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.
Sir Keir Starmer was at home in Downing Street, watching Arsenal lose in the Champions League, when he got a call from Donald Trump that he thought presented the chance to snatch victory from the jaws of trading defeat.
The president’s call was a characteristic last-minute flex intended to squeeze a little more out of the prime minister.
It was enough to persuade Sir Keir and his business secretary Jonathan Reynolds, dining with industry bosses across London at Mansion House, that they had to seize the opportunity.
The result, hurriedly announced via presidential conference call, is not the broad trade deal of Brexiteer dreams, and is certainly not a free-trade agreement.
It’s a narrow agreement that secures immediate relief for a handful of sectors most threatened by Mr Trump’s swingeing tariffs, with a promise of a broader renegotiation of “reciprocal” 10% tariffs to come.
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‘A fantastic, historic day’
Most pressing was the car industry, which Mr Reynolds said was facing imminent announcements of “very difficult news” at Britain’s biggest brands, including Jaguar Land Rover, which sounds like code for redundancies.
In place of the 25% tariffs imposed last month, a 10% tariff will apply to a quota of 100,000 vehicles a year, less than the 111,000 exported to the US in 2024, but close enough for a deal.
It still leaves the car sector far worse off than it was before “liberation day”, but, with one in four exports crossing the Atlantic, ministers reason it’s better than no deal, and crucially offers more favourable terms than any major US trading partner can claim.
For steel and aluminium zero tariffs were secured, along with what sounds like a commitment to work with the US to prevent Chinese dumping. That is a clear win and fundamental for the ailing industries in Britain, though modest in broad terms, with US exports worth only around £400m a year.
Image: US and UK announced trade deal
In exchange, the UK has had to open up access to food and agricultural products, starting with beef and ethanol, used for fuel and food production.
In place of tariff quotas on beef that applied on either side (12% in the UK and 20% in America) 13,000 tonnes of beef can flow tariff-free in either direction, around 1.5% of the UK market.
The biggest wins
Crucially, sanitary and phytosanitary (SPS) production standards that apply to food and animal products, and prevent the sale of hormone-treated meat, will remain. Mr Trump even suggested the US was moving towards “no chemical” European standards.
This may be among the biggest wins, as it leaves open the prospect of an easing of SPS checks on trade with the European Union, a valuable reduction in red tape that is the UK’s priority in reset negotiations with Brussels.
Farmers also believe the US offers an opportunity for their high-quality, grass-fed beef, though there is concern that the near-doubling of ethanol quotas is a threat to domestic production.
Technology deals to come?
There were broad commitments to do deals on technology, AI and an “economic security blanket”, and much hope rests on the US’s promise of “preferential terms” when it comes to pharmaceuticals and other sectors.
There was no mention of proposed film tariffs, still unclear even in the Oval Office.
Taken together, officials describe these moves as “banking sectoral wins” while they continue to try and negotiate down the remaining tariffs.
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The challenge from here is that Mr Trump’s “reciprocal” tariff is not reciprocal at all. As commerce secretary Howard Lutnick proudly pointed out in the Oval Office, tariffs on US trade have fallen to less than 2%, while the UK’s have risen to 10%.
As a consequence, UK exporters remain in a materially worse position than they were at the start of April, though better than it was before the president’s call, and for now, several British industries have secured concessions that no other country can claim.
From a protectionist, capricious president, this might well be the best deal on offer.
Quite what incentive Mr Trump will have to renegotiate the blanket tariff, and what the UK has left to give up by way of compromise, remains to be seen. Sir Keir will hope that, unlike the vanquished Arsenal, he can turn it round in the second leg.
Donald Trump has a soft spot for military spectacles and autocrats.
He will be looking on with envy as Vladimir Putin parades both in Moscow today, with Chinese leader Xi Jinping flying in to join Victory Day events in Red Square.
European allies of Ukraine will be watching nervously, wary of anything that could upturn the delicate quest for peace.
President Trump‘s patience with peddling his much vaunted “peace deal” has been wearing thin and allies had feared Ukraine could be punished for it.
That would have been grotesquely unfair, of course. Ukraine has bent over backwards to accommodate Mr Trump’s one-sided diplomacy that has so far seemed to favour the aggressor in this obscene war.
