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Spatial structures in ionospheric electron density revealed in a tomographic image have been identified with auroral forms and related to their sources in precipitating particles observed by DMSP satellites. The observations of plasma enhancements relate to discrete auroral arcs seen in the post-noon sector, identified by both red- and green-line emissions measured by a meridional scanning photometer. The features lie within a very narrow latitudinal band on L-shells where the satellite detectors observed electron precipitation classified as from the boundary plasma sheet (BPS). The harder particles are identified with an E-region structure, while further north the precipitation is softer, resulting in a localised F-layer blob and 630.0 nm emissions. A steep gradient in plasma density represent a signature in the ionosphere of the central plasma sheet (CPS)/BPS boundary. A transition to a less-structured F-layer is found on crossing the convection reversal boundary..Key words. Ionosphere (auroral ionosphere; ionosphere-magnetosphere interactions; polar ionosphere)

The observations from the GOES (Geostationary Operational Environmental Satellites) are critical for monitoring a wide range of land, ocean, atmosphere, and space weather phenomena. With both earth-pointing and sun-pointing instruments, GOES monitors the Earth, the Sun, and the space environment. While the GOES are often referred to as “weather satellites,” they are truly environmental satellites. The GOES are also used as communications satellites, including search and rescue and data collection retransmission services.

A new sunspot and faculae digital dataset for the interval 1874 – 1955 has been prepared under the auspices of the NOAA National Geophysical Data Center (NGDC). This digital dataset contains measurements of the positions and areas of both sunspots and faculae published initially by the Royal Observatory, Greenwich, and subsequently by the Royal Greenwich Observatory (RGO), under the title Greenwich Photo-heliographic Results (GPR), 1874 – 1976. Quality control (QC) procedures based on logical consistency have been used to identify the more obvious errors in the RGO publications. Typical examples of identifiable errors are North versus South errors in specifying heliographic latitude, errors in specifying heliographic (Carrington) longitude, errors in the dates and times, errors in sunspot group numbers, arithmetic errors in the summation process, and the occasional omission of solar ephemerides. Although the number of errors in the RGO publications is remarkably small, an initial table of necessary corrections is provided for the interval 1874 – 1917. Moreover, as noted in the preceding companion papers, the existence of two independently prepared digital datasets, which both contain information on sunspot positions and areas, makes it possible to outline a preliminary strategy for the development of an even more accurate digital dataset. Further work is in progress to generate an extremely reliable sunspot digital dataset, based on the long programme of solar observations supported first by the Royal Observatory, Greenwich, and then by the Royal Greenwich Observatory.

Attention is drawn to the existence of errors in the original digital dataset containing sunspot data extracted from certain sections of the printed Greenwich Photo-heliographic Results (GPR) 1874 – 1976. Calculating the polar coordinates from the heliographic coordinates and comparing them with the recorded polar coordinates reveals that there are both isolated and systematic errors in the original sunspot digital dataset, particularly during the early years (1874 – 1914). It should be noted that most of these errors are present in the compiled sunspot digital dataset and not in the original printed copies of the Greenwich Photo-heliographic Results. Surprisingly, many of the errors in the digitised positions of sunspot groups are apparently in the measured polar coordinates, not the derived heliographic coordinates. The mathematical equations that are used to convert between heliographic and polar coordinate systems are formulated and then used to calculate revised (digitised) polar coordinates for sunspot groups, on the assumption that the heliographic coordinates of every sunspot group are correct. The additional complication of requiring accurate solar ephemerides in order to solve the mathematical equations is discussed in detail. It is shown that the isolated and systematic errors, which are prevalent in the sunspot digital dataset during the early years, disappear if revised polar coordinates are used instead. A comprehensive procedure for checking the original sunspot digital dataset is formulated in an Appendix.

