Multi-scale features of solar terrestrial coupling in the cusp ionosphere

Moen, J.; Carlson, H. C.; Rinne, Y.; Skjæveland, Åsmund

doi:10.1016/j.jastp.2011.07.002

Cited by 14 publications

(14 citation statements)

References 75 publications

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“…The magnetic curvature force drives high‐speed horizontal plasma flow jets in the ionosphere after reconnection [ Valladares et al ., ]. Current sheets of upgoing or precipitating electrons bound the edges of this driven flow channel [ Southwood , ; Moen et al ., ]. That CHAMP sees density/drag enhancements collocated with fine current sheets was one of the pieces of supporting evidence cited by Carlson et al .…”

Section: Introductionmentioning

confidence: 79%

“…The magnetic curvature force drives high-speed horizontal plasma flow jets in the ionosphere after reconnection [Valladares et al, 1998]. Current sheets of upgoing or precipitating electrons bound the edges of this driven flow channel [Southwood, 1987;Moen et al, 2012]. That CHAMP sees density/drag enhancements collocated with fine current sheets was one of the pieces of supporting evidence cited by Carlson et al [2012] for their explanation of the density doublings as due to energy deposition associated with magnetic reconnection events (which also have accompanying fine current sheets).…”

Section: Statistical Work Bymentioning

confidence: 99%

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Which cusp upflow events can possibly turn into outflows?

2014

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Two sequences, before and after magnetic noon, respectively, of poleward moving auroral forms with associated upflows situated above the European Incoherent Scatter Svalbard Radar allowed close study of ion upflow dynamics. We find that flux intensity is correlated with plasma temperature and that upflowing plasma undergoes acceleration proportional to the slope of the velocity profile and to the velocity at each altitude. The potential for upflows to lift thermal plasma to regions where broadband extremely low frequency electric field activity can cause nonthermal acceleration leading to outflow is examined. Equations for estimating the travel time of upflowing plasma are presented. We find that around 40% of the observed upflow profiles with a unit number flux greater than 1 × 10 13 m À2 s À1 can transport plasma from 500 to 800 km altitude in less than 10 min, approximately the typical lifetime of pulsed upflow events. Almost all such profiles can transport plasma from 600 to 800 km in the same time span. Typical transport times for other altitude ranges are also presented. Post magnetic noon the background electron density was somewhat higher than prenoon due to transport of EUV-enhanced plasma, and the postnoon ion flux was somewhat weaker than prenoon.

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Section: Introductionmentioning

confidence: 79%

Section: Statistical Work Bymentioning

confidence: 99%

Which cusp upflow events can possibly turn into outflows?

2014

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“…[12] The primary energy deposited into the near-Earth environment by magnetic reconnection events at the magnetopause is dissipation of downgoing Poynting flux into the ionosphere-thermosphere where, by ion frictional drag heating (or equivalently Joule heating as per Thayer and Semeter [2004, Appendix A]), the Poynting flux that is not reflected is nearly all passed into the ultimate heat sink, the thermosphere [Carlson, 2012;Carlson et al, 2012]. Strong plasma flow shears have been known to be common in the cusp for a considerable time [e.g., Pinnock et al, 1993Pinnock et al, , 1995Oksavik et al, 2004aOksavik et al, , 2004bOksavik et al, , 2005Rinne et al, 2007Rinne et al, , 2010Rinne et al, , 2011Moen et al, 2008Moen et al, , 2012aMoen et al, , 2012b. Energy is also deposited by the background cusp particle precipitation, as well as transient injection of electrons and ions precipitating from the newly opened magnetic flux tubes.…”

Section: Relevance Of Magnetic Reconnection Eventsmentioning

confidence: 99%

“…The poleward boundaries of contours of sharp gradients in Ne, Te, Ti, and 630.0 nm intensity track poleward with these relative time delays, and sharp plasma flow shear boundaries separate background plasma from plasma entrained in these flow shears. The edges of these flow shears are found to seed velocity shear or Kelvin-Helmholtz instabilities , which can also lead to plasma density irregularities and strong radar echoes at decameter HF wavelengths [Moen et al, 2001[Moen et al, , 2012a[Moen et al, , 2012bOksavik et al, 2005Oksavik et al, , 2011Oksavik et al, , 2012.…”

Section: Relevance Of Magnetic Reconnection Eventsmentioning

confidence: 99%

Thermally excited 630.0 nm O(¹D) emission in the cusp: A frequent high‐altitude transient signature

