Dynamical critical scaling of electric field fluctuations in the greater cusp and magnetotail implied by HF radar observations of F-region Doppler velocity
Akasofu's solar wind ε parameter describes the coupling of solar wind energy to the magnetosphere and ionosphere. Analysis of fluctuations in ε using model independent scaling techniques including the peaks of probability density functions (PDFs) and generalised struc...
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2006-03-01
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| Series: | Annales Geophysicae |
| Online Access: | https://www.ann-geophys.net/24/689/2006/angeo-24-689-2006.pdf |
| _version_ | 1818011428394631168 |
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| author | M. L. Parkinson |
| author_facet | M. L. Parkinson |
| author_sort | M. L. Parkinson |
| collection | DOAJ |
| description | Akasofu's solar wind ε parameter describes the coupling of
solar wind energy to the magnetosphere and ionosphere. Analysis of
fluctuations in ε using model independent scaling techniques including the
peaks of probability density functions (PDFs) and generalised structure
function (GSF) analysis show the fluctuations were self-affine
(mono-fractal, single exponent scaling) over 9 octaves of time scale from
~46 s to ~9.1 h. However, the peak scaling exponent α<sub>0</sub> was a
function of the fluctuation bin size, so caution is required when comparing
the exponents for different data sets sampled in different ways. The same
generic scaling techniques revealed the organisation and functional form of
concurrent fluctuations in azimuthal magnetospheric electric fields implied
by SuperDARN HF radar measurements of line-of-sight Doppler velocity, <i>v</i><sub>LOS</sub>,
made in the high-latitude austral ionosphere. The PDFs of <i>v</i><sub>LOS</sub>
fluctuation were calculated for time scales between 1 min and 256 min, and
were sorted into noon sector results obtained with the Halley radar, and
midnight sector results obtained with the TIGER radar. The PDFs were further
sorted according to the orientation of the interplanetary magnetic field, as
well as ionospheric regions of high and low Doppler spectral width. High
spectral widths tend to occur at higher latitude, mostly on open field lines
but also on closed field lines just equatorward of the open-closed boundary,
whereas low spectral widths are concentrated on closed field lines deeper
inside the magnetosphere. The <i>v</i><sub>LOS</sub> fluctuations were most self-affine
(i.e. like the solar wind ε parameter) on the high spectral width field lines
in the noon sector ionosphere (i.e. the greater cusp), but suggested
multi-fractal behaviour on closed field lines in the midnight sector (i.e. the
central plasma sheet). Long tails in the PDFs imply that "microbursts"
in ionospheric convection occur far more frequently, especially on open
field lines, than can be captured using the effective Nyquist frequency and
volume resolution of SuperDARN radars. |
| first_indexed | 2024-04-14T06:07:38Z |
| format | Article |
| id | doaj.art-7bcc6d2faccb471fb5bdb37d4e36ee7d |
| institution | Directory Open Access Journal |
| issn | 0992-7689 1432-0576 |
| language | English |
| last_indexed | 2024-04-14T06:07:38Z |
| publishDate | 2006-03-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Annales Geophysicae |
| spelling | doaj.art-7bcc6d2faccb471fb5bdb37d4e36ee7d2022-12-22T02:08:28ZengCopernicus PublicationsAnnales Geophysicae0992-76891432-05762006-03-012468970510.5194/angeo-24-689-2006Dynamical critical scaling of electric field fluctuations in the greater cusp and magnetotail implied by HF radar observations of F-region Doppler velocityM. L. Parkinson0Department of Physics, La Trobe University, Bundoora Campus, Victoria 3086, AustraliaAkasofu's solar wind ε parameter describes the coupling of solar wind energy to the magnetosphere and ionosphere. Analysis of fluctuations in ε using model independent scaling techniques including the peaks of probability density functions (PDFs) and generalised structure function (GSF) analysis show the fluctuations were self-affine (mono-fractal, single exponent scaling) over 9 octaves of time scale from ~46 s to ~9.1 h. However, the peak scaling exponent α<sub>0</sub> was a function of the fluctuation bin size, so caution is required when comparing the exponents for different data sets sampled in different ways. The same generic scaling techniques revealed the organisation and functional form of concurrent fluctuations in azimuthal magnetospheric electric fields implied by SuperDARN HF radar measurements of line-of-sight Doppler velocity, <i>v</i><sub>LOS</sub>, made in the high-latitude austral ionosphere. The PDFs of <i>v</i><sub>LOS</sub> fluctuation were calculated for time scales between 1 min and 256 min, and were sorted into noon sector results obtained with the Halley radar, and midnight sector results obtained with the TIGER radar. The PDFs were further sorted according to the orientation of the interplanetary magnetic field, as well as ionospheric regions of high and low Doppler spectral width. High spectral widths tend to occur at higher latitude, mostly on open field lines but also on closed field lines just equatorward of the open-closed boundary, whereas low spectral widths are concentrated on closed field lines deeper inside the magnetosphere. The <i>v</i><sub>LOS</sub> fluctuations were most self-affine (i.e. like the solar wind ε parameter) on the high spectral width field lines in the noon sector ionosphere (i.e. the greater cusp), but suggested multi-fractal behaviour on closed field lines in the midnight sector (i.e. the central plasma sheet). Long tails in the PDFs imply that "microbursts" in ionospheric convection occur far more frequently, especially on open field lines, than can be captured using the effective Nyquist frequency and volume resolution of SuperDARN radars.https://www.ann-geophys.net/24/689/2006/angeo-24-689-2006.pdf |
| spellingShingle | M. L. Parkinson Dynamical critical scaling of electric field fluctuations in the greater cusp and magnetotail implied by HF radar observations of F-region Doppler velocity Annales Geophysicae |
| title | Dynamical critical scaling of electric field fluctuations in the greater cusp and magnetotail implied by HF radar observations of F-region Doppler velocity |
| title_full | Dynamical critical scaling of electric field fluctuations in the greater cusp and magnetotail implied by HF radar observations of F-region Doppler velocity |
| title_fullStr | Dynamical critical scaling of electric field fluctuations in the greater cusp and magnetotail implied by HF radar observations of F-region Doppler velocity |
| title_full_unstemmed | Dynamical critical scaling of electric field fluctuations in the greater cusp and magnetotail implied by HF radar observations of F-region Doppler velocity |
| title_short | Dynamical critical scaling of electric field fluctuations in the greater cusp and magnetotail implied by HF radar observations of F-region Doppler velocity |
| title_sort | dynamical critical scaling of electric field fluctuations in the greater cusp and magnetotail implied by hf radar observations of f region doppler velocity |
| url | https://www.ann-geophys.net/24/689/2006/angeo-24-689-2006.pdf |
| work_keys_str_mv | AT mlparkinson dynamicalcriticalscalingofelectricfieldfluctuationsinthegreatercuspandmagnetotailimpliedbyhfradarobservationsoffregiondopplervelocity |