We report on the polar mesosphere summer echoes (PMSE) occurrence probability over SANAE (South African National Antarctic Expedition) IV, for the first time. A matching coincidence method is described and implemented for PMSE extraction from SuperDARN (Super Dual Auroral Radar Network) HF radar. Several SuperDARN-PMSE characteristics are studied during the summer period from years 2005 -2007. The seasonal and interannual SuperDARN-PMSE variations in relation to the mesospheric neutral winds are studied and presented in this paper. The occurrence probability of SuperDARN-PMSE on the day-to-day scale show, predominantly, diurnal variation, with a broader peak between 12 -14 LT and distinct minimum of 22 LT. The SuperDARN-PMSE occurrence probability rate is high in the summer solstice. Seasonal variations show a connection between the SuperDARN-PMSE occurrence probability rate and mesospheric temperature from SABER (Sounding of the Atmosphere using Broadband Emission Radiometry). The seasonal trend for both meridional and zonal winds is very stable year-to-year. Analysis of the neutral wind variations indicates the importance of pole-to-pole circulations in SuperDARN-PMSE generation.

Several possible characteristics of magnetic clouds (MCs) have been discussed in the literature, but none appears to explain all the effects from accumulated observations. MC characteristics range from low proton temperature and plasma beta, to high magnetic field magnitude, to smooth rotation in the direction of the magnetic field thus resulting in strong geomagnetic disturbances. Varied instrumentation which is located not only in SANAE IV, Antarctica, but also at Halley, a same radial distance (L ~ 4) in the southern hemisphere and in the vicinity of a conjugate location in northern hemisphere provide an opportunity to test theories applied to high latitude heating rates on the arrival of MC. The Halley riometer is used to monitor coincidences of absorption with the arrival of MC which was observed on 8 November 2004. Using the Monte Carlo Energy Transport Model (MCETM), the corresponding altitude of electron and proton energy distribution indicates the importance of MC triggered geomagnetic storms on mesosphere dynamics.Key words: Magnetic Cloud, Precipitation, MLT region, Absorption, Energy deposition, L shell Citation: Ogunjobi, O., V. Sivakumar, and N. Mbatha, 2014: A case study of energy deposition and absorption by magnetic cloud electrons and protons over the high latitude stations: Effects on the mesosphere and lower thermosphere. Terr. Atmos. Ocean. Sci., 25,[219][220][221][222][223][224][225][226][227][228][229][230][231][232]

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We study the temporal intensity profile, or pulse shape, of cosmic ray ground level enhancements (GLEs) by calculating the rise (τ r ) and decay (τ d ) times for a small subset of all available events. Although these quantities show very large inter-event variability, a linear dependence of τ d ≈ 3.5τ r is found. We interpret these observational findings in terms of an interplanetary transport model, thereby including the effects of scattering (in pitch-angle) as these particles propagate from (near) the Sun to Earth. It is shown that such a model can account for the observed trends in the pulse shape, illustrating that interplanetary transport must be taken into account when studying GLE events, especially their temporal profiles. Furthermore, depending on the model parameters, the pulse shape of GLEs may be determined entirely by interplanetary scattering, obscuring all information regarding the initial acceleration process, and hence making a classification between impulsive and gradual events, as is traditionally done, superfluous.

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