Solar wind electrons: Vela 4 measurements

Montgomery, M. D.; Bame, S. J.; Hundhausen, A. J.

doi:10.1029/ja073i015p04999

Cited by 316 publications

(147 citation statements)

References 6 publications

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“…On the other hand, both the strahl n and halo n have no association with the solar wind core population, while the halo n strongly correlates with the strahl n. These results support the idea that the strahl/halo have a different origin from the solar wind core: the strahl could originate from the Sun, e.g., due to the escaping electrons from the hot corona, while the halo may be due to some processes (e.g., scattering) acting on the strahl in the IPM (e.g., Montgomery et al 1968;Feldman et al 1975;Rosenbauer et al 1977;Pilipp et al 1987;Pierrard et al 2001). For the 0.1-1.5 keV strahl electrons at quiet times, κ ranges from 4.3 to 15.3 (from 4.6 to 16.6) in solar cycle 23 (24), anticorrelated with the sunspot number (see Figure 7).…”

Section: Summary and Discussionsupporting

confidence: 75%

“…The highly anisotropic strahl could result from the escape of thermal electrons from the hot (∼10 6 K) solar corona (e.g., Feldman et al 1975;Salem et al 2007) that carries heat flux outward, while the isotropic halo may be due to the scattering of the strahl in the interplanetary medium (IPM; e.g., Montgomery et al 1968;Feldman et al 1975;Rosenbauer et al 1977;Pilipp et al 1987;Pierrard et al 2001). Combining the measurements from the Helios, WIND, and Ulysses spacecraft, Maksimovic et al (2005) and Stverak et al (2009) reported that the relative halo (strahl) number density to the total electron density increases (decreases) with the heliocentric distance, while the relative core density remains roughly constant, supporting the above scenarios.…”

Section: Introductionmentioning

confidence: 99%

“…The solar wind electrons observed near 1 au consist of three components: a thermal (∼10 eV) Maxwellian core that contains ∼90%-95% of the plasma density, a much hotter (∼50-80 eV) halo/strahl that contains ∼5%-10% of the plasma density (e.g., Montgomery et al 1968;Vasyliunas 1968;Feldman et al 1975;Rosenbauer et al 1977;Pilipp et al 1987;Maksimovic et al 2005;Zouganelis 2008), and a power-law ( µ b -J E with b~2.4) superhalo at energies above ∼2 keV (Lin 1998;Wang et al 2012;Yang et al 2015). The halo population is observed to have a Maxwellian/Kappa spectrum and isotropic angular distribution.…”

Section: Introductionmentioning

confidence: 99%

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QUIET-TIME SUPRATHERMAL (∼0.1–1.5 keV) ELECTRONS IN THE SOLAR WIND

Tao

Wang

Zong

et al. 2016

ApJ

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We present a statistical survey of the energy spectrum of solar wind suprathermal (∼0.1-1.5 keV) electrons measured by the WIND3DP instrument at 1 AU during quiet times at the minimum and maximum of solar cycles 23 and 24. After separating (beaming) strahl electrons from (isotropic) halo electrons according to their different behaviors in the angular distribution, we fit the observed energy spectrum of both strahl and halo electrons at ∼0.1-1.5 keV to a Kappa distribution function with an index κ and effective temperature T eff . We also calculate the number density n and average energy E avg of strahl and halo electrons by integrating the electron measurements between ∼0.1 and 1.5 keV. We find a strong positive correlation between κ and T eff for both strahl and halo electrons, and a strong positive correlation between the strahl n and halo n, likely reflecting the nature of the generation of these suprathermal electrons. In both solar cycles, κ is larger at solar minimum than at solar maximum for both strahl and halo electrons. The halo κ is generally smaller than the strahl κ (except during the solar minimum of cycle 23). The strahl n is larger at solar maximum, but the halo n shows no difference between solar minimum and maximum. Both the strahl n and halo n have no clear association with the solar wind core population, but the density ratio between the strahl and halo roughly anti-correlates (correlates) with the solar wind density (velocity).

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Section: Summary and Discussionsupporting

confidence: 75%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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QUIET-TIME SUPRATHERMAL (∼0.1–1.5 keV) ELECTRONS IN THE SOLAR WIND

Tao

Wang

Zong

et al. 2016

ApJ

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“…Twenty hours of data sampled over a 2 month observation period suggested the basic characteristics of solar wind electron behavior [Montgomery et al, 1968]. Electron temperatures Te were observed over a range of 70,000-200,000 K, which were 1.5-5 times the prevailing proton temperatures…”

Section: Introduction Parts They Can Be Drastically Affected By a Spmentioning

confidence: 99%

Electron temperature in the ambient solar wind: Typical properties and a lower bound at 1 AU

Newbury¹,

Russell²,

Phillips³

et al. 1998

J. Geophys. Res.

134

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Abstract. Our understanding of what controls the solar wind electron temperature is far from complete. Previous studies from the Vela and IMP spacecraft have suggested that twice the proton temperature or an assumed average of • 150,000 K are reasonable estimations of total electron temperature at 1 AU. Eighteen months of continuous ISEE 3 solar wind data are analyzed in this paper and are found to have a mean electron temperature of 141,000 4-38,000 K, in good agreement with past measurements. No correlation is found between electron temperature and other solar wind parameters, including proton temperature. However, a very distinct lower bound on the electron temperature is found; this bound increases with proton temperature and is observed by both ISEE 3 and Ulysses spacecraft. The bound is also found to vary with bulk solar speed of the solar wind and with distance from the Sun. Solar wind plasma observed following stream interactions are often associated with temperatures near this bound, and enhanced electromagnetic wave activity in the 18-100 Hz range is coincident with intervals where this apparent temperature coupling is observed, suggesting the possible presence of wave-particle interactions. Possible explanations for the existence of this electron temperature bound are explored, but no definitive answer has been found at this time.

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“…This heat flux should be compared with the corrected value (Q -1-3x 10 -2 erg/cm 2 sec) obtained observationally by Montgomery et al (1968). However, using the N 2 /N p = 0 contour in Figure 1, one would have obtained (-g ecp 0/xT I ) = 1.094 or ( p 0 1 1.3 V ;-Qf.…”

Section: Two-component Electron Exospherementioning

confidence: 99%