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Peter M. Banks

Bio: Peter M. Banks is an academic researcher from University of Michigan. The author has contributed to research in topics: Ionosphere & Electron. The author has an hindex of 40, co-authored 86 publications receiving 6321 citations. Previous affiliations of Peter M. Banks include University of California, Berkeley & Belgian Institute for Space Aeronomy.


Papers
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Journal ArticleDOI
TL;DR: The Ultraviolet Imager for the Global Geospace Sciences portion of the International Solar-Terrestrial Physics (IGSSP) program as discussed by the authors has been used to image the auroral oval and polar cap.
Abstract: The aurorae are the result of collisions with the atmosphere of energetic particles that have their origin in the solar wind, and reach the atmosphere after having undergone varying degrees of acceleration and redistribution within the Earth's magnetosphere. The global scale phenomenon represented by the aurorae therefore contains considerable information concerning the solar-terrestrial connection. For example, by correctly measuring specific auroral emissions, and with the aid of comprehensive models of the region, we can infer the total energy flux entering the atmosphere and the average energy of the particles causing these emissions. Furthermore, from these auroral emissions we can determine the ionospheric conductances that are part of the closing of the magnetospheric currents through the ionosphere, and from these we can in turn obtain the electric potentials and convective patterns that are an essential element to our understanding of the global magnetosphere-ionosphere-thermosphere-mesosphere. Simultaneously acquired images of the auroral oval and polar cap not only yield the temporal and spatial morphology from which we can infer activity indices, but in conjunction with simultaneous measurements made on spacecraft at other locations within the magnetosphere, allow us to map the various parts of the oval back to their source regions in the magnetosphere. This paper describes the Ultraviolet Imager for the Global Geospace Sciences portion of the International Solar-Terrestrial Physics program. The instrument operates in the far ultraviolet (FUV) and is capable of imaging the auroral oval regardless of whether it is sunlit or in darkness. The instrument has an 8° circular field of view and is located on a despun platform which permits simultaneous imaging of the entire oval for at least 9 hours of every 18 hour orbit. The three mirror, unobscured aperture, optical system (f/2.9) provides excellent imaging over this full field of view, yielding a per pixel angular resolution of 0.6 milliradians. Its FUV filters have been designed to allow accurate spectral separation of the features of interest, thus allowing quantitative interpretation of the images to provide the parameters mentioned above. The system has been designed to provide ten orders of magnitude blocking against longer wavelength (primarily visible) scattered sunlight, thus allowing the first imaging of key, spectrally resolved, FUV diagnostic features in the fully sunlit midday aurorae. The intensified-CCD detector has a nominal frame rate of 37 s, and the fast optical system has a noise equivalent signal within one frame of ∼ 10R. The instantaneous dynamic range is >1000 and can be positioned within an overall gain range of 104, allowing measurement of both the very weak polar cap emissions and the very bright aurora. The optical surfaces have been designed to be sufficiently smooth to permit this dynamic range to be utilized without the scattering of light from bright features into the weaker features. Finally, the data product can only be as good as the degree to which the instrument performance is characterized and calibrated. In the VUV, calibration of an an imager intended for quantitative studies is a task requiring some pioneering methods, but it is now possible to calibrate such an instrument over its focal plane to an accuracy of ±10%. In summary, very recent advances in optical, filter and detector technology have been exploited to produce an auroral imager to meet the ISTP objectives.

421 citations

Journal ArticleDOI
TL;DR: Polar wind, describing upward plasma expansion of topside polar ionosphere and acceleration of positive H and He ions as discussed by the authors, describes upward plasmas expansion of top-side polar ionosphere.
Abstract: Polar wind, describing upward plasma expansion of topside polar ionosphere and acceleration of positive H and He ions

377 citations

Journal ArticleDOI
TL;DR: In this article, fluxes and energy spectra in ionosphere for predawn and sunlit atmospheres, taking into account elastic and inelastic collisions were analyzed. But the authors did not consider the effect of temperature variation.
Abstract: Photoelectron fluxes and energy spectra in ionosphere for predawn and sunlit atmospheres, taking into account elastic and inelastic collisions

360 citations

Journal ArticleDOI
TL;DR: In this paper, the coupled continuity, momentum, and energy equations for NO(+, O(+), and O2(+) ions were obtained for conditions appropriate to the daytime high-latitude E and F regions.
Abstract: We have obtained solutions of the coupled continuity, momentum, and energy equations for NO(+), O(+), and O2(+) ions for conditions appropriate to the daytime high-latitude E and F regions. Owing to the rapid increase of the reaction O(+) + N2 yielding NO(+) + N with ion energy, high-latitude electric fields and consequent perpendicular-E x B drifts deplete O(+) in favor of NO(+). For electric field strengths less than about 10 mV/m the depletion of O(+) is small, and the altitude profiles of ion density are similar to those found at mid-latitudes. However, for moderate electric field strengths (50 mV/m), NO(+) is substantially increased in relation to O(+) and becomes an important ion throughout the F region. For large electric fields (200 mV/m), NO(+) completely dominates the ion composition to at least 600 km, decreasing at high altitudes with a diffusive equilibrium scale height. Since the overall F region electron density decreases markedly with increasing electric field strength, it appears that high-latitude, daytime electron density troughs are directly related to the presence of ionospheric electric fields.

