Ground‐based estimates of outer radiation belt energetic electron precipitation fluxes into the atmosphere

Abstract

[1] AARDDVARK data from a radio wave receiver in Sodankylä, Finland have been used to monitor transmissions across the auroral oval and just into the polar cap from the very low frequency communications transmitter, call sign NAA (24.0 kHz, 44°N, 67°W, L = 2.9), in Maine, USA, since 2004. The transmissions are influenced by outer radiation belt (L = 3-7) energetic electron precipitation. In this study, we have been able to show that the observed transmission amplitude variations can be used to determine routinely the flux of energetic electrons entering the upper atmosphere along the total path and between 30 and 90 km. Our analysis of the NAA observations shows that electron precipitation fluxes can vary by 3 orders of magnitude during geomagnetic storms. Typically when averaging over L = 3-7 we find that the >100 keV POES "trapped" fluxes peak at about 10 6 el. cm −2 s −1 sr −1 during geomagnetic storms, with the DEMETER >100 keV drift loss cone showing peak fluxes of 10 5 el. cm −2 s −1 sr −1 , and both the POES >100 keV "loss" fluxes and the NAA ground-based >100 keV precipitation fluxes showing peaks of ∼10 4 el. cm −2 s −1 sr −1 . During a geomagnetic storm in July 2005, there were systematic MLT variations in the fluxes observed: electron precipitation flux in the midnight sector (22-06 MLT) exceeded the fluxes from the morning side (0330-1130 MLT) and also from the afternoon sector (1130( -1930. The analysis of NAA amplitude variability has the potential of providing a detailed, near real-time, picture of energetic electron precipitation fluxes from the outer radiation belts.

What is the solar influence on climate? Overview of activities during CAWSES-II

“…Thus, the use of any POES observations as a measure of electron precipitation into the atmosphere needs to be carefully considered. In order to constrain the POES observations, Clilverd et al (2010) have demonstrated the potential of using ground-based observations of changes in ionospheric D-layer ionisation (VLF, very low frequency radio propagation) to establish near-real-time electron precipitation fluxes. For the time being, inclusion of electron precipitation and thus full EPP forcing in model simulations is yet to reach the same routine approach as solar protons (SPEs).…”

A Case Study of Energy Deposition and Absorption by Magnetic Cloud Electrons and Protons over the High Latitude Stations: Effects on the Mesosphere and Lower Thermosphere

“…The locations of the Finnish chain of riometer stations and their L-values are tabulated in Table 1. A riometer responds to the integrated absorption of cosmic ray noise through the ionosphere (Clilverd et al 2010) where the particle motion is collision dominated. The riometers are widebeam, typically 30 MHz and sensitive to any incident particle population capable of reaching the ionosphere in the range of 70 -100 km (that is, D-region).…”

Space weather effects on the low latitude D-region ionosphere during solar minimum

“…They obtained negative phase and amplitude variations of the VLF signal both during day and nighttimes during the main storm phase days, but the nighttime variations were more pronounced. There have not been other studies on magnetic storm associated subionospheric changes purely at low latitude paths; however, there have been several studies on VLF perturbations due to storm-induced energetic electron precipitation at mid and high latitudes (e.g., Peter et al 2006;Clilverd et al 2010).…”