The measurements of sunspot positions and areas that were published initially by the Royal Observatory, Greenwich, and subsequently by the Royal Greenwich Observatory (RGO), as the Greenwich Photo-heliographic Results (GPR), 1874 – 1976, exist in both printed and digital forms. These printed and digital sunspot datasets have been archived in various libraries and data centres. Unfortunately, however, typographic, systematic and isolated errors can be found in the various datasets. The purpose of the present paper is to begin the task of identifying and correcting these errors. In particular, the intention is to provide in one foundational paper all the necessary background information on the original solar observations, their various applications in scientific research, the format of the different digital datasets, the necessary definitions of the quantities measured, and the initial identification of errors in both the printed publications and the digital datasets. Two companion papers address the question of specific identifiable errors; namely, typographic errors in the printed publications, and both isolated and systematic errors in the digital datasets. The existence of two independently prepared digital datasets, which both contain information on sunspot positions and areas, makes it possible to outline a preliminary strategy for the development of an even more accurate digital dataset. Further work is in progress to generate an extremely reliable sunspot digital dataset, based on the programme of solar observations supported for more than a century by the Royal Observatory, Greenwich, and the Royal Greenwich Observatory. This improved dataset should be of value in many future scientific investigations.

Part of Special Issue "Eleventh International EISCAT Workshop" Abstract. Results are presented from a multi-instrument study of the spatial distribution of the summertime, polar ionospheric electron density under conditions of relatively stable IMF Bz

A continuous band of high ion temperature, which persisted for about 8h and zigzagged north-south across more than five degrees in latitude in the dayside (07:00-15:00MLT) auroral ionosphere, was observed by the EISCAT VHF radar on 23 November 1999. Latitudinal gradients in the temperature of the F-region electron and ion gases (Te and Ti, respectively) have been compared with concurrent observations of particle precipitation and field-perpendicular convection by DMSP satellites, in order to reveal a physical explanation for the persistent band of high Ti, and to test the potential role of Ti and Te gradients as possible markers for the open-closed field line boundary. The north/south movement of the equatorward Ti boundary was found to be consistent with the contraction/expansion of the polar cap due to an unbalanced dayside and nightside reconnection. Sporadic intensifications in Ti, recurring on ~10-min time scales, indicate that frictional heating was modulated by time-varying reconnection, and the band of high Ti was located on open flux. However, the equatorward Ti boundary was not found to be a close proxy of the open-closed boundary. The closest definable proxy of the open-closed boundary is the magnetosheath electron edge observed by DMSP. Although Te appears to be sensitive to magnetosheath electron fluxes, it is not found to be a suitable parameter for routine tracking of the open-closed boundary, as it involves case dependent analysis of the thermal balance. Finally, we have documented a region of newly-opened sunward convecting flux. This region is situated between the convection reversal boundary and the magnetosheath electron edge defining the open-closed boundary. This is consistent with a delay of several minutes between the arrival of the first (super-Alfvénic) magnetosheath electrons and the response in the ionospheric convection, conveyed to the ionosphere by the interior Alfvén wave. It represents a candidate footprint of the low-latitude boundary mixing layer on sunward convecting open flux.

The focus of the study is a region of enhanced ionospheric densities observed by the EISCAT Svalbard radar in the polar F-region near local magnetic noon under conditions of IMF Bz Key words. Ionosphere (polar ionosphere; plasma temerature; plasma convection)

The Cluster spacecraft experienced several boundary layer encounters when flying outbound from the magnetosphere to the magnetosheath in the dusk sector on 14 January 2001. The dayside boundary layer was populated by magnetosheath electrons, but not with quite as high densities as in the magnetosheath itself. The Cluster ground track was calculated using the Tsyganenko-96 model which appears to be a strong tool for combining high-altitude satellite and ground observations, given that the solar wind conditions are known. This paper focuses on identifying auroral responses corresponding to boundary layer dynamics observed by Cluster. The first boundary layer encounter studied was a brief visit into a closed LLBL, most likely due to a boundary wave that travelled tailward over the spacecraft. A corresponding equatorward and eastward movement was seen in the post-noon aurora between Greenland and Svalbard. The second boundary encounter was in a high-latitude cusp, and occurred as a consequence of a transient reconfiguration of the cusp. The cusp expanded duskward over the spacecraft into the late post-noon sector. NOAA-12 probed the 16:30 MLT sector of this auroral activity, and measured a 1.4 keV electron beam located poleward of the 30 keV electron-trapping boundary. A sequence of three moving auroral forms emanating from this active region are likely candidates for flux transfer events. The auroral signatures are discussed in relation to earlier observations, and appear to be an example of accelerated electrons/discrete post-noon aurora on open magnetic field lines.Key words. Ionosphere (particle precipitation) Magnetospheric physics (auroral phenomena; magnetopause, cusp and boundary layers)

