An incredible number of factors and variables have led to the planet we live on today, where life has found a way to survive and even thrive in the most marginal conditions. The Sun is the catalyst for all of this, and thanks to its stable synthesis, it directs life towards a more complex structure.

But the Sun is only soft because of the Earth’s built-in protection, the magnetosphere. Both the Sun and the magnetosphere changed over time, and the power of each diminished. The sun influences strong space weather and the magnetosphere protects the Earth.

How did these two events affect Earth’s habitability?

A new study examines how the magnetic shield of the Sun and Earth has changed over time and how these changes affect the habitability of our planet. Its title: “On the Habitability of Earth in the Sun’s Main Sequence: The Joint Effect of Space Weather and the Evolution of the Earth’s Magnetic Field.” The lead author is Jacobo Varela, a researcher at the Carlos III University of Madrid. The article will be published on: Monthly Notices of the Royal Astronomical Society and is currently available on the preprint server arXiv.

We know much more about the Sun than we did a few decades ago. The Parker Solar Probe, Solar and Heliospheric Observatory (SOHO), Solar Dynamics Observatory (SDO) and other spacecraft are currently working intensively on this issue. We know that the Sun has an 11-year cycle and sometimes emits powerful solar storms that can disable electrical equipment on Earth.

We also know a lot about Earth’s magnetosphere. We know that the planet’s rotating iron core and its convection currents form a protective magnetic shield that blocks much of the sun’s dangerous radiation while allowing heat to pass through. We know that the Earth’s poles can change and the strength of the magnetosphere can change over time.

How did all these factors affect Earth’s habitability?

The solar wind (SW) and interplanetary magnetic field (IMF) together create space weather, and habitability depends on how space weather interacts with our magnetosphere. Without a strong magnetosphere, the Earth is vulnerable.

“This means that weather conditions in space can impose limits on the habitability of Earth and exoplanets with respect to the protection provided by planetary magnetospheres, avoiding the sterilizing effect of the stellar wind on the surface,” the authors explain.

Coronal mass ejections (CMEs) have the most destructive impact on Earth’s magnetosphere. When the Sun emits a powerful CME that hits the Earth, it temporarily deforms the Earth’s magnetosphere. The day side is compressed and the night side is expanded. In most cases, this only results in stronger auroras, a natural light show that reaches lower latitudes than normal.

But it’s a balancing act that isn’t always balanced. Earlier in its history, the Sun rotated faster and had stronger magnetic activity. Because CMEs are driven by the sun’s behavior, including rotation and magnetism, the sun has produced stronger CMEs in the past. “The dynamic NE pressure and the intensity of the IMF were much higher in the early stages of the Sun’s main sequence than today, so the perturbations caused by the young sun in the Earth’s magnetosphere were stronger,” the authors write. “

The question is; How exactly did all of this change over time and how did it affect livability? How will this affect him in the future?

“The aim of this study is to analyze the habitability of the Earth in the main sequence during the evolution of the Sun,” the authors explain. The team ran a series of detailed simulations to explore the interaction between the Sun and Earth over billions of years of history. The modeling is based on established scientific models of factors such as software strength over time.

One thing that changes over time is the strength of the Earth’s magnetic field, measured in microtesla. Recent data show that it varies over a 200-million-year cycle. The changes result from changes within the Earth from which the field was created.

The authors examined how Earth’s habitability changes during periods when the dipolar magnetic field is weak, normal, and high intensity. There were periods when not only the density of the Earth but also the nature of its magnetic field changed. There are sometimes periods when the Earth’s magnetic field is multipolar rather than bipolar. The strength of the field also changes at this time, and when it is weak the field may change.

The figure below shows some of the data used in the simulation. The team used models for four different ranges of Earth’s magnetic field strength. These are shown in two columns labeled “Dipole” below the Paleomagnetic Data column and the World Field Model column B. The Earth experienced low field strengths during the Proterozoic Eon and during the Cambrian, Denian, and Carboniferous periods of the Paleozoic Era. There was also a low areal density during the Triassic period in the Mesozoic. These times correspond to models with only 5 microteslas, shown in red.

Slightly stronger 15 microtesla periods occurred in the Paleo-Archaean and Meso-Archaean epochs, the Proterozoic Eon, the Jurassic in the Mesozoic epoch, and the Paleogene in the Cenozoic epoch. They are shown in orange below the dipole columns.

“The 30 μT dipole model illustrates the Meso-Proterozoic and Neoarchaean periods, as well as the Neogene and Quaternary periods of the Cretaceous period,” the authors explain. These times are shown in pink.

The Earth’s magnetic field was strongest in early times. “The 45 μT dipole model represents high-field periods in the Hadean Eon and Eo-Archaean,” the authors write. They are shown in purple.

So what does all this mean?

An important part of this study is the magnetopause distance. This distance is compressed by more energetic solar winds and widens when the Earth’s magnetic strength is higher. In the above figure, (a) has a significantly shorter magnetopause distance than (d) when the magnetic field strength is higher.

In times of strong solar winds and weak magnetism, the magnetopause distance is closer to the Earth’s surface, meaning that the Sun poses a threat to life. If this distance decreases to zero, that is, if solar radiation can fall directly on the surface, then the habitability of the Earth will decrease significantly.

“We conclude that the impact of space weather on Earth habitability should be considered an important factor in the evolution of the atmosphere and life,” the authors write. (Note that the authors are not native English speakers and their syntax reflects this. Still, the meaning is clear.)

The study shows how space weather and the strength of the Earth’s magnetic field change over time and facilitate or hinder habitability. This suggests that we are more sensitive to space weather, especially when the Earth was in a multipolar configuration before the poles changed. The last pole shift occurred about 780,000 years ago and the magnetic shield weakened. Cancellation can take hundreds or even thousands of years. We are still protected during flashbacks, but not as much. If a strong CME attacks at this time, it could trigger a strong geomagnetic storm.

In the distant future, Earth’s dipole will weaken. Its geodynamo will fade just like it did on Mars. The planet’s ability to withstand solar radiation will decrease and it will no longer be suitable for life. Eventually successive ICMEs will rise to the surface and damage Earth’s biosphere. Eventually even a relatively weak solar wind will reach the surface, and the Earth will be constantly bathed in radiation.

But so far we’re good. Little by little, without help, we can continue our work, making the Earth uninhabitable. Source