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Updated: Jun 5, 2026
06:28
Visualization of Low-Level Gamma Radiation Sources Using a Low-Cost, High-Sensitivity, Omnidirectional Compton Camera
Published on: January 30, 2020
Solar Cycle Variation of Sustained Gamma Ray Emission from the Sun
Nat Gopalswamy1, Pertti Mäkelä1,2, Seiji Yashiro1,2
1NASA Goddard Space Flight Center, Greenbelt, MD USA.
Solar Physics
|June 4, 2026
Summary
Solar Cycle 25 shows a higher rate of sustained gamma ray emission (SGRE) events than Solar Cycle 24, despite data gaps. Increased solar activity, including fast and wide coronal mass ejections, correlates with more SGRE events.
Area of Science:
- * High-energy astrophysics
- * Solar physics
- * Space weather
Background:
- * Sustained gamma ray emission (SGRE) events are energetic solar phenomena.
- * Fermi Gamma-ray Space Telescope data from Solar Cycle (SC) 24 and the rising phases of SC 25 are analyzed.
- * A significant reduction in solar coverage (LAT gap) due to instrument malfunction in SC 25 posed a challenge for event detection.
Purpose of the Study:
- * To investigate and estimate the occurrence rate of SGRE events during SC 25.
- * To compare the activity levels of SC 25 with SC 24 using SGRE event rates.
- * To understand the relationship between SGREs and other solar energetic phenomena.
Main Methods:
- * Analysis of Fermi-LAT data from 2008 to cover SC 24 and early SC 25.
- * Estimation of SGRE events in SC 25 using three distinct methods: sunspot number correlation, association rates with fast and wide coronal mass ejections (FW CMEs) and decameter-hectometric (DH) type II bursts, and inference from hard X-ray (HXR) bursts during data gaps.
- * Comparison of SGRE event numbers with solar activity indicators like sunspot number (SSN), FW CMEs, and DH type II bursts.
Main Results:
- * Fewer SGRE events (16) were observed in the first 61 months of SC 25 compared to SC 24 (27), despite higher average sunspot numbers in SC 25.
- * Other energetic events, including FW CMEs and DH type II bursts, increased significantly in SC 25.
- * Three independent estimation methods converged to suggest a higher number of SGRE events in SC 25 (estimated at 43-50 events) compared to SC 24.
Conclusions:
- * Solar Cycle 25 is demonstrably more active than Solar Cycle 24, as indicated by the estimated higher occurrence rate of SGRE events.
- * The findings are consistent with increased occurrences of other energetic solar phenomena and geomagnetic storms in SC 25.
- * SGRE events are strongly associated with hard X-ray bursts, providing a method to infer events during observational gaps.
Keywords:
Coronal mass ejectionsGamma-raysSolar Cycle variationSolar energetic particle eventsType II solar radio burstsMore Related Videos
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