Ionospheres

Schunk, R. W.; Nagy, Andrew F.

doi:10.1017/cbo9780511635342

Cited by 859 publications

(562 citation statements)

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“…Closed form expressions for all of the collisional terms needed in the five-moment equations which are valid for arbitrarily large temperature and velocity differences between species have been derived, but unfortunately, the same is not true for the eight-moment equations [Schunk and Nagy, 2009]. The Burgers linear collision terms are valid for small temperature and velocity differences, and the Burgers semilinear collision terms are valid for small velocity differences but arbitrary temperatures differences [Burgers, 1969;Schunk and Nagy, 2009].…”

Section: 1002/2013ja019378mentioning

confidence: 99%

“…The Burgers linear collision terms are valid for small temperature and velocity differences, and the Burgers semilinear collision terms are valid for small velocity differences but arbitrary temperatures differences [Burgers, 1969;Schunk and Nagy, 2009]. In the polar wind the velocity differences between the light and heavy ions can exceed the ion thermal speeds, meaning the Burgers linear collision terms are not valid.…”

Section: 1002/2013ja019378mentioning

confidence: 99%

“…In the above equations k B is Boltzmann's constant, the are momentum transfer collision frequencies, and the reduced masses and temperatures are defined as [Schunk and Nagy, 2009] …”

Section: 1002/2013ja019378mentioning

confidence: 99%

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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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Section: 1002/2013ja019378mentioning

confidence: 99%

Section: 1002/2013ja019378mentioning

confidence: 99%

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Heating of the sunlit polar cap ionosphere by reflected photoelectrons

2014

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“…A complete description of all the reactions and associated energetics can be found in standard textbooks such as Schunk & Nagy (2009). We divide the deposited energy obtained from simulations by the ion pair generation energy to calculate ion pairs for each scenario.…”

Section: Resultsmentioning

confidence: 99%

“…A fraction of the energy is lost in the form of heat, airglow and transport processes such as thermal conduction and molecular diffusion. The electrons take away a large fraction of the kinetic energy since positive ions are heavy and possess less recoil energy (Schunk & Nagy 2009). The other mechanisms include ion sputtering produced by ions impacting the upper atmosphere, plasma energization and solar wind forcing and ion pickup by solar wind electric field.…”

Section: Introductionmentioning

confidence: 99%

Did high-energy astrophysical sources contribute to Martian atmospheric loss?

Atri¹

2016

Monthly Notices of the Royal Astronomical Society: Letters

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Mars is believed to have had a substantial atmosphere in the past. Atmospheric loss led to depressurization and cooling, and is thought to be the primary driving force responsible for the loss of liquid water from its surface. Recently, MAVEN observations have provided new insight into the physics of atmospheric loss induced by ICMEs and solar wind interacting with the Martian atmosphere. In addition to solar radiation, it is likely that its atmosphere has been exposed to radiation bursts from high-energy astrophysical sources which become highly probable on timescales of ∼Gy and beyond. These sources are capable of significantly enhancing the rates of photoionization and charged particle-induced ionization in the upper atmosphere. We use Monte Carlo simulations to model the interaction of charged particles and photons from astrophysical sources in the upper Martian atmosphere and discuss its implications on atmospheric loss. Our calculations suggest that the passage of the solar system though dense interstellar clouds is the most significant contributor to atmospheric loss among the sources considered here.

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Elevated electron temperatures around twin sporadic E layers at low latitude: Observations and the case for a plausible link to currents parallel to the geomagnetic field

2013

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[1] We present data from nighttime sounding rocket flights in the low latitude E region. The payloads carried a sweeping Langmuir probe, a plasma impedance probe, and electric field probes. A detailed examination of the plasma density, temperature, and electric field measurements show two strong sporadic E (E s ) layers with very high electron temperatures ( 1000 K) on each side of the upper layer. The lower layer was consistent with the presence of a strong zonal neutral wind shear. The upper layer was strongly influenced by the presence of a strongly negative vertical electric field, with zonal winds and their shears also contributing. A strong downward motion of the plasma from the combined action of the downward electric field and negative zonal wind advected the upper layer far below the region of maximum growth. We have attributed the more puzzling high electron temperatures to frictional heating from parallel currents and shown that the F region nighttime dynamo could easily generate the necessary parallel current densities (1 A m -2 ) near the electron density troughs. The electron temperature was also elevated in the E s layers themselves, implying parallel current densities of the order of 15 A m -2 around the E s peaks. Those parallel currents were attributed to strong Hall current divergences driven by the zonal electric field around the E s peaks.Citation: Barjatya, A., J.-P. St-Maurice, and C. M. Swenson (2013), Elevated electron temperatures around twin sporadic E layers at low latitude: Observations and the case for a plausible link to currents parallel to the geomagnetic field,

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Ionospheres

Cited by 859 publications

References 0 publications

Heating of the sunlit polar cap ionosphere by reflected photoelectrons

Heating of the sunlit polar cap ionosphere by reflected photoelectrons

Did high-energy astrophysical sources contribute to Martian atmospheric loss?

Elevated electron temperatures around twin sporadic E layers at low latitude: Observations and the case for a plausible link to currents parallel to the geomagnetic field

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