Abstract. This paper describes the development of a major space storm during November 2-11, 1993. We discuss the history of the contributing high-speed stream, the powerful combination of solar wind transients and a corotating interaction region which initiated the storm, the high-speed flow which prolonged the storm and the near-Earth manifestations of the storm. The 8-day storm period was unusually long; the result of a high-speed stream (maximum speed 800 km/s) emanating from a distended coronal hole. Storm onset was accompanied by a compression of the entire dayside magnetopause to within geosynchronous Earth orbit (GEO). For nearly 12 hours the near-Earth environment was in a state of tumult. A super-dense plasma sheet was observed at GEO, and severe spacecraft charging was reported. The effects of electrons precipitating into the atmosphere penetrated into the stratosphere. Subauroral electron content varied by 100% and F layer heights oscillated by 200 km. Equatorial plasma irregularities extended in plumes to heights of 1400 km. Later, energetic particle fluxes at GEO recovered and rose by more than an order of magnitude. A satellite anomaly was reported during the interval of high energetic electron flux. Model results indicate an upper atmospheric temperature increase of 200øK within 24 hours of storm onset. Joule heating for the first 24 hours of the storm was more than 3 times that for typical active geomagnetic conditions. We estimate that total global ionospheric heating for the full storm interval was-190 PJ, with 30% of that generated within 24 hours of storm onset.
Abstract. Temporal and spatial evolution of two highaltitude plasma bubbles (evening and midnight) was observed on 4 April 2002, at geomagnetic conjugate points at Sata, Japan (magnetic latitude 24 • N), and Darwin, Australia (magnetic latitude 22 • S), using two 630-nm airglow imagers. The apex height of the bubbles reached ∼1500 km. The upward velocity of the evolution was faster in the evening (∼170 m/s at 20:00-21:00 LT) than around midnight (∼28 m/s at 23:00-00:00 LT). Bifurcating features of the bubbles into a smaller scale size of ∼50 km were clearly seen for both the evening and midnight bubbles, showing fairly good conjugacy between the Northern and Southern Hemispheres.
Abstract. We report on a study of three intense ionospheric storms that occurred in September 1989. Using Dst as a reference for storm onset and subsequent main and recovery phases, we analyze the observed worldwide responses of F region heights hmF 2 and densities NmF 2 as a function of universal and local times, latitudinal domains, and storm onset-times; and we compare the characteristics of all three storms. The following points are among the major findings: (1) The negative phase storm was the dominant characteristic, with the greatest intensity occurring in the regions which were in the nighttime hemisphere during the main phase; (2) at middle and low latitudes negative phase characteristics were observed first in the nighttime hemisphere and then corotated with the Earth into the dayside; (3) the most intense negative response occurred in the recovery phase; (4) observations of the negative phase characteristics supported thermospheric upwelling, increased mean molecular mass, and an associated enhancement in dissociative recombination as the principal cause-effect chain; but the observations suggest greater ion-neutral chemistry effects than accounted for in current models; (5) hmF2 was observed to respond quickly to the storm onset (pointing to the importance of electric fields) with enhanced values in all latitudinal and local time domains; (6) positive storm characteristics were among the issues most difficult to reconcile with current descriptions of cause-effect relationships; and (7) the analysis of all storm phases and comparisons with several modeling efforts show that future advances in understanding require a more accurate accounting of the influences of magnetospherically-imposed and dynamo-driven electric fields, plasmaspheric fluxes, and vibrationally excited N 2.
We demonstrate that conventional ionosondes can provide long‐term observations of intermediate, descending, and transitional layers in the 100–200 km altitude region of the ionosphere. Using 15 consecutive days of observations at Townsville, Australia, during the SUNDIAL campaign of September 1989, we tracked the “birth” of the layers at altitudes above 150 km and their systematic downward motion to the 110 km region at rates between 4 and 5 km/hr. The observations are compared with NCAR TIGCM simulations, and the results show: (i) that the layering process is identifiable with meridional wind‐shear‐node convergence of ions; (ii) that zonal wind controls of the layers are insignificant under the prevailing conditions; and (iii) that electric fields play an important role in the effectiveness of the ion‐convergence and downward transport processes at altitudes above 125 km. The measurement and modelling comparisons are the first of a kind, providing insight into the relative roles of winds and electric fields, and opening possibilities for determining the global characteristics of the layers and their cause‐effect roles in the dynamics of the lower ionospheric‐thermospheric domain.
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