Radio observations of PKS2314 + 03 during occultation by comet Halley

Alurkar, S. K.; Bhonsle, R. V.; Sharma, A. K.

doi:10.1038/322439a0

Cited by 14 publications

(14 citation statements)

References 11 publications

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“…It is interesting to compare the present results with the earlier reports of both detections and nondetections of enhanced scintillation. The range of values of the normalized plasma turbulence from similar observations spread over almost an order of magnitude (Alurkar et al 1986;Slee et al 1987Slee et al , 1990Ananthakrishnan et al 1987) for a given set of parameters (e.g., , ). In addition to that, the tur-L n c e c bulence level is likely to change systematically with the distance from the nucleus of the comet along the plasma tail axis.…”

Section: Observations and Resultsmentioning

confidence: 97%

“…When a comet plasma tail intersects the radio path, the electron density irregularities associated with the comet can cause an enhancement in the level of scintillation. Several attempts have been made to estimate the turbulence associated with the cometary plasma by observing the occultation of the radio source by the tail of the comet (Ananthakrishnan et al 1975(Ananthakrishnan et al , 1987Alurkar et al 1986Alurkar et al , 1989Slee et al 1987;Hajivassiliou & Duffett-Smith 1987). However, in order to confirm the effect of the cometary plasma as well as to assess the contribution to the level of turbulence imposed by any solar wind transients or disturbances, it is essential to simultaneously monitor a region just outside the tail of the comet during such observations.…”

Section: Introductionmentioning

confidence: 98%

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Occultation Observation to Probe the Turbulence Scale Size in the Plasma Tail of Comet Schwassmann-Wachmann 3-B

Roy

Manoharan

Chakraborty

2007

ApJ

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We present the occultation observation of compact radio source B0019Ϫ000 through the plasma tail of comet Schwassmann-Wachmann 3-B. The observation was made with the Ooty Radio Telescope at 326.5 MHz on 2006 May 26, when the plasma tail of the comet was in front of this source. The scintillation was found to be increased significantly for the target source compared to that of a control source. The intensity fluctuation power spectra show both steepening at high spatial scales and excess power at low spatial scales. This observation can be attributed to the turbulence in the comet plasma tail. A two-regime plasma turbulence can explain the timeevolution of the power spectrum during the occultation observation.

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Section: Observations and Resultsmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 98%

Occultation Observation to Probe the Turbulence Scale Size in the Plasma Tail of Comet Schwassmann-Wachmann 3-B

Roy

Manoharan

Chakraborty

2007

ApJ

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“…Increases in scintillation were noted for Comet Kohoutek (Ananthakrishnan et al 1975) and Comet Halley (Alurkar et al 1986;Slee et al 1986). Conversely, Ananthakrishnan et al (1987) were unable to confirm an enhancement for Comet Halley while Hajvassiliou and Duffett-Smith (1987) reported negative results for a number of comet-tail occultations.…”

Section: Introductionmentioning

confidence: 84%

“…The observations of Alurkar et al (1986) used suitable control sources and showed that a large increase in scintillation index was accompanied by an upward shift in the peak frequency of the power spectrum to 0·6 Hz. Although in their experiment the effect of tail lag may not have been important because of the special occultation geometry, it would be well worth their making a further analysis taking into account the opening angle of the tail and the tail lag, both of which may be available from the photographs of Halley.…”

Section: Discussionmentioning

confidence: 99%

Radio Source Scintillations Through Comet Tails Revisited: Comet Wilson (1987)

Slee¹,

Bobra²,

Waldron³

et al. 1990

Aust. J. Phys.

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Observations of the quasars 0606-795 and 0637-752 as the tail of Comet Wilson swept across them on May 1 and May 2, 1987, showed a three-fold increase in scintillation index over that of nearby compact radio sources outside the tail. Two scintillation regimes have been identified: (1) small-scale turbulence of 10-40 km develops near the tail-axis; (2) large-scale turbulence of km is present in the off-axis transition region between the tail plasma and solar wind. At a distance 0·12 AU downstream from the nucleus the r.m.s. electron-density variation in these turbules is 4-8 cm-3 on axis and 0·8-1· 7 cm-3 in the transition region between the tail and the solar wind. The reported negative results from earlier comets are shown to be of doubtful significance.

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“…The question of whether cometary plasma contained in the tail of a comet can cause radio scintillations has been addressed several times, with positive results being reported in some cases (Ananthakrishnan et al 1975;Alurkar et al 1986;Slee et al 1986) and negative results in others (Ananthakrishnan et al 1987;Hajivassiliou and Duffett-Smith 1987). Recently, it has been shown conclusively (Slee et al 1990) that cometary plasma can contain a higher level of turbulence than the normal solar wind and give rise to enhanced scintillations.…”

Section: Introductionmentioning

confidence: 93%

Enhanced Radio Source Scintillation due to Comet Austin (1989c1)

Janardhan¹,

Alurkar²,

Bobra³

et al. 1991

Aust. J. Phys.

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Enhanced scintillations in the direction of the quasar 2204+29 (3C441) were observed on 13 May 1990 when the tail of Comet Austin passed in front of it. Comparison with previous observations at 103, 327 and 408 MHz of Comet Halley and at 408 MHz of Comet Wilson show that proper occultation geometry is essential for observing enhanced scintillations. It has been shown that the solar elongation € during such observations should be large, typically greater than 60· and in no case less than 30· at 103 MHz. At the time of the occultation the scintillation index (r.m.s./mean source flux) was greater than that expected for this source by a factor of 3. The r.m.s. electron density variation /IN, at a distance of 0·9 A.U. from the sun and 7·3· downstream of the nucleus, was found to be 6 cm-3 as compared with 1 cm-3 for the normal solar wind at 1 A.U. The corresponding scale sizes of the turbulence were found to be much finer than normally found in interplanetary scintillation (IPS) caused by the solar wind.

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Radio observations of PKS2314 + 03 during occultation by comet Halley

Cited by 14 publications

References 11 publications

Occultation Observation to Probe the Turbulence Scale Size in the Plasma Tail of Comet Schwassmann-Wachmann 3-B

Occultation Observation to Probe the Turbulence Scale Size in the Plasma Tail of Comet Schwassmann-Wachmann 3-B

Radio Source Scintillations Through Comet Tails Revisited: Comet Wilson (1987)

Enhanced Radio Source Scintillation due to Comet Austin (1989c1)

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