Physics and Chemistry of the Earth, Part C: Solar, Terrestrial & Planetary Science最新文献

{"title":"Estimate of auroral electron spectra, the power of ground-based multi-station optical measurements","authors":"B. Gustavsson,&nbsp;A. Steen,&nbsp;T. Sergienko,&nbsp;B.U.E. Brändström","doi":"10.1016/S1464-1917(00)00106-9","DOIUrl":"10.1016/S1464-1917(00)00106-9","url":null,"abstract":"<div><p>Ground-based multi-station optical imaging has a great inherent scientific potential for investigations of the magnetosphere-ionosphere-thermosphere interactions by using inversions of the ionospheric optical signal, the aurora.</p><p>Two methods for estimating characteristics of primary auroral electron spectra are compared and used to describe an auroral event. One method uses the spectral information in the images and the other method is based on the inversion of the <em>N</em>₂⁺1<em>NG</em> 4287 Å altitude distribution. With the second method ALIS can currently give estimates of the primary electron distribution with medium time resolution (10 s).</p><p>The auroral event, a passage of an eastward moving fold in a pre-existing auroral arc, is analysed and characteristics of the precipitating electrons show regions with different fluxes, e.g. a soft region that has previously been found inside the fold appears to belong to a wider region of soft precipitation that emerges as the arc activates.</p></div>","PeriodicalId":101026,"journal":{"name":"Physics and Chemistry of the Earth, Part C: Solar, Terrestrial & Planetary Science","volume":"26 1","pages":"Pages 189-194"},"PeriodicalIF":0.0,"publicationDate":"2001-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S1464-1917(00)00106-9","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89977180","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The normal state of the F2 ionospheric layer at high latitudes","authors":"A. Belehaki ,&nbsp;G. Moraitis ,&nbsp;I. Tsagouri","doi":"10.1016/S1464-1917(01)00004-6","DOIUrl":"10.1016/S1464-1917(01)00004-6","url":null,"abstract":"<div><p>The use of monthly median values to determine the normal level of the undisturbed F2 layer, leads often to inconsistent results regarding the type of ionospheric disturbance and quietness as well. Recently Belehaki (2000) proposed an hourly local ionospheric index <em>f_nF2</em> to define the normal level of the F2 layer at middle latitudes. In this paper we apply the <em>f_nF2</em> index to observations from a high latitude station, where geomagnetic activity strongly influence the temporal and spatial behaviour of the ionospheric layers, for investigating and testing the usefulness of the <em>f_nF2</em> index on a planetary scale. From the analysis that follows, it was revealed that during intervals of low magnetospheric activity, <em>f_nF2</em> index shows a very good fit to the observed <em>f_oF2</em> parameter, comparing to the monthly median <em>f_oF2</em> behaviour. On the other hand, enhanced magnetospheric activity does not affect the <em>f_nF2</em> index, which daily variation is a function of the sunspot number itself. In summary, the <em>f_nF2</em> index can be used as a measure of the undisturbed F2 layer at middle and high latitudes as well, caution though is needed in the definition of the quiet magnetospheric intervals, which for the needs of this work it was approached as a function of the <em>aa</em>-index for middle latitudes, whereas the <em>AE</em>-index was used for auroral latitudes.</p></div>","PeriodicalId":101026,"journal":{"name":"Physics and Chemistry of the Earth, Part C: Solar, Terrestrial & Planetary Science","volume":"26 5","pages":"Pages 309-313"},"PeriodicalIF":0.0,"publicationDate":"2001-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S1464-1917(01)00004-6","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90083491","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A statistical method to predict debris flow deposited volumes on a debris fan","authors":"L. Franzi,&nbsp;G. Bianco","doi":"10.1016/S1464-1917(01)00067-8","DOIUrl":"10.1016/S1464-1917(01)00067-8","url":null,"abstract":"<div><p>The present paper aims to give a useful methodology to predict the debris volume <em>G_s</em> associated to a debris flow and deposited on the basin's terminal fan in the alpine region. Predicting the occurrence and the magnitude of a debris flow is often a very difficult task, as it is necessary to consider the variability