<p>How would you get a magnetar close to Mars, within the solar system?</p>

<p>OK, let's leave that to one side, but the Earth's magnetic field is of  order $10^{-4}$ Tesla at strongest. As the dipole field of a magnetar diminishes as $r^{-3}$ and could be as high as $10^{11}$ Teslas at the surface of the magnetar, at a radius of 10 km, then the magnetar woud need to be at a distance of $10^{6}$ km to surround Mars with a field of $10^{-4}$ Tesla.</p>

<p>The problem is that the radiation coming from the magnetar in the form of charged particles accelerated from the magnetic poles would <em>completely dwarf</em> the charged particle radiation from the Sun at Mars.</p>

<p>So no, a nearby Magnetar would not save Mars' atmosphere - quite the reverse.</p>

<p>EDIT: A BOTE calculations: If we look at the Crab pulsar - not quite a magnetar, but close - it is calculated that 10% of the rotational KE being lost ends up in synchrotron raiation from charged particles. That's about $10^{30}$ Watts. So there is at least $\sim 10^4$ solar luminosities, just in the kinetic energy of relativistic particles.</p>

<p>Magnetars are also very strong and variable sources of hard X-ray and Gamma ray radiation. Typical magnetar bursts/flares can release $10^{7}-10^{9}$ solar luminosities of hard X-rays and Gamma rays over periods of 1-40 s. That should fry any atmosphere (or anything else) that was only $10^{6}$ km away!</p>

CC BY-SA 3.0
2015-02-21T20:56:44.637Z
2015-02-21T21:27:08.713Z
2015-02-21T21:27:08.713Z
ProfRob
<p>Just wondering: if a magnetar was close enough to Mars would it have saved its atmosphere by protecting it from solar radiation? I was wondering this because Earth protects us via a magnetic field; the magnetar would be providing Mars one. This is if it did not destroy the planet first as suggested <a href="https://astronomy.stackexchange.com/questions/9944/can-magnetars-destroy-planets">here</a>.</p>

<p><strong>Edit</strong>
I meant if the magnetar was safe to live by. </p>

<mars><planetary-atmosphere><magnetic-field><neutron-star>
Could a magnetars magnetic field have saved Mars atmosphere?
iProgram
# Could a magnetars magnetic field have saved Mars atmosphere?

(Asked by: username_0 on 2015-02-21)

Just wondering: if a magnetar was close enough to Mars would it have saved its atmosphere by protecting it from solar radiation? I was wondering this because Earth protects us via a magnetic field; the magnetar would be providing Mars one. This is if it did not destroy the planet first as suggested [here](https://astronomy.stackexchange.com/questions/9944/can-magnetars-destroy-planets).

**Edit**
I meant if the magnetar was safe to live by.

**Tags:** mars, planetary-atmosphere, magnetic-field, neutron-star

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## 1 answers

### Answer by username_1 on 2015-02-21. Score: 6

How would you get a magnetar close to Mars, within the solar system?

OK, let's leave that to one side, but the Earth's magnetic field is of order $10^{-4}$ Tesla at strongest. As the dipole field of a magnetar diminishes as $r^{-3}$ and could be as high as $10^{11}$ Teslas at the surface of the magnetar, at a radius of 10 km, then the magnetar woud need to be at a distance of $10^{6}$ km to surround Mars with a field of $10^{-4}$ Tesla.

The problem is that the radiation coming from the magnetar in the form of charged particles accelerated from the magnetic poles would *completely dwarf* the charged particle radiation from the Sun at Mars.

So no, a nearby Magnetar would not save Mars' atmosphere - quite the reverse.

EDIT: A BOTE calculations: If we look at the Crab pulsar - not quite a magnetar, but close - it is calculated that 10% of the rotational KE being lost ends up in synchrotron raiation from charged particles. That's about $10^{30}$ Watts. So there is at least $\sim 10^4$ solar luminosities, just in the kinetic energy of relativistic particles.

Magnetars are also very strong and variable sources of hard X-ray and Gamma ray radiation. Typical magnetar bursts/flares can release $10^{7}-10^{9}$ solar luminosities of hard X-rays and Gamma rays over periods of 1-40 s. That should fry any atmosphere (or anything else) that was only $10^{6}$ km away!


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