Probing Coronal Activity Using Radio Signals Based on the 2021 superior conjunction of Mars: the Downlink Data from Tianwen-1

TL;DR

This study uses radio signals from Tianwen-1 during its 2021 superior conjunction to analyze solar wind and coronal activity, revealing correlations with solar phenomena and demonstrating a method for localizing solar activity.

Contribution

It introduces a novel approach to probe coronal activity by analyzing Doppler frequency scintillation of radio signals passing near the Sun during a planetary conjunction.

Findings

Frequency scintillation parameter increases as the signal path approaches the Sun.

Strong correlations between scintillation anomalies and solar phenomena like CMEs.

Temporal delay observed between scintillation changes and solar wind speed variations.

Abstract

During the first superior conjunction of the Tianwen-1 Mars probe in October 2021, its downlink signal received by the Wuqing 70-m radio telescope passed within 4.53 solar radii of the Sun. The signal was significantly perturbed by the solar wind, providing a mechanism to probe coronal activity. We analyze the Doppler frequency scintillation spectrum of the solar wind within 10 solar radii to derive a characteristic frequency scintillation parameter. Statistical analysis indicates this parameter increases as the signal path approaches the Sun, with notable anomalies observed on October 5, 13, and 15. Comparisons with SOHO and SDO data reveal strong spatio-temporal correlations between these scintillation anomalies and coronal activity. We demonstrate that this parameter effectively identifies solar phenomena, including coronal streamers, high-speed solar wind, and coronal mass ejections (CMEs). Quantitative analysis confirms a distinct temporal correlation and delay between frequency scintillation and solar wind speed changes, validating the feasibility of spatially localizing solar activity.