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The Radio Receiver Instrument (RRI) on-board the Swarm-E satellite is used to determine the full polarisation state of transionospheric radio waves. Co-ordinated experiments between ground transmitters and RRI have shown that the detected radio waves can have ellipticity that varies from linearly to circularly polarised when observed poleward of the transmitter at low elevations. Circular polarisation states are expected for waves propagating traverse to the local geometric field; however, these circular states were observed over a much wider range of aspect angles than expected. The present study compares the results of radio transmissions from the Saskatoon SuperDARN radar with a transionospheric radio wave model to estimate the relative strengths of received O- and X-mode waves along the satellite track. At selected low elevations, the X-mode of the radio wave dominates over the O-mode, resulting in a circular ellipticity, although the propagation is not transverse to the magnetic field. This work presents new ways to utilize ellipticity polarisation observations of radio waves to better understand the structure of the ionosphere, complementing Faraday rotation observations which have been extensively used.

Swarm-E carries the e-POP payload, which consists of eight scientific instruments. The Radio Receiver Instrument (RRI) on e-POP may be used to detect density structures that modify the characteristics of transionospheric HF radio waves from ground-based transmitters. RRI has a cross-dipole antenna designed to determine the polarisation characteristics of the incident radio waves. Joint experiments with other instruments, IRM (Imaging and Rapid-scanning ion Mass spectrometer) and MGF (Fluxgate Magnetometer), complement RRI for better understanding of the local ionosphere conditions and integrated conditions along the path between a ground-based transmitter and Swarm-E. Under optimum conditions, the RRI determines the full polarisation characteristics. This presentation discusses past and future contributions to ionospheric science of the Swarm constellation.

We present the first space-borne observation of optical emissions of both neutral and ionized argon atoms resulting from a radio-frequency glow discharge (RF-GD) from a sounding rocket payload. The Observations of Electric-field Distributions in the Ionospheric Plasma — a Unique Strategy-C (OEDIPUS-C) payload was designed to separate into two sub-payloads on its up-leg. This separation permitted a number of two-point measurements, including those on radio wave propagation from the active dipole antennas on the upper sub-payload to the synchronized receiving dipoles on the lower sub-payload. A white-light video camera on the lower sub-payload recorded strong luminosity around the active dipoles during the first 15 s after sub-payload separation, when argon gas jets were providing propulsion to separate the two sub-payloads. Parts of the ejected argon appeared as a glowing volume where the large radio-frequency (RF) fields from the two active dipoles excited the optical emission, as the sub-payload separation increased from 2 to 55 m. The shape and intensity of the luminosity were well repeated as a function of the swept frequency (0.025–8.000 MHz), but their frequency dependences were distinctly different from those of sounder-accelerated electrons measured onboard, and deduced to result from the nonlinearity of the glow discharge. The observation is to our knowledge the first of its kind, and is interpreted in terms of a RF-GD energized by the strong near electric fields of the transmitting dipoles.

Variations in ionospheric electron density, so-called irregularities, produce rapid fluctuations on propagating communication and navigation signals, which can be severe near the magnetic equator and in the polar regions. This may result in positioning error. Due to sparse sampling, our knowledge of the vertical distribution of small-scale irregularities is limited. In this study, we examine the vertical distribution of multi-scale scintillation-inducing irregularities in the low-latitude ionosphere. In four sets of novel experiments, we sampled altitudes from 330-1280 km in the 18-24 MLT sector using the Swarm Echo GAP-O GPS receiver with its antenna oriented toward zenith. In order to identify multi-scale irregularities both above and at the satellite’s position, we utilize high-sample-rate GAP-O amplitude and phase measurements along with a measurement of net current onto the surface of the IRM sensor on board, which serves as a proxy for density variations. We find that amplitude scintillations on the GPS signal coincide with strong in-situ small-scale density irregularities in 74% of cases, and above 500 km of altitude in all but one instance. In addition, we show that large-scale ionospheric disturbances occur predominantly below 500 km, and down to the 330 km perigee of Swarm Echo in the 18-21 MLT sector. In contrast, small-scale variations on total electron content (TEC) are detected at all MLTs between 18 MLT and magnetic midnight and at all altitudes sampled in this experiment. However, they are more frequent in the 22-24 MLT range.