of the geological, hydraulic and pluviometric factors connected to the beginning, propagation and deposition of a debris flow. These factors are not easily quantifiable, as well as their influence on the debris volumes deposited on the debris fan. Even if some useful mathematical (and deterministic) relations have been proposed by some authors to predict the likely debris volumes, they do not seem to take into account the high variability of the influencing factors. For these reasons a statistical investigation of the relationship between <em>Gs</em> and the basin area <em>A</em> has been undertaken. By means of well known statistical methodologies and by using a sample of about two hundred data (referred to the alpine region), a new criterion is proposed, in the present paper, for the prediction of a probable <em>Gs</em> value. For a given basin, this value is obtained on the basis of a statistical risk degree arbitrarily chosen. A probabilistic methodology is also proposed, which, when results of an accurate survey are not available for a particular basin, may provide a rational basis for a first hazard zonation and the design of mitigative measures.</p></div>","PeriodicalId":101026,"journal":{"name":"Physics and Chemistry of the Earth, Part C: Solar, Terrestrial & Planetary Science","volume":"26 9","pages":"Pages 683-688"},"PeriodicalIF":0.0,"publicationDate":"2001-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S1464-1917(01)00067-8","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80318620","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The time-weighted magnetic indices ap(τ), PC(τ), AE(τ) and their correlation to the southern high latitude ionosphere","authors":"L. Perrone ,&nbsp;G. De Franceschi ,&nbsp;Gulyaeva","doi":"10.1016/S1464-1917(01)00008-3","DOIUrl":"10.1016/S1464-1917(01)00008-3","url":null,"abstract":"<div><p>In this investigation different data transformations of the ionospheric characteristic foF2 from high latitude stations in the Southern Hemisphere are considered and correlated with time weighted accumulation of the geomagnetic indices ap, AE and PC. The analysis, performed during periods of severe magnetic activity, shows a decrease in foF2 as a consequence of geomagnetic perturbations and a characteristic response recovery time <em>t</em> ranged between 15–20 hours. The best correlation coefficients are obtained by comparing the time weighted accumulation of the auroral index AE and a data transformation based on the ratio NmF2(t)/NmF2_M where NmF2(t) is the hourly maximum electron density at the F2 peak layer and NmF2_M is its monthly median value.</p></div>","PeriodicalId":101026,"journal":{"name":"Physics and Chemistry of the Earth, Part C: Solar, Terrestrial & Planetary Science","volume":"26 5","pages":"Pages 331-334"},"PeriodicalIF":0.0,"publicationDate":"2001-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S1464-1917(01)00008-3","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76439392","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The physics in the auroral dynamo regions and auroral particle acceleration","authors":"Y. Song,&nbsp;R.L. Lysak","doi":"10.1016/S1464-1917(00)00087-8","DOIUrl":"10.1016/S1464-1917(00)00087-8","url":null,"abstract":"<div><p>Auroral particle acceleration requires an energy flux flowing into the acceleration region and the subsequent development of parallel electric fields. Auroral arcs are often very dynamic, and even in cases when a quasi-steady arc is formed, the question arises of how the system evolved to this quasi-steady state. Existing theories of auroral current generation and the formation of parallel electric fields mostly consider such a steady situation, limiting their ability to describe the dynamics of the system. Since the energy necessary to power auroral particle acceleration is related to the auroral current system, the generation of field-aligned currents (FAC) and auroral particle acceleration are closely coupled. Thus, in order to understand the dynamics of auroral particle acceleration, the physics in the auroral dynamo region must also be considered. Construction of such a dynamical theory of the auroral current system requires that the time-dependent generation of field-aligned currents (∂<em>J</em>_|/∂<em>t</em>) and the dynamics of the generation of parallel electric fields (∂<em>E</em>_|/∂<em>t</em>) and parallel potential drops must be the primary considerations.