Harmonics of Solar Radio Spikes at Metric Wavelengths

TL;DR

This study reports detailed observations of harmonic structures in solar radio spike bursts at metric wavelengths, analyzing their temporal delays and inferring coronal parameters using electron cyclotron maser theory.

Contribution

It provides new observational evidence of harmonic structures in solar radio spikes and links these to coronal magnetic and density conditions.

Findings

Harmonic structures observed in solar radio spikes with specific delay patterns.

Temporal delays between harmonics suggest electron cyclotron maser emission mechanisms.

Inferred coronal magnetic field strength and electron density from delay analysis.

Abstract

This paper presents the latest observations from the newly-built solar radio spectrograph at the \emph{Chashan Solar Observatory}. On July 18 2016, the spectrograph records a solar spike burst event, which has several episodes showing harmonic structures, with the second, third, and fourth harmonics. The lower harmonic radio spike emissions are observed later than the higher harmonic bands, and the temporal delay of the second (third) harmonic relative to the fourth harmonic is about 30\ --\ 40 (10) ms. Based on the electron cyclotron maser emission mechanism, we analyze possible causes of the temporal delay and further infer relevant coronal parameters, such as the magnetic field strength and the electron density at the radio source.