Whistler-mode chorus waves are critical for driving resonant scattering and loss of radiation belt relativistic electrons into the atmosphere. The resonant energies of electrons scattered by chorus waves increase at increasingly higher magnetic latitudes. Propagation of chorus waves to middle and high latitudes is hampered by wave divergence and Landau damping but is promoted otherwise if ducted by density irregularities. Although ducting theories have been proposed since the 1960’s, no conjugate observation of ducted chorus propagation from the equatorial magnetosphere to the ionosphere has been observed so far. Here we provide such an observation, for the first time, using conjugate spacecraft measurements. Ducted chorus waves maintain significant wave power upon reaching the ionosphere, which is confirmed by ray tracing simulations. Our results suggest that ducted chorus waves may be an important driver for relativistic electron precipitation.

This work presents a statistical study between satellite observed very low frequency (VLF) events and earthquakes. We have observed strong VLF turbulences under geomagnetic quiet conditions, but during cascading earthquakes, implying the possibility of a seismic – ionospheric connection, although the exact connection mechanism is yet to be identified.

Ionospheric outflow has been shown to be a dominant ion source of Earth's magnetosphere. However, most studies in the literature are about ionospheric outflow injected into the nightside magnetosph ...

We have developed a model that simulates the power density profile of the Saskatoon Super Dual Auroral Radar Network (SuperDARN) radar at ionospheric altitudes. The model uses ray tracing software ...

On behalf of the journal, AGU, and the scientific community, the editors would like to sincerely thank those who reviewed the manuscripts for Geophysical Research Letters in 2020. The hours reading and commenting on manuscripts not only improve the manuscripts but also increase the scientific rigor of future research in the field. We particularly appreciate the timely reviews in light of the demands imposed by the rapid review process at Geophysical Research Letters. The COVID pandemic imposed additional stresses on the review process, as many reviewers had to juggle increased family commitments, hours of online meetings, remote work and instruction, lack of physical access to library resources, and other hardships to maintain the quality and timeliness of their reviews. Although we witnessed an increase in the number of submissions, the average number of days to complete a review increased by less than one day!! That says a lot about the diligence of our reviewers. We deeply appreciate their contributions in these challenging times. With the advent of AGU's data policy, many reviewers have also helped immensely to evaluate the accessibility and availability of data, and many have provided insightful comments that helped to improve the data presentation and quality. We greatly appreciate the assistance of the reviewers in advancing open science, which is a key objective of AGU's data policy. Individuals in italics provided three or more reviews for Geophysical Research Letters during the year. In total, 5,177 referees contributed to 8,786 individual reviews. Thank you again. We look forward to the coming year of exciting advances in the field and communicating those advances to our community and to the broader public.

