Solar Radio Burst Mystery Solved: Harmonic Strength Tied to Solar Longitude
Researchers from the Indian Institute of Astrophysics (IIA) have explained why the relative strengths of fundamental and harmonic radio waves vary across different solar events. Their findings improve the understanding of solar coronal shocks and aid in more accurate space‑weather forecasting.
Key Developments
- Analysis of 58 Type II bursts recorded by the global CALLISTO array.
- Data from the GLOSS instrument at Gauribidanur Radio Observatory were used to trace burst origins.
- Bursts originating from active regions with heliographic longitudes > 75° show stronger harmonic emission; those < 75° display stronger fundamental emission.
- Refractive effects, directivity, and viewing angle in the corona explain the observed pattern: harmonics have broader cone angles, allowing detection on Earth even when fundamentals are blocked.
Important Facts
• Heliographic longitude is the solar coordinate measuring east‑west position of an active region on the Sun’s disk.
• Fundamental emission is theoretically expected to dominate, but observations now show a systematic longitude‑dependent reversal.
• The study examined bursts from 26 Oct 2023 (fundamental stronger) and 16 Jul 2024 (harmonic stronger) as illustrative cases.
Exam Relevance
The research links solar physics to national priorities:
- Space‑weather impacts satellite operations, aviation, and defence communications, topics covered under GS 4.
- Understanding coronal shock propagation aids the ISRO and Ministry of Earth Sciences in building early‑warning systems.
- The study showcases the role of indigenous research institutions (IIA, DST) in advancing scientific capabilities, relevant for questions on science policy and research infrastructure (GS 1).
Way Forward
• Expand the CALLISTO database and apply machine‑learning techniques to uncover further patterns. • Integrate findings into operational space‑weather models used by ISRO and the Ministry of Earth Sciences for real‑time forecasting. • Promote collaborative research between Indian institutes and international solar observatories to enhance global coverage.