RECENTLY, I was giving a tour of the University of New Hampshire’s department of physics and astronomy to a guest who isn’t a scientist. Among the many questions he asked was: “How does this stuff show up in the real world?” The kind of stuff I do, I explained, is mostly just knowing things for the sake of our big-picture understanding of the universe and our place in it.
Later, I realised I had made a mistake in not giving a practical example based on the class I am teaching, an introduction to stellar astrophysics. The topic can seem as esoteric as it gets, because what use could we possibly have for equations that describe the structure and evolution of stars?
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The first answer to this is that almost every element in the periodic table is made in stars, star deaths, stellar remnants (what is left after a star dies) and collisions between stellar remnants.
But there are more practical considerations: understanding our local star is essential for our electricity-dependent world. Space weather is a very real phenomenon that can have serious consequences for our electrical grids. In March, Mpho Tshisaphungo, head of space weather for the South African National Space Agency (SANSA), a forecast for a coronal mass ejection (CME) that could disrupt electrical grids.
A CME with relevance to Earth occurs when the sun’s atmosphere spits out plasma (a sea of charged particles acting in concert), leading to magnetic fields being stretched out to the point of interacting with our planet’s magnetic field. These temporary changes to Earth’s magnetic field can disrupt satellites, radio transmissions and electrical transmission lines, with the potential to damage power distribution facilities.
Tshisaphungo and his team originally forecast a mild CME; in actuality, the storm ended up being more extreme. This discrepancy isn’t a failure on SANSA’s part, but rather a sign of how research into stellar structure and evolution has significant practical importance. Predicting and protecting the grid from harm requires monitoring the sun and using mathematical models to predict what it might do next.
In a past column, I talked about the importance of using observational tools like NASA’s GOES satellite network to monitor solar activity. While such tools provide essential data about the sun’s current status, they don’t explain exactly how solar phenomena influence Earth’s magnetic field. This is where theorists come in, to try to figure out the mechanisms through which CMEs affect our planet’s magnetic field and the region of space where it is typically the dominant magnetic field, the magnetosphere.
It is worth pausing to say that, yes, Earth is a giant magnet! But it is a weak one. A refrigerator magnet is about 200 times stronger than the geomagnetic field that reaches from Earth’s interior out into space beyond the atmosphere. This magnetosphere has a dynamic relationship with our atmosphere: they affect one another. Because of its electromagnetic properties, the magnetosphere changes how charged atomic ions behave, and there is a layer of the upper atmosphere called the ionosphere that is comprised entirely of ions.
Clearly, we have a big picture sense of what it means for the ionosphere and magnetosphere to interact and affect one another. But the devil is in the details. We know they create an environment where winds of charged ions form. Today, scientists actively work on trying to explain how ionised hydrogen and oxygen are accelerated in these winds, because understanding this behaviour can provide insight into the exact mechanisms of ionosphere-magnetosphere interactions, as well as how space weather like CMEs affects them.
at Al-Quds University in Palestine has proposed a promising model based on an idea known as wave-particle interactions (WPIs). Despite the name, this isn’t a quantum mechanical idea. Instead, WPIs look at how particles like ionised hydrogen or oxygen behave when they are in a bath of plasma waves. Various researchers have explored WPIs in relation to the acceleration of hydrogen and oxygen ions.
Barghouthi and his team have added their own twist to this idea, suggesting it is important to correctly model how the particles spread out by showing that this spread is dependent on their speed. In a 2008 paper, Barghouthi used computer simulations to demonstrate that his model fitted the data better than other models did. Of course, this isn’t the end of the conversation, but it is work like this that brings stellar astrophysics into the real world and helps us all live better under the gaze of our occasionally messy sun.
Chanda’s week
What I’m reading
Robin Bernstein’s Freeman’s Challenge: The murder that shook America’s original prison for profit.
What I’m watching
I’ve been catching up on Coronation Street.
What I’m working on
Learning about applications of astrophysics and electromagnetism by reading some of Imad Barghouthi’s papers.
Chanda Prescod-Weinstein is an associate professor of physics and astronomy, and a core faculty member in women’s studies at the University of New Hampshire. Her most recent book is The Disordered Cosmos: A journey into dark matter, spacetime, and dreams deferred