One of the primary mechanisms of loss of Earth's atmosphere is the persistent “cold” ( urn:x-wiley:jgra:media:jgra56068:jgra56068-math-0001 20 eV) ion outflow that has been observed in the magnetospheric lobes over large volumes with dimensions of order several Earth radii. As the main source of this cold ion outflow, the polar cap F region ionosphere and conditions within it have a disproportionate influence on these magnetospheric regions. Using 15 years of measurements of plasma density Ne made by the Swarm spacecraft constellation and the Challenging Mini Satellite Payload (CHAMP) spacecraft within the F region of the polar cap above 80° Apex magnetic latitude, we report evidence of several types of seasonal asymmetries in polar cap Ne. Among these, the transition between “winter‐like” and “summer‐like” median polar cap Ne occurs 1 week prior to local spring equinox in the Northern Hemisphere (NH) and 1 week after local spring equinox in the Southern Hemisphere (SH). Thus, the median SH polar cap Ne lags the median NH polar cap Ne by approximately 2 weeks with respect to hemispherically local spring and fall equinox. From interhemispheric comparison of statistical distributions of polar cap plasma density around each equinox and solstice, we find that distributions in the SH are often flatter (i.e., less skewed and kurtotic) than those in the NH. Perhaps of most significance to cold ion outflow, we find no evidence of an F region plasma density counterpart to a previously reported hemispheric asymmetry whereby cold plasma density is higher in the NH magnetospheric lobe than in the SH lobe. Plain Language Summary The Earth's magnetic poles are not perfectly aligned with the Earth's geographic poles, and the degree of misalignment is greater in the Southern Hemisphere. Furthermore, as a result of the Earth's elliptical orbit around the Sun, summer and fall in the Northern Hemisphere together are approximately 1 week longer than summer and fall in the Southern Hemisphere, because the Earth is very slightly closer to the Sun around December solstice (summer in the Southern Hemisphere). These seasonal asymmetries, together with the asymmetric displacement of the Earth's magnetic poles relative to the geographic poles, suggest that the plasma density in the topside ionosphere's geomagnetic polar regions may also be subject to seasonal and hemispheric asymmetries. The polar regions are the primary site of loss of the Earth's atmosphere via so‐called ion outflow processes that, over geological time scales, are believed to lead to loss of the Earth's atmosphere. Using 15 years of plasma density measurements made by four different satellites to statistically study the plasma density of each hemisphere's geomagnetic polar cap ionosphere in the altitude range 350–520 km, we find that the polar cap ionosphere at these altitudes exhibits a variety of seasonal and hemispheric asymmetries. publishedVersion

On behalf of the journal, AGU, and the scientific community, the editors would like to sincerely thank those who reviewed the manuscripts for Geophysical Research Letters in 2019. The hours reading and commenting on manuscripts not only improve the manuscripts but also increase the scientific rigor of future research in the field. We particularly appreciate the timely reviews in light of the demands imposed by the rapid review process at Geophysical Research Letters. With the revival of the “major revisions” decisions, we appreciate the reviewers' efforts on multiple versions of some manuscripts. With the advent of AGU's data policy, many reviewers have helped immensely to evaluate the accessibility and availability of data associated with the papers they have reviewed, and many have provided insightful comments that helped to improve the data presentation and quality. We greatly appreciate the assistance of the reviewers in advancing open science, which is a key objective of AGU's data policy. Many of those listed below went beyond and reviewed three or more manuscripts for our journal, and those are indicated in italics.

The CASSIOPE Enhanced Polar Outflow Probe (e-POP) was originally envisioned as a low-cost, short-lifetime (18-month) small-satellite mission for investigating polar ion outflows and related magnetosphere-ionosphere coupling phenomena. However, e-POP is currently in its seventh year of continuing operation, as an addition to and as the fourth component of the Swarm constellation of satellites, under the European Space Agency Third Party Mission Programme.Since 2017, the increased operation duty-cycle of e-POP has enabled the routine extension of its science operations to its full altitude range and to all latitudes, and made possible several new studies of important mid- and low-latitude topside ionospheric phenomena. In addition, the integrated e-POP and Swarm operation takes advantage of the synergy between the orbit characteristics and unique instrument capabilities between e-POP and Swarm, to enable or enhance a host of coordinated studies of magnetosphere-ionosphere coupling: including the Earth’s magnetic field and related current systems, auroral and upper atmospheric dynamics, and ionosphere-thermosphere and ionosphere-plasmasphere coupling processes. We present an overview of these new studies, focusing on their results on the effects of space weather in the ionosphere and upper atmosphere such as anomalous satellite orbit drag and ionospheric scintillation.

