Ion cyclotron harmonics in auroral radar echoes: Real effect or analysis artifact?
Certain analyses of Canadian radar studies of auroral electrojet echoes have apparently shown spectra with multiple ion cyclotron harmonic peaks. On the basis of these, it has been argued that ion cyclotron effects must be important for all echo types seen by VHF radars, not just type 3. We reject t...
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| Veröffentlicht in: | Geophysical research letters 1991-04, Vol.18 (4), p.709-712 |
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| creator | Farley, D. T. Sahr, J. D. Providakes, J. F. |
| description | Certain analyses of Canadian radar studies of auroral electrojet echoes have apparently shown spectra with multiple ion cyclotron harmonic peaks. On the basis of these, it has been argued that ion cyclotron effects must be important for all echo types seen by VHF radars, not just type 3. We reject this conclusion for two reasons: (1) at the altitude of auroral backscatter (∼ 100–120 km) the ion‐neutral collision frequency is much higher than the gyro frequency—ions are essentially unmagnetized; (2) we show that the “high resolution” signal processing algorithm employed does not distinguish between echoes with and without harmonic structure. With a simulation, we show that the algorithm itself can impose apparent quasi harmonic structure onto the spectrum of random noise. |
| doi_str_mv | 10.1029/91GL00122 |
| format | Article |
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T. ; Sahr, J. D. ; Providakes, J. F.</creator><creatorcontrib>Farley, D. T. ; Sahr, J. D. ; Providakes, J. F.</creatorcontrib><description>Certain analyses of Canadian radar studies of auroral electrojet echoes have apparently shown spectra with multiple ion cyclotron harmonic peaks. On the basis of these, it has been argued that ion cyclotron effects must be important for all echo types seen by VHF radars, not just type 3. We reject this conclusion for two reasons: (1) at the altitude of auroral backscatter (∼ 100–120 km) the ion‐neutral collision frequency is much higher than the gyro frequency—ions are essentially unmagnetized; (2) we show that the “high resolution” signal processing algorithm employed does not distinguish between echoes with and without harmonic structure. With a simulation, we show that the algorithm itself can impose apparent quasi harmonic structure onto the spectrum of random noise.</description><identifier>ISSN: 0094-8276</identifier><identifier>EISSN: 1944-8007</identifier><identifier>DOI: 10.1029/91GL00122</identifier><identifier>CODEN: GPRLAJ</identifier><language>eng</language><publisher>Washington, DC: Blackwell Publishing Ltd</publisher><subject>640201 - Atmospheric Physics- Auroral, Ionospheric, & Magetospheric Phenomena ; ALGORITHMS ; Altitude ; AURORAE ; BACKSCATTERING ; CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS ; CURRENTS ; CYCLOTRON FREQUENCY ; CYCLOTRON HARMONICS ; Cyclotrons ; DATA ANALYSIS ; DATA PROCESSING ; Earth, ocean, space ; Echoes ; ELECTRIC CURRENTS ; ELECTROJETS ; Exact sciences and technology ; External geophysics ; HARMONICS ; ION PLASMA WAVES ; ION WAVES ; Ionospheric soundings ; MATHEMATICAL LOGIC ; MEASURING INSTRUMENTS ; NOISE ; OSCILLATIONS ; Physics of the ionosphere ; PLASMA WAVES ; PROCESSING ; RADAR ; RANGE FINDERS ; SCATTERING ; SIGNALS ; Spectra</subject><ispartof>Geophysical research letters, 1991-04, Vol.18 (4), p.709-712</ispartof><rights>Copyright 1991 by the American Geophysical Union.</rights><rights>1991 INIST-CNRS</rights><lds50>peer_reviewed</lds50><woscitedreferencessubscribed>false</woscitedreferencessubscribed><citedby>FETCH-LOGICAL-c4911-3640fdb230898b309276bfca8a193632fa7e3e5720b8400aedad8cbe39737e703</citedby><cites>FETCH-LOGICAL-c4911-3640fdb230898b309276bfca8a193632fa7e3e5720b8400aedad8cbe39737e703</cites></display><links><openurl>$$Topenurl_article</openurl><openurlfulltext>$$Topenurlfull_article</openurlfulltext><thumbnail>$$Tsyndetics_thumb_exl</thumbnail><linktopdf>$$Uhttps://onlinelibrary.wiley.com/doi/pdf/10.1029%2F91GL00122$$EPDF$$P50$$Gwiley$$H</linktopdf><linktohtml>$$Uhttps://onlinelibrary.wiley.com/doi/full/10.1029%2F91GL00122$$EHTML$$P50$$Gwiley$$H</linktohtml><link.rule.ids>230,314,780,784,885,1417,27924,27925,45574,45575</link.rule.ids><backlink>$$Uhttp://pascal-francis.inist.fr/vibad/index.php?action=getRecordDetail&idt=19714746$$DView record in Pascal Francis$$Hfree_for_read</backlink><backlink>$$Uhttps://www.osti.gov/biblio/5186837$$D View this record in Osti.gov$$Hfree_for_read</backlink></links><search><creatorcontrib>Farley, D. T.