Fine and Superfine Structure of the Decameter–Hectometer Type II Burst on 7 June 2011

Dorovskyy, V. V.; Melnik, V. N.; Konovalenko, A. A.; Браженко, А. И.; Panchenko, M.; Poedts, Stefaan; Mykhaylov, Valeriy

doi:10.1007/s11207-015-0725-9

Cited by 21 publications

(31 citation statements)

References 30 publications

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“…Hence, coronagraphic images acquired by the STEREO coronagraphs would not provide any useful information about the corona lying on the meridional plane at 66 • W. Said that, although we assume that no significant temporal and longitudinal variations are present between the density profile we inferred on the plane of the sky and the density really met by the shock, this assumption is undoubtedly much more realistic with respect to the one that involves the adoption of a generic power-law density profile, as usually done in the literature for this kind of studies (see e.g. Pohjolainen & Lehtinen 2006;Liu et al 2009;Kong et al 2015;Dorovskyy et al 2015).…”

Section: Radio Dynamic Specrummentioning

confidence: 89%

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: Radio Dynamic Specrummentioning

confidence: 89%

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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“…The fine structures discussed here show the same spectral morphology, that is, a thorn-like shape (or in other words a head-tail structure). − HBs exhibit a pronounced circular polarization (Stewart & Magun 1980;Suzuki et al 1982;Cairns & Robinson 1987;Dorovskyy et al 2015). The fundamental radiation of HBs is usually more circularly polarized than the harmonic one (Cairns & Robinson 1987).…”

Section: Introductionmentioning

confidence: 99%

Radio signatures of shock-accelerated electron beams in the solar corona

Mann

Melnik

Rücker

et al. 2018

A&A

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Context. The Sun’s activity can appear in terms of radio bursts. In the frequency range 8−33 MHz the radio telescope URAN-2 observed special fine structures appearing as a chain of stripes of enhanced radio emission in the dynamic radio spectrum. The chain drifts slowly from 26 to 23 MHz within 4 min. The individual structures consist of a “head” at the high-frequency edge and a “tail” rapidly drifting from the “head” to lower frequencies over an extent of ≈10 MHz within 8 s. Since they resemble the well-known “herring bones” in type II radio bursts, they are interpreted as shock accelerated electron beams. Aims. The electron beams generating these fine structures are considered to be produced by shock drift acceleration (SDA). The beam electrons excite Langmuir waves which are converted into radio waves by nonlinear wave-plasma processes. That is called plasma emission. The aim of this paper is to link the radio spectral data of these fine structures to the theoretical results in order to gain a better understanding of the generation of energetic electrons by shocks in the solar corona. Methods. Adopting SDA for generating energetic electrons, the accelerated electrons establish a beam-like velocity distribution. Plasma emission requires the excitation of Langmuir waves, which is efficient if the velocity of the beam electrons exceeds a few times thermal electron speed. That is the case if the angle between the shock normal and the upstream magnetic field is nearly perpendicular. Hence, the Rankine-Hugoniot relationships, which describe the shock transition in the framework of magnetohydrodynamics, are evaluated for the special case of nearly perpendicular shocks under coronal circumstances. Results. The radio data deduced from the dynamic radio spectrum can be related in the best way to the theoretical results, if the electron beams, which generate these fine structures, are generated via SDA at an almost perpendicular shock, which is traveling nearly horizontally to the surface of the Sun.

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“…Однако, кроме получения параметров Стокса, нам нужно выполнить еще одну операцию, связанную со сдвигом фазы сигнала гетеродинаподавление боковой полосы частот [https://www.analog.com/ru/analogdialogue/articles/mirror-mirror-on-the-wall-understandingimage-rejection-and-its-impact-on-desired-signals.html]. Если возможностей чипа AD9361 по манипуляции фазами будет недостаточно для реализации одновременно этих двух задач, остается резервный вариантполучение Iи V-параметров Стокса в цифровом виде в ПЛИС [Das et al, 2010].…”

Section: возможность применения Sdr в спектрополяриметрах метрового дunclassified

Solar Spectropolarimeter for Space Weather Forecast

Ivanov

Gubin

Lesovoi

et al. 2019

Solnechno-Zemnaya Fizika

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We propose a project of the meter wavelength range solar spectropolarimeter designed for a ground-based network developing for space weather forecast. The Software-Defined Radio (SDR) solution is chosen to meet such instrument network requirements as specification identity, low cost, possibility of controlling and transmitting data remotely via the Internet. Along with these requirements, the proposed SDR solution allows us to measure Stokes I and V easily, which contrasts the proposed instrument with e-CALLISTO network spectropolarimeters, most of which can record only one linear polarization. Deployment of such instruments at various longitudes will allow continuous observation of type II bursts, often related to coronal mass ejections (CMEs) — the most geoeffective solar activity events that affect the space weather significantly.

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Fine and Superfine Structure of the Decameter–Hectometer Type II Burst on 7 June 2011

Cited by 21 publications

References 30 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

Radio signatures of shock-accelerated electron beams in the solar corona

Solar Spectropolarimeter for Space Weather Forecast

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