Fourier Analysis of Magnetic Fields in the Ionosphere of Mars

Abstract

The two main sources of magnetic field for the Martian ionosphere are the solar wind magnetic fields (i.e., the interplanetary magnetic field), and, particularly in the southern hemisphere, remnant crustal magnetization. The magnetic fields measured in the ionosphere by the magnetometers onboard the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft and the Mars Global Surveyor (MGS) display a wide range of spatial scales. In this paper we use a Fourier analysis of the magnetic field to quantify the field strength as a function of scale-size. Fourier analysis represents a function of time (or some other variable) as the sum over a wide range of sinusoidal functions of different frequencies. We find that results of the Fourier analysis for the ionospheric magnetic field have much in common with the Fourier analysis of the interplanetary magnetic field. The paper exploits this similarity to probe the sources of the ionosphere’s magnetic structure.