<p>Since atmospheric retention is largely dependent on escape velocity and temperature, removal of the Earth's magnetic field should not have a greatly noticeable effect, as current research shows that Earth's magnetic field changes the location of atmosphere loss due to the solar wind rather than eliminating it.  Earth's temperature is not likely to change much without a magnetic field (with the current solar luminosity), so that too can be discounted.</p>

<p>It is far more likely that Earth's atmosphere will diminish as a result of increasing temperature as the sun expands due to an increase in helium fusion as it runs out of hydrogen, a phenomenon that would not be dependent on having or not having a magnetic field.  That would be in roughly 5 to 7 billion years according to the <a href="http://en.wikipedia.org/wiki/Future_of_the_Earth">Atmospheric Escape</a> and the <a href="http://en.wikipedia.org/wiki/Formation_and_evolution_of_the_Solar_System#Timeline_of_Solar_System_evolution">Formation and evolution of the Solar System </a> Wikipedia articles.</p>

<p>If we discount solar expansion and make the convenient but incorrect assumption that solar wind and temperature will remain constant over time, then it is possible that Earth's atmosphere could be stripped in a timeframe on the order of many trillions of years.  See the <a href="http://en.wikipedia.org/wiki/Atmospheric_escape">Atmospheric Escape</a> Wikipedia article, and this <a href="http://www.space.com/11187-earth-magnetic-field-solar-wind.html">How Vital Is a Planet's Magnetic Field</a> Space.com article.</p>

CC BY-SA 3.0
2015-10-10T19:32:53.277Z
@MontyWild The key quantities are the total size of the atmosphere (Venus's is 90 times Earth's), escape velocity (Venus about equals Earth), the molecular weights in the atmosphere (Venus with CO2, ~44, and SO2, ~64; Earth with N2, ~28, O2, ~32, and Ar, ~40), the temp at the **exobase** (top) of the atmosphere which can be very different from the surface temp, the portion of atomization and ionization at the exobase, and the strength of magnetic **flux** (not field) at the exobase.
Eubie Drew
CC BY-SA 3.0
2014-04-22T23:22:36.257Z
Given that Venus does not have much of a magnetic field, has lower gravity and a higher temperature, and is closer to the sun where solar wind effects would be greater, and still has a very thick atmosphere presumably billions of years after its formation, I would say that solar wind effects would not be terribly significant at these distances on an object of sufficient size.
Monty Wild
CC BY-SA 3.0
2014-04-22T23:28:05.693Z
That could be, I was specifically commenting on the suggestion that influx would equal outflux.  The mass flux of the solar wind is insignificant.  There is a net outflow of both hydrogen and oxygen from the Earth's atmosphere, fortunately there's a vast reservoir in the crust and oceans, so it's not a practical problem (for example, see [Slapak (2013)](http://pure.ltu.se/portal/files/42434406/Rikard_Slapak.pdf)).  The question is, how much more would it be without a magnetosphere?
gerrit
CC BY-SA 3.0
2014-04-22T23:32:31.417Z
I didn't mean to suggest that solar wind effects were zero-sum, just that with the other considerations such as solar expansion, it was not particularly significant.  Note the `much` in `not likely to change much`
Monty Wild
CC BY-SA 3.0
2014-04-22T23:34:25.980Z
Ok.  Still, your answer remains unsourced, and it seems speculative, and therefore it is not very useful.  Some references to peer-reviewed literature would be highly valuable.
gerrit
CC BY-SA 3.0
2014-04-23T18:04:24.750Z
Because this is a budgets and rates question, I have to downvote this until numbers and sources are added.
tobias47n9e
CC BY-SA 3.0
2014-04-23T23:57:14.177Z
@Spießbürger, quite right.  Please note my edited answer including references.  It appears that my educated guesses weren't too far off, though.
Monty Wild
CC BY-SA 3.0
2014-04-24T05:18:24.510Z
@MontyWild But the question is about "how long will it take", not "when will it happen".
tobias47n9e
CC BY-SA 3.0
2014-04-22T23:06:45.007Z
2014-04-23T23:55:22.067Z
2014-04-23T23:55:22.067Z
Monty Wild
<p>Atmospheric escape is a topic with a long research history. It is complex and is being addressed with both measurements and simulations. </p>

