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We present results from the first comprehensive small‐scale flux rope survey between 0.3 and 5.5 AU using the Helios 1, Helios 2, IMP 8, Wind, ACE, and Ulysses spacecrafts to examine their occurrence rate, properties, and evolution. Small‐scale flux ropes are similar to magnetic clouds and can be modeled as a constant‐alpha, force‐free, cylindrically symmetric flux rope. They differ from magnetic clouds in that they have durations on the order of tens of minutes up to a few hours, they lack an expansion signature at 1 AU, and they do not have a depressed proton temperature compared to the surrounding solar wind plasma. The occurrence rate of small‐scale flux ropes is slightly higher in the inner heliosphere than the outer heliosphere and has a weak dependence on the phase of the solar cycle. The duration of the events as a function of radial distance indicates there is a large, rapid expansion within 1 AU and it becomes constant in the outer heliosphere. This behavior implies small‐scale flux ropes are created and nearly complete their evolution within 1 AU.

While the formation of equatorial electrojet (EEJ) and its temporal variation is believed to be fairly well understood, the longitudinal variability at all local times is still unknown. This paper presents a case and statistical study of the longitudinal variability of dayside EEJ for all local times using ground-based observations. We found EEJ is stronger in the west American sector and decreases from west to east longitudinal sectors. We also confirm the presence of significant longitudinal difference in the dusk sector pre-reversal drift, using the ion velocity meter (IVM) instrument onboard the C/NOFS satellite, with stronger pre-reversal drift in the west American sector compared to the African sector. Previous satellite observations have shown that the African sector is home to stronger and year-round ionospheric bubbles/irregularities compared to the American and Asian sectors. This study's results raises the question if the vertical drift, which is believed to be the main cause for the enhancement of Rayleigh–Taylor (RT) instability growth rate, is stronger in the American sector and weaker in the African sector – why are the occurrence and amplitude of equatorial irregularities stronger in the African sector?

Accurate estimation of global vertical distribution of ionospheric and plasmaspheric density as a function of local time, season, and magnetic activity is required to improve the operation of space‐based navigation and communication systems. The vertical density distribution, especially at low and equatorial latitudes, is governed by the equatorial electrodynamics that produces a vertical driving force. The vertical structure of the equatorial density distribution can be observed by using tomographic reconstruction techniques on ground‐based global positioning system (GPS) total electron content (TEC). Similarly, the vertical drift, which is one of the driving mechanisms that govern equatorial electrodynamics and strongly affect the structure and dynamics of the ionosphere in the low/midlatitude region, can be estimated using ground magnetometer observations. We present tomographically reconstructed density distribution and the corresponding vertical drifts at two different longitudes: the East African and west South American sectors. Chains of GPS stations in the east African and west South American longitudinal sectors, covering the equatorial anomaly region of meridian ∼37°E and 290°E, respectively, are used to reconstruct the vertical density distribution. Similarly, magnetometer sites of African Meridian B‐field Education and Research (AMBER) and INTERMAGNET for the east African sector and South American Meridional B‐field Array (SAMBA) and Low Latitude Ionospheric Sensor Network (LISN) are used to estimate the vertical drift velocity at two distinct longitudes. The comparison between the reconstructed and Jicamarca Incoherent Scatter Radar (ISR) measured density profiles shows excellent agreement, demonstrating the usefulness of tomographic reconstruction technique in providing the vertical density distribution at different longitudes. Similarly, the comparison between magnetometer estimated vertical drift and other independent drift observation, such as from VEFI onboard Communication/Navigation Outage Forecasting System (C/NOFS) satellite and JULIA radar, is equally promising. The observations at different longitudes suggest that the vertical drift velocities and the vertical density distribution have significant longitudinal differences; especially the equatorial anomaly peaks expand to higher latitudes more in American sector than the African sector, indicating that the vertical drift in the American sector is stronger than the African sector. Key Points Longitudinal vertical ionospheric density distributions difference Simultaneous observation of vertical drift and density distribution Validation of in situ density using tomographically imaged density

Solar coronal mass ejections and their interplanetary counterparts often show evidence of a twisted flux rope structure that is nearly identical, though of vastly different spatial scale, to plasmoids observed in the Earth's magnetotail. This paper reviews the current understanding of flux rope formation, morphology, and evolution in coronal mass ejections and magnetotail plasmoids. It highlights the idea that flux rope formation is a common space physics phenomenon and that the physical mechanisms responsible for flux rope formation occur over a wide range of plasma conditions wherever current sheets exist.

On 21 October 2010, ARTEMIS spacecraft P2, located at about −57 in the Earth's magnetotail, observed a series of flux ropes during the course of a moderate substorm. Subsequently, ARTEMIS spacecraft P1, located about 20 RE farther downtail and farther into the lobe than P2, observed a series of TCRs, consistent with the flux ropes observed by P2. The dual‐spacecraft configuration allows simultaneous examination of these phenomena, which are interpreted as an O‐line, followed by a series of flux ropes/TCRs. An inter‐spacecraft time of flight analysis, assuming tailward propagation of cross‐tail aligned ropes, suggests propagation speeds of up to ∼2000 km/s. A principal axis investigation, however, indicates that the flux ropes were tilted between 41° and 45° in the GSM x‐y‐plane with respect to the noon‐midnight meridional plane. Taking this into account, the tailward propagation speed of the different flux ropes is determined to be between 900 and 1400 km/s. The same timing analysis also reveals that the flux rope velocity increased progressively from one flux rope to the next. A clear correlation between the magnetic field and plasma flow components inside the flux ropes was observed. As possible mechanisms leading to the formation of tilted flux ropes we suggest (a) a progressive spreading of the reconnection line along the east‐west direction, leading to a boomerang‐like shape and (b) a tilting of flux ropes during their formation by non‐uniform reconnection with open field lines at the ends of the flux ropes. The progressive increase in the propagation velocity from the first to the last flux rope may be evidence of impulsive reconnection: initially deep inside the plasma sheet the reconnection rate is slow but as reconnection proceeds at the plasma sheet boundary and possibly lobes, the reconnection rate increases. Key Points Tilt of flux ropes Acceleration of a series of flux ropes Progressive reconnection

