The spectral extent of chorus in the off-equatorial magnetosphere
Magnetospheric chorus waves are a major driver of acceleration and loss in the Earth's outer electron radiation belt. The spectral extent of chorus is a key parameter in quantifying the global effect of chorus on energetic particle populations by determining the range of resonant electron energ...
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| Veröffentlicht in: | Journal of geophysical research. Space physics 2013-04, Vol.118 (4), p.1700-1705 |
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| container_title | Journal of geophysical research. Space physics |
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| creator | Bunch, N. L. Spasojevic, M. Shprits, Y. Y. Gu, X. Foust, F. |
| description | Magnetospheric chorus waves are a major driver of acceleration and loss in the Earth's outer electron radiation belt. The spectral extent of chorus is a key parameter in quantifying the global effect of chorus on energetic particle populations by determining the range of resonant electron energies. However, statistics of spectral properties are sparse, particularly in the off‐equatorial magnetosphere. We use a database of chorus observations from the Polar spacecraft to generate statistics on the normalized chorus frequency (with the respect to the minimum field line gyrofrequency, Ωmin) as a function of magnetic local time (MLT) (0 |
| doi_str_mv | 10.1029/2012JA018182 |
| format | Article |
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Key Points
The normalized chorus peak frequency decreases with R_0, and latitudeLower band chorus has bandwidth <0.1 - narrower than used in most modelsNightside scatter sensitive to peak freq and bandwidth, dayside to peak freq]]></description><identifier>ISSN: 2169-9380</identifier><identifier>EISSN: 2169-9402</identifier><identifier>DOI: 10.1029/2012JA018182</identifier><language>eng</language><publisher>Washington: Blackwell Publishing Ltd</publisher><subject>Diffusion coefficient ; Geophysics ; Latitude ; Magnetic fields ; Spacecraft</subject><ispartof>Journal of geophysical research. Space physics, 2013-04, Vol.118 (4), p.1700-1705</ispartof><rights>2012. American Geophysical Union. All Rights Reserved.</rights><rights>2013. American Geophysical Union. All Rights Reserved.</rights><lds50>peer_reviewed</lds50><oa>free_for_read</oa><woscitedreferencessubscribed>false</woscitedreferencessubscribed><citedby>FETCH-LOGICAL-c4164-665c270c57cb11f7e2e63824d452b7f78cbd0f06c46187b9ac3cc717a113ab563</citedby><cites>FETCH-LOGICAL-c4164-665c270c57cb11f7e2e63824d452b7f78cbd0f06c46187b9ac3cc717a113ab563</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%2F2012JA018182$$EPDF$$P50$$Gwiley$$H</linktopdf><linktohtml>$$Uhttps://onlinelibrary.wiley.com/doi/full/10.1029%2F2012JA018182$$EHTML$$P50$$Gwiley$$H</linktohtml><link.rule.ids>314,777,781,1412,1428,27905,27906,45555,45556,46390,46814</link.rule.ids></links><search><creatorcontrib>Bunch, N. L.</creatorcontrib><creatorcontrib>Spasojevic, M.</creatorcontrib><creatorcontrib>Shprits, Y. Y.</creatorcontrib><creatorcontrib>Gu, X.</creatorcontrib><creatorcontrib>Foust, F.</creatorcontrib><title>The spectral extent of chorus in the off-equatorial magnetosphere</title><title>Journal of geophysical research. Space physics</title><addtitle>J. Geophys. Res. Space Physics</addtitle><description><![CDATA[Magnetospheric chorus waves are a major driver of acceleration and loss in the Earth's outer electron radiation belt. The spectral extent of chorus is a key parameter in quantifying the global effect of chorus on energetic particle populations by determining the range of resonant electron energies. However, statistics of spectral properties are sparse, particularly in the off‐equatorial magnetosphere. We use a database of chorus observations from the Polar spacecraft to generate statistics on the normalized chorus frequency (with the respect to the minimum field line gyrofrequency, Ωmin) as a function of magnetic local time (MLT) (0 < MLT < 24), L‐shell (3 < L < 11), and magnetic latitude (|λ|< 65°). We find that, on average, the chorus spectrum peaks in the range of 0.1–0.4 Ωmin, varying significantly with λ, R0 and MLT. The normalized chorus peak frequency is found to decrease with increasing R0, and decreases with increasing latitude below ∼ 25°. When fit to a Gaussian spectral model, lower band chorus is found to have a bandwidth < 0.1 Ωmin, which is narrower than assumed in most diffusion models. Diffusion coefficients calculated using the University of California at Los Angeles (UCLA) Full Diffusion Code show that wave‐particle interactions on the nightside are highly sensitive to both the peak frequency and bandwidth of chorus, yet on the dayside scattering is mostly sensitive to the peak frequency as a result of the wider latitudinal extent of the waves. We also find that fitting a Gaussian to the logarithm of the spectrum reduces fit errors by over 60%, indicating that inclusion of arbitrary spectral forms may improve the accuracy of wave models within radiation belt simulations.