The polar cap ionosphere (here defined as the region above 80° magnetic latitude) is the primary source region of cold plasma outflows observed in the magnetosphere. The two factors controlling cold plasma outflows are the availability of plasma in the polar cap ionosphere, and transport from the ionosphere to the magnetosphere. Some statistical studies have indicated that the former of these two factors, availability of cold plasma, is the limiting factor. We use 15 years of electron density measurements made by Swarm and CHAMP spacecraft, corrected for variations in observation altitude and solar activity, to investigate how variations in solar wind driving and local hemispheric season affect the polar cap ionosphere electron density Ne. We show that the dependence of Ne on the By component of the interplanetary magnetic field is apparently antisymmetric in the two hemispheres, that Nestatistically decreases with decreasing Dst index (i.e., increasing geomagnetic activity) and that Ne is apparently insensitive to the AE index. We also show that Ne distributions around March and September equinoxes display weak evidence of hemispheric asymmetry. We show that during local summer, observed Ne distributions under high solar wind driving conditions are relatively lower than Ne distributions under low solar wind driving conditions. During local winter the reverse is true, with Ne distributions under low solar wind driving conditions being relatively lower than Ne distributions under high solar wind driving conditions. Thus solar wind driving and seasonal effects may apparently both constructively and destructively interfere. Altitude variation in Swarm and CHAMP Nemeasurements is accounted for via an empirical scale height derived from 1687 conjunctions between Swarm B and either Swarm A or Swarm C during 2013–2019. The approximately linear dependence of Ne on F10.7 measurements is also accounted for. Swarm Ne measurements are additionally corrected using the Lomidze et al. (2018) calibrations.

Cold (eV) ions of ionospheric origin dominate the number density of most of the volume of the magnetosphere during most of the time. Supersonic flows of cold positive ions are common and can cause a negatively charged wake behind a positively charged spacecraft. The associated induced electric field can be observed and can be used to study the cold ions. We present observations from the Cluster and MMS spacecraft showing how a charged satellite, and also individual charged wire booms of an electric field instrument, can be used to investigate cold ion populations. Ionospheric ions affect large scales, including the Alfvén velocity and thus energy transport with waves and the magnetic reconnection rate. These ions also affect small-scale kinetic plasma physics, including the Hall physics and wave instabilities associated with magnetic reconnection. Concerning large scales, we summarize observations from several spacecraft and show that a typical total outflow rate of ionospheric ions is 1026 ions/s and that many of these ions stay cold also after a long time in the magnetosphere. Concerning small scales, we show examples of how cold ions modify the Hall physics of thin current sheets, including magnetic reconnection separatrices. On small kinetic scales the cold ions introduce a new length-scale, a gyro radius between the gyro radii of hot (keV) ions and electrons. The Hall currents carried by electrons can be partially cancelled by the cold ions when electrons and the magnetized cold ions ExB drift together. Also, close to a reconnection X-line an additional diffusion region can be formed (regions associated with hot and cold ions, and with electrons, total of three).

Heavy (O+) ion energization and field-aligned motion in and near the ionosphere are still not well understood. Based on observations from the CASSIOPE Enhanced Polar Outflow Probe (e-POP) at altitudes between 325 km and 730 km over one year, we present a statistical study (24 events) of ion heating and its relation to field-aligned ion bulk flow velocity, low-frequency waves and field-aligned currents (FACs). The ion temperature and field-aligned bulk flow velocity are derived from 2-D ion velocity distribution functions measured by the suprathermal electron imager (SEI) instrument. Consistent ion heating and flow velocity characteristics are observed from both the SEI and the rapid-scanning ion mass spectrometer (IRM) instruments. We find that transverse O+ ion heating in the ionosphere can be intense (up to 4.5 eV), confined to very narrow regions (∼ 2 km across B), is more likely to occur in the downward current region, and is associated with broadband extremely low frequency (BBELF) waves. These waves are interpreted as linearly polarized perpendicular to the magnetic field. The amount of ion heating cannot be explained by frictional heating, and the correlation of ion heating with BBELF waves suggest that significant wave-ion heating is occurring and even dominating at altitudes as low as 350 km, a boundary that is lower than previously reported. Surprisingly, the majority of these heating events (17 out 24) are associated with core ion downflows rather than upflows. This may be explained by a downward-pointing electric field in the low-altitude return current region.

