Thermal electron heating rate: A derivation

Hoegy, W. R.

doi:10.1029/ja089ia02p00977

Cited by 18 publications

(9 citation statements)

References 22 publications

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“…Previous studies which have stopped the sum at a transition energy E t $ 2 eV where the total distribution function no longer deviates detectably from a Maxwellian can underestimate the total heating rate by as much as 40% [Schunk and Nagy, 1978;Hoegy, 1984]. One solution to this problem is to include an extra "surface term" which is evaluated at E t [Hoegy, 1984]. In this study we do not define a transition energy and instead consider the photoelectron distribution to be defined all the way to the thermal energy.…”

Section: Thermal Electron Heating Ratesmentioning

confidence: 97%

“…It is very important to continue the sum in all the way down to the thermal energy since most of the heating comes from the lowest energy photoelectrons. Previous studies which have stopped the sum at a transition energy

{scriptE}_{t} \sim 2 eV

where the total distribution function no longer deviates detectably from a Maxwellian can underestimate the total heating rate by as much as 40% [ Schunk and Nagy , 1978; Hoegy , 1984]. One solution to this problem is to include an extra “surface term” which is evaluated at

E_{t}

[ Hoegy , 1984].…”

Section: Model Descriptionmentioning

confidence: 99%

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SAMI2‐PE: A model of the ionosphere including multistream interhemispheric photoelectron transport

et al. 2012

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[1] In order to improve model comparisons with recently improved incoherent scatter radar measurements at the Jicamarca Radio Observatory we have added photoelectron transport and energy redistribution to the two dimensional SAMI2 ionospheric model. The photoelectron model uses multiple pitch angle bins, includes effects associated with curved magnetic field lines, and uses an energy degradation procedure which conserves energy on coarse, non-uniformly spaced energy grids. The photoelectron model generates secondary electron production rates and thermal electron heating rates which are then passed to the fluid equations in SAMI2. We then compare electron and ion temperatures and electron densities of this modified SAMI2 model with measurements of these parameters over a range of altitudes from 90 km to 1650 km (L = 1.26) over a 24 hour period. The new electron heating model is a significant improvement over the semi-empirical model used in SAMI2. The electron temperatures above the F-peak from the modified model qualitatively reproduce the shape of the measurements as functions of time and altitude and quantitatively agree with the measurements to within $30% or better during the entire day, including during the rapid temperature increase at dawn.

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Section: Thermal Electron Heating Ratesmentioning

confidence: 97%

{scriptE}_{t} \sim 2 eV

E_{t}

[ Hoegy , 1984].…”

Section: Model Descriptionmentioning

confidence: 99%

SAMI2‐PE: A model of the ionosphere including multistream interhemispheric photoelectron transport

et al. 2012

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“…The computation of the suprathermal electron heating rate, Q phe , from the suprathermal flux is described by Hoegy [1984], Varney et al [2012], and Varney [2012]. The heating rate is computed by summing all the energy lost by suprathermal electrons to Coulomb collisions, and the algorithm is guaranteed to numerically conserve energy [Varney, 2012].…”

Section: Thermal Electron Equationsmentioning

confidence: 99%

Heating of the sunlit polar cap ionosphere by reflected photoelectrons

2014

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Photoelectrons escape from the ionosphere on sunlit polar cap field lines. In order for those field lines to carry zero current without significant heavy ion outflow or cold electron inflow, field-aligned potential drops must form to reflect a portion of the escaping photoelectron population back to the ionosphere. Using a 1-D ionosphere-polar wind model and measurements from the Resolute Bay Incoherent Scatter Radar (RISR-N), this paper shows that these reflected photoelectrons are a significant source of heat for the sunlit polar cap ionosphere. The model includes a kinetic suprathermal electron transport solver, and it allows energy input from the upper boundary in three different ways: thermal conduction, soft precipitation, and potentials that reflect photoelectrons. The simulations confirm that reflection potentials of several tens of eV are required to prevent cold electron inflow and demonstrate that the flux tube integrated change in electron heating rate (FTICEHR) associated with reflected photoelectrons can reach 10 9 eV cm −2 s −1 . Soft precipitation can produce FTICEHR of comparable magnitudes, but this extra heating is divided among more electrons as a result of electron impact ionization. Simulations with no reflected photoelectrons and with downward field-aligned currents (FAC) primarily carried by the escaping photoelectrons have electron temperatures which are ∼250-500 K lower than the RISR-N measurements in the 300-600 km region; however, simulations with reflected photoelectrons, zero FAC, and no other form of heat flux through the upper boundary can satisfactorily reproduce the RISR-N data.

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“…Therefore, electron‐ion‐neutral interactions are a key process in controlling the dynamics and energetics of the upper atmosphere. Because the heating rate by photoelectrons increases with increasing ambient plasma density [ Hoegy , ] and the cooling rate through Coulomb collision is proportional to the square of plasma density [ Schunk and Nagy , ], electron temperature (Te) is negatively correlated with electron density (Ne) [e.g., Brace and Theis , ; Bilitza and Hoegy , ], which has been confirmed by many researchers. However, Te and Ne data measured by the HINOTORI satellite reveal that Te is negatively correlated with Ne in the low Ne range (<10 6 cm −3 ) but that Te is positively correlated with Ne in the high Ne range (>10 6 cm −3 ) [ Kakinami et al , , ].…”

Section: Introductionmentioning

confidence: 99%

Correlations between ion density and temperature in the topside ionosphere measured by ROCSAT‐1

et al. 2014

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From the ROCSAT-1 satellite plasma data at an altitude of 600 km, the correlation between ion temperature (Ti) and density (Ni) was investigated. The data were obtained in a magnetic dip latitude (MLAT) of less than ±40°in 2000-2004. Positive and negative correlations between Ni and Ti were observed around the magnetic dip equator, while weak positive correlations were observed in |MLAT| > 25°during daytime (10:00-16:00 local time). These variations were found in all longitudes, seasons, solar flux (F 10.7 ) levels, and magnetic disturbance levels, although the minimum value of Ti clearly increased with increasing solar flux levels. The results suggest that the solar flux dependence of Ti arises from the solar flux dependence on neutral temperature (Tn). Since Ti is determined by heating through Coulomb collision with electrons and cooling through elastic collision with neutral species, the ratio of ion density to neutral density is an important factor. The ratio reaches its maximum value around the magnetic dip equator and decreases with increasing MLAT. The correlation between Ni and Ti in the topside ionosphere can be explained by electron temperature (Te) and Tn as well as the ratio because Ti follows Te variation when the ratio is high, while it follows Tn when the ratio is low.

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Thermal electron heating rate: A derivation

Cited by 18 publications

References 22 publications

SAMI2‐PE: A model of the ionosphere including multistream interhemispheric photoelectron transport

SAMI2‐PE: A model of the ionosphere including multistream interhemispheric photoelectron transport

Heating of the sunlit polar cap ionosphere by reflected photoelectrons

Correlations between ion density and temperature in the topside ionosphere measured by ROCSAT‐1

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