# Oscillations in the 45-5000 MHz Radio Spectrum of the 18 April 2014 Flare

## TL;DR

This study analyzes the 2014 solar flare's radio spectrum using wavelet techniques, revealing quasi-periodic oscillations and multi-scale processes, and compares radio data with EUV observations to understand flare dynamics.

## Contribution

Introduces a new oscillation mapping method for radio spectra, uncovering multi-periodic oscillations and their relation to flare dynamics and magnetic reconnection.

## Key findings

- Identified 65-115 s oscillations drifting towards lower frequencies.
- Detected multi-scale oscillations with periods from 1 to 200 seconds.
- Observed fiber bursts with ~1 second periods superimposed on drifting structures.

## Abstract

Using a new type of oscillation map, made from the radio spectra by the wavelet technique, we study the 18 April 2014 M7.3 flare (SOL2014-04-18T13:03:00L245C017). We find a quasi-periodic character of this flare with periods in the range 65-115 seconds. At the very beginning of this flare, in connection with the drifting pulsation structure (plasmoid ejection) we find the 65-115 s oscillation phase drifting slowly towards lower frequencies, which indicates an upward propagating wave initiated at the start of the magnetic reconnection. In the drifting pulsation structure many periods (1-200 seconds) are found documenting multi-scale and multi-periodic processes. On this drifting structure fiber bursts with a characteristic period of about one second are superimposed, whose frequency drift is similar to that of the drifting 65-115 s oscillation phase. We also check periods found in this flare by EUV Imaging Spectrometer (EIS)/Hinode and Interface Region Imaging Spectrograph (IRIS) observations. We recognize the type III bursts (electron beams) as proposed, but their time coincidence with the EIS and IRIS peaks is not very good. This is probably due to the radio spectrum beeing a whole-disk record consisting of all bursts from any location while the EIS and IRIS peaks are emitted only from locations of slits in the EIS and IRIS observations.