A characteristic sequence of poleward moving auroral events and the associated ground magnetic deflections in the vicinity of cusp-type precipitation in the convection throat are studied. The occurrence, structure, and motion pattern of these events are found to be strongly regulated by the IMF Bz and By components. The present cases are observed in the prenoon sector during positive IMF By and negative Bz conditions. New, improved results on the dynamical structure of the magnetosphere-ionosphere current system of these events are obtained. The current system consists of a central filament or sheet-like field-aligned current (FAC), located on newly opened field lines with oppositely directed return currents on the poleward and equatorward sides. The ground magnetic deflections can be explained by ionospheric Hall currents generated by this FAC system and the associated pattern of ionospheric electric fields. The propagation speed of the events (auroral and magnetic signatures) are found to be comparable with the simultaneously observed antisunward convection speeds (1–2 km/s); that is, they are related to the tailward convection of newly opened magnetic flux. A qualitatively similar current system with opposite current polarity has recently been proposed for the corresponding auroral and magnetic signatures observed during negative IMF By conditions. The events are found to be consistent with an interpretation in terms of pulsed magnetopause reconnection, that is, flux transfer events.

10 second resolution ionospheric convection data covering the invariant latitude range from 71° to 76°, obtained by using the EISCAT UHF and VHF radars, are combined with optical data from Ny Alesund during a sequence of auroral transients in the post-noon sector (∼ 15 MLT). Satellite observations of polar cap convection patterns suggest negative BZ and BY components of the interplanetary magnetic field. Burst-like enhancements of westward (sunward) post-noon convection were accompanied by eastward moving auroral forms at higher latitudes, above the convection reversal boundary. In this case the background convection was weak, whereas the integrated potential drop across the radar field-of-view associated with the westward flow bursts was typically ∼ 20-35 kV. The auroral phenomenon consists of a series of similar events with a mean repetition period of 8 min. A close correlation between the auroral activity and convection enhancements in the cleft ionosphere is demonstrated.

We present an analysis of a “quasi-steady” cusp ion dispersion signature observed at low altitudes. We reconstruct the field-parallel part of the Cowley-D ion distribution function, injected into the open LLBL in the vicinity of the reconnection X-line. From this we find the field-parallel magnetosheath flow at the X-line was only 20 ± 60 km s−1, placing the reconnection site close to the flow streamline which is perpendicular to the magnetosheath field. Using interplanetary data and assuming the subsolar magnetopause is in pressure balance, we derive a wealth of information about the X-line, including: the density, flow, magnetic field and Alfvén speed of the magnetosheath; the magnetic shear across the X-line; the de-Hoffman Teller speed with which field lines emerge from the X-line; the magnetospheric field; and the ion transmission factor across the magnetopause. The results indicate that some heating takes place near the X-line as the ions cross the magnetopause, and that sheath densities may be reduced in a plasma depletion layer. We also compute the reconnection rate. Despite its quasi-steady appearance on an ion spectrogram, this cusp is found to reveal a large pulse of enhanced reconnection rate.

