Radio emission from the rise was discovered by the NRH during 2 periods: from 11:49 to 11:51 UT (phase A) and from 12:00 to ~ 13:00 UT (phase B). We further keep in mind that in both stages two sources appear in the high-frequency NRH images where the resolution is greater (Figure 1); moreover, during phase B the upper source is plainly displaced upwards, compared to phase A, which is apparently an outcome of the expansion of the rise. The positions of the NRH lower source, from 327 to 435 MHz, calculated for emission at the basic, projected very close to the base of the surge on the sky aircraft as seen from STEREO-A (right panels of Figure 3).
A and B refer to the matching phases of the emission. The limitations of the 304Å rise derived from triangulation are also outlined in red for referral.: Computed NRH source positions from 327 to 435 MHz (red filled circles) projected on the sky plane as seen from STEREO-A, on top of base-difference 304 Å images near stage A (left) and throughout phase B (right).
Conclusions.
We reported the detection of metric radio emission from a surge, associated with a secondary energy release during the late phase of the M9-class flare of February 12, 2010, that was formerly analyzed in Paper I. This is the very first time that direct imaging of a surge is reported. The detection of surge-associated emission includes one more manifestation to the list of flare-associated metric radio emissions.
The NRH images revealed that the rise occurred in two stages and included 2 sources. Short-scale time variations appeared in both, with a minor delay suggesting superluminal speeds; an appropriate consideration of the geometry exposed that scattering of radiation from the lower source by the upper source is the most likely explanation.
The observed high degree of circular polarization, as well as the existence of spikes and pulsations in the dynamic spectrum, might be accommodated by plasma emission from the essential. Furthermore, radio source positions computed under this system follow the surge position as seen from STEREO-A. Thus, we consider type IV-like plasma emission with a low strength gyrosynchrotron element as the most possible system.
Based upon a recent paper by Alissandrakis, C. E., Patsourakos, S., Nindos, A., Bouratzis, C., Hillaris, A., 2022, A&A, 662, A14. https://doi.org/10.1051/0004-6361/202243169.
Referrals.
Alissandrakis, C. E., C. E., Nindos, A., Patsourakos, S., Hillaris, A, 2021, A&A, 654, A112. doi:10.1051/ 0004-6361/2021 41672 (Paper I).
* Full list of authors: Costas Alissandrakis, Spiros Patsourakos, Alexander Nindos, Costas Bouratzis and Alexander Hillaris.
Practically all solar phenomena observed in radio wavelengths have their counterpart in other regions of the electro-magnetic spectrum. This is apparently because metric bursts result from meaningful plasma emission, which has no observable signature outside the radio variety.
NRH images in overall intensity of the rise at all ten frequencies throughout the first (leading) and the second (bottom) phase of the occasion. The white arc marks the solar limb, the insert shows the NRH beam (resolution), while the crosshair is positioned at the optimum of the lower source at 445 MHz throughout the first stage.
Observations and Analysis.
We utilized images from the Nançay Radioheliograph (NRH) at ten frequencies with a cadence of 250 ms and a spatial resolution of 1.20 ′ by 1.80 ′ at 432 MHz, vibrant spectra from the ARTEMIS-JLS radiospectrograph and CALLISTO; light curves from GOES, Hα images from Catania, soft X-ray images from the GOES Soft X-ray Imager (SXI), EUV images at 304 Å with a cadence of 10 minutes from STEREO SECCHI A and B and coronagraph images from STEREO COR1, with a cadence of 5 minutes. Seen from STEREO-A, the event was really near the E limb, whereas it was near the W limb for STEREO-B. No EIT information were offered throughout the occasion. The three-dimensional position of the rise functions was computed from triangulation of STEREO A and B images at 304 Å and, from that, the forecast of the rise on the aircraft of the sky, as seen from the Earth.
Outcomes.
Radio emission from the surge was identified by the NRH throughout 2 periods: from 11:49 to 11:51 UT (phase A) and from 12:00 to ~ 13:00 UT (phase B). We further keep in mind that in both phases two sources appear in the high-frequency NRH images where the resolution is greater (Figure 1); moreover, throughout phase B the upper source is plainly displaced upwards, compared to stage A, which is apparently a result of the expansion of the rise.
Stirs I cuts (intensity as a function of time and position along the surge), at complete time resolution, for 445.0, 432.0, and 408.0 MHz, during phase A of the surge. Absolutely no position is at the middle of the cut.
Short-scale time variations were found during both phases of the rise. An example is displayed in Figure 2, which offers images (cuts) of the intensity as a function of time and position along the axis of the rise throughout the stage A. Interestingly, the variations in the upper lower and upper source are highly correlated, with a small time hold-up, which appears as an inclination of the features in the Figure. Trusted, this delay translates to propagation at superluminal speed. When the geometry is effectively taken into account (left panel of Figure 3), a more plausible explanation is that this hold-up is due to scattering of radiation from the lower source by the upper source.
NRH images showed a high degree of circular polarization, verified by dynamic spectra; the latter likewise showed pulsations and spikes. All these point towards type IV-like plasma emission from the fundamental. The positions of the NRH lower source, from 327 to 435 MHz, calculated for emission at the fundamental, projected very close to the base of the surge on the sky airplane as seen from STEREO-A (ideal panels of Figure 3).
We reported the detection of metric radio emission from a rise, associated with a secondary energy release throughout the late stage of the M9-class flare of February 12, 2010, that was previously evaluated in Paper I. The detection of surge-associated emission includes one more symptom to the list of flare-associated metric radio emissions.
