Cited by 31 publications

References 39 publications

Soft X‐ray Imaging of the Magnetosheath and Cusps Under Different Solar Wind Conditions: MHD Simulations

Soft X‐ray Imaging of the Magnetosheath and Cusps Under Different Solar Wind Conditions: MHD Simulations

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

Wide field‐of‐view soft X‐ray imaging for solar wind‐magnetosphere interactions

Contact Info

Product

Resources

About