The moon exerts a previously unknown tidal force on the “plasma ocean” surrounding Earth’s upper atmosphere, creating fluctuations that are similar to the tides in the oceans, a new study suggests.
In the study, published Jan. 26 in the journal Nature Physics (opens in new tab) , scientists used more than 40 years of data collected by satellites to track the minute changes in the shape of the plasmasphere, the inner region of Earth’s magnetosphere, which shields our planet from solar storms and other types of high-energy particles.
The plasmasphere is a roughly doughnut-shaped blob of cool plasma that sits on top of Earth’s magnetic field lines, just above the ionosphere, the electrically charged part of the upper atmosphere. The plasma, or ionized gas, in the plasmasphere is denser than the plasma in the outer regions of the magnetosphere, which causes it to sink to the bottom of the magnetosphere. The boundary between this dense sunken plasma and the rest of the magnetosphere is known as the plasmapause.
“Given its cold, dense plasma properties, the plasmasphere can be regarded as a ‘plasma ocean,’ and the plasmapause represents the ‘surface’ of this ocean,” the researchers wrote in the paper. The moon’s gravitational pull can distort this “ocean,” causing its surface to rise and fall like the ocean tides.
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The moon is already known to exert tidal forces on Earth’s oceans, crust, near-ground geomagnetic field and the gas within the lower atmosphere. However, until now, nobody had tested to see if there was a tidal effect on the plasmasphere.
To investigate this question, the researchers analyzed data from more than 50,000 crossings of the plasmasphere by satellites belonging to 10 scientific missions, including NASA’s Time History of Events and Macroscale Interactions during Substorms (THEMIS) mission. The satellites’ sensors are capable of detecting minute changes in the concentrations of plasma, which allowed the team to map out the exact boundary of the plasmapause in greater detail than ever before.
The satellite crossings occurred between 1977 and 2015, and during this period, there were four complete solar cycles. This information allowed the team to factor in the role of solar activity on Earth’s magnetosphere. Once the sun’s influence was accounted for, it started to become clear that fluctuations in the shape of the plasmapause followed daily and monthly patterns that were very similar to the ocean’s tides, indicating that the moon was the most likely cause of the plasma tides.
The researchers are unsure exactly how the moon causes the plasma tides, but their current best guess is that the moon’s gravity causes perturbations in Earth’s electromagnetic field. But further research is needed to tell for sure.
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The team thinks this previously unknown interaction between Earth and the moon could help researchers understand other parts of the magnetosphere in greater detail, such as the Van Allen radiation belts, which capture highly energetic particles from solar wind and trap them in the outer magnetosphere.
“We suspect that the observed plasma tide may subtly affect the distribution of energetic radiation belt particles, which are a well-known hazard to space-based infrastructure and human activities in space,” the researchers wrote. Better understanding the tides could therefore help to improve work in these areas, they added.
The researchers also want to see if plasma in the magnetospheres of other planets is influenced by those planets’ moons. “These findings may have implications for tidal interactions in other two-body celestial systems,” they wrote.
Donald Trump’s Middle East envoy has met Israel’s prime minister in an effort to secure a ceasefire deal in Gaza before the president-elect takes office on 20 January.
Benjamin Netanyahu’s office confirmed details of the meeting with Steve Witkoff on Saturday, adding that the head of the Israeli Mossad intelligence agency has been deployed to Qatar in order to “advance” talks.
It was not immediately clear when David Barnea would travel to Doha for the latest round of indirect discussions between Israel and Hamas.
Earlier on Saturday, an Israeli official said some progress had been made, mediated by Egypt, Qatar and the United States, to reach a deal in Gaza.
The mediators are making renewed efforts to halt fighting in Gaza and free the remaining Israeli hostages held there before Mr Trump takes office.
A deal would also involve the release of some Palestinian prisoners held in Israeli jails.
Families of Israeli hostages welcomed Mr Netanyahu’s decision to dispatch the officials, with the Hostages and Missing Families Forum Headquarters describing it as a “historic opportunity”.
Mr Witkoff arrived in Doha on Friday and met the Qatari Prime Minister Sheikh Mohammed bin Abdulrahman Al Thani, Qatar’s foreign ministry said.
Egyptian and Qatari mediators received reassurances from Mr Witkoff that the US would continue to work towards a fair deal to end the war soon, Egyptian security sources said, though no further details were released.
Israel launched its assault on Gaza after Hamas fighters stormed across its borders in October 2023, killing 1,200 people and taking more than 250 hostages, according to Israeli figures.
Families of the roughly 100 hostages still held in Gaza are pressing Mr Netanyahu to reach a deal to bring their loved ones home.