343 citations

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TL;DR: In this paper, a new computational model has been created to describe the interaction of auroral electrons with the atmosphere, which is used to compute energy spectrums, ionization rates, backscatter ratios, and optical emissions associated with different incident electron spectrums.
Abstract: A new computational model has been created to describe the interaction of auroral electrons with the atmosphere. For electrons of energy greater than 500 eV, continuous energy losses and small angle deflections are combined in a Fokker-Planck diffusion equation that computes energy spectrums over all pitch angles throughout the atmosphere. These fluxes are then used to determine the rates of secondary electron and degraded (E < 500 eV) primary electron production at all heights. This information is used to compute upward and downward hemispherical fluxes in the energy range 0–500 eV, taking into account discrete energy losses, large angle scattering, and particle transport along magnetic field lines. The model has been used to compute energy spectrums, ionization rates, backscatter ratios, and optical emissions associated with different incident electron spectrums. For monoenergetic electrons of energy 2 keV and above the results obtained agree well with the work of Rees (1969) and Rees and Maeda (1973). At lower energies the effects of transport and elastic collisions become progressively more important, and the present results differ significantly both from the Rees and Maeda results and from those obtained from the ideas of energy degradation. Finally, spectrums typical of the nighttime auroral oval and daytime polar cusp are used to obtain the altitude dependent fluxes, ionization rates, and optical emissions.

315 citations


Cited by
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Journal ArticleDOI
TL;DR: In this article, the authors examined the theoretical consequences to be expected during the extended relaxation phase which must follow such events, characterized by a gradual reconnection of the outward-distended field lines.
Abstract: Many classes of transient solar phenomena, such as flares, flare sprays, and eruptive prominences, cause major disruptions in the magnetic geometry of the overlying corona. Typically, the results from Skylab indicate that pre-existing closed magnetic loops in the corona are torn open by the force of the disruption. We examine here some of the theoretical consequences to be expected during the extended relaxation phase which must follow such events. This phase is characterized by a gradual reconnection of the outward-distended field lines. In particular, the enhanced coronal expansion which occurs on open field lines just before they reconnect appears adequate to supply the large downward mass fluxes observed in Ha loop prominence systems that form during the post-transient relaxation. In addition, this enhanced flow may produce nonrecurrent high speed streams in the solar wind after such events. Calculations of the relaxation phase for representative field geometries and the resulting flow configurations are described.

1,467 citations

Journal ArticleDOI
TL;DR: In this paper, large-scale revisions of the OGO 6 dawn-dusk measurement models are made, showing that the deformations of the two-cell patterns lead to sunward convection in dayside polar regions, while maintaining the integrity of the night-side convection pattern.
Abstract: The present analysis of electric field measurements from the Dynamics Explorer 2 satellite, which extends previous empirical models, emcompasses much data from polar crossings entering and exiting the high latitudes in all magnetic local time zones. The goal is to represent the typical distributions of convective electric fields with a minimum number of characteristic patterns. Significant large-scale revisions of the OGO 6 dawn-dusk measurement models are made. The deformations of the two-cell patterns lead to sunward convection in dayside polar regions, while maintaining the integrity of the nightside convection pattern.

1,060 citations

Journal ArticleDOI
TL;DR: In this article, a numerical simulation study of the thermospheric winds produced by auroral heating during magnetic storms, and of their global dynamo effects, establishes the main features of the ionospheric disturbance dynamo.
Abstract: A numerical simulation study of the thermospheric winds produced by auroral heating during magnetic storms, and of their global dynamo effects, establishes the main features of the ionospheric disturbance dynamo. Driven by auroral heating, a Hadley cell is created with equatorward winds blowing above about 120 km at mid-latitudes. The transport of angular momentum by these winds produces a subrotation of the mid-latitude thermosphere or westward motion with respect to the earth. The westward winds in turn drive equatorward Pedersen currents which accumulate charge toward the equator, resulting in the generation of a poleward electric field, a westward E × B drift, and an eastward current. When realistic local time conductivity variations are simulated, the eastward mid-latitude current is found to close partly via lower latitudes, resulting in an ‘anti-Sq’ type of current vortex. Both electric field and current at low latitudes thus vary in opposition to their normal quiet-day behavior. This total pattern of disturbance winds, electric fields, and currents is superimposed upon the background quiet-day pattern. When the neutral winds are artificially confined on the nightside, the basic pattern of predominantly westward E × B plasma drifts still prevails on the nightside but no longer extends into the dayside. Considerable observational evidence exists, suggesting that the ionospheric disturbance dynamo has an appreciable influence on storm-time ionospheric electric fields at middle and low latitudes.

1,049 citations

Journal ArticleDOI
TL;DR: Topside ionospheric instabilities of electrostatic ion acoustic and ion cyclotron waves to field aligned currents in single and multiion plasmas are discussed in this paper.
Abstract: Topside ionospheric instabilities of electrostatic ion acoustic and ion cyclotron waves to field aligned currents in single and multiion plasmas

872 citations

Journal ArticleDOI
TL;DR: In this article, it was shown that epsilon is the primary factor controlling the time development of magnetospheric substorms and storms and that the power generated by the dynamo can be identified as ϵ through the use of a dimensional analysis, indicating that the magnetosphere is closer to a directly driven system than to an unloading system which stores the generated energy before converting it to substorm and storm energies.
Abstract: A description is given of the path leading to the first approximation expression for the solar wind-magnetosphere energy coupling function (epsilon), which correlates well with the total energy consumption rate (U sub T) of the magnetosphere. It is shown that epsilon is the primary factor controlling the time development of magnetospheric substorms and storms. The finding of this particular expression epsilon indicates how the solar wind couples its energy to the magnetosphere; the solar wind and the magnetosphere make up a dynamo. In fact, the power generated by the dynamo can be identified as epsilon through the use of a dimensional analysis. In addition, the finding of epsilon suggests that the magnetosphere is closer to a directly driven system than to an unloading system which stores the generated energy before converting it to substorm and storm energies. The finding of epsilon and its implications is considered to have significantly advanced and improved the understanding of magnetospheric processes.

840 citations