A different class of interplanetary bursts (IP) Type II that show a diffuse broadband emission of a single wide lane, but is still clear how these explosions are still formed. The radio broke out from June 17 to 18, 2003 was analyzed by Bastian (2007) who suggested that the broad and diffuse band part of the explosion (type II-s in Fig. 1) could be due to the emission of synerron. The back of the explosion (type II-P) could be identified as a plasma emission due to the pair of fundamental-anmonic lanes (FH). It has been discovered that an explosion of two similar aspects has been discovered on May 17, 2012. In this posterior event, there are radio data available from three different spacecraft, stereo-a, stereo-b and wind. The diffuse broadband emission was only visible in the stereo dynamic spectrum, that is, only from a viewing angle. This study investigates the conditions in which type II explosions of two parts are formed, to find possible explanations for non -typical radio emission structures.
Figure 1. Left: The type II gust event from June 17 to 18, 2003, which included a possible source of syncotron emission (type II-S) and a source of plasma emission (type II-P), the figure was published by Bastian (2007). Right: The type II gusts of May 17, 2012 that showed a similar two -part structure in the radio broadcast.
Observations
The events of 2003 and 2012 were associated with Halo high speed CMS. In the 2003 event, a class outbreak m6.8 Goes was located in S07E55, but no EUV wave was observed. In the 2012 event, a class flash M5.1 Goes was located near N11E42 in the stereo-a view (in N11W76 in the Earth’s view), and an EUV wave was observed. For the 2012 event, Shen et al. (2013) He suggested that there could be two rashes (CME) present, and later Grechnev et al. (2024) He concluded that there could be two disturbances similar to waves and a subsequent clash of halo involved, which suggests that there could also be three separate bursts of type II.
In the present study, the evolution of the height time of the diffuse emission and F-lane type II, compared to the evolution of the height of Lasco, seems similar in both events (Fig. 2, left panel). However, in the 2012 event, the stereo-a CME heights are much lower than the heights of Lasco CME (Fig. 2, right panel). The type II-P (lane F, marked with stars) heights are close to the stereo-a of most of the time.
Figure 2. Left: Height time graphics for the two events, which shows SOHO/Lasco CME heights with the heights of the radio source for bursts of two type II parts. RIGHT: CME HEIGHTS OF SOHO/LASCO Y Stereo-A for the 2012 event, with radio source heights of the type II-P emission (F-LANE). The red discontinuous line indicates the heights of a white light shock region near the main front of CME.
Questions
The comparison of the diffuse type II emission heights and Lasco’s CME heights suggests that the radio broadcast originates in a CME arch clash, although in the 2003 event there is a growing height difference. So, could the emission of diffuse radio in some cases due to syncrotron radiation?
In these two events, the diffuse burst of type II weakens and disappears from the spectrum near the time when the explosion of FH type II becomes visible. Pohjolainen, Allawi and Valtonen (2013) He discovered that in most diffuse types II, the emission lasts more and can be followed at much lower frequencies. So, the end of the diffuse explodes in a previous condition for the formation and appearance of the FH explosion? Are the clashes of two type II parts created by a single CME, or are they created by more than one CME and several clashes, as the 2012 event suggests?
The radio broadcast in the 2012 event was observed from three different visualization angles, but only one of them showed the diffuse emission. Are there directivity effects on diffuse emission, as in bursts of type IV? Type IV explosions are complex and can contain multiple emission mechanisms, as syncrotron emitters are trapped inside a magnetic cloud in motion (Mohan et al., 2024) .
Conclusions
There are several explanations for the creation of these radio explosions. But, without images in DH wavelengths, the locations of the true radio source are not known. Homologous events present a challenge for theory and simulations, such as how to produce similar emission characteristics.
Based on the recent article by Silja Pohjooinen, Radfagas of interplanetary radio type II of two parts, Sol. Phys. 300, Id.25, 2025, doi:10.1007/S11207-025-02449-5
References
Bastian, TS: 2007, APJ 665, 805
GRECHNEV, VV, KISEELV, VI, URORAV, AM, ET AL. 2024, sun. Phys., 299, Id.129
Mohan, A., Gopalswamy, N., Kumari, A., et al.: 2024, APJ, 971, Id.86
Pohjolainen, S., Allawi, H., Valtonen, E.: 2013, A&A, 558, ID.A7
SHEN, C., LI, G., Kong, X., et al.: 2013, APJ, 763, Id.114
#Syncrotron #nonanalysis #type #bursts #parts #Silja #PohjoolaineCommunity #radio #European #astronomers
