Thunderstorms Make Trees Glow

Scientists have long hypothesized that the high electrical charge of thunderstorms could produce an opposite charge in the ground that would discharge from the forest canopy. But this phenomenon, known as a corona, had never been observed on actual trees. A new study, however, has observed this ghostly ultraviolet (UV) glow from the tips of sweetgum leaves and loblolly pine needles during thunderstorms.

Catching these coronae in action required a new kind of UV detector that was ultra-sensitive to the particular band of UV-light emitted by coronas, hot fires, or mercury lamps. Since the latter two weren’t present during the team’s field observations, they were able to conclude that the light they detected came from coronae.

The group observed that corona discharges were transient, jumping from leaf to leaf and branch to branch across the forest canopy. For any creature capable of detecting that glow by eye, it must be incredible to watch the treetops lit by their own ever-shifting auroras during every thunderstorm. (Image credit: W. Brune; research credit: P. McFarland et al.; via SciAm)

'Field Evaporation Simulation in #ElectrosprayThrusters Using Electrohydrodynamics–Particle-in-Cell Method' - an article in the #AIAA Space Collection on #ScienceOpen:

🗞️🔗 https://www.scienceopen.com/document?vid=42d598ba-d5b1-4fa6-b940-6cfb41a67474

#ElectricPropulsion #ParticleInCell #Electrohydrodynamics #SpaceTech

'Field Evaporation Simulation in Electrospray Thrusters Using Electrohydrodynamics–Particle-in-Cell Method' - an article in the #AIAA Space Collection on #ScienceOpen:

🔗 https://www.scienceopen.com/document?vid=42d598ba-d5b1-4fa6-b940-6cfb41a67474

#AerospaceEngineering #Electrohydrodynamics #ElectrosprayThruster #SpacePropulsion

Charged Drops Don’t Splash

When a droplet falls on a surface, it spreads itself horizontally into a thin lamella. Sometimes — depending on factors like viscosity, impact speed, and air pressure — that drop splashes, breaking up along its edge into myriad smaller droplets. But a new study finds that a small electrical charge is enough to suppress a drop’s splash, as seen below.

The drop’s electrical charge builds up along the drop’s surface, providing an attraction that acts somewhat like surface tension. As a result, charged drops don’t lift off the surface as much and they spread less overall; both factors inhibit splashing.* The effect could increase our control of droplets in ink jet printing, allowing for higher resolution printing. (Image and research credit: F. Yu et al.; via APS News)

*Note that this only works for non-conductive surfaces. If the surface is electrically conductive, the charge simply dissipates, allowing the splash to occur as normal.

#dropletImpact #droplets #electricalField #electrohydrodynamics #fluidDynamics #lamella #physics #science #splashes #splashing

Salt Affects Particle Spreading

Microplastics are proliferating in our oceans (and everywhere else). This video takes a look at how salt and salinity gradients could affect the way plastics move. The researchers begin with a liquid bath sandwiched between a bed of magnets and electrodes. Using Lorentz forcing, they create an essentially 2D flow field that is ordered or chaotic, depending on the magnets’ configuration. Although it’s driven very differently, the flow field resembles the way the upper layer of the ocean moves and mixes.

The researchers then introduce colloids (particles that act as an analog for microplastics) and a bit of salt. Depending on the salinity gradient in the bath, the colloids can be attracted to one another or repelled. As the team shows, the resulting spread of colloids depends strongly on these salinity conditions, suggesting that microplastics, too, could see stronger dispersion or trapping depending on salinity changes. (Video and image credit: M. Alipour et al.)

#2024gofm #electrohydrodynamics #flowVisualization #fluidDynamics #geophysics #magneticField #physics #plasticPollution #science #turbulence

After starting to read Destexhe & Rudolph-Lilith's book, I looked at the googl scholar page for Alain Destexhe and found this 3 page paper from last year, showing that the Navier-Stokes equations for charged fluids can be used to derive the cable equations for neurons

https://arxiv.org/abs/2201.04927

#Neuroscience #Biophysics #Electrohydrodynamics