Hydra ? A 3-dimensional electron and ion hot plasma instrument for the POLAR spacecraft of the GGS mission

Scudder, J. D.; Hunsacker, F.; Miller, G.; Lobell, J.; Zawistowski, Tomasz; Ogilvie, K. W.; Keller, John W.; Chornay, D.; Herrero, F. A.; Fitzenreiter, R. J.; Fairfield, D. H.; Needell, J.; Bodet, D.; Googins, J.; Kletzing, C. A.; Torbert, R. B.; Vandiver, James C.; Bentley, R. D.; Fillius, W.; McIlwain, C. E.; Whipple, E. C.; Korth, A.

doi:10.1007/bf00751338

Cited by 184 publications

(150 citation statements)

References 14 publications

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“…We are nevertheless reasonably confident that our calibration is on the whole accurate to within $30% with O + , H + , and He + data included here (obtained before 9 December 1998), provided their signal-to-background ratio is substantially greater than one. It may actually be somewhat better, considering the rather good agreement we have found in flight with positive-ion spectra from the Polar HYDRA instrument (electron and ion hot plasma instrument) [Scudder et al, 1995] when H + ions dominate. We cannot make the same claim with respect to He ++ data, however, at least not in the cusp regions, where intense H + count rates interfere with the H + versus He ++ anode positioning in ways that were not anticipated and therefore not calibrated prior to flight.…”

Section: Margins Of Errormentioning

confidence: 68%

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: 68%

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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“…Again, it consists of multiple bursts of plasma, both ions and electrons (electron data have been obtained from the HYDRA instrument [Scudder et al, 1995] but are not shown here), with flux levels comparable to those of the central plasma sheet, especially the heated flux found during disturbed conditions. It may be noted that the individual bursts, while …”

Section: Ion Observationsmentioning

confidence: 94%

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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“…The Hydra instrument measures the three-dimensional electron and ion velocity-space distribution functions using 12 narrow field-of-view detectors spread over the unit sphere [Scudder et al, 1995]. The distribution functions described here cover the energy range from 5 eV/q to 20 keV/q with a temporal resolution of 13.8 s. Throughout the entire time period from about 0255 to 0708 UT, the Hydra instrument detected dense magnetosheath-like plasma.…”

Section: Overview Of Regions Encountered On May 29 1996mentioning

confidence: 99%

Reconnection at the high‐latitude magnetopause during northward interplanetary magnetic field conditions

Onsager¹,

Scudder²,

Lockwood³

et al. 2001

J. Geophys. Res.

164

207

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Hydra ? A 3-dimensional electron and ion hot plasma instrument for the POLAR spacecraft of the GGS mission

Cited by 184 publications

References 14 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

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

Reconnection at the high‐latitude magnetopause during northward interplanetary magnetic field conditions

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Hydra ? A 3-dimensional electron and ion hot plasma instrument for the POLAR spacecraft of the GGS mission

Cited by 184 publications

References 14 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

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

Reconnection at the high‐latitude magnetopause during northward interplanetary magnetic field conditions

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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