Opportunities for magnetospheric research using EISCAT/ESR and CLUSTER

The four Cluster spacecraft offer a unique opportunity to study structure and dynamics in the magnetosphere and we discuss four general ways in which ground-based remote-sensing observations of the ionosphere can be used to support the in-situ measurements. The ionosphere over the Svalbard islands will be studied in particular detail, not only by the ESR and EISCAT incoherent scatter radars, but also by optical instruments, magnetometers, imaging riometers and the CUTLASS bistatic HF radar. We present an on-line procedure to plan coordinated measurements by the Cluster spacecraft with these combined ground-based systems. We illustrate the philosophy of the method, using two important examples of the many possible configurations between the Cluster satellites and the ground-based instruments

Recommendations for Next‐Generation Ground Magnetic Perturbation Validation

Data‐model validation of ground magnetic perturbation forecasts, specifically of the time rate of change of surface magnetic field, dB/dt, is a critical task for model development and for mitigation of geomagnetically induced current effects. While a current, community‐accepted standard for dB/dt validation exists (Pulkkinen et al., 2013), it has several limitations that prevent more complete understanding of model capability. This work presents recommendations from the International Forum for Space Weather Capabilities Assessment Ground Magnetic Perturbation Working Team for creating a next‐generation validation suite. Four recommendations are made to address the existing suite: greatly expand the number of ground observatories used, expand the number of events included in the suite from six to eight, generate metrics as a function of magnetic local time, and generate metrics as a function of activity type. For each of these, implementation details are explored. Limitations and future considerations are also discussed.Plain Language SummarySpace weather forecast models of magnetic field perturbations are important for protecting the power grid and other vulnerable infrastructure. These models must be validated by comparing their predictions to observations. This paper makes recommendations for how future models should be validated in order to best test their capabilities.Key PointsWe present a new validation suite for models of ground magnetic perturbations, dB/dt, of interest for geomagnetically induced currentsThe existing standard remains useful but provides limited information, so an expanded set of metrics is defined hereThis work is a result of the International Forum for Space Weather Capabilities Assessment and represents a new community consensusPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/147786/1/swe20777_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/147786/2/swe20777.pd

EISCAT observations of plasma convection and the high-latitude, winter F-region during substorm activity

A 24 h period of observations by the EISCAT radar and other ground-based instrumentation is used to study the role of plasma convection in determining the morphology of the high-latitude F-region during winter. It is suggested that, in the afternoon sector of the polar convection pattern, rapid zonal (westward) flows caused low F-region electron densities due to an extension of the mid-latitude trough far into the sunlit hemisphere. Low densities on the dawn side prior to 0600 UT may also have been due to a trough-like feature. Although the generation mechanism is unclear, the trough may be the fossil remnant of a substorm. Around midnight, high F-region densities were seen, probably due to plasma flow emerging from the cap through soft particle precipitation in the auroral oval. Two substorms occurred at times when the radar was south of the auroral oval. Both caused enhanced convection speeds, a swing to equatorward flow, enhanced E-region densities and a depleted F-region. The first was seen as a Westward Travelling Surge, and the swing to purely southward flow which followed the surge front did not return to westward flows until 80–110 min later. The Harang discontinuity was observed co-rotating eastwards between the substorms, 65 ± 30 min before the separatrix between the dawn and dusk convection cells

Ground-based observations of an onset of localized field-aligned currents during auroral breakup around magnetic midnight

The substorm on 2 March 1978 was selected for study as a relatively weak substorm, starting at about local magnetic midnight, that could be observed with instruments in Northern Scandinavia. The analysis is based on a comparative study of data from the IMS magnetometer network, all-sky cameras, pulsation magnetometers, and riometers in the Scandinavian area. In addition other data are used to support the results, e.g., a photograph from the DMSP-F2 satellite, showing the auroral situation over Scandinavia, and further west, immediately after the substorm onset. The substorm was preceded by a weak activation of aurora and magnetic disturbance about 3 min before the onset. After a fading that lasted for 20 s and could be observed only in optical aurora, the substorm onset led to a strong brightening of the aurora, an enhancement of the westward electrojet, a sudden rise in the ionospheric D-layer absorption, and Pi B type pulsations. Immediately after the onset, the ground magnetic data suggest the appearence of a pair of oppositely directed, localized, field-aligned currents (FACs). The main development of the signatures of the downward FAC was clearly delayed by about 3 min. There were significant correlations between the magnetic signatures of the two FACs and different features and spectra of the optical aurora, both in time and location. The observed Pi B type pulsations lasted as long as a growth in the local onset-connected FACs could be inferred. Within the first three minutes the localized three dimensional current system developed into a more sheet-like configuration. An expansion to the west, possibly accompanied by a westward travelling surge, was traced with riometers and magnetometers on Iceland and Greenland.           ARK: https://n2t.net/ark:/88439/y084828 Permalink: https://geophysicsjournal.com/article/208 &nbsp

Pi2 magnetic pulsations, auroral break-ups, and the substorm current wedge: A case study

The two-dimensional distribution of the characteristics of Pi2 magnetic pulsations observed by the Scandinavian Magnetometer Array (SMA) during the passage of a westward travelling surge on 11 November 1976 and during three sucessive auroral break-ups around magnetic midnight on 15 February 1977 have been studied in relation to the position of active aurora and the break-up current system. On both days the greatest Pi2 amplitudes were collocated with the region where the brightest auroras were observed. The sense of polarization of the horizontal disturbance vectors changed along longitudinal and meridional lines. The two-dimensional equivalent current system of the Pi2 pulsations resembled a circular current vortex around the location of the localized upward field-aligned currents and changed its direction from counterclockwise to clockwise and back to counterclockwise again within one Pi2 cycle. Our observations indicate that the generation of Pi2 pulsations is not directly connected to periodic fluctuations of the complete current system at substorm onset, but that the upward directed field-aligned currents at the western edge of this system play the most important role for the Pi2 generation.           ARK: https://n2t.net/ark:/88439/y071359 Permalink: https://geophysicsjournal.com/article/167 &nbsp