Precise determination of lightning plasma parameters based on a collisional-radiative model

Abstract A fine spectrum of natural lightning has been simulated by collisional-radiative model (CRM), and the line-intensities of N II dependent on electron temperature ( T e ) and electron density ( n e ) were obtained. It was found that the intensity proportion of 2p3d 3 F <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mi/> <mml:mn>4</mml:mn> <mml:mo>∘</mml:mo> </mml:msubsup> </mml:mrow> </mml:math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mo stretchy="false">→</mml:mo> </mml:mrow> </mml:math> 2p3p 3 D 3 and 2p3p 3 D 3 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mo stretchy="false">→</mml:mo> </mml:mrow> </mml:math> 2p3s 3 P <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mi/> <mml:mn>2</mml:mn> <mml:mo>∘</mml:mo> </mml:msubsup> </mml:mrow> </mml:math> transitions in the multiple spectral lines to which they belong tend to stabilize in the T e - n e variation space, which is an inherent physical property that can be applied in determining the experimental intensity of characteristic lines from the total intensity of overlapped lines. By accurately matching the theoretical intensity-ratio with the experimental one, two intersections of contours of line-intensity ratios in the two-dimensional plane of T e - n e are derived, and then the T e and n e in the lightning channel were diagnosed simultaneously. The precise spectral analysis method and plasma diagnostic technique are the basis for researching other physical characteristics of lightning discharges, this work also has application value in artificially triggered lightning, laser-guided lightning, arc discharge, etc.