HEUVAC: A new high resolution solar EUV proxy model

Richards, P. G.; Woods, Thomas N.; Peterson, W. K.

doi:10.1016/j.asr.2005.06.031

Cited by 120 publications

(113 citation statements)

References 34 publications

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“…The chemical production and loss rates are computed using the reactions from the recent review of Richards [2011] plus the extra reactions listed in Appendix A. The photoproduction rates are computed from the high-resolution empirical solar EUV spectrum HEUVAC [Richards et al, 2006] as described by Varney [2012]. The computation of the impact ionization rates from the suprathermal electron fluxes is described in detail by Varney [2012].…”

Section: 1002/2013ja019378mentioning

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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Section: 1002/2013ja019378mentioning

confidence: 99%

Heating of the sunlit polar cap ionosphere by reflected photoelectrons

2014

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“…EUVAC also adds physical constraints on the coronal flux. Its latest version, named HEUVAC (Richards et al 2006), extends the EUV model below 5 nm and includes data from the SEE instrument onboard TIMED (Woods et al 2005). All these models are reviewed in Lilensten et al (2008).…”

Section: The Euv/xuv Sourcementioning

confidence: 99%

Ionization processes in the atmosphere of Titan

Gronoff¹,

Lilensten²,

Desorgher

et al. 2009

A&A

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Context. The Cassini probe regularly passes in the vicinity of Titan, revealing new insights into particle precipitation thanks to the electron and proton spectrometer. Moreover, the Huygens probe has revealed an ionized layer at 65 km induced by cosmic rays. The impact of these different particles on the chemistry of Titan is probably very strong. Aims. In this article, we compute the whole ionization in the atmosphere of Titan: from the cosmic rays near the ground to the EUV in the upper atmosphere. The meteoritic layer is not taken into account. Methods. We used the transTitan model to compute the electron and EUV impact, and the planetocosmics code to compute the influence of protons and oxygen ions. We coupled the two models to study the influence of the secondary electrons obtained by planetocosmics through the transTitan code. The resulting model improves the accuracy of the calculation through the transport of electrons in the atmosphere. Results. The whole ionization is computed and studied in details. During the day, the cosmic ray ionization peak is as strong as the UV-EUV one. Electrons and protons are very important depending the precipitation conditions. Protons can create a layer at 500 km, while electrons tend to ionize near 800 km. The oxygen ion impact is near 900 km. The results shows few differences to precedent models for the nightside T5 fly-by of Cassini, and can highlight the sources of the different ion layers detected by radio measurements. Conclusions. The new model successfully computes the ion production in the atmosphere of Titan. For the first time, a full electron and ion profile has been computed from 0 to 1600 km, which compares qualitatively with measurements. This result can be used by chemical models.

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“…EUVAC also adds physical constraints on the coronal flux. Its latest version, named HEUVAC (high-resolution solar EUV irradiance model for aeronomic calculations) (Richards et al 2006), extends the EUV model below 5 nm and includes data from the SEE (Solar EUV Experiment) instrument on board TIMED (Thermosphere Ionosphere Mesosphere Energetics and Dynamics) (Woods et al 2005).…”

Section: Solar Xuv-euv Models For Space Weather Applicationsmentioning

confidence: 99%

Solar Weather Event Modelling and Prediction

et al. 2009

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Key drivers of solar weather and mid-term solar weather are reviewed by considering a selection of relevant physics-and statistics-based scientific models as well as a selection of related prediction models, in order to provide an updated operational scenario for space weather applications. The characteristics and outcomes of the considered scientific and prediction models indicate that they only partially cope with the complex nature of solar activity for the lack of a detailed knowledge of the underlying physics. This is indicated by the fact that, on one hand, scientific models based on chaos theory and non-linear dynamics reproduce better the observed features, and, on the other hand, that prediction models based on statistics and artificial neural networks perform better. To date, the solar weather prediction success at most time and spatial scales is far from being satisfactory, but the forthcoming ground-and space-based high-resolution observations can add fundamental tiles to the modelling and predicting frameworks as well as the application of advanced mathematical approaches in the analysis of diachronic solar observations, that are a must to provide comprehensive and homogeneous data sets.

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HEUVAC: A new high resolution solar EUV proxy model

Cited by 120 publications

References 34 publications

Heating of the sunlit polar cap ionosphere by reflected photoelectrons

Heating of the sunlit polar cap ionosphere by reflected photoelectrons

Ionization processes in the atmosphere of Titan

Solar Weather Event Modelling and Prediction

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