PFISR Experiment, Data Reduction, and Analysis

PFISR data processing descriptio

On the generation/decay of the storm‐enhanced density plumes: Role of the convection flow and field‐aligned ion flow

Storm‐enhanced density (SED) plumes are prominent ionospheric electron density increases at the dayside middle and high latitudes. The generation and decay mechanisms of the plumes are still not clear. We present observations of SED plumes during six storms between 2010 and 2013 and comprehensively analyze the associated ionospheric parameters within the plumes, including vertical ion flow, field‐aligned ion flow and flux, plasma temperature, and field‐aligned currents, obtained from multiple instruments, including GPS total electron content (TEC), Poker Flat Incoherent Scatter Radar (PFISR), Super Dual Auroral Radar Network, and Active Magnetosphere and Planetary Electrodynamics Response Experiment. The TEC increase within the SED plumes at the PFISR site can be 1.4–5.5 times their quiet time value. The plumes are usually associated with northwestward E  ×  B flows ranging from a couple of hundred m s −1 to > 1 km s −1 . Upward vertical flows due to the projection of these E  ×  B drifts are mainly responsible for lifting the plasma in sunlit regions to higher altitude and thus leading to plume density enhancement. The upward vertical flows near the poleward part of the plumes are more persistent, while those near the equatorward part are more patchy. In addition, the plumes can be collocated with either upward or downward field‐aligned currents (FACs) but are usually observed equatorward of the peak of the Region 1 upward FAC, suggesting that the northwestward flows collocated with plumes can be either subauroral or auroral flows. Furthermore, during the decay phase of the plume, large downward ion flows, as large as ~200 m s −1 , and downward fluxes, as large as 10 14  m −2  s −1 , are often observed within the plumes. In our study of six storms, enhanced ambipolar diffusion due to an elevated pressure gradient is able to explain two of the four large downward flow/flux cases, but this mechanism is not sufficient for the other two cases where the flows are of larger magnitude. For the latter two cases, enhanced poleward thermospheric wind is suggested to be another mechanism for pushing the plasma downward along the field line. These downward flows should be an important mechanism for the decay of the SED plumes. Key Points Vertical plasma lifting leads to density increase during plume generation phase Large downward field‐aligned ion flow/flux seen during plume decay phase Complex‐induced plasma drifts seen indicating plumes' highly dynamic naturePeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/109661/1/StormB_tec_20121113.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/109661/2/QuietTimeF_tec_20100821.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/109661/3/StormD_tec_20120423.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/109661/4/QuietTimeC_tec_20120928.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/109661/5/SupplementaryMaterial_Figure3_quiet.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/109661/6/QuietTimeE_tec_20110203.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/109661/7/StormC_tec_20120930.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/109661/8/StormA_tec_20130423.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/109661/9/StormF_tec_20100803.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/109661/10/jgra51348.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/109661/11/SupplementaryMaterial_Figure4_quiet.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/109661/12/QuietTimeA_tec_20130421.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/109661/13/QuietTimeD_tec_20120429.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/109661/14/QuietTimeB_tec_20121109.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/109661/15/StormE_tec_20110204.pd

Multi‐instrument observations of SED during 24–25 October 2011 storm: Implications for SED formation processes

