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T. J. Immel, H. U. Frey, S. B. Mende, S. Fuselier, J.C. Gerard, B. Hubert.

Subauroral proton precipitation observed by IMAGE FUV. T. J. Immel, H. U. Frey, S. B. Mende, S. Fuselier, J.C. Gerard, B. Hubert. Space Sciences Laboratory, University of California, Berkeley.

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T. J. Immel, H. U. Frey, S. B. Mende, S. Fuselier, J.C. Gerard, B. Hubert.

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  1. Subauroral proton precipitation observed by IMAGE FUV T. J. Immel, H. U. Frey, S. B. Mende, S. Fuselier, J.C. Gerard, B. Hubert. Space Sciences Laboratory, University of California, Berkeley

  2. During some periods of geomagnetic activity, aurora-like features can be observed well away from the auroral oval on the dayside. • Questions: • What are they and why do they occur? • Is there a common driver or phenomenon behind all of them? • Are they observed in other instruments from space? (e.g. EUV, HENA, MENA)

  3. Impulsive Event, Oct 28 (Day 302), 2000 Extended Event, Jan 23, 2001

  4. Observations- Location and mapping of precipitation. 1) All of the continuous precipitation effects are observed in the noon-dusk sector. Using the Tseganenko magnetospheric field model to project these features into the equatorial plane, they are seen at distances greater than 6 Re. 2) The day 23, 2001 event occurs over Canada, while the day 118, 2001 event occurs over northeastern Russia. The others are in not-so-handy locations for ground based comparisons.

  5. Observations - Energy • For day 23, the subauroral precipitation is made up entirely of protons. The same is probably the case for day 193 (2000) and day 118 (2001). • Knowing this, one can determine the proton energy with comparisons to WIC. • Without this knowledge (e.g. day 302-impulsive), one can still use WIC to provide the upper limit of proton energy.

  6. More Observations - Energy • From IMAGE, the proton energies in the dusk-sector subauroral forms (at the particular locations studied in detail) are ~20-30 keV. • This is somewhat less than what FAST shows in a single conjugate pass through this region. • From IMAGE, the proton energies in the dawn-sector impulsive event (day 302) are < 8 keV (upper-limit constraint provided by WIC-S12 comparison).

  7. Solar wind parameters, Days 193 (2000) and 23 (2001)

  8. ACE data for day 118, 2001 event and impulsive dawn side precipitation.

  9. Observations – Solar Wind • The continuous precipitation in the dusk sector does not seem to be controlled by the solar wind IMF or modulated by the solar wind density, though high solar wind density/pressure at the magnetopause is observed in all cases. • The single impulsive event is obviously related to the arrival of a shock (and the subsequent brightening of the entire auroral oval).

  10. Conclusions • Continuous subauroral precipitation in the dusk sector can occur after the arrival of shocks in the solar wind, or significant enhancements in solar wind density. • From the three cases studied here, there is no obvious IMF control. The process which governs the precipitation is probably an internal process of the magnetosphere. • Impulsive precipitation (in this case occurring in the dawn sector) is related directly to the arrival of shock fronts at the magnetopause. We should find more of these if we look!

  11. More work! • Full characterization of the proton energy vs. time and vs. location. • Search for more cases at shock arrival times, and periods of high solar wind dynamic pressure. Does the local time of the proton precipitation change? • LANL satellites and HENA data are just now being investigated. We must keep looking for FAST conjunctions.

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