Plasma Properties in Coronal Holes Derived from Measurements of Minor Ion Spectral Lines and Polarized White Light Intensity

Esser, Ruth; Fineschi, Silvano; Dobrzycka, D.; Habbal, Shadia Rifai; Edgar, R. J.; Raymond, J. C.; Kohl, J. L.; Guhathakurta, M.

doi:10.1086/311786

Cited by 178 publications

(171 citation statements)

References 22 publications

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“…We can therefore expect that if magnetosonic pulses are excited in the solar corona, they would raise ion perpendicular temperature. This feature is consistent with observations that the perpendicular ion temperatures are higher than the parallel ones in the solar corona [7,8]. Therefore, this acceleration mechanism would be applicable to ion heating in the solar corona.…”

Section: Discussionsupporting

confidence: 91%

Theory for Finite Temperature Effects on Magnetosonic Waves in a Two-Ion-Species Plasma

Aota

Toida

2013

Plasma and Fusion Research

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The theory of magnetosonic waves perpendicular to a magnetic field in a two-ion-species plasma is extended to include finite temperature effects based on the three-fluid model with finite ion and electron pressures. First, the condition for the dispersion relation of the low-frequency mode, the lower branch of magnetosonic waves, to be approximated as a form of weak dispersion is presented. Next, by virtue of this, it is shown that the KdV equation for the low-frequency mode is valid for amplitude ε < ε max , where the upper limit of the amplitude ε max is given as a function of the ratio of the kinetic to magnetic energies, the density ratio, and the cyclotron frequency ratio of two ion species. The finite-temperature effects on linear and nonlinear high-frequency modes and on heavy-ion acceleration by the high-frequency-mode pulse are also discussed.

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Section: Discussionsupporting

confidence: 91%

Theory for Finite Temperature Effects on Magnetosonic Waves in a Two-Ion-Species Plasma

Aota

Toida

2013

Plasma and Fusion Research

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“…The electron density is an important parameter of the coronal plasma (cf. Esser et al 1999) and is critical for any determination of the solar-wind outflow velocities with the help of Doppler-dimming techniques (cf. Antonucci et al 2000;Gabriel et al 2003), as the outflow velocities deduced from such observations decrease with increasing density.…”

Section: Discussionmentioning

confidence: 99%

Solar coronal-hole plasma densities and temperatures

Wilhelm¹

2006

A&A

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Polar plumes extending from the Sun into the solar corona have long been seen during eclipses, and can now be studied without this restriction with telescopes and spectrometers on board of spacecraft. Despite the large amount of observational data available on this prominent phenomenon, it is not clear whether plumes contribute substantially to the fast solar-wind streams emanating from coronal holes. An understanding of the processes leading to the formation of bright plumes and the surrounding darker inter-plume regions in coronal holes requires a good knowledge of the physical conditions in plumes and their environment. This investigation aims at measuring the electron densities and temperatures in these regions with the help of radiance ratios of ultraviolet emission lines obtained by SUMER on SOHO. It finds densities of about 7 × 10 7 cm −3 in bright plumes and 1.3 × 10 7 cm −3 in inter-plume lanes at ≈45 Mm above the limb. At this height, the total plume cross-section relative to the size of the coronal hole was found to be less than 8%. The densities drop by a factor of roughly two over the next 80 Mm in height, in lanes a little less than seen in plumes. In this height range, the electron temperatures in plumes are ≈7.5 × 10 5 K and ≈1.13 × 10 6 K in inter-plume regions. The effective ion temperatures, deduced from the line widths, are higher and nearly independent of the altitude in plumes, whereas they increase in inter-plume regions, starting from an even higher level. No systematic dependence of the line-of-sight bulk velocities on the brightness could be found in the coronal-hole plasma.

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“…Much higher Alfvén speeds are known to exist in coronal holes, while the streamers have much lower Alfvén speeds (see e.g. Esser et al, 1999). It is expected that the quiet coronal regions have intermediate values.…”

Section: April 2003 Cmementioning

confidence: 99%

Coronal mass ejections, type II radio bursts, and solar energetic particle events in the SOHO era

et al. 2008

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Abstract.Using the extensive and uniform data on coronal mass ejections (CMEs), solar energetic particle (SEP) events, and type II radio bursts during the SOHO era, we discuss how the CME properties such as speed, width and solar-source longitude decide whether CMEs are associated with type II radio bursts and SEP events. We discuss why some radio-quiet CMEs are associated with small SEP events while some radio-loud CMEs are not associated with SEP events. We conclude that either some fast and wide CMEs do not drive shocks or they drive weak shocks that do not produce significant levels of particle acceleration. We also infer that the Alfvén speed in the corona and near-Sun interplanetary medium ranges from <200 km/s to ∼1600 km/s. Radio-quiet fast and wide CMEs are also poor SEP producers and the association rate of type II bursts and SEP events steadily increases with CME speed and width (i.e. energy). If we consider western hemispheric CMEs, the SEP association rate increases linearly from ∼30% for 800 km/s CMEs to 100% for ≥1800 km/s. Essentially all type II bursts in the decametre-hectometric (DH) wavelength range are associated with SEP events once the source location on the Sun is taken into account. This is a significant result for space weather applications, because if a CME originating from the western hemisphere is accompanied by a DH type II burst, there is a high probability that it will produce an SEP event.

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Plasma Properties in Coronal Holes Derived from Measurements of Minor Ion Spectral Lines and Polarized White Light Intensity

Cited by 178 publications

References 22 publications

Theory for Finite Temperature Effects on Magnetosonic Waves in a Two-Ion-Species Plasma

Theory for Finite Temperature Effects on Magnetosonic Waves in a Two-Ion-Species Plasma

Solar coronal-hole plasma densities and temperatures

Coronal mass ejections, type II radio bursts, and solar energetic particle events in the SOHO era

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