</creatorcontrib><creatorcontrib>Sahr, J. D.</creatorcontrib><creatorcontrib>Providakes, J. F.</creatorcontrib><title>Ion cyclotron harmonics in auroral radar echoes: Real effect or analysis artifact?</title><title>Geophysical research letters</title><addtitle>Geophys. Res. Lett</addtitle><description>Certain analyses of Canadian radar studies of auroral electrojet echoes have apparently shown spectra with multiple ion cyclotron harmonic peaks. On the basis of these, it has been argued that ion cyclotron effects must be important for all echo types seen by VHF radars, not just type 3. We reject this conclusion for two reasons: (1) at the altitude of auroral backscatter (∼ 100–120 km) the ion‐neutral collision frequency is much higher than the gyro frequency—ions are essentially unmagnetized; (2) we show that the “high resolution” signal processing algorithm employed does not distinguish between echoes with and without harmonic structure. With a simulation, we show that the algorithm itself can impose apparent quasi harmonic structure onto the spectrum of random noise.</description><subject>640201 - Atmospheric Physics- Auroral, Ionospheric, & Magetospheric Phenomena</subject><subject>ALGORITHMS</subject><subject>Altitude</subject><subject>AURORAE</subject><subject>BACKSCATTERING</subject><subject>CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS</subject><subject>CURRENTS</subject><subject>CYCLOTRON FREQUENCY</subject><subject>CYCLOTRON HARMONICS</subject><subject>Cyclotrons</subject><subject>DATA ANALYSIS</subject><subject>DATA PROCESSING</subject><subject>Earth, ocean, space</subject><subject>Echoes</subject><subject>ELECTRIC CURRENTS</subject><subject>ELECTROJETS</subject><subject>Exact sciences and technology</subject><subject>External geophysics</subject><subject>HARMONICS</subject><subject>ION PLASMA WAVES</subject><subject>ION WAVES</subject><subject>Ionospheric soundings</subject><subject>MATHEMATICAL LOGIC</subject><subject>MEASURING INSTRUMENTS</subject><subject>NOISE</subject><subject>OSCILLATIONS</subject><subject>Physics of the ionosphere</subject><subject>PLASMA WAVES</subject><subject>PROCESSING</subject><subject>RADAR</subject><subject>RANGE FINDERS</subject><subject>SCATTERING</subject><subject>SIGNALS</subject><subject>Spectra</subject><issn>0094-8276</issn><issn>1944-8007</issn><fulltext>true</fulltext><rsrctype>article</rsrctype><creationdate>1991</creationdate><recordtype>article</recordtype><recordid>eNqFkU-LFDEQxYMoOK4e_AZBUNxDr5V_ncSLuIszLowKs4rgJVRn0my0p7MmPeh8e7P0sp50T1UUv_d4VUXIUwYnDLh9ZdlqDcA4v0cWzErZGAB9nywAbO25bh-SR6V8BwABgi3I5jyN1B_8kKZcu0vMuzRGX2gcKe5zyjjQjFvMNPjLFMprugl1FPo--ImmTHHE4VBioZin2KOf3jwmD3ocSnhyU4_Il-W7z2fvm_Wn1fnZ23XjpWWsEa2EfttxAcaaToCt4breo0FmRSt4jzqIoDSHzkgADFvcGt8FYbXQQYM4Is9m31Sm6IqPU43o0zjWZE4x0xqhK_Rihq5y-rkPZXK7WHwYBhxD2hfHlQAFrL0TZIZLo6yq4Mv_g63WVnDG9N2o4raiEkxFj2fU51RKDr27ynGH-eAYuOvPutvPVvb5jS0Wj0OfcfSx_BVYzaSW1yudzNyvOITDvw3darNWNXEVNLMglin8vhVg_uHaenTlvn5cuQ_q9GIplxfum_gDi3S8nA</recordid><startdate>199104</startdate><enddate>199104</enddate><creator>Farley, D. T.</creator><creator>Sahr, J. D.</creator><creator>Providakes, J. F.</creator><general>Blackwell Publishing Ltd</general><general>American Geophysical Union</general><scope>BSCLL</scope><scope>IQODW</scope><scope>AAYXX</scope><scope>CITATION</scope><scope>7TG</scope><scope>7TV</scope><scope>7UA</scope><scope>C1K</scope><scope>F1W</scope><scope>H96</scope><scope>KL.</scope><scope>L.G</scope><scope>7SP</scope><scope>8FD</scope><scope>FR3</scope><scope>H8D</scope><scope>KR7</scope><scope>L7M</scope><scope>OTOTI</scope></search><sort><creationdate>199104</creationdate><title>Ion cyclotron harmonics in auroral radar echoes: Real effect or analysis artifact?