TY - JOUR

T1 - Triangulating the height of cosmic noise absorption: A method for estimating the characteristic energy of precipitating electrons

AU - Wild, P.

AU - Honary, F.

AU - Kavanagh, A.J.

AU - Senior, A.

N1 - Copyright (2010) American Geophysical Union. Further reproduction or electronic distribution is not permitted.

PY - 2010/12/21

Y1 - 2010/12/21

N2 - Energetic electrons (tens to hundreds of keV) deposit significant energy into the D layer of the ionosphere. Riometers provide a means of monitoring this electron precipitation by measuring the associated cosmic noise absorption (CNA), but individually they are incapable of resolving the associated energy. However, the combination of two imaging riometers with overlapping beams allows an estimate of the height of peak CNA and so the associated energy to be made. We examine two methods for estimating the height of CNA using data from two imaging riometers in northern Fennoscandia; a 3-D reconstruction of CNA using Occam's inversion and a technique based upon the triangulation of discrete absorption structures are developed. We compare these two methods with the results from a previously published technique. It is found that for the case studies and test phantoms the height triangulation and 3-D reconstruction offer improvement over previous methods. These techniques are tested by comparison with data from the EISCAT incoherent scatter radar. Observations show good correlation between the estimates of peak height of CNA from EISCAT and from the triangulation and 3-D reconstruction methods for this case. Three case studies are examined in detail, a slowly varying absorption, afternoon spike, and evening absorption spike event. Estimates of the characteristic energy are made. The substorm event had a characteristic energy of ∼5 keV, whereas the characteristic energy for the morning event was 17–20 keV. Analyses indicate the afternoon spike event having characteristic energy greater than 100 keV.

AB - Energetic electrons (tens to hundreds of keV) deposit significant energy into the D layer of the ionosphere. Riometers provide a means of monitoring this electron precipitation by measuring the associated cosmic noise absorption (CNA), but individually they are incapable of resolving the associated energy. However, the combination of two imaging riometers with overlapping beams allows an estimate of the height of peak CNA and so the associated energy to be made. We examine two methods for estimating the height of CNA using data from two imaging riometers in northern Fennoscandia; a 3-D reconstruction of CNA using Occam's inversion and a technique based upon the triangulation of discrete absorption structures are developed. We compare these two methods with the results from a previously published technique. It is found that for the case studies and test phantoms the height triangulation and 3-D reconstruction offer improvement over previous methods. These techniques are tested by comparison with data from the EISCAT incoherent scatter radar. Observations show good correlation between the estimates of peak height of CNA from EISCAT and from the triangulation and 3-D reconstruction methods for this case. Three case studies are examined in detail, a slowly varying absorption, afternoon spike, and evening absorption spike event. Estimates of the characteristic energy are made. The substorm event had a characteristic energy of ∼5 keV, whereas the characteristic energy for the morning event was 17–20 keV. Analyses indicate the afternoon spike event having characteristic energy greater than 100 keV.

KW - riometer DCS-publications-id

KW - art-1017

KW - DCS-publications-credits

KW - aries

KW - iono-fa

KW - iris

KW - DCS-publications-personnel-id

KW - 136

KW - 5

KW - 9

KW - 51

U2 - 10.1029/2010JA015766

DO - 10.1029/2010JA015766

M3 - Journal article

VL - 115

SP - 1

EP - 11

JO - Journal of Geophysical Research

JF - Journal of Geophysical Research

SN - 0148-0227

IS - A12326

ER -