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[en] Complete text of publication follows. The equation of pitch angle diffusion is offered, which also allows to model change of pitch angle distribution from time. Two examples are presented. The first example is evolution of pitch angle distribution of protons during a typical moderate magnetic storm. The second example is evolution of pitch angle distribution of protons during the 2 - 7 May 1998 storm. The received results are compared among themselves and to results of other works.
[en] The ATS-6 data for a period of 1975-76 is used for the study of slab thickness during two moderate storms (Ksub(p)<=4-) around the crest of the anomaly, Ahmedabad and a very great (Ksub(p)<=7), a great (Ksub(p)<=4) and a moderate storm (Ksub(p)<=6+) outside the equatorial anomaly region, Delhi. While at Ahmedabad, on the average, the slab thickness is found to be above the frequency. Comparison of slab thickness with foF2 and the equatorial magnetic record (for Ahmedabad only) shows that the foF2 changes alone cannot be held responsible for the slab thickness variation and thus entry of the plasma flux from the plasmasphere cannot be ruled out. The pressure variation effect of storm-time heating on the slab thickness at Ahmedabad is that even for Ksub(p)=8, the thermal expansion and the contraction effects are unable to explain complete quantitative and qualitative features of the observations
[en] A theoretical study has been made of the process to refill geomagnetic force tubes with a thermal ionospheric plasma after a magnetic disturbance. As shown by analytical and numerical calculations, the characteristic time of filling and the maximum possible total electron content are proportional to the tube volume and equal to tau approximately 0.17L4 of a day and N infinity approximately 1012L4 cm-2, respectively. It is typical during a long period of magnetically quiet conditions that at L < 3 the electron content is closed to a limited value of N infinity approximately L4, whereas at L > 3 the electron content is proportional to the duration of the quiet period and does not depend on the value of L. Incomplete filling of the force tubes with a thermal plasma causes the ionospheric light ion through to be produced within the range of L-shells for which tau(L) >> t
[en] The relationship between disappearing solar fragments and geomagnetic disturbances was investigated. It is shown that long-delay storms are associated with filaments well removed from the disc centre, and particularly in the case of large filaments and prominences, the proportion of events that produce long-delay storms increases with angular distance from the centre
[en] Complete text of publication follows. The complex system of the Earth's magnetosphere corresponds to an open spatially extended nonequilibrium (input - output) dynamical system. The non-extensive Tsallis entropy has been recently introduced (Balasis et al., 2008) as an appropriate information measure to investigate dynamical complexity in the magnetosphere. The method has been employed for analyzing Dst time series and gave promising results, detecting the complexity dissimilarity among different physiological and pathological magnetospheric states (i.e., pre-storm activity and intense magnetic storms, respectively). This paper explores the applicability and effectiveness of a variety of computable entropy measures (e.g. Block entropy, Kolmogorov entropy, T complexity and Approximate entropy) to the investigation of dynamical complexity in the magnetosphere. We show that as the magnetic storm approaches there is clear evidence of significant lower complexity in the magnetosphere. The observed higher degree of organization of the system agrees with that inferred previously (Balasis et al., 2006), from an independent linear fractal spectral analysis based on wavelet transforms. This convergence between nonlinear and linear analyses provides a more reliable detection of the transition from the quiet-time to the storm-time magnetosphere, thus showing evidence that the occurrence of an intense magnetic storm is imminent. More precisely, we claim that our results suggest an important principle: significant complexity decrease and accession of persistency in Dst time series can be confirmed as the magnetic storm approaches, which can be used as diagnostic tools for the magnetospheric injury (global instability). Overall, Approximate entropy and Tsallis entropy yield superior results for detecting dynamical complexity changes in the magnetosphere in comparison to the other entropy measures presented herein. Ultimately, the analysis tools developed in the course of this study for the treatment of Dst index can provide convenience for space weather applications.
[en] Complete text of publication follows. One of the modern and popular uses of ground magnetometer data is to identify field line resonance frequencies through cross-phase or cross-amplitude analysis and infer the equatorial mass density in the magnetosphere. Most studies on this topic to date focus on the observations along a specific meridian, and, as the Earth rotates, the observations constantly advance in local time. This study presents the field line resonance analysis using data gathered by a number of magnetometer networks in North America, such as McMAC, Falcon, IGPP-LANL, THEMIS, CARISMA, AUTUMN, and Alaskan stations. The observations provide two-dimensional snapshots of the equatorial mass density over a range of L-values and local hours. Using the October 2007 magnetic storm as an example, we will show the spatiotemporal features of density structure observed by the combined two-dimensional magnetometer network and how they are compared with the results obtained by observations along a single meridian.
