Ionospheric Radiowave Absorption Processes in the Dayside Polar Cap Boundary Regions

Stauning, P.

doi:10.1007/978-94-011-5214-3_18

Cited by 2 publications

(3 citation statements)

References 46 publications

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“…Stauning et al, 1995b;Stauning, 1998) and also at the Japanese IRIS located at NyÅlesund on Svalbard (e.g. Nishino et al, 1999), both at higher magnetic latitudes and closer to the polar cap boundary than the present observations.…”

Section: Substorm Driftssupporting

confidence: 58%

“…On average, these bursts last for 10 to 15 min with a ∼ 10-min separation suggesting a Pc5 like modulation. Stauning (1998) and Kikachi et al (1988) observed some slowly varying absorption events to be related to strong pulsations in the Pc4-5 range. Stauning et al (1995b) and Stauning (1998) describe the theory that absorption in the morning sector displaying this slowly varying nature was related to the drizzle of eastward drifting electrons from substorm activity on the nightside.…”

Section: Substorm Driftsmentioning

confidence: 93%

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Substorm related changes in precipitation in the dayside auroral zone – a multi instrument case study

et al. 2002

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Abstract.A period (08:10-14:40 MLT, 11 February 1997) of enhanced electron density in the D-and E-regions is investigated using EISCAT, IRIS and other complementary instruments. The precipitation is determined to be due to substorm processes occurring close to magnetic midnight. Energetic electrons drift eastward after substorm injection and precipitate in the morning sector. The precipitation is triggered by small pulses in the solar wind pressure, which drive wave particle interactions. The characteristic energy of precipitation is inferred from drift timing on different L-shells and apparently verified by EISCAT measurements. The IMF influence on the precipitation in the auroral zone is also briefly discussed. A large change in the precipitation spectrum is attributed to increased numbers of ions and much reduced electron fluxes. These are detected by a close passing DMSP satellite. The possibility that these ions are from the low latitude boundary layer (LLBL) is discussed with reference to structured narrow band Pc1 waves observed by a search coil magnetometer, co-located with IRIS. The intensity of the waves grows with increased distance equatorward of the cusp position (determined by both satellite and HF radar), contrary to expectations if the precipitation is linked to the LLBL. It is suggested that the ion precipitation is, instead, due to the recovery phase of a small geomagnetic storm, following on from very active conditions. The movement of absorption in the later stages of the event is compared with observations of the ionospheric convection velocities. A good agreement is found to exist in this time interval suggesting that E ×B drift has become the dominant drift mechanism over the gradientcurvature drift separation of the moving absorption patches observed at the beginning of the morning precipitation event.

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Section: Substorm Driftssupporting

confidence: 58%

Section: Substorm Driftsmentioning

confidence: 93%

Substorm related changes in precipitation in the dayside auroral zone – a multi instrument case study

et al. 2002

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“…The riometer technique for examining particle density enhancements in the ionospheric D‐ and lower E‐regions (75–120 km altitude) is based on the absorption of broadband RF energy radiated by stellar sources in the galaxy and called cosmic noise. At high latitudes the precipitation of electrons of energies from 10–100 keV, and high‐energy solar protons to above 10 MeV from both the dayside and night‐side magnetosphere, increases D‐ and E‐region electron density resulting in enhanced cosmic noise absorption (CNA) in the 2–55 MHz frequency range [e.g., Stauning , 1998].…”

Section: Mst Radar and Riometer Measurementsmentioning

confidence: 99%

Is there a causal relationship between cosmic noise absorption and PMSE?

Morris

Terkildsen

Holdsworth

et al. 2005

Geophysical Research Letters

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[1] We report on the first Southern Hemisphere comparison between polar mesosphere summer echoes (PMSE) and cosmic noise absorption (CNA). Observations were obtained during the austral summer of 2003 -2004 from a 55 MHz MST radar, a 38.2 MHz imaging riometer and a 30 MHz standard riometer all co-located at Davis, Antarctica (68.6°S). Case study PMSE events suggest that CNA plays a role in the intensification of established dayside PMSE possibly linked with soft electron precipitation from the polar cusp, and indeed with a similar effect and moreover with the creation of night-side PMSE connected with hard auroral electron precipitation. Although Pearson correlation coefficients are not that high (i.e., 0.423), Spearman rank correlation coefficients of 0.315, with 123 degrees of freedom well above the 99% confidence limits, established that a weak correlation between CNA and PMSE intensity exists. We use this result to discuss two unexplained properties of PMSE: (i) diurnal minimum near $15-21 UT; and (ii) non-linear intensity variation as a function of latitude. Surprisingly, this study presents only the second analysis of this kind using co-located instruments.

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Ionospheric Radiowave Absorption Processes in the Dayside Polar Cap Boundary Regions

Cited by 2 publications

References 46 publications

Substorm related changes in precipitation in the dayside auroral zone – a multi instrument case study

Substorm related changes in precipitation in the dayside auroral zone – a multi instrument case study

Is there a causal relationship between cosmic noise absorption and PMSE?

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