Continuous Surge Research Articles

Consideration of air entrapment in surface irrigation; A computer simulation study

A numerical model, based on Richard's equation was used to simulate infiltration for continuous flow, surge flow, and surge flow with air entrapment on a Rubicon sandy loam soil. Air entrapment was described by reducing the rewet water content in the water retention function by 10% during the first redistribution. Surge simulations consisted of four cycles with 10 min on and off times followed by one last surge with 20 min on-time. For comparison purposes the opportunity time for the continuous flow simulation was the same as for the surge simulations. Results showed a 21% decrease in cumulative infiltration for the air entrapment simulations compared with that for continuous flow. A larger simulation time corresponding to an actual irrigation event would have increased the magnitude of the differences in cumulative infiltration between the continuous flow and air entrapment simulations. In summary, it was demonstrated that air entrapment could significantly contribute to intake rate reduction under surge irrigation in sandy soils. More experimental research is needed to accurately model air entrapment and conduct comprehensive simulation studies.

Chromospheric explosions and satellite sunspots

Observations of the longitudinal component of the photospheric magnetic fields near sunspots imply that surges and Ellerman bombs occur at neutral points in the magnetic fields (i.e. |B|=0) in the chromosphere. The neutral points appear above satellite sunspots, which are defined as polarity reversals (in B||) near the edges of large-spot penumbrae. A series of magnetograph observations shows a point of satellite polarity vanishing during a period of almost continuous surge activity. The lost magnetic energy is comparable to the energy release evidenced by the surge.