Solar Flares
The solar wind is a constant stream of particles and magnetic fields released by the sun.
This solar wind hits planets across the solar system with particles and radiation – which can stream all the way to planetary surfaces unless thwarted by an atmosphere, magnetic field, or both.
On earth, The solar wind is mostly deflected by our magnetic field, but sometimes, when intense, some of it can leak through. Once in near-Earth space, the particles can trigger aurora near the North and South pole.
The solar wind is created by an expansion of plasma from the sun’s corona. This plasma is continually heated to the point that the Sun’s gravity can’t hold it. It then travels along the sun’s magnetic field that extends outward. As the sun rotates every 27 days, it winds up its magnetic field lines above its polar regions into a large rotating spiral, creating a constraint stream of solar “wind.”
The coronal magnetic field (Sun’s magnetic field) controls all the dynamics and topology of the Sun’s phenomena. A theory suggested that the corona was heated by shock waves from the convection zone. But the solar probes are expected to research the origins of this coronal magnetic field.
How do solar transients drive heliospheric variability?
The Sun exhibits phenomenons, such as solar flares, and coronal mass ejections. These events affect the structure and dynamics of the outflowing solar wind and so eventually affect Earth’s upper atmosphere, creating what is known as 'space weather'. This changes in the course of long periods of time.
There are fundamental questions to be answered about these events occurring and how they develop if in the future we are to attempt to predict such occurrences or their effects on Earth and space around us. This will also help our understanding about the inner workings of other stars.
Operating close to the sun, Probes such as the Solar Orbiter will be able to sample the fields and plasmas from their mission. This will allow Solar Orbiter both to determine the input to Earth’s atmosphere, and to measure the consequences of eruptive solar events.
How do solar eruptions produce energetic particle radiation that fills the heliosphere?
The sun, capable of accelerating energetic particle radiation close to the speed of light, is the solar system’s most forceful particle accelerator. The radiation generated and accelerated is powerful enough to penetrate Earth’s magnetic field and be detected on the surface. The radiation, called Solar Energetic Particles(SEP), is powerful enough to disrupt radio communications, critically damage spacecraft, and disrupt navigation systems.
The majority of the equipment onboard Solar Orbiter is purposed for researching the source and formation of Solar Energetic Particles. This will be done by recording data with onboard sensors and taking images at various wavelengths on the electromagnetic spectrum. With the data gathered by Solar Orbiter, scientists will be able to identify the mechanisms which cause Solar Energetic Particles.
Wave Heating
In short, the question concerning how heat is transferred to the corona has remained unanswered. However, currently, scientists have developed hypothesises to help explain this. One of them is "Wave Heating."
Wave heating is an idea that refers to how strong waves of energy are created by the turbulence of the Sun’s surface and transferred to the corona, heating it. These waves of ions and electrons move in a wave-like motion, back and forth which therefore means a magnetic field is also generated. Though the magnetic field does not move exactly the same way as the particles, it can change strength and direction as the wave travels. The magnetism it possessed can also give it some extra energy.
Owing to this hypothesis, as the waves move away from the sun, all that energy eventually turns into heat that increases the temperature of the corona. But this alone is still not enough to make corona as hot as it is.
In 2011, scientists found that wave heating could be enough for only getting the corona to the bottom of its temperature range while studying the Sun’s transition zone. This means that when the corona is undergoing a lot of solar activities and having a temperature greater than four times that, there must be something happening. This brings us to the second idea, Magnetic Reconnection.
Magnetic Reconnection
To help explain such a phenomenon, astronomers have formed another hypothesis called magnetic reconnection. This occurs when pockets of magnetism in the Sun’s plasma, known as magnetic domains, connect and release a ton of energy. As the magnetic fields line up here, everything essentially points in the same direction.
On the Sun, the plasma that is swirling around allows magnetic domains to come into contact with each other in an especially strange manner. Usually, when magnetic fields combine, we are able to predict the outcome. But this is not the case with magnetic reconnection as there are unaccountable bending and stretching to throw off our calculations. These are mainly caused by factors such as the Sun’s rotation and the perpetually moving plasma which constantly changes the system; we are not even able to grasp it entirely.
Fortunately, one thing we do know is that when two magnetic domains that are lined up in opposite directions collide, they annihilate each other and release huge amounts of heat energy which could possibly be the source of the corona’s high temperature.