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Чашей, И. В.; Bird, M. K.; Ефимов, А. И.; Andreev, V. E.; Samoznaev, L. N.

doi:10.1023/a:1005223531849

Cited by 28 publications

(16 citation statements)

References 3 publications

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“…The transient event seen in the first part of the data contained narrow-band spectral enhancement with peaks at 3.3 and 6.1 mHz (Figures 6a and 6b). The 3.3 mHz peak corresponds to intermittent quasi-harmonic oscillations of~5 min period reported by Efimov et al [2000] and Chashei et al [1999] for FRF observations beyond 3 R ⊙ . The finding of augmented power at~6 mHz is interesting because it might indicate MHD wave harmonics.…”

Section: Space Weathermentioning

confidence: 51%

“…Spectral analysis was also used to search for quasiperiodic fluctuations appearing as peaks superimposed upon the general power spectrum. Waves of period~5 min (3-3.5 mHz) were of particular interest due to prior descriptions of this periodicity in both EUV studies at the coronal base and transition regions [e.g., Tomczyk et al, 2007;McIntosh et al, 2011], and in coronal FR studies beyond 3R ⊙ [Chashei et al, 1999;Efimov et al, 2000].…”

Section: Data Processingmentioning

confidence: 99%

“…The extensive data sets from the HELIOS 1 (1974( -84) and HELIOS 2 (1976( -1980 spacecraft were used to study coronal FR, the first set for large-scale coronal magnetic field structure [Pätzold et al, 1987] and both sets for detailed analysis of FR fluctuations (FRFs) in transcoronal radio sounding experiments [Efimov et al,1993;Chashei et al, 2000;Bird, 2007]. Chashei et al [1999] and Efimov et al [2000] described intermittent segments of quasi-harmonic FRF along with power spectral wave-scale organization generally consistent with the energy cascade concept. One particularly interesting feature was the presence of 5 min wave-like oscillations in FR that appeared in up to 25% of the recordings obtained at heliocentric solar offsets above 3R ⊙ .…”

Section: Introductionmentioning

confidence: 98%

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Faraday rotation fluctuations of MESSENGER radio signals through the equatorial lower corona near solar minimum

et al. 2017

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Faraday rotation (FR) of transcoronal radio transmissions from spacecraft near superior conjunction enables study of the temporal variations in coronal plasma density, velocity, and magnetic field. The MESSENGER spacecraft 8.4 GHz radio, transmitting through the corona with closest line‐of‐sight approach 1.63–1.89 solar radii and near‐equatorial heliolatitudes, was recorded soon after the deep solar minimum of solar cycle 23. During egress from superior conjunction, FR gradually decreased, and an overlay of wave‐like FR fluctuations (FRFs) with periods of hundreds to thousands of seconds was found. The FRF power spectrum was characterized by a power law relation, with the baseline spectral index being −2.64. A transient power increase showed relative flattening of the spectrum and bands of enhanced spectral power at 3.3 mHz and 6.1 mHz. Our results confirm the presence of coronal FRF similar to those described previously at greater solar offset. Interpreted as Alfvén waves crossing the line of sight radially near the proximate point, low‐frequency FRF convey an energy flux density higher than that of the background solar wind kinetic energy, but only a fraction of that required to accelerate the solar wind. Even so, this fraction is quite variable and potentially escalates to energetically significant values with relatively modest changes in estimated magnetic field strength and electron concentration. Given the uncertainties in these key parameters, as well as in solar wind properties close to the Sun at low heliolatitudes, we cannot yet confidently assign the quantitative role for Alfvén wave energy from this region in driving the slow solar wind.

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Section: Space Weathermentioning

confidence: 51%

Section: Data Processingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

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Faraday rotation fluctuations of MESSENGER radio signals through the equatorial lower corona near solar minimum

et al. 2017

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“…However, unlike the in situ data and much of the radio data, Ulrich's fluctuations were mainly in the 5-minute band. In this context, it is interesting to note that Chashei et al (1999) have provided observations of Faraday rotation fluctuations (due to magnetic field fluctuations which are believed to be associated with Alfvén waves) of radio signals propagating through the corona in the acceleration region of the solar wind; there is evidence of a peak at periods around 5 minutes, in an otherwise broad power spectrum. Might the putative turbulent cascade originate from waves with periods of the order of 5 minutes, rather than hours?…”

Section: Whence the Ion-cyclotron Waves?mentioning

confidence: 99%

The solar wind: Our current understanding and how we got here

Hollweg

2008

J Astrophys Astron

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In the original theory for the solar wind, the electron pressure gradient was the principal accelerating force. This was soon recognized to be insufficient to drive the high-speed streams. Subsequently, the discovery of Alfvén waves in the solar wind led to a long series of models in which wave pressure provided additional acceleration, but these wavedriven models ultimately failed to explain the rapid acceleration of the fast wind close to the Sun. An alternate view was that the pressure of hot protons close to the Sun could explain the rapid acceleration, with the proton heating coming from the cyclotron resonance. SOHO has provided remarkable data which have verified some of the predictions of this view, and given impetus to ongoing studies of the ion-cyclotron resonance in the fast wind. After a historical review, we discuss the basic ideas behind current research, emphasizing the importance of particle kinetics. We conclude with some guesses as to how work might proceed in the future.

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“…Joint coronagraph observations are needed to determine whether an FR transient is caused by CMEs. Subsequent FR observations by the Pioneer and Helios spacecraft reveal important information on the quiet coronal field (Stelzried et al 1970;Pätzold et al 1987) and magnetic fluctuations (Hollweg et al 1982;Efimov et al 1996;Andreev et al 1997;Chashei et al 1999Chashei et al , 2000. FR fluctuations are currently the only source of information for the coronal field fluctuations.…”

Section: Introductionmentioning

confidence: 99%

Determining the Magnetic Field Orientation of Coronal Mass Ejections from Faraday Rotation

Liu

Manchester

Kasper

et al. 2007

ApJ

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We describe a method to measure the magnetic field orientation of coronal mass ejections (CMEs) using Faraday rotation (FR). Two basic FR profiles, Gaussian-shaped with a single polarity or "N"-like with polarity reversals, are produced by a radio source occulted by a moving flux rope depending on its orientation. These curves are consistent with the Helios observations, providing evidence for the flux-rope geometry of CMEs. Many background radio sources can map CMEs in FR onto the sky. We demonstrate with a simple flux rope that the magnetic field orientation and helicity of the flux rope can be determined 2-3 days before it reaches Earth, which is of crucial importance for space weather forecasting. An FR calculation based on global magnetohydrodynamic (MHD) simulations of CMEs in a background heliosphere shows that FR mapping can also resolve a CME geometry curved back to the Sun. We discuss implementation of the method using data from the Mileura Widefield Array (MWA).

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Cited by 28 publications

References 3 publications

Faraday rotation fluctuations of MESSENGER radio signals through the equatorial lower corona near solar minimum

Faraday rotation fluctuations of MESSENGER radio signals through the equatorial lower corona near solar minimum

The solar wind: Our current understanding and how we got here

Determining the Magnetic Field Orientation of Coronal Mass Ejections from Faraday Rotation

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