Image: Pic: AP
True, the Trump proposal does not agree to Russian annexation of all the land already taken by force and stops short of ordering the complete demilitarisation of Ukraine, but otherwise the proposals are pretty much everything that Moscow has asked for.
The deal is being pushed by Steve Witkoff, Mr Trump’s golf partner turned chief negotiator, a man regarded by diplomats as out of his depth and lost in the rough when it comes to the arts of statecraft.
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Like his president, Mr Witkoff has a history of doing business with Russian oligarchs, an apparently starry-eyed view of the Russian leader and has called Ukraine a “false country”.
Moment of truth approaching
Mr Witkoff and Mr Trump have so far given Mr Putin the benefit of the doubt, but a moment of truth is approaching. While Ukraine has agreed to a longer ceasefire in principle, Mr Putin will not.
Ukraine’s European allies feared that Mr Trump was about to despair of progress, blame Ukraine and take US military support with him.
Then came the minerals agreement between the US and Ukraine. The breakthrough gave the US president something to show for his efforts and assuaged his desire for some kind of deal. He seems to have moved on for now, at least, and approved the first $50m of arms sales to Ukraine.
Image: Members of the Russian Air Force fly over Red Square during the rehearsal. Pic: AP
But these remain a tense few days ahead with plenty at stake.
The Russian lull is seen here in Kyiv as little more than a ploy.
If the Russian leader was serious about giving peace a chance, they say, he would have signed up to the permanent ceasefire being proposed by the Trump team.
Besides, Russia broke the last truce in Easter as soon as it had begun and used it to carry out surveillance and reinforcement operations says Kyiv. Why risk another pointless pause that is exploited by the invaders?
Escalation possible
If Russia plays the same games this time and Ukraine retaliates, there could be a significant escalation. Likewise, with any Ukrainian drone attack on Moscow during Victory Day.
Any major flare-up will not be looked on favourably by the US president if it upstages his first trip abroad this presidency, a three-day tour of the Middle East.
For now, his attention is not so much on the Ukraine conflict and he is no longer issuing threats to walk away and stop supporting the Ukrainians.
Image: Russian servicemen march towards Red Square in the rehearsal. Pic: AP
On Wednesday, India said it hit nine “terrorist infrastructure” sites, while Pakistansaid it was not involved in the April attack and the sites were not militant bases.
Pakistan’sPrime Minister Shehbaz Sharif has since vowed that India will “now have to pay the price” for their “blatant mistake,” and skirmishes have also been reported along the Line of Actual Control (LAC).
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Speaking to Sky’s The World with Yalda Hakim on Thursday, India’s high commissioner to the UK, Vikram Doraiswami, said “the original escalation is Pakistan’s sponsored terror groups’ attack on civilians”.
India strikes ‘reasonable,’ says high commissioner
He then insisted India’s strikes in Pakistan and Kashmir were “precise, targeted, reasonable and moderate,” adding: “It was focused principally and solely on terrorist infrastructure.
“We made it abundantly clear that the object of this exercise was clearly to avoid military escalation.
“A fact that was actually acknowledged – in a left-handed way of course – by the Pakistani side in terms of their own statements, which said the airspace hadn’t been violated.”
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India awaits Pakistan’s response
Pakistan chose ‘to escalate the matter’
The high commissioner also said about claims Pakistan shot down Indian aircraft with Chinese-made fighter jets: “If it satisfies Pakistan’s ego to say that they’ve done something, they could have used that as an off-ramp to move on.
“Clearly they’ve chosen not to, and they’ve chosen to escalate the matter.”
Image: A boy collects papers from the debris of a damaged house in Gingal village. Pic: Reuters
And when asked about Pakistan’s threats of retaliation, Mr Doraiswami said: “We’re not looking for an escalation, but if Pakistan responds, as we have done, we will respond proportionally and in exactly the same light.”
He then referenced the border skirmishes, saying: “I do want to remind everybody: For the last 15 days, they’ve also opened artillery fire along the Line of Actual Control… That’s led to civilian casualties.”
It comes after India said Pakistan attacked its military stations in the Kashmir region with drones and missiles on Thursday.
The country’s defence ministry said stations at Jammu, Pathankot and Udhampur were “targeted by Pakistani-origin” weapons, and added “the threats were swiftly neutralised”.