High resolution VLA-Nancay observations of the sun

Kerdraon, A.; Lang, Kenneth R.; Trottet, G.; Willson, R. F.

doi:10.1016/0273-1177(88)90294-3

Cited by 2 publications

(3 citation statements)

References 5 publications

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“…4.1. Internal structure of noise storms at a single frequency Kerdraon et al (1988) observed two bursts at different positions and times but without relating them to the overall storm structure. Lang and Willson (1987), from data integrated over one hour, found evidence of fine structure involving several compact sources embedded in a more extended source.…”

Section: Discussionmentioning

confidence: 99%

“…Zlobec et al (1992) reported sizes ∼ 50 arcsec for about 20 bursts, with a minimum reliable value of 40 arcsec for two of them. Kerdraon et al (1988) also reported two bursts with size of 40 arsec. In our study, the main noise storm on Aug. 27, 2002 has a nearly stable size in the 224 images during the whole observation of 1 hour, with a minimum of 31 arcsec.…”

Section: Apparent Sizes Of Noise Storm Coresmentioning

confidence: 92%

“…However, the time resolution was only 13 and 30 s and the dynamical range in images was limited by the small number (12) of the antennas used. Kerdraon et al (1988) presented images of two bursts occuring at different times during a storm, with typical sizes of 45 arcsec and positions separated by ∼ 50 arcsec, one being polarized and the other unpolarized. Zlobec et al (1992) attempted to derive the smallest spatial scales involved in noise storms.…”

Section: Introductionmentioning

confidence: 99%

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The structure of solar radio noise storms

Mercier

Subramanian

Chambe

et al. 2015

A&A

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Context. The Nançay Radioheliograph (NRH) routinely produces snapshot images of the full sun (field of view ∼3 R ) at 6 or 10 frequencies between 150 and 450 MHz, with typical resolution 3 arcmin and time cadence 0.2 s. Combining visibilities from the NRH and from the Giant Meterwave Radio Telescope (GMRT) allows us to produce images of the sun at 236 or 327 MHz, with the same field as the NRH, a resolution as low as 20 arcsec, and a time cadence 2 s. Aims. We seek to investigate the structure of noise storms (the most common non-thermal solar radio emission) which is yet poorly known. We focus on the relation of position and altitude of noise storms with the observing frequency and on the lower limit of their sizes. Methods. We use an improved version of a previously used method for combining NRH and GMRT visibilities to get high-resolution composite images and to investigate the fine structure of noise storms. We also use the NRH data over several consecutive days around the common observation days to derive the altitude of storms at different frequencies.Results. We present results for noise storms on four days. Noise storms consist of an extended halo and of one or several compact cores with relative intensity changing over a few seconds. We found that core sizes can be almost stable over one hour, with a minimum in the range 31-35 arcsec (less than previously reported). The heliocentric distances of noise storms are ∼1.20 and 1.35 R at 432 and 150 MHz, respectively. Regions where storms originate are thus much denser than the ambient corona and their vertical extent is found to be less than expected from hydrostatic equilibrium. Conclusions. The smallest observed sizes impose upper limits on broadening effects due to scattering on density inhomogeneities in the low and medium corona and constrain the level of density turbulence in the solar corona. It is possible that scatter broadening has been overestimated in the past, and that the observed sizes cannot only be attributed to scattering. The vertical structure of the noise storms is difficult to reconcile with the classical columnar model.

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Section: Discussionmentioning

confidence: 99%

Section: Apparent Sizes Of Noise Storm Coresmentioning

confidence: 92%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

The structure of solar radio noise storms

Mercier

Subramanian

Chambe

et al. 2015

A&A

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VLA and Trieste observations of type I storms, type IV and pulsations

et al. 1992

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A prime objective of this experiment was to determine whether type I or IV sources at 333 MHz contain features of small (arc sec) scale. With the VLA, our resolution was better than 4". However, we never observed any structure of size smaller than about 30", with the typical source sizes being between about 40" and 90".Many observations were simultaneous with the Trieste Astronomical Observatory records at 327 MHz. The observations were made on two days in November 1988. On 8 November the observations were of a type I storm about two hours after a major flare. On 14 November they were mostly of the main phase of a type IV event, including pulsations of a kind rarely seen, strongly circularly polarized, and having a well-defined period of about 12 s. The size of the pulsating source was about 40" by 60", and the brightness temperature was about 109 K. We compare these pulsations with those observed earlier.

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High resolution VLA-Nancay observations of the sun

Cited by 2 publications

References 5 publications

The structure of solar radio noise storms

The structure of solar radio noise storms

VLA and Trieste observations of type I storms, type IV and pulsations

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