Dawn–Dusk Asymmetries In The Coupled Solar Wind–Magnetosphere–Ionosphere System: A Review

Dawn–dusk asymmetries are ubiquitous features of the coupled solar-wind–magnetosphere–ionosphere system. During the last decades, increasing availability of satellite and ground-based measurements has made it possible to study these phenomena in more detail. Numerous publications have documented the existence of persistent asymmetries in processes, properties and topology of plasma structures in various regions of geospace. In this paper, we present a review of our present knowledge of some of the most pronounced dawn–dusk asymmetries. We focus on four key aspects: (1) the role of external influences such as the solar wind and its interaction with the Earth\u27s magnetosphere; (2) properties of the magnetosphere itself; (3) the role of the ionosphere and (4) feedback and coupling between regions. We have also identified potential inconsistencies and gaps in our understanding of dawn–dusk asymmetries in the Earth\u27s magnetosphere and ionosphere

Mini-conference on helicon plasma sources

The first two sessions of this mini-conference focused attention on two areas of helicon source research: The conditions for optimal helicon source performance and the origins of energetic electrons and ions in helicon sourceplasmas. The final mini-conference session reviewed novel applications of helicon sources, such as mixed plasma source systems and toroidal helicon sources. The session format was designed to stimulate debate and discussion, with considerable time available for extended discussion.E.E.S. and A.M.K. acknowledge support for this work from NSF award No. PHY- 0611571

Storm time equatorial magnetospheric ion temperature derived from TWINS ENA flux

The plasma sheet plays an integral role in the transport of energy from the magnetotail to the ring current. We present a comprehensive study of the equatorial magnetospheric ion temperatures derived from Two Wide‐angle Imaging Neutral‐atom Spectrometers (TWINS) energetic neutral atom (ENA) measurements during moderate to intense (Dstpeak < −60 nT) storm times between 2009 and 2015. The results are validated using ion temperature data derived from the Geotail low‐energy particle energy analyzer and the Los Alamos National Laboratory magnetospheric plasma analyzer. The ion temperatures are analyzed as a function of storm time, local time, and L shell. We perform a normalized superposed epoch analysis of 48 geomagnetic storms and examine the spatial and temporal evolution of the plasma as a function of storm phase. This analysis illustrates the spatial and temporal variation of the ions from the plasma sheet into the inner magnetosphere. We find that the ion temperature increases approaching the storm peak. This enhancement has the largest magnetic local time extent near 12 RE distance downtail.Key PointsWe derive and statistically examine storm time equatorial magnetospheric ion temperatures from TWINS ENA fluxThe TWINS ion temperature data are validated using Geotail and LANL ion temperature dataFor moderate to intense storms the widest (in MLT) peak in nightside ion temperature is found to exist near 12 REPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/137478/1/jgra53387.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/137478/2/jgra53387_am.pd

Statistical Storm Time Examination Of Mlt-Dependent Plasmapause Location Derived From Image Euv

The location of the outer edge of the plasmasphere (the plasmapause) as a function of geomagnetic storm time is identified and investigated statistically in regard to the solar wind driver. Imager for Magnetopause‐to‐Aurora Global Exploration (IMAGE) extreme ultraviolet (EUV) data are used to create an automated method that locates and extracts the plasmapause. The plasmapause extraction technique searches a set range of possible plasmasphere densities for a maximum gradient. The magnetic local time (MLT)‐dependent plasmapause results are compared to manual extraction results. The plasmapause results from 39 intense storms are examined along a normalized epoch storm timeline to determine the average plasmapause L shell as a function of MLT and storm time. The average extracted plasmapause L shell follows the expected storm time plasmapause behavior. The results show that during the main phase, the plasmapause moves earthward and a plasmaspheric drainage plume forms near dusk and across the dayside during strong convection. During the recovery phase, the plume rejoins the corotationally driven plasma while the average plasmapause location moves farther from the Earth. The results are also examined in terms of the solar wind driver. We find evidence that shows that the different categories of solar wind drivers result in different plasmaspheric configurations. During magnetic cloud‐driven events the plasmaspheric drainage plume appears at the start of the main phase. During sheath‐driven events the plume forms later but typically extends further in MLT.Key PointsDeveloped an automated procedure to extract plasmapause from IMAGE EUV imagesValidate and evaluate results using statistical analysis of 39 intense stormsShow that plasmasphere dynamics vary systematically with CME‐v‐CIR drivin

