Observations of Paired Electrostatic Shocks in the Polar Magnetosphere

Mozer, F. S.; Carlson, C. W.; Hudson, M. K.; Torbert, R. B.; Parady, Bodo; Yatteau, J.; Kelley, M. C.

doi:10.1103/physrevlett.38.292

Cited by 696 publications

(396 citation statements)

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“…That would change, quite significantly, the multiplier used for entering the corresponding flow density sampling in the average hemispheric outflow rate. However, electric fields that strong are localized [e.g., Mozer et al, 1977], and the E Â B drift tends to average out across an entire polar region. As a consequence, drift-related arithmetic errors are, in fact, already part of the scatter we found by using different grids for averaging.…”

Section: Margins Of Errormentioning

confidence: 99%

Solar wind control of Earth's H⁺ and O⁺ outflow rates in the 15‐eV to 33‐keV energy range

2004

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[1] Earth's high-latitude outflow of H + and O + ions has been examined with the Toroidal Imaging Mass-Angle Spectrograph instrument on the Polar satellite in the 15-eV to 33-keV energy range over an almost 3-year period near solar minimum (1996)(1997)(1998). This outflow is compared with solar wind plasma and interplanetary magnetic field (IMF) data from the Wind spacecraft, the latter having been time shifted to the subsolar magnetopause and averaged for 15 min prior to each sampling of Earth's magnetic fieldaligned ion flow densities. When the flow data are arranged according to the polarity of the IMF B z (in GSM coordinates) and limited to times with B z > 3 nT or B z < À3 nT, the total rate of ion outflow is seen to be significantly enhanced with negative B z , typically by factors of 2.5-3 for the O + and 1.5-2 for the H + , more than previously reported from similar but less extensive comparisons. With either IMF B z polarity the rate of ion outflow is well correlated with the solar wind energy flow density, especially well with the density of kinetic energy flow. The rate of ion outflow within the instrument's energy range is a strong function of the Polar satellite altitude, increasing almost threefold from perigee (R $ 2 R E ) toward apogee (R $ 4-9 R E ) for O + ions, i.e., up to 10 26 ions s À1 or more per hemisphere. The apogee enhancement may be still larger for the H + , but it is obscured by mantle flow of cusp origin solar H + . Ion mean energy also increases with altitude, leading to about a twentyfold increase in the O + energy flow rate from Polar perigee to apogee altitude, reaching values of 20 GW or more per hemisphere. While the perigee outflow of H + has little or no seasonal modulation, in terms of ions s À1 the O + outflow rates at both altitudes do increase during local summer and so does the rate of cusp origin H + flow near apogee. The latter rate, in fact, has very similar seasonal modulation as the O + rates, suggesting that it has a significant influence on the O + outflow.

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Section: Margins Of Errormentioning

confidence: 99%

Solar wind control of Earth's H⁺ and O⁺ outflow rates in the 15‐eV to 33‐keV energy range

2004

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“…Acceleration from magnetic field-aligned potential drops is known to occur at several 1000 km altitudes above auroral arcs (e.g., Mozer et al 1977;Sharp, Johnson, & Shelley 1977;Gorney et al 1981). It is thus the closest realization of a powerful cosmic acceleration process, easy to probe, and, indeed, documented by a wealth of data (a good collection of papers with data from the Swedish Viking satellite can be found in the May issue [no.…”

Section: Introductionmentioning

confidence: 99%

Acceleration from Field-Aligned Potential Drops

Haerendel

1994

International Astronomical Union Colloquium

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Unstable field-aligned currents are seen as the origin of field-aligned potential drops. They convert energy stored in magnetic shear stresses into kinetic energy. A good fraction of this energy is carried by runaway electrons and ions out of the acceleration region. The paper emphasizes the analogy with mechanical fractures. Simple expressions for the energy conversion rate and the parallel potential drop are derived, the two being linked by the critical current density needed for instability. The origin of the currents (generator) lies mostly in a region remote from that of energy conversion (fracture zone). The transmission of shear stresses and energy from the generator plasma, where the primary forces are applied to the fracture zone is also considered. A closed set of relations allows quantitative evaluation of the energetic particle production efficiency. The decoupling of the plasma on either side of the fracture zone which allows fast stress relief is described in detail, as well as a stationary model for the Alfven wave interaction between fracture zone and generator plasma. A simple concept of the nature of the anomalous resistivity generated by the unstable current leads to an expression for the magnetic diffusivity inside the fracture zone and an estimate of the latter's extent parallel to the magnetic field, whereas its width and length transverse to B follow from the macroscopic relations. Finally and as an example, the theory is applied to the problem of fast electron (and ion) acceleration well above 1 MeV seen to occur in many solar flares. It is obvious that this process belongs to the most powerful production processes of high-energy particles in stellar magnetic fields.

