A local interstellar spectrum for galactic electrons

A heliopause spectrum at 122 AU from the Sun is presented for galactic electrons over an energy range from 1 MeV to 50 GeV that can be considered the lowest possible local interstellar spectrum (LIS). The focus is on the spectral shape of the LIS below 1.0 GeV. The study is done by using a comprehensive numerical model for solar modulation in comparison with Voyager 1 observations at 110 AU from the Sun and PAMELA data at Earth. Below 1.0 GeV, this LIS exhibits a power law,E to the power -(1.55+-0.05), where E is the kinetic energy. However, reproducing the PAMELA electron spectrum averaged for 2009, requires a LIS with a different power law of the form E to the power -(3.15+-0.05) above about 5 GeV. Combining the two power laws with a smooth transition from low to high energies yields a LIS over the full energy range that is relevant and applicable to the modulation of cosmic ray electrons in the heliosphere. The break occurs between 800 MeV and 2 GeV as a characteristic feature of this LIS.Comment: 15 pages,3 figure

Ionospheric Response at Conjugate Locations During the 7–8 September 2017 Geomagnetic Storm Over the Europe-African Longitude Sector

This paper focuses on unique aspects of the ionospheric response at conjugate locations over Europe and South Africa during the 7–8 September 2017 geomagnetic storm including the role of the bottomside and topside ionosphere and plasmasphere in influencing electron density changes. Analysis of total electron content (TEC) on 7 September 2017 shows that for a pair of geomagnetically conjugate locations, positive storm effect was observed reaching about 65% when benchmarked on the monthly median TEC variability in the Northern Hemisphere, while the Southern Hemisphere remained within the quiet time variability threshold of ±40%. Over the investigated locations, the Southern Hemisphere midlatitudes showed positive TEC deviations that were in most cases twice the comparative response level in the Northern Hemisphere on the 8 September 2017. During the storm main phase on 8 September 2017, we have obtained an interesting result of ionosonde maximum electron density of the F2 layer and TEC derived from Global Navigation Satellite System (GNSS) observations showing different ionospheric responses over the same midlatitude location in the Northern Hemisphere. In situ electron density measurements from SWARM satellite aided by bottomside ionosonde-derived TEC up to the maximum height of the F2 layer (hmF2) revealed that the bottomside and topside ionosphere as well as plasmasphere electron content contributions to overall GNSS-derived TEC were different in both hemispheres especially for 8 September 2017 during the storm main phase. The differences in hemispheric response at conjugate locations and on a regional scale have been explained in terms of seasonal influence on the background electron density coupled with the presence of large-scale traveling ionospheric disturbances and low-latitude-associated processes. The major highlight of this study is the simultaneous confirmation of most of the previously observed features and their underlying physical mechanisms during geomagnetic storms through a multi–data set examination of hemispheric differences. © 2020. American Geophysical Union. All Rights Reserved

Development of the HARM model for aviation dosimetry

 Primary galactic cosmic-rays (GCRs) and Solar energetic particles (SEPs) enter the Earth's atmosphere in varying amounts. Due to that, the aircrew and passengers are exposed to ionizing radiation in amounts that depend on severable factors. At the top of the atmosphere and beyond, cosmic radiation is modulated by the geomagnetic field and solar activity. Once ionising radiation, albeit from either GCRs or SEPs, crosses the geomagnetic field and enters the atmosphere, it interacts with the atmospheric molecules in the same manner regardless of where it came from. The High Altitude Radiation Monitor (HARM) model has been in development at the North-West University since January 2021, for calculation of doses of ionizing radiation in the atmosphere. Here we introduce this model, discuss its input parameters and output results, and show its initial results during flights compared with other well known models.</p

The North-West University’s High Altitude Radiation Monitor programme

Since the discovery of cosmic radiation by Victor Hess in 1912, when he reported a significant increase in radiation as altitude increases, concerns about radiation effects on human bodies and equipment have grown over the years. The secondary and tertiary particles which result from the interaction of primary cosmic rays with atmospheric particles and commercial aircraft components, are the primary cause of the radiation dose deposited in human bodies and in electronic equipment (avionics) during aircraft flights. At an altitude of about 10 km (or higher) above sea level, the dose received by frequent flyers, and especially flight crew, is a serious concern. Also of concern is the possible failure of sensitive equipment on board commercial aircrafts as a result of flying through this mixed radiation field. Monitoring radiation in the atmosphere is therefore very important. Here we report on the first measurements by the High Altitude Radiation Monitor (HARM) detector during a commercial flight from Johannesburg (O.R. Tambo International Airport) to Windhoek (Hosea Kutako International Airport). As part of a public awareness activity, the HARM detector was placed on a high-altitude balloon, and these measurements are also shown here. Model calculations (estimations) of radiation levels for the commercial aircraft flight are shown and the results are used to interpret our measurements. Significance: Measurements of the Regener–Pfotzer maximum in South Africa and dosimetric measurements on board a commercial flight are presented. These radiation measurements are compared to model calculations which can be used to predict the radiation dose during commercial flights. This study also aims to raise public awareness about the atmospheric radiation environment from ground level to the Regener–Pfotzer peak at high altitude

The mini-neutron monitor:a new approach in neutron monitor design

Abstract The near-Earth cosmic ray flux has been monitored for more than 70 years by a network of ground-based neutron monitors (NMs). With the ever-increasing importance of quantifying the radiation risk and effects of cosmic rays for, e.g., air and space-travel, it is essential to continue operating the existing NM stations, while expanding this crucial network. In this paper, we discuss a smaller and cost-effective version of the traditional NM, the mini-NM. These monitors can be deployed with ease, even to extremely remote locations, where they operate in a semi-autonomous fashion. We believe that the mini-NM, therefore, offers the opportunity to increase the sensitivity and expand the coverage of the existing NM network, making this network more suitable to near-real-time monitoring for space weather applications. In this paper, we present the technical details of the mini-NM’s design and operation, and present a summary of the initial tests and science results