by
Martin Leduc
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A huge solar flare was discovered on Friday, October 4, 2024. “It is the largest in years,” astrophysicist Eric Lagadique commented on Saturday, October 5 and Sunday, October 6, 2024.
In the end, it appears that the warning “did not do much.” But it could rise againactu.frGilles Davidovich, Vice President of the French Astronomical Society (SAF).
From the moment you see the northern lights, it must be dark by the hour actu.frwe thought it might be interesting for readers to find out for themselves whether there would actually be a sight to watch over their homes at night. There are many websites out there, and if the data you are referring to seems barbaric, don't panic, we will explain everything. Tutorial.
It is very difficult to predict
First of all, it is important to go back to what the Northern Lights are.
Concretely, it is the interaction between molecules in the solar wind and the Earth's upper atmosphere. Basically, the Sun sends out a wind of particles, which, if they meet the Earth at the right time and in the right place, cause a whole series of physical phenomena. Including the northern lights.
If you say so, it sounds simple and easy to predict. But this is not really the case. “There are countless events that can disrupt the good functioning of the northern lights,” says Jill Davidovich.
Until now, we don't know how to accurately predict solar flares. We know how to detect it, but we don't expect it.
Hence, one factor that plays a role in the northern lights is the speed of the solar wind. Other than that, to find out, we're only using about a dozen satellites, including Solar Orbiter, SoHO, and even Proba-3, which are supposed to depart in the coming months.
They work a bit like car radars and pick up speed when you pass in front of them. But at the back it can slow down completely. If you slow down, your chances of seeing the northern lights decrease.
This is just one of the parameters that must be taken into account. In short, suffice it to say that it is difficult to accurately predict these giant green and red curtains. “We will know two or three hours in advance whether there will be an aurora,” Fabrice Motez, editor-in-chief of the journal Astronomy and researcher (CNRS) at the Paris Observatory, explained in a previous article.
So how do you know?
From the moment it gets dark, start going to the site SpaceWeatherLive.com. The latter provides, in real time, meteorological information about space and especially about our Sun.
Obviously, many other sites on the Internet provide this type of information. But this is what Gil Davidovich recommended. From the home page, we are interested in two pieces of information: the KP index and the solar wind speed.
the Solar windIt is a cloud of particles expelled by the sun. Their speed can be increased by coronal mass ejections, or solar flares, for short. KB indexFor its part, it is a measure of the Earth's geomagnetic activity. It is used to measure disturbances to the Earth's magnetosphere caused by solar wind, in particular solar flares or coronal mass ejections.
On SpaceWeatherLive.com, these two data are displayed in large format, at the top left.
“If the KP is at 7, it doesn't mean there will be some things, but we are likely to see some,” says the SAF deputy chief.
There is also the speed of the solar wind that comes into play.
When they accelerate, they are what bring a flow of particles that interact with the upper atmosphere. So, if the speed is 400 km/s, that's good. On the other hand, at 900, we catch a wave. Here again the opportunities increase.
For us, in France, there is no chance of seeing the northern lights if the KP index is not less than 7, and if the solar wind speed is not less than 700 km/s.
As mentioned above, it also has to be dark, “otherwise we wouldn't see anything, even if they were there,” smiles Gil Davidovich.
The last “simple” parameter to take into account: this famous solar wind must be in the right direction. The Earth rotates around its axis. So, if the solar wind reached the other side of the Earth, we would have nothing to eat. Ditto if the magnetic field is not directed properly.
You will understand that you cannot expect the northern lights to perform well. She notices herself. This is where apps, like My Aurora Forecast, can come in handy, allowing you to see supporting data, maps and webcam in real time.
If the data indicates that there may be northern lights, what do we do?
If it's night, and the data is exciting, you should leave the house. Above all, do not waste time: the northern lights can last for several hours or several seconds.
Find a place away from light pollution, hope the weather is clear (this is a no-brainer), look north, and be patient. “You have to want to see the northern lights,” concludes Gil Dawidosis.
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