[en] First, we present and compare experimental data on magnetospheric cold plasma density and plasmapause position obtained, for two magnetically disturbed days (14 and 6 July 1977), by the three following techniques: - analysis of multi-component whistlers recorded at Kerguelen (L = 3.7) and General Belgrano (L approximately equal to 4.5), Antarctica; - in situ measurements from the relaxation sounded and the mutual impedance experiment on board GEOS-1; - broadband VLF spectra telemetered from the ISIS satellites to Kerguelen. In the vicinity of the plasmapause, the equarorial electron density profiles derived from whistlers and GEOS-1 data are similar. Outside the plasmasphere, the agreement between results is better when the hybrid model -rather than R-4 ones- is assumed in whistler analysis. Inside the plasmasphere, the radial decrease of the electron density above L = 4 follows roughly a L-4 law. Then, all the data are used to study the structure and the dynamical behavior of the dayside plasmasphere. On July 14, the response of the plasmapause to substorms is complex and occurs with some delay, increasing with the magnetic local time. We observe successively: a plasmapause deformation near 12 MLT, detached plasma elements in the early afternoom sector and a reduced size plasmaphere, with a pronounced duskside bulge, in the 12-19 MLT sector. On July 6, the plasmasphere structure and the cold plasma drifts in the equatorial plane are those of quiet magnetic periods as long as there is no energy injection into the ring current. As soon as the injection associated with the magnetic storm begins, the equatorial structure of the dayside plasmasphere becomes irregular. It appears, between approximately 3.5 and 4 Rsub(E), a trough-like depression which remains in the view of the ground-based station during more than six hours; the electron densities in the trough-like region are of the order of 300 cm-3, whereas they were between 500 and 550 cm-3 before the magnetic storm
[fr]On presente et compare des donnees experimentales sur la densite du plasma froid magnetospherique et sur la position de la plasmapause obtenues, au cours de deux journees magnetiquement perturbees (les 14 et 16 juillet 1977), a l'aide des trois techniques suivantes: - analyse de sifflements a composantes multiples enregistres a Kerguelen (L = 3.7) et General Belgrano (L approximativement = 4.5), en Antarctique; - mesures in-situ faites a bord de GEOS-1 au moyen du sondeur a relaxation et de l'experience d'impedance mutuelle; - spectres TBF en large bande realises a bord des satellites ISIS par telecommande depuis la station de Kerguelen. Au voisinage de la plasmapause, les profils de la densite electronique equatoriale deduits des donnees des sifflements et de GEOS-1 sont similaires. A l'exterieur de la plasmasphere, la condordance des resultats est meilleure lorsque le modele hybride, plutot que le modele R-4, est adopte pour analyser les sifflements. A l'interieur de la plasmasphere, la decroissance radiale de la densite electronique suit une loi en L-4 au-dela de L = 4. Toutes les donnees sont ensuite utilisees pour etudier la structure et le comportement dynamique de la region diurne de la plasmasphere. Le 14 juillet 1977, la reponse de la plasmapause aux sous-orages est complexe et a lieu avec un certain retard qui augmente avec le temps magnetique local. Le 6 juillet 1977, la structure de la plasmasphere et les derives du plasma froid dans le plan equatorial sont celles des periodes magnetiquement calmes tant qu'il ne se produit pas une injection d'energie dans le courant annulaire. Des le debut de l'injection associee a l'orage magnetique, la structure equatoriale de la plasmasphere du cote jour devient irreguliere. Il apparait, entre environ 3.5 et 4 Rsub(E), un creux d'ionisation; les densites electroniques y sont de l'ordre de 300 cm-3 alors qu'elles etaient comprises entre 500 et 550 cm-3, avant l'orage magnetique
[en] Total electron content (Nsub(t)) of the ionosphere obtained from 137-MHz transmissions of ATS-1 at Honolulu, Hawai and maximum ionization (Nsub(m)) of F layer derived from ionosonde measurements at Maui, Hawai have been combined to study the nature of ionospheric response at low midlatitudes (20 deg N geomagnetic) to 27 SC type geomagnetic storms during the solar maximum phase of 1967-1968. The local time and stormtime variations of Nsub(t)Nsub(m) and their ratio tau, known as the slab thickness of the ionosphere, are examined on a seasonal basis. It is shown that during summer and equinoxes, Nsub(t) and Nsub(m) show an initial positive phase followed by a long enduring negative phase. In winter, these two parameters indicate only a marked positive phase. In spite of the seasonally varying depletion or enhancement shown by Nsub(t) and Nsub(m), the slab thickness parameter tau shows an increase irrespective of the season; the observed increase is, however, small compared to the variations in the other two parameters. This indicates that the shape factor of ionization distribution tends to be preserved during the storms. The observed seasonal variations of Nsub(b)Nsub(m) and tau at this low midlatitude station are interpreted on the basis of current models of stormtime meridional wind and changes in neutral air composition
[en] The latitudinal variation of the effect of the great storm of 17 Dec. 71 is investigated by choosing stations of varying latitudes but of approximately the same longitude. In addition, three stations, one each in the American, African and Indian zone, are chosen to find the longitudinal changes produced during this storm. It is seen that the storm is mainly a negative one in the southern hemisphere of this longitude sector. The noon biteout is enhanced on the major storm day, viz., 17 Dec. 71, at the American equator, with large evening peaks on both 17th and 18th. The northern hemisphere does not exhibit any large change in the critical frequency of the F layer. The reported changes in TEC measurements are not reflected in the parameter f0F2 at Lindau