I am trying to find relevant literature about the possible magnetic attraction forces between snowflakes. Is it negligible or significant enough to trigger collision?
Hadi Jabbar Alagealy , could you please elaborate a little bit? Thanks in advance
Probably you are looking for a device called a "snowflake divertor”, googling it will be enough I hope.
Ciao Jacopo Grazioli , I guess you attracted some plasma-physics answers. Assuming you were actually interested in the magnetic attraction between ice particles in natural clouds, I would say that this process is not really relevant and that is why it is not possible to find studies on that. The thing is that ice is diamagnetic and would interact with externally applied magnetic fields, but by itself, it does not have a magnetic field, this blog post might help clarify that http://www.madsci.org/posts/archives/2008-08/1219953614.Ph.r.html Thinking about electromagnetic interactions is indeed fascinating and worth study. But being practical I would say that a simple differential sedimentation process already explains most of the aggregation Article Universality in snowflake formation
To improve upon that simplification I would first consider the enhanced snow collision rate due to the catching of crystals in the aerodynamic wake of another (there are tank experiments that show that and probably also numerical simulations). Coming back to your idea, I would say that electric fields (not magnetic) might play a role and that is worth some attention. It appears that ice processes are connected with cloud electrification and thus it comes naturally that ice particles are charge carriers. In this scenario, aggregation might be enhanced by this charge separation and it would act as a cloud "neutralizing" process that avoids electrification.Article Charge, Morphology, and p H of Natural Snow
Article Charge on ice crystals in laboratory clouds
Article Electrical Charges on Snow Particles
It is a fascinating idea but complex to study. Charged particles would either attract or repulse depending on the charge pair. It will probably depend on how that charge surplus has formed and whether or not the opposite charge is present within the cloud.
Davide Ori , what a pleasure to get your answer (and so also hear from you!). Super inputs, thanks a lot. It was the kind of overview I was looking for.
Hi Jacopo: As usual, I agree completely with what Davide Ori said ;-) Just to add some more recent literature on this topic I came across recently:
There seems to be in-situ evidence that strongly charged thunderstorms enhance aggregation in very cold cloud regions where aggregation is usually not very efficient: Article Aircraft observations of the influence of electric fields on...
What I find quite interesting is that the "main charging zone" in convective clouds is roughly between -10 and -20°C where we also know that many ice microphysics (esp. aggregation, sec. ice, riming, etc.) is active. It is quite amazing/frustrating how long people think about the mechanisms how those clouds get charged and how little the overall "convergence" in this topic is. Here is a recent review related to charging mechanisms: Article Charge Separation Mechanisms in Clouds
Cheers,
Stefan
Dear Stefan Kneifel : thanks a lot! Very nice input and excellent literature suggestions. I agree that there is plenty to converge on on the subject and a lot still to do in experiments and modeling. A good breakthrough, either technological or from the model side would be very welcome
Some old work now but showing near-surface effects: Article The Electric Field During Blowing Snow Events
Thanks Richard Davy , interesting to see also the effects in case of horizontal snow transport
water molecule has a strong electric dipole moment (about 1.84-1.85 debye, see my book Physics and Dynamics of Clouds and Precipitation, 2013 Cambridge University Press). Collision between snowflakes are far more likely due to electric effect than any magnetic effect. Water molecule does not respond strongly to a normal magnetic field in the earth environment.
Dear Pao K. Wang , thank you very much for your complementary information!