Comparison of solar wind speed estimates from nearly simultaneous IPS observations at 327 and 111 MHz

TL;DR

This study compares solar wind speed estimates from IPS observations at 327 and 111 MHz over six years, revealing moderate correlation for a compact source and low correlation for an extended source, highlighting potential biases.

Contribution

It provides a detailed comparison of solar wind speed estimates from two different IPS observation methods and investigates sources of discrepancies.

Findings

50% correlation for 3C48 speed estimates

Annual averages align with solar cycle variation

25% correlation for 3C298 speed estimates

Abstract

Results are presented of a comparison between solar wind speed estimates made using the time delays between 3 pairs of 327 MHz antennas at ISEE and estimates made by modeling the temporal power spectra observed with the 111 MHz BSA antenna at LPI. The observations were made for 6 years in the descending phase of solar cycle 24. More than 100 individual records were obtained for the compact source 3C48 and the extended and anisotropic source 3C298. The correlation between the daily speed estimates from 3C48 is 50%. Their annual averages agree within the error estimates and show the expected solar cycle variation. However the correlation between speeds from 3C298 is only 25% and their annual averages do not agree well. We investigate possible causes of this bias in the 3C298 estimated speeds.