On Split-Band Structure in Type II Radio Bursts from the Sun

Smerd, S. F.; Sheridan, K. V.; Stewart, R. T.

doi:10.1017/s0074180900234542

Cited by 34 publications

(41 citation statements)

References 9 publications

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“…In this paper we utilize the method proposed by Smerd et al (1974Smerd et al ( , 1975. It is based on measurements of type II radio bursts, known to be excited by the coronal MHD shock waves.…”

Section: Introductionmentioning

confidence: 99%

“…Nelson & Melrose 1985). Smerd et al (1974) proposed that the band-split is associated with the density jump at the shock front, which provides an estimate of the shock Mach number. On the other hand, the shock velocity can be estimated from the frequency drift of the burst, and the ratio of the two parameters gives the Alfvén velocity.…”

Section: Introductionmentioning

confidence: 99%

“…Several reasons motivated us to perform an analysis similar to the one presented by Smerd et al (1974Smerd et al ( , 1975. First, the data set used by Smerd et al (1974Smerd et al ( , 1975 was relatively small and the procedure was not appropriate: The analysis included only 9 events with the highest observed fundamental band frequency 80 MHz, and the Mach number was evaluated using the hydrodynamic approximation (β = ∞).…”

Section: Introductionmentioning

confidence: 99%

“…First, the data set used by Smerd et al (1974Smerd et al ( , 1975 was relatively small and the procedure was not appropriate: The analysis included only 9 events with the highest observed fundamental band frequency 80 MHz, and the Mach number was evaluated using the hydrodynamic approximation (β = ∞). We have selected a two times as large a data set of 18 type II bursts embracing starting (fundamental band) frequencies up to 270 MHz, and a more detailed and more accurate analysis is performed.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Band-splitting of coronal and interplanetary type II bursts

Vršnak

Magdalenić

Auraß

et al. 2002

A&A

177

147

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Abstract. Type II radio bursts recorded in the metric wavelength range are excited by MHD shocks traveling through the solar corona. They often expose the fundamental and harmonic emission band, both frequently being split in two parallel lanes that show a similar frequency drift and intensity behaviour. Our previous paper showed that band-splitting of such characteristics is a consequence of the plasma emission from the upstream and downstream shock regions. Consequently, the split can be used to evaluate the density jump at the shock front and to estimate the shock Mach number, which in combination with the shock speed inferred from the frequency drift provides an estimate of the Alfvén velocity and the magnetic field in the ambient plasma. In this paper such a procedure is applied to 18 metric type II bursts with the fundamental band starting frequencies up to 270 MHz. The obtained values show a minimum of the Alfvén velocity at the heliocentric distance R ≈ 2 amounting to v A ≈ 400-500 km s −1 . It then increases achieving a local maximum of v A ≈ 450-700 km s −1 at R ≈ 2.5. The implications regarding the process of formation and decay of MHD shocks in the corona are discussed. The coronal magnetic field in the range 1.3 < R < 3 decreases as R −3 to R −4 , or H −1.5 to H −2 if expressed as a function of the height. The results are compared with other estimates of the coronal magnetic field in the range 1 < R < 10. Combined data show that below H < 0.3 the magnetic field is dominated by active region fields, whereas above H = 1 it becomes radial, behaving roughly as B = 2 × R −2 with a plausible value of B ≈ 5 nT at 1 a.u.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Band-splitting of coronal and interplanetary type II bursts

Vršnak

Magdalenić

Auraß

et al. 2002

A&A

177

147

View full text Add to dashboard Cite

show abstract

“…The F branch as a whole lasts for ~28 min (22 : 34-23 : 02 UT) and extends from ~140 to 10 MHz with an average drift rate of ~0.08 MHz s 1 . At 22 : 44 UT, both branches get intermittent, till 22 : 48 UT the emission becomes continuous again with a clear band splitting [150,151] on the H branch. In the meantime, the H-branch slope changes drastically at ~40 MHz with the average drift rate decreasing from ~0.4 (22 : 34-22 : 44) to ~−0.04 MHz s 1 (22 : 44-22 : 52).…”

Section: Radio Signatures Of Cme-streamer Interactionsmentioning

confidence: 99%

A review of recent studies on coronal dynamics: Streamers, coronal mass ejections, and their interactions

Chen

2013

Chin. Sci. Bull.

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In this article I present a review of recent studies on coronal dynamics, including research progresses on the physics of coronal streamers that are the largest structure in the corona, physics of coronal mass ejections (CMEs) that may cause a global disturbance to the corona, as well as physics of CME-streamer interactions. The following topics will be discussed in depth: (1) acceleration of the slow wind flowing around the streamer considering the effect of magnetic flux tube curvature; (2) physical mechanism accounting for persistent releases of streamer blobs and diagnostic results on the temporal variability of the slow wind speed with such events; (3) force balance analysis and energy release mechanism of CMEs with a flux rope magnetohydrodynamic model; (4) statistical studies on magnetic islands along the coronal-ray structure behind a CME and the first observation of magnetic island coalescence with associated electron acceleration; and (5) white light and radio manifestations of CME-streamer interactions. These studies shed new light on the physics of coronal streamers, the acceleration of the slow wind, the physics of solar eruptions, the physics of magnetic reconnection and associated electron acceleration, the large-scale coronal wave phenomenon, as well as the physics accounting for CME shock-induced type II radio bursts. solar wind, coronal streamer, coronal mass ejection, solar radio burst, magnetic reconnection Citation:Chen Y. A review of recent studies on coronal dynamics: Streamers, coronal mass ejections, and their interactions.

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Influence of the Initial Shock Speed Excited by Solar Flares on Shock Arrival Time Prediction

Hao

Chen

et al. 2011

Chinese J of Geophysics

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By using the Hakamada‐Akasofu‐Fry (HAF) solar wind model, we simulated 48 solar flare events during Carrington Rotation 1981 to 1985 and compared the simulated shock arrival time with observations by satellites at 1 AU. It is found that the initial solar wind shock speed deduced from the metric Type II radio burst observations plays an important role in the shock arrival time prediction. The match between predicted and observed shock arrival times (SATs) was considerably improved by iteratively adjusting the initial shock speed. We obtained the adjustment factors as the function of the initial shock speed for different hemispheres by using the statistical analysis and applied them to adjust the initial shock speed driven by the solar flares which occurred in the following five Carrington rotations (1986~1990), and the mean absolute error of the shock arrival time was reduced from 16 (15) hours to 12 (11) hours for the flare occurred on the western (eastern) hemisphere. This indicates that significant improvements can be made for the shock arrival time prediction by adjusting the initial shock speed using the statistical functions.

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On Split-Band Structure in Type II Radio Bursts from the Sun

Abstract: (Astrophys. Letters). The measured amount of band-splitting, Δf, in the spectra of nine harmonic type II bursts is illustrated in Figure 1. Here, as in previous, smaller samples (Roberts, 1959; Maxwell and Thompson, 1962; Weiss, 1965) Δf is found to increase with frequency, f.

Cited by 34 publications

References 9 publications

Band-splitting of coronal and interplanetary type II bursts

Band-splitting of coronal and interplanetary type II bursts

A review of recent studies on coronal dynamics: Streamers, coronal mass ejections, and their interactions

Influence of the Initial Shock Speed Excited by Solar Flares on Shock Arrival Time Prediction

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