</title><author>Farley, D. T. ; Sahr, J. D. ; Providakes, J. F.</author></sort><facets><frbrtype>5</frbrtype><frbrgroupid>cdi_FETCH-LOGICAL-c4911-3640fdb230898b309276bfca8a193632fa7e3e5720b8400aedad8cbe39737e703</frbrgroupid><rsrctype>articles</rsrctype><prefilter>articles</prefilter><language>eng</language><creationdate>1991</creationdate><topic>640201 - Atmospheric Physics- Auroral, Ionospheric, & Magetospheric Phenomena</topic><topic>ALGORITHMS</topic><topic>Altitude</topic><topic>AURORAE</topic><topic>BACKSCATTERING</topic><topic>CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS</topic><topic>CURRENTS</topic><topic>CYCLOTRON FREQUENCY</topic><topic>CYCLOTRON HARMONICS</topic><topic>Cyclotrons</topic><topic>DATA ANALYSIS</topic><topic>DATA PROCESSING</topic><topic>Earth, ocean, space</topic><topic>Echoes</topic><topic>ELECTRIC CURRENTS</topic><topic>ELECTROJETS</topic><topic>Exact sciences and technology</topic><topic>External geophysics</topic><topic>HARMONICS</topic><topic>ION PLASMA WAVES</topic><topic>ION WAVES</topic><topic>Ionospheric soundings</topic><topic>MATHEMATICAL LOGIC</topic><topic>MEASURING INSTRUMENTS</topic><topic>NOISE</topic><topic>OSCILLATIONS</topic><topic>Physics of the ionosphere</topic><topic>PLASMA WAVES</topic><topic>PROCESSING</topic><topic>RADAR</topic><topic>RANGE FINDERS</topic><topic>SCATTERING</topic><topic>SIGNALS</topic><topic>Spectra</topic><toplevel>peer_reviewed</toplevel><toplevel>online_resources</toplevel><creatorcontrib>Farley, D. T.</creatorcontrib><creatorcontrib>Sahr, J. D.</creatorcontrib><creatorcontrib>Providakes, J. 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T.</au><au>Sahr, J. D.</au><au>Providakes, J. F.</au><format>journal</format><genre>article</genre><ristype>JOUR</ristype><atitle>Ion cyclotron harmonics in auroral radar echoes: Real effect or analysis artifact?</atitle><jtitle>Geophysical research letters</jtitle><addtitle>Geophys. Res. Lett</addtitle><date>1991-04</date><risdate>1991</risdate><volume>18</volume><issue>4</issue><spage>709</spage><epage>712</epage><pages>709-712</pages><issn>0094-8276</issn><eissn>1944-8007</eissn><coden>GPRLAJ</coden><abstract>Certain analyses of Canadian radar studies of auroral electrojet echoes have apparently shown spectra with multiple ion cyclotron harmonic peaks. On the basis of these, it has been argued that ion cyclotron effects must be important for all echo types seen by VHF radars, not just type 3. We reject this conclusion for two reasons: (1) at the altitude of auroral backscatter (∼ 100–120 km) the ion‐neutral collision frequency is much higher than the gyro frequency—ions are essentially unmagnetized; (2) we show that the “high resolution” signal processing algorithm employed does not distinguish between echoes with and without harmonic structure. With a simulation, we show that the algorithm itself can impose apparent quasi harmonic structure onto the spectrum of random noise.</abstract><cop>Washington, DC</cop><pub>Blackwell Publishing Ltd</pub><doi>10.1029/91GL00122</doi><tpages>4</tpages></addata></record> |
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| ispartof | Geophysical research letters, 1991-04, Vol.18 (4), p.709-712 |
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| language | eng |
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| subjects | 640201 - Atmospheric Physics- Auroral, Ionospheric, & Magetospheric Phenomena ALGORITHMS Altitude AURORAE BACKSCATTERING CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS CURRENTS CYCLOTRON FREQUENCY CYCLOTRON HARMONICS Cyclotrons DATA ANALYSIS DATA PROCESSING Earth, ocean, space Echoes ELECTRIC CURRENTS ELECTROJETS Exact sciences and technology External geophysics HARMONICS ION PLASMA WAVES ION WAVES Ionospheric soundings MATHEMATICAL LOGIC MEASURING INSTRUMENTS NOISE OSCILLATIONS Physics of the ionosphere PLASMA WAVES PROCESSING RADAR RANGE FINDERS SCATTERING SIGNALS Spectra |
| title | Ion cyclotron harmonics in auroral radar echoes: Real effect or analysis artifact? |
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