On the origin of high <i>m</i> magnetospheric waves

Beharrell, M. J.; Kavanagh, A. J.; Honary, F.

doi:10.1029/2009ja014709

Cited by 11 publications

(10 citation statements)

References 34 publications

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“…At electron energies above approximately keV, a plethora of observations exist that link ULF waves in ground magnetometer and riometer absorption (e.g., Anger et al, 1963;Beharrell et al, 2010;Brown, 1964;Heacock & Hunsucker, 1977;Olson et al, 1980;Rae, Mann, Dent, et al, 2007;Roldugin & Roldugin, 2008;Spanswick et al, 2005;Ziauddin, 1960). Spanswick et al (2005) used statistics of NORSTAR riometer measurements to investigate the relationship between Pc5 wave power observed in riometer data and FLRs observed in ground magnetometer data, finding that when significant ULF wave power was observed in riometer absorption, there was always generally a corresponding Pc5 wave signature in ground magnetometer data.…”

Section: Discussionmentioning

confidence: 99%

“…Ultra-low frequency (ULF) waves have been proposed to provide both resonant (e.g., Elkington et al, 1999;Mann et al, 2013) and diffusive (e.g., Brautigam & Albert, 2000;Schulz & Lanzerotti, 1974) acceleration and transport of electrons. ULF wave precipitation signatures have been observed since the early 1960s (e.g., Anger et al, 1963;Brown, 1964;Ziauddin, 1960) and have been observed in riometer (e.g., Beharrell et al, 2010;Heacock & Hunsucker, 1977;Olson et al, 1980;Spanswick et al, 2005), auroral (e.g., Rae, Mann, Dent, et al, 2007;Roldugin & Roldugin, 2008), and X-ray-related precipitation (e.g., Brito et al, 2012;Halford et al, 2015;Motoba et al, 2013). However, although ULF wave signatures have been observed in precipitation across a wide range of energies from keV to MeV, these waves have only been proposed to be indirectly involved in energetic electron losses.…”

Section: Introductionmentioning

confidence: 99%

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The Role of Localized Compressional Ultra‐low Frequency Waves in Energetic Electron Precipitation

et al. 2018

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Typically, ultra‐low frequency (ULF) waves have historically been invoked for radial diffusive transport leading to acceleration and loss of outer radiation belt electrons. At higher frequencies, very low frequency waves are generally thought to provide a mechanism for localized acceleration and loss through precipitation into the ionosphere of radiation belt electrons. In this study we present a new mechanism for electron loss through precipitation into the ionosphere due to a direct modulation of the loss cone via localized compressional ULF waves. We present a case study of compressional wave activity in tandem with riometer and balloon‐borne electron precipitation across keV‐MeV energies to demonstrate that the experimental measurements can be explained by our new enhanced loss cone mechanism. Observational evidence is presented demonstrating that modulation of the equatorial loss cone can occur via localized compressional wave activity, which greatly exceeds the change in pitch angle through conservation of the first and second adiabatic invariants. The precipitation response can be a complex interplay between electron energy, the localization of the waves, the shape of the phase space density profile at low pitch angles, ionospheric decay time scales, and the time dependence of the electron source; we show that two pivotal components not usually considered are localized ULF wave fields and ionospheric decay time scales. We conclude that enhanced precipitation driven by compressional ULF wave modulation of the loss cone is a viable candidate for direct precipitation of radiation belt electrons without any additional requirement for gyroresonant wave‐particle interaction. Additional mechanisms would be complementary and additive in providing means to precipitate electrons from the radiation belts during storm times.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The Role of Localized Compressional Ultra‐low Frequency Waves in Energetic Electron Precipitation

et al. 2018

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“…The higher resolution of ARIES enables detection of much higher m number events, up to 380, some of which are not detectable with other imaging riometers. 29 ARIES has also recorded the first direct measurements of absorption caused by ionospheric modification ("heating") of the D-region by high-power HF radio waves. 30 Due to the high-spatial resolution one of the ARIES beams is able to fit inside the heater beam.…”

