Plasmoids (or magnetic islands) are believed to play an necessary position within the onset of quick magnetic reconnection and particle acceleration throughout photo voltaic flares and eruptions. Direct imaging of flare present sheets and formation/ejection of a number of plasmoids in excessive ultraviolet (EUV) photos, together with simultaneous X-ray and radio observations, offers vital insights into the mechanisms driving particle acceleration in photo voltaic flares. Earlier research have proposed that decimetric radio bursts and pulsations (drifting in direction of decrease frequencies) might be produced by the ejection and coalescence of a number of plasmoids within the flare present sheet (Kliem, Karlický & Benz 2000). Drifting pulsating constructions (DPSs) in decimetric radio bursts seemingly point out the intermittent nature of power launch within the flare present sheet, and signature of radio emission from electrons accelerated through the ejection and coalescence of plasmoids (Karlický & Barta 2011). Simultaneous EUV imaging of bidirectional plasmoids in flare plasma/present sheet and the related DPS in radio have been noticed beforehand (Kumar & Cho, 2013).
On this nugget, we briefly talk about EUV imaging of plasmoids shaped in flare present sheets beneath erupting flux ropes throughout two successive flares on 2015 April 22. The bidirectional plasmoids had been related to quasiperiodic pulsations (QPP; Nakariakov & Melnikov, 2009) in X-ray (comfortable/laborious) and radio (decimetric) wavelengths. The flux rope appeared solely within the scorching channels (131/94 Å) through the first flare. We current direct imaging of the formation of double coronal X-ray sources at each ends of the flare present sheet through the ejection and coalescence of a number of plasmoids. The erupting flux rope through the second flare apparently undergoes kink instability and the formation of a plasma/present sheet together with a number of plasmoids propagating bidirectionally. In each circumstances the flux ropes reached a top of about 45 Mm (60 arcsecs) above the limb however remained confined inside the overlying strapping subject of the lively area, thus failing to provide CMEs.
Observations
The lively area NOAA 12322 was positioned on the west limb (N11W91) on April 22 2015. We studied two limb flares (C3.8, M1.1) and the related flux-rope eruption from this AR on 22 April 2015. Each flares had been practically homologous and occurred successively from the identical polarity inversion line (PIL) of the AR. Based on the GOES comfortable X-ray flux profile, the primary flare (C3.8) began at 07:59 UT, peaked at 08:06 UT, and ended at about 08:24 UT. The second flare (M1.1) began at 08:28 UT, peaked at 08:44 UT, and ended round 08:58 UT.
Determine 1: Evolution of X-ray sources (6–12 keV) through the first flare (C3.8) from 08:10 to 08:13 UT. AIA 171, 211, and 131 Å photos through the QPPs detected within the decay section of the flare. RHESSI photos within the 6–12 keV power band are overlaid on AIA 211 and 131 Å photos. The contour ranges are 40%, 60%, and 80% of the height depth. S1 and S2 characterize double coronal sources.
To watch the evolution of the RHESSI X-ray sources through the QPPs, we reconstructed RHESSI photos within the 6-12 keV vary utilizing the CLEAN algorithm. The AIA 171 and 211 Å photos exhibit a vivid plasma sheet and blobs throughout 08:10-08:13 UT (Determine 1), whereas the AIA 131 Å photos present the brilliant flare arcade (FA) and flux rope. The RHESSI picture at 08:10 UT reveals two sources above the limb (Determine 1(a4)). The decrease supply coincides with the flare arcade, whereas the higher supply aligns with the highest portion of the flux rope. Notably, we detected simultaneous X-ray (6-12 keV) and radio bursts throughout 08:11:30-08:12:30 UT (see Determine 1(a)). At 08:11 UT, the RHESSI picture reveals an extra supply (marked by an arrow, Determine 1(b4)), which is spatially aligned with the highest a part of the plasma sheet with blobs. Later, at 08:12 UT, we noticed an depth improve and extension of each the higher and decrease sources (S1, S2).
