Seasonal variations of equatorial night-time thermospheric meridional winds

Hari, Sridhar; Murthy, B. V. Krishna

doi:10.1016/0021-9169(95)00007-o

Cited by 15 publications

(14 citation statements)

References 16 publications

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“…Thermospheric meridional winds as derived from ionosonde observations are discussed in connection with the MTM by several authors [ Sastri et al , 1994; Hari and Krishna Murthy , 1995; Batista et al , 1997; Niranjan et al , 2006]. Neutral wind directions at low latitudes are often referred to as equatorward/poleward.…”

Section: Discussionmentioning

confidence: 99%

“…Thus, it would be valuable to derive thermospheric winds from ionosonde observations. Several authors describe nighttime thermospheric wind variations and their connection with the MTM at low latitudes [ Sastri et al , 1994; Hari and Krishna Murthy , 1995; Batista et al , 1997; Niranjan et al , 2006]. On the other hand, Fesen [1996] and Colerico et al [2006] conduct simulations with the NCAR thermosphere‐ionosphere‐electrodynamic general circulation model (TIEGCM) and reproduce temperature increases, but fail to reproduce wind abatement.…”

Section: Introductionmentioning

confidence: 99%

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Thermospheric meridional winds as deduced from ionosonde chain at low and equatorial latitudes and their connection with midnight temperature maximum

et al. 2008

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Multipoint ionosonde observation was conducted in Southeast Asia to study ionosphere‐thermosphere coupling. For this observation three ionosondes were installed along the magnetic meridian at 100°E (Southeast Asia Low‐latitude Ionospheric Network: SEALION); two of them were at magnetic conjugate points and the third was near the magnetic equator. The F layer virtual height, h′F, was scaled from nighttime ionograms obtained from September 2004 to August 2005, close to the solar minimum. The height variations at the three locations were used to derive thermospheric winds in the magnetic meridional plane for transequatorial and convergent/divergent components (with respect to the magnetic equator). During northern winter months, a prominent 6‐hr periodic variation of a transequatorial component was found. During northern summer months, a diurnal or semidiurnal variation was dominant. Convergent winds toward the magnetic equator were associated with the occurrence of the midnight temperature maximum at the latitudes between the two conjugate stations as observed by satellite instruments during the solstices. However, no clear evidence was found of abatement of the wind due to the pressure bulge associated with the midnight temperature maximum.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Thermospheric meridional winds as deduced from ionosonde chain at low and equatorial latitudes and their connection with midnight temperature maximum

et al. 2008

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“…• W in the American sector and Hari and Krishna Murthy (1995) in the Indian sector. Both observed reversals in the meridional winds to a poleward direction at local midnight during equinox conditions.…”

Section: Recent Observationsmentioning

confidence: 99%

The current state of investigations regarding the thermospheric midnight temperature maximum (MTM)

Colerico

Mendillo

2002

Journal of Atmospheric and Solar-Terrestrial Physics

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The thermospheric midnight temperature maximum (MTM) is an upper atmospheric e ect found at low latitudes. It is accompanied by an increase in pressure and a signature poleward abatement or reversal in the meridional neutral winds. The MTM exhibits a poleward propagation away from the geographic equator with two secondary maxima developing at approximately ±15• latitude. In this paper, we review early works and recent e orts regarding the MTM. Outstanding questions dealing with seasonal and longitudinal dependencies of the MTM's basic characteristics are discussed. All-sky imaging systems at Arequipa and El Leoncito observed the propagation of 6300 A airglow enhancements related to the MTM past 35• S latitude. This provides useful information on the upper latitude limit of the MTM. TIEGCM modeling e orts simulate the MTM through upward propagating semi-diurnal tides but have di culty reproducing accurately its amplitude and occurrence time. It is suggested that the role of the terdiurnal tidal mode may be more important than previously thought. Recent comparative observation and modeling studies of MTM related 6300 A emission proved unsuccessful. We report that the amplitude of the modeled MTM was not strong enough to instigate the 'midnight collapse' of the F-region needed to produce the airglow signature.

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“…Sastri et al (1994) show northward winds peaking at 02:00 LT with equatorward surges at 00:00 LT and 05:00 LT in December 1992, at Sriharikota (13.7 • N) that agree well with the brightening and the wanings we see at these times. Likewise, Hari and Krishna Murthy (1995) show the same poleward wind at 02:00 LT in their averaged winter data, and an equatorward wind after that.…”

Section: Midnight Pressure Bulgementioning

confidence: 60%

Brightness variations of the northern 630nm intertropical arc and the midnight pressure bulge over Eritrea

et al. 2004

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Abstract.The nightglow brightness at 630 nm from the thermospheric O( 1 D) layer was monitored nightly at Asmara, Eritrea (15.4 • N, 39.9 • E, 7 • N dip) with an all-sky imager. Averages of north-south strips of the images enabled contour plots of brightness on a latitude vs. local time grid. The contours show the movement of the intertropical arc southward before midnight, staying just north of Asmara after midnight, and gradually brightening to a maximum at 02:00 h local civil time, 02:00 LT, after which it disappears before dawn. It is argued that all features of the plots can be explained by known mechanisms capable of driving ions along magnetic field lines, including the fountain effect, summer to winter transequatorial winds, and the midnight pressure bulge.The 02:00 LT brightness maximum is the most striking and the most persistent feature in the data. The persistence of the location of the 02:00 LT brightening is attributed to a pressure bulge centered on the geographic equator at midnight and extending to higher latitudes with increasing local time in both the winter and the summer hemispheres. The bulge is shown to be stronger near solstice than near equinox, confirming earlier work.

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Seasonal variations of equatorial night-time thermospheric meridional winds

Cited by 15 publications

References 16 publications

Thermospheric meridional winds as deduced from ionosonde chain at low and equatorial latitudes and their connection with midnight temperature maximum

Thermospheric meridional winds as deduced from ionosonde chain at low and equatorial latitudes and their connection with midnight temperature maximum

The current state of investigations regarding the thermospheric midnight temperature maximum (MTM)

Brightness variations of the northern 630nm intertropical arc and the midnight pressure bulge over Eritrea

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