Section: Operation and Resultsmentioning

confidence: 99%

Invited Article: Digital beam-forming imaging riometer systems

Honary

Marple

Barratt³

et al. 2011

Review of Scientific Instruments

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The design and operation of a new generation of digital imaging riometer systems developed by Lancaster University are presented. In the heart of the digital imaging riometer is a field-programmable gate array (FPGA), which is used for the digital signal processing and digital beam forming, completely replacing the analog Butler matrices which have been used in previous designs. The reconfigurable nature of the FPGA has been exploited to produce tools for remote system testing and diagnosis which have proven extremely useful for operation in remote locations such as the Arctic and Antarctic. Different FPGA programs enable different instrument configurations, including a 4 × 4 antenna filled array (producing 4 × 4 beams), an 8 × 8 antenna filled array (producing 7 × 7 beams), and a Mills cross system utilizing 63 antennas producing 556 usable beams. The concept of using a Mills cross antenna array for riometry has been successfully demonstrated for the first time. The digital beam forming has been validated by comparing the received signal power from cosmic radio sources with results predicted from the theoretical beam radiation pattern. The performances of four digital imaging riometer systems are compared against each other and a traditional imaging riometer utilizing analog Butler matrices. The comparison shows that digital imaging riometer systems, with independent receivers for each antenna, can obtain much better measurement precision for filled arrays or much higher spatial resolution for the Mills cross configuration when compared to existing imaging riometer systems.

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“…In the dawn-side magnetosphere, the ThE satellite from magnetometer and plasma detector data recorded the azimuthally small-scale oscillations that did not manifest themselves in ground-based magnetic field measurements. Manifestation of the Pi3 pulsations in magnetometer, riometer, and optical observations has also been examined in [Belakhovsky et al, 2015]. The authors observed a sharp increase in energetic particle fluxes from satellite observations, an increase in electron precipitation from riometer absorption data, and an enhancement of auroral intensity from all-sky camera data.…”

Section: Discussionmentioning

confidence: 99%

“…The first, large-scale, was from the external source, whereas the second and third, small-scale, were from the internal sources. Beharrell et al [2010], using scanning riometer data, have studied small-scale oscillations with azimuthal wave numbers up to 380. The authors suggested that the observed small-scale oscillations were secondary, excited by primary oscillations in the magnetospheric cavity, which, in turn, were caused by P d pulses.…”

Section: Penetration Of Mhd Waves From the Solar Wind Into The Magnetmentioning

confidence: 99%

FEATURES OF EXCITATION AND AZIMUTHAL AND MERIDIONAL PROPAGATION OF LONG-PERIOD Pi3 OSCILLATIONS OF THE GEOMAGNETIC FIELD ON DECEMBER 8, 2017

Moiseev

Starodubtsev

Мишин

2020

Solar-Terrestrial Physics

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We study the Pi3 pulsations (with a period T=15–30 min) that were recorded on December 8, 2017 at ground stations in the midnight sector of the magnetosphere at the latitude range of DP2 current system convective electrojets. We have found that Pi3 are especially pronounced in the pre-midnight sector with amplitude of up to 300 nT and duration of up to 2.5 hrs. The pulsation amplitude rapidly decreased with decreasing latitude from F′=72° to F′=63°. The event was recorded during the steady magnetospheric convection. In the southward Bz component of the interplanetary magnetic field, irregular oscillations were detected in the Pi3 frequency range. They correspond to slow magnetosonic waves occurring without noticeable variations in the dynamic pressure Pd. Ground-based geomagnetic observations have shown azimuthal propagation of pulsations with a 0.6–10.6 km/s velocity east and west of the midnight meridian. An analysis of the dynamics of pulsations along the meridian has revealed their propagation to the equator at a velocity 0.75–7.87 km/s. In the projection onto the magnetosphere, the velocities are close in magnitude to the observed propagation velocities of substorm injected electrons. In the dawn-side magnetosphere during ground-observed Pi3 pulsations, compression mode oscillations were recorded. We conclude that propagation of geomagnetic field oscillations in this event depends on the dynamics of particle injections under the action of a large-scale electric field of magnetospheric convection, which causes the plasma to move to Earth due to reconnection in the magnetotail. Small-scale oscillations in the magnetosphere were secondary, excited by the solar wind oscillations penetrating into the magnetosphere.

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On the origin of high m magnetospheric waves

Cited by 11 publications

References 34 publications

The Role of Localized Compressional Ultra‐low Frequency Waves in Energetic Electron Precipitation

The Role of Localized Compressional Ultra‐low Frequency Waves in Energetic Electron Precipitation

Invited Article: Digital beam-forming imaging riometer systems

FEATURES OF EXCITATION AND AZIMUTHAL AND MERIDIONAL PROPAGATION OF LONG-PERIOD Pi3 OSCILLATIONS OF THE GEOMAGNETIC FIELD ON DECEMBER 8, 2017

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