Recently, a considerable sunspot group known as ‘AR2770’ has been detected. Although it emitted minor space flares that led to subtle waves of ionization rippling through Earth’s upper atmosphere, there was not any significant impact on Earth.
Understanding Sunspots
Sunspots, in some instances reaching up to 50,000 km in diameter, are areas on the Sun’s surface (photosphere) that appear darker due to their cooler temperature compared to other parts of the Sun’s surface. Even though these spots are considered ‘cooler’, they still maintain a high temperature—around 6,500 degrees Fahrenheit. Photosphere, the visible surface of the Sun, emits most of the Sun’s light that reaches Earth directly.
Sunspots are relatively cool because they form at areas where magnetic fields are particularly strong. These magnetic fields hinder some of the heat within the Sun from reaching the surface. In fact, the magnetic field in such areas is approximately 2,500 times stronger than Earth’s. Sunspots typically consist of a dark region known as the ‘umbra’, surrounded by a lighter region called the ‘penumbra’.
Every solar cycle, the number of Sunspots tends to fluctuate. The current solar cycle, which began in 2008, is in its ‘solar minimum’ phase, indicating a routine low in the number of sunspots and solar flares.
The Phenomenon of Solar Flares
Near sunspots, the magnetic field lines often entangle and reorganize, potentially causing a sudden explosion of energy known as a solar flare. The energy released in a solar flare can be equivalent to a trillion ‘Little boy’ atomic bombs, like those dropped on Hiroshima and Nagasaki in 1945. Solar flares disseminate a high amount of radiation into space.
Solar flares, if potent enough, can disrupt satellite and radio transmission on Earth, and severe ones can inflict ‘geomagnetic storms’, which may damage transformers in power grids. A geomagnetic storm represents a significant disturbance of Earth’s magnetosphere, resulting from an efficient energy exchange from the solar wind into the space surrounding Earth.
The Earth’s magnetosphere, a region dominated by Earth’s magnetic field, safeguards the Earth from solar and cosmic radiation and also prevents the erosion of the atmosphere by the solar wind, a continuous flow of charged particles radiating from the Sun.
Coronal Mass Ejections & Auroras
Solar flares are sometimes accompanied by Coronal Mass Ejections (CME). These are massive bubbles of radiation and particles from the Sun’s Corona or the outermost region of the Sun’s atmosphere. The magnetic field lines of the Sun suddenly reorganize to release CMEs, causing them to explode into space at extremely high speeds.
These CMEs can trigger intense light displays in the sky on Earth, known as auroras. Some of the energy and small particles from these solar occurrences travel down the magnetic field lines at the north and south poles into Earth’s atmosphere. Here, these particles interact with gases, lighting up the atmosphere in breathtaking displays of color. Oxygen emits green and red light, while Nitrogen glows blue and purple. The northern hemisphere experiences this phenomenon as the aurora borealis or northern lights, while the southern hemisphere sees it as the aurora australis or southern lights.
The Solar Cycle
The Sun, an immense ball of electrically-charged hot gas, moves to generate a powerful magnetic field. This field undergoes a cycle, termed the solar cycle, wherein every 11 years or so, the Sun’s magnetic field completely flips, interchanging its north and south poles. It then takes about another 11 years for the poles to flip back again.
This solar cycle regulates activity on the Sun’s surface, like sunspots, which emerge as a result of the Sun’s magnetic fields. As these magnetic fields transform, so does the activity level on the Sun’s surface. The solar cycle can be tracked by counting the number of sunspots. A new cycle begins with a solar minimum, where the Sun has the least sunspots. Gradually, solar activity—and the number of sunspots—increases to peak at the solar maximum, where the Sun has the most sunspots, before receding back to the solar minimum.