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Lightning forcing of tornado

Kumar Prabhat

Acta Geophysica

2023

Vol. 71, no. 4

1967--1981

It is mathematically noted that the waveform perturbations that caused the electric field due to the lightning burst during intracloud (IC) or cloud to ground (CG) lightning cause strong fluctuations in the induced magnetic field which is summation of two components: (i) highly fluctuating [dominant] and (ii) relatively steadier [weaker]. As an example, a periodic cosine function of magnetic field with microsecond or submicrosecond period has been mathematically formulated. Magnetohydrodynamic analysis within the corona envelope up to the skin depth in the lowest layer, above ground level, indicated that mean Lorentz force is comprised of two parts (i) magnetic pressure rotational component and (ii) irrotational component. Later is product of horizontal magnetic field gradient (HMG) and exponential term (ET). Intracloud HMG helps funnel lowering below the cloud base, and Bernoulli’s principle causes the cloud formation within the funnel. Minor increase in magnetic field (B0) makes large change in HMG as magnetic field term appears as square (B02). This explains why positive lightning {refer Sect. 5.1 col. 4 and 5 of Tables 1 and 2 showing typical values of Bi and Bh for positive and negative CG lightning, respectively} is more favourable to higher EF tornadogenesis and long-track tornadoes. Polarity reversal is often indicative of long-track tornadoes because after its formation even relatively weaker negative CG lightning can help sustain it to longer track. Analytical expressions for buoyancy - change, due to lightning jump, have been also examined.