<p>For example, the question of atmospheric escape is still actively researched at Mars, and the MAVEN (Mars Atmosphere and Volatile Evolution) spacecraft mission is for example dedicated to this topic. Mars is a planet without a significant global magnetic field (although it does possess crustal magnetic anomalies); in fact its planetary dynamo was active and then stopped about 3.6 billion years ago, which considerably reduced the strength of its magnetic field.<br>
So understanding the evolution of its atmosphere helps to relate to what would happen if Earth would loose its magnetic field. The question of atmospheric escape at Mars is relevant concerning the fate of water (geological evidences indicate the presence of liquid water in the past, which suggests a warm and dense atmosphere able to support it at that time).</p>

<p>Besides thermal atmospheric escape, there is also non thermal escape, including removal by asteroid impact (in the past) and by interaction between the atmosphere and the solar wind leading to pickup of atmospheric ions (in the past and continuing today).</p>

<p>Some examples of references to the scientific literature about atmospheric escape at terrestrial planets (abstracts):<br>
<a href="http://adsabs.harvard.edu/abs/2013SSRv..174..113L" rel="noreferrer">Outgassing History and Escape of the Martian Atmosphere and Water Inventory</a><br>
or<br>
<a href="http://adsabs.harvard.edu/abs/1996RvGeo..34..483S" rel="noreferrer">Nonthermal escape of the atmospheres of Venus, Earth, and Mars</a></p>

CC BY-SA 3.0
2014-04-30T23:55:10.207Z
2015-04-02T14:46:45.020Z
2015-04-02T14:46:45.020Z
CathD
<p>The Earth's magnetic field provides an important protection against the solar wind (for example, <a href="https://en.wikipedia.org/wiki/Earth%27s_magnetic_field#Importance">see Wikipedia on Earth's magnetic field</a> and references therein).  Mars may have lost its atmosphere because it did not retain such a magnetic field, although <a href="https://en.wikipedia.org/wiki/Venus#Magnetic_field_and_core">Venus does not have an intrinsic magnetic field either</a>.  This raises the question: what will happen to Earth's atmosphere if the global magnetic field would disappear?  Would the solar wind blow it all away?  If so, how long would it take until only a small part (&lt;10 kPa sea level pressure) is left?</p>

CC BY-SA 3.0
2014-04-22T18:26:48.357Z
Mars still has an atmosphere. It may be thinner now than previously though.
Siv
CC BY-SA 3.0
2014-04-22T19:29:15.390Z
The surface escape velocity of Mars is also lower than Venus or Earth.
winwaed
CC BY-SA 3.0
2014-04-22T20:14:19.230Z
thats a good point winwaed, but wouldnt the solar forces be stronger?
Neo
CC BY-SA 3.0
2014-04-22T20:25:00.840Z
“Size *does* matter.”
gerrit
CC BY-SA 3.0
2014-04-22T20:57:02.063Z
Difficult question: Measuring rates on Mars would be most comparable, but Mars probably also had 'atmospheric impact-erosion'. +The erosion probably happened faster, than changes in atmospheric screening (size of meteorite craters) can resolve. +Different magnitude of solar wind. I don't know of any numerical modelling, but that would probably give the best results for Earth.
tobias47n9e
CC BY-SA 3.0
2014-04-23T00:11:13.133Z
@Neo, with regard to Mars, the heavy isotope enrichment of the Martian atmosphere's hydrogen (rel. Earth) is taken as a sign of greater diffusion rate of H (vs Deuterium) due to the lower gravitational forces.
winwaed
CC BY-SA 3.0
2016-04-17T18:55:20.623Z
Forget trillions. The Sun is a Main Sequence star headed for red giant-hood (https://en.m.wikipedia.org/wiki/Red_giant) in less than 10B years. This event will blow away atmospheres and probably moon satellites of every planet inside the asteroid belt. Bye bye lunar tidal lock. Now the site wants me to ask a question! Or I get no points. What happens when Earth were to lose its magnetic field is not as interesting a question (it being way speculative) as what the evolution of our planet's magnetic field is actually moving toward. So here is what I ask: Is the long term magnetic field average i
GuestinArizona
CC BY-SA 3.0
2016-09-27T15:01:34.913Z
I always thought that the main protective effect of the magnetic field was the charged particles carried by the solar winds that would bombard and kill us, more than the stripping away of the atmosphere.
PoloHoleSet
CC BY-SA 3.0
2017-11-06T10:36:54.870Z
See also https://earthscience.stackexchange.com/questions/8845/what-is-the-characteristical-time-of-the-loss-of-the-earth-atmosphere-how-can-i
JeopardyTempest
CC BY-SA 4.0
2019-01-25T03:16:11.273Z
Related question https://earthscience.stackexchange.com/questions/14915/does-the-magnetic-field-really-protect-earth-from-anything/
Camilo Rada
CC BY-SA 4.0
2023-01-09T12:23:57.983Z
Wow this is crappy science.
No EMF would cause a cascade of megadisasters….and yes weather & temperatures change dramatically despite the author’s assertion. Last pole flip 42k years ago that caused a MASS EXTINCTION, that speaks louder than blogs. We’ve lost 50% of field strength in last 1,500 years & an extra 10% the last hundred…we are in the POLEFLIP NOW! https://youtu.be/tOUQz7BlX4c
Lots of charts, data in this video
PsychicX
<atmosphere><hypothetical><solar-terrestrial-physics><magnetosphere>
(How long) would Earth's atmosphere last without a global magnetic field?
gerrit
# (How long) would Earth's atmosphere last without a global magnetic field?

