An annual and a semiannual variation of the upper air density

Paetzold, H. K.; Zschörner, H.

doi:10.1007/bf01992371

Cited by 51 publications

(54 citation statements)

References 9 publications

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“…It is well known from studies based on satellite drag measurements that the upper thermospheric density exhibits annual and semiannual variations. The thermospheric density is at a maximum during the equinox months with a primary minimum in July and secondary minimum in January [e.g., Paetzold and Zschörner, 1961;Qian et al 2009;Lei et al, 2012b], and the amplitude difference between maximum and minimum can depend on both height and solar EUV flux [Bowman et al 2008]. Although we do not endeavor to discuss the mechanisms for the seasonal variations, we note that our results for 350 km show that the density is indeed maximum in the equinox months (8.92Â10 13 m -3 ), and lowest in summer (6.13Â10 13 m -3 ) with the secondary minimum in winter (7.61Â10 13 m -3 ).…”

Section: Discussionmentioning

confidence: 99%

“…We use a form of the equation simplified for field-aligned ion motion in the topside ionosphere at high latitudes. A full derivation and justification for the simplifying assumptions can be found in Ogawa [2002]. The terms that are neglected are: advection due to subsonic flow, the magnetic mirror force resulting from ion temperature anisotropy, the Lorentz force associated with cyclotron motion, the height differential of the stress tensor in the vertical direction, and the force contributed by chemical reactions.…”

Section: Theoretical Frameworkmentioning

confidence: 99%

“…Kosch et al, 2010] and at ESR [cf. Ogawa, 2002] in the topside ionosphere. By restricting our analysis to quiet geomagnetic conditions only, i.e., Kp ≤ 2, Joule heating [Kosch and Nielsen, 1995] and heat flux of ions and electrons due to particle precipitation also become negligible [cf.…”

Section: Theoretical Frameworkmentioning

confidence: 99%

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Thermospheric atomic oxygen density estimates using the EISCAT Svalbard Radar

et al. 2013

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[1] Coupling between the ionized and neutral atmosphere through particle collisions allows an indirect study of the neutral atmosphere through measurements of ionospheric plasma parameters. We estimate the neutral density of the upper thermosphere above~250 km with the European Incoherent Scatter Svalbard Radar (ESR) using the year-long operations of the International Polar Year from March 2007 to February 2008. The simplified momentum equation for atomic oxygen ions is used for field-aligned motion in the steady state, taking into account the opposing forces of plasma pressure gradients and gravity only. This restricts the technique to quiet geomagnetic periods, which applies to most of the International Polar Year during the recent very quiet solar minimum. The method works best in the height rangẽ 300-400 km where our assumptions are satisfied. Differences between Mass Spectrometer and Incoherent Scatter and ESR estimates are found to vary with altitude, season, and magnetic disturbance, with the largest discrepancies during the winter months. A total of 9 out of 10 in situ passes by the CHAMP satellite above Svalbard at 350 km altitude agree with the ESR neutral density estimates to within the error bars of the measurements during quiet geomagnetic periods.

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Section: Discussionmentioning

confidence: 99%

Section: Theoretical Frameworkmentioning

confidence: 99%

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Thermospheric atomic oxygen density estimates using the EISCAT Svalbard Radar

et al. 2013

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“…The semi-annual variation, discovered by Paetzold and Zschorner [1961], leads to density changes of about 30%, with maxima around April and October, although it can be quite irregular in both amplitude and phase [Bowman, 2004]. During periods of low solar activity, it is the dominant cause of changes in density, as can be seen in Figure 2.2.…”

Section: Semi-annual Variationmentioning

confidence: 99%

Thermospheric Density and Wind Determination from Satellite Dynamics

Doornbos¹

2012

Springer Theses

156

212

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“…They include the peak electron density of the ionospheric F2-layer (NmF2) in some parts of the world (Burkard, 1951;Yonezawa and Arima, 1959;Chaman Lal, 1992); the height of the F2-layer peak (hmF2) (Becker, 1967); the neutral air density q in the thermosphere (Paetzold and ZschoÈ rner, 1961); and geomagnetic indices such as Kp and Ap (Bartels, 1963;Green, 1984). Semiannual oscillations also exist in the lower and middle atmosphere.…”

Section: Introductionmentioning

confidence: 99%

Semiannual and annual variations in the height of the ionospheric F2-peak

Rishbeth

Sedgemore-Schulthess²,

Ulich³

2000

Ann. Geophys.

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Abstract. Ionosonde data from sixteen stations are used to study the semiannual and annual variations in the height of the ionospheric F2-peak, hmF2. The semiannual variation, which peaks shortly after equinox, has an amplitude of about 8 km at an average level of solar activity (10.7 cm¯ux = 140 units), both at noon and midnight. The annual variation has an amplitude of about 11 km at northern midlatitudes, peaking in early summer; and is larger at southern stations, where it peaks in late summer. Both annual and semiannual amplitudes increase with increasing solar activity by day, but not at night. The semiannual variation in hmF2 is unrelated to the semiannual variation of the peak electron density NmF2, and is not reproduced by the CTIP and TIME-GCM computational models of the quiet-day thermosphere and ionosphere. The semiannual variation in hmF2 is approximately``isobaric'', in that its amplitude corresponds quite well to the semiannual variation in the height of ®xed pressure-levels in the thermosphere, as represented by the MSIS empirical model. The annual variation is not``isobaric''. The annual mean of hmF2 increases with solar 10.7 cm¯ux, both by night and by day, on average by about 0.45 km/¯ux unit, rather smaller than the corresponding increase of height of constant pressure-levels in the MSIS model. The discrepancy may be due to solar-cycle variations of thermospheric winds. Although geomagnetic activity, which aects thermospheric density and temperature and therefore hmF2 also, is greatest at the equinoxes, this seems to account for less than half the semiannual variation of hmF2. The rest may be due to a semiannual variation of tidal and wave energy transmitted to the thermosphere from lower levels in the atmosphere.

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An annual and a semiannual variation of the upper air density

Cited by 51 publications

References 9 publications

Thermospheric atomic oxygen density estimates using the EISCAT Svalbard Radar

Thermospheric atomic oxygen density estimates using the EISCAT Svalbard Radar

Thermospheric Density and Wind Determination from Satellite Dynamics

Semiannual and annual variations in the height of the ionospheric F2-peak

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