We present state‐of‐the‐art multiple instrument observations of an isolated substorm on October 12, 2007. The auroral breakup was observed simultaneously by Reimei, THEMIS ASI, and PFISR. The footprint of Geotail was also near the breakup. These observations allow for detailed study of the breakup location in terms of large‐ and small‐scale auroral morphology, particle precipitation, and ionospheric convection, which has not previously been achieved. It also allows for detailed identification of the sequence leading to the breakup. We report the first spaceborne high spatial and temporal resolution images of part of a breakup arc and a wave‐like auroral enhancement captured by Reimei. Observations suggest a sudden plasma sheet thinning initiated ∼10 min before the onset. Wave‐like auroral enhancements were observed twice at the most equatorward arc ∼3 min and ∼1 min before the breakup. These enhancements are likely due to some near‐Earth instability, such as ballooning instability. Unlike the usual substorm sequence, this most equatorward arc did not develop into the breakup arc but remained almost stable until being engulfed by the auroral equatorward expansion from higher latitude after onset. The wave‐like auroral enhancement was associated with three fine inverted V arcs and embedded within energetic ion precipitation. Following this enhancement, an arc, likely a poleward boundary intensification, formed at higher latitude just adjacent to the plasma sheet boundary layer (PSBL). This arc then extended southwestward and led to the breakup arc, which was located poleward of the wavy structures. Assuming longitudinal homogeneity of ion precipitation over 1°, this breakup arc was located in a region without ion precipitation just poleward of the energetic ion precipitation. These observations suggest the possible existence of a low‐entropy flow channel associated with the arc adjacent to the PSBL, which might be associated with instability in the near‐Earth plasma sheet responsible for the auroral breakup.

Issue Title: International Heliophysical Year 2007: Second European General Assembly, Italy | Third UN/ESA/NASA Workshop, Japan The AMBER array contains four magnetometers and spans across the geomagnetic equator from L of 1 to an L of 1.4. In addition to filling the largest land-based gap in global magnetometer coverage, the AMBER array will address two fundamental areas of space physics: (1) the processes governing electrodynamics of the equatorial ionosphere as a function of latitude (or L-shell), local time, longitude, magnetic activity, and season, and (2) ULF pulsation strength and its connection with equatorial electrojet strength at low/mid-latitude regions. Satellite observations show unique equatorial ionospheric structures in the African sector, though these have not been confirmed by observation from the ground due to lack of ground-based instruments in the region. In order to have a complete global understanding of equatorial ionosphere motions, deployment of ground-based magnetometers in Africa is essential. One focus of IHY is the deployment of networks of small instruments, including the development of research infrastructure in developing nations through the United Nations Basic Space Science (UNBSS) Small Instrument Array. Therefore, AMBER magnetometer array in partnership with parallel US funded GPS receivers in Africa will allow us to understand the electrodynamics that governs equatorial ionosphere motions. While AMBER routinely observes the F region plasma drift mechanism (E × B drift), the GPS stations will monitor the structure of plasma at low/mid-latitudes in the African sectors. In addition to new scientific discoveries and advancing the space science research into Africa by establishing scientific collaborations between scientists in the developing and developed nations, the AMBER project also contributes to developing the basic science of heliophysics through cross-disciplinary studies of universal process. This includes the creation of sustainable research/training infrastructure within the developing nations (Africa). [PUBLICATION ABSTRACT]

A statistical study comparing the plasmapause location determined using extreme ultraviolet (EUV) and cross‐phase measurements was performed over 50 days in May–July 2000 and 1 day in May 2008. In EUV images the plasmapause location was estimated using the sharp gradient in the brightness of 30.4 nm He+ emission. We have taken EUV images obtained by the IMAGE and the Kaguya satellites, which were operated in a solar maximum and minimum periods, respectively. In the ground‐based cross‐phase measurement, the plasmapause was defined as a steep drop of mass density in its radial profile. Mass density was inferred from the eigenfrequency of field line resonances in the ULF band (∼1–1000 mHz), which was deduced from geomagnetic field data using cross‐phase analysis. The two measurements of the plasmapause have been compared in a same meridian at the same time and very good agreement was found in 18 of 19 events. Our result clearly indicates that the He+ and mass density plasmapause are usually detected at the same place with the error range of ± 0.4 RE. In only one event, the He+ and the mass density defined plasmapauses were not colocated. This event may be due to the difference of refilling time between He+ and other dominant species.

Simultaneous IMAGE EUV plasmaspheric images and Magnetospheric Plasma Analyzer (MPA) data from the Los Alamos National Laboratory's geosynchronous satellites are combined to understand plasmaspheric behavior and to quantify the global images. A brief review of the understanding of the plasmasphere as learned from in situ observations prior to the launch of IMAGE is given to place the results presented here into context.