</p><p>The time-dependent generation of FAC filaments can occur as a result of the interaction of the MHD fast mode wave packets and a current sheet, either at the magnetopause or in the plasma sheet. In this process, a shear Alfvén wave can be generated in a discrete form as shear Alfvén wave packets. Although a single shear Alfvén wave packet can propagate without distortion or nonlinear interaction, the interaction of incident and reflected shear mode wave packets in the auroral acceleration region can release the kinetic and/or magnetic energy carried by the wave packets. Either solitary waves accompanied by a charge condensation (charge hole) or a net parallel potential drop may be formed, depending on the polarizations of the interacting wave packets. In order to produce FAC filaments and parallel electric fields by the wave packet interaction, a localized breakdown of the frozen-in condition is necessary. The electron inertial term is a natural candidate to break the frozen-in condition locally.</p></div>","PeriodicalId":101026,"journal":{"name":"Physics and Chemistry of the Earth, Part C: Solar, Terrestrial & Planetary Science","volume":"26 1","pages":"Pages 33-42"},"PeriodicalIF":0.0,"publicationDate":"2001-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S1464-1917(00)00087-8","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75559491","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Sulphate particles from subsonic aviation: impact on upper tropospheric and lower stratospheric ozone","authors":"G. Pitari ,&nbsp;E. Mancini ,&nbsp;A. Bregman ,&nbsp;H.L. Rogers ,&nbsp;J.K. Sundet ,&nbsp;V. Grewe ,&nbsp;O. Dessens","doi":"10.1016/S1464-1917(01)00048-4","DOIUrl":"https://doi.org/10.1016/S1464-1917(01)00048-4","url":null,"abstract":"","PeriodicalId":101026,"journal":{"name":"Physics and Chemistry of the Earth, Part C: Solar, Terrestrial & Planetary Science","volume":"26 8","pages":"563-569"},"PeriodicalIF":0.0,"publicationDate":"2001-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S1464-1917(01)00048-4","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72217827","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Auroral particle acceleration by waves","authors":"R. Bingham ,&nbsp;R.A. Cairns ,&nbsp;R.O. Dendy ,&nbsp;V.D. Shapiro ,&nbsp;P.K. Shukla ,&nbsp;L. Stenflo","doi":"10.1016/S1464-1917(00)00099-4","DOIUrl":"10.1016/S1464-1917(00)00099-4","url":null,"abstract":"<div><p>The role of waves in accelerating both electrons and ions in the auroral zone is discussed. Various wave generation mechanisms and acceleration processes including acceleration within cavitons and nonlinear potential structures are analysed. The wave modes which we consider include waves such as kinetic Alfvén waves, and lower-hybrid waves. In some cases wave amplitudes are found to be large enough for strong turbulence effect to play a significant role in the particle dynamics. These effects manifest themselves in the formation of caviton structures and large scale density striations creating local acceleration regions. A theoretical description of the different nonlinear processes responsible for plasma modification and acceleration will be presented.</p></div>","PeriodicalId":101026,"journal":{"name":"Physics and Chemistry of the Earth, Part C: Solar, Terrestrial & Planetary Science","volume":"26 1","pages":"Pages 133-144"},"PeriodicalIF":0.0,"publicationDate":"2001-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S1464-1917(00)00099-4","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76243338","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A new model for the Schumann-Runge bands of O2","authors":"B.R. Lewis ,&nbsp;S.T. Gibson ,&nbsp;F.T. Hawes ,&nbsp;L.W. Torop","doi":"10.1016/S1464-1917(01)00040-X","DOIUrl":"10.1016/S1464-1917(01)00040-X","url":null,"abstract":"<div><p>A new quantum-mechanical model is presented of photoabsorption and photodissociation in the discrete and continuous Schumann-Runge regions of the molecular oxygen spectrum, based on the coupled-channel Schrödinger-equations method. The ability of the model to predict accurately temperature-dependent photoabsorption cross sections and photodissociation branching ratios is demonstrated, suggesting applications in the areas of atmospheric vacuum-ultraviolet opacity and photochemistry.