(Asked by: username_0 on 2014-04-22)

The Earth's magnetic field provides an important protection against the solar wind (for example, [see Wikipedia on Earth's magnetic field](https://en.wikipedia.org/wiki/Earth%27s_magnetic_field#Importance) and references therein). Mars may have lost its atmosphere because it did not retain such a magnetic field, although [Venus does not have an intrinsic magnetic field either](https://en.wikipedia.org/wiki/Venus#Magnetic_field_and_core). This raises the question: what will happen to Earth's atmosphere if the global magnetic field would disappear? Would the solar wind blow it all away? If so, how long would it take until only a small part (<10 kPa sea level pressure) is left?

**Tags:** atmosphere, hypothetical, solar-terrestrial-physics, magnetosphere

> **Comments:**
> **username_1**: Mars still has an atmosphere. It may be thinner now than previously though.  
> **username_2**: The surface escape velocity of Mars is also lower than Venus or Earth.  
> **username_3**: thats a good point username_2, but wouldnt the solar forces be stronger?  
> **username_0**: “Size *does* matter.”  
> **username_4**: Difficult question: Measuring rates on Mars would be most comparable, but Mars probably also had 'atmospheric impact-erosion'. +The erosion probably happened faster, than changes in atmospheric screening (size of meteorite craters) can resolve. +Different magnitude of solar wind. I don't know of any numerical modelling, but that would probably give the best results for Earth.  
> **username_2**: @username_3, with regard to Mars, the heavy isotope enrichment of the Martian atmosphere's hydrogen (rel. Earth) is taken as a sign of greater diffusion rate of H (vs Deuterium) due to the lower gravitational forces.  
> **username_5**: Forget trillions. The Sun is a Main Sequence star headed for red giant-hood (https://en.m.wikipedia.org/wiki/Red_giant) in less than 10B years. This event will blow away atmospheres and probably moon satellites of every planet inside the asteroid belt. Bye bye lunar tidal lock. Now the site wants me to ask a question! Or I get no points. What happens when Earth were to lose its magnetic field is not as interesting a question (it being way speculative) as what the evolution of our planet's magnetic field is actually moving toward. So here is what I ask: Is the long term magnetic field average i  
> **username_6**: I always thought that the main protective effect of the magnetic field was the charged particles carried by the solar winds that would bombard and kill us, more than the stripping away of the atmosphere.  
> **username_7**: See also https://earthscience.stackexchange.com/questions/8845/what-is-the-characteristical-time-of-the-loss-of-the-earth-atmosphere-how-can-i  
> **username_8**: Related question https://earthscience.stackexchange.com/questions/14915/does-the-magnetic-field-really-protect-earth-from-anything/  
> **username_9**: Wow this is crappy science. No EMF would cause a cascade of megadisasters….and yes weather & temperatures change dramatically despite the author’s assertion. Last pole flip 42k years ago that caused a MASS EXTINCTION, that speaks louder than blogs. We’ve lost 50% of field strength in last 1,500 years & an extra 10% the last hundred…we are in the POLEFLIP NOW! https://youtu.be/tOUQz7BlX4c Lots of charts, data in this video  

---

## 2 answers

### Answer by username_12 on 2014-04-30. Score: 16 | Accepted answer

Atmospheric escape is a topic with a long research history. It is complex and is being addressed with both measurements and simulations.

