One crucial job linked with the corona heating issue is exploring the physical mechanisms that produce, speed up, and transport energetic particles in the upper corona. In numerous cases, Type III bursts are observed without indications of activity in the hard X-ray emission in the lower corona.
Recently, throughout the first Parker Solar Probe perihelion, an uncommon narrowband radio emission in the 5– 7 GHz band originating from the weak X-ray intense point on 13 April 2019 was discussed by Altyntsev et al. (2022 ). An analysis showed that attributes of the spectrum of microwave emission indicated a coherent emission system produced by electrons caught in low coronal loops. The emission was produced by electrons with energies of a number of 10s of keV at the harmonic of the plasma frequency. In addition, numerous bursts were observed by LOFAR over this time but there were no signatures of the nonthermal emissions in hard X-rays. The objective of this study is to discover the low corona source of type III and/or J bursts at meter wavelengths using the spatially dealt with microwave observations.
Observations
The various short bursts cover the getting band of the LOFAR Low Frequency Array (Fig. 1a) during the interval 05:43:30– 07:39:59 of typical observations with the BBMS spectropolarimeter in the microwave range 4– 8 GHz (Fig. 1b). We have discovered a box in the LOFAR dynamic spectrum (Fig. 1a) for which the cross-correlation coefficient with a typical microwave profile over the range of 5- 7 GHz profile is high and surpasses 0.7.
One essential task connected with the corona heating issue is checking out the physical systems that produce, accelerate, and transportation energetic particles in the upper corona. In numerous cases, Type III bursts are observed without signs of activity in the tough X-ray emission in the lower corona. It must be noted that microwave observations on large radioheliographs can be more delicate to the look of nonthermal electrons to the lower corona (Altyntsev et al. 2020).
An analysis showed that characteristics of the spectrum of microwave emission suggested a coherent emission mechanism produced by electrons trapped in low coronal loops. The objective of this study is to find the low corona source of type III and/or J bursts at meter wavelengths utilizing the spatially fixed microwave observations.
Figure 1. Dynamic spectra on 13 April 2019, recorded by LOFAR (a) and BBMS in microwaves (b). Package in panel a) with the time bounds from 05:45:15 till 06:56:40 and frequency variety 53– 80 MHz offers the spectrum region for which there is a high cross-correlation coefficient with the microwave emission at 6 GHz.
Figure 2. Images on 13 April 2019. a) Solar disk at 171 A (SDO/AIA) and contours of brightness temperature at 50, 60, 70 MHz at half height at 06:48 (LOFAR); b) AR 12635 in soft X-rays (XRT/Hinode) at 06:04 and 06:24 (box in the upper right corner) together with the line of sight electromagnetic field component ± 100, ± 300, ± 1000, ± 1500 G). Red and blue shapes show favorable and negative elements, respectively. White contours at (0.2, 0.5, 0.9) × 0.6 MK corresponds to brightness temperature at 6.25 GHz (SRH) in intensity at 05:44:49. The SRH beam width is 52 × 35 arcsec. Black strong and rushed shapes suggest the brightness temperature level in the right and left polarization, respectively. The levels are (0.5, 0.7) × 2.8 ・ 104 K and -( 0.7, 0.5) × 1.6 ・ 105 K.
Altyntsev et al. (2022) revealed that the microwave emission in the frequency band 5– 7 GHz was created by a relatively small number of accelerated electrons, trapped in the loop, related to intense X-ray point A. To study the electromagnetic field structure around the favorable polarity addition and the intense XRT loop we assumed local non-potentiality of the magnetic field and carried out a nonlinear force-free field restoration in the little subvolume near point A. Small-scale electromagnetic field lines near this point A correspond to the intense function in the XRT image. Potential-field extrapolation reveals that the small magnetic flux, anchored to the magnetic inclusion, is overlapped by the fairly large-scale magnetic flux, anchored to the surrounding magnetic polarity. The vertical parts of the electromagnetic field vectors of the small and big loops are anti-parallel at carefully spaced areas, which produces beneficial conditions for magnetic reconnection. This is referred to as “interchange reconnection” if a field line that is open to interplanetary area changes the area of its photospheric footpoint (Cairns et al. 2018). Post-reconnection field lines take the shape of a little hot loop and field lines that are open to interplanetary area. Hence, it is shown that the source of a series of type III and/or J bursts in the frequency variety 50– 80 MHz is the interaction of two loop systems with substantially various lengths.
We can conclude that using large multiwave radioheliographs makes it possible to expose non-thermal procedures in the solar corona not only in weak flares, but also in short-term occasions. The combination of cross connection analysis of the temporal profiles of radio emission from the lower and upper corona with the localization of sources makes it possible to validate the approaches of reconstruction of coronal magnetic fields.
Based upon the current paper by Altyntsev, A. T., Reid, H., Meshalkina, N. S., Myshyakov, I. I., Zhdanov, D. A. Temporal and Spatial Association Between Microwaves and Type III Bursts in the Upper Corona: 2023, Astronomy& & Astrophysics, 671, A30, DOI: 10.1051/ 0004-6361/2022 44599.
References
Altyntsev, A.T., Meshalkina, N.S., Fedotova A.Ya. & & Myshykov I.I.: 2020, ApJ, 905, 149, 13pp.
Altyntsev, A.T., Meshalkina, N.S., && Myshykov I.I.: 2022, Solar-Terrestrial Physics, 8,3.
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Cairns, I. H., Lobzin, V. V., Donea, A., et al.: 2018, Scientific Reports, 8, 1676.
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* Complete list of authors: Altyntsev1, A. T., Reid2, H., Meshalkina1, N. S., Myshyakov, I. I. 1,., Zhdanov1, D. A.
1Institute of Solar-Terrestrial Physics SB RAS, Lermontov St. 126A, Irkutsk 664033, Russia
2 Mullard Space Science Laboratory, Department of Space and Climate Physics, University College London, Dorking, United Kingdom