At a time when most polar cap ionospheric studies are focused on electron density enhancements caused by patches or arcs, this paper discusses an F region depletion known as the ionospheric polar hole. Statistically, polar holes tend to develop on the nightside from 2100–0600 MLT between 70°–80°Λ. Electron concentrations as small as 2×102 cm−3 at altitudes near 300 km have previously been observed in polar holes during solar minimum winter conditions. Under magnetically quiet conditions, polar holes are thought to form due to slow convection of plasma across the polar cap. The electron concentration is depleted by normal recombination processes during many hours spent in the dark polar cap. In contrast with previous studies, which have tended to be statistical in nature, this paper describes the temporal and spatial development of a single polar hole. During the Geospace Environment Modelling Pilot Program of January 16,1990, the development of the polar hole was monitored by the DMSP F8 and F9 satellites, a digital ionosonde and a 250-MHz scintillation receiver. The data reveal that the polar hole is a very dynamic phenomenon, and its location can change dramatically within several hours. This is the first study of the polar hole using ground based instruments. The observations presented here are of interest not only because they contribute to a morphological understanding of the polar hole, but also because they illustrate the influence of the polar hole on radio signals propagating in the ionospheric medium. The results are of direct relevance to applications and systems involving ionospheric and transionospheric propagation. The data set is sufficiently complete that it will provide rigorous constraints for future modeling studies and will thus contribute to a better physical understanding of the polar hole.

A specific category of auroral event sequence taking place at the dayside polar cap boundary during southward-directed interplanetary magnetic field (IMF) is exemplified by three cases of combined ground and satellite observations. The detailed temporal and spatial evolution of these optical events were monitored by all-sky TV imagery mapped onto a geographic coordinate system. Profiles along the satellite track of particle precipitation and ionospheric convection in the vicinity of the optical events were important for the determination of the solar wind - magnetosphere coupling mode involved. The observed north-westward event motion in the prenoon sector is typical for periods of positive IMF B Y . Auroral events associated with negative IMF B Y were moving northeastward in the midday and early post-noon sector. The optical events mostly appear as a brightening of the 630.0 nm aurora near the poleward boundary of the persistent cleft/LLBL precipitation at the boundary of the field-of-view of the TV camera. A continuous motion into the polar cap (mantle precipitation) was observed before the optical emission faded out after 10–15 minutes, typically ∼500 km poleward of the continuous cleft arc. The auroral forms typically cover ∼500 km in the east - west direction and ∼200 km in the north - south direction. A glow of 630.0 nm emission spanning ∼500 km in latitudinal extent was observed during the decay phase of the Jan. 12, 1991 case presented here. The optical, particle and ion drift observations in combination with the available IMF and solar wind plasma data indicate that the events represent dynamical structures of IMF B Y -related Dungey cell convection over the polar magnetosphere, initiated by pulses of enhanced merging rate (B n ≠ 0) at the dayside magnetopause.

THE plasma precipitating into the Earth's dayside auroral atmosphere has characteristics which show that it originates from the shocked solar-wind plasma of the magnetosheath1'2. The particles of the magnetosheath plasma precipitate down a funnel-shaped region (cusp) of open field lines resulting from reconnection of the geomagnetic field with the interplanetary magnetic field3. Although the cusp has long been considered a well defined spatial structure maintained by continuous reconnection, it has recently been suggested4–6 that reconnection instead may take place in a series of discontinuous events; this is the ‘pulsating cusp model’. Here we present coordinated radar and satellite observations of a series of discrete, poleward-moving plasma structures that are consistent with the pulsating-cusp model.

