On the influence of the Sun on the rapid variability of compact extragalactic sources

TL;DR

This study investigates how the Sun influences rapid variability in compact extragalactic radio sources, revealing an annual cycle linked to solar elongation and suggesting interplanetary scintillation as a possible cause.

Contribution

It provides evidence of solar influence on radio source variability and links it to interplanetary scintillation, based on long-term monitoring and survey data analysis.

Findings

Variability amplitude shows an annual cycle correlated with solar elongation.

Fractional modulation increases as solar elongation decreases.

Results support the hypothesis of interplanetary scintillation affecting variability.

Abstract

Starting from December 2004, a program for the monitoring of intraday variable sources at a frequency of 5 GHz was performed at the Urumqi Observatory. The analysis of the variability characteristics of the flat-spectrum radio source AO 0235+164 revealed the existence of an annual cycle in the variability amplitude. This appears to correlate with the solar elongation of the source. A thorough analysis of the results of the MASIV IDV survey --- which provides the variability characteristics of a large sample of compact radio sources --- confirms that there is a small but detectable component of the observed fractional modulation which increases with decreasing solar elongation. We discuss the hypothesis that the phenomenon is related to interplanetary scintillation.