Fig 1 - uploaded by Emilia Correia
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Sketch of a simple antenna beam pattern of three intersecting beams observing two sources that emit at the same time.
Source publication
In this paper multiwavelength observations of an impulsive flare of May 9, 1991 are presented. This event was observed with the 48 GHz multibeam focal array used at the Itapetinga radio telescope, the microwave patrol telescopes at Bem and the BATSE high time resolution hard X-ray spectrometer on board CGRO. While spatially unresolved low sensitivi...
Context in source publication
Context 1
... simplicity the one dimensional geometry illustrated in Fig. 1 is discussed first. The simple beam pattern consists of three beams. Beams 1 and 3 are inclined with respect to the antenna axis by -θ and +θ respectively while beam 2 is aligned. This beam pattern is used to observe two small sources (S 2 and S 1 ) at an angular distance of ±ϕ from the antenna axis. Source 1 is assumed to be brighter ...
Citations
... Two components or a multicomponent microwave spectrum have been used to explain the observed spectra assuming gyrosynchrotron emission. Analysing the observed temporal evolution Stähli et al. (1990) classified these spectra in two groups: those spectra originated by two separated gyrosynchrotron sources (see for example Gary and Hurford, 1990;Herrmann et al., 1997;Cristiani et al., 2007) and those triggered by a single source or two sources that are strongly coupled (see Huang and Haisheng, 2006). ...
Almost 10years of solar submillimeter observations have shown new aspects of solar activity, such as the presence of rapid solar spikes associated with the launch of coronal mass ejections and an increasing submillimeter spectral component in flares. We analyse the singular microwave–submillimeter spectrum of an M class solar flare on 20 December, 2002. Flux density observations measured by Sun patrol telescopes and the Solar Submillimeter Telescope are used to build the radio spectrum, which is fitted using Ramaty’s code. At submillimeter frequencies the spectrum shows a component different from the microwave classical burst. The fitting is achieved proposing two homogeneous sources of emission. This theoretical fitting is in agreement with differential precipitation through a magnetically asymmetric loop or set of loops. From a coronal magnetic field model we infer an asymmetric magnetic structure at the flare location. The model proposed to quantify the differential precipitation rates due to the asymmetry results in a total precipitation ratio Q2/Q1≈104–105, where Q1(Q2) represents the total precipitation in the loop foot with the high (low) magnetic field intensity. This ratio agrees with the electron total number ratio of the two sources proposed to fit the radio spectrum.
The multiple beam technique determine burst sources positions when their angular extent are small compared with the beam shapes. We show for the first time that we carl check the above condition with the simultaneous observation using at least four beams. The developed technique is not critically dependent on source shapes. By means of simulations me found that for narrow 1 arcmin long sources the uncertainties in position determination are less than 5 arcsec, and much better for symmetrical sources. The influence of side lobes on source positions determinations was found to be negligible. A qualitative method was developed when data from only three beams are available. Both methods are applied to the analysis of a solar burst observed with multiple beams at 48 GHz with the Itapetinga 13.7 m antenna. The multiple beam technique also offers the unique advantage to determine flux density irrespectively from the position displacements of the source with respect to the beams, or vice versa. Pages: 373-382