At 08:14 UT, we noticed one other faint supply, S3, between S1 and S2 (Determine 2(a4)). One minute later, the supply had moved up about 12 arcsecs within the RHESSI picture. The estimated velocity of S3 is round 150 km/s. Concurrently, we observed a lower within the top of S1 (Determine 2(b4)). RHESSI contours overlaid on AIA photos reveal that supply S3 coincides with blobs close to the apex of the plasma sheet. Supply S1 fades as its top will increase throughout 08:17-08:19 UT, whereas supply S2 stays vivid (Determine 2(c4,d4)). The supply S1 disappeared after 08:20 UT and supply S2 additionally light steadily through the decay section of the flare.
Determine 2: Evolution of X-ray sources (6–12 keV) through the first flare (C3.8) from 08:14 to 08:19 UT. AIA 171, 211, and 131 Å photos through the QPPs detected within the decay section of the flare. RHESSI photos within the 6–12 keV power band are overlaid on AIA 211 and 131 Å photos. The contour ranges are 40%, 60%, and 80% of the height depth. S1 and S2 characterize double coronal sources. S3 is the faint supply that appeared between S1 and S2.
To measure the temporal evolution and kinematics of the blobs shaped within the flare plasma sheet, we created time-distance (TD) EUV depth plots alongside and throughout the plasma sheet utilizing AIA 171 Å photos through the first flare (C3.8; 08:00-08:30 UT). The TD depth plot alongside the plasma sheet reveals the ejection of a number of blobs above the flare arcade through the flare impulsive section (08:00-08:11 UT; Determine 3 (a)). The speeds of the upward-moving blobs alongside the tracked paths are 228, 203, 208, 295, 323, 370, and 210 km/s. The TD depth plot throughout the plasma sheet reveals the blobs passing by means of the slit (Determine 3 (b)). The blobs had been detected within the plasma sheet till 08:20 UT and disappeared afterward. The white curve on the precise y-axis represents the common depth of the blobs, which is extracted between the 2 horizontal dashed strains in panel (a).
The Fermi GBM mild curve reveals the X-ray emission within the 6-12, 12-25, and 25-50 keV channels (Determine 3(c)). The X-ray emission reveals QPPs within the 6-12 and 12-25 keV bands throughout 08:00-08:20 UT, with solely weak emission within the 25-50 keV band (08:00-08:06 UT). The ejection of blobs is sort of related to the X-ray emission peaks (marked by arrows) within the 6-12 and 12-25 keV bands through the flare impulsive section (4 cycles throughout 08:00-08:08 UT). Apparently, QPPs additionally seem in the identical X-ray bands through the flare decay section, 08:11-08:20 UT. The dynamic radio spectrum reveals practically simultaneous decimetric/metric radio bursts (800-150 MHz) with the X-ray peaks through the flare impulsive and decay phases (Determine 3 (d)). The radio/X-ray emission stopped at 08:20, coinciding with the disappearance of the blobs within the plasma sheet.
Determine 3. X-ray and radio emissions related to the ejection and merging of blobs through the first flare (C3.8), from 08:00–08:30 UT. (a) and (b) TD depth plot alongside slices P1Q1 and P2Q2 utilizing AIA 171 Å photos. The white dotted strains characterize the tracks used to estimate the speeds of the upward-moving blobs. The white curve in (b) represents the imply depth (arbitrary items) extracted from between the 2 inexperienced dashed strains in (a). (c) Fermi-GBM counts within the 6–12, 12–25, and 25–50 keV power bands. (d) ORFEES radio dynamic spectrum (144–1004 MHz).
For the primary time, we noticed a double construction of the plasma/present sheet (as proven within the MHD simulation, i.e, Kliem et al. 2010) with a number of propagating blobs under the erupting flux ropes. We interpret these blobs as plasmoids shaped by reconnection within the flare present sheet. Throughout the first flare (C3.8), we noticed upward-moving reconnection outflows traced by a number of plasmoids (velocity: 200-370 km/s) and the formation of a scorching flux rope through the eruption.