The geomagnetic storm of March 1989 was the largest geomagnetic storm of the decade and one of the largest of the century. We review many of the "high-latitude" ionospheric observations that were made during this storm. Most of the data presented here comes from the polar-orbiting satellites of the Defense Meteorological Satellite Program (DMSP) series. A review of the DMSP data shows that most of the high-latitude, top-side ionospheric disturbance occurred on March 13 and 14. The magnitudes of the particle energy flux (ergs cm−2) (1 erg = 10−7 J) and Joule heating were not unusually large for a storm, but the area of the energy deposition, and thus the total energy deposition, was extremely large. At the peak of the storm (minimum in Dst (disturbance with storm time) and midnight boundary indices) the auroral particle precipitation extended down to magnetic latitudes of 40.1° or L = 1.71 while the polar edge of the auroral zone expanded poleward only slightly. The storm was also a period of intense, hemispherically symmetric polar rain fluxes. The auroral electric field was clearly observed down to magnetic latitude of 35°. This is consistent with the auroral electrojet (AE) current density and the AE index having a saturation level beyond which the index will increase slowly or not at all as more energy is transferred from the solar wind to the magnetosphere, but the cross polar-cap potential during this storm shows no evidence of saturation. There are only two visible light images from DMSP available near the peak of the storm. These images and one UV image from the Dynamics Explorer (DE) satellite at approximately the same time show the distribution of the aurora just after the peak of the storm. Comparison of the DMSP particle data with the DE-1 UV image indicates that the bifurcation of the auroral luminosity in the UV image is probably an effect of the DE-1 UV instrument's sensitivity limits; the DMSP data show no evidence for bifurcation of the auroral zone.

In this paper we focus on flux transfer events (FTEs) and poleward moving auroral forms (PMAFs) in the cusp region, combining data from the EISCAT Svalbard radar, SuperDARN HF radars, ground-based optics, and three low-altitude polar-orbiting spacecraft. During an interval of southward interplanetary magnetic field the EISCAT Svalbard radar tracked a train of narrow flow channels drifting into the polar cap. One 30-60 km wide flow channel surrounded by flow running in the opposite direction is studied in great detail from when it formed equatorward of the cusp aurora, near magnetic noon, until it left the field-of-view and disappeared into the polar cap. Satellite data shows that the flow channel was on open field lines. The flow pattern is consistent with field-aligned currents on the sides of the flow channel; with a downward current on the equatorward side, and an upward current on the poleward side. The poleward edge of the flow channel was coincident with a PMAF that separated from the background cusp aurora and drifted into the polar cap. A passage of the DMSP F13 spacecraft confirms that the FTE flow channel was still discernable over 15 minutes after it formed, as the spacecraft revealed a 30–40 km wide region of sunward flow within the anti-sunward background convection. From the dimensions of the flow channel we estimate that the magnetic flux contained in the event was at least 1 MWb. This data set also shows that Birkeland current filaments often seen by low-altitude spacecraft in the cusp/mantle are really associated with individual FTE events or a train of FTEs in progress. As the region 0 or cusp/mantle current represents the statistical average consistent with the large-scale flow pattern, we therefore introduce a new term – FTE currents – to denote the unique pair of Birkeland current sheets that are associated with individual meso-scale FTE flow disturbances. The poleward moving auroral forms (PMAFs), often referred to in the literature, are the optical signature of the upward FTE current. Keywords. Magnetospheric physics (Current systems; Magnetopause, cusp and boundary layers) – Ionosphere (plasma convection)

The assimilative mapping of ionospheric electrodynamics (AMIE) technique has been used to estimate global distributions of high-latitude ionospheric convection and field-aligned current by combining data obtained nearly simultaneously both from ground and from space. Therefore, unlike the statistical patterns, the 'snapshot' distributions derived by AMIE allow us to examine in more detail the distinctions between field-aligned current systems associated with separate magnetospheric processes, especially in the dayside cusp region. By comparing the field-aligned current and ionospheric convection patterns with the corresponding spectrograms of precipitating particles, the following signatures have been identified: (1) For the three cases studied, which all had an IMF with negative y and z components, the cusp precipitation was encountered by the DMSP satellites in the postnoon sector in the northern hemisphere and in the prenoon sector in the southern hemisphere. The equatorward part of the cusp in both hemispheres is in the sunward flow region and marks the beginning of the flow rotation from sunward to antisunward. (2) The pair of field-aligned currents near local noon, i.e., the cusp/mantle currents, are coincident with the cusp or mantle particle precipitation. In distinction, the field-aligned currents on the dawnside and duskside, i.e., the normal region 1 currents, are usually associated with the plasma sheet particle precipitation. Thus the cusp/mantle currents are generated on open field lines and the region 1 currents mainly on closed field lines. (3) Topologically, the cusp/mantle currents appear as an expansion of the region 1 currents from the dawnside and duskside and they overlap near local noon. When B(sub y) is negative, in the northern hemisphere the downward field-aligned current is located poleward of the upward current; whereas in the southern hemisphere the upward current is located poleward of the downward current. (4) Under the assumption of quasi-steady state reconnection, the location of the separatrix in the ionosphere is estimated and the reconnection velocity is calculated to be between 400 and 550 m/s. The dayside separatrix lies equatorward of the dayside convection throat in the two cases examined.

