An Estimate of the Coronal Magnetic Field Near a Solar Coronal Mass Ejection From Low-Frequency Radio Observations

Hariharan, K.; Ramesh, R.; Kishore, P.; Kathiravan, C.; Gopalswamy, Ν.

doi:10.1088/0004-637x/795/1/14

Cited by 27 publications

(18 citation statements)

References 48 publications

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“…Nevertheless, extrapolations from photospheric fields are model-dependent, static (no eruptive events) and fail to reproduce accurately complex coronal topologies. For these reasons, many different techniques have been developed to measure magnetic fields in the extended corona using radio observations and taking advantage of Faraday ro- tation (e.g., Mancuso & Spangler 1999;Mancuso & Garzelli 2013a,b) and circular polarization in radio bursts (e.g., Hariharan et al 2014), or in the lower corona with EUV images using coronal seismology (e.g., West et al 2011) and field extrapolations bounded to 3D reconstructions (e.g., Aschwanden, Sun & Liu 2014). The recent development of spectro-polarimetric measurements of magnetic field strength and orientation is now providing very promising results (Tomczyk et al 2011;Dove et al 2011, e.g.,), even if (due to the required polarimetric sensitivities) these techniques can be applied only in the lower corona (h < 0.4 R ).…”

Section: Discussionmentioning

confidence: 99%

Physical Conditions of Coronal Plasma at the Transit of a Shock Driven by a Coronal Mass Ejection

Susino

Бемпорад

Mancuso

2015

ApJ

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We report here on the determination of plasma physical parameters across a shock driven by a Coronal Mass Ejection using White Light (WL) coronagraphic images and Radio Dynamic Spectra (RDS). The event analyzed here is the spectacular eruption that occurred on June 7th 2011, a fast CME followed by the ejection of columns of chromospheric plasma, part of them falling back to the solar surface, associated with a M2.5 flare and a type-II radio burst. Images acquired by the SOHO/LASCO coronagraphs (C2 and C3) were employed to track the CME-driven shock in the corona between 2-12 R in an angular interval of about 110 • . In these intervals we derived 2-Dimensional (2D) maps of electron density, shock velocity and shock compression ratio, and we measured the shock inclination angle with respect to the radial direction. Under plausible assumptions, these quantities were used to infer 2D maps of shock Mach number M A and strength of coronal magnetic fields at the shock's heights. We found that in the early phases (2-4 R ) the whole shock surface is super-Alfvénic, while later on (i.e. higher up) it becomes super-Alfvenic only at the nose. This is in agreement with the location for the source of the observed type-II burst, as inferred from RDS combined with the shock kinematic and coronal densities derived from WL. For the first time, a coronal shock is used to derive a 2D map of the coronal magnetic field strength over a 10 R altitude and ∼ 110 • latitude intervals.

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Section: Discussionmentioning

confidence: 99%

Physical Conditions of Coronal Plasma at the Transit of a Shock Driven by a Coronal Mass Ejection

Susino

Бемпорад

Mancuso

2015

ApJ

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“…Imaging these bursts provides important information such as the magnetic field in the ambient medium (Hariharan et al 2014). These bursts indicate the height of shock formation in the corona as evidenced by EUV shocks and Moreton waves (see e.g., Asai et al 2012aAsai et al , 2012b.…”

Section: Shocks Inferred From Radio Observationsmentioning

confidence: 99%

Short-term variability of the Sun-Earth system: an overview of progress made during the CAWSES-II period

Gopalswamy

Tsurutani

Yan

2015

Prog. in Earth and Planet. Sci.

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This paper presents an overview of results obtained during the CAWSES-II period on the short-term variability of the Sun and how it affects the near-Earth space environment. CAWSES-II was planned to examine the behavior of the solar-terrestrial system as the solar activity climbed to its maximum phase in solar cycle 24. After a deep minimum following cycle 23, the Sun climbed to a very weak maximum in terms of the sunspot number in cycle 24 (MiniMax24), so many of the results presented here refer to this weak activity in comparison with cycle 23. The short-term variability that has immediate consequence to Earth and geospace manifests as solar eruptions from closed-field regions and high-speed streams from coronal holes. Both electromagnetic (flares) and mass emissions (coronal mass ejections -CMEs) are involved in solar eruptions, while coronal holes result in high-speed streams that collide with slow wind forming the so-called corotating interaction regions (CIRs). Fast CMEs affect Earth via leading shocks accelerating energetic particles and creating large geomagnetic storms. CIRs and their trailing high-speed streams (HSSs), on the other hand, are responsible for recurrent small geomagnetic storms and extended days of auroral zone activity, respectively. The latter leads to the acceleration of relativistic magnetospheric 'killer' electrons. One of the major consequences of the weak solar activity is the altered physical state of the heliosphere that has serious implications for the shock-driving and storm-causing properties of CMEs. Finally, a discussion is presented on extreme space weather events prompted by the 23 July 2012 super storm event that occurred on the backside of the Sun. Many of these studies were enabled by the simultaneous availability of remote sensing and in situ observations from multiple vantage points with respect to the Sun-Earth line.

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“…Stokes I, alone (Smerd, Sheridan, and Stewart, 1975;Gopalswamy and Kundu, 1990;Bastian et al, 2001;Vršnak et al, 2002;Mancuso et al, 2003;Cho et al, 2007;Kishore et al, 2016) or both the total and circularly polarized intensities, i.e. Stokes I and V (Dulk and Suzuki, 1980;Gary et al, 1985;Ramesh et al, 2010a;Ramesh, Kathiravan, and Narayanan, 2011;Tun and Vourlidas, 2013;Sasikumar Raja and Ramesh, 2013;Hariharan et al, 2014;2016b;Anshu et al, 2017). Note that we have mentioned only Stokes I and V emission here since differential Faraday rotation of the plane of polarization in the solar corona and Earth's ionosphere makes it impossible to observe the linear polarization (represented by Stokes Q and U ) within the typical observing bandwidths of ≈ 100 kHz (see for example Grognard and McLean, 1973.)…”

Section: Introductionmentioning

confidence: 99%

Strength of the Solar Coronal Magnetic Field – A Comparison of Independent Estimates Using Contemporaneous Radio and White-Light Observations

et al. 2017

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We estimated the coronal magnetic field strength (B) during the 23 July 2016 coronal mass ejection (CME) event using i) the flux rope structure of the CME in the whitelight coronagraph images and ii) the band splitting in the associated type II burst. No models were assumed for the coronal electron density (N (r)) used in the estimation. The results obtained using the above two independent methods correspond to different heliocentric distances (r) in the range ≈ 2.5 -4.5R ⊙ , but they show excellent consistency and could be fitted with a single power-law distribution of the type B(r) = 5.7r −2.6 G, which is applicable in the aforementioned distance range. The power law index (i.e. −2.6) is in good agreement with the results obtained in previous studies by different methods.

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An Estimate of the Coronal Magnetic Field Near a Solar Coronal Mass Ejection From Low-Frequency Radio Observations

Cited by 27 publications

References 48 publications

Physical Conditions of Coronal Plasma at the Transit of a Shock Driven by a Coronal Mass Ejection

Physical Conditions of Coronal Plasma at the Transit of a Shock Driven by a Coronal Mass Ejection

Short-term variability of the Sun-Earth system: an overview of progress made during the CAWSES-II period

Strength of the Solar Coronal Magnetic Field – A Comparison of Independent Estimates Using Contemporaneous Radio and White-Light Observations

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