This paper presents validation of ionospheric Global Positioning System (GPS) radio occultation measurements of the GPS Attitude, Positioning, and Profiling Experiment occultation receiver (GAP-O). GAP is one of eight instruments comprising the Enhanced Polar Outflow Probe (e-POP) instrument suite on board the Cascade Smallsat and Ionospheric Polar Explorer (CASSIOPE) satellite. One of the main error sources for certain GAP-O data products is the receiver differential code bias (rDCB). A minimization of standard deviations (MSD) technique has shown the most promise for rDCB estimation, with estimates ranging primarily from −40 to −28 total electron content units (TECU = 1016 el m−2; 21.6 to 15.1 ns), including a long-term decrease in rDCB magnitude and variability over the first 3 years of instrument operation. In application of the MSD method, the sensitivity of bias estimates to ionospheric shell height are as large as 4.5 TECU per 100 km. MSD calculations also agree well with the “assumption of zero topside TEC” method for rDCB estimate at satellite apogee. Bias-corrected topside TEC of GAP-O was validated by statistical comparison with topside TEC obtained from ground-based GPS TEC and ionosonde measurements. Although GAP-O and ground-based topside TEC had similar variability, GAP-O consistently underestimated the ground-derived topside TEC by up to 7 TECU. Ionospheric electron density profiles obtained from Abel inversion of GAP-O occultation TEC showed good agreement with F region densities of ground-based incoherent scatter radar measurements. Comparison of GAP-O and ionosonde measurements revealed correlation coefficients of 0.78 and 0.79, for peak F region density and altitude, respectively.

Author(s): Rajaram, H; Diffenbaugh, N; Camargo, S; Cardenas, MB; Carey, R; Cobb, K; Cory, R; Cronin, M; Dombard, A; Donohue, K; Flesch, L; Giannini, A; Hayes, G; Hogg, A; Ilyina, T; Ivanov, V; Jacobsen, S; Korte, M; Lu, G; Morlighem, M; Magnusdottir, G; Newman, A; Opher, M; Passalacqua, P; Patricola, C; Ritsema, J; Sprintall, J; Su, H; Thornton, J; Williams, P; Yau, A | Abstract: On behalf of the journal, AGU, and the scientific community, the Editors would like to sincerely thank those who reviewed manuscripts for Geophysical Research Letters in 2018. The hours reading and commenting on manuscripts not only improves the manuscripts but also increases the scientific rigor of future research in the field. We particularly appreciate the timely reviews, in light of the demands imposed by the rapid review process at Geophysical Research Letters. With the revival of the “major revisions” decisions, we appreciate the reviewers' efforts on multiple versions of some manuscripts. Many of those listed below went beyond and reviewed three or more manuscripts for our journal, and those are indicated in italics. In total, 4,484 referees contributed to 7,557 individual reviews in journal. Thank you again. We look forward to the coming year of exciting advances in the field and communicating those advances to our community and to the broader public.

Swarm-E (formerly CASSIOPE Enhanced Polar Outflow Probe, e-POP) was launched in September 2013 into an elliptical polar orbit (325–1500 km, 81° inclination), and is currently in its sixth year of operation (and second year of operation as an integral part of the Swarm constellation). One of its science thrusts is to investigate the microphysics of radio-wave propagation and wave-plasma interaction processes in the topside ionosphere [1], using its trio of radio science instruments to perform a variety of unique active experiments and passive observations in coordination with ground facilities and other spacecraft.

