Correlation between cosmic noise absorption and VHF coherent echo intensity
We present examples and statistical analysis of the events with statistically significant correlation between the cosmic noise absorption (CNA) and the signal-to-noise ratio (SNR) of the VHF coherent echo intensity in the area monitored simultaneously by an imaging riometer and two oblique-sound...
| Main Authors: | , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2005-07-01
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| Series: | Annales Geophysicae |
| Online Access: | https://www.ann-geophys.net/23/1543/2005/angeo-23-1543-2005.pdf |
| _version_ | 1818134342125223936 |
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| author | R. A. Makarevitch R. A. Makarevitch F. Honary |
| author_facet | R. A. Makarevitch R. A. Makarevitch F. Honary |
| author_sort | R. A. Makarevitch |
| collection | DOAJ |
| description | We present examples and statistical analysis of the events with
statistically significant correlation between the cosmic noise
absorption (CNA) and the signal-to-noise ratio (SNR) of the VHF
coherent echo intensity in the area monitored simultaneously by an
imaging riometer and two oblique-sounding coherent VHF radars in
Northern Scandinavia. By only considering the observations from
the narrow riometer beams comparable (in terms of the intersection
with the ionosphere) with the VHF radar cells, we identify ~200
one-hour high correlation periods (HCPs) for 2 years near the
solar cycle maximum, 2000–2001. The HCP occurrence is maximized
in the afternoon (12:00–17:00 UT, MLT≅UT+3), with the secondary
peak near the midnight (21:00–02:00 UT). Relative to the VHF echo
occurrence, HCPs occur more frequently from 11:00 to 20:00 UT. The
diurnal variation of HCP occurrence is similar to that of the
1-h intervals with the lowest mean absorption <i>A</i><0.25dB.
</p><p style="line-height: 20px;">
The HCPs are observed more frequently during the winter months,
which, combined with the fact that VHF echoes observed during HCPs
exhibit features typical for field-aligned E-region
irregularities, makes their association with the polar mesospheric
echoes (for which some positive CNA/SNR correlation has been
reported in the past) very unlikely. Instead, we attribute the
high positive CNA/SNR correlation to the synchronous, to a first
approximation, variation of the particle fluxes for two different
but close sets of energies.
</p><p style="line-height: 20px;">
By considering the dependence of the CNA/SNR correlation
coefficients for both VHF radars (<i>C<sub>A1</sub></i> and <i>C<sub>A2</sub></i>) upon the
correlation between SNRs for two radars (<i>C<sub>12</sub></i>), we show that
both coefficients, <i>C<sub>A1</sub></i> and <i>C<sub>A2</sub></i>, and the agreement between
them decrease drastically with a <i>C<sub>12</sub></i> decrease, which we
interpreted through the progressively increasing role of the
spatial inhomogeneity of the processes leading to the enhanced CNA
and SNR. In this situation, a similarity between the radio signal
collection areas should become important, and we demonstrate that
the HCP occurrence and mean correlation coefficient decrease as
the riometer beams and radar cells become less comparable in terms
of mutual orientation and closeness between the points of maximum
sensitivity. <p>
<b>Keywords.</b> Ionosphere (Auroral ionosphere; Particle precipitation;
Instruments and techniques) |
| first_indexed | 2024-12-11T09:07:05Z |
| format | Article |
| id | doaj.art-be8868f8f3f249cc9a527a866ad0a493 |
| institution | Directory Open Access Journal |
| issn | 0992-7689 1432-0576 |
| language | English |
| last_indexed | 2024-12-11T09:07:05Z |
| publishDate | 2005-07-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Annales Geophysicae |
| spelling | doaj.art-be8868f8f3f249cc9a527a866ad0a4932022-12-22T01:13:36ZengCopernicus PublicationsAnnales Geophysicae0992-76891432-05762005-07-01231543155310.5194/angeo-23-1543-2005Correlation between cosmic noise absorption and VHF coherent echo intensityR. A. Makarevitch0R. A. Makarevitch1F. Honary2Department of Communication Systems, Lancaster University, Lancaster, LA1 4WA, UKnow at: Department of Physics, La Trobe University, Victoria, 3086, AustraliaDepartment of Communication Systems, Lancaster University, Lancaster, LA1 4WA, UKWe present examples and statistical analysis of the events with statistically significant correlation between the cosmic noise absorption (CNA) and the signal-to-noise ratio (SNR) of the VHF coherent echo intensity in the area monitored simultaneously by an imaging riometer and two oblique-sounding coherent VHF radars in Northern Scandinavia. By only considering the observations from the narrow riometer beams comparable (in terms of the intersection with the ionosphere) with the VHF radar cells, we identify ~200 one-hour high correlation periods (HCPs) for 2 years near the solar cycle maximum, 2000–2001. The HCP occurrence is maximized in the afternoon (12:00–17:00 UT, MLT≅UT+3), with the secondary peak near the midnight (21:00–02:00 UT). Relative to the VHF echo occurrence, HCPs occur more frequently from 11:00 to 20:00 UT. The diurnal variation of HCP occurrence is similar to that of the 1-h intervals with the lowest mean absorption <i>A</i><0.25dB. </p><p style="line-height: 20px;"> The HCPs are observed more frequently during the winter months, which, combined with the fact that VHF echoes observed during HCPs exhibit features typical for field-aligned E-region irregularities, makes their association with the polar mesospheric echoes (for which some positive CNA/SNR correlation has been reported in the past) very unlikely. Instead, we attribute the high positive CNA/SNR correlation to the synchronous, to a first approximation, variation of the particle fluxes for two different but close sets of energies. </p><p style="line-height: 20px;"> By considering the dependence of the CNA/SNR correlation coefficients for both VHF radars (<i>C<sub>A1</sub></i> and <i>C<sub>A2</sub></i>) upon the correlation between SNRs for two radars (<i>C<sub>12</sub></i>), we show that both coefficients, <i>C<sub>A1</sub></i> and <i>C<sub>A2</sub></i>, and the agreement between them decrease drastically with a <i>C<sub>12</sub></i> decrease, which we interpreted through the progressively increasing role of the spatial inhomogeneity of the processes leading to the enhanced CNA and SNR. In this situation, a similarity between the radio signal collection areas should become important, and we demonstrate that the HCP occurrence and mean correlation coefficient decrease as the riometer beams and radar cells become less comparable in terms of mutual orientation and closeness between the points of maximum sensitivity. <p> <b>Keywords.</b> Ionosphere (Auroral ionosphere; Particle precipitation; Instruments and techniques)https://www.ann-geophys.net/23/1543/2005/angeo-23-1543-2005.pdf |
| spellingShingle | R. A. Makarevitch R. A. Makarevitch F. Honary Correlation between cosmic noise absorption and VHF coherent echo intensity Annales Geophysicae |
| title | Correlation between cosmic noise absorption and VHF coherent echo intensity |
| title_full | Correlation between cosmic noise absorption and VHF coherent echo intensity |
| title_fullStr | Correlation between cosmic noise absorption and VHF coherent echo intensity |
| title_full_unstemmed | Correlation between cosmic noise absorption and VHF coherent echo intensity |
| title_short | Correlation between cosmic noise absorption and VHF coherent echo intensity |
| title_sort | correlation between cosmic noise absorption and vhf coherent echo intensity |
| url | https://www.ann-geophys.net/23/1543/2005/angeo-23-1543-2005.pdf |
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