An emittance measurement system for a wide range of bunch charges

As a part of the emittance measurements planned for the FEL injector at the Thomas Jefferson National Accelerator Facility (Jefferson Lab), the authors have developed an emittance measurement system that covers the wide dynamic range of bunch charges necessary to fully characterize the high-DC-voltage photocathode gun. The measurements are carried out with a variant of the classical two-slit method using a slit to sample the beam in conjunction with a wire scanner to measure the transmitted beam profile. The use of commercial, ultra-low noise picoammeters makes it possible to cover the wide range of desired bunch charges, with the actual measurements made over the range of 0.25 pC to 125 pC. The entire system, including its integration into the EPICS control system, is discussed

Geomagnetic disturbance intensity dependence on the universal timing of the storm peak

The role of universal time (UT) dependence on storm time development has remained an unresolved question in geospace research. This study presents new insight into storm progression in terms of the UT of the storm peak. We present a superposed epoch analysis of solar wind drivers and geomagnetic index responses during magnetic storms, categorized as a function of UT of the storm peak, to investigate the dependency of storm intensity on UT. Storms with Dst minimum less than −100 nT were identified in the 1970–2012 era (305 events), covering four solar cycles. The storms were classified into six groups based on the UT of the minimum Dst (40 to 61 events per bin) then each grouping was superposed on a timeline that aligns the time of the minimum Dst. Fifteen different quantities were considered: seven solar wind parameters and eight activity indices derived from ground‐based magnetometer data. Statistical analyses of the superposed means against each other (between the different UT groupings) were conducted to determine the mathematical significance of similarities and differences in the time series plots. It was found that the solar wind parameters have no significant difference between the UT groupings, as expected. The geomagnetic activity indices, however, all show statistically significant differences with UT during the main phase and/or early recovery phase. Specifically, the 02:00 UT groupings are stronger storms than those in the other UT bins. That is, storms are stronger when the Asian sector is on the nightside (American sector on the dayside) during the main phase.Key PointsWe statistically examine storm time solar wind and geophysical data as a function of UT of the storm peakThere is a significant UT dependence to large storms; larger storms occur with a peak near 02:00 UTThe difference in storm magnitude is caused by substorm activity and not by solar wind drivingPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/134203/1/jgra52755.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/134203/2/jgra52755_am.pd

The CuSPED Mission: CubeSat for GNSS Sounding of the Ionosphere-Plasmasphere Electron Density

The CubeSat for GNSS Sounding of Ionosphere-Plasmasphere Electron Density (CuSPED) is a 3U CubeSat mission concept that has been developed in response to the NASA Heliophysics program's decadal science goal of the determining of the dynamics and coupling of the Earth's magnetosphere, ionosphere, and atmosphere and their response to solar and terrestrial inputs. The mission was formulated through a collaboration between West Virginia University, Georgia Tech, NASA GSFC and NASA JPL, and features a 3U CubeSat that hosts both a miniaturized space capable Global Navigation Satellite System (GNSS) receiver for topside atmospheric sounding, along with a Thermal Electron Capped Hemispherical Spectrometer (TECHS) for the purpose of in situ electron precipitation measurements. These two complimentary measurement techniques will provide data for the purpose of constraining ionosphere-magnetosphere coupling models and will also enable studies of the local plasma environment and spacecraft charging; a phenomenon which is known to lead to significant errors in the measurement of low-energy, charged species from instruments aboard spacecraft traversing the ionosphere. This paper will provide an overview of the concept including its science motivation and implementation