A superposed epoch study of the effects of solar wind stream interface events on the upper mesospheric and lower thermospheric temperature

Ogunjobi, O.; Sivakumar, Venkataraman; Sivla, W.T.

doi:10.1016/j.asr.2014.07.005

Cited by 10 publications

(11 citation statements)

References 34 publications

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“…8) shows that during an enhanced solar activity, energetic particle precipitation as well as levels of extreme ultraviolent (EUV) radiation could be high. Nevertheless, the quiet time electrodynamics of the Mesosphere and Lower Thermosphere (MLT) region might be driven mainly by tides and gravity waves propagating upward from their source regions in the lower atmosphere (Richardson et al 2001;Ogunjobi et al 2014b). It can be seen that prior to the start of the SuperDARN-PMSE peaks (November), the mean meridional winds become more positive and the zonal winds also grow significantly.…”

Section: Mesospheric Temperature and Winds In Relation To Superdarn-pmsementioning

confidence: 87%

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PMSE long term observations using SuperDARN SANAE HF radar measurements

Ogunjobi¹,

Sivakumar²,

Stephenson³

et al. 2017

Terr. Atmos. Ocean. Sci.

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It is known that the presence of nanometre-scale ice particles and neutral air turbulence in the Polar summer mesosphere modify the D-region plasma, resulting in strong backscatter. These strong backscatters are referred to as Polar Mesosphere Summer Echoes (PMSE). Although studies on PMSE have been ongoing for over three decades, aspects revealed by various instruments are still the subject of discussion. As a sequel to the paper by Ogunjobi et al. (2015), we report on the long term trends and variations in PMSE occurrence probability from Super Dual Auroral Radar Network (SuperDARN) high frequency (HF) radar measurements over the South African National Antarctic Expedition IV (SANAE IV). In this current paper, a simple multiple-filter technique is employed to obtain the occurrence probability rate for SuperDARN-PMSE during the summer periods for the years 1998 -2007. The SuperDARN-PMSE occurrence probability rate in relation to geomagnetic activity is examined. The mesospheric neutral winds and temperature trends during these periods, are further studied and presented in this paper. Both the monthly and diurnal variations in occurrence are consistent with previous reports, confirming the presence of PMSE from SuperDARN SANAE IV radar measurements and the influence of pole to pole mesospheric transport circulation. The special mesospheric mean flow observed prior to the year 2002 is ascribed to the influence of solar activity. The SuperDARN-PMSE occurrence probability peaks with lowered geomagnetic activity. These present results support the hypothesis that the particle precipitation also plays an important role in SuperDARN-PMSE occurrence.

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Section: Mesospheric Temperature and Winds In Relation To Superdarn-pmsementioning

confidence: 87%

“…Intuitively, we expect high Kp index to cause robust cosmic noise absorption (Ogunjobi et al 2014b); hence similar trend in the occurrence rate with Kp and absorption. Nonetheless, the inconsistency might be, partly, due to technical approach for obtaining Kp index, radar, and riometer measurements.…”

Section: Superdarn-pmse Occurrence In Relation Tomentioning

confidence: 99%

PMSE long term observations using SuperDARN SANAE HF radar measurements

Ogunjobi¹,

Sivakumar²,

Stephenson³

et al. 2017

Terr. Atmos. Ocean. Sci.

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“…Remote sensing of electromagnetic waves of cosmic origin is a technique used in studying the state and the structure of the ionosphere (Behera et al 2014). Riometers respond to the integrated absorption of cosmic ray noise through the ionosphere at heights where the electron (up to 30 keV) motion is collision dominated (Morley et al 2010;Ogunjobi et al 2014b). With such sensitivity, riometers data can be examined for ionospheric absorption at the time of dropouts and, by proxy, where the precipitation is localized.…”

Section: Datasets and Event Cleaningmentioning

confidence: 99%

“…Furthermore, the internal correlations between various parameters are one of the problems in the study of solar wind-magnetosphere coupling and responsible for shielding mechanism causing dropouts. For instance, Ogunjobi et al (2014b) noted that within each of several geospace event structures, the magnetic fields might be of different origins and the solar wind parameters that control the solar wind-magnetosphere coupling might also have different behaviours. Thus the whole area is somewhat complex and needs a more specific comparative event-based study to be better observed.…”

Section: Introductionmentioning

confidence: 99%

A comparison of outer electron radiation belt dropouts during solar wind stream interface and magnetic cloud driven storms

2017

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Energetic electrons are trapped in the Earth's radiation belts which occupy a toroidal region between 3 and 7 R E above the Earth's surface. Rapid loss of electrons from the radiation belts is known as dropouts. The source and loss mechanisms regulating the radiation belts population are not yet understood entirely, particularly during geomagnetic storm times. Nevertheless, the dominant loss mechanism may require an event based study to be better observed. Utilizing multiple data sources from the year 1997-2007, this study identifies radiation belt electron dropouts which are ultimately triggered when solar wind stream interfaces (SI) arrived at Earth, or when magnetic clouds (MC) arrived. Using superposed epoch analysis (SEA) technique, a synthesis of multiple observations is performed to reveal loss mechanism which might, perhaps, be a major contributor to radiation belt losses under SI and MC driven storms. Results show an abrupt slower decaying precipitation of electron peak (about 3000 counts/sec) on SI arrival within 5.05 < L < 6.05, which persist till 0.5 day before gradual recovery. This pattern is interpreted as an indication of depleted electrons from bounce lost cone via precipitating mechanism known as relativistic electron microburst. On the other hand, MC shows a pancake precipitating peak extending to lower L (Plasmapause); indicating a combination of electron cyclotron harmonic (ECH) and whistler mode waves as the contributing mechanisms.

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“…Riometers respond to the integrated absorption of cosmic ray noise through the ionosphere (Wilson and Stoker 2002;Hargreaves and Friedrich 2003), usually around 90 km altitude (Ogunjobi et al 2014b). The E-region irregularities due to geomagnetic disturbances can result in aurora (Greenwald et al 1995;Liu et al 2013;Zhang et al 2013).…”

Section: Riometer Datamentioning

confidence: 99%

Evidence of Polar Mesosphere Summer Echoes Observed by SuperDARN SANAE HF Radar in Antarctica

Ogunjobi¹,

Sivakumar²,

Stephenson³

et al. 2015

Terr. Atmos. Ocean. Sci.

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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.

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A superposed epoch study of the effects of solar wind stream interface events on the upper mesospheric and lower thermospheric temperature

Cited by 10 publications

References 34 publications

PMSE long term observations using SuperDARN SANAE HF radar measurements

PMSE long term observations using SuperDARN SANAE HF radar measurements

A comparison of outer electron radiation belt dropouts during solar wind stream interface and magnetic cloud driven storms

Evidence of Polar Mesosphere Summer Echoes Observed by SuperDARN SANAE HF Radar in Antarctica

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