This paper presents a case study of the dayside auroral behavior during a rapid expansion of the auroral oval. An unstructured auroral form characterized by a large I(630.0 nm)/ I(557.7 nm) ratio is observed to rapidly drift from the east into the field of view of a set of ground based instruments. Corroborating sets of DMSP satellite particle precipitation and ion drift measurements are presented to show that the cusp is probably located to the east of the ground station and that the diffuse auroral forms observed at the ground site may be related to magnetic merging in the polar cusp.

A simulation was conducted to model the high-latitude ionospheric to the sustaied level of high geomagnetic activity for the great magnetic storm period of March 13-14, 1989. The geomagnetic and solar activity indices and the Defense Meterological Satellite Program (DMSP) F8 and F9 satellite data for particle precipitation and high-latitude convection were used as inputs to a time-dependent ionospheric model (TDIM). The results of the TDIM were compared to both DMSP plasma density data and ground-based total electron content (TEC) measurements for the great storm period as well as with earlier storm observations. The comparisons show that the overall structure of the high-latitude ionosphere was dominated by an increased convection speed within the polar cap that led to increased ion temperatures. In turn, this enhanced the NO(+) density, raised the atomic-to-molecular ion transition height to over 300 km, decreased N(sub m)F(sub 2), increased h(sub m)F(sub 2), and in places either increased n(sub e) at 800 km or slightly decreased it. The morphology of the ionosphere under these extreme conditions was considerably different than that modeled for less distributed intervals. These differences included the character of the dayside tongue of ionization that no longer extended deep into the polar cap. Instead, as a result of the ion heating and consequent reduction in N(sub m)F(sub 2), a large polar hole occupied much of the polar region. This polar hole extended beyond the auroral oval and merged with the night sector midatitude trough. The limitaions associated with the applicability of the TDIM to the geomagnetic conditions present on March 13 and 14 are discussed. The primary limitations of the TDIM derive from the limited temporal resolution of the model input parameters and the lack of suitably dynamic thermospheric specification for the great storm conditions. These limitations leads to midlatitude ionospheric storm phases that do no follow those observed.

The assimilative mapping of ionospheric electrodynamics technique has been used to derive the large-scale high-latitude ionospheric convection patterns simultaneously in both northern and southern hemispheres during the period of January 27-29, 1992. When the interplanetary magnetic field (IMF) Bz component is negative, the convection patterns in the southern hemisphere are basically the mirror images of those in the northern hemisphere. The total cross-polar-cap potential drops in the two hemispheres are similar. When Bz is positive and |By| > Bz, the convection configurations are mainly determined by By and they may appear as normal “two-cell” patterns in both hemispheres much as one would expect under southward IMF conditions. However, there is a significant difference in the cross-polar-cap potential drop between the two hemispheres, with the potential drop in the southern (summer) hemisphere over 50% larger than that in the northern (winter) hemisphere. As the ratio of |By|/Bz decreases (less than one), the convection configuration in the two hemispheres may be significantly different, with reverse convection in the southern hemisphere and weak but disturbed convection in the northern hemisphere. By comparing the convection patterns with the corresponding spectrograms of precipitating particles, we interpret the convection patterns in terms of the concept of merging cells, lobe cells, and viscous cells. Estimates of the “merging cell” potential drops, that is, the potential ascribed to the opening of the dayside field lines, are usually comparable between the two hemispheres, as they should be. The “lobe cell” provides a potential between 8.5 and 26 k V and can differ greatly between hemispheres, as predicted. Lobe cells can be significant even for southward IMF, if |By| > |Bz|. To estimate the potential drop of the “viscous cells,” we assume that the low-latitude boundary layer is on closed field lines. We find that this potential drop varies from case to case, with a typical value of 10 kV. If the source of these cells is truly a viscous interaction at the flank of the magnetopause, the process is likely spatially and temporally varying rather than steady state.

