Coronal Radio Occultation Experiments with the Helios Solar Probes: Correlation/Spectral Analysis of Faraday Rotation Fluctuations

Ефимов, А. И.; Луканина, Л. А.; Rogashkova, A. I.; Samoznaev, L. N.; Чашей, И. В.; Bird, M. K.; Pätzold, M.

doi:10.1007/s11207-015-0687-y

Cited by 11 publications

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References 11 publications

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“…Our work demonstrates low‐frequency FR fluctuations in the lower corona but does not prove the existence of propagating waves since we had only single‐station observations. FR studies using two‐station temporal cross correlations did show evidence for wave propagation [ Bird , ; Efimov et al ., ; Jensen and Rusell , ]. Below the Alfvén critical point, where the Alfvén speed exceeds the solar wind speed, the two‐station data indicated propagation sometimes toward but mostly away from the Sun.…”

Section: Discussionmentioning

confidence: 97%

“…The FRF power spectrum (Figures and ) showed a power law form similar to that found in the HELIOS studies [ Efimov et al ., ; Bird , ; Efimov et al ., ]. We found it useful to separate the data analysis frame with the transient event from those showing only the general background fluctuation spectrum.…”

Section: Discussionmentioning

confidence: 99%

“…Recent reviews by Efimov et al . [, ] illustrate a broad range of FRF frequencies, from milliHertz (mHz) scales extending into the sub‐mHz range.…”

Section: Introductionmentioning

confidence: 99%

“…Lowfrequency FR fluctuations with time scales up to hours are believed to represent Alfvén waves [Hollweg et al, 1982] and have been implicated in the overall process of energy transport required for heating and acceleration of the solar wind [Chashei, 1989;Hollweg et al, 2010]. Recent reviews by Efimov et al [2015aEfimov et al [ , 2015b illustrate a broad range of FRF frequencies, from milliHertz (mHz) scales extending into the sub-mHz range.…”

Section: Introductionmentioning

confidence: 99%

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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: Discussionmentioning

confidence: 97%

Section: Discussionmentioning

confidence: 99%

“…Recent reviews by Efimov et al . [, ] illustrate a broad range of FRF frequencies, from milliHertz (mHz) scales extending into the sub‐mHz range.…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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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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“…Examples of results which have been obtained with spacecraft transmitters are Stelzried et al (1970), Hollweg et al (1982), Pätzold et al (1987), Bird & Edenhofer (1990), Andreev et al (1997), Jensen et al (2013a,b), and Efimov et al (2015).…”

Section: Losmentioning

confidence: 99%

VLA Measurements of Faraday Rotation through Coronal Mass Ejections

et al. 2017

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Coronal mass ejections (CMEs) are large-scale eruptions of plasma from the Sun that play an important role in space weather. Faraday rotation (FR) is the rotation of the plane of polarization that results when a linearly polarized signal passes through a magnetized plasma such as a CME and is proportional to the path integral through the plasma of the electron density and the line of sight component of the magnetic field.FR observations of a source near the Sun can provide information on the plasma structure of a CME shortly after launch; however, separating the contribution of the plasma density from the line of sight magnetic field is challenging.We report on simultaneous white-light and radio observations made of three CMEs in August 2012. We made sensitive Very Large Array (VLA) full-polarization observations using 1 − 2 GHz frequencies of a "constellation" of radio sources through the solar corona at heliocentric distances that ranged from 6 − 15R ⊙ . Of the nine sources observed, three were occulted by CMEs: two sources (0842+1835 and 0900+1832) were occulted by a single CME and one source (0843+1547) was occulted by two CMEs. In addition to our radioastronomical observations, which represent one of the first active hunts for CME Faraday rotation since Bird et al. (2007) and Jensen & Russell (2008), as well as previous CME FR observations by Bird et al. (1985).

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Properties of the Circumsolar Plasma Turbulence and Plasma Waves According to the Coronal Sounding Experiments Using Spacecraft Signals

Yakovlev

2017

Radiophys Quantum El

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Coronal Radio Occultation Experiments with the Helios Solar Probes: Correlation/Spectral Analysis of Faraday Rotation Fluctuations

Cited by 11 publications

References 11 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

VLA Measurements of Faraday Rotation through Coronal Mass Ejections

Properties of the Circumsolar Plasma Turbulence and Plasma Waves According to the Coronal Sounding Experiments Using Spacecraft Signals

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