Energetics of the dayside ionosphere of Venus

Dóbé, Z.; Nagy, Andrew F.; Brace, L. H.; Cravens, T. E.; Luhmann, J. G.

doi:10.1029/93gl01452

Cited by 16 publications

(15 citation statements)

References 16 publications

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“…The uncertainties in the electron temperature profiles are among the largest sources of error in our models. We note here also, however, that the values of T e in the Venus ionosphere have been found to be partly controlled by the interaction of the ionosphere with the solar wind [e.g., Brace et al , 1980], and with the presence or absence of an induced magnetospheric field [e.g., Dobe et al , 1993].…”

Section: Model Resultsmentioning

confidence: 96%

“…The T e profile in the Venus ionosphere has been found to be nearly independent of solar zenith angle [e.g., Miller et al , 1980]. An inverse correlation between n e and T e in the Venus ionosphere has, however, been found by Knudsen et al [1979], Dobe et al [1993], and Mahajan et al [1994]. Breus et al [2004] have adduced evidence from analysis of some of the MGS profiles that T e and E 10.7 in the Martian ionosphere are anticorrelated.…”

Section: Model Resultsmentioning

confidence: 99%

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Morphology of the near‐terminator Martian ionosphere: A comparison of models and data

Fox¹,

Yeager²

2006

J. Geophys. Res.

123

170

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[1] We have constructed low and high solar activity models of the Martian thermosphere/ ionosphere for solar zenith angles from 60 to 90°in 5 degree increments. The solar fluxes that we have adopted are those from the Solar 2000 v2.22 models of Tobiska (2004), without enhancements of the soft X-ray fluxes. The background neutral density and temperature profiles are similar to those that we have recently presented (Fox, 2004). We compute the density profiles for 14 ions and nine neutral species. For all the models, we present altitude profiles of the photoionization rates, electron impact ionization rates, total ion production rates, and the predicted electron density profiles. Each model exhibits both an F 1 peak and an E peak, although the latter usually appears as a shoulder, rather than as a separate peak. The altitudes of the model peaks are found to be slightly too high. We fit the model peak densities to the equation n max,c i = A(cos c) k , where, for an ideal Chapman layer, A is the value of the subsolar peak density, n max,0 i , and the exponent k is 0.5. We compare the behavior of the model electron density profiles to that of a theoretical Chapman layer and to the values of A and k obtained by fitting the Mars Global Surveyor (MGS) radio science electron density profiles for occultation seasons 1, 2, and 4. We also compare our results to those of previous investigators who have analyzed data from earlier Mars missions and those from MGS and from the Mars Express spacecraft. We find that our model best fit values of k for the F 1 peak and those derived from the MGS data are less than the Chapman value of 0.5. We note, however, that the use of spherical geometry alone reduces the value of k below the Chapman value for large solar zenith angles, but the deviation from the experimental values also indicates that there are changes in the neutral atmosphere as the terminator is approached. Our peak densities and predicted subsolar peak densities for both the F 1 and E peaks are somewhat smaller than those derived from the data. This is attributed to the use of the S2K v2.22 solar flux models, rather than the S2K v1.24 models or those from Hinteregger (1981). We also evaluate the neutral, ion, and plasma pressure scale heights at the peaks, 33 km above the peaks and at 250 km for all the models. We find that the solar activity variation of our peak densities are in substantial agreement with those determined by other investigators. We argue that the peaks near 90°solar zenith angle are above the photochemical equilibrium region and fitting these peaks to a Chapman profile is therefore inappropriate.