The e-POP/Swarm-E Radio Receiver Instrument (RRI) on CASSIOPE detects very-low-frequency (VLF) broadcasts from national naval sources over the whole world. The propagation in question is the whistler mode whose dispersion relation allows a number of unique phenomena to be examined. Because the whistler mode is the only ionospheric magnetoionic mode propagating at VLF, the crossed 6-m dipoles feeding the RRI permit the whistler-mode elliptical electric fields to be measured. This allows the direction of arrival (DOA) of propagation at the satellite to be determined. Examples of wave reception from NWC (Australia), NLK (USA), NAA (USA), and DHO38 (Germany) show features of whistler-mode propagation in the topside ionosphere.

We present the design and principle of operation of the imaging ion mass and velocity analyzer on the Enhanced Polar Outflow Probe (e-POP), which measures low-energy (1–90 eV/e) ion mass composition (1–40 AMU/e) and velocity distributions using a hemispherical electrostatic analyzer (HEA), a time-of-flight (TOF) gate, and a pair of toroidal electrostatic deflectors (TED). The HEA and TOF gate measure the energy-per-charge and azimuth of each detected ion and the ion transit time inside the analyzer, respectively, providing the 2-D velocity distribution of each major ionospheric ion species and resolving the minor ion species under favorable conditions. The TED are in front of the TOF gate and optionally sample ions at different elevation angles up to ±60°, for measurement of 3-D velocity distribution. We present examples of observation data to illustrate the measurement capability of the analyzer, and show the occurrence of enhanced densities of heavy “minor” O++, N+, and molecular ions and intermittent, high-velocity (a few km/s) upward and downward flowing H+ ions in localized regions of the quiet time topside high-latitude ionosphere.

We present measurements the Enhanced Polar Outflow Probe (e-POP) onboard the CAScade, Smallsat and IOnospheric Polar Explorer (CASSIOPE) performed during the August 21, 2017 eclipse. CASSIOPE transited across the path of totality of the eclipse within 10 minutes after totality over Idaho. The spacecraft was moving along a north-south track at an altitude of approximately 650 km. In this presentation, we outline results from 2 of e-POP's 8 instruments: the Radio Receiver Instrument (RRI), and the GPS Attitude, Position and profiling experiment – Occultation (GAP-O) instrument.

We report the first satellite imaging of auroral pulsations by the Fast Auroral Imager (FAI) on board the Enhanced Polar Outflow Probe (e-POP) satellite. The near-infrared camera of FAI is capable of providing up to two auroral images per second, ideal for investigation of pulsating auroras. The auroral pulsations were observed within the auroral bulge formed during a substorm interval on 19 February 2014. This first satellite view of these pulsations from FAI reveals that (1) several pulsating auroral channels (PACs) occur within the auroral bulge, (2) periods of the intensity pulsations span over one decade within the auroral bulge, and (3) there is no apparent trend of longer pulsation periods associated with higher latitudes for these PACs. Although PACs resemble in some respect stable pulsating auroras reported previously, they have several important differences in characteristics.

Electron conic distributions have angular distributions with peak fluxes well separated from the field aligned-direction. They have previously been reported at Earth on auroral field lines and at the Moon and Mars on closed crustal magnetic field lines. Here we report observations of electron conics at Earth on closed magnetic field lines well removed from the aurora. We show how these distributions could be produced without plasma wave interactions when magnetic field lines are illuminated by solar ionizing radiation at relatively high altitudes in the ionosphere. Examination of previous reports of electron conic distributions observed in planetary atmospheres show that there are a variety of physical mechanisms that can lead to their formation, not all of which require wave-particle interactions.

