Solar Fast-drifting Radio Bursts in an X1.3 Flare on 2014 April 25

Abstract

One of the most important products of solar flares is nonthermal energetic particles, which may carry up to 50% of the energy released in the flaring processes. In radio observations, nonthermal particles generally manifest as spectral fine structures with fast frequency-drifting rates, named as solar fast-drifting radio bursts (FDRBs). This work demonstrated three types of FDRBs, including type III pair bursts, narrowband stochastic spike bursts following the type III bursts, and spike-like bursts superimposed on a type II burst in an X1.3 flare on 2014 April 25. We find that although all of them have fast frequency-drifting rates, they are intrinsically different from each other in frequency bandwidth, drifting rate, and statistical distribution. We suggest that they are possibly generated from different accelerating mechanisms. The type III pair bursts may be triggered by high-energy electron beams accelerated by the flaring magnetic reconnection, spike bursts are produced by the energetic electrons accelerated by a termination shock wave triggered by the fast reconnecting plasma outflows impacting the flaring loop top, and spike-like bursts are possibly generated by nonthermal electrons accelerated by moving magnetic reconnection triggered by interaction between coronal mass ejection and the background magnetized plasma. These results may help us to understand the generation mechanism of nonthermal particles and energy release in solar flares.

A Bright Fast Radio Burst from FRB 20200120E with Sub-100 Nanosecond Structure

“…On the other hand, using the measured flux density of the narrowest component at S-band and assuming its width at X-band is similarly narrow, we can place an upper limit of α < -1.8 on the spectral index of the emission process. However, we note that previous multi-wavelength observations of FRBs show patchy emission over large, instantaneous frequency bandwidths (Majid et al 2020;Pearlman et al 2020) and do not appear to support a power-law model (e.g., Spitler et al 2016;Scholz et al 2016;Law et al 2017).…”

“…Furthermore, such high time resolution studies make it possible to carry out detailed studies of scatter broadening due to the turbulent plasma between the source and the observer, including studies of ISM in the Milky Way, the Milky Way halo, host galaxy halo, ISM in the host galaxy, and finally any local scattering material near the progenitors of FRBs. Finally, high time resolution studies of FRBs will also help in identifying known analogs to FRB emission characteristics, such as the giant-pulse phenomenon seen in some pulsars, Type III solar radio bursts, and short S-shaped decametric Jovian bursts (see, e.g., Hankins et al 2015;Tan et al 2019;Shaposhnikov et al 2011).…”

“…The localization of a subset of FRBs to host galaxies at redshifts of 0.034-0.66 has confirmed the extragalactic nature of FRBs (Chatterjee et al 2017;Bannister et al 2019;Ravi et al 2019;Prochaska et al 2019;Marcote et al 2020). The current census of FRBs includes over 100 sources (Petroff et al 2016) 16 , 24 of which have been found to produce repeat bursts (e.g., see Spitler et al 2016;The CHIME/FRB Collaboration et al 2019a,b;Fonseca et al 2020). Despite the increasing number of FRB detections, their origin remains an open question with numerous progenitor and emission models that have been proposed to explain the nature of these mysterious bursts (see, e.g.…”

Μελέτη Λεπτής Υφής Σε Ηλιακές Ραδιοεξάρσεις Τύπου ΙΙ Με Χρήση Ραδιοφασματικών Παρατηρήσεων

“…Λίγους μήνες μετά τη δημοσίευση των αποτελεσμάτων μας, σε μια άλλη μελέτη ενός φαινομένου, οιTan et al (2019) εντόπισαν και υπολόγισαν δομές τύπου αιχμών, τις οποίες χαρακτήρισαν υπέρλεπτη υφή (super fine structure) επίσης στο μέτωπο της ραδιοέξαρσης τύπου ΙΙ. Εδώ η μελέτη αναφέρεται σε αντίστοιχα με τα δικά μας, μετρικά μήκη κύματος οπότε θα προβούμε σε μια σύγκριση των αποτελεσμάτων των μετρήσεων.…”

“…Αναγνωρίζοντας 140 δομές τύπου αιχμών, αριθμός που κρίνεται ικανοποιητικός για ένα φαινόμενο, υπολόγισαν μέση διάρκεια 42 ms και αντίστοιχο μέσο συχνοτικό εύρος 12 MHz. Η ερμηνεία που έχουμε προτείνει για τη δημιουργία των εξάρσεων αυτών (spike-like bursts) εντός των τύπου ΙΙ είναι η μαγνητική επανασύνδεση μικρής κλίμακας κατά μήκος του μετώπου της ραδιοέξαρσης, άποψη που υποστήριξαν και οιTan et al (2019) στην εργασία τους για τις αντίστοιχες δομές.΄Οπως είπαμε οιChernov et al (2007);Chernov (2016) ανέφεραν την ύπαρξη δομών τύπου αιχμών για ένα μόνο φαινόμενο στα δεκαμετρικά μήκη, χωρίς όμως περαιτέρω μετρήσεις ή παρατηρήσεις. ΄Ετσι δεν μπορούμε να γνωρίζουμε αν οι δομές εκείνες έχουν την ίδια προέλευση με τις μελετούμενες στην παρούσα εργασία.…”