The Solar Corona in Interplanetary Space

Hewish, A.; Wyndham, John

doi:10.1093/mnras/126.5.469

Cited by 47 publications

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“…Interplanetary space is known to be inhomogeneous and variable with time. "Blast waves" (12) occur, and the distribution of the gas is very "lumpy" (13). The temperature of the gas is also variable (14).…”

Section: Charge On Interplanetary Dustmentioning

confidence: 99%

Dynamics of Interplanetary Dust

Belton

1966

Science

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The solar wind and its magnetic field complica the study of dust in the solar systei Michael J. S. BellCosmic dust plays an important role in theoretical and observational astrophysics. It is apparently an important factor in the process of star formation. The polarization of starlight which is induced by aligned particles of interstellar dust gives information about the magnetic field in galactic systems, including our own. Through its wavelength-dependent extinction properties, it introduces uncertainties in the measurement of stellar distances and colors. In the solar system the presence of dust in a planetary atmosphere may lead to misinterpretations of photometric and polarimetric data that would otherwise give important information about the total mass of the atmosphere (1). And finally, dust is responsible for such interplanetary phenomena as the F corona, zodiacal light, gegenschein, and type-II comet tails.With the advent of manned and unmanned space probes, there has been new interest in the properties of cosmic and, in particular, interplanetary dust particles in the vicinity of the asteroid belt. In order to design a system which will have a reasonable chance of completing a mission, the space engineer must have as complete SCIENCE, VOL. 151

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Section: Charge On Interplanetary Dustmentioning

confidence: 99%

Dynamics of Interplanetary Dust

Belton

1966

Science

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“…In this work, we will use interferometric observations of the Crab nebula to infer the spectral level of solar wind density turbulence and the density modulation index as a function of heliocentric distance. Crab occultation is a very well established technique that has been in use since the 1950s [Hewish, 1957[Hewish, , 1958Hewish and Wyndham, 1963;Erickson, 1964;Sastry and Subramanian, 1974], giving us the advantage of a standard observational quantity to draw inferences from. The schematic diagram of the occultation is shown in Figure 1.…”

Section: Introductionmentioning

confidence: 99%

“…We have used Crab occultation observations made in 2011 and 2013 at the Gauribidanur observatory [Ramesh, 2011], together with published data from several earlier observations by Machin and Smith [1952]; Hewish [1957Hewish [ , 1958; Hewish and Wyndham [1963]…”

Section: Introductionmentioning

confidence: 99%

Amplitude of solar wind density turbulence from 10 to 45 R_⊙

et al. 2016

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We report on the amplitude of the density turbulence spectrum ( CN2) and the density modulation index (δN/N) in the solar wind between 10 and 45R⊙. We derive these quantities using a structure function that is observationally constrained by occultation observations of the Crab nebula made in 2011 and 2013 and similar observations published earlier. We use the most general form of the structure function, together with currently used prescriptions for the inner/dissipation scale of the turbulence spectrum. Our work yields a comprehensive picture (a) of the manner in which CN2 and δN/N vary with heliocentric distance in the solar wind and (b) of the solar cycle dependence of these quantities.

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“…2 Evidence for Non-Force-Free Flux Tubes in the Solar Corona Filamentary density contrast of diameter 30 Mm has been recognized historically in different solar coronal observations as with polar plumes, but with suggestions of much finer structures (Newkirk 1967). Hewish & Wyndham (1963) identified fine elongated approximately radial density contrast smaller than 5 Mm in the solar corona and interplanetary medium around 60R ⊙ from radio scintillation measurements. The scintillation spectrum extends to much finer scales in the interpretation of multiple baseline measurements, suggesting an inner scale of turbulence of about 1 km at 5R ⊙ that increases to about 100 km near 100R ⊙ (Coles & Harmon 1989).…”

Section: Introductionmentioning

confidence: 98%

The Astrophysical Corona as the Minimum Atmosphere Surrounding Embedded Non-Force-Free Flux Tubes

November¹

2019

Preprint

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The equilibrium of current-carrying magnetic fields (e.g. flux tubes) embedded in a large-scale background field is developed and discussed in the astrophysical context. Embedded non-force-free current-carrying fields require a minimum surrounding atmosphere, which by direct pressure balance has a gas pressure everywhere proportional to the background magnetic pressure. Formally, the MHD equations, with flows and gravity as part of a wide class of physical processes, separate into independent local and global relations representing an equilibrium solution for embedded current-carrying fields. The local pressure relation for the embedded field is a 3D Grad-Shafranov equation with finite-sheath solutions. The global relation reproduces the ambient MHD pressure equation without the embedded fields, but instead with the constraint that the ambient gas and magnetic pressures vary in proportion, as with the direct pressure balance. A coupled gas pressure in magnetically dominant regimes necessitates refilling outflows in a depleted atmosphere (actualized by flux-tube Lorentz forces) providing a compressively heated equilibrium corona with a specific global distribution of density, temperature, and steady accelerated outflow, all defined by the large-scale background magnetic field. Magnetic footpoint compression and twisting in a high-gas-pressure field-forming region (e.g. convection zone) outside, as below, the magnetically dominant regime, can introduce and sustain non-force-free embedded fields, thereby providing the energy for the coronal atmosphere. Such coronae may be relevant on very different astrophysical scales: around the sun and stars, and ranging from planets, to neutron stars, black holes, and spiral galaxies. Predicted coronal temperatures are corroborated.

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The Solar Corona in Interplanetary Space

Cited by 47 publications

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Dynamics of Interplanetary Dust

Dynamics of Interplanetary Dust

Amplitude of solar wind density turbulence from 10 to 45 R_⊙

The Astrophysical Corona as the Minimum Atmosphere Surrounding Embedded Non-Force-Free Flux Tubes

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The Solar Corona in Interplanetary Space

Cited by 47 publications

References 0 publications

Dynamics of Interplanetary Dust

Dynamics of Interplanetary Dust

Amplitude of solar wind density turbulence from 10 to 45 R⊙

The Astrophysical Corona as the Minimum Atmosphere Surrounding Embedded Non-Force-Free Flux Tubes

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Amplitude of solar wind density turbulence from 10 to 45 R_⊙