Anisotropic fluid modeling of ionospheric upflow: Effects of low‐altitude anisotropy and thermospheric winds

Burleigh, M.; Zettergren, M. D.

doi:10.1002/2016ja023329

Cited by 7 publications

(18 citation statements)

References 65 publications

(126 reference statements)

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“…The ionospheric model used in this study and described in detail in Burleigh and Zettergren () (GEMINI‐TIA) is an anisotropic extension of the model originally developed in Zettergren and Semeter () and expanded in Zettergren and Snively (), Zettergren et al (), and Zettergren and Snively (). This fluid model solves the 2‐D nonlinear equations for the conservation of mass, momentum, parallel energy, and perpendicular energy for each species s relevant to the E and F regions and topside ionosphere ( s = O + , NO + , N

_{2}^{+}

_{2}^{+}

, N + , and H + ) and is coupled to a quasi‐static treatment of auroral and neutral dynamo electric currents.…”

Section: Modeling Approachmentioning

confidence: 99%

“…In a third new simulation, denoted by SS W , the control simulation also has wave heating applied at the same UT for additional comparison. The wave heating is accomplished through the use of the resonant heating term,

{\overset{W}{true}}_{s, ⊥}

, included in the perpendicular energy equation within the model that encompasses the acceleration of ions by transverse plasma waves (Burleigh & Zettergren, ). This gyroresonant (cyclotron) energy transfer is the most efficient in regions of low ion‐neutral collision rates and is therefore not very effective below 500 km except in extreme cases (e.g., Whalen et al, ).…”

Section: Ionospheric Response To Gw Forcingmentioning

confidence: 99%

“…This gyroresonant (cyclotron) energy transfer is the most efficient in regions of low ion‐neutral collision rates and is therefore not very effective below 500 km except in extreme cases (e.g., Whalen et al, ). The present form of the model (Burleigh & Zettergren, ) uses an empirical specification of this heating term:

{\overset{W}{true}}_{s, ⊥} false(ω false) = 2 m_{s} n_{s} ((), \frac{η q_{s}^{2}}{4 m_{s}^{2}}) false| E_{o} |^{2} {((), \frac{ω}{ω_{o}})}^{- α}

where ω is the local gyrofrequency for each ion, η is the fraction of the wavefield which is left‐hand polarized, assumed to be 0.125 (Chang et al, ), α is the spectral power index, assumed to be 1.7 (Crew et al, ), and | E o | 2 is the wave power spectral density set here to be 0.3 (mV/m) 2 /Hz with the reference frequency ω o assumed to be 6.5 Hz (Retterer et al, ; Zeng & Horwitz, ; Zeng et al, ). This type of heating occurs primarily in collisionless regions; the resulting ion distributions remain highly anisotropic and are accelerated by the mirror force, attaining large field‐aligned velocities high above the heating region.…”

Section: Ionospheric Response To Gw Forcingmentioning

confidence: 99%

“…This gyroresonant (cyclotron) energy transfer is the most efficient in regions of low ion-neutral collision rates and is therefore not very effective below 500 km except in extreme cases (e.g., Whalen et al, 1978). The present form of the model (Burleigh & Zettergren, 2017) uses an empirical specification of this heating term: Figure 10. The gravity wave-driven topside transport is enough to alter the ion populations available for secondary acceleration processes, such as transverse wave heating, that can lead to outflow into the magnetosphere.…”

Section: Ionospheric Response To Gw Forcingmentioning

confidence: 99%

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Modulation of Low‐Altitude Ionospheric Upflow by Linear and Nonlinear Atmospheric Gravity Waves

et al. 2018

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This study examines how thermospheric motions due to gravity waves (GWs) drive ion upflow in the F region, modulating the topside ionosphere in a way that can contribute to ion outflow. We present incoherent scatter radar data from Sondrestrom, from 31 May 2003 which showed upflow/downflow motions, having a downward phase progression, in the field‐aligned velocity, indicating forcing by a thermospheric GW. The GW‐upflow coupling dynamics are investigated through the use of a coupled atmosphere‐ionosphere model to examine potential impacts on topside ionospheric upflow. Specifically, a sequence of simulations with varying wave amplitude is conducted to determine responses to a range of transient forcing reminiscent of the incoherent scatter radar data. Nonlinear wave effects, resulting from increases in amplitude of the modeled GW, are shown to critically impact the ionospheric response. GW breaking deposits energy into smaller scale wave modes, drives periods of large field‐aligned ion velocities, while also modulating ion densities. Complementary momentum transfer increases the mean flow and, through ion‐neutral drag, can increase ion densities above 300 km. Ionospheric collision frequency (cooling) and photoionization effects (heating), both dependent on ionospheric density, modify the electron temperature; these changes conduct quickly up geomagnetic field lines driving ion upflow at altitudes well above initial disturbances. This flow alters ion populations available for high‐altitude acceleration processes that may lead to outflow into the magnetosphere. We have included a representative source of transverse wave heating which, when supplemented by our GWs, illustrates strengthened upward fluxes in the topside ionosphere.

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_{2}^{+}

_{2}^{+}

, N + , and H + ) and is coupled to a quasi‐static treatment of auroral and neutral dynamo electric currents.…”

Section: Modeling Approachmentioning

confidence: 99%

{\overset{W}{true}}_{s, ⊥}

Section: Ionospheric Response To Gw Forcingmentioning

confidence: 99%

{\overset{W}{true}}_{s, ⊥} false(ω false) = 2 m_{s} n_{s} ((), \frac{η q_{s}^{2}}{4 m_{s}^{2}}) false| E_{o} |^{2} {((), \frac{ω}{ω_{o}})}^{- α}

Section: Ionospheric Response To Gw Forcingmentioning

confidence: 99%

Section: Ionospheric Response To Gw Forcingmentioning

confidence: 99%

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Modulation of Low‐Altitude Ionospheric Upflow by Linear and Nonlinear Atmospheric Gravity Waves

et al. 2018

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“…Previous ionospheric modeling studies (e.g., Burleigh & Zettergren, ; Wu et al, ) and comparisons against observations (e.g., Sanchez & Strømme, ) have demonstrated that ionospheric sources of plasma to the topside (controlled by low‐altitude heating and dynamics) can regulate outward ion fluxes. Most upflow studies examine the “step response” of the ionosphere, by using a fixed precipitation input having some “ramp‐up“ time scale or “on‐off” paradigm (e.g., Caton et al, ; Sadler et al, ) — a sensible approach but one that cannot account for situations with complicated time‐variable forcing.…”

Section: Introductionmentioning

confidence: 99%

Transient Ionospheric Upflow Driven by Poleward Moving Auroral forms Observed During the Rocket Experiment for Neutral Upwelling 2 (RENU2) Campaign

Burleigh

Zettergren

Lynch

et al. 2019

Geophysical Research Letters

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This study examines cumulative effects of a series of poleward moving auroral forms on ion upflow and downflow. These effects are investigated using an ionospheric model with inputs derived from the Rocket Experiment for Neutral Upwelling 2 (RENU2) sounding rocket campaign. Auroral precipitation inputs are constrained by all‐sky imager brightness values resulting in significant latitudinal structuring in simulated ionospheric upflows due to transient forcing. For contrast, a case with steady forcing generates almost double the O+ upflow transport through 1,000 km when compared to poleward moving auroral form‐like structures. At high altitudes, model results show a spread in upflow response time dependent on ion mass, with molecular ions responding slower than atomic ions by several minutes. While the modeled auroral precipitation is not strong enough to accelerate ions to escape velocities, source populations available for higher‐altitude energization processes are greatly impacted by variable forcing exhibited by the RENU2 event.

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Low‐Altitude Ion Heating, Downflowing Ions, and BBELF Waves in the Return Current Region

et al. 2018

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Heavy (O+) ion energization and field‐aligned motion in and near the ionosphere are still not well understood. Based on observations from the CAScade, Smallsat and IOnospheric Polar Explorer (CASSIOPE) Enhanced Polar Outflow Probe at altitudes between 325 km and 730 km over 1 year, we present a statistical study (24 events) of ion heating and its relation to field‐aligned ion bulk flow velocity, low‐frequency waves, and field‐aligned currents. The ion temperature and field‐aligned bulk flow velocity are derived from 2‐D ion velocity distribution functions measured by the suprathermal electron imager (SEI) instrument. Consistent ion heating and flow velocity characteristics are observed from both the SEI and the rapid‐scanning ion mass spectrometer instruments. We find that transverse O+ ion heating in the ionosphere can be intense (up to 4.5 eV), confined to very narrow regions (∼2 km across B), is more likely to occur in the downward current region and is associated with broadband extremely low frequency (BBELF) waves. These waves are interpreted as linearly polarized perpendicular to the magnetic field. The amount of ion heating cannot be explained by frictional heating, and the correlation of ion heating with BBELF waves suggests that significant wave‐ion heating is occurring and even dominating at altitudes as low as 350 km, a boundary that is lower than previously reported. Surprisingly, the majority of these heating events (17 out 24) are associated with core ion downflows rather than upflows. This may be explained by a downward pointing electric field in the low‐altitude return current region.

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Anisotropic fluid modeling of ionospheric upflow: Effects of low‐altitude anisotropy and thermospheric winds

Cited by 7 publications

References 65 publications

Modulation of Low‐Altitude Ionospheric Upflow by Linear and Nonlinear Atmospheric Gravity Waves

Modulation of Low‐Altitude Ionospheric Upflow by Linear and Nonlinear Atmospheric Gravity Waves

Transient Ionospheric Upflow Driven by Poleward Moving Auroral forms Observed During the Rocket Experiment for Neutral Upwelling 2 (RENU2) Campaign

Low‐Altitude Ion Heating, Downflowing Ions, and BBELF Waves in the Return Current Region

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