<p>No, but the magnetic dipole of Earth has a field strength that increases with closer distance. On the direct line between Earth and Sun the magnetic field strength is always <span class="math-container">$B(r) = M/r^3$</span> where <span class="math-container">$M$</span> is the magnetic moment of the terrestrial dipole and <span class="math-container">$r$</span> is the distance to the dipole, aka Earth.<br>
When the solar wind conditions change, the boundary between the wind and the terrestrial magnetosphere changes in location, until it finds a new pressure equilibrium.</p>

<p>The approximate location of the boundary shock can be found by equating the ram pressure of the solar win <span class="math-container">$p_{\rm ram}= \rho u^2$</span> with the magnetic dipole pressure <span class="math-container">$p_{\rm dip}=M^2/(2\mu_0 r^6)$</span>, where <span class="math-container">$\mu_0$</span> is the vacuum magnetic permittivity. If you solve this for <span class="math-container">$r$</span>, you will find a closer location <span class="math-container">$r$</span> for the shock for stronger conditions, and then checking at which magnetic field strength this occurs via <span class="math-container">$B(r) = M/r^3$</span>, you'll find that the magnetic field at the shock has of course increased, but only because the shock has moved closer, not because  <span class="math-container">$M$</span> has changed.</p>

CC BY-SA 4.0
2019-12-17T15:43:13.713Z
2019-12-17T15:43:13.713Z
AtmosphericPrisonEscape
<p>This curiosity arises as follows: when ejecta from a strong solar flare hits Earth, will the Earth somehow <em>counter</em> its impact with a stronger magnetic field. </p>

<p>Or, earth's magnetic field as limited power strength to resist? </p>

CC BY-SA 4.0
2019-12-17T10:24:44.803Z
I adjusted some of your wording to better fit the Stack Exchange style, but I think I've left the core of your question unchanged. It's a good question and in some cases impact of a high speed plasma can locally compress magnetic field lines, which could make the magnitude (strength) of the field stronger in that area, though the total flux from the Earth would remain essentially unchanged. Hopefully someone who is more knowledgable will write up a complete answer.
uhoh
CC BY-SA 4.0
2022-10-14T13:24:50.940Z
Solar flares do not, in general, affect Earth's magnetic field as they are intensifications of x-rays in a localized region on the Sun, e.g., see more at https://astronomy.stackexchange.com/a/16786/13663
honeste_vivere
<the-sun><magnetic-field><solar-flare><planetary-science><coronal-mass-ejection>
Does Earth's magnetic field become stronger when a solar flare hits?
Ubi.B
# Does Earth's magnetic field become stronger when a solar flare hits?

(Asked by: username_0 on 2019-12-17)

This curiosity arises as follows: when ejecta from a strong solar flare hits Earth, will the Earth somehow *counter* its impact with a stronger magnetic field.

Or, earth's magnetic field as limited power strength to resist?

**Tags:** the-sun, magnetic-field, solar-flare, planetary-science, coronal-mass-ejection

> **Comments:**
> **username_1**: I adjusted some of your wording to better fit the Stack Exchange style, but I think I've left the core of your question unchanged. It's a good question and in some cases impact of a high speed plasma can locally compress magnetic field lines, which could make the magnitude (strength) of the field stronger in that area, though the total flux from the Earth would remain essentially unchanged. Hopefully someone who is more knowledgable will write up a complete answer.  
> **username_2**: Solar flares do not, in general, affect Earth's magnetic field as they are intensifications of x-rays in a localized region on the Sun, e.g., see more at https://astronomy.stackexchange.com/a/16786/13663  

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## 1 answers

### Answer by username_3 on 2019-12-17. Score: 3 | Accepted answer

No, but the magnetic dipole of Earth has a field strength that increases with closer distance. On the direct line between Earth and Sun the magnetic field strength is always $B(r) = M/r^3$ where $M$ is the magnetic moment of the terrestrial dipole and $r$ is the distance to the dipole, aka Earth.  
When the solar wind conditions change, the boundary between the wind and the terrestrial magnetosphere changes in location, until it finds a new pressure equilibrium.

The approximate location of the boundary shock can be found by equating the ram pressure of the solar win $p\_{\rm ram}= \rho u^2$ with the magnetic dipole pressure $p\_{\rm dip}=M^2/(2\mu\_0 r^6)$, where $\mu\_0$ is the vacuum magnetic permittivity. If you solve this for $r$, you will find a closer location $r$ for the shock for stronger conditions, and then checking at which magnetic field strength this occurs via $B(r) = M/r^3$, you'll find that the magnetic field at the shock has of course increased, but only because the shock has moved closer, not because $M$ has changed.


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