Results are presented of observations of strong VHF plasma waves with amplitudes in excess of 0.1 mV/m (Hz)1/2 associated with 50 mA electron beam injections in the ionosphere. Data from three swept-frequency receivers carried on two daughter payloads are analyzed to determine the emission spectra of the electron beam for various energies and currents. These results were obtained from the rocket-borne experiment SCEX 3, NASA flight 39.002 UE, launched February 1, 1990. The accelerator payload also carried photometers, which measured luminosity at wavelengths of 391.4 and 380.5 nm. Several times during electron gun activity the measured luminosity increased much faster than proportional to the beam current. This nonlinear increase is evidence that a discharge is occurring in the vicinity of the accelerator payload. It is inferred from the uniform distribution of the luminosity around the accelerator payload that the observed discharge extends significantly outside the beam cylinder.

A comparison of nucleon-removal differential scattering cross sections at 35/sup 0/ for 190-MeV ..pi../sup + -/ on /sup 27/Al shows p2n removal and single-nucleon removal as the most dominant. Single-nucleon removal is consistent and in good agreement with the one-step-quasifree ..pi..N scattering model, but only if the pion interacts principally with a p2n system. The outgoing nucleon charge exchange probability is measured to be approx.1/3 for approx.16-MeV nucleons. The ..pi..N angular distribution and the proton energy spectrum at 35/sup 0/ also support the one-step-quasifree scattering with the outermost nucleons model.

Gamma‐ray spectra were recently obtained in coincidence with scattered particles for 300‐MeV/c pions on 27Al at LAMPF. Spectra are presented for gamma‐rays in coincidence with scattered pions. The relative cross‐sections for production of residual nuclei which correspond to the removal of an equivalent Li6, α, t and d particles and for single nucleon removal are also presented.

A discussion of recent evidence for pion reaction and clustering from gamma‐ray spectra taken in coincidence with pions, protons, and deuterons from 300‐MeV/c pions on 27Al at LAMPF. The removal of particles equivalent to 7Li, 6Li, α, d, t, and single nucleons are the strongest lines in each of the spectra.

Gamma‐ray spectra were recently obtained in coincidence with particles from 300‐MeV/c pions on 27Al at LAMPF. The spectra of gamma‐rays in coincidence with the protons is presented along with the relative cross‐sections corresponding to the removal of particles equivalent to 6Li, α, t and d particles as well as for single nucleon removal.

Proton and pion spectra obtained in coincidence with the prompt gamma rays following the bombardment of 27Al by 190‐MeV pions provides evidence for quasi‐free single nucleon removal. The single nucleon removal ratios are not in agreement with a single quasi‐free scattering model. However, the proton distributions in coincidence with the respective gamma rays are in good agreement. The angular distributions are also in substantial agreement with a quasi‐free scattering mechanism.

LAMPF experiment ♯319 gives energy spectra of particles and nuclear gamma rays taken in coincidence from 300 MeV/cπ± interactions on 27Al. The particle spectra are strongly indicative of nuclear surface clustering.

