The bursts are observed generally in the frequency variety $approx 1,$ GHz$– 10,$ kHz, which corresponds to radial distance variety in between the low– upper corona; this indicates that type III bursts can be utilized to trace coronal magnetic field over the aforementioned distance range. Type III bursts frequently take place in groups and the individual bursts in a group are due to acceleration episodes happening at different locations in the very same active region (Reid and Ratcliffe, 2014). Observations revealing displacements in the centroid of the type III burst throughout the course of the occasion are there in the literature (Vlahos and Raoult, 1994).
We use combined radio and Hα observations to study the positional shifts. For the radio observations, we utilized the Gauribidanur Radioheliograph (GRAPH, FoV ~ 2o and resolution ~ 5, pixel size ~ 14″), the Gauribidanur Low Frequency Solar Spectrograph (GLOSS, tint ~ 250 ms, BW ~ 2 MHz) and Gauribidanur Radio Interferometric Polarimeter (GRIP, 3o by 90o), which gave us the polarized intensities.
For the Hα information, we used the Kodaikanal telescope, which has a cadence of 1 min. The field of vision is ~ 41 and the pixel size is ~ 1.2″.
The extreme patch of emission during ≈ 06:48– 06:54 UT corresponds to a group of type III bursts. The other different comparable brilliant and faint fast drifting features, but not as a group like the previous, close to ≈ 06:55:30 UT and ≈ 06:57 UT are isolated type III bursts. Its optimum was at ≈ 06:51 UT.5 A comparison of the different timings pointed out above suggests that the separated type III bursts as well as the group of type III bursts took place within the flare duration.
We traced the positional shifts of the radio and Hα images utilizing centroiding techniques (Kontar et al, 2017). For the radio images, we created maps utilizing AIPS with pixel size of ~ 14″. We recognized the source maxima at various times, for different type III bursts throughout of the group. For comparable times, we likewise used the H-alpha images, recognized a region of interest around the active region and estimated the centroids for these. We discovered that the hα and the radio centroids were spread around the active area on the solar disk (see Figure 2). We likewise discover that the centroid shifts between the hα and the radio images show a high correlation (Figure 3)
Figure 2– (a) Positions of the centroids of the Type III group as imaged by GRAPH. The little square (b) reveals a zoomed-in view into the positions of the H-alpha centroids.
This clearly suggests that the individual bursts in the type III burst group are because of temporal and spatial fragmentation of the main energy release near the flare site in the chromosphere as revealed by the Hα observations. The observations of group of type III bursts are the coronal signatures of such a fragmented energy release.
Figure 3– Correlation between the radio and H-alpha centroid positions.
We have reported the first observational proof for a correlation between the modifications in the centroid positions of a group of type III radio bursts and that of the associated Hα flare emission. Similar optical and radio observations with high spatial resolution would work to understand the topic of fragmented energy release better given that it has actually been dealt with mostly using time and spectral domain research studies to date. The magnetic coupling in between the different levels in the solar environment and how the energetic particles are assisted through the corona into the interplanetary space might also be penetrated using such observations.
Based upon a recent paper Ramesh, R.; Mugundhan, V.; Prabhu, K., The Astrophysical Journal Letters, 2020, DOI:10.3847/ 2041-8213/ ab6a9c.
H.A.S. Reid and H. Ratcliffe, 2014, Research in Astronomy and Astrophysics, 14, 7.
L. Vlahos and A. Raoult, 1995, Astron. Astrophys. 296, 844.
E. P. Kontar, S. Yu, et. al., 2017, Nature Communications, 8, 1515.
* Full list of authors: R. Ramesh, V. Mugundhan and K. Prabhu.
The bursts are observed typically in the frequency variety $approx 1,$ GHz$– 10,$ kHz, which corresponds to radial distance variety in between the low– upper corona; this implies that type III bursts can be utilized to trace coronal magnetic field over the previously mentioned distance range. Type III bursts typically take place in groups and the specific bursts in a group are due to velocity episodes taking place at different locations in the very same active area (Reid and Ratcliffe, 2014). Observations revealing displacements in the centroid of the type III burst throughout the course of the occasion are there in the literature (Vlahos and Raoult, 1994). Its optimum was at ≈ 06:51 UT.5 A contrast of the different timings discussed above suggests that the separated type III bursts as well as the group of type III bursts happened within the flare duration.
We have reported the first observational evidence for a correlation between the modifications in the centroid positions of a group of type III radio bursts and that of the associated Hα flare emission.