Inverting ionospheric radio occultation measurements using maximum entropy

Hysell, D. L.

doi:10.1029/2007rs003635

Cited by 20 publications

(16 citation statements)

References 20 publications

(25 reference statements)

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“…3, multiple precipitation layers were excluded from identification. Thus, we are not subject to false positives due to noisy retrievals as described by Hysell (2007). When excess noise was visible in the E region, we denoted this as an "ambiguous" case.…”

Section: Discussionmentioning

confidence: 99%

“…Due to the nature of the retrieval process (Hysell, 2007;Yue et al, 2010;Hajj and Romans, 1998), retrieval errors will not introduce a single electron density enhancement layer of the kind we are using to identify precipitation. The background E region electron density, defined as the smoothly decreasing component, could certainly be in error.…”

Section: Discussionmentioning

confidence: 99%

“…Accuracy is degraded below the F2 peak due to horizontal variation of electron density along the ray path and other factors (Yue et al, 2010;Nicolls et al, 2009;Hysell, 2007). This study focuses on prominent layer features below the F2 peak density that are likely to be the ionization signatures of EPP.…”

Section: Observationsmentioning

confidence: 99%

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Use of radio occultation to probe the high-latitude ionosphere

et al. 2015

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Abstract.We have explored the use of COSMIC data to provide valuable scientific information on the ionospheric impacts of energetic particle precipitation during geomagnetic storms. Ionospheric electron density in the E region, and hence ionospheric conductivity, is significantly altered by precipitating particles from the magnetosphere. This has global impacts on the thermosphere-ionosphere because of the important role of conductivity on high-latitude Joule heating. Two high-speed stream (HSS) and two coronal mass ejection (CME) storms are examined with the COSMIC data. We find clear correlation between geomagnetic activity and electron density retrievals from COSMIC. At nighttime local times, the number of profiles with maximum electron densities in the E layer (below 200 km altitude) is well correlated with geomagnetic activity. We interpret this to mean that electron density increases due to precipitation are captured by the COSMIC profiles. These "E-layer-dominant ionosphere" (ELDI) profiles have geomagnetic latitudes that are consistent with climatological models of the auroral location. For the two HSS storms that occurred in May of 2011 and 2012, a strong hemispheric asymmetry is observed, with nearly all the ELDI profiles found in the Southern, less sunlit, Hemisphere. Stronger aurora and precipitation have been observed before in winter hemispheres, but the degree of asymmetry deserves further study. For the two CME storms, occurring in July and November of 2012, large increases in the number of ELDI profiles are found starting in the storm's main phase but continuing for several days into the recovery phase. Analysis of the COSMIC profiles was extended to all local times for the July 2012 CME storm by relaxing the ELDI criterion and instead visually inspecting all profiles above 50 • magnetic latitude for signatures of precipitation in the E region. For 9 days during the July 2012 period, we find a signature of precipitation occurs nearly uniformly in local time, although the magnitude of electron density increase may vary with local time. The latitudinal extent of the precipitation layers is generally consistent with auroral climatology. However, after the storm main phase on 14 July 2012 the precipitation tended to be somewhat more equatorward than the climatology (by about 5-10 • latitude) and equatorward of the auroral boundary data acquired from the SSUSI sensor onboard the F18 DMSP satellite. We conclude that, if analyzed appropriately, high-latitude COSMIC profiles have the potential to contribute to our understanding of MI coupling processes and extend and improve existing models of the auroral region.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Use of radio occultation to probe the high-latitude ionosphere

et al. 2015

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“…Despite the power of this method, the limitations of radio occultation have been noted, particularly when retrieving electron density structure below the F-region peak density (Hysell, 2007;Lei et al, 2007;Wu et al, 2009a;Yue et al, 2010). The standard Abel inversion method to retrieve electron density from total electron content is analytically correct in the case of a spherically symmetric ionosphere (electron density depends only on radial distance).…”

Section: Introductionmentioning

confidence: 97%

Electron density retrieval from occulting GNSS signals using a gradient-aided inversion technique

Kulikov

Mannucci

et al. 2011

Advances in Space Research

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“…Thus the error introduced in the beginning iteration will be transferred and amplified in the successive iterations. To solve this problem, some improving methods, like the regularization inversion and the maximum entropy inversion [7,8] , were proposed. Combining the principles of these two improved versions, we propose in this paper a new algorithm for the calculation of the ionospheric occultation: maximum entropy regularization method.…”

Section: Introductionmentioning

confidence: 99%