We present the initial scientific results from the CASSIOPE small satellite mission, which was successfully launched on September 29, 2013 into an elliptic polar orbit of 325×1500 km at 81° inclination. The CASSIOPE spacecraft uses the Canadian small satellite bus to carry the Enhanced Polar Outflow Probe (e-POP) scientific (space weather research) payload and the Cascade communications technology demonstration payload into orbit. The e-POP payload is comprised of a suite of eight high-resolution plasma, magnetic field, radio, and optical instruments designed for in-situ observations in the topside polar ionosphere at the highest-possible resolution. The payload utilizes the advanced data storage and telemetry downlink capability of Cascade to meet its large data downlink bandwidth requirements – and to help demonstrate the capabilities of Cascade in the process. We present preliminary results from the first several months of CASSIOPE mission operation, to demonstrate the performance of both payloads, and the scientific capabilities of the e-POP mission in coordination with other observing facilities.

This paper presents validation of ionospheric Global Positioning System (GPS) radio occultation (RO) measurements of the GPS Attitude, Positioning, and Profiling Experiment occultation receiver (GAP-O). The primary source of uncertainty impacting GAP-O data products is the receiver differential code bias (rDCB). A minimization of standard deviations (MSD) technique for rDCB estimate has shown the most promise, and resulted in estimates ranging from −39 to −29 TECU, including a steady, long term decrease in rDCB magnitude. MSD estimates agree well with the “assumption of zero topside TEC” method at satellite apogee in the polar cap. Bias-corrected topside TEC of GAP-O was validated by statistical comparison with topside TEC obtained from ground-based GPS TEC and ionosonde measurements. GAP-O and ground-based topside TEC had similar variability, however GAP-O consistently underestimated the ground-derived topside TEC by up to 8 TECU. Ionospheric electron density profiles obtained from Abel inversion of GAP-O occultation TEC showed consistently good agreement with F-region densities of incoherent scatter radar measurements, however RO-derived E-region densities were not as reliable at high latitudes.

Highlights from AGU’s joint meeting with the Japan Geophysical Union.

First results from the Juno mission shed new light on Jupiter’s atmosphere, gravity, magnetic field, aurora, history, and more.

The role of electron precipitation in the auroral zone in driving thermal O+ upwelling is explored by comparison of observations and model results. Previous reports have shown how the ambiguities of such an assessment can be reduced when the problem is addressed in dynamic boundary-related coordinates. Upwelling ion data from the Defense Meteorological Satellite Program (DMSP) satellites are compared using a modeling framework based on the Field Line Interhemispheric Plasma (FLIP) ionospheric model. We focus on geomagnetically quiet intervals, that is, nonstorm times with Dst > −50 nT. We find that low-energy (

The GIOS program has conducted HF scatter and ionosphere propagation tests to show that a single HF transmitter can illuminate greater than 1000 km of ocean surface and scatter waves to single satellite in low earth orbit. The receiver in orbit samples the HF illuminated area to measure Brag scatter from the ocean with signals that pass through the ionosphere. The Doppler shifts and group delays map to specific points on the ocean surface at each point in the satellite orbit. Using the theory of ocean scatter, both coherent (specular) and incoherent (Bragg) scatter components at HF frequency provides bistatic sampling of global ocean surface. Data based models of the waveheight spectrum have been used in simulations to validate this concept. Experimental tests with the HF transmitter of ROTHR/VA and space based receiver of ePOP/RRI have provided data that were collected in April 2015. Actual interpretation in of the satellite measurements in terms of ocean surface parameters is in progress. A practical GIOS system will require measurements from a spacecraft flying below the ionosphere. For this purpose, the Naval Research Laboratory has designed a satellite called CARINA which will orbit the earth at an altitude of 200 to 250 km for 60 days.

Understanding magnetic reconnection is important in the context of Sun-Earth Connection, because of the resulting exchange of mass and energy, and the large amount of energy involved.

This paper reviews the state of knowledge concerning the source of magnetospheric plasma at Earth. Source of plasma, its acceleration and transport throughout the system, its consequences on system dynamics, and its loss are all discussed. Both observational and modeling advances since the last time this subject was covered in detail (Hultqvist et al., Magnetospheric Plasma Sources and Losses, 1999) are addressed.