Key Points
The normalized chorus peak frequency decreases with R_0, and latitudeLower band chorus has bandwidth <0.1 - narrower than used in most modelsNightside scatter sensitive to peak freq and bandwidth, dayside to peak freq]]></description><subject>Diffusion coefficient</subject><subject>Geophysics</subject><subject>Latitude</subject><subject>Magnetic fields</subject><subject>Spacecraft</subject><issn>2169-9380</issn><issn>2169-9402</issn><fulltext>true</fulltext><rsrctype>article</rsrctype><creationdate>2013</creationdate><recordtype>article</recordtype><recordid>eNp90EFLwzAUB_AiCg715gcoePFgNS9pk-w4h26OMVEmO4Y0e3WdXbMlLW7f3shUxIO5JITf_73Hi6JzINdAaPeGEqCjHgEJkh5EHQq8m3RTQg-_30yS4-jM-yUJR4YvyDpRb7rA2K_RNE5XMW4brJvYFrFZWNf6uKzjJgBbFAluWt1YVwa20q81NtavF-jwNDoqdOXx7Os-iV7u76b9YTJ-HDz0e-PEpMDThPPMUEFMJkwOUAikyJmk6TzNaC4KIU0-JwXhJuUgRd7VhhkjQGgApvOMs5Pocl937eymRd-oVekNVpWu0bZeAQfgjPFMBnrxhy5t6-owXVChqRSM06Cu9so4673DQq1dudJup4Coz5Wq3ysNnO35e1nh7l-rRoPnXkYIT0Mq2adK3-D2J6Xdm-KCiUzNJgPVn90Op08Tpjj7AEiFhHk</recordid><startdate>201304</startdate><enddate>201304</enddate><creator>Bunch, N. L.</creator><creator>Spasojevic, M.</creator><creator>Shprits, Y. Y.</creator><creator>Gu, X.</creator><creator>Foust, F.</creator><general>Blackwell Publishing Ltd</general><scope>BSCLL</scope><scope>AAYXX</scope><scope>CITATION</scope><scope>7TG</scope><scope>8FD</scope><scope>H8D</scope><scope>KL.</scope><scope>L7M</scope></search><sort><creationdate>201304</creationdate><title>The spectral extent of chorus in the off-equatorial magnetosphere</title><author>Bunch, N. L. ; Spasojevic, M. ; Shprits, Y. Y. ; Gu, X. ; Foust, F.</author></sort><facets><frbrtype>5</frbrtype><frbrgroupid>cdi_FETCH-LOGICAL-c4164-665c270c57cb11f7e2e63824d452b7f78cbd0f06c46187b9ac3cc717a113ab563</frbrgroupid><rsrctype>articles</rsrctype><prefilter>articles</prefilter><language>eng</language><creationdate>2013</creationdate><topic>Diffusion coefficient</topic><topic>Geophysics</topic><topic>Latitude</topic><topic>Magnetic fields</topic><topic>Spacecraft</topic><toplevel>peer_reviewed</toplevel><toplevel>online_resources</toplevel><creatorcontrib>Bunch, N. L.</creatorcontrib><creatorcontrib>Spasojevic, M.</creatorcontrib><creatorcontrib>Shprits, Y. Y.</creatorcontrib><creatorcontrib>Gu, X.</creatorcontrib><creatorcontrib>Foust, F.</creatorcontrib><collection>Istex</collection><collection>CrossRef</collection><collection>Meteorological & Geoastrophysical Abstracts</collection><collection>Technology Research Database</collection><collection>Aerospace Database</collection><collection>Meteorological & Geoastrophysical Abstracts - Academic</collection><collection>Advanced Technologies Database with Aerospace</collection><jtitle>Journal of geophysical research. Space physics</jtitle></facets><delivery><delcategory>Remote Search Resource</delcategory><fulltext>fulltext</fulltext></delivery><addata><au>Bunch, N. L.</au><au>Spasojevic, M.</au><au>Shprits, Y. Y.