Bibliography

Spatial structures in solar wind superthermal electrons and polar rain aurora

We report a special polar rain aurora case around 11:24 UT on October 27, 2003, where intense polar rain electrons produced observable polar rain auroral emission with the shape of a roughly dawn-dusk aligned bar. Associated solar wind speed and density observations during the event were around 450 km/s and 2.5 cm−3 respectively. The interplanetary magnetic field (IMF) components Bx, By, and Bz were \textasciitilde5, −3, and 5 nT respectively. The negative By condition likely caused the dawnside shift and slight tilt of the polar rain aurora bar. Furthermore, although Kelvin-Helmholtz waves on the high latitude magnetopause have been previously reported to induce dawn-dusk aligned auroral bars (Zhang et al., 2007), the solar wind and IMF conditions of the event are not favorable for generating them (Zhang et al., 2013) and are therefore not a likely cause. Instead, coincident observations by the Geotail satellite show enhanced anti-sunward flux in the solar wind superthermal electrons (7 eV–42 keV) around the time of the auroral bar. The solar wind superthermal electron spatial size, when mapped into the polar ionosphere, is consistent with the width of the auroral bar, confirming a connection between the two.

Herschbach, Dennis; Zhang, Yongliang;

Published by: Journal of Atmospheric and Solar-Terrestrial Physics      Published on: jul

YEAR: 2021     DOI: 10.1016/j.jastp.2021.105633

Magnetosphere interaction; Polar rain aurora; Polar rain electrons; solar wind; Solar wind superthermal electrons

Exploring the Upper Atmosphere

In this chapter, we describe how we can understand the state of the upper atmosphere (the ionosphere, thermosphere, and aurora) using optical observations and how one produces a global view of the Earth s upper atmosphere from optical remote sensing, especially using far ultraviolet (FUV) wavelengths, to advance our understanding of the near Earth space environment. We examine the choice of optical signatures, the basic science behind the signatures, and the techniques for observations. Examples of the technique as applied to key geophysical processes are described and discussed for tracing the physical processes that alter the state variables (in particular, density, composition, and temperature) in the upper atmosphere. Applications of optical remote sensing will be discussed in terms of the challenges inherent in establishing a predictive capability of the global upper atmosphere system, including the high-latitude regions (such as the Arctic) where the structures of the thermosphere and ionosphere are complicated by strong coupling among the polar ionosphere, magnetosphere, and solar wind.

Paxton, Larry; Zhang, Yongliang; Kil, Hyosub; Schaefer, Robert;

Published by:       Published on:

YEAR: 2021     DOI: 10.1002/9781119815631.ch23

Earth space environment; far ultraviolet wavelengths; high-latitude regions; optical remote sensing; solar wind; upper atmosphere

Ionosphere-thermosphere (IT) response to solar wind forcing during magnetic storms

During magnetic storms, there is a strong response in the ionosphere and thermosphere which occurs at polar latitudes. Energy input in the form of Poynting flux and energetic particle precipitation, and energy output in the form of heated ions and neutrals have been detected at different altitudes and all local times. We have analyzed a number of storms, using satellite data from the Defense Meteorological Satellite Program (DMSP), the Gravity Recovery and Climate Experiment (GRACE), Gravity field and steady-state Ocean Circulation Explorer (GOCE), and Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) mission. Poynting flux measured by instruments on four DMSP spacecraft during storms which occurred in 2011\textendash2012 was observed in both hemispheres to peak at both auroral and polar latitudes. By contrast, the measured ion temperatures at DMSP and maxima in neutral density at GOCE and GRACE altitudes maximize in the polar region most frequently with little evidence of Joule heating at auroral latitudes at these spacecraft orbital locations.

