Living Inside the Sun

The news from THEMIS last time caught my attention, why? Because that would change on we look on the solar wind. I will not dwell much on the finding, but in brief, if previously thought, that when the sun’s magnetic field is aligned with that of the Earth, the shield is up and that few if any solar particles enter Earth’s magnetic shield. Oppositely, the shield is down when the solar magnetic field direction points opposite to Earth’s field, leading to more solar particles inside the shield. But this no longer the case because of recent observations by the THEMIS spacecraft fleet demonstrate that the opposite is true.

But, what is it? The wind with magnetic field? The wind from the Sun? If one have to ponder alot about this subject that should be them who works on the field of Solar Physics, as i have to be learn for something from the finding.

Nonetheless, let’s go to the basic. What is the Solar wind? Maybe we immediately compare to the usual wind like we know in our daily life. To some degree that is true. Wind is the flow of air molecule because of pressure gradient force. If on one point the pressure is different from the other, then the air tends to flow from point to point from the higher pressure region to the lower. That is the simplest idea about the wind, at least as i recall vividly from my elementary school. Sometimes i wonder how that even elementary school study still relevant to the study of solar physics. And to some degree that would be still relevant to the Solar Wind.

But, how do we measure the ‘Solar wind’? How do we know the pressure difference between near earth & near Sun? Can someone go near the Sun & measure the pressure there? Long-long time ago, when people observe the comets, when they appear, when they go to approaching the Sun, the tail always follow the head, but the opposite happen, when the comet go away from the Sun, the comets go with the tail first, followed by the head. How does that happen?

Btw, before continue, there is the Lulin comet approach us soon, it would be great to observe it if possible!

Now, back to the comet conundrum, around 1600s, Johannes Kepler proposed that the pressure of sunglight pushes the comet tails away from the Sun. It took years, and until the 20th century that the term Solar wind become accepted, after years and years of study, observation, analysis, and learn that instead of empty space around the Sun, the Sun continuously blowing itself away, filling the environment with flow of matter, the Solar wind. In fact, actually we live inside the Sun, because the sphere of the Sun that we know is merely a limit when finally the light can escape freely to the space.

So the term Solar wind, is the stream of particles emitted by the Sun, but not just the as simple as the wind that we know in our Earth, because of so extreme conditions in the Sun, so the atoms & molecules torn apart from their natural state, instead we will find electrons and protons as the most constituent of the Sun, we call it plasma. Basically, the Sun (as with all the stars in the universe) is merely giant hot ball of plasma. And the Solar wind is a stream of the plasma.

To add  more complexity, because of every particle int he plasma is charged, therefore electrically conducting, and that would meen when it moves will generate magnetic fields. That imply that the Solar wind carries with it the magnetic field lines! This will lead us to the prior questions.

The Sun is a big magnet. Earth has a magnetic field, too, but the Earth’s magnetic field is 100 times weaker than the Sun. As the solar wind carries the magnetic field away from the Sun, it might hit the planets, like our Earth. Thanks to our magnetic field, that shield us from the gale. Otherwise the destiny of the Earth would be like Mars, because Mars does not have sufficient protective magnetic shield (the magnetosphere). And so the live on Earth has been exist for thousands and thousands years, disregard of continuous bombardment from the Sun, because of the magnetosphere protection.

Like the magnet bar that we know, that always north-south direction (dipole), so does the interatction between the Sun magnetic field & Earth magnetic field. As the magnetic stream from the Sun come into contact with Earth’s magnetic field at the place called the magnetpouse, sometimes the incoming the magnetic direction points south, sometimes to the north. As for Earth’s magnetic field always points north at the magnetopause. The prior to the finding, most believe that when the incoming magnetic field points south, that can cancel the Earth’s magnetic field at the point of contact, and for the people in the northern/southern latitude will see the auroras – as the Solar wind able to inject energetic particles into the magnetosphere (to be honest i never seen aurora directly in the sky). As the new finding from THEMIS shows that instead when the opposite happen, the case will be stronger.

In brief, the solar wind is a stream of plasma—ejected from the Sun. These particles are able to escape the Sun’s gravity, thrown freely in the space, and to some point can interact the neighbouring planets. That does not mean that the Sun is the sphere of gas that we seen daily, because actually the space in between the planets is not an empty space. It is always filled with the plasma streamed out from the optically opaque spherical shape, and the planets like the Earth as it moves around the Sun, interact with the wind, just like a ship in the ocean, cannot escape the wind as it blows away. Surely we live inside the Sun.

Lastly, how can be the Sun continuously blow its material away as the wind? Shouldn’t be the Sun depleted its material someday because of that? Where is exactly the wind started, is it from inside? Or somewhere else? I will return later. (to be continued)