For example, the question of atmospheric escape is still actively researched at Mars, and the MAVEN (Mars Atmosphere and Volatile Evolution) spacecraft mission is for example dedicated to this topic. Mars is a planet without a significant global magnetic field (although it does possess crustal magnetic anomalies); in fact its planetary dynamo was active and then stopped about 3.6 billion years ago, which considerably reduced the strength of its magnetic field.  
So understanding the evolution of its atmosphere helps to relate to what would happen if Earth would loose its magnetic field. The question of atmospheric escape at Mars is relevant concerning the fate of water (geological evidences indicate the presence of liquid water in the past, which suggests a warm and dense atmosphere able to support it at that time).

Besides thermal atmospheric escape, there is also non thermal escape, including removal by asteroid impact (in the past) and by interaction between the atmosphere and the solar wind leading to pickup of atmospheric ions (in the past and continuing today).

Some examples of references to the scientific literature about atmospheric escape at terrestrial planets (abstracts):  
[Outgassing History and Escape of the Martian Atmosphere and Water Inventory](http://adsabs.harvard.edu/abs/2013SSRv..174..113L)  
or  
[Nonthermal escape of the atmospheres of Venus, Earth, and Mars](http://adsabs.harvard.edu/abs/1996RvGeo..34..483S)


---

### Answer by username_10 on 2014-04-22. Score: 15

Since atmospheric retention is largely dependent on escape velocity and temperature, removal of the Earth's magnetic field should not have a greatly noticeable effect, as current research shows that Earth's magnetic field changes the location of atmosphere loss due to the solar wind rather than eliminating it. Earth's temperature is not likely to change much without a magnetic field (with the current solar luminosity), so that too can be discounted.

It is far more likely that Earth's atmosphere will diminish as a result of increasing temperature as the sun expands due to an increase in helium fusion as it runs out of hydrogen, a phenomenon that would not be dependent on having or not having a magnetic field. That would be in roughly 5 to 7 billion years according to the [Atmospheric Escape](http://en.wikipedia.org/wiki/Future_of_the_Earth) and the [Formation and evolution of the Solar System](http://en.wikipedia.org/wiki/Formation_and_evolution_of_the_Solar_System#Timeline_of_Solar_System_evolution)  Wikipedia articles.

If we discount solar expansion and make the convenient but incorrect assumption that solar wind and temperature will remain constant over time, then it is possible that Earth's atmosphere could be stripped in a timeframe on the order of many trillions of years. See the [Atmospheric Escape](http://en.wikipedia.org/wiki/Atmospheric_escape) Wikipedia article, and this [How Vital Is a Planet's Magnetic Field](http://www.space.com/11187-earth-magnetic-field-solar-wind.html) Space.com article.

> **Comments:**
> **username_10**: Given that Venus does not have much of a magnetic field, has lower gravity and a higher temperature, and is closer to the sun where solar wind effects would be greater, and still has a very thick atmosphere presumably billions of years after its formation, I would say that solar wind effects would not be terribly significant at these distances on an object of sufficient size.  
> **username_0**: That could be, I was specifically commenting on the suggestion that influx would equal outflux.  The mass flux of the solar wind is insignificant.  There is a net outflow of both hydrogen and oxygen from the Earth's atmosphere, fortunately there's a vast reservoir in the crust and oceans, so it's not a practical problem (for example, see [Slapak (2013)](http://pure.ltu.se/portal/files/42434406/Rikard_Slapak.pdf)).  The question is, how much more would it be without a magnetosphere?  
> **username_10**: I didn't mean to suggest that solar wind effects were zero-sum, just that with the other considerations such as solar expansion, it was not particularly significant.  Note the `much` in `not likely to change much`  
> **username_0**: Ok.  Still, your answer remains unsourced, and it seems speculative, and therefore it is not very useful.  Some references to peer-reviewed literature would be highly valuable.  
> **username_4**: Because this is a budgets and rates question, I have to downvote this until numbers and sources are added.  
> **username_10**: @Spießbürger, quite right.  Please note my edited answer including references.  It appears that my educated guesses weren't too far off, though.  
> **username_4**: @username_10 But the question is about "how long will it take", not "when will it happen".  
> **username_11**: @username_10 The key quantities are the total size of the atmosphere (Venus's is 90 times Earth's), escape velocity (Venus about equals Earth), the molecular weights in the atmosphere (Venus with CO2, ~44, and SO2, ~64; Earth with N2, ~28, O2, ~32, and Ar, ~40), the temp at the **exobase** (top) of the atmosphere which can be very different from the surface temp, the portion of atomization and ionization at the exobase, and the strength of magnetic **flux** (not field) at the exobase.  

---

