Solar flares accelerate energy electrons. While some of them escape the interplanetary space and produce explosions of interplanetary solar radio type III, the electrons that interact with the solar atmosphere produce a hard X -ray emission (HXR). Many studies related to the Radio III radio gust observations and HXR emissions from the first observations of its temporary association (for example, Kane 1972, 1981). More recently, statistical studies were carried out by https://www.aanda.org/article/Aa/Full_html/2025/02/AA52278-24/AA52278-24.html and James and Vilmer (2023) In the link between electrons that produce HXR emissions and the properties of type III coronal gusts and the association with interplanetary explosions of type III. With Stix and RPW now observing continuously in the same spacecraft (solar orbiter), we are in a unique position to follow the exploration of the association between HXR shoots and interplanetary bursts type III.
The recent study by Paipa-Leon et al. (2025) It is based on five days of observations (November 17 to November 21) in 2020, when Stix and RPW provided the first simultaneous observations of X -ray flashes and type III radio bursts in Orbitter Solar (Figure 1).
Figure 1. RPW/STIX OBSERVATIONS From November 18 at 00:00 UT to November 19 at 6:00 p.m. UT. (Upper curve) from top to bottom: RPW-TNR spectacRAMS (100–425 KHz) and RPW-HFR (425 KHz-8 MHz) and Stix speed light curves. The vertical lines indicate the start time of type III. (Lower curve) For six flares, X -ray contours superimposed on EUV (EUI) images in the 174 Å band. The colored coding of the contours energy band is the same as in the upper panels.
Figure 1 shows that the association between the two types of issuance is not one by one, as already known in previous studies. The stronger X -ray outbreak detected up to 80 KEV does not have a type III counterpart. The most intense type III IP burst (event 8) is associated with a relatively weak Bengal (without counts greater than 16 KEV). During the entire observations period, it was discovered that 21 type III IP explosions and HXR Bengals were temporarily associated (with a total of 232 HXR flares observed by Stix and 32 bursts of type III observed by RPW).
Figure 2: Event on November 17 ∼ 01:25 UT. (Left from top to bottom): RPW spectrograms and STIX counting speed spectrogram and light curves in different overlapping energy ranges. The start time of the X -ray Bengal, the start time of Ráfaga IP type III and the associated X -ray peak time are marked with vertical lines in magenta, blue and purple. (Right) X -ray contours at selected time intervals in the image EUI/FSI in the 174 Å band.
Figure 2 shows that the beginning of the IP Ráfaga Type III is not necessarily associated with the first HXR peak of the Bengal or the most energetic, but may be associated with later peaks. This is the case for most flares in our sample. Only in six cases the IP type III explosion is temporarily associated with the main HXR peak. The delays between the start of the type III IP explosions and the time of the associated HXR peaks vary from a few seconds to about five minutes, with most of them less than three minutes. These delays are consistent with the propagation time of electrons with speeds of around 0.1 C (typical of electrons that produce bursts type III) between the injection time from the low crown to the place where they can produce radio emissions in the frequencies vary from 6.52 MHz to 675 kHz). Figure 2 (right) also shows that changes in the morphology of HXR sources are observed near the start of the type III IP gusts. This is observed in all the flares of our sample. Additional X -ray sources appear near pre -existing X -ray sources on the disc or in the limb (see Figure 2B) or an elongation of the X -ray source is observed when the active region is behind the limb (see Benadas 12 and 13 in Figure 1).
Conclusions
Figure 3 describes a possible scenario to explain the appearance of new X -ray sources or the elongation of X -ray sources for flares close to the limb. Successive reconnection episodes produce energy electrons in magnetic configurations with different connectivity with the upper solar atmosphere. There is a first reconnection event in the low crown and produces energy electrons that emit HXR. This first episode is not associated with a radio explosion since energy particles do not have access to open field lines. As the magnetic configuration evolves, a new reconnection event occurs higher in the crown between closed and open field lines. Some accelerated electrons produce radiographs and some of them spread on the open field line and produce type III bursts. If the active region that comes on is still on the disc, the new reconnection event leads to the appearance of new views. Weak coronal sources can also be produced in the loop near the reconnection sites. When the standing points are hidden (active region near the limb or behind), these coronal sources can be detected and new sources that appear higher in the crown can be observed in relation to the new episode of reconnection. Given the limited spatial resolution or the long integration times, the appearance of the new coronal source may appear as an elongation.
Our results confirm the important role of the reconnection of the exchange in the access of accelerated electrons with Bengal to open magnetic field linesas before in EG Krucker et al., 2008.
Figure 3: Cartoon the proposed reconnection scenario (adapted from Glesener et al. 2012). myNergy’s release is triggered by an emerging loop in the integrated active region In open field lines. Reconnection occurs between the closed growing loop and the open magnetic field line. Energy electrons that travel along the reconnected field lines (orange arrows) produce hard x -ray emissions at views (in BLue; They can be hidden if the active region is behind the limb) and in coronal sources (in Magenta) cloI know the reconnection site (in red). They can also escape along the magnetic field line open in the crown towards the IP and Prod medium.Type III UCE rags (in green).
Based on the recent article By Paipa-Leon, D., et al. Connecting energy electrons to the sun and in the helosphere through X -rays and radio diagnoses, Astronomy and Astrophysics, Volume 694, ID.A111, DOI: 10.1051/0004-6361/202452278
References
Glesener, L., Krucker, S. and Lin, RP 2012, APJ, 754, 9
James, T. and Vilmer, N. 2023, A&A, 673, A57
Kane, Mr. 1972, Sol. Phys., 27, 174
Krucker, S., Saint-Hilaire, P., Christe, S., et al. 2008, APJ, 681, 644
#Connecting #energy #electrons #sun #Helosphere #Xray #diagnoses #radio #PaipaLeon #European #astronomer #radio #community
