Ionospheric erosion by Alfvén waves

Chaston, C. C.; Génot, Vincent; Bonnell, J. W.; Carlson, C. W.; McFadden, J. P.; Ergun, R. E.; Strangeway, R. J.; Lund, E. J.; Hwang, Kyotaek

doi:10.1029/2005ja011367

Cited by 120 publications

(149 citation statements)

References 62 publications

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“…The nonlinear evolution shows the formation of electron holes structures and associated coherent (small-scale) electrostatic structures observed in auroral cavities by many spacecraft [Génot et al, 2001a[Génot et al, , 2004. More recently a comparative study conducted with FAST data [Chaston et al, 2006] revealed that predictions of the present model were actually observed (electron acceleration on the density gradients, wave focusing in the cavity, ..). On the simulation side, analog results were found independently by Tsiklauri et al [2005].…”

Section: Introductionmentioning

confidence: 90%

Electron acceleration by an Alfvénic pulse propagating in an auroral plasma cavity

Mottez

Génot

2011

J. Geophys. Res.

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[1] With the help of a 2.5-D particle-in-cell simulation code, we investigate the physics of the acceleration of auroral electrons, through the interaction of an isolated Alfvén wave packet with a plasma density cavity. The cavity is edged by density gradients perpendicular to the magnetic field. We show that a single passing of an isolated wave packet over a (infinite) cavity creates an electron beam. It triggers local current and beam-plasma instabilities and small-scale coherent electric structures. The energy flux of downgoing electrons is significantly increased, whereas upgoing electrons are also accelerated, even if no beam is formed. Accelerated electrons remain after the passage of the Alfvénic pulse, allowing the observation of energetic particles without any significant electromagnetic perturbation. The dependence of this process on the electron to ion mass ratio is consistent with its control by inertial effects.Citation: Mottez, F., and V. Génot (2011), Electron acceleration by an Alfvénic pulse propagating in an auroral plasma cavity, J. Geophys. Res., 116,

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Section: Introductionmentioning

confidence: 90%

Electron acceleration by an Alfvénic pulse propagating in an auroral plasma cavity

Mottez

Génot

2011

J. Geophys. Res.

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“…We note however that the level of electron temperature increase that is observed here cannot solely drive this instability. Chaston et al [2006] studied a similar wave spectra to that seen by the SERSIO mission which was associated with perpendicular wave heating. Their analysis of this wave activity may also prove fruitful in the investigation of ion acoustic phenomena that cause NEIAL.…”

Section: Neial and Bbelf Activitymentioning

confidence: 99%

“…Ogawa et al [2003] used DMSP and EISCAT to show that soft precipitation primarily drives ion upflow. Chaston et al [2006] used FAST data to investigate a cold ionospheric density cavity in the dayside auroral oval and found evidence of enhanced electric and magnetic field fluctuations, wave accelerated ions, and field-aligned downward directed electron fluxes. Their analysis of the downward and inward directed Poynting flux in these cavities indicated a cyclical process of Alfvén wave focusing that produces further density depletion and outflow of transversely accelerated ions.…”

Section: Introductionmentioning

confidence: 99%

SERSIO: Svalbard EISCAT Rocket Study of Ion Outflows

et al. 2007

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[1] The SERSIO sounding rocket was launched from Ny-Alesund, Svalbard, into a type 2 ion upflow event simultaneously observed by the European Incoherent Scatter (EISCAT) radar facility in Longyearbyen on 22 January 2004 at 0857 UT. It reached an apogee of 782 km. In situ wave data and thermal particle measurements in the cusp/cleft region clearly show core thermal ion temperature enhancements up to 0.8 eV in association with 0-4 kHz broadband extremely low frequency wave activity (BBELF). The in situ observation of wave heating in the cusp/cleft region at these low altitudes (520-780 km) and high densities (80,000/cm 3 ) is an important measurement and should be included in any model of ion energization. Wave activity in the form of naturally enhanced ion acoustic lines (NEIAL) was seen by the EISCAT radar in the same activity region. Periods of NEIAL were compared with in situ auroral electron data that show no evidence of a bump-on-tail distribution; thus our data do not support using Langmuir turbulence to explain these radar echoes. In contrast, these observations associating NEIAL with BBELF activity suggest that they may be the same phenomenon. During these comparisons, all-sky camera images were used to verify similar environmental conditions between the rocket and radar measurement volumes, while the spatial separation between the volumes was less than 500 km. In situ measurements also confirm the link between soft electron precipitation and thermal electron temperature enhancements in this ion upflow environment.

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“…Various mechanisms have been proposed for such acceleration, including acceleration at the edge of a potential structure [e.g., McFadden et al, 1986;Lotko, 1986] or acceleration due to broadband electrostatic turbulence [e.g., Knudsen et al, 1998]. However, the FAST spacecraft [e.g., Chaston et al, 2000Chaston et al, , 2002aChaston et al, , 2003Chaston et al, , 2006Chaston et al, , 2007 has observed these broadband distributions in conjunction with Alfvénic fluctuations, suggesting that these electrons are accelerated by parallel electric fields in kinetic Alfvén waves. This conclusion was supported by models for the Alfvén wave acceleration of these electrons [e.g., Kletzing, 1994;Thompson and Lysak, 1996;Chaston et al, 1999Chaston et al, , 2000Chaston et al, , 2002aChaston et al, , 2002bKletzing and Hu, 2001;Lysak and Song, 2003a, 2003b, which gave results consistent with observation.…”

Section: Introductionmentioning

confidence: 99%

“…Phase mixing at the plasma sheet boundary layer has been discussed by Allan and Wright [1998] and more recently by Lysak et al [2009]. Such a process could also occur at the edges of the auroral density cavity [e.g., Chaston et al, 2006;Lysak and Song, 2008].…”

Section: Introductionmentioning

confidence: 99%

Development of parallel electric fields at the plasma sheet boundary layer

Lysak

Song

2011

J. Geophys. Res.

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[1] Many measurements of auroral particles, in particular recent measurements from the FAST satellite, indicate that the auroral electron distribution is often broad in energy and field-aligned in pitch angle. Such electrons are seen in conjunction with strong kinetic Alfvén waves with small perpendicular wavelength, and so the aurora produced by these electrons has been termed the "Alfvénic aurora." The Alfvénic aurora is predominant at the polar cap boundary of the aurora as well as in the auroral arc that brightens during substorm onset. The process of forming parallel electric fields in Alfvén waves has been investigated by means of three-dimensional two-fluid simulations. Waves with small perpendicular wavelengths can be produced by phase mixing when perpendicular gradients are present in the plasma. At lower altitudes, Alfvén waves can interact with the ionospheric Alfvén resonator and phase mix to scales of a few kilometers. At higher altitudes, the electron thermal speed becomes comparable or larger than the Alfvén speed, and parallel electric fields due to the Landau resonance can develop. This has been modeled in the fluid code by an approximation to the plasma dispersion function used in kinetic theory. Phase mixing is most effective when there are strong gradients, such as at the plasma sheet boundary layer. Simulations indicate that these processes can produce parallel electric fields on scales of a few kilometers (in the cold plasma case) to a few tens of kilometers (in the warm plasma case), comparable to the scale sizes of auroral arcs.

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Ionospheric erosion by Alfvén waves

Cited by 120 publications

References 62 publications

Electron acceleration by an Alfvénic pulse propagating in an auroral plasma cavity

Electron acceleration by an Alfvénic pulse propagating in an auroral plasma cavity

SERSIO: Svalbard EISCAT Rocket Study of Ion Outflows

Development of parallel electric fields at the plasma sheet boundary layer

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