We present multiple instrument observations of a storm‐enhanced density (SED) during the 24–25 October 2011 intense geomagnetic storm. Formation and the subsequent evolution of the SED and the midlatitude trough are revealed by global GPS vertical total electron content maps. In addition, we present high time resolution Poker Flat Incoherent Scatter Radar (PFISR) observations of ionospheric profiles within the SED. We divided the SED observed by PFISR into two parts. Both parts are characterized by elevated ionospheric peak height ( h m F 2 ) and total electron content, compared to quiet time values. However, the two parts of the SED have different characteristics in the electron temperature ( T e ), the F region peak density ( N m F 2 ), and convection flows. The first part of the SED is associated with enhanced T e in the lower F region and reduced T e in the upper F region and is collocated with northward convection flows. The N m F 2 was lower than quiet time values. The second part of the SED is associated with significantly increased N m F 2 , elevated T e at all altitudes and is located near the equatorward boundary of large northwestward flows. Based on these observations, we suggest that the mechanisms responsible for the formation of the two parts of the SED may be different. The first part is due to equatorward expansion of the convection pattern and the projection of northward convection flows in the vertical direction, which lifts the ionospheric plasma to higher altitudes and thus reduces the loss rate of plasma recombination. The second part is more complicated. Besides equatorward expansion of the convection pattern and large upward flows, evidences of other mechanisms, including horizontal advection due to fast flows, energetic particle precipitation, and enhanced thermospheric wind in the topside ionosphere, are also present. Estimates show that contribution from precipitating energetic protons is at most ~10% of the total F region density. The thermospheric wind also plays a minor role in this case. Key Points SED formation during 24–25 October 2011 geomagnetic storm studied PFISR observations within the SED shown Electric field plays a major role in the formation of SED in this stormPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/102626/1/jgra50711.pd

Ionospheric ion temperature climate and upper atmospheric long-term cooling

It is now recognized that Earth's upper atmosphere is experiencing a long-term cooling over the past several solar cycles. The potential impact of the cooling on societal activities is significant, but a fundamental scientific question exists regarding the drivers of the cooling. New observations and analyses provide crucial advances in our knowledge of these important processes. We investigate ionospheric ion temperature climatology and long-term trends using up-to-date large and consistent ground-based data sets as measured by multiple incoherent scatter radars (ISRs). The very comprehensive view provided by these unique observations of the upper atmospheric thermal status allows us to address drivers of strong cooling previously observed by ISRs. We use observations from two high-latitude sites at Sondrestrom (invariant latitude 73.2°N) from 1990 to 2015 and Chatanika/Poker Flat (invariant latitude 65.9°N) over the span of 1976–2015 (with a gap from 1983 to 2006). Results are compared to conditions at the midlatitude Millstone Hill site (invariant latitude 52.8°N) from 1968 to 2015. The aggregate radar observations have very comparable and consistent altitude dependence of long-term trends. In particular, the lower F region (<275 km) exhibits dayside cooling trends that are significantly higher (−3 to −1 K/yr at 250 km) than anticipated from model predictions given the anthropogenic increase of greenhouse gases. Above 275 km, cooling trends continue to increase in magnitude but values are strongly dependent on magnetic latitude, suggesting the presence of significant downward influences from nonneutral atmospheric processes.National Science Foundation (U.S.) (Awards AGS-1042569 and AGS-1343056

PFISR observation of intense ion upflow fluxes associated with an SED during the 1 June 2013 geomagnetic storm

The Earth’s ionosphere plays an important role in supplying plasma into the magnetosphere through ion upflow/outflow, particularly during periods of strong solar wind driving. An intense ion upflow flux event during the 1 June 2013 storm has been studied using observations from multiple instruments. When the open‐closed field line boundary (OCB) moved into the Poker Flat incoherent scatter radar (PFISR) field of view, divergent ion fluxes were observed by PFISR with intense upflow fluxes reaching ~1.9 × 1014 m−2 s−1 at ~600 km altitude. Both ion and electron temperatures increased significantly within the ion upflow, and thus, this event has been classified as a type 2 upflow. We discuss factors contributing to the high electron density and intense ion upflow fluxes, including plasma temperature effect and preconditioning by storm‐enhanced density (SED). Our analysis shows that the significantly enhanced electron temperature due to soft electron precipitation in the cusp can reduce the dissociative recombination rate of molecular ions above ~400 km and contributed to the density increase. In addition, this intense ion upflow flux event is preconditioned by the lifted F region ionosphere due to northwestward convection flows in the SED plume. During this event, the OCB and cusp were detected by DMSP between 15 and 16 magnetic local times, unusually duskward. Results from a global magnetohydrodynamics simulation using the Space Weather Modeling Framework have been used to provide a global context for this event. This case study provides a more comprehensive mechanism for the generation of intense ion upflow fluxes observed in association with SEDs.Key PointsA more comprehensive mechanism for the generation of intense ion upflow fluxes observed in association with SEDs has been providedNorthwestward convection flows lift the F region ionosphere within SED and provide seed population for intense ion upflow fluxesSignificantly elevated electron temperature reduces recombination rate contributing to density increasePeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/136519/1/jgra53328.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/136519/2/jgra53328_am.pd

Electrodynamics of the high‐latitude trough: Its relationship with convection flows and field‐aligned currents

We present a detailed case study of the electrodynamics of a high‐latitude trough observed at ~ 12 UT (~1 MLT) on 8 March 2008 using multiple instruments, including incoherent scattering radar (ISR), GPS total electron content (TEC), magnetometers, and auroral imager. The electron density within the trough dropped as much as 80% within 6 minutes. This trough was collocated with a counterclockwise convection flow vortex, indicating divergent horizontal electric fields and currents. Together with a collocated dark area shown in auroral images, the observations provide strong evidence for an existence of downward field‐aligned currents (FACs) collocated with the high‐latitude trough. This is further supported by assimilative mapping of ionospheric electrodynamics results. In addition, the downward FACs formed at about the same time as a substorm onset and east of the Harang reversal, suggesting it is part of the substorm current wedge. It has long been a puzzle why this type of high‐latitude trough predominantly occurs just east of the Harang reversal in the postmidnight sector. We suggest that the high‐latitude trough is associated with the formation of downward FACs of the substorm current system, which usually occur just east of the Harang reversal. In addition, we find that the ionospheric electron temperature within the high latitude trough decreases in the F region while increasing in the E region. We discuss possible mechanisms responsible for the complex change in electron temperature, such as ion composition change and/or presence of downward FACs. Key Points Multi‐instrument study of the high‐latitude trough electrodynamics Trough is associated with anti‐clockwise flow vortex and substorm downward FACs Complex Te profile observed in the trough and due to downward FACsPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/98817/1/jgra50120.pd

IPSE, an abundant egg-secreted protein of the carcinogenic helminth Schistosoma haematobium, promotes proliferation of bladder cancer cells and angiogenesis

Background Schistosoma haematobium, the helminth causing urogenital schistosomiasis, is a known bladder carcinogen. Despite the causal link between S. haematobium and bladder cancer, the underlying mechanisms are poorly understood. S. haematobium oviposition in the bladder is associated with angiogenesis and urothelial hyperplasia. These changes may be pre-carcinogenic events in the bladder. We hypothesized that the Interleukin-4-inducing principle of Schistosoma mansoni eggs (IPSE), an S. haematobium egg-secreted “infiltrin” protein that enters host cell nuclei to alter cellular activity, is sufficient to induce angiogenesis and urothelial hyperplasia. Methods: Mouse bladders injected with S. haematobium eggs were analyzed via microscopy for angiogenesis and urothelial hyperplasia. Endothelial and urothelial cell lines were incubated with recombinant IPSE protein or an IPSE mutant protein that lacks the native nuclear localization sequence (NLS-) and proliferation measured using CFSE staining and real-time monitoring of cell growth. IPSE’s effects on urothelial cell cycle status was assayed through propidium iodide staining. Endothelial and urothelial cell uptake of fluorophore-labeled IPSE was measured. Findings: Injection of S. haematobium eggs into the bladder triggers angiogenesis, enhances leakiness of bladder blood vessels, and drives urothelial hyperplasia. Wild type IPSE, but not NLS-, increases proliferation of endothelial and urothelial cells and skews urothelial cells towards S phase. Finally, IPSE is internalized by both endothelial and urothelial cells. Interpretation: IPSE drives endothelial and urothelial proliferation, which may depend on internalization of the molecule. The urothelial effects of IPSE depend upon its NLS. Thus, IPSE is a candidate pro-carcinogenic molecule of S. haematobium. Summary Schistosoma haematobium acts as a bladder carcinogen through unclear mechanisms. The S. haematobium homolog of IPSE, a secreted schistosome egg immunomodulatory molecule, enhances angiogenesis and urothelial proliferation, hallmarks of pre-carcinogenesis, suggesting IPSE is a key pro-oncogenic molecule of S. haematobium

Thermospheric Gravity Wave Observations Over Alaska Using the Poker Flat Incoherent Scatter Radar

It is now well known that atmospheric gravity waves play important roles in the mesosphere lower thermosphere (MLT) region (~80 - 110 km) through momentum deposition [e.g. Fritts and Alexander, 2003]. Observational and modeling studies in the past decade have revealed the importance of these waves in the higher thermospheric region (~110 - 400 km) as they contribute significantly to changes in both winds and temperatures [e.g. Vadas and Fritts, 2005]. Although case studies have revealed their presence in the thermosphere [e.g. Nicolls and Heinselman, 2007], the distributions and variability of thermospheric gravity wave parameters are unknown. Recently, a four year collaborative observational effort utilizing an all-sky airglow imager, Rayleigh lidar, and the Poker Flat Incoherent Scatter Radar (PFISR) has been performed over interior Alaska to study a broad spectrum of gravity waves throughout the troposphere, mesosphere, and thermosphere. This presentation details the process of obtaining wave parameters from PFISR (based on a method developed by Nicolls and Heinselman, 2007) and presents preliminary wave period distributions for the winter season of 2010 - 2011. These distributions are compared to results obtained with a co-located mesospheric airglow imager

Thermospheric Gravity Wave Characteristics Obtained Using the Poker Flat Incoherent Scatter Radar

Recent observational and modeling studies have revealed the importance of gravity waves propagating into the thermospheric region (~110 - 400 km) as they contribute significantly to changes in both winds and temperatures [e.g. Vadas and Fritts, 2005]. The distributions and variability of these thermospheric gravity wave parameters are not yet known

24/7 Solar Minimum Polar Cap and Auroral Ion Temperature Observations

During the International Polar Year (IPY) two Incoherent Scatter Radars (ISRs) achieved close to 24/7 continuous observations. This presentation describes their data sets and specifically how they can provide the International Reference Ionosphere (IRI) a fiduciary E- and F-region ionosphere description for solar minimum conditions in both the auroral and polar cap regions. The ionospheric description being electron density, ion temperature and electron temperature profiles from as low as 90 km extending to several scale heights above the F-layer peak. The auroral location is Poker Flat in Alaska at 65.1 N latitude, 212.5 E longitude where the NSF s new Poker Flat Incoherent Scatter Radar (PFISR) is located. This location during solar minimum conditions is in the auroral region for most of the day but is at midlatitudes, equator ward of the cusp, for about 4-8 h per day dependent upon geomagnetic activity. In contrast the polar location is Svalbard, at 78.2 N latitude, 16.0 E longitude where the EISCAT Svalbard Radar (ESR) is located. For most of the day the ESR is in the Northern Polar Cap with a noon sector passage often through the dayside cusp. Of unique relevance to IRI is that these extended observations have enabled the ionospheric morphology to be distinguished between quiet and disturbed geomagnetic conditions. During the IPY year, 1 March 2007 - 29 February 2008, about 50 solar wind Corotating Interaction Regions (CIRs) impacted geospace. Each CIR has a two to five day geomagnetic disturbance that is observed in the ESR and PFISR observations. Hence, this data set also enables the quiet-background ionospheric climatology to be established as a function of season and local time. These two separate climatologies for the ion temperature at an altitude of 300 km are presented and compared with IRI ion temperatures. The IRI ion temperatures are about 200-300 K hotter than the observed values. However, the MSIS neutral temperature at 300 km compares favorably with the quiet-background in temperature, both in magnitude and climatology