Incoherent Scatter Radar Estimation of F Region Ionospheric Composition During Frictional Heating Events

A method is developed for estimating F region ion composition from incoherent scatter radar (ISR) measurements during times of frictional ion heating. The technique addresses ion temperature‐mass ambiguities in the IS spectra by self‐consistently modeling ion temperature profiles, including the effects of ion temperature anisotropies and altitude‐independent neutral winds. The modeled temperature profiles are used in a minimization procedure to estimate ion composition consistent with the recorded IS spectra. The proposed method is applicable to short‐integration (min) data sets from either single‐beam or multiple‐beam experiments. Application of the technique to Sondrestrom ISR measurements shows increases in F region molecular ions in response to frictional heating, a result consistent with previous theoretical and observational work. Estimates of ion composition are shown to be relatively insensitive to moderate variations in the neutral atmospheric model, which serves as input to the method. The technique developed in this work is uniquely qualified for studying highly variable ion composition near auroral arcs and associated processes such as molecular ion upflows. It also addresses a systematic source of error in standard ISR analysis methods when they are applied in such situations

Imaging radar observations of Farley Buneman waves during the JOULE II experiment

Vector electric fields and associated <I><B>E</B></I>×<I><B>B</B></I> drifts measured by a sounding rocket in the auroral zone during the NASA JOULE II experiment in January 2007, are compared with coherent scatter spectra measured by a 30 MHz radar imager in a common volume. Radar imaging permits precise collocation of the spectra with the background electric field. The Doppler shifts and spectral widths appear to be governed by the cosine and sine of the convection flow angle, respectively, and also proportional to the presumptive ion acoustic speed. The neutral wind also contributes to the Doppler shifts. These findings are consistent with those from the JOULE I experiment and also with recent numerical simulations of Farley Buneman waves and instabilities carried out by Oppenheim et al. (2008). Simple linear analysis of the waves offers some insights into the spectral moments. A formula relating the spectral width to the flow angle, ion acoustic speed, and other ionospheric parameters is derived

Identification of substorm onset location and preonset sequence using Reimei, THEMIS GBO, PFISR, and Geotail

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95307/1/jgra20667.pd

Observations of Ionospheric Heating During the Passage of Solar Coronal Hole Fast Streams

Using ionospheric temperature measurements made continuously by the Poker Flat Incoherent Scatter Radar (PFISR) and EISCAT Svalbard Radar (ESR) during the International Polar Year (IPY), we provide evidence for directly driven ionospheric heating associated with the solar wind corotating interaction region (CIR). Both ESR and PFISR operated almost continuously during the IPY, which began on 1 March 2007. During this period 55 CIR events occurred and when ISR observations were available during these events ionospheric heating was observed. This study is the first comprehensive observation of ionospheric heating by CIRs demonstrated through case study comparisons and statistically over the 1-year IPY period. These multiple-day heating events are present in both the auroral and polar regions. The quantitative one-to-one correlation between ACE-CIR observations and ISR-ionosphere observations leads to a database that will enable the ionospheric heating efficiency of CIR events to be determined

Substorm triggering by new plasma intrusion: Incoherent‐scatter radar observations

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95031/1/jgra20482.pd

Can forest management based on natural disturbances maintain ecological resilience?

Given the increasingly global stresses on forests, many ecologists argue that managers must maintain ecological resilience: the capacity of ecosystems to absorb disturbances without undergoing fundamental change. In this review we ask: Can the emerging paradigm of natural-disturbance-based management (NDBM) maintain ecological resilience in managed forests? Applying resilience theory requires careful articulation of the ecosystem state under consideration, the disturbances and stresses that affect the persistence of possible alternative states, and the spatial and temporal scales of management relevance. Implementing NDBM while maintaining resilience means recognizing that (i) biodiversity is important for long-term ecosystem persistence, (ii) natural disturbances play a critical role as a generator of structural and compositional heterogeneity at multiple scales, and (iii) traditional management tends to produce forests more homogeneous than those disturbed naturally and increases the likelihood of unexpected catastrophic change by constraining variation of key environmental processes. NDBM may maintain resilience if silvicultural strategies retain the structures and processes that perpetuate desired states while reducing those that enhance resilience of undesirable states. Such strategies require an understanding of harvesting impacts on slow ecosystem processes, such as seed-bank or nutrient dynamics, which in the long term can lead to ecological surprises by altering the forest's capacity to reorganize after disturbance