Gamma‐ray spectra in coincidence with scattered pions at 35° were obtained for π+ and π− incident on 27Al at LAMPF. The gamma‐ray spectra in coincidence with the scattered π+ or π− were separated into two energy bins each: Eπ′

On 14 January 2001, the four Cluster spacecraft passed through the northern magnetospheric mantle in close conjunction to the EISCAT Svalbard Radar (ESR) and approached the post-noon dayside magnetopause over Green-land between 13:00 and 14:00 UT. During that interval, a sudden reorganisation of the high-latitude dayside convection pattern occurred after 13:20 UT, most likely caused by a direction change of the Solar wind magnetic field. The result was an eastward and poleward directed flow-channel, as monitored by the SuperDARN radar network and also by arrays of ground-based magnetometers in Canada, Greenland and Scandinavia. After an initial eastward and later poleward expansion of the flow-channel between 13:20 and 13:40 UT, the four Cluster spacecraft, and the field line footprints covered by the eastward looking scan cycle of the Söndre Strömfjord incoherent scatter radar were engulfed by cusp-like precipitation with transient magnetic and electric field signatures. In addition, the EISCAT Svalbard Radar detected strong transient effects of the convection reorganisation, a poleward moving precipitation, and a fast ion flow-channel in association with the auroral structures that suddenly formed to the west and north of the radar. From a detailed analysis of the coordinated Cluster and ground-based data, it was found that this extraordinary transient convection pattern, indeed, had moved the cusp precipitation from its former pre-noon position into the late post-noon sector, allowing for the first and quite unexpected encounter of the cusp by the Cluster spacecraft. Our findings illustrate the large amplitude of cusp dynamics even in response to moderate solar wind forcing. The global ground-based data proves to be an invaluable tool to monitor the dynamics and width of the affected magnetospheric regions.Key words. Magnetospheric cusp, ionosphere, reconnection, convection flow-channel, Cluster, ground-based observations

Measurements of field-aligned currents (FAC's), convection electric fields, and precipitating electrons were made by the S3-2 satellite in the midmorning time sectors of both the northern and southern high-latitude ionospheres before and during a geomagnetic storm on June 24–25, 1976. The patterns of electric fields and FAC's did not match the standard configuration of two-cell convection and the region 1/region 2 FAC's. In particular, near the beginning of the main phase of the storm an intense (242 mV/m) convection electric field and an extra FAC were observed just poleward of the region 1 current in the southern hemisphere. The observations, made over a period of at least 3 hours, were consistent with a quasi steady state three-cell convection pattern with stresses from a strong By component of the interplanetary magnetic field (IMF). An analysis of the particle and field data from within the region of the intense convection electric field is in sharp disagreement with the single-particle motion model of Lyons (1980) and implies that a significant portion of the measured FAC was from ionospheric ions. Finally, large-amplitude AC electric waves from broadband electrostatic noise (BEN) were present in the high-altitude southern (or winter) passes but not in the northern passes at lower altitudes. In general, BEN has been observed occasionally by S3-2 within the high-altitude (1000–1500 km) winter auroral regions but has never been detected during other seasons or at lower altitudes. The implication of these measurements is that the low-altitude limit for the region of field-aligned potentials is determined by the local plasma density.

A Fabry-Perot imager that can give spectral image information for the airglow is briefly described. Such an instrument was flown on the shuttle on the STS 41-G mission. Several spectral images of the limb view atmosphere were obtained, and rotational temperatures are derived for two of these images. The rotational temperature for the O2 A band on the limb at the emission intensity maximum was measured as 200°K. Viewing the airglow layer at a downward viewing slant path, the temperature was found to be higher. The rotational temperature was also obtained from images of the airglow at the wavelength of the OH Meinel (8-3) band. The properties of the available filter and Fabry-Perot combination were not ideal for this measurement. From the ratio of the line intensity of the P1(3) and the superimposition of the P2(3) and the Q(2) line the rotational temperature was found to be 220°K. These temperature measurements demonstrate the validity of the technique. Several new experiments are planned where systematic measurements of the atmospheric airglow rotational temperatures will be carried out. Such measurements will provide new insight into the global temperature structure of the mesosphere.