2013

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[1] We highlight why 630.0 nm auroral emissions excited by thermal electrons are expected to be significant in the cusp and are occurring more often than generally recognized. We note conditions when they are likely to occur and provide a simple formula to calculate the altitude discriminated (R/km) and line-of-sight integrated 630.0 nm intensity (kR). The formula is applied to incoherent scatter radar data near the cusp to produce 2-D maps of thermal red line aurora. We estimate when the thermally excited red aurora should be negligible or not, for given electron density (Ne), electron temperature (Te), and exospheric temperature (Tn) conditions. Sensitivity to Te dominates that to Tn and Ne. We test these formulas against radar and all-sky imaging photometer data for 2 days. The time/ space agreement, as transient strong red arcs pass over the cusp, confirms detection of a thermal 630.0 nm aurora in~400-450 km altitude, twice the height (4 times the area) conventionally assumed for 630.0 nm emissions. Among many potential uses for this technique is application to the long-standing question of the degree to which magnetic reconnection events contribute to the net magnetic flux entering the polar cap. We conclude that it is more often than now recognized and provide a tool and guidelines to facilitate improvement over present underestimates.

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“…While research on localized flow enhancements deep in the polar cap is very limited, narrow and transient flow enhancements near the dayside auroral poleward boundary have been widely identified. Around the dayside cusp, flow channels drifting poleward into the polar cap are detected as signatures of magnetopause reconnection or flux transfer events (FTEs) [ Moen et al ., , and references therein] and they are closely associated with dayside auroral intensifications and subsequent poleward moving auroral forms (PMAFs) [e.g., Lockwood et al ., ; Sandholt and Farrugia , ]. The poleward motion of these localized flows and PMAFs is attributed to magnetic flux being eroded from closed field lines and transported to the polar cap.…”

Section: Introductionmentioning

confidence: 99%

Localized polar cap flow enhancement tracing using airglow patches: Statistical properties, IMF dependence, and contribution to polar cap convection

et al. 2015

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Recent radar observations have suggested that polar cap flows are highly structured and that localized flow enhancements can lead to nightside auroral disturbances. However, knowledge of these flows is limited to available echo regions. Utilizing wide spatial coverage by an all-sky imager at Resolute Bay and simultaneous Super Dual Auroral Radar Network measurements, we statistically determined properties of such flows and their interplanetary magnetic field (IMF) dependence. We found that narrow flow enhancements are well collocated with airglow patches with substantially larger velocities (≥200 m/s) than the weak large-scale background flows. The flow azimuthal widths are similar to the patch widths. During the evolution across the polar cap, the flow directions and speeds are consistent with the patch propagation directions and speeds. These correspondences indicate that patches can optically trace localized flow enhancements reflecting the flow width, speed, and direction. Such associations were found common (~67%) in statistics, and the typical flow speed, propagation time, and width within our observation areas are 600 m/s, tens of minutes, and 200-300 km, respectively. By examining IMF dependence of the occurrence and properties of these flows, we found that they tend to be observed under B y -dominated IMF. Flow speeds are large under oscillating IMF clock angles. Localized flow enhancements are usually observed as a channel elongated in the noon-midnight meridian and directed toward premidnight (postmidnight) for +B y (ÀB y ). The potential drops across localized flow enhancements account for~10-40% of the cross polar cap potential, indicating that they significantly contribute to polar cap plasma transport.

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Multi-scale features of solar terrestrial coupling in the cusp ionosphere

Cited by 14 publications

References 75 publications

Which cusp upflow events can possibly turn into outflows?

Which cusp upflow events can possibly turn into outflows?

Thermally excited 630.0 nm O(¹D) emission in the cusp: A frequent high‐altitude transient signature

Localized polar cap flow enhancement tracing using airglow patches: Statistical properties, IMF dependence, and contribution to polar cap convection

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Multi-scale features of solar terrestrial coupling in the cusp ionosphere

Cited by 14 publications

References 75 publications

Which cusp upflow events can possibly turn into outflows?

Which cusp upflow events can possibly turn into outflows?

Thermally excited 630.0 nm O(1D) emission in the cusp: A frequent high‐altitude transient signature

Localized polar cap flow enhancement tracing using airglow patches: Statistical properties, IMF dependence, and contribution to polar cap convection

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Thermally excited 630.0 nm O(¹D) emission in the cusp: A frequent high‐altitude transient signature