Introduction
Sun is a bright and active yellow dwarf star that is located at the center of our solar system and it powers up the entire solar system. Sun has a diameter of 1.39 million kilometers and an estimated mass of 1.98x 10^30 kg and it is so huge that it occupies 99.8%of the entire solar system mass. Sun has a surface temperature of 3.5 million degrees centigrade and in core temperature of scorching 15 million degrees centigrade. This temperature triggers nuclear fusion reaction which keeps our sun alive.
Solar Activity
To understand the meaning of solar minimum, first we need to have an idea about the activities happening in the sun. Sun is a blazing star with 91% hydrogen, 6-7% of helium, and traces of higher-order isotopes. Hydrogen atom called proton fuses inside the sun’s core to form alpha particle which is a helium nucleus with the release of enormous amounts of energy in the form of radiation. These radiations take several thousands of years to travel from core to the photosphere crossing different solar layers like the radiative zone and convective zone. Radiations from the photosphere reach the coronal surface and travel to the entire solar system with the speed of light. As I said above, radiations from the core of the sun have to pass through the convective zone to reach the surface. The convective layer has hot ionized gases that are in their excited state due to high temperatures and keep moving from one place to another. This rapid movement creates strong magnetic fields inside the convective layer that extends to the surface. The excitation movement of ionized hot gases causes the magnetic fields to twist, turn, and stretch which causes triggers some intense activity on the sun’s surface called Solar Activity.
Sun Spots and Solar Flares
Sunspots and solar flares are the types of solar activity which occurs due to the shifts in magnetic fields. Sunspots are the darker regions on the sun’s surface which appear like dark spots. These regions are cooler compared to other areas of the sun. The temperature of this surface would be 3600 degrees centigrade which is cooler than the other regions on the sun. The main reason for these sunspots to occur is due to the strong magnetic field in the convective zone which blocks most of the sun’s radiation to reach the surface. Solar flares are the violent explosion of radiation from these sunspots causes due to the tangling of the magnetic fields of the sunspots. This explosion shoots huge amounts of solar radiation into the solar system.
Solar Minimum
The solar cycle is a natural phenomenon happening in the sun due to the reorganizing of the magnetic fields. This happens once in eleven years. This is a tranquilized state of the sun and it lasts for months. This serene stage of the sun is called Solar Minimum. During this period, the sunspots fade away and solar flares subside. Sunspots and solar flares are the indications of an active sun. Without the sunspots and solar flares, the earth would not get the requisite amount of ultra-violet and x-ray radiations. This would cause significant changes in the solar system including Earth.
Effects of Solar Minimum
Solar minimum does not imply that the sun is becoming inactive and dull. It is just a shedding phase in the solar cycle. But there are some possible effects due to the Solar minimum.
They cause some disturbance to our earth’s magnetosphere which in turn causes geomagnetic storms. These are just small fluctuations in the earth’s magnetic field and they are temporary. This causes our satellite and navigational equipment to malfunction.
Ultraviolet rays cannot reach the earth’s surface in required amounts and cannot heat the outer atmosphere. This in turn reduces the friction drag of the outer atmosphere which becomes difficult for space junk to fall back and burn in the earth’s surface and instead floats in space.
Sun’s magnetic field is protecting the entire solar system from the dangerous cosmic rays arising from the distant supernova explosions or cosmic bursts. But due to the weakening of the magnetic field during solar minimum, the cosmic rays enter the solar system and are a threat to our astronauts and satellites in space.
We can have a glance at coronal holes, which are dense regions on the sun’s corona where the sun’s magnetic field opens up and causes energized solar radiations to escape into space as cosmic mass ejections (CME). Very powerful CME poses a threat to our magnetosphere and also can interfere with our power and electronic systems and can damage them.
Conclusion
Some are speculating that the solar minimum causes the little ice age that happened on earth during the 14th to 19th centuries. But we have to make a note on one thing that the solar minimum is just a phase in the solar minimum and it just lasts for months and is not catastrophic. With the help of Parker solar probe and large satellites, we can make use of this solar minimum and study in detail about the solar activity.
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