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“…This is at most about 10 times larger than the local gyroradius of a 1 keV proton at 90°pitch angle, for example, and less than three times the gyroradius of a 1 keV O + ion. If these scale sizes were to reflect the spatial structure of high-altitude transverse electric fields, which appears to be the case [e.g., Mozer et al, 1977], then one would anticipate that finite gyroradii effects play an important role in the transverse acceleration of upflowing terrestrial ions. As will be illustrated below, terrestrial-origin ions are indeed transversely accelerated to keV energies at altitudes as high as R = 6 R E (and higher).…”

Section: Introductionmentioning

confidence: 99%

In situ Polar observation of transverse cold‐ion acceleration: Evidence that electric field generation is a hot‐ion finite gyroradii effect

Lennartsson

2003

J. Geophys. Res.

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[1] Recent results with the Polar TIMAS instrument (ion mass spectrometer) have revealed that earthward magnetic field-aligned and velocity-dispersed flows of 1-to 33-keV protons (and other ions) from the outer magnetosphere are inherently ''blast-like'' and exhibit a complex filamentary structure where transverse scale sizes may often be a few proton gyroradii. These velocity-dispersed protons (and accompanying hot electrons) have been found to have a close association with enhanced large pitch angle outflow of accelerated (sometimes to more than 10 keV) ionospheric ions (H + , O + , and He + ) at Polar. Theoretical considerations suggest a mechanism by which the difference in gyroradii between hot ions and electrons in earthward plasma bursts generates charge imbalance and strong transverse electric fields at density gradients, as the bursts move into an increasingly strong magnetic field, which in turn accelerate the ambient cold ions. Model electric fields greater than 1 V m À1 at Polar are readily generated with density gradient scale lengths of a few earth radii in an equatorial source region of the bursts, assuming that the magnetic moments of the burst protons are preserved. The nonadiabatic acceleration of cold ions may act to reduce these fields to the ca 0.1-V m À1 amplitude and few-second period fluctuations actually observed. Sample TIMAS data are shown to be consistent with the transverse acceleration of cold O + ions to keV energy on a timescale of less than a single gyroperiod.

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Observations of Paired Electrostatic Shocks in the Polar Magnetosphere

Abstract: fields, static randomness, etc. Thus, it is expected to become an important theoretical tool for studying many-body systems, especially narrow-band materials 8 (e.g.,NiS) and impurity bands in crystalline semiconductors. 9

Cited by 696 publications

References 7 publications

Solar wind control of Earth's H⁺ and O⁺ outflow rates in the 15‐eV to 33‐keV energy range

Solar wind control of Earth's H⁺ and O⁺ outflow rates in the 15‐eV to 33‐keV energy range

Acceleration from Field-Aligned Potential Drops

In situ Polar observation of transverse cold‐ion acceleration: Evidence that electric field generation is a hot‐ion finite gyroradii effect

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Observations of Paired Electrostatic Shocks in the Polar Magnetosphere

Abstract: fields, static randomness, etc. Thus, it is expected to become an important theoretical tool for studying many-body systems, especially narrow-band materials 8 (e.g.,NiS) and impurity bands in crystalline semiconductors. 9

Cited by 696 publications

References 7 publications

Solar wind control of Earth's H+ and O+ outflow rates in the 15‐eV to 33‐keV energy range

Solar wind control of Earth's H+ and O+ outflow rates in the 15‐eV to 33‐keV energy range

Acceleration from Field-Aligned Potential Drops

In situ Polar observation of transverse cold‐ion acceleration: Evidence that electric field generation is a hot‐ion finite gyroradii effect

Contact Info

Product

Resources

About

Solar wind control of Earth's H⁺ and O⁺ outflow rates in the 15‐eV to 33‐keV energy range

Solar wind control of Earth's H⁺ and O⁺ outflow rates in the 15‐eV to 33‐keV energy range