</p></div>","PeriodicalId":101026,"journal":{"name":"Physics and Chemistry of the Earth, Part C: Solar, Terrestrial & Planetary Science","volume":"26 7","pages":"Pages 519-526"},"PeriodicalIF":0.0,"publicationDate":"2001-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S1464-1917(01)00040-X","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"109921896","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Model update for mesospheric/thermospheric nitric oxide","authors":"P.K. Swaminathan ,&nbsp;D.F. Strobel ,&nbsp;L. Acton ,&nbsp;L.J. Paxton","doi":"10.1016/S1464-1917(01)00042-3","DOIUrl":"10.1016/S1464-1917(01)00042-3","url":null,"abstract":"<div><p>In reviewing the large deficit in model predictions of nitric oxide (NO) abundance near the mesosphere/lower thermosphere [NO] peak region, this paper shows that the deficit is now largely reduced using an updated model. Prior model/data comparison study (Swaminathan, 1998) which included comprehensive chemistry, contemporaneously measured solar soft x ray flux, and time-dependence of the suprathermal N(⁴S) atom source, pointed to a large net deficit based on current NO chemistry. Although the suprathermal source has been invoked for many decades, its importance has been recently disestablished (Balakrishnan 1998). The present update to the model has no suprathermal N(⁴S) source, a recently measured higher NO⁺ recombination branching ratio and extended empirical solar x ray wavelength coverage based on combined YOHKOH and SNOE solar x ray flux data; and it is found that the large deficit is no longer present. The model predicts [NO] peak density within 30% of the data after accounting for the ever-present auroral transport contribution derived by Barth (1999) from recent SNOE measurements. This result dramatically impacts the thermospheric nitric oxide abundance problem that has existed for many decades. Further search for minor NO chemical sources is only appropriate while also quantifying the role of multidimensional atmospheric dynamics in detailed model/data comparisons.</p></div>","PeriodicalId":101026,"journal":{"name":"Physics and Chemistry of the Earth, Part C: Solar, Terrestrial & Planetary Science","volume":"26 7","pages":"Pages 533-537"},"PeriodicalIF":0.0,"publicationDate":"2001-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S1464-1917(01)00042-3","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83431648","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Almost monoenergetic ions: new support for Alfvén ideas on the role of electric currents in space plasmas?","authors":"V.N. Lutsenko","doi":"10.1016/S1464-1917(01)00057-5","DOIUrl":"https://doi.org/10.1016/S1464-1917(01)00057-5","url":null,"abstract":"<div><p>A new kind of energetic particle spectra consisting of 1–3 narrow lines was discovered in the DOK-2 experiments on board of the Interball-1 and 2 spacecrafts during a period from August 1995 to August 1999 in the region upstream of the Earth's bow shock, in the magnetosheath, and near the border of the magnetotail plasma sheet. The relative width at half maximum of these lines was of 15–30%. Ion energy values varied for different events from 30 to 600 keV but were almost unchanged during each event. In two-peak spectra the energy values ratio was 1:2, and in three peak spectra the ratios were 1:2(5–6). Such line spectra cannot be explained by current models of particle acceleration or escape from the magnetosphere. We propose a hypothesis explaining the origin and the main features of these ions by solar wind ions acceleration in a burst of strong electrostatic field (50–100 mV/m) in a small region (1000–5000 km). This burst can be a result of a disruption of a current filament of the magnetopause or the magnetotail current system. By such a disruption the whole potential difference over the magnetosphere due to convective electric field develops over a small region accelerating plasma ions to energies ∼100 keV. If this mechanism is really working it may give a new support to Alfvén ideas on the dualism and the role of electric currents in space plasmas.</p></div>","PeriodicalId":101026,"journal":{"name":"Physics and Chemistry of the Earth, Part C: Solar, Terrestrial & Planetary Science","volume":"26 8","pages":"Pages 615-619"},"PeriodicalIF":0.0,"publicationDate":"2001-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S1464-1917(01)00057-5","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"137126542","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}