Throughout the first flare (C3.8), we detected double coronal X-ray sources (6-12, 12-25 keV) positioned at each ends of the plasma sheet (i.e., under and above the reconnection website). The decrease supply was positioned above the flare arcade, whereas the upper supply was noticed close to the reconnection outflow, the place a number of plasmoids merged with the underside of the halted flux rope. The flux rope showing within the scorching channels was noticed throughout magnetic reconnection on the flare plasma/present sheet. As well as, we noticed a faint X-ray supply (6-12 keV) that appeared between the double X-ray sources (S1, S2) and was co-spatial with EUV plasmoids within the plasma sheet. The speeds of the upward-moving faint supply and the EUV plasmoids are constant.
Previous to the second flare (M1.1), a filament inside the flux rope rose slowly (35 km/s) related to brightening between its legs. The flux rope confirmed proof of kink instability and the formation of two vivid plasma sheets on the inside surfaces of its legs, joined by a central flare present sheet. The speeds of the upward and downward shifting plasmoids had been 134-330 km/s and 82-235 km/s, respectively, with plasmoid sizes starting from 2-3 arcseconds. We noticed decimetric radio bursts (proof of electron injections) related to the formation/ejection and coalescence of plasmoids into the trailing fringe of the flux rope through the impulsive section of the M1.1 flare.
Abstract
We reported the direct imaging of the formation and ejection of a number of plasmoids in flare present sheets beneath erupting flux ropes, together with QPPs in X-ray and radio wavelengths. The observations verify:
(i) that the X-ray double coronal sources noticed by RHESSI are positioned at each ends of the flare present sheet, and shaped throughout plasmoid-mediated reconnection within the sheet;
(ii) the faint transient supply that appeared between the double coronal sources is most definitely related to upward-moving plasmoids;
(iii) the presence of a flare present sheet with double construction and a number of plasmoids, as predicted by an MHD simulation of kink-unstable flux rope (Kliem et al. 2010);
(iv) the formation of a plasma/present sheet at the vanguard of the kink-unstable flux rope throughout its encounter with the overlying flux system;
(v) that the coalescence of upward-moving plasmoids on the underside of the flux rope is accompanied by decimetric radio bursts;
(vi) X-ray/radio QPPs (P=10 s, 100 s) are related to ejection and coalescence of plasmoids within the flare plasma/present sheet.
These findings improve our understanding of plasma heating and the quasi-periodic acceleration of electrons through plasmoid-mediated reconnection in flare present sheets under erupting flux ropes. The manufacturing of energetic electrons by means of the ejection and coalescence of plasmoids within the plasma sheet has broad applicability to understanding quick magnetic reconnection in photo voltaic, heliospheric, and magnetospheric present sheets. The direct imaging of plasmoids and related QPPs offers key insights into plasmoid-mediated magnetic reconnection and particle acceleration, supporting theoretical fashions of those processes throughout photo voltaic flares. Sooner or later, comparable flare occasions together with simultaneous EUV, radio, and laborious X-ray imaging will yield additional insights into the electron acceleration websites related to plasmoids throughout magnetic reconnection in photo voltaic eruptions.
Primarily based on a current paper by Pankaj Kumar, Judith T. Karpen, and Joel T. Dahlin X-Ray/Radio Quasiperiodic Pulsations Related to Plasmoids in Photo voltaic Flare Present Sheets (2025), ApJ, 980, 158. DOI: 10.3847/1538-4357/ada293
References
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Kliem, B., Linton, M.~G., Torok, T., et al. 2010, SoPh, 266, 91.
Kumar, P. & Cho, Okay.-S. 2013, A&A, 557, A115.
Nakariakov, V.~M. & Melnikov, V.~F. 2009, SSR, 149, 119.
