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IIA study explains Sun’s microwave polar brightening mechanism
Recent research by scientists at the Indian Institute of Astrophysics (IIA) comprises an investigation of the mechanism behind solar microwave polar brightening. The study comprises collaboration among ARIES, Nainital, the Udaipur Solar Observatory (USO), the Physical Research Laboratory (PRL), and IIT Roorkee. The reported findings comprise identification of the magnetic mechanism for “Microwave Polar Brightening,” also called microwave aurorae, in the Sun.
Microwave Polar Brightening:
| Dimension | Key Details |
|---|---|
| Phenomenon and observation band | Microwave polar brightening comprises a condition in which solar poles appear brighter than the quiet central disk at high radio frequencies in the microwave spectrum, around 17-37 GHz. |
| Solar-atmosphere origin region | The microwave enhancement comprises emission originating in the upper chromosphere and low transition region of the solar atmosphere. |
| Large-scale magnetic driver | Large-scale poloidal fields comprise a driver in which microwave polar brightening applies to maximum intensity during solar activity minima because global polar magnetic fields are strongest at this stage of the 11-year solar cycle. |
| Small-scale magnetic driver | Small-scale unipolar magnetic elements comprise concentrated patches of brightening driven by small, intense, unipolar magnetic structures, described as unipolar network elements, embedded near the poles. |
| Plasma heating and radiation process | Localized heating of solar plasma comprises elevated electron temperature and density that increase free-free thermal bremsstrahlung radiation at microwave frequencies. |
| 11-year solar cycle linkage | Solar minimum comprises strong, well-defined global polar magnetic fields and low active-region sunspot count, and comprises maximum brightening with enhanced concentration of unipolar magnetic network elements at the poles; solar maximum comprises weakening, decay, and field reversal of global polar fields with high active-region sunspot count, and comprises minimum brightening with sharp decline in polar microwave emission due to disruption and dispersal of polar magnetic structures. |
| Proxy utility | The phenomenon provides for a proxy for measuring the strength of the Sun’s poloidal magnetic field, and this proxy applies to predicting the strength and timing of future solar cycles. |
| Mission and forecasting relevance | The findings comprise complementarity with measurements from Aditya-L1 and NASA/ESA’s Solar Orbiter, and this complementarity applies to forecasting models for solar wind acceleration, coronal mass ejections (CMEs), and geomagnetic disturbance risks to satellite operations. |