Huang, Cheryl; Huang, Yanshi; Su, Yi-Jiun; Sutton, Eric; Hairston, Marc; Coley, William;

Published by: Journal of Space Weather and Space Climate      Published on: 01/2016

YEAR: 2016     DOI: 10.1051/swsc/2015041

Energy distribution; Ionosphere; polar cap; solar wind; thermosphere

Polar cap arcs correlated with solar wind entry at the high latitude magnetosphere

Polar cap arcs are sun-aligned aurora structures occurring during northward turnings of the Interplanetary Magnetic Field (IMF) B_z component. At the same time, a new region of solar wind entry at the high latitude magnetosphere, tailward of the cusp region, was found recently at the periods of northward IMF B_z. We propose a study to see the relationship of these entry events with the transpolar arc formation. Data of Global Ultraviolet Imager (GUVI) onboard TIMED mission is examined to see the transpolar aurora arcs during the given time periods of the solar wind entry. Initial results show that in approximately 20\% of cases transpolar arcs occur related to the solar wind entry processes.

Mailyan, B.; Shi, Q.; Gou, X.;

Published by:       Published on:

YEAR: 2014     DOI: 10.1109/URSIGASS.2014.6929926

aurora interplanetary; GUVI; magnetic fields; magnetosphere; solar wind; TIMED

Comparison of penetration electric fields created by the solar wind with Jicamarca data using SWAGE

SWAGE (Solar Wind Acting on the Geophysical Environment) calculates the global ionospheric electric field generated by high-latitude electrodynamics drivers determined from the time-shifted solar wind data measured at L1 by joining the Hill-Siscoe polar cap potential model with the N-C ionospheric potential solver. Of particular interest are the conditions under which the eastward equatorial penetration electric field near twilight contributes to the pre-reversal enhancement (PRE). In the present model, it is found that a steeper terminator conductance gradient leads to a more pronounced PRE. The model is statistically consistent with the Jicamarca vertical drift data at twilight during quiet times for eighty-two days in the years 1998\textendash2005. The model is also consistent with the Jicamarca vertical drift data during the November 2004 magnetic superstorms (Dst\ \< -250 nT) and highlights the importance of including the LT dependence of the ionospheric response. In this comparison, disturbance dynamo (DD) effects are also included. Comparison is much better using the conductance model with a shallower terminator gradient and indicates that the conductance LT profile was relatively unchanged throughout the storms.

Rothwell, P.; Jasperse, J.; Grossbard, N.;

Published by: Journal of Geophysical Research      Published on: 09/2012

YEAR: 2012     DOI: 10.1029/2012JA017684

Electric field; Ionosphere; solar wind

Comparison of the Hill–Siscoe polar cap potential theory with the Weimer and AMIE models

The magnetic storm on November 2004 was characterized by a high solar wind pressure and thus offers a unique opportunity to test the Hill–Siscoe formula (H–S) for the polar cap potential (PCP). To estimate the polar cap potential, we use the Weimer Statistical Convection Model (WCM), and the Assimilative Mapping of Ionospheric Electrodynamics Model (AMIE), based on ingestion of a number of data sets. H–S is in excellent agreement with WCM, and with AMIE during times when DMSP is used in the latter. The implication is that the AMIE conductivity model yields conductivities that are too high by a factor of 2–3. Both H–S and WCM display saturation effects, although WCM is more severe. The two methods track well until an IEF of about 20mV/m occurs, where H–S continues to increase while WCM levels off. Even at high electric field values, the pressure increases the denominator of the H–S formula by 60\%, keeping the potential lower than its saturation value. There are several H–S points above 250kV, even up to 400kV, that are not found in WCM and occur right after a rapid transition from Bz north to south. For Bz north, we find evidence for a saturation effect on the PCP at large IEF, little effect as a function of solar wind velocity, and an increase of the PCP with increasing pressure. This seems to rule out viscous interaction but may involve geometric changes in the high-altitude polar cusp that affect recombination there for Bz north.

Kelley, Michael; Crowley, Geoffrey; Weimer, Daniel;

Published by: Journal of Atmospheric and Solar-Terrestrial Physics      Published on:

YEAR: 2010     DOI: https://doi.org/10.1016/j.jastp.2009.02.011

Magnetic storm; Polar cap potential; Hill–Siscoe formula; solar wind