<p>The convective overturn time is the typical timescale for a convective cell to rise in a gas. Imagine a "lava lamp" - it's the time for one of the blobs to rise from its lowest to highest point.</p>

<p>I am most familiar with its use in stars, where convective energy transport is modelled using a mixing length. This posits that the typical height travelled by an adiabatic convection cell is some multiple $\alpha$ of the pressure scale height $H_p$ (the typical length on which the internal pressure changes significantly). </p>

<p>The convective overturn (or turnover) time is then $\alpha H_p/v$, where $v$ is the velocity at which convective cells rise.</p>

CC BY-SA 3.0
2017-12-20T09:06:22.967Z
Thanks very much, I am a freshman in this field, could you recommend a book or something else about this?
Lack Coma
CC BY-SA 3.0
2017-12-20T10:33:13.113Z
@LackComa It is an output from a theoretical model - a way of characterising the convection. I am only familiar with it from research papers that can be found by searching on "convective turnover time".
ProfRob
CC BY-SA 3.0
2017-12-20T07:28:58.227Z
2017-12-20T07:28:58.227Z
ProfRob
<p>When I read some papers about MHD dynamo theory, there is always a $\tau$ that means convection overturning time. What does <em>convection overturn</em> mean?</p>

<the-sun><stellar-dynamics>
What is convection overturn?
Lack Coma
# What is convection overturn?

(Asked by: username_0 on 2017-12-20)

When I read some papers about MHD dynamo theory, there is always a $\tau$ that means convection overturning time. What does *convection overturn* mean?

**Tags:** the-sun, stellar-dynamics

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## 1 answers

### Answer by username_1 on 2017-12-20. Score: 6 | Accepted answer

The convective overturn time is the typical timescale for a convective cell to rise in a gas. Imagine a "lava lamp" - it's the time for one of the blobs to rise from its lowest to highest point.

I am most familiar with its use in stars, where convective energy transport is modelled using a mixing length. This posits that the typical height travelled by an adiabatic convection cell is some multiple $\alpha$ of the pressure scale height $H\_p$ (the typical length on which the internal pressure changes significantly).

The convective overturn (or turnover) time is then $\alpha H\_p/v$, where $v$ is the velocity at which convective cells rise.

> **Comments:**
> **username_0**: Thanks very much, I am a freshman in this field, could you recommend a book or something else about this?  
> **username_1**: @LackComa It is an output from a theoretical model - a way of characterising the convection. I am only familiar with it from research papers that can be found by searching on "convective turnover time".  

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