</au><au>Gu, X.</au><au>Foust, F.</au><format>journal</format><genre>article</genre><ristype>JOUR</ristype><atitle>The spectral extent of chorus in the off-equatorial magnetosphere</atitle><jtitle>Journal of geophysical research. Space physics</jtitle><addtitle>J. Geophys. Res. Space Physics</addtitle><date>2013-04</date><risdate>2013</risdate><volume>118</volume><issue>4</issue><spage>1700</spage><epage>1705</epage><pages>1700-1705</pages><issn>2169-9380</issn><eissn>2169-9402</eissn><abstract><![CDATA[Magnetospheric chorus waves are a major driver of acceleration and loss in the Earth's outer electron radiation belt. The spectral extent of chorus is a key parameter in quantifying the global effect of chorus on energetic particle populations by determining the range of resonant electron energies. However, statistics of spectral properties are sparse, particularly in the off‐equatorial magnetosphere. We use a database of chorus observations from the Polar spacecraft to generate statistics on the normalized chorus frequency (with the respect to the minimum field line gyrofrequency, Ωmin) as a function of magnetic local time (MLT) (0 < MLT < 24), L‐shell (3 < L < 11), and magnetic latitude (|λ|< 65°). We find that, on average, the chorus spectrum peaks in the range of 0.1–0.4 Ωmin, varying significantly with λ, R0 and MLT. The normalized chorus peak frequency is found to decrease with increasing R0, and decreases with increasing latitude below ∼ 25°. When fit to a Gaussian spectral model, lower band chorus is found to have a bandwidth < 0.1 Ωmin, which is narrower than assumed in most diffusion models. Diffusion coefficients calculated using the University of California at Los Angeles (UCLA) Full Diffusion Code show that wave‐particle interactions on the nightside are highly sensitive to both the peak frequency and bandwidth of chorus, yet on the dayside scattering is mostly sensitive to the peak frequency as a result of the wider latitudinal extent of the waves. We also find that fitting a Gaussian to the logarithm of the spectrum reduces fit errors by over 60%, indicating that inclusion of arbitrary spectral forms may improve the accuracy of wave models within radiation belt simulations.
Key Points
The normalized chorus peak frequency decreases with R_0, and latitudeLower band chorus has bandwidth <0.1 - narrower than used in most modelsNightside scatter sensitive to peak freq and bandwidth, dayside to peak freq]]></abstract><cop>Washington</cop><pub>Blackwell Publishing Ltd</pub><doi>10.1029/2012JA018182</doi><tpages>6</tpages><oa>free_for_read</oa></addata></record> |
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| source | Wiley Online Library Journals Frontfile Complete; Wiley Free Content |
| subjects | Diffusion coefficient Geophysics Latitude Magnetic fields Spacecraft |
| title | The spectral extent of chorus in the off-equatorial magnetosphere |
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