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Section: Model Resultsmentioning

confidence: 96%

Section: Model Resultsmentioning

confidence: 99%

Morphology of the near‐terminator Martian ionosphere: A comparison of models and data

Fox¹,

Yeager²

2006

J. Geophys. Res.

123

170

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“…The collision frequencies are set v ei = 54.5 × n / T e 3/2 s −1 ( T e is the electron temperature) and v en = 3.68 × 10 −8 [CO 2 ] s −1 [taken from Schunk and Nagy , 2000]. In , k B is the Boltzmann constant, T the plasma temperature, and T 0 the model temperature based on the observed electron temperature [ Dobe et al , 1993] (Figure 1). The coefficient σ is determined so that the altitude profile of σk B T 0 is similar to that of the electron heating/cooling rate of Shinagawa et al [1991] in the subsolar region and σ is proportional to cos θ (θ is the solar zenith angle).…”

Section: Simulation Methodsmentioning

confidence: 99%

The critical solar wind pressure for IMF penetration into the Venus ionosphere

2008

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[1] Early observations and simulations have revealed that the occurrence of IMF penetration into the Venus ionosphere depends on the upstream solar wind pressure, and that IMF is transported into the ionosphere by the downward convection when the solar wind dynamic pressure is relatively large. In this paper, we investigated the critical solar wind pressure for the IMF penetration, by using a two-dimensional global MHD model. The simulations showed that variations in the upstream solar wind pressure (P SW ) affect plasma dynamics and chemistry in the subsolar ionosphere. The chemical plasma loss rate increases as P SW increases, and the amount of plasma loss exceeds that of plasma production when P SW exceeds a certain critical level (P crtc ). On this occasion, the plasma convection in the ionosphere connects to the solar wind flow, and as a result the connected downward convection transports IMF into the ionosphere. The simulations also showed that IMF penetration occurs only when P SW exceeds P crtc , even if the solar wind pressure changes abruptly. The critical pressure is not necessarily equal to the ionospheric peak thermal pressure (P peak ). Our simulations suggested that P crtc is smaller than P peak .Citation: Jin, H., K. Maezawa, and T. Mukai (2008), The critical solar wind pressure for IMF penetration into the Venus ionosphere,

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“…However studies on the dayside Venus ionosphere during magnetised state have been only a few and sometimes with conflicting results. For example, while Elphic et al [1984] found that the parameters Ne and Te were not significantly affected when the ionospheres were in magnetized state, Dobe et al [1993] found a strong correlation between elevated electron temperatures and the induced magnetic fields in the dayside Venus ionosphere. It needs to be mentioned that Elphic et al [1984, p. 125] confined their analysis to altitudes below 200 km “…to avoid the effects of the ionopause on the equilibrium profile of Ne and Te that may be seen at higher altitudes…,” and therefore examined Ne and Te values averaged over the altitude range 150 to 200 km.…”

Section: Introductionmentioning

confidence: 99%

Observations of electron density and electron temperature during large scale magnetic fields in the dayside Venus ionosphere and lesson for Mars

Mahajan

Lodhi

Singh

2010

Geophysical Research Letters

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[1] We first present several dayside electron density (Ne) and electron temperature (Te) profiles observed by the Langmuir probe experiment aboard Pioneer Venus Orbiter when the Venus ionosphere was in a magnetised state and then examine the effect of large scale magnetic fields on the Venus ionosphere. We find that for the magnetised ionospheres, the "top" moves down to altitudes near 200 km and the ionopause layers with steep altitude gradients in Ne and Te start above this altitude. No significant change in electron density and electron temperature is seen within the ionosphere. Occasionally a second ionopause layer is also seen at higher altitudes and the ionospheric region between the two ionopause layers, which is seen to extend to altitudes up to 250 km, too does not indicate any significant change in Ne and Te for these cases. These results have direct relevance to Mars where large scale ionospheric fields have also been observed. Citation: Mahajan, K. K., N. K. Lodhi, and S. Singh (2010), Observations of electron density and electron temperature during large scale magnetic fields in the dayside Venus ionosphere and lesson for Mars, Geophys. Res. Lett., 37, L06202,

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Energetics of the dayside ionosphere of Venus

Cited by 16 publications

References 16 publications

Morphology of the near‐terminator Martian ionosphere: A comparison of models and data

Morphology of the near‐terminator Martian ionosphere: A comparison of models and data

The critical solar wind pressure for IMF penetration into the Venus ionosphere

Observations of electron density and electron temperature during large scale magnetic fields in the dayside Venus ionosphere and lesson for Mars

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