Since then, more than 46,000 people have been killed in Gaza, according to Palestinian health officials, with much of the area destroyed and gripped by a humanitarian crisis, with most of its population displaced.
Pope Francis has been honoured with America’s highest civilian award by President Joe Biden, who has described the pontiff as “a light of faith, hope, and love that shines brightly across the world”.
It is the first time Mr Biden, 82, has given the Presidential Medal of Freedom with Distinction during his four years in office.
In a statement, the White House said the award is “presented to individuals who have made exemplary contributions to the prosperity, values, or security of the United States, world peace, or other significant societal, public or private endeavours”.
Mr Biden had been scheduled to present the medal to Pope Francis, 88, in person on Saturday in Rome on what was to be the final overseas trip of his presidency. But the president cancelled his visit to monitor the California wildfires.
The White House said Mr Biden bestowed the award during a phone call in which they also discussed efforts to promote peace and alleviate suffering around the world.
The award can be presented with or without distinction.
Mr Biden presented the medal of freedom – without distinction – on 5 January to several people including fellow Democrat Hillary Clinton, humanitarian and U2 singer Bono, fashion designer Ralph Lauren and actors Michael J Fox and Denzel Washington.
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Mr Biden himself is a recipient of the award with distinction, recognised when he was vice president by then president Barack Obama in a surprise ceremony eight years ago.
The citation for the pope’s honour said his “mission of serving the poor has never ceased”.
“A loving pastor, he joyfully answers children’s questions about God. A challenging teacher, he commands us to fight for peace and protect the planet. A welcoming leader, he reaches out to different faiths,” it added.
And so now it is certain. Alice Weidel will lead her far-right party into Germany’s general election next month.
She was overwhelmingly backed at the Alternative for Germany (AfD) conference and was greeted with a standing ovation.
Weidel will fight the election with a manifesto that follows a familiar pattern from other successful populist campaigns in Europe and beyond – contempt for mainstream politicians, anger over levels of irregular immigration, a desire to rein in the power of the European Union and dismay over the spread of so-called woke values.
“Thank you for your trust,” she told the audience.
“I am excited to lead our campaign. For our people, for our future.”
Who is Weidel?
Weidel is an unusual figure to lead a German hard right-wing party – a gay woman with a PhD in economics, a Sri Lankan partner, two children and a home in another country – she commutes from Switzerland.
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Admittedly there is an awkward history – her grandfather was a Nazi judge appointed to the job personally by Adolf Hitler, but she has maintained that she did not know that fact growing up and has angrily distanced herself from accusations of racism.
Indeed, Ms Weidel maintains that her party is not on the far right, but is simply conservative.
And that is part of her attraction – she is perceived as uncompromising on the things that the AfD’s supporters hold dear – migration, Euroscepticism, the greatness of German culture – but she’s also perceived as more palatable to the wider public.
Or, at least, that’s the idea.
Thousands of protesters
Outside the sports centre, where the AfD’s convention was being held, thousands of protesters gathered to raise their fears that the country was going back to the politics of the past.
“They are fascists,” said a man called Gabriel, who was helping to blockade the road that ran past the venue.
“I don’t know if we have learnt anything in the past hundred years but now we do have to stand against fascism.”
Many of the delegates would angrily decry that label.
His grouping, Der Flugel, was declared a suspected extremist organisation but he remained the party’s leader in Thuringia.
In 2019, a court ruled that it was not libellous to refer to Hocke as a fascist.
He has twice been found guilty of using Nazi slogans but last year, under his leadership, the AfD won the state election.
Emotions often run high when the AfD is involved. The protests here were, at times, heated.
Police had to clear the road in front of Ms Weidel’s car as some protesters sat down and others began to surround it.
Later, the party’s MPs were called to gather together for a sudden security briefing.
The sports centre where this meeting was held once hosted the World Sumo Wrestling Championship.
Here, the heavyweights were political, and the prize at stake was far more consequential.
Barring a quite astonishing movement in the polls, the AfD is unlikely to win the election next month, but the party may well come second with more than 20% of the vote.
That probably won’t equate to power – Germany’s major parties have all said they won’t go into coalition with the AfD – but it will mean momentum.
It will mean a loud voice in the Bundestag, the German federal parliament, and the ability to pressure the next chancellor into reflecting the opinions of the millions who vote for Ms Weidel’s vision.
Long term, if Ms Weidel can prove that her party is palatable, as well as popular, then she knows the political dam will one day break.
If enough people back the AfD, it will eventually become impossible to shun the party forever.