Coronal Holes

stock here: this is the most extreme solar activity I have ever seen

Coronal holes are regions on the Sun’s surface characterized by open magnetic field lines, allowing high-speed solar wind to escape into space. Understanding their behavior is crucial, as they can influence space weather and geomagnetic conditions on Earth. Several datasets and studies have been developed to analyze the historical evolution of coronal holes:​
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1. NOAA’s National Centers for Environmental Information (NCEI):

NCEI offers extensive solar coronal data, including:​
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Green Coronal Emission Line Observations (1939-present): Daily coronal intensity measurements taken every 5 degrees around the solar disk, providing insights into long-term coronal activity.​
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Digital Solar Synoptic Maps in H-alpha (1966-1987): These charts display large-scale magnetic field structures and locations of coronal holes, facilitating studies of solar magnetic polarity over time.​
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These datasets are accessible for research and analysis. ​

2. Solen’s Coronal Hole History:

Solen.info maintains a detailed log of coronal holes since October 2002, documenting attributes such as:​
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Location and Polarity: Identifying whether coronal holes are situated in northern, southern, or equatorial regions, along with their magnetic polarity.​
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Earth-Facing Position Dates: Timeframes when coronal holes are directed towards Earth, which is critical for anticipating geomagnetic disturbances.​

Associated Geomagnetic Activity: Correlating coronal holes with geomagnetic disturbances, including metrics like the Kp index and maximum solar wind speeds.​
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This resource is valuable for correlating coronal hole occurrences with geomagnetic impacts on Earth. ​

3. Statistical Studies on Coronal Hole Evolution:

Research has focused on the long-term behavior of coronal holes. For instance, a study analyzed 16 long-lived coronal holes observed by the Solar Dynamics Observatory (SDO) from 2010 to 2019, examining their coronal, morphological, and underlying photospheric magnetic field characteristics. The study found that coronal holes typically grow to a maximum size before decaying, with area change rates influenced by the solar cycle. ​
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4. Catalogs of Non-Polar Coronal Holes:

The Collection of Analysis Tools for Coronal Holes (CATCH) provides a catalog of non-polar coronal holes during the SDO era (2010-2019). This resource includes data on coronal hole sizes, magnetic field strengths, and distributions across various latitudes, offering insights into their properties and evolution. ​
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5. Historical Solar Cycle Data:

SpaceWeatherLive.com offers charts depicting sunspot numbers since 1749, marking the beginning of extensive solar activity records. These charts allow for comparisons between different solar cycles, aiding in understanding the Sun’s long-term behavior and its correlation with coronal hole occurrences. ​
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These datasets and studies provide comprehensive insights into the historical behavior of coronal holes, their evolution over solar cycles, and their impact on space weather phenomena affecting Earth.