Ground and satellite observations of postdawn aurorae near the time of a sudden storm commencement

Journal Article · Tue Feb 01 04:00:00 EST 1994 · Journal of Geophysical Research

DOI:https://doi.org/10.1029/92JA03027· OSTI ID:28481

Egeland, A ^[1]; Burke, W; Maynard, N C ^[2]; Basinska, E M ^[3]; Winningham, J D ^[4]; Deehr, C S ^[5]

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1. Univ. of Oslo (Norway)
2. Phillips Lab., Hanscom Air Force Base, MA (United States)
3. Boston Univ., MA (United States)
4. Southwest Research Institute, San Antonio, TX (United States)
5. Univ. of Alaska, Fairbanks, AK (United States)

Meridian scanning photometer measurements taken in the magnetic postdawn sector at Longyearbyen, Svalbard, between 0300 and 0630 UT on December 29, 1981, are analyzed in conjunction with particle and field data retrieved during two near passes of the Dynamics Explorer 2 (DE 2) satellite. The interval included a sudden storm commencement (SSC) at 0455 UT. Pre-SSC optical and particle measurements showed a system of arcs that are spaced at {approximately} 1.1{degrees} intervals in magnetic latitude, embedded within the region 1 current system and span the convection reversal. The softer particle precipitation appears to have a source near the flanks of the magnetotail while the harder, more equatorward precipitation originates closer to Earth. During the SSC period the entire sky brightened, with enhanced 630.0-nm emissions extending from the northern horizon to south of magnetic zenith; intense but spatially separated 557.7-nm emissions dominated the southern horizon. DE 2 detected more than an order of magnitude increase and near isotropization of ring current electron fluxes, enhanced precipitation from the plasma sheet and significantly decreased auroral zone convection. Region 1/region 2 currents remained, with wavelike structures superposed. A dual timescale response to the SSC is consistent with ground and satellite measurements. On few minute travel timescales for hydromagnetic waves to pass through the system, magnetospheric particles accelerate and precipitate to increase the ionospheric conductivity. Global, field-aligned currents change more slowly. To maintain similar field-aligned currents with higher ionospheric conductances requires reduced electric fields. After 0520 UT the optical emissions settled into stable, but latitudinally separated, bands of 630.0- and 557.7-nm emissions characteristic of cleft and plasma sheet precipitation, respectively. 55 refs., 10 figs.

• OSTI ID: 28481
• Journal Information: Journal of Geophysical Research, Journal Name: Journal of Geophysical Research Journal Issue: A2 Vol. 99; ISSN JGREA2; ISSN 0148-0227
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
AURORAE
CHARGED-PARTICLE PRECIPITATION
MAGNETIC STORMS
MAGNETOTAIL
PHOTON EMISSION
PLASMA SHEET
REMOTE SENSING
TIME DEPENDENCE