Statistical evidence for O&amp;lt;sup&amp;gt;+&amp;lt;/sup&amp;gt; energization and outflow caused by wave-particle interaction in the high altitude cusp and mantle

Waara, Martin; Slapak, Rikard; Nilsson, Hans; Stenberg, G.; André, Mats; Barghouthi, I. A.

doi:10.5194/angeo-29-945-2011

Cited by 34 publications

(78 citation statements)

References 32 publications

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“…The largest differences from the new ionization (cometary) case are as follows: (a) the massloading regions are geomagnetically connected to the ionosphere through which separated charges can flow, and (b) the mass-loading ions are already heated with non-zero gyrating velocity when they are supplied from one boundary along the magnetic field perpendicular (in the z direction) to the inflow. In Cluster observations at the Earth, these mass-loading ions coming from the ionosphere have thermal velocities of > 100 km s −1 in Nilsson et al (2006) and Waara et al (2011). This value is comparable to the decelerated solar wind speed (about 100 km s −1 in the plasma mantle) as shown in Fig O + stream line in the plasma mantle (as defined in are plotted.…”

Section: Amount Of Converted Kinetic Energy By the Escaping O +supporting

confidence: 49%

Energy conversion through mass loading of escaping ionospheric ions for different Kp values

Yamauchi¹,

Slapak²

2018

Ann. Geophys.

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Abstract. By conserving momentum during the mixing of fast solar wind flow and slow planetary ion flow in an inelastic way, mass loading converts kinetic energy to other forms -e.g. first to electrical energy through charge separation and then to thermal energy (randomness) through gyromotion of the newly born cold ions for the comet and Mars cases. Here, we consider the Earth's exterior cusp and plasma mantle, where the ionospheric origin escaping ions with finite temperatures are loaded into the decelerated solar wind flow. Due to direct connectivity to the ionosphere through the geomagnetic field, a large part of this electrical energy is consumed to maintain field-aligned currents (FACs) toward the ionosphere, in a similar manner as the solar wind-driven ionospheric convection in the open geomagnetic field region. We show that the energy extraction rate by the mass loading of escaping ions ( K) is sufficient to explain the cusp FACs, and that K depends only on the solar wind velocity accessing the mass-loading region (u sw ) and the total mass flux of the escaping ions into this region (m load F load ), as K ∼ −m load F load u 2 sw /4. The expected distribution of the separated charges by this process also predicts the observed flowing directions of the cusp FACs for different interplanetary magnetic field (IMF) orientations if we include the deflection of the solar wind flow directions in the exterior cusp. Using empirical relations of u 0 ∝ Kp+1.2 and F load ∝ exp(0.45Kp) for Kp = 1-7, where u 0 is the solar wind velocity upstream of the bow shock, K becomes a simple function of Kp as log 10 ( K) = 0.2 · Kp + 2 · log 10 (Kp + 1.2) + constant. The major contribution of this nearly linear increase is the F load term, i.e. positive feedback between the increase of ion escaping rate F load through the increased energy consumption in the ionosphere for high Kp, and subsequent extraction of more kinetic energy K from the solar wind to the current system by the increased F load . Since F load significantly increases for increased flux of extreme ultraviolet (EUV) radiation, high EUV flux may significantly enhance this positive feedback. Therefore, the ion escape rate and the energy extraction by mass loading during ancient Earth, when the Sun is believed to have emitted much higher EUV flux than at present, could have been even higher than the currently available highest values based on Kp = 9. This raises a possibility that the ion escape has substantially contributed to the evolution of the Earth's atmosphere.

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Section: Amount Of Converted Kinetic Energy By the Escaping O +supporting

confidence: 49%

Energy conversion through mass loading of escaping ionospheric ions for different Kp values

Yamauchi¹,

Slapak²

2018

Ann. Geophys.

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“…The DC-level (0 Hz) in the data is removed by subtracting the mean of each time window for the EFW. The wave data set is described in more detail by Waara et al (2011). In that study, it was shown that the electric field to magnetic field spectral density ratio (E/B ratio) of the observed waves agreed with the Alfvén wave velocity as calculated from the background magnetic field and ion density estimates obtained using ion spectrometer data.…”

Section: Instrumentation and Datamentioning

confidence: 62%

“…The study of Waara et al (2010) was followed up with a statistical study of the electric and magnetic field spectral densities in the frequency range below 1 Hz, in the general vicinity of the high altitude oxygen gyrofrequency . In Waara et al (2011), it was shown that, statistically, the gyroresonance model could, in fact, reproduce the observed average perpendicular temperature and average parallel velocity for altitudes between 8-15 R E in the cusp/mantle region given the average spectral density. It was assumed that 50 % of the observed wave activity at the local O + gyrofrequency was due to left-hand polarized waves, which can effectively heat the ions.…”

Section: Introductionmentioning

confidence: 99%

“…We use a value of η = 50 % in the calculations in this study. The α value we use is 1.5 and is taken from Waara et al (2011).…”

Section: Waara Et Al: Wave-particle Interaction In High Altitude mentioning

confidence: 99%

“…If heating is continuous, we would get as good correlation between wave activity and temperature for this point-by-point correlation study as we got for the average values. It was however shown in Waara et al (2011) that heating, as observed by the spacecraft, is typically sporadic, lasting only a few minutes for each burst. This could strongly affect the point-by-point correlation between wave activity and ion temperature.…”

Section: Introductionmentioning

confidence: 99%

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Oxygen ion energization by waves in the high altitude cusp and mantle

et al. 2012

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Abstract. We present a comparative study of low frequency electric field spectral densities and temperatures observed by the Cluster spacecraft in the high altitude cusp/mantle region. We compare the relation between the O + temperature and wave intensity at the oxygen gyrofrequency at each measurement point and find a clear correlation. The trend of the correlation agrees with the predictions by both an asymptotic mean-particle theory and a test-particle approach. The perpendicular to parallel temperature ratio is also consistent with the predictions of the asymptotic mean-particle theory. At times the perpendicular temperature is significantly higher than predicted by the models. A simple study of the evolution of the particle distributions (conics) at these altitudes indicates that enhanced perpendicular temperatures would be observed over many R E after heating ceases. Therefore, sporadic intense heating is the likely explanation for cases with high temperature and comparably low wave activity. We observe waves of sufficient amplitude to explain the highest observed temperatures, while the theory in general overestimates the temperature associated with the highest observed wave activity, indicating that such high wave activity is very sporadic.

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Centrifugal acceleration at high altitudes above the polar cap: A Monte Carlo simulation

Abudayyeh¹,

Barghouthi²,

Slapak³

et al. 2015

JGR Space Physics

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A Monte Carlo simulation was used to study the outflow of O+ and H+ ions along three flight trajectories above the polar cap up to altitudes of about 15 RE. Barghouthi (2008) developed a model on the basis of altitude and velocity‐dependent wave‐particle interactions and a radial geomagnetic field which includes the effects of ambipolar electric field and gravitational and mirror forces. In the present work we improve this model to include the effect of the centrifugal force, with the use of relevant boundary conditions. In addition, the magnetic field and flight trajectories, namely, the central polar cap (CPC), nightside polar cap (NPC), and cusp, were calculated using the Tsyganenko T96 model. To simulate wave‐particle interactions, the perpendicular velocity diffusion coefficients for O+ ions in each region were determined such that the simulation results fit the observations. For H+ ions, a constant perpendicular velocity diffusion coefficient was assumed for all altitudes in all regions as recommended by Nilsson et al. (2013). The effect of centrifugal acceleration was simulated by considering three values for the ionospheric electric field: 0 (no centrifugal acceleration), 50, and 100 mV/m. It was found that the centrifugal acceleration increases the parallel bulk velocity and decreases the parallel and perpendicular temperatures of both ion species at altitudes above about 4 RE. Centrifugal acceleration also increases the temperature anisotropy at high altitudes. At a given altitude, centrifugal acceleration decreases the density of H+ ions while it increases the density of O+ ions. This implies that with higher centrifugal acceleration more O+ ions overcome the potential barrier. It was also found that aside from two exceptions centrifugal acceleration has the same effect on the velocities of both ions. This implies that the centrifugal acceleration is universal for all particles. The parallel bulk velocities at a given value of ionospheric electric field were highest in the cusp followed by the CPC followed by the NPC. In this study a region of no wave‐particle interaction was assumed in the CPC and NPC between 3.7 and 7.5 RE. In this region the perpendicular temperature was found to decrease with altitude due to perpendicular adiabatic cooling.

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Statistical evidence for O<sup>+</sup> energization and outflow caused by wave-particle interaction in the high altitude cusp and mantle

Cited by 34 publications

References 32 publications

Energy conversion through mass loading of escaping ionospheric ions for different Kp values

Energy conversion through mass loading of escaping ionospheric ions for different Kp values

Oxygen ion energization by waves in the high altitude cusp and mantle

Centrifugal acceleration at high altitudes above the polar cap: A Monte Carlo simulation

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