Modulation of Jovian and galactic electrons in the heliosphere: 1. Latitudinal transport of a few MeV electrons

Abstract

Abstract. The heliospheric modulation of galactic and Jovian electrons is studied using a fully threedimensional, steady state model based on Parker's transport equation including the Jovian source. The modulation of low-energy electrons is a handy tool to establish and to construct a suitable diffusion tensor to assure compatibility between model computations and observations from the Ulysses spacecraft. This is because electron modulation responds directly to the energy dependence of the diffusion coefficients below -500 MeV in contrast to protons which experience large adiabatic energy losses below this energy. The model is used to study the latitudinal transport of both Jovian and 4-20 MeV galactic electrons by illustrating how the electron intensities are affected at different latitudes when enhancing perpendicular diffusion in the polar direction. In particular, the electron intensity-time profile along the Ulysses trajectory is calculated for various assumptions for perpendicular diffusion in the polar direction and compared to the 3-10 MeV electron flux observed by Ulysses from launch up to the end of the first out of the ecliptic orbit. Comparison of the model computations and the observations give an indication as to the magnitude of this diffusion coefficient. The relative contributions of the Jovian and galactic electrons to the total electron intensity is shown along the Ulysses trajectory.

Modulation of Galactic Protons in the Heliosphere During the Unusual Solar Minimum of 2006 to 2009

“…is enhanced towards the poles by a factor d with respect to the value of K || in the equatorial regions of the heliosphere (as also applied and motivated by Potgieter, 2000;Ferreira et al, 2001Ferreira et al, , 2003Moeketsi et al, 2005;Ngobeni and Potgieter, 2011 …”

“…For elaborated discussions on this issue, see also Strauss, Potgieter, and Ferreira (2011) and Ngobeni and Potgieter (2010). The numerical procedure used to solve Equation (1) was described by Ferreira and Potgieter (2002) and Ferreira et al (2001Ferreira et al ( , 2003 and Nkosi, Potgieter and Ferreira (2008). Graphical illustrations of the diffusion coefficients and the drift coefficient as a function of rigidity will be shown below, together with the computed spectra.…”

3–20 MeV Electrons in the Inner Three‐dimensional Heliosphere at Solar Maximum:UlyssesCOSPIN/KET Observations

“…Ulysses observations of a few MeV electrons in the inner threedimensional heliosphere have been successfully modeled by Ferreira et al (2001a) during the time period from launch of Ulysses in 1990-1998, during the declining and minimum phase of solar cycle 22. It is important to note that for MeV electrons drift effects are of minor importance, so that the model is dominated by diffusion.…”

“…It is important to note that for MeV electrons drift effects are of minor importance, so that the model is dominated by diffusion. In order to obtain reasonable compatibility of the simulated intensities with the observation, Ferreira et al (2001a) had to use a set of diffusion coefficients in which the ratio, in the equatorial plane, of the perpendicular diffusion coefficient in the polar direction ( ? ; ) to the parallel diffusion coefficient ( k ) was between 0.005 and 0.02.…”

Modulation of galactic cosmic rays during the unusual solar minimum between cycles 23 and 24

“…In this work a relatively simple spatial and momentum dependence of the diffusion coefficients is assumed following Zhang [1999] and Ferreira et al [2001]. First, parallel diffusion is set as [Zhang, 1999;Ferreira et al, 2001]…”