Daytime thermosphere above Millstone Hill during severe geomagnetic storms

Mikhailov, A. V.; Foster, J.

doi:10.1029/97ja00879

Cited by 53 publications

(43 citation statements)

References 22 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…On the other hand the temperature dependence given by McFarland et al (1973) is very steep. It was e ciently used in our calculations to mimic the increase of this reaction rate due to vibrationally excited N 2 at high solar activity (Mikhailov and FoÈ rster, 1997;Mikhailov and Foster, 1997;Mikhailov and Schlegel, 1998). Recent owing afterglow measurements by Hierl et al (1997) carried out at T n T i T v 300±1600 K con®rmed the results by Schmeltekopf et al (1968) and showed that the translation energy dependencies for the vibrationally excited species are the same as those for the species being at the ground level (v 0).…”

Section: Introductionsupporting

confidence: 51%

A self-consistent estimate of O+ + N2 − rate coefficient and total EUV solar flux with λ < 1050 Å using EISCAT observations

Михайлов

Schlegel

2000

Ann. Geophys.

Self Cite

View full text Add to dashboard Cite

Abstract. There are di erences between existing models of solar EUV with k < 1050 A Ê and between laboratory measurements of the O + + N 2 ± reaction rate coecient, both parameters being crucial for the F2-region modeling. Therefore, indirect aeronomic estimates of these parameters may be useful for qualifying the existing EUV models and the laboratory measured O + + N 2 ± rate coe cient. A modi®ed self-consistent method for daytime F2-region modeling developed by Mikhailov and Schlegel was applied to EISCAT observations (32 quiet summer and equinoctial days) to estimate the set of main aeronomic parameters. Three laboratory measured temperature dependencies for the O + + N 2 ± rate coe cient were used in our calculations to ®nd self-consistent factors both for this rate coe cient and for the solar EUV¯ux model from Nusinov. Independent of the rate coe cient used, the calculated values group around the temperature dependence recently measured by Hierl et al. in the 850±1400 K temperature range. Therefore, this rate coe cient may be considered as the most preferable and is recommended for aeronomic calculations. The calculated EUV¯ux shows a somewhat steeper dependence on solar activity than both, the Nusinov and the EUVAC models predict. In practice both EUV models may be recommended for the F2-region electron density calculations with the total EUV¯ux shifted by 25% for the EUVAC and Nusinov models, correspondingly.

show abstract

Section: Introductionsupporting

confidence: 51%

A self-consistent estimate of O+ + N2 − rate coefficient and total EUV solar flux with λ < 1050 Å using EISCAT observations

Михайлов

Schlegel

2000

Ann. Geophys.

Self Cite

View full text Add to dashboard Cite

show abstract

“…No correction was applied to these profiles as the calculated O + /Ne ratio for quiet time conditions is close to the standard Millstone Hill ion composition model being used during their data development. Such correction makes sense only for storm conditions when deviations from the standard O + /Ne model are essential [Mikhailov and Foster, 1997;Mikhailov and Schlegel, 1998]. All aeronomic parameters are found simultaneously constituting a self-consistent set.…”

Section: Observations and The Methods Of Analysismentioning

confidence: 99%

On the mechanism of seasonal and solar cycleN_mF₂variations: A quantitative estimate of the main parameters contribution using incoherent scatter radar observations

Mikhailov

Perrone

2011

J. Geophys. Res.

Self Cite

View full text Add to dashboard Cite

[1] Seasonal (winter/summer) and solar cycle N m F 2 variations as well as summer saturation effect in N m F 2 have been analyzed using Millstone Hill incoherent scatter radar (ISR) daytime observations. A self-consistent approach to the Ne(h) modeling has been applied to extract from ISR observations a consistent set of main aeronomic parameters and to estimate their quantitative contribution to the observed N m F 2 variations. The retrieved aeronomic parameters are independent of uncertainties in thermosphere and solar EUV empirical models, and this is a distinguishing feature of the present consideration. Different temperatures in winter and in summer in the course of solar cycle overlapped on the O + + N 2 reaction rate coefficient temperature dependence result in different N m F 2 dependences on solar activity: a steep practically linear increase with a tendency to turn up in January (contrary to international reference ionosphere prediction) and a slow increase with a tendency to saturate at high solar activity in July despite increasing solar EUV irradiation. In winter the EUV flux and thermospheric parameters provide approximately equal contributions to the N m F 2 increase, while in summer the contribution of thermospheric parameters is small. Both in winter and in summer the variations of atomic oxygen [O] are small at the F 2 layer peak, and its contribution is small compared to linear loss coefficient, b. It is shown that the summer saturation effect in N m F 2 under high solar activity is not just reduced to O/N 2 or EUV flux solar cycle variations but is determined by b via the g 1 temperature dependence. A new mechanism (qualitative) to explain the December anomaly in N m F 2 is proposed. It is based on the idea that the areas of atomic oxygen production and its loss are spatially separated and that time is required to transfer [O] from one area to the other where [O] associates in a three-body collision. Therefore, under a 7% increase in the O 2 dissociation rate due to the Sun-Earth distance decrease in December-January compared to June-July, an accumulation of atomic oxygen should take place in the thermosphere in the vicinity of the December solstice resulting in a 21% N m F 2 increase, which is close to the observed global December effect.Citation: Mikhailov, A. V., and L. Perrone (2011), On the mechanism of seasonal and solar cycle N m F 2 variations: A quantitative estimate of the main parameters contribution using incoherent scatter radar observations,

show abstract

“…For example, Joule heating causes ion upwelling (Kivanc and Heelis, 1999), gravity waves (Williams et al, 1988;Buonsanto et al, 1999;Balthazor et al, 1997), winds, which in turn change the F-region electron concentrations (Emery et al, 1999) and thermospheric composition (Hecht et al, 1999;Mikhailov and Foster, 1997).…”

Section: Introductionmentioning

confidence: 99%

The variability of Joule heating, and its effects on the ionosphere and thermosphere

et al. 2001

View full text Add to dashboard Cite

Abstract.A considerable fraction of the solar wind energy that crosses the magnetopause ends up in the high-latitude thermosphere-ionosphere system as a result of Joule heating, the consequences of which are very significant and global in nature. Often Joule heating calculations use hourly averages of the electric field, rather than the time-varying electric field. This leads to an underestimation of the heating. In this paper, we determine the magnitude of the underestimation of Joule heating by analysing electric field data from the EISCAT Incoherent Scatter Radar, situated at the 67 • E magnetic latitude. We find that the underestimation, using hourly-averaged electric field values, is normally ∼20%, with an upper value of about 65%. We find that these values are insensitive to changes in solar flux, magnetic activity and magnetic local time, implying that the electric field fluctuations are linear related to the amplitude of the electric field. Assuming that these changes are representative of the entire auroral oval, we then use a coupled ionosphere-thermosphere model to calculate the local changes these underestimations in the heating rate cause to the neutral temperature, mean molecular mass and meridional wind. The changes in each parameter are of the order of a few percent but they result in a reduction in the peak F-region concentration of ∼20% in the summer hemisphere at high latitudes, and about half of this level in the winter hemisphere. We suggest that these calculations could be used to add corrections to modelled values of Joule heating.

show abstract

Daytime thermosphere above Millstone Hill during severe geomagnetic storms

Cited by 53 publications

References 22 publications

A self-consistent estimate of O<sup>+</sup> + N<sub>2</sub> − rate coefficient and total EUV solar flux with λ < 1050 Å using EISCAT observations

A self-consistent estimate of O<sup>+</sup> + N<sub>2</sub> − rate coefficient and total EUV solar flux with λ < 1050 Å using EISCAT observations

On the mechanism of seasonal and solar cycleN_mF₂variations: A quantitative estimate of the main parameters contribution using incoherent scatter radar observations

The variability of Joule heating, and its effects on the ionosphere and thermosphere

Contact Info

Product

Resources

About

Daytime thermosphere above Millstone Hill during severe geomagnetic storms

Cited by 53 publications

References 22 publications

A self-consistent estimate of O&lt;sup&gt;+&lt;/sup&gt; + N&lt;sub&gt;2&lt;/sub&gt; − rate coefficient and total EUV solar flux with λ &lt; 1050 Å using EISCAT observations

A self-consistent estimate of O&lt;sup&gt;+&lt;/sup&gt; + N&lt;sub&gt;2&lt;/sub&gt; − rate coefficient and total EUV solar flux with λ &lt; 1050 Å using EISCAT observations

On the mechanism of seasonal and solar cycleNmF2variations: A quantitative estimate of the main parameters contribution using incoherent scatter radar observations

The variability of Joule heating, and its effects on the ionosphere and thermosphere

Contact Info

Product

Resources

About

A self-consistent estimate of O<sup>+</sup> + N<sub>2</sub> − rate coefficient and total EUV solar flux with λ < 1050 Å using EISCAT observations

A self-consistent estimate of O<sup>+</sup> + N<sub>2</sub> − rate coefficient and total EUV solar flux with λ < 1050 Å using EISCAT observations

On the mechanism of seasonal and solar cycleN_mF₂variations